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Versions: 00
NFS Version 4 Working Group S. Shepler
INTERNET-DRAFT Sun Microsystems
Document: draft-ietf-nfsv4-03-00.txt C. Beame
Hummingbird Communications
B. Callaghan
Sun Microsystems
M. Eisler
Sun Microsystems
D. Noveck
Network Appliance
D. Robinson
Sun Microsystems
R. Thurlow
Sun Microsystems
December 1999
NFS version 4 Protocol
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
NFS version 4 is a distributed file system protocol which owes
heritage to NFS versions 2 [RFC1094] and 3 [RFC1813]. Unlike earlier
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versions, NFS version 4 supports traditional file access while
integrating support for file locking and the mount protocol. In
addition, support for strong security (and its negotiation), compound
operations, and internationalization have been added. Of course,
attention has been applied to making NFS version 4 operate well in an
Internet environment.
Copyright
Copyright (C) The Internet Society (1999). All Rights Reserved.
Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7
1.1. Overview of NFS Version 4 Features . . . . . . . . . . . . 7
1.1.1. RPC and Security . . . . . . . . . . . . . . . . . . . . 8
1.1.2. Procedure and Operation Structure . . . . . . . . . . . 8
1.1.3. File System Model . . . . . . . . . . . . . . . . . . . 9
1.1.3.1. Filehandle Types . . . . . . . . . . . . . . . . . . . 9
1.1.3.2. Attribute Types . . . . . . . . . . . . . . . . . . 10
1.1.3.3. File System Replication and Migration . . . . . . . 10
1.1.4. OPEN and CLOSE . . . . . . . . . . . . . . . . . . . . 11
1.1.5. File locking . . . . . . . . . . . . . . . . . . . . . 11
1.1.6. Client Caching and Delegation . . . . . . . . . . . . 11
2. Protocol Data Types . . . . . . . . . . . . . . . . . . . 13
2.1. Basic Data Types . . . . . . . . . . . . . . . . . . . . 13
2.2. Structured Data Types . . . . . . . . . . . . . . . . . 14
3. RPC and Security Flavor . . . . . . . . . . . . . . . . . 18
3.1. Ports and Transports . . . . . . . . . . . . . . . . . . 18
3.2. Security Flavors . . . . . . . . . . . . . . . . . . . . 18
3.2.1. Security mechanisms for NFS version 4 . . . . . . . . 18
3.2.1.1. Kerberos V5 as security triple . . . . . . . . . . . 19
3.2.1.2. LIPKEY as a security triple . . . . . . . . . . . . 19
3.2.1.3. SPKM-3 as a security triple . . . . . . . . . . . . 20
3.3. Security Negotiation . . . . . . . . . . . . . . . . . . 21
3.3.1. Security Error . . . . . . . . . . . . . . . . . . . . 21
3.3.2. SECINFO . . . . . . . . . . . . . . . . . . . . . . . 21
4. Filehandles . . . . . . . . . . . . . . . . . . . . . . . 22
4.1. Obtaining the First Filehandle . . . . . . . . . . . . . 22
4.1.1. Root Filehandle . . . . . . . . . . . . . . . . . . . 22
4.1.2. Public Filehandle . . . . . . . . . . . . . . . . . . 23
4.2. Filehandle Types . . . . . . . . . . . . . . . . . . . . 23
4.2.1. General Properties of a Filehandle . . . . . . . . . . 24
4.2.2. Persistent Filehandle . . . . . . . . . . . . . . . . 24
4.2.3. Volatile Filehandle . . . . . . . . . . . . . . . . . 25
4.2.4. One Method of Constructing a Volatile Filehandle . . . 26
4.3. Client Recovery from Filehandle Expiration . . . . . . . 26
5. File Attributes . . . . . . . . . . . . . . . . . . . . . 28
5.1. Mandatory Attributes . . . . . . . . . . . . . . . . . . 29
5.2. Recommended Attributes . . . . . . . . . . . . . . . . . 29
5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . 29
5.4. Mandatory Attributes - Definitions . . . . . . . . . . . 31
5.5. Recommended Attributes - Definitions . . . . . . . . . . 34
5.6. Interpreting owner and owner_group . . . . . . . . . . . 39
5.7. Quota Attributes . . . . . . . . . . . . . . . . . . . . 40
5.8. Access Control Lists . . . . . . . . . . . . . . . . . . 41
5.8.1. ACE type . . . . . . . . . . . . . . . . . . . . . . . 42
5.8.2. ACE flag . . . . . . . . . . . . . . . . . . . . . . . 42
5.8.3. ACE Access Mask . . . . . . . . . . . . . . . . . . . 43
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5.8.4. ACE who . . . . . . . . . . . . . . . . . . . . . . . 44
6. File System Migration and Replication . . . . . . . . . . 46
6.1. Replication . . . . . . . . . . . . . . . . . . . . . . 46
6.2. Migration . . . . . . . . . . . . . . . . . . . . . . . 46
6.3. Interpretation of the fs_locations Attribute . . . . . . 47
6.4. Filehandle Recovery for Migration or Replication . . . . 48
7. NFS Server Namespace . . . . . . . . . . . . . . . . . . . 49
7.1. Server Exports . . . . . . . . . . . . . . . . . . . . . 49
7.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . 49
7.3. Server Pseudo File System . . . . . . . . . . . . . . . 50
7.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . 50
7.5. Filehandle Volatility . . . . . . . . . . . . . . . . . 50
7.6. Exported Root . . . . . . . . . . . . . . . . . . . . . 51
7.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . 51
7.8. Security Policy and Namespace Presentation . . . . . . . 51
8. File Locking . . . . . . . . . . . . . . . . . . . . . . . 53
8.1. Definitions . . . . . . . . . . . . . . . . . . . . . . 53
8.2. Locking . . . . . . . . . . . . . . . . . . . . . . . . 54
8.2.1. Client ID . . . . . . . . . . . . . . . . . . . . . . 54
8.2.2. nfs_lockowner and stateid Definition . . . . . . . . . 56
8.2.3. Use of the stateid . . . . . . . . . . . . . . . . . . 58
8.2.4. Sequencing of Lock Requests . . . . . . . . . . . . . 58
8.3. Blocking Locks . . . . . . . . . . . . . . . . . . . . . 59
8.4. Lease Renewal . . . . . . . . . . . . . . . . . . . . . 59
8.5. Crash Recovery . . . . . . . . . . . . . . . . . . . . . 60
8.5.1. Client Failure and Recovery . . . . . . . . . . . . . 60
8.5.2. Server Failure and Recovery . . . . . . . . . . . . . 61
8.5.3. Network Partitions and Recovery . . . . . . . . . . . 63
8.6. Server Revocation of Locks . . . . . . . . . . . . . . . 64
8.7. Share Reservations . . . . . . . . . . . . . . . . . . . 65
8.8. OPEN/CLOSE Operations . . . . . . . . . . . . . . . . . 65
8.9. Short and Long Leases . . . . . . . . . . . . . . . . . 66
8.10. Clocks and Calculating Lease Expiration . . . . . . . . 66
9. Client-Side Caching . . . . . . . . . . . . . . . . . . . 68
9.1. Performance Challenges for Client-Side Caching . . . . . 68
9.2. Delegation and Callbacks . . . . . . . . . . . . . . . . 69
9.2.1. Delegation Recovery . . . . . . . . . . . . . . . . . 71
9.3. Data Caching . . . . . . . . . . . . . . . . . . . . . . 72
9.3.1. Data Caching and OPENs . . . . . . . . . . . . . . . . 73
9.3.2. Data Caching and File Locking . . . . . . . . . . . . 73
9.3.3. Data Caching and Mandatory File Locking . . . . . . . 75
9.3.4. Data Caching and File Identity . . . . . . . . . . . . 75
9.4. Open Delegation . . . . . . . . . . . . . . . . . . . . 77
9.4.1. Open Delegation and Data Caching . . . . . . . . . . . 79
9.4.2. Open Delegation and File Locks . . . . . . . . . . . . 80
9.4.3. Recall of Open Delegation . . . . . . . . . . . . . . 80
9.4.4. Delegation Revocation . . . . . . . . . . . . . . . . 82
9.5. Data Caching and Revocation . . . . . . . . . . . . . . 83
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9.5.1. Revocation Recovery for Write Open Delegation . . . . 83
9.6. Attribute Caching . . . . . . . . . . . . . . . . . . . 84
9.7. Name Caching . . . . . . . . . . . . . . . . . . . . . . 85
9.8. Directory Caching . . . . . . . . . . . . . . . . . . . 86
10. Minor Versioning . . . . . . . . . . . . . . . . . . . . 88
11. Internationalization . . . . . . . . . . . . . . . . . . 91
11.1. Universal Versus Local Character Sets . . . . . . . . . 91
11.2. Overview of Universal Character Set Standards . . . . . 92
11.3. Difficulties with UCS-4, UCS-2, Unicode . . . . . . . . 93
11.4. UTF-8 and its solutions . . . . . . . . . . . . . . . . 94
12. Error Definitions . . . . . . . . . . . . . . . . . . . . 95
13. NFS Version 4 Requests . . . . . . . . . . . . . . . . . 100
13.1. Compound Procedure . . . . . . . . . . . . . . . . . . 100
13.2. Evaluation of a Compound Request . . . . . . . . . . . 101
13.3. Operation Values . . . . . . . . . . . . . . . . . . . 101
14. NFS Version 4 Procedures . . . . . . . . . . . . . . . . 102
14.1. Procedure 0: NULL - No Operation . . . . . . . . . . . 102
14.2. Procedure 1: COMPOUND - Compound Operations . . . . . . 103
14.2.1. Operation 3: ACCESS - Check Access Rights . . . . . . 106
14.2.2. Operation 4: CLOSE - Close File . . . . . . . . . . . 109
14.2.3. Operation 5: COMMIT - Commit Cached Data . . . . . . 111
14.2.4. Operation 6: CREATE - Create a Non-Regular File Object 114
14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting
Recovery . . . . . . . . . . . . . . . . . . . . . . 116
14.2.6. Operation 8: DELEGRETURN - Return Delegation . . . . 117
14.2.7. Operation 9: GETATTR - Get Attributes . . . . . . . . 118
14.2.8. Operation 10: GETFH - Get Current Filehandle . . . . 120
14.2.9. Operation 11: LINK - Create Link to a File . . . . . 122
14.2.10. Operation 12: LOCK - Create Lock . . . . . . . . . . 124
14.2.11. Operation 13: LOCKT - Test For Lock . . . . . . . . 126
14.2.12. Operation 14: LOCKU - Unlock File . . . . . . . . . 128
14.2.13. Operation 15: LOOKUP - Lookup Filename . . . . . . . 130
14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory . . 133
14.2.15. Operation 17: NVERIFY - Verify Difference in
Attributes . . . . . . . . . . . . . . . . . . . . . 135
14.2.16. Operation 18: OPEN - Open a Regular File . . . . . . 137
14.2.17. Operation 19: OPENATTR - Open Named Attribute
Directory . . . . . . . . . . . . . . . . . . . . . 145
14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open . . . . . 147
14.2.19. Operation 21: PUTFH - Set Current Filehandle . . . . 149
14.2.20. Operation 22: PUTPUBFH - Set Public Filehandle . . . 150
14.2.21. Operation 23: PUTROOTFH - Set Root Filehandle . . . 151
14.2.22. Operation 24: READ - Read from File . . . . . . . . 152
14.2.23. Operation 25: READDIR - Read Directory . . . . . . . 154
14.2.24. Operation 26: READLINK - Read Symbolic Link . . . . 158
14.2.25. Operation 27: REMOVE - Remove Filesystem Object . . 160
14.2.26. Operation 28: RENAME - Rename Directory Entry . . . 162
14.2.27. Operation 29: RENEW - Renew a Lease . . . . . . . . 165
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14.2.28. Operation 30: RESTOREFH - Restore Saved Filehandle . 167
14.2.29. Operation 31: SAVEFH - Save Current Filehandle . . . 169
14.2.30. Operation 32: SECINFO - Obtain Available Security . 170
14.2.31. Operation 33: SETATTR - Set Attributes . . . . . . . 172
14.2.32. Operation 34: SETCLIENTID - Negotiate Clientid . . . 174
14.2.33. Operation 35: SETCLIENTID_CONFIRM - Confirm Clientid 176
14.2.34. Operation 36: VERIFY - Verify Same Attributes . . . 178
14.2.35. Operation 37: WRITE - Write to File . . . . . . . . 180
15. NFS Version 4 Callback Procedures . . . . . . . . . . . . 185
15.1. Procedure 0: CB_NULL - No Operation . . . . . . . . . . 185
15.2. Procedure 1: CB_COMPOUND - Compound Operations . . . . 186
15.2.1. Operation 3: CB_GETATTR - Get Attributes . . . . . . 188
15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation . 190
16. Security Considerations . . . . . . . . . . . . . . . . . 191
17. RPC definition file . . . . . . . . . . . . . . . . . . . 192
18. Bibliography . . . . . . . . . . . . . . . . . . . . . . 223
19. Authors and Contributors . . . . . . . . . . . . . . . . 228
19.1. Editor's Address . . . . . . . . . . . . . . . . . . . 228
19.2. Authors' Addresses . . . . . . . . . . . . . . . . . . 228
20. Full Copyright Statement . . . . . . . . . . . . . . . . 230
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1. Introduction
The NFS version 4 protocol is a further revision of the NFS protocol
defined already by versions 2 [RFC1094] and 3 [RFC1813]. It retains
the essential characteristics of previous versions: design for easy
recovery, independent of transport protocols, operating systems and
filesystems, simplicity, and good performance. The NFS version 4
revision has the following goals:
o Improved access and good performance on the Internet.
The protocol is designed to transit firewalls easily, perform
well where latency is high and bandwidth is low, and scale to
very large numbers of clients per server.
o Strong security with negotiation built into the protocol.
The protocol builds on the work of the ONCRPC working group in
supporting the RPCSEC_GSS protocol. Additionally, the NFS
version 4 protocol provides a mechanism to allow clients and
servers the ability to negotiate security and require clients
and servers to support a minimal set of security schemes.
o Good cross-platform interoperability.
The protocol features a file system model that provides a
useful, common set of features that does not unduly favor one
file system or operating system over another.
o Designed for protocol extensions.
The protocol is designed to accept standard extensions that do
not compromise backward compatibility.
1.1. Overview of NFS Version 4 Features
To provide a reasonable context for the reader, the major features of
NFS version 4 protocol will be reviewed in brief. This will be done
to provide an appropriate context for both the reader who is familiar
with the previous versions of the NFS protocol and the reader that is
new to the NFS protocols. For the reader new to the NFS protocols,
there is still a fundamental knowledge that is expected. The reader
should be familiar with the XDR and RPC protocols as described in
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[RFC1831] and [RFC1832]. A basic knowledge of file systems and
distributed file systems is expected as well.
1.1.1. RPC and Security
As with previous versions of NFS, the External Data Representation
(XDR) and Remote Procedure Call (RPC) mechanisms used for the NFS
version 4 protocol are those defined in [RFC1831] and [RFC1832]. To
meet end to end security requirements, the RPCSEC_GSS framework
[RFC2623] will be used to extend the basic RPC security. With the
use of RPCSEC_GSS, various mechanisms can be provided to offer
authentication, integrity, and privacy to the NFS version 4 protocol.
Kerberos V5 will be used as described in [RFC1964] to provide one
security framework. The LIPKEY GSS-API mechanism described in
[RFCXXXX] will be used to deliver the use of password and server
public key to the NFS version 4 protocol. With the use of
RPCSEC_GSS, other mechanisms may also be specified and used for NFS
version 4 security.
To enable in-band security negotiation, the NFS version 4 protocol
has added a new operation which provides the client a method of
querying the server about its policies regarding which security
mechanisms must be used for access to the server's file system
resources. With this, the client can securely match the security
mechanism that meets the policies specified at both the client and
server.
1.1.2. Procedure and Operation Structure
A significant departure from the previous versions of the NFS
protocol is the introduction of the COMPOUND procedure. For the NFS
version 4 protocol, there are two RPC procedures, NULL and COMPOUND.
The COMPOUND procedure is defined in terms of operations and these
operations correspond more closely to the traditional NFS procedures.
With the use of the COMPOUND procedure, the client is able to build
simple or complex requests. These COMPOUND requests allow for a
reduction in the number of RPCs needed for logical file system
operations. For example, without previous contact with a server a
client will be able to read data from a file in one request by
combining LOOKUP, OPEN, and READ operations in a single COMPOUND RPC.
With previous versions of the NFS protocol, this type of single
request was not possible.
The model used for COMPOUND is very simple. There is no logical OR
or ANDing of operations. The operations combined within a COMPOUND
request are evaluated in order by the server. Once an operation
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returns a failing result, the evaluation ends and the results of all
evaluated operations are returned to the client.
The NFS version 4 protocol has held onto the model of having the
client refer to a file or directory at the server by a "filehandle".
The COMPOUND procedure has a method of passing a filehandle from one
operation to another within the sequence of operations. There is a
concept of a "current filehandle" and "saved filehandle". Most
operations use the "current filehandle" as the file system object to
operate upon. The "saved filehandle" is used as temporary filehandle
storage within a COMPOUND procedure.
1.1.3. File System Model
The general file system model used for the NFS version 4 protocol is
the same as previous versions. The server file system is
hierarchical with the regular files contained within being treated as
opaque byte streams. In a slight departure, file and directory names
are encoded with UTF-8 to deal with the basics of
internationalization.
The NFS version 4 protocol does not require a separate protocol to
provide for the initial mapping between path name and filehandle.
Instead of using the older MOUNT protocol for this mapping, the
server provides a ROOT filehandle that represents the logical root or
top of the file system tree provided by the server. The server
provides multiple file systems by glueing them together with pseudo
file systems. These pseudo file systems provide for potential gaps
in the path names between real file systems.
1.1.3.1. Filehandle Types
In previous versions of the NFS protocol, the filehandle provided by
the server was guaranteed to be valid or persistent for the lifetime
of the file system object to which it referred. For some server
implementations, this persistence requirement has been difficult to
meet. For the NFS version 4 protocol, this requirement has been
relaxed by introducing another type of filehandle, volatile. With
persistent and volatile filehandle types, the server implementation
can match the abilities of the file system at the server along with
the operating environment. The client will have knowledge of the
type of filehandle being provided by the server and can be prepared
to deal with the semantics of each.
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1.1.3.2. Attribute Types
The NFS version 4 protocol introduces three classes of file system or
file attributes. Like the additional filehandle type, the
classification of file attributes has been done to ease server
implementations along with extending the overall functionality of the
NFS protocol. This attribute model is structured to be extensible
such that new attributes can be introduced in minor revisions of the
protocol without requiring significant rework.
The three classifications are: mandatory, recommended and named
attributes. This is a significant departure from the previous
attribute model used in the NFS protocol. Previously, the attributes
for the file system and file objects were a fixed set of mainly Unix
attributes. If the server or client did not support a particular
attribute, it would have to simulate the attribute the best it could.
Mandatory attributes are the minimal set of file or file system
attributes that must be provided by the server and must be properly
represented by the server. Recommended attributes represent
different file system types and operating environments. The
recommended attributes will allow for better interoperability and the
inclusion of more operating environments. The mandatory and
recommended attribute sets are traditional file or file system
attributes. The third type of attribute is the named attribute. A
named attribute is an opaque byte stream that is associated with a
directory or file and referred to by a string name. Named attributes
are meant to be used by client applications as a method to associate
application specific data with a regular file or directory.
One significant addition to the recommended set of file attributes is
the Access Control List (ACL) attribute. This attribute provides for
directory and file access control beyond the model used in previous
versions of the NFS protocol. The ACL definition allows for
specification of user and group level access control.
1.1.3.3. File System Replication and Migration
With the use of a special file attribute, the ability to migrate or
replicate server file systems is enabled within the protocol. The
file system locations attribute provides a method for the client to
probe the server about the location of a file system. In the event
of a migration of a file system, the client will receive and error
when operating on the file system and it can then query as to the new
file system location. Similar steps are used for replication, the
client is able to query the server for the multiple available
locations of a particular file system. From this information, the
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client can use its own policies to access the appropriate file system
location.
1.1.4. OPEN and CLOSE
The NFS version 4 protocol introduces OPEN and CLOSE operations. The
OPEN operation provides a single point where file lookup, creation,
and share semantics can be combined. The CLOSE operation also
provides for the release of state accumulated by OPEN.
1.1.5. File locking
With the NFS version 4 protocol, the support for byte range file
locking is part of the NFS protocol. The file locking support is
structured so that an RPC callback mechanism is not required. This
is a departure from the previous versions of the NFS file locking
protocol -- NLM. The state associated with file locks is maintained
at the server under a lease based model. The server defines a single
lease period for all state held by a NFS client. If the client does
not renew its lease within the defined period, all state associated
with the client's lease may be released by the server. The client
may renew its lease with use of the RENEW operation or implicitly by
use of other operations (primarily READ).
1.1.6. Client Caching and Delegation
The file, attribute, and directory caching for the NFS version 4
protocol is similar to previous versions. Attributes and directory
information are cached for a duration determined by the client. At
the end of a predefined timeout, the client will query the server to
see if the related file system object has been updated.
For file data, the client checks its cache validity when the file is
open. A query is sent to the server to determine if the file has
been changed. Based on this information, the client determines if
the data cache for the file should kept or release. Also, when the
file is closed, any modified data is written to the server.
If an application wants to serialize access to file data, file
locking of the file data ranges in question should be used.
The major addition to NFS version 4 in the area of caching is the
ability of the server to delegate certain responsibilities to the
client. When the server grants a delegation for a file to a client,
the client is guaranteed certain semantics with respect to the
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sharing of that file with other clients. At OPEN, the client may ask
the server for either a read or write delegation for the file. If
the client is granted a read delegation, it is assured that no other
client has the ability to write to the file for the duration of the
delegation. If the client is granted a write delegation, the client
is assured that no other client has read or write access to the file.
Delegations can be recalled by the server. If another client
requests access to the file in such a way that the access conflicts
with the granted delegation, the server is able to notify the initial
client and recall the delegation. This requires that a callback path
exist between the server and client. If this callback path does not
exist, then delegations can not be granted. The essence of a
delegation is that it allows the client to locally service operations
such as OPEN, CLOSE, LOCK, LOCKU, READ, WRITE without immediate
interaction with the server.
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2. Protocol Data Types
The syntax and semantics to describe the data types of the NFS
version 4 protocol are defined in the XDR [RFC1832] and RPC [RFC1831]
documents. The next sections build upon the XDR data types to define
types and structures specific to this protocol.
2.1. Basic Data Types
Data Type Definition
_____________________________________________________________________
int32_t typedef int int32_t;
uint32_t typedef unsigned int uint32_t;
int64_t typedef hyper int64_t;
uint64_t typedef unsigned hyper uint64_t;
attrlist4 typedef opaque attrlist4<>;
Used for file/directory attributes
bitmap4 typedef uint32_t bitmap4<>;
Used in attribute array encoding.
clientid4 typedef uint64_t clientid4;
Shorthand reference to client identification
component4 typedef utf8string component4;
Represents path name components
cookieverf4 typedef opaque cookieverf4[8];
Used for READDIR to verify cookie values
count4 typedef uint32_t count4;
Various count parameters (READ, WRITE, COMMIT)
createverf4 typedef opaque createverf4[8];
Used for exclusive CREATE
length4 typedef uint64_t length4;
Describes LOCK lengths
linktext4 typedef utf8string linktext4;
Symbolic link contents
mode4 typedef uint32_t mode4;
Mode attribute data type
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nfs_cookie4 typedef uint64_t nfs_cookie4;
Opaque cookie value for READDIR
nfs_fh4 typedef opaque nfs_fh4<NFS4_FHSIZE>;
Filehandle definition; NFS4_FHSIZE is defined as 128
nfs_ftype4 enum nfs_ftype4;
Various defined file types
nfsstat4 enum nfsstat4;
Return value for operations
offset4 typedef uint64_t offset4;
Various offset designations (READ, WRITE, LOCK, COMMIT)
pathname4 typedef component4 pathname4<>;
Represents path name for LOOKUP, OPEN and others
qop4 typedef uint32_t qop4;
Quality of protection designation in SECINFO
sec_oid4 typedef opaque sec_oid4<>;
Security Object Identifier
seqid4 typedef uint32_t seqid4;
Sequence identifier used for file locking
stateid4 typedef uint64_t stateid4;
State identifier used for file locking and delegation
utf8string typedef opaque utf8string<>;
UTF-8 encoding for strings
writeverf4 typedef uint32_t writeverf4;
Write verifier used for WRITE and COMMIT
2.2. Structured Data Types
nfstime4
struct nfstime4 {
int64_t seconds;
uint32_t nseconds;
}
The nfstime4 structure gives the number of seconds and
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nanoseconds since midnight or 0 hour January 1, 1970 Coordinated
Universal Time (UTC). Values greater than zero for the seconds
field denote dates after the 0 hour January 1, 1970. Values
less than zero for the seconds field denote dates before the 0
hour January 1, 1970. In both cases, the nseconds field is to
be added to the seconds field for the final time representation.
For example, if the time to be represented is one-half second
before 0 hour January 1, 1970, the seconds field would have a
value of negative one (-1) and the nseconds fields would have a
value of one-half second (500000000). Values greater than
999,999,999 for nseconds are considered invalid.
This data type is used to pass time and date information. A
server converts to and from local time when processing time
values, preserving as much accuracy as possible. If the
precision of timestamps stored for a file system object is less
than defined, loss of precision can occur. An adjunct time
maintenance protocol is recommended to reduce client and server
time skew.
specdata4
struct specdata4 {
uint32_t specdata1;
uint32_t specdata2;
}
This data type represents additional information for the device
file types NF4CHR and NF4BLK.
fsid4
struct fsid4 {
uint64_t major;
uint64_t minor;
};
This type is the file system identifier that is used as a
mandatory attribute.
fs_location4
struct fs_location4 {
utf8string server<>;
pathname4 rootpath;
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};
fs_locations4
struct fs_locations4 {
pathname4 fs_root;
fs_location4 locations<>;
};
The fs_location4 and fs_locations4 data types are used for the
fs_locations recommended attribute which is used for migration
and replication support.
fattr4
struct fattr4 {
bitmap4 attrmask;
attrlist4 attr_vals;
};
The fattr4 structure is used to represent file and directory
attributes.
The bitmap is a counted array of 32 bit integers used to contain
bit values. The position of the integer in the array that
contains bit n can be computed from the expression (n / 32) and
its bit within that integer is (n mod 32).
0 1
+-----------+-----------+-----------+--
| count | 31 .. 0 | 63 .. 32 |
+-----------+-----------+-----------+--
change_info4
struct change_info4 {
bool atomic;
fattr4_change before;
fattr4_change after;
};
This structure is used with the CREATE, LINK, REMOVE, RENAME
operations to let the client know value of the change attribute
for the directory in which the target file system object
resides.
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clientaddr4
struct clientaddr4 {
/* see struct rpcb in RFC 1833 */
string r_netid<>; /* network id */
string r_addr<>; /* universal address */
};
The clientaddr4 structure is used as part of the SETCLIENT
operation to specify the address of either the client that is
using a clientid or as part of the call back registration.
cb_client4
struct cb_client4 {
unsigned int cb_program;
clientaddr4 cb_location;
};
This structure is used by the client to inform the server of its
call back address; includes the program number and client
address.
nfs_client_id4
struct nfs_client_id4 {
opaque verifier[4];
opaque id<>;
};
This structure is part of the arguments to the SETCLIENTID
operation.
nfs_lockowner4
struct nfs_lockowner4 {
clientid4 clientid;
opaque owner<>;
};
This structure is used to identify the owner of a OPEN share or
file lock.
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3. RPC and Security Flavor
The NFS version 4 protocol is a Remote Procedure Call (RPC)
application that uses RPC version 2 and the corresponding eXternal
Data Representation (XDR) as defined in [RFC1831] and [RFC1832]. The
RPCSEC_GSS security flavor as defined in [RFC2203] MUST be used as
the mechanism to deliver stronger security for the NFS version 4
protocol.
3.1. Ports and Transports
Historically, NFS version 2 and version 3 servers have resided on
port 2049. The registered port 2049 [RFC1700] for the NFS protocol
should be the default configuration. Using the registered port for
NFS services means the NFS client will not need to use the RPC
binding protocols as described in [RFC1833]; this will allow NFS to
transit firewalls.
The transport used by the RPC service for the NFS version 4 protocol
MUST provide congestion control comparable to that defined for TCP in
[RFC2581]. If the operating environment implements TCP, the NFS
version 4 protocol SHOULD be supported over TCP. The NFS client and
server may use other transports if they support congestion control as
defined above and in those cases a mechanism may be provided to
override TCP usage in favor of another transport.
If TCP is used as the transport, the client and server SHOULD use
persistent connections. This will prevent the weakening of TCP's
congestion control via short lived connections.
3.2. Security Flavors
Traditional RPC implementations have included AUTH_NONE, AUTH_SYS,
AUTH_DH, and AUTH_KRB4 as security flavors. With [RFC2203] an
additional security flavor of RPCSEC_GSS has been introduced which
uses the functionality of GSS-API [RFC2078]. This allows for the use
of varying security mechanisms by the RPC layer without the
additional implementation overhead of adding RPC security flavors.
For NFS version 4, the RPCSEC_GSS security flavor MUST be used to
enable the mandatory security mechanism. The flavors AUTH_NONE,
AUTH_SYS, and AUTH_DH MAY be implemented as well.
3.2.1. Security mechanisms for NFS version 4
The use of RPCSEC_GSS requires selection of: mechanism, quality of
protection, and service (authentication, integrity, privacy). The
remainder of this document will refer to these three parameters of
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the RPCSEC_GSS security as the security triple.
3.2.1.1. Kerberos V5 as security triple
The Kerberos V5 GSS-API mechanism as described in [RFC1964] MUST be
implemented and provide the following security triples.
column descriptions:
1 == number of pseudo flavor
2 == name of pseudo flavor
3 == mechanism's OID
4 == mechanism's algorithm(s)
5 == RPCSEC_GSS service
1 2 3 4 5
-----------------------------------------------------------------------
390003 krb5 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_none
390004 krb5i 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_integrity
390005 krb5p 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_privacy
for integrity,
and 56 bit DES
for privacy.
Note that the pseudo flavor is presented here as a mapping aid to the
implementor. Because this NFS protocol includes a method to
negotiate security and it understands the GSS-API mechanism, the
pseudo flavor is not needed. The pseudo flavor is needed for NFS
version 3 since the security negotiation is done via the MOUNT
protocol.
For a discussion of NFS' use of RPCSEC_GSS and Kerberos V5, please
see [RFC2623].
3.2.1.2. LIPKEY as a security triple
The LIPKEY GSS-API mechanism as described in [RFCXXXX] MUST be
implemented and provide the following security triples. The
definition of the columns matches the previous subsection "Kerberos
V5 as security triple"
1 2 3 4 5
-----------------------------------------------------------------------
390006 lipkey TBD negotiated rpc_gss_svc_none
390007 lipkey-i TBD negotiated rpc_gss_svc_integrity
390008 lipkey-p TBD negotiated rpc_gss_svc_privacy
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The mechanism algorithm is listed as "negotiated". This is because
LIPKEY is layered on SPKM-3 and in SPKM-3 [RFCXXXX] the
confidentiality and integrity algorithms are negotiated. Since
SPKM-3 specifies HMAC-MD5 for integrity as MANDATORY, 128 bit
cast5CBC for confidentiality for privacy as MANDATORY, and further
specifies that HMAC-MD5 and cast5CBC MUST be listed first before
weaker algorithms, specifying "negotiated" in column 4 does not
impair interoperability. In the event an SPKM-3 does not support the
mandatory algorithms, the other peer is free to accept or reject the
GSS-API context creation.
Because SPKM-3 negotiates the algorithms, subsequent calls to
LIPKEY's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality
of protection value of 0 (zero). See section 5.2 of [RFC2025] for an
explanation.
LIPKEY uses SPKM-3 to create a secure channel in which to pass a user
name and password from the client to the user. Once the user name
and password have been accepted by the server, calls to the LIPKEY
context are redirected to the SPKM-3 context. See [RFCXXXX] for more
details.
3.2.1.3. SPKM-3 as a security triple
The SPKM-3 GSS-API mechanism as described in [RFCXXXX] MUST be
implemented and provide the following security triples. The
definition of the columns matches the previous subsection "Kerberos
V5 as security triple".
1 2 3 4 5
-----------------------------------------------------------------------
390009 spkm3 TBD negotiated rpc_gss_svc_none
390010 spkm3i TBD negotiated rpc_gss_svc_integrity
390011 spkm3p TBD negotiated rpc_gss_svc_privacy
For a discussion as to why the mechanism algorithm is listed as
"negotiated", see the previous section "LIPKEY as a security triple."
Because SPKM-3 negotiates the algorithms, subsequent calls to SPKM-
3's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality of
protection value of 0 (zero). See section 5.2 of [RFC2025] for an
explanation.
Even though LIPKEY is layered onto SPKM-3, SPKM-3 is specified as a
mandatory set of triples to handle the situation when the initiator
(the client) is anonymous. If the initiator is anonymous, there will
not be a user name and password to send to the target (the server).
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3.3. Security Negotiation
With the NFS version 4 server potentially offering multiple security
mechanisms, the client needs a method to determine or negotiate which
mechanism is to be used for its communication with the server. The
NFS server may have multiple points within its file system name space
that are available for use by NFS clients. In turn the NFS server
may be configured such that each of these entry points may have
different or multiple security mechanisms in use.
The security negotiation between client and server must be done with
a secure channel to eliminate the possibility of a third party
intercepting the negotiation sequence and forcing the client and
server to choose a lower level of security than required or desired.
3.3.1. Security Error
Based on the assumption that each NFS version 4 client and server
must support a minimum set of security (i.e. LIPKEY, SPKM-3, and
Kerberos-V5 all under RPCSEC_GSS), the NFS client will start its
communication with the server with one of the minimal security
triples. During communication with the server, the client may
receive an NFS error of NFS4ERR_WRONGSEC. This error allows the
server to notify the client that the security triple currently being
used is not appropriate for access to the server's file system
resources. The client is then responsible for determining what
security triples are available at the server and choose one which is
appropriate for the client.
3.3.2. SECINFO
The new SECINFO operation will allow the client to determine, on a
per filehandle basis, what security triple is to be used for server
access. In general, the client will not have to use the SECINFO
procedure except during initial communication with the server or when
the client crosses policy boundaries at the server. It is possible
that the server's policies change during the client's interaction
therefore forcing the client to negotiate a new security triple.
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4. Filehandles
The filehandle in the NFS protocol is a per server unique identifier
for a file system object. The contents of the filehandle are opaque
to the client. Therefore, the server is responsible for translating
the filehandle to an internal representation of the file system
object. Since the filehandle is the client's reference to an object
and the client may cache this reference, the server should not reuse
a filehandle for another file system object. If the server needs to
reuse a filehandle value, the time elapsed before reuse SHOULD be
large enough that it is likely the client no longer has a cached copy
of the reused filehandle value.
4.1. Obtaining the First Filehandle
The operations of the NFS protocol are defined in terms of one or
more filehandles. Therefore, the client needs a filehandle to
initiate communication with the server. With the NFS version 2
protocol [RFC1094] and the NFS version 3 protocol [RFC1813], there
exists an ancillary protocol to obtain this first filehandle. The
MOUNT protocol, RPC program number 100005, provides the mechanism of
translating a string based file system path name to a filehandle
which can then be used by the NFS protocols.
The MOUNT protocol has deficiencies in the area of security and use
via firewalls. This is one reason that the use of the public
filehandle was introduced in [RFC2054] and [RFC2055]. With the use
of the public filehandle in combination with the LOOKUP procedure in
the NFS version 2 and 3 protocols, it has been demonstrated that the
MOUNT protocol is unnecessary for viable interaction between NFS
client and server.
Therefore, the NFS version 4 protocol will not use an ancillary
protocol for translation from string based path names to a
filehandle. Two special filehandles will be used as starting points
for the NFS client.
4.1.1. Root Filehandle
The first of the special filehandles is the ROOT filehandle. The
ROOT filehandle is the "conceptual" root of the file system name
space at the NFS server. The client uses or starts with the ROOT
filehandle by employing the PUTROOTFH operation. The PUTROOTFH
operation instructs the server to set the "current" filehandle to the
ROOT of the server's file tree. Once this PUTROOTFH operation is
used, the client can then traverse the entirety of the server's file
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tree with the LOOKUP procedure. A complete discussion of the server
name space is in the section "NFS Server Name Space".
4.1.2. Public Filehandle
The second special filehandle is the PUBLIC filehandle. Unlike the
ROOT filehandle, the PUBLIC filehandle may be bound or represent an
arbitrary file system object at the server. The server is
responsible for this binding. It may be that the PUBLIC filehandle
and the ROOT filehandle refer to the same file system object.
However, it is up to the administrative software at the server and
the policies of the server administrator to define the binding of the
PUBLIC filehandle and server file system object. The client may not
make any assumptions about this binding.
4.2. Filehandle Types
In the NFS version 2 and 3 protocols, there was one type of
filehandle with a single set of semantics. The NFS version 4
protocol introduces a new type of filehandle in an attempt to
accommodate certain server environments. The first type of
filehandle is 'persistent'. The semantics of a persistent filehandle
are the same as the filehandles of the NFS version 2 and 3 protocols.
The second or new type of filehandle is the "volatile" filehandle.
The volatile filehandle type is being introduced to address server
functionality or implementation issues which prevent correct or
feasible implementation of a persistent filehandle. Some server
environments do not provide a file system level invariant that can be
used to construct a persistent filehandle. The underlying server
file system may not provide the invariant or the server's file system
programming interfaces may not provide access to the needed
invariant. Volatile filehandles may ease the implementation of
server functionality such as hierarchical storage management or file
system reorganization or migration. However, the volatile filehandle
increases the implementation burden for the client. However this
increased burden is deemed acceptable based on the overall gains
achieved by the protocol.
Since the client will have different paths of logic to handle
persistent and volatile filehandles, a file attribute is defined
which may be used by the client to determine the filehandle types
being returned by the server.
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4.2.1. General Properties of a Filehandle
The filehandle contains all the information the server needs to
distinguish an individual file. To the client, the filehandle is
opaque. The client stores filehandles for use in a later request and
can compare two filehandles from the same server for equality by
doing a byte-by-byte comparison. However, the client MUST NOT
otherwise interpret the contents of filehandles. If two filehandles
from the same server are equal, they MUST refer to the same file. If
they are not equal, no conclusions can be drawn. Servers SHOULD try
to maintain a one-to-one correspondence between filehandles and files
but this is not required. Clients MUST only use filehandle
comparisons only to improve performance, not for correct behavior.
Further discussion of filehandle and attribute comparison in the
context of data caching is presented in the section "Data Caching and
File Identity".
As an example, in the case that two different path names when
traversed at the server terminate at the same file system object, the
server SHOULD return the same filehandle for each path. This can
occur if a hard link is used to create two file names which refer to
the same underlying file object and associated data. For example, if
paths /a/b/c and /a/d/c refer to the same file, the server SHOULD
return the same filehandle for both path names traversals.
4.2.2. Persistent Filehandle
A persistent filehandle is defined as having a persistent value for
the lifetime of the file system object to which it refers. Once the
server creates the filehandle for a file system object, the server
MUST accept the same filehandle for the object for the lifetime of
the object. If the server restarts or reboots, or the file system is
migrated, the NFS server must honor the same filehandle value as it
did in the server's previous instantiation.
The persistent filehandle will be become stale or invalid when the
file system object is removed. When the server is presented with a
persistent filehandle that refers to a deleted object, it MUST return
an error of NFS4ERR_STALE. A filehandle may become stale when the
file system containing the object is no longer available. The file
system may become unavailable if it exists on removable media and the
media is no longer available at the server or the file system in
whole has been destroyed or the file system has simply been removed
from the server's name space (i.e. unmounted in a Unix environment).
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4.2.3. Volatile Filehandle
A volatile filehandle does not share the same longevity attributes of
the persistent filehandle. The server may determine that a volatile
filehandle is no longer valid at many different points in time. If
the server can definitively determine that a volatile filehandle
refers to an object that has been removed, the server should return
NFS4ERR_STALE to the client (as is the case for persistent
filehandles). In all other cases where the server determines that a
volatile filehandle can no longer be used, it should return an error
of NFS4ERR_FHEXPIRED.
The mandatory attribute "fh_expire_type" is used by the client to
determine what type of filehandle the server is providing for a
particular file system. This attribute is a bitmask with the
following values:
FH4_PERSISTENT
The filehandle is valid until the object is removed from the
file system. The server will not return NFS4ERR_FHEXPIRED for
this filehandle.
FH4_NOEXPIRE_WITH_OPEN
The filehandle will not expire while client has the file open.
If this bit is set, then the values defined as follows do not
impact expiration while the file is open. Once the file is
closed or if the FH4_NOEXPIRE_WITH_OPEN bit is false, the rest
of the volatile related bits apply.
FH4_VOLATILE_ANY
The filehandle may expire at any time.
FH4_VOL_MIGRATION
The filehandle may expire during file system migration. May
only be set if FH4_VOLATILE_ANY is not set.
FH4_VOL_RENAME
The filehandle may expire due to a rename. This includes a
rename by the requesting client or a rename by another client.
May only be set if FH4_VOLATILE_ANY is not set.
Servers which provide volatile filehandles should deny a RENAME or
REMOVE that would effect an OPEN file or any of the components
leading to the OPEN file. In addition, the server should deny all
RENAME or REMOVE requests during the grace or lease period upon
server restart.
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4.2.4. One Method of Constructing a Volatile Filehandle
As mentioned, in some instances a filehandle is stale (no longer
valid; perhaps because the file was removed from the server) or it is
expired (the underlying file is valid but since the filehandle is
volatile, it may have expired). Thus the server needs to be able to
return NFS4ERR_STALE in the former case and NFS4ERR_FHEXPIRED in the
latter case. This can be done by careful construction of the volatile
filehandle. One possible implementation follows.
A volatile filehandle, while opaque to the client could contain:
[volatile bit = 1 | server boot time | slot | generation number]
o slot is an index in the server volatile filehandle table
o generation number is the generation number for the table
entry/slot
If the server boot time is less than the current server boot time,
return NFS4ERR_FHEXPIRED. If slot is out of range, return
NFS4ERR_BADHANDLE. If the generation number does not match, return
NFS4ERR_FHEXPIRED.
When the server reboots, the table is gone (it is volatile).
If volatile bit is 0, then it is a persistent filehandle with a
different structure following it.
4.3. Client Recovery from Filehandle Expiration
If possible, the client SHOULD recover from the receipt of an
NFS4ERR_FHEXPIRED error. The client must take on additional
responsibility so that it may prepare itself to recover from the
expiration of a volatile filehandle. If the server returns
persistent filehandles, the client does not need these additional
steps.
For volatile filehandles, most commonly the client will need to store
the component names leading up to and including the file system
object in question. With these names, the client should be able to
recover by finding a filehandle in the name space that is still
available or by starting at the root of the server's file system name
space.
If the expired filehandle refers to an object that has been removed
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from the file system, obviously the client will not be able to
recover from the expired filehandle.
It is also possible that the expired filehandle refers to a file that
has been renamed. If the file was renamed by another client, again
it is possible that the original client will not be able to recover.
However, in the case that the client itself is renaming the file and
the file is open, it is possible that the client may be able to
recover. The client can determine the new path name based on the
processing of the rename request. The client can then regenerate the
new filehandle based on the new path name. The client could also use
the compound operation mechanism to construct a set of operations
like:
RENAME A B
LOOKUP B
GETFH
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5. File Attributes
To meet the requirements of extensibility and increased
interoperability with non-Unix platforms, attributes must be handled
in a flexible manner. The NFS Version 3 fattr3 structure contains a
fixed list of attributes that not all clients and servers are able to
support or care about. The fattr3 structure can not be extended as
new needs arise and it provides no way to indicate non-support. With
the NFS Version 4 protocol, the client will be able to ask what
attributes the server supports and will be able to request only those
attributes in which it is interested.
To this end, attributes will be divided into three groups: mandatory,
recommended, and named. Both mandatory and recommended attributes
are supported in the NFS version 4 protocol by a specific and well-
defined encoding and are identified by number. They are requested by
setting a bit in the bit vector sent in the GETATTR request; the
server response includes a bit vector to list what attributes were
returned in the response. New mandatory or recommended attributes
may be added to the NFS protocol between major revisions by
publishing a standards-track RFC which allocates a new attribute
number value and defines the encoding for the attribute. See the
section "Minor Versioning" for further discussion.
Named attributes are accessed by the new OPENATTR operation, which
accesses a hidden directory of attributes associated with a file
system object. OPENATTR takes a filehandle for the object and
returns the filehandle for the attribute hierarchy. The filehandle
for the named attributes is a directory object accessible by LOOKUP
or READDIR and contains files whose names represent the named
attributes and whose data bytes are the value of the attribute. For
example:
LOOKUP "foo" ; look up file
GETATTR attrbits
OPENATTR ; access foo's named attributes
LOOKUP "x11icon" ; look up specific attribute
READ 0,4096 ; read stream of bytes
Named attributes are intended primarily for data needed by
applications rather than by an NFS client implementation. NFS
implementors are strongly encouraged to define their new attributes
as recommended attributes by bringing them to the IETF standards-
track process.
The set of attributes which are classified as mandatory is
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deliberately small since servers must do whatever it takes to support
them. The recommended attributes may be unsupported; though a server
should support as many as it can. Attributes are deemed mandatory if
the data is both needed by a large number of clients and is not
otherwise reasonably computable by the client when support is not
provided on the server.
5.1. Mandatory Attributes
These MUST be supported by every NFS Version 4 client and server in
order to ensure a minimum level of interoperability. The server must
store and return these attributes and the client must be able to
function with an attribute set limited to these attributes. With
just the mandatory attributes some client functionality may be
impaired or limited in some ways. A client may ask for any of these
attributes to be returned by setting a bit in the GETATTR request and
the server must return their value.
5.2. Recommended Attributes
These attributes are understood well enough to warrant support in the
NFS Version 4 protocol. However, they may not be supported on all
clients and servers. A client may ask for any of these attributes to
be returned by setting a bit in the GETATTR request but must handle
the case where the server does not return them. A client may ask for
the set of attributes the server supports and should not request
attributes the server does not support. A server should be tolerant
of requests for unsupported attributes and simply not return them
rather than considering the request an error. It is expected that
servers will support all attributes they comfortably can and only
fail to support attributes which are difficult to support in their
operating environments. A server should provide attributes whenever
they don't have to "tell lies" to the client. For example, a file
modification time should be either an accurate time or should not be
supported by the server. This will not always be comfortable to
clients but it seems that the client has a better ability to
fabricate or construct an attribute or do without the attribute.
5.3. Named Attributes
These attributes are not supported by direct encoding in the NFS
Version 4 protocol but are accessed by string names rather than
numbers and correspond to an uninterpreted stream of bytes which are
stored with the file system object. The namespace for these
attributes may be accessed by using the OPENATTR operation. The
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OPENATTR operation returns a filehandle for a virtual "attribute
directory" and further perusal of the name space may be done using
READDIR and LOOKUP operations on this filehandle. Named attributes
may then be examined or changed by normal READ and WRITE and CREATE
operations on the filehandles returned from READDIR and LOOKUP.
Named attributes may have attributes. For example, a security label
may have access control information in its own right.
It is recommended that servers support arbitrary named attributes. A
client should not depend on the ability to store any named attributes
in the server's file system. If a server does support named
attributes, a client which is also able to handle them should be able
to copy a file's data and meta-data with complete transparency from
one location to another; this would imply that there should be no
attribute names which will be considered illegal by the server.
Names of attributes will not be controlled by a standards body.
However, vendors and application writers are encouraged to register
attribute names and the interpretation and semantics of the stream of
bytes via informational RFCs so that other implementations may
interoperate where common interests exist.
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5.4. Mandatory Attributes - Definitions
Name # DataType Access Description
___________________________________________________________________
supp_attr 0 bitmap READ The bit vector which
would retrieve all
mandatory and
recommended attributes
which may be requested
for this object.
The client must ask
this question to
request correct
attributes.
object_type 1 nfs4_ftype READ The type of the object
(file, directory,
symlink)
The client cannot
handle object
correctly without
type.
fh_expire_type 2 uint32 READ Server uses this to
specify filehandle
expiration behavior to
the client. See the
section "Filehandles"
for additional
description.
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change 3 uint64 READ A value created by the
server that the client
can use to determine
if file data,
directory contents or
attributes of the
object have been
modified. The server
may return the
object's time_modify
attribute for this
attribute's value but
only if the file
system object can not
be updated more
frequently than the
resolution of
time_modify.
object_size 4 uint64 R/W The size of the object
in bytes.
Could be very
expensive to derive,
likely to be
available.
link_support 5 boolean READ Does the object's file
system supports hard
links?
Server can easily
determine if links are
supported.
symlink_support 6 boolean READ Does the object's file
system supports
symbolic links?
Server can easily
determine if links are
supported.
named_attr 7 boolean READ Does this object have
named attributes?
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fsid 8 fsid4 READ Unique file system
identifier for the
file system holding
this object. fsid
contains major and
minor components each
of which are uint64.
unique_handles 9 boolean READ Are two distinct
filehandles guaranteed
to refer to two
different file system
objects?
lease_time 10 nfs_lease4 READ Duration of leases at
server in seconds.
rdattr_error 11 enum READ Error returned from
getattr during
readdir.
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5.5. Recommended Attributes - Definitions
Name # Data Type Access Description
_____________________________________________________________________
ACL 12 nfsace4<> R/W The access control
list for the object.
[The nature and
format of ACLs is
still to be
determined.]
aclsupport 13 uint32 READ Indicates what ACLs
are supported on the
current file system.
archive 14 boolean R/W Whether or not this
file has been
archived since the
time of last
modification
(deprecated in favor
of backup_time).
cansettime 15 boolean READ Whether or not this
object's file system
can fill in the times
on a SETATTR request
without an explicit
time.
case_insensitive 16 boolean READ Are filename
comparisons on this
file system case
insensitive?
case_preserving 17 boolean READ Is filename case on
this file system
preserved?
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chown_restricted 18 boolean READ If TRUE, the server
will reject any
request to change
either the owner or
the group associated
with a file if the
caller is not a
privileged user (for
example, "root" in
Unix operating
environments or in NT
the "Take Ownership"
privilege)
filehandle 19 nfs4_fh READ The filehandle of
this object
(primarily for
readdir requests).
fileid 20 uint64 READ A number uniquely
identifying the file
within the file
system.
files_avail 21 uint64 READ File slots available
to this user on the
file system
containing this
object - this should
be the smallest
relevant limit.
files_free 22 uint64 READ Free file slots on
the file system
containing this
object - this should
be the smallest
relevant limit.
files_total 23 uint64 READ Total file slots on
the file system
containing this
object.
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fs_locations 24 fs_locations READ Locations where this
file system may be
found. If the server
returns NFS4ERR_MOVED
as an error, this
attribute must be
supported.
hidden 25 boolean R/W Is file considered
hidden with respect
to the WIN32 API.
homogeneous 26 boolean READ Whether or not this
object's file system
is homogeneous, i.e.
whether pathconf is
the same for all file
system objects.
maxfilesize 27 uint64 READ Maximum supported
file size for the
file system of this
object.
maxlink 28 uint32 READ Maximum number of
links for this
object.
maxname 29 uint32 READ Maximum filename size
supported for this
object.
maxread 30 uint64 READ Maximum read size
supported for this
object.
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maxwrite 31 uint64 READ Maximum write size
supported for this
object. This
attribute SHOULD be
supported if the file
is writable. Lack of
this attribute can
lead to the client
either wasting
bandwidth or not
receiving the best
performance.
mime_type 32 utf8<> R/W MIME body
type/subtype of this
object.
mode 33 mode4 R/W Unix-style permission
bits for this object
(deprecated in favor
of ACLs)
no_trunc 34 boolean READ If a name longer than
name_max is used,
will an error be
returned or will the
name be truncated?
numlinks 35 uint32 READ Number of links to
this object.
owner 36 utf8<> R/W The string name of
the owner of this
object.
owner_group 37 utf8<> R/W The string name of
the group of the
owner of this object.
quota_hard 38 uint64 READ For definition see
"Quota Attributes"
section below.
quota_soft 39 uint64 READ For definition see
"Quota Attributes"
section below.
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quota_used 40 uint64 READ For definition see
"Quota Attributes"
section below.
rawdev 41 specdata4 READ Raw device
identifier.
space_avail 42 uint64 READ Disk space in bytes
available to this
user on the file
system containing
this object - this
should be the
smallest relevant
limit.
space_free 43 uint64 READ Free disk space in
bytes on the file
system containing
this object - this
should be the
smallest relevant
limit.
space_total 44 uint64 READ Total disk space in
bytes on the file
system containing
this object.
space_used 45 uint64 READ Number of file system
bytes allocated to
this object.
system 46 boolean R/W Is this file is a
system file with
respect to the WIN32
API.
time_access 47 nfstime4 R/W The time of last
access to the object.
time_backup 48 nfstime4 R/W The time of last
backup of the object.
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time_create 49 nfstime4 R/W The time of creation
of the object. This
attribute does not
have any relation to
the traditional Unix
file attribute
"ctime" or "change
time".
time_delta 50 nfstime4 READ Smallest useful
server time
granularity.
time_metadata 51 nfstime4 R/W The time of last
meta-data
modification of the
object.
time_modify 52 nfstime4 R/W The time since the
epoch of last
modification to the
object.
version 53 utf8<> R/W Version number of
this document.
volatility 54 nfstime4 READ Approximate time
until next expected
change on this file
system, as a measure
of volatility.
5.6. Interpreting owner and owner_group
The recommended attributes "owner" and "owner_group" are represented
in terms of a UTF-8 string. To avoid a representation that is tied
to a particular underlying implementation at the client or server,
the use of the UTF-8 string has been chosen. Note that section 6.1
of [RFC2624] provides additional rationale. It is expected that the
client and server will have their own local representation of owner
and owner_group that is used for local storage or presentation to the
end user. Therefore, it is expected that the when these attributes
are transferred between the client and server that the local
representation is translated to a syntax of the form
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"user@dns_domain". This will allow for a client and server that do
not use the same local representation the ability to translate to a
common syntax that can be interpreted by both.
The translation is not specified as part of the protocol. This
allows various solutions to be employed. For example, a local
translation table may be consulted that maps between a numeric id to
the user@dns_domain syntax. A name service may also be used to
accomplish the translation. The "dns_domain" portion of the owner
string is meant to be a DNS domain name. For example, user@ietf.org.
In the case where there is no translation available to the client or
server, the attribute value must be constructed without the "@".
Therefore, the absence of the @ from the owner or owner_group
attribute signifies that no translation was available and the
receiver of the attribute should not place any special meaning with
the attribute value. Even though the attribute value can not be
translated, it may still be useful. In the case of a client, the
attribute string may be used for local display of ownership.
5.7. Quota Attributes
For the attributes related to file system quotas, the following
definitions apply:
quota_avail_soft
The value in bytes which represents the amount of extra disc
space that can be allocated to this file before the user may
reasonably be warned. It is understood that this space may be
consumed by allocations to other files though there is a rule as
to which other files.
quota_avail_hard
The value in bytes which represent the amount of extra disc
space that can be allocated to this file before further
allocations will be declined. It is understood that this space
may be consumed by allocations to other files.
quota_used
The value in bytes which represent the amount of disc space used
by this file and possibly a number of other similar files, where
the set of "similar" files meets at least the criterion that
allocating space to any file in the set will reduce the
"quota_avail_hard" of every other file in the set.
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Note that there may be a number of distinct but overlapping sets
of files for which a quota_used value is maintained. E.g. "all
files with a given owner", "all files with a given group owner".
etc.
The server is at liberty to choose any of those sets, but should
do so in a repeatable way. The rule may be configured per-
filesystem, or may be "choose the set with the smallest quota".
5.8. Access Control Lists
The NFS ACL attribute is an array of access control entries (ACE).
There are various access control entry types. The server is able to
communicate which ACE types are support by returning the appropriate
value within the aclsupport attribute. The types of ACEs are defined
as follows:
Type Description
_____________________________________________________
ALLOW Explicitly grants the access defined in
acemask4 to the file or directory.
DENY Explicitly denies the access defined in
acemask4 to the file or directory.
AUDIT LOG (system dependant) any access
attempt to a file or directory which
uses an access method which is a subset
of acemask4.
ALARM Generate a system ALARM (system
dependant) when any access attempt is
made to a file or directory which is a
subset of acemask4
The NFS ACE attribute is defined as follows:
typedef uint32_t acetype4;
typedef uint32_t aceflag4;
typedef uint32_t acemask4;
struct nfsace4 {
acetype4 type;
aceflag4 flag;
acemask4 access_mask;
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utf8string who;
};
To determine if an ACCESS or OPEN request succeeds each nfsace4 entry
is processed in order by the server. Only ACEs which have a "who"
that matches the requester are considered. Each ACE is processed
until all of the bits of the requester's access have been ALLOWED.
Once a bit (see below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it
is no longer considered in the processing of later ACEs. If an
ACCESS_DENIED_ACE is encountered where the requester's mode still has
unALLOWED bits in common with the "access_mask" of the ACE, the
request is denied.
5.8.1. ACE type
The semantics of the "type" field follow the descriptions provided
above.
5.8.2. ACE flag
The "flag" field contains values based on the following descriptions.
ACE4_FILE_INHERIT_ACE
Can be placed on a directory and indicates that this ACE should be
added to each new non-directory file created.
ACE4_DIRECTORY_INHERIT_ACE
Can be placed on a directory and indicates that this ACE should be
added to each new directory created.
ACE4_INHERIT_ONLY_ACE
Can be placed on a directory but does not apply to the directory,
only to newly created files/directories as specified by the above two
flags.
ACE4_NO_PROPAGATE_INHERIT_ACE
Can be placed on a directory. Normally when a new directory is
created and an ACE exists on the parent directory which is marked
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ACL4_DIRECTORY_INHERIT_ACE, two ACEs are placed on the new directory.
One for the directory itself and one which is an inheritable ACE for
newly created directories. This flag tells the O/S to not place an
ACE on the newly created directory which is inheritable by
subdirectories of the created directory.
ACE4_SUCCESSFUL_ACCESS_ACE_FLAG
ACL4_FAILED_ACCESS_ACE_FLAG
Both indicate for AUDIT and ALARM which state to log the event. On
every ACCESS or OPEN call which occurs on a file or directory which
has an ACL that is of type ACE4_SYSTEM_AUDIT_ACE_TYPE or
ACE4_SYSTEM_ALARM_ACE_TYPE, the attempted access is compared to the
ace4mask of these ACLs. If the access is a subset of ace4mask and the
identifier match, an AUDIT trail or an ALARM is generated. By
default this happens regardless of the success or failure of the
ACCESS or OPEN call.
The flag ACE4_SUCCESSFUL_ACCESS_ACE_FLAG only produces the AUDIT or
ALARM if the ACCESS or OPEN call is successful. The
ACE4_FAILED_ACCESS_ACE_FLAG causes the ALARM or AUDIT if the ACCESS
or OPEN call fails.
ACE4_IDENTIFIER_GROUP
Indicates that the "who" refers to a GROUP as defined under Unix.
5.8.3. ACE Access Mask
The access_mask field contains values based on the following:
Access Description
_______________________________________________________________
READ_DATA Permission to read the data of the file
LIST_DIRECTORY Permission to list the contents of a
directory
WRITE_DATA Permission to modify the file's data
ADD_FILE Permission to add a new file to a
directory
APPEND_DATA Permission to append data to a file
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ADD_SUBDIRECTORY Permission to create a subdirectory to a
directory
READ_STREAMS Permission to read the additional
streams of a file
WRITE_STREAMS Permission to write the additional
streams of a file
EXECUTE Permission to execute a file
DELETE_CHILD Permission to delete a file or directory
within a directory
READ_ATTRIBUTES The ability to read basic attributes
(non-acls) of a file
WRITE_ATTRIBUTES Permission to change basic attributes
(non-acls) of a file
DELETE Permission to Delete the File, IF FILE
BASED
READ_ACL Permission to Read the ACL
WRITE_ACL Permission to Write the ACL
WRITE_OWNER Permission to change the owner
SYNCHRONIZE Allow the forcing of mutual-exclusion to
the file
5.8.4. ACE who
There are several special identifiers ("who") which need to be
understood universally. Some of these identifiers cannot be
understood when an NFS client accesses the server, but have meaning
when a local process accesses the file. The ability to display and
modify these permissions is permitted over NFS.
Who Description
_______________________________________________________________
"OWNER" The owner of the file.
"GROUP" The group associated with the file.
"EVERYONE" The world.
"INTERACTIVE" Accessed from an interactive terminal.
"NETWORK" Accessed via the network.
"DIALUP" Accessed as a dialup user to the server.
"BATCH" Accessed from a batch job.
"ANONYMOUS" Accessed without any authentication.
"AUTHENTICATED" Any authenticated user (opposite of
ANONYMOUS)
"SERVICE" Access from a system service.
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To avoid conflict these special identifiers should be of the form
"xxxx@". For example: ANONYMOUS@.
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6. File System Migration and Replication
With the use of the recommended attribute "fs_locations", the NFS
version 4 server has a method of providing file system migration or
replication services. For the purposes of migration and replication,
a file system will be defined as all files that share a given fsid
(major and minor values are the same).
The fs_locations attribute provides a list of file system locations.
These locations are specified by providing the server name (either
DNS domain or IP address) and the path name representing the root of
the file system. Depending on the type of service being provided,
the list will provide a new or alternate locations for the file
system. The client will use this information to redirect its
requests to the new server.
6.1. Replication
It is expected that file system replication will be used in the case
of read-only data. Typically, the file system will be replicated
amongst two or more servers. The fs_locations attribute will provide
the list of these locations to the client. On first access of the
file system, the client should obtain the value of the fs_locations
attribute. If, in the future, the client finds the server
unresponsive, the client may attempt to use another server specified
by fs_locations.
If applicable, the client must take the appropriate steps to recover
valid filehandles from the new server. This is described in more
detail in the following sections.
6.2. Migration
File system migration is used to move a file system from one server
to another. Migration is typically used for a file system that is
writable and has a single copy. The expected use of migration is for
load balancing or general resource reallocation. The protocol does
not specify how the file system will be moved between servers. This
server-to-server transfer mechanism is left to the server
implementor. However, the method used to communicate the migration
event between client and server is specified here.
Once the servers participating in the migration have completed the
move of the file system, the error NFS4ERR_MOVED will be returned for
subsequent requests received by the original server. The
NFS4ERR_MOVED error is returned for all operations except GETATTR.
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Upon receiving the NFS4ERR_MOVED error, the client will obtain the
value of the fs_locations attribute. The client will then use the
contents of the attribute to redirect its requests to the specified
server. To facilitate the use of GETATTR operations such as PUTFH
must also be accepted by the server for the migrated file system's
filehandles. Note that if the server returns NFS4ERR_MOVED, the
server MUST support the fs_locations attribute.
If the client requests more attributes than fs_locations, the server
may return fs_locations only. This is to be expected since the
server has migrated the file system and may not have a method of
obtaining additional attribute data.
The server implementor needs to be careful in developing a migration
solution. The server must consider all of the state information
clients may have outstanding at the server. This includes but is not
limited to locking/share state, delegation state, and asynchronous
file writes which are represented by WRITE and COMMIT verifiers. The
server should strive to minimize the impact on its clients during and
after the migration process.
6.3. Interpretation of the fs_locations Attribute
The fs_location attribute is structured in the following way:
struct fs_location {
utf8string server<>;
pathname4 rootpath;
};
struct fs_locations {
pathname4 fs_root;
fs_location locations<>;
};
The fs_location struct is used to represent the location of a file
system by providing a server name and the path to the root of the
file system. For a multi-homed server or a set of servers that use
the same rootpath, an array of server names may be provided. An
entry in the server array is an UTF8 string and represents one of a
traditional DNS host name, IPv4 address, or IPv6 address. It is not
a requirement that all servers that share the same rootpath be listed
in one fs_location struct. The array of server names is provided for
convenience. Servers that share the same rootpath may also be listed
in separate fs_location entries in the fs_locations attribute.
The fs_locations struct and attribute then contains an array of
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locations. Since the namespace of each server may be constructed
differently, the "fs_root" field is provided. The path represented
by fs_root represents the location of the file system in the server's
namespace. Therefore, the fs_root path is only associated with the
server from which the fs_locations attribute was obtained. The
fs_root path is meant to aid the client in locating the file system
at the various servers listed.
As an example, there is a replicated file system located at two
servers (servA and servB). At servA the file system is located at
path "/a/b/c". At servB the file system is located at path "/x/y/z".
In this example the client accesses the file system first at servA
with a multi-component lookup path of "/a/b/c/d". Since the client
used a multi-component lookup to obtain the filehandle at "/a/b/c/d",
it is unaware that the file system's root is located in servA's
namespace at "/a/b/c". When the client switches to servB, it will
need to determine that the directory it first referenced at servA is
now represented by the path "/x/y/z/d" on servB. To facilitate this,
the fs_locations attribute provided by servA would have a fs_root
value of "/a/b/c" and two entries in fs_location. One entry in
fs_location will be for itself (servA) and the other will be for
servB with a path of "/x/y/z". With this information, the client is
able to substitute "/x/y/z" for the "/a/b/c" at the beginning of its
access path and construct "/x/y/z/d" to use for the new server.
6.4. Filehandle Recovery for Migration or Replication
Filehandles for file systems that are replicated or migrated have the
same semantics as for file systems that are not replicated or
migrated. For example, if a file system has persistent filehandles
and it is migrated to another server, the filehandle values for the
file system will be valid at the new server.
The same is true for a file system which is made up of volatile
filehandles. In fact, in this case the client should expect that the
new server will return NFS4ERR_FHEXPIRED when old filehandles are
presented; the client will need to recover the filehandles
appropriately.
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7. NFS Server Namespace
7.1. Server Exports
On a UNIX server the name space describes all the files reachable by
pathnames under the root directory or "/". On a Windows NT server
the name space constitutes all the files on disks named by mapped
disk letters. NFS server administrators rarely make the entire
server's file system name space available to NFS clients. More often
portions of the name space are made available via an "export"
feature. In previous versions of the NFS protocol, the root
filehandle for each export is obtained through the MOUNT protocol;
the client sends a string that identifies the export of name space
and the server returns the root filehandle for it. The MOUNT
protocol supports an EXPORTS procedure that will enumerate the
server's exports.
7.2. Browsing Exports
The NFS version 4 protocol provides a root filehandle that clients
can use to obtain filehandles for these exports via a multi-component
LOOKUP. A common user experience is to use a graphical user
interface (perhaps a file "Open" dialog window) to find a file via
progressive browsing through a directory tree. The client must be
able to move from one export to another export via single-component,
progressive LOOKUP operations.
This style of browsing is not well supported by the NFS version 2 and
3 protocols. The client expects all LOOKUP operations to remain
within a single server file system. For example, the device
attribute will not change. This prevents a client from taking name
space paths that span exports.
An automounter on the client can obtain a snapshot of the server's
name space using the EXPORTS procedure of the MOUNT protocol. If it
understands the server's pathname syntax, it can create an image of
the server's name space on the client. The parts of the name space
that are not exported by the server are filled in with a "pseudo file
system" that allows the user to browse from one mounted file system
to another. There is a drawback to this representation of the
server's name space on the client: it is static. If the server
administrator adds a new export the client will be unaware of it.
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7.3. Server Pseudo File System
NFS version 4 servers avoid this name space inconsistency by
presenting all the exports within the framework of a single server
name space. An NFS version 4 client uses LOOKUP and READDIR
operations to browse seamlessly from one export to another. Portions
of the server name space that are not exported are bridged via a
"pseudo file system" that provides a view of exported directories
only. A pseudo file system has a unique fsid and behaves like a
normal, read only file system.
Based on the construction of the server's name space, it is possible
that multiple pseudo filesystems may exist. For example,
/a pseudo file system
/a/b real file system
/a/b/c pseudo file system
/a/b/c/d real file system
Each of the pseudo file systems are consider separate entities and
therefore will have a unique fsid.
7.4. Multiple Roots
The DOS and Windows operating environments are sometimes described as
having "multiple roots". File systems are commonly represented as
disk letters. MacOS represents file systems as top level names. NFS
version 4 servers for these platforms can construct a pseudo file
system above these root names so that disk letters or volume names
are simply directory names in the pseudo root.
7.5. Filehandle Volatility
The nature of the server's pseudo file system is that it is a logical
representation of file system(s) available from the server.
Therefore, the pseudo file system is most likely constructed
dynamically when the server is first instantiated. It is expected
that the pseudo file system may not have an on disk counterpart from
which persistent filehandles could be constructed. Even though it is
preferable that the server provide persistent filehandles for the
pseudo file system, the NFS client should expect that pseudo file
system filehandles are volatile. This can be confirmed by checking
the associated "persistent_fh" attribute for those filehandles in
question. If the filehandles are volatile, the NFS client must be
prepared to recover a filehandle value (i.e. with a v4 multi-
component LOOKUP) when receiving an error of NFS4ERR_FHEXPIRED.
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7.6. Exported Root
If the server's root file system is exported, it might be easy to
conclude that a pseudo-file system is not needed. This would be
wrong. Assume the following file systems on a server:
/ disk1 (exported)
/a disk2 (not exported)
/a/b disk3 (exported)
Because disk2 is not exported, disk3 cannot be reached with simple
LOOKUPs. The server must bridge the gap with a pseudo-file system.
7.7. Mount Point Crossing
The server file system environment may be constructed in such a way
that one file system contains a directory which is 'covered' or
mounted upon by a second file system. For example:
/a/b (file system 1)
/a/b/c/d (file system 2)
The pseudo file system for this server may be constructed to look
like:
/ (place holder/not exported)
/a/b (file system 1)
/a/b/c/d (file system 2)
It is the server's responsibility to present the pseudo file system
that is complete to the client. If the client sends a lookup request
for the path "/a/b/c/d", the server's response is the filehandle of
the file system "/a/b/c/d". In previous versions of the NFS
protocol, the server would respond with the directory "/a/b/d/d"
within the file system "/a/b".
The NFS client will be able to determine if it crosses a server mount
point by a change in the value of the "fsid" attribute.
7.8. Security Policy and Namespace Presentation
The application of the server's security policy needs to be carefully
considered by the implementor. One may choose to limit the
viewability of portions of the pseudo file system based on the
server's perception of the client's ability to authenticate itself
properly. However with the support of multiple security mechanisms
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and the ability to negotiate the appropriate use of these mechanisms,
the server is unable to properly determine if a client will be able
to authenticate itself. If, based on its policies, the server
chooses to limit the contents of the pseudo file system, the server
may effectively hide file systems from a client that may otherwise
have legitimate access.
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8. File Locking
Integrating locking into the NFS protocol necessarily causes it to be
state-full. With the invasive nature of "share" file locks it
becomes substantially more dependent on state than the traditional
combination of NFS and NLM [XNFS]. There are three components to
making this state manageable:
o Clear division between client and server
o Ability to reliably detect inconsistency in state between client
and server
o Simple and robust recovery mechanisms
In this model, the server owns the state information. The client
communicates its view of this state to the server as needed. The
client is also able to detect inconsistent state before modifying a
file.
To support Win32 "share" locks it is necessary to atomically OPEN or
CREATE files. Having a separate share/unshare operation will not
allow correct implementation of the Win32 OpenFile API. In order to
correctly implement share semantics, the previous NFS protocol
mechanisms used when a file is opened or created (LOOKUP, CREATE,
ACCESS) need to be replaced. The NFS version 4 protocol has an OPEN
operation that subsumes the functionality of LOOKUP, CREATE, and
ACCESS. However, because many operations require a filehandle, the
traditional LOOKUP is preserved to map a file name to filehandle
without establishing state on the server. The policy of granting
access or modifying files is managed by the server based on the
client's state. It is believed that these mechanisms can implement
policy ranging from advisory only locking to full mandatory locking.
While ACCESS is just a subset of OPEN, the ACCESS operation is
maintained as a lighter weight mechanism.
8.1. Definitions
Lock The term "lock" will be used to refer to both record
(byte-range) locks as well as file (share) locks unless
specifically stated otherwise.
Client The term "client" is used to indicate the entity that
maintains a set of locks on behalf of one or more
applications. The client is responsible for crash or
failure recovery for those locks it manages. Multiple
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clients may share the same transport and multiple clients
may exist on the same network node.
Clientid A 64-bit quantity returned by a server that uniquely
corresponds to a client supplied Verifier and ID.
Lease An interval of time defined by the server for which the
client is irrevokeably granted a lock. At the end of a
lease period the lock may be revoked if the lease has not
been extended. The lock must be revoked if a conflicting
lock has been granted after the lease interval. All leases
granted by a server have the same fixed interval.
Stateid A 64-bit quantity returned by a server that uniquely
defines the locking state granted by the server for a
specific lock owner for a specific file. A stateid
composed of all bits 0 or all bits 1 has special meaning
and are reserved values.
Verifier A 32-bit quantity generated by the client that the server
can use to determine if the client has restarted and lost
all previous lock state.
8.2. Locking
It is assumed that manipulating a lock is rare when compared to READ
and WRITE operations. It is also assumed that crashes and network
partitions are relatively rare. Therefore it is important that the
READ and WRITE operations have a light weight mechanism to indicate
if they possess a held lock. A lock request contains the heavy
weight information required to establish a lock and uniquely define
the lock owner.
The following sections describe the transition from the heavy weight
information to the eventual stateid used for most client and server
locking and lease interactions.
8.2.1. Client ID
For each LOCK request, the client must identify itself to the server.
This is done in such a way as to allow for correct lock
identification and crash recovery. Client identification is
accomplished with two values.
o A verifier that is used to detect client reboots.
o A variable length opaque array to uniquely define a client.
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For an operating system this may be a fully qualified host
name or IP address. For a user level NFS client it may
additionally contain a process id or other unique sequence.
The data structure for the Client ID would then appear as:
struct nfs_client_id {
opaque verifier[4];
opaque id<>;
}
It is possible through the mis-configuration of a client or the
existence of a rogue client that two clients end up using the same
nfs_client_id. This situation is avoided by "negotiating" the
nfs_client_id between client and server with the use of the
SETCLIENTID and SETCLIENTID_CONFIRM operations. The following
describes the two scenarios of negotiation.
1 Client has never connected to the server
In this case the client generates an nfs_client_id and
unless another client has the same nfs_client_id.id field,
the server accepts the request. The server also records the
principal (or principal to uid mapping) from the credential
in the RPC request that contains the nfs_client_id
negotiation request (SETCLIENTID operation).
Two clients might still use the same nfs_client_id.id due
to perhaps configuration error. For example, a High
Availability configuration where the nfs_client_id.id is
derived from the ethernet controller address and both
systems have the same address. In this case, the result is
a switched union that returns in addition to
NFS4ERR_CLID_INUSE, the network address (the rpcbind netid
and universal address) of the client that is using the id.
2 Client is re-connecting to the server after a client reboot
In this case, the client still generates an nfs_client_id
but the nfs_client_id.id field will be the same as the
nfs_client_id.id generated prior to reboot. If the server
finds that the principal/uid is equal to the previously
"registered" nfs_client_id.id, then locks associated with
the old nfs_client_id are immediately released. If the
principal/uid is not equal, then this is a rogue client and
the request is returned in error. For more discussion of
crash recovery semantics, see the section on "Crash
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Recovery"
To mitigate retransmission of the SETCLIENTID operation,
the client has the choice to request of the server a
confirmation step. In the SETCLIENTID request, the client
would specify that it wants to confirm the clientid. The
server would return a confirmation cookie that is then
returned to the server in the SETCLIENTID_CONFIRM
operation. Once the server receives the confirmation from
the client, the locking state for the client is released.
In both cases, upon success, NFS4_OK is returned. To help reduce the
amount of data transferred on OPEN and LOCK, the server will also
return a unique 64-bit clientid value that is a shorthand reference
to the nfs_client_id values presented by the client. From this point
forward, the client will use the clientid to refer to itself.
The clientid assigned by the server should be chosen so that it will
not conflict with a clientid previously assigned by the server. This
applies across server restarts or reboots. When a clientid is
presented to a server and that clientid is not recognized, as would
happen after a server reboot, the server will reject the request with
the error NFS4ERR_STALE_CLIENTID. When this happens, the client must
obtain a new clientid by use of the SETCLIENTID operation and then
proceed to any other necessary recovery for the server reboot case
(See the section "Server Failure and Recovery").
The client must also employ the SETCLIENTID operation when it
receives a NFS4ERR_STALE_STATEID error using a stateid derived from
its current clientid since this also indicates a server reboot which
has invalidated the existing clientid (see the next section
"nfs_lockowner and stateid Definition" for details).
8.2.2. nfs_lockowner and stateid Definition
When requesting a lock, the client must present to the server the
clientid and an identifier for the owner of the requested lock.
These two fields are referred to as the nfs_lockowner and the
definition of those fields are:
o A clientid returned by the server as part of the clients use of
the SETCLIENTID operation.
o A variable length opaque array used to uniquely define the owner
of a lock managed by the client.
This may be a thread id, process id, or other unique value.
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When the server grants the lock it responds with a unique 64-bit
stateid. The stateid is used as a shorthand reference to the
nfs_lockowner, since the server will be maintaining the
correspondence between them.
The server is free to form the stateid in any manner that it chooses
as long as it is able to recognize invalid and out-of-date stateids.
This requirement includes those stateids generated by earlier
instances of the server. From this, the client can be properly
notified of a server restart. This notification will occur when the
client presents a stateid to the server from a previous
instantiation.
The server must be able to distinguish the following situations and
return the error as specified:
o The stateid was generated by an earlier server instance (i.e.
before a server reboot). The error NFS4ERR_STALE_STATEID should
be returned.
o The stateid was generated by the current server instance but the
stateid no longer designates the current locking state for the
lockowner-file pair in question (i.e. one or more locking
operations has occurred). The error NFS4ERR_OLD_STATEID should
be returned.
This error condition will occur when the client issues a locking
request which changes a stateid while an I/O request that uses
that stateid is outstanding.
o The stateid was generated by the current server instance but the
stateid does not designate a locking state for any active
lockowner-file pair. The error NFS4ERR_BAD_STATEID should be
returned.
This error condition will occur when there has been a logic
error on the part of the client or server. This should not
happen.
One mechanism that may be used to satisfy these requirements is for
the server to divide stateids into three fields:
o A server verifier which uniquely designates a particular server
instantiation.
o An index into a table of locking-state structures.
o A sequence value which is incremented for each stateid that is
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associated with the same index into the locking-state table.
By matching the incoming stateid and its field values with the state
held at the server, the server is able to easily determine if a
stateid is valid for its current instantiation and state. If the
stateid is not valid, the appropriate error can be supplied to the
client.
8.2.3. Use of the stateid
All READ and WRITE operations contain a stateid. If the
nfs_lockowner performs a READ or WRITE on a range of bytes within a
locked range, the stateid returned by the server must be used to
indicate the appropriate lock (record or share) is held. If no state
is established by the client, either record lock or share lock, a
stateid of all bits 0 is used. If no conflicting locks are held on
the file, the server may service the READ or WRITE operation. If a
conflict with an explicit lock occurs, an error is returned for the
operation (NFS4ERR_LOCKED). This allows "mandatory locking" to be
implemented.
A stateid of all bits 1 allows READ operations to bypass locking
checks at the server. However, WRITE operations with stateid with
bits all 1 do not bypass file locking requirements.
An explicit lock may not be granted while a READ or WRITE operation
with conflicting implicit locking is being performed.
The byte range of a lock is indivisible. A range may be locked or
unlocked between read and write but may not have subranges unlocked
or changed between read and write. These are the semantics provided
by the Win32 environment but only a subset of the semantics provided
by Unix environment. It is expected that Unix clients can more
easily simulate modifying subranges than Win32 servers adding this
feature.
8.2.4. Sequencing of Lock Requests
Locking is different than most NFS operations as it requires "at-
most-one" semantics that are not provided by ONCRPC. In the face of
retransmission or reordering, lock or unlock requests must have a
well defined and consistent behavior. To accomplish this, each lock
request contains a sequence number that is a consecutively increasing
integer. Different nfs_lockowners have different sequences. The
server maintains the last sequence number (L) received and the
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response that was returned.
If a request with a previous sequence number (r < L) is received, it
is rejected with the return of error NFS4ERR_BAD_SEQID. Given a
properly-functioning client, the response to (r) must have been
received before the last request (L) was sent. If a duplicate of
last request (r == L) is received, the stored response is returned.
If a request beyond the next sequence (r == L + 2) is received, it is
rejected with the return of error NFS4ERR_BAD_SEQID. Sequence
history is reinitialized whenever the client verifier changes.
8.3. Blocking Locks
Some clients require the support of blocking locks. The NFS version
4 protocol must not rely on a callback mechanism and therefore is
unable to notify a client when a lock has been granted. Clients have
no choice but to continually poll for the lock. This presents a
fairness problem. Two new lock types are added, READW and WRITEW,
and are used to indicate to the server that the client is requesting
a blocking lock. The server should maintain an ordered list of
pending blocking locks. When the conflicting lock is released, the
server may wait the lease period for the first client to re-request
the lock. After the lease period expires the next waiting client
request is allowed the lock. Clients are required to poll at an
interval sufficiently small that it is likely to acquire the lock in
a timely manner. The server is not required to maintain a list of
pending blocked locks as it is used to increase fairness and not
correct operation. Because of the unordered nature of crash
recovery, storing of lock state to stable storage would be required
to guarantee ordered granting of blocking locks.
8.4. Lease Renewal
The purpose of a lease is to allow a server to remove stale locks
that are held by a client that has crashed or is otherwise
unreachable. It is not a mechanism for cache consistency and lease
renewals may not be denied if the lease interval has not expired.
The following events cause implicit renewal of all of the leases for
a given client (i.e. all those sharing a given clientid). Each of
these is a positive indication that the client is still active and
that the associated state held at the server, for the client, is
still valid.
o An OPEN with a valid clientid.
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o Any operation made with a valid stateid (CLOSE, DELEGRETURN,
LOCK, LOCKU, OPEN, OPEN_CONFIRM, READ, RENEW, SETATTR, WRITE).
This does not include the special stateids of all bits 0 or all
bits 1.
Note that if the client had restarted or rebooted, the
client would not be making these requests without issuing
the SETCLIENTID operation. The use of the SETCLIENTID (and
optional SETCLIENTID_CONFIRM) operation(s) notifies the
server to drop the locking state associated with the
client.
If the server has rebooted, the stateids
(NFS4ERR_STALE_STATEID error) or the clientid
(NFS4ERR_STALE_CLIENTID error) will not be valid hence
preventing spurious renewals.
This approach allows for low overhead lease renewal which scales
well. In the typical case no extra RPC calls are required for lease
renewal and in the worst case one RPC is required every lease period
(i.e. a RENEW operation). The number of locks held by the client is
not a factor since all state for the client is involved with the
lease renewal action.
Since all operations that create a new lease also renew existing
leases, the server must maintain a common lease expiration time for
all valid leases for a given client. This lease time can then be
easily updated upon implicit lease renewal actions.
8.5. Crash Recovery
The important requirement in crash recovery is that both the client
and the server know when the other has failed. Additionally, it is
required that a client sees a consistent view of data across server
restarts or reboots. All READ and WRITE operations that may have
been queued within the client or network buffers must wait until the
client has successfully recovered the locks protecting the READ and
WRITE operations.
8.5.1. Client Failure and Recovery
In the event that a client fails, the server may recover the client's
locks when the associated leases have expired. Conflicting locks
from another client may only be granted after this lease expiration.
If the client is able to restart or reinitialize within the lease
period the client may be forced to wait the remainder of the lease
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period before obtaining new locks.
To minimize client delay upon restart, lock requests are associated
with an instance of the client by a client supplied verifier. This
verifier is part of the initial SETCLIENTID call made by the client.
The server returns a clientid as a result of the SETCLIENTID
operation. The clientid in combination with an opaque owner field is
then used by the client to identify the lock owner.
Since the verifier will be changed by the client upon each
initialization, the server can compare a new verifier to the verifier
associated with currently held locks and determine that they do not
match. This signifies the client's new instantiation and subsequent
loss of locking state. As a result, the server is free to release
all locks held which are associated with the old clientid which was
derived from the old verifier.
For secure environments, a change in the verifier must only cause the
release of locks associated with the authenticated requester. This
is required to prevent a rogue entity from freeing otherwise valid
locks.
Note that the verifier must have the same uniqueness properties of
the verify for the COMMIT operation.
8.5.2. Server Failure and Recovery
If the server loses locking state (usually as a result of a restart
or reboot), it must allow clients time to discover this fact and re-
establish the lost locking state. The client must be able to re-
establish the locking state without having the server deny valid
requests because the server has granted conflicting access to another
client. Likewise, if there is the possibility that clients have not
yet re-established their locking state for a file, the server must
disallow READ and WRITE operations for that file. The duration of
this recovery period is equal to the duration of the lease period.
A client can determine that server failure (and thus loss of locking
state) has occurred, when it receives one of two errors. The
NFS4ERR_STALE_STATEID error indicates a stateid invalidated by a
reboot or restart. The NFS4ERR_STALE_CLIENTID error indicates a
clientid invalidated by reboot or restart. When either of these are
received, the client must establish a new clientid (See the section
"Client ID") and re-establish the locking state as discussed below.
The period of special handling of locking and READs and WRITEs, equal
in duration to the lease period, is referred to as the "grace
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period". During the grace period, clients recover locks and the
associated state by reclaim-type locking requests (i.e. LOCK requests
with reclaim set to true and OPEN operations with a claim type of
CLAIM_PREVIOUS). During the grace period, the server must reject
READ and WRITE operations and non-reclaim locking requests (i.e.
other LOCK and OPEN operations) with an error of NFS4ERR_GRACE.
If the server can reliably determine that granting a non-reclaim
request will not conflict with reclamation of locks by other clients,
the NFS4ERR_GRACE error does not have to be returned and the non-
reclaim client request can be serviced. For the server to be able to
service READ and WRITE operations during the grace period, it must
again be able to guarantee that no possible conflict could arise
between an impending reclaim locking request and the READ or WRITE
operation. If the server is unable to offer that guarantee, the
NFS4ERR_GRACE error must be returned to the client.
For a server to provide simple, valid handling during the grace
period, the easiest method is to simply reject all non-reclaim
locking requests and READ and WRITE operations by returning the
NFS4ERR_GRACE error. However, a server may keep information about
granted locks in stable storage. With this information, the server
could determine if a regular lock or READ or WRITE operation can be
safely processed.
For example, if a count of locks on a given file is available in
stable storage, the server can track reclaimed locks for the file and
when all reclaims have been processed, non-reclaim locking requests
may be processed. This way the server can ensure that non-reclaim
locking requests will not conflict with potential reclaim requests.
With respect to I/O requests if the server is able to determine that
there are no outstanding reclaim requests for a file by information
from stable storage of another similar mechanism, the processing of
I/O requests could proceed normally for the file.
To reiterate, for the server that allows non-reclaim lock and I/O
requests to be processed during the grace period, it MUST determine
that no lock subsequently reclaimed will be rejected and that no lock
subsequently reclaimed would have prevented any I/O operation
processed during the grace period.
Clients should be prepared for the return of NFS4ERR_GRACE errors for
non-reclaim lock and I/O requests. In this case the client should
employ a backoff and retry mechanism for the request. Timeout
periods should be chosen to avoid overwhelming a server. The client
must account for the server that is able to perform I/O and non-
reclaim locking requests within the grace period as well as those
that can not.
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A reclaim-type locking request outside the server's grace period can
only succeed if the server can guarantee that no conflicting lock or
I/O request has been granted since reboot or restart.
8.5.3. Network Partitions and Recovery
If the duration of a network partition is greater than the lease
period provided by the server, the server will have not received a
lease renewal from the client. If this occurs, the server may free
all locks held for the client. As a result, all stateids held by the
client will become invalid or stale. Once the client is able to
reach the server after such a network partition, all I/O submitted by
the client with the now invalid stateids will fail with the server
returning the error NFS4ERR_EXPIRED. Once this error is received,
the client will suitably notify the application that held the lock.
As a courtesy to the client or optimization, the server may continue
to hold locks on behalf of a client for which recent communication
has extended beyond the lease period. If the server receives a lock
or I/O request that conflicts with one of these courtesy locks, the
server must free the courtesy lock and grant the new request.
In the event of a network partition with a duration extending beyond
the expiration of a client's leases, the server MUST employ a method
of recording this fact in its stable storage. Conflicting locks
requests from another client may be serviced after the lease
expiration. There are various scenarios involving server failure
after such an event that require the storage of these lease
expirations or network partitions. One scenario is as follows:
A client holds a lock at the server and encounters a
network partition and is unable to renew the associated
lease. A second client obtains a conflicting lock and then
frees the lock. After the unlock request by the second
client, the server reboots or reinitializes. Once the
server recovers, the network partition heals and the
original client attempts to reclaim the original lock.
In this scenario and without any state information, the server will
allow the reclaim and the client will be in an inconsistent state
because the server or the client has no knowledge of the conflicting
lock.
The server may choose to store this lease expiration or network
partitioning state in a way that will only identify the client as a
whole. Note that this may potentially lead to lock reclaims being
denied unnecessarily because of a mix of conflicting and non-
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conflicting locks. The server may also choose to store information
about each lock that has an expired lease with an associated
conflicting lock. The choice of the amount and type of state
information that is stored is left to the implementor. In any case,
the server must have enough state information to enable correct
recovery from multiple partitions and multiple server failures.
8.6. Server Revocation of Locks
At any point, the server can revoke locks held by a client and the
client must be prepared for this event. When the client detects that
its locks have been or may have been revoked, the client is
responsible for validating the state information between itself and
the server. Validating locking state for the client means that it
must verify or reclaim state for each lock currently held.
The first instance of lock revocation is upon server reboot or re-
initialization. In this instance the client will receive an error or
NFS4ERR_GRACE and the client will proceed with normal crash recovery
as described in the previous section.
The second lock revocation event can occur as a result of
administrative intervention within the lease period. While this is
considered a rare event, it is possible that the server's
administrator has decided to release or revoke a particular lock held
by the client. As a result of revocation, the client will receive an
error of NFS4ERR_EXPIRED and the error is received within the lease
period for the lock. In this instance the client may assume that
only the nfs_lockowner's locks have been lost. The client notifies
the lock holder appropriately. The client may not assume the lease
period has been renewed as a result of failed operation.
The third lock revocation event is the inability to renew the lease
period. While this is considered a rare or unusual event, the client
must be prepared to recover. Both the server and client will be able
to detect the failure to renew the lease and are capable of
recovering without data corruption. For the server, it tracks the
last renewal event serviced for the client and knows when the lease
will expire. Similarly, the client must track operations which will
renew the lease period. Using the time that each such request was
sent and the time that the corresponding reply was received, the
client should bound the time that the corresponding renewal could
have occurred on the server and thus determine if it is possible that
a lease period expiration could have occurred.
When the client determines the lease period may have expired, the
client must mark all locks held for the associated lease as
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"unvalidated". This means the client has been unable to re-establish
or confirm the appropriate lock state with the server. As described
in the previous section on crash recovery, there are scenarios in
which the server may grant conflicting locks after the lease period
has expired for a client. When it is possible that the lease period
has expired, the client must validate each lock currently held to
ensure that a conflicting lock has not been granted. The client may
accomplish this task by issuing an I/O request, either a pending I/O
or a zero-length read, specifying the stateid associated with the
lock in question. If the response to the request is success, the
client has validated all of the locks governed by that stateid and
re-established the appropriate state between itself and the server.
If the I/O request is not successful, then one or more of the locks
associated with the stateid was revoked by the server and the client
must notify the owner.
8.7. Share Reservations
A share reservation is a mechanism to control access to a file. It
is a separate and independent mechanism from record locking. When a
client opens a file, it issues an OPEN operation to the server
specifying the type of access required (READ, WRITE, or BOTH) and the
type of access to deny others (deny NONE, READ, WRITE, or BOTH). If
the OPEN fails the client will fail the applications open request.
Pseudo-code definition of the semantics:
if ((request.access & file_state.deny)) ||
(request.deny & file_state.access))
return (NFS4ERR_DENIED)
8.8. OPEN/CLOSE Operations
To provide correct share semantics, a client MUST use the OPEN
operation to obtain the initial filehandle and indicate the desired
access and what if any access to deny. Even if the client intends to
use a stateid of all 0's or all 1's, it must still obtain the
filehandle for the regular file with the OPEN operation so the
appropriate share semantics can be applied. For clients that do not
have a deny mode built into their open programming interfaces, deny
equal to NONE should be used.
The OPEN operation with the CREATE flag, also subsumes the CREATE
operation for regular files as used in previous versions of the NFS
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protocol. This allows a create with a share to be done atomicly.
The CLOSE operation removes all share locks held by the nfs_lockowner
on that file. If record locks are held, the client SHOULD release
all locks before issuing a CLOSE. The server MAY free all
outstanding locks on CLOSE but some servers may not support the CLOSE
of a file that still has record locks held. The server MUST return
failure if any locks would exist after the CLOSE.
The LOOKUP operation is preserved and will return a filehandle
without establishing any lock state on the server. Without a valid
stateid, the server will assume the client has the least access. For
example, a file opened with deny READ/WRITE cannot be accessed using
a filehandle obtained through LOOKUP because it would not have a
valid stateid (i.e. using a stateid of all bits 0 or all bits 1).
8.9. Short and Long Leases
When determining the time period for the server lease, the usual
lease tradeoffs apply. Short leases are good for fast server
recovery at a cost of increased RENEW or READ (with zero length)
requests. Longer leases are certainly kinder and gentler to large
internet servers trying to handle a very large numbers of clients.
The number of RENEW requests drop in direct proportion to the lease
time. The disadvantages of long leases are slower recovery after
server failure (server must wait for leases to expire and grace
period before granting new lock requests) and increased file
contention (if client fails to transmit an unlock request then server
must wait for lease expiration before granting new locks).
Long leases are usable if the server is able to store lease state in
non-volatile memory. Upon recovery, the server can reconstruct the
lease state from its non-volatile memory and continue operation with
its clients and therefore long leases are not an issue.
8.10. Clocks and Calculating Lease Expiration
To avoid the need for synchronized clocks, lease times are granted by
the server as a time delta. However, there is a requirement that the
client and server clocks do not drift excessively over the duration
of the lock. There is also the issue of propagation delay across the
network which could easily be several hundred milliseconds as well as
the possibility that requests will be lost and need to be
retransmitted.
To take propagation delay into account, the client should subtract it
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from lease times (e.g. if the client estimates the one-way
propagation delay as 200 msec, then it can assume that the lease is
already 200 msec old when it gets it). In addition, it will take
another 200 msec to get a response back to the server. So the client
must send a lock renewal or write data back to the server 400 msec
before the lease would expire.
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9. Client-Side Caching
Client-side caching of data, of file attributes, and of file names is
essential to providing good performance with the NFS protocol.
Providing distributed cache coherence is a difficult problem and
previous versions of the NFS protocol have not attempted it.
Instead, several NFS client implementation techniques have been used
to reduce the problems that a lack of coherence poses for users.
These techniques have not been clearly defined by earlier protocol
specifications and it is often unclear what is valid or invalid
client behavior.
The NFS version 4 protocol uses many techniques similar to those that
have been used in previous protocol versions. The NFS version 4
protocol does not provide distributed cache coherence. However, it
defines a more limited set of caching guarantees to allow locks and
share reservations to be used without destructive interference from
client side caching.
In addition, the NFS version 4 protocol introduces a delegation
mechanism which allows many decisions normally made by the server to
be made locally by clients. This mechanism provides efficient
support of the common cases where sharing is infrequent or where
sharing is read-only.
9.1. Performance Challenges for Client-Side Caching
Caching techniques used in previous versions of the NFS protocol have
been successful in providing good performance. However, several
scalability challenges can arise when those techniques are used with
very large numbers of clients. This is particularly true when
clients are geographically distributed which classically increases
the latency for cache revalidation requests.
The previous versions of the NFS protocol repeat their file data
cache validation requests at the time the file is opened. This
behavior can have serious performance drawbacks. A common case is
one in which a file is only accessed by a single client. Therefore,
sharing is infrequent.
In this case, repeated reference to the server to find that no
conflicts exist is expensive. A better option with regards to
performance is to allow a client that repeatedly opens a file to do
so without reference to the server. This is done until potentially
conflicting operations from another client actually occur.
A similar situation arises in connection with file locking. Sending
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file lock and unlock requests to the server as well as the read and
write requests necessary to make data caching consistent with the
locking semantics (see the section "Data Caching and File Locking")
can severely limit performance. When locking is used to provide
protection against infrequent conflicts, a large penalty is incurred.
This penalty may discourage the use of file locking by applications.
The NFS version 4 protocol provides more aggressive caching
strategies with the following design goals:
o Compatibility with a large range of server semantics.
o Provide the same caching benefits as previous versions of the
NFS protocol when unable to provide the more aggressive model.
o Requirements for aggressive caching are organized so that a
large portion of the benefit can be obtained even when not all
of the requirements can be met.
The appropriate requirements for the server are discussed in later
sections in which specific forms of caching are covered. (see the
section "Open Delegation").
9.2. Delegation and Callbacks
Recallable delegation of server responsibilities for a file to a
client improves performance by avoiding repeated requests to the
server in the absence of inter-client conflict. With the use of a
"callback" RPC from server to client, a server recalls delegated
responsibilities when another client engages in sharing of a
delegated file.
A delegation is passed from the server to the client, specifying the
object of the delegation and the type of delegation. There are
different types of delegations but each type contains a stateid to be
used to represent the delegation when performing operations that
depend on the delegation. This stateid is similar to those
associated with locks and share reservations but differs in that the
stateid for a delegation is associated with a clientid and may be
used on behalf of all the nfs_lockowners for the given client. A
delegation is made to the client as a whole and not to any specific
process or thread of control within it.
Because callback RPCs may not work in all environments (due to
firewalls, for example), correct protocol operation does not depend
on them. Preliminary testing of callback functionality by means of a
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CB_NULL procedure determines whether callbacks can be supported. The
CB_NULL procedure checks the continuity of the callback path. A
server makes a preliminary assessment of callback availability to a
given client and avoids delegating responsibilities until it has
determined that callbacks are supported. Because the granting of a
delegation is always conditional upon the absence of conflicting
access, clients must not assume that a delegation will be granted and
they must always be prepared for denial.
Once granted, a delegation behaves in most ways like a lock. There
is an associated lease that is subject to renewal together with all
of the other leases held by that client.
Unlike locks, an operation by a second client to a delegated file
will cause the server to recall a delegation through a callback.
On recall, the client holding the delegation must flush modified
state (such as modified data) to the server and return the
delegation. The conflicting request will not receive a response
until the recall is complete. The recall is considered complete when
the client returns the delegation or the server times out on the
recall and revokes the delegation as a result of the time out.
Following the resolution of the recall, the server has the
information necessary to grant or deny the second client's request.
At the time the client receives a delegation recall, it may have
substantial state that needs to be flushed to the server. Therefore,
the server should allow sufficient time for the recall RPC to
complete since it involves atypical actions. If the server is able
to determine that the client is diligently flushing state to the
server as a result of the recall, the server may extend the usual
time allowed for a recall. However, the time allowed for recall
completion should not be unbounded.
An example of this is when responsibility to mediate opens on a given
file is delegated to a client (see the section "Open Delegation").
The server will not know what opens are in effect on the client.
Without this knowledge the server will be unable to determine if the
access and deny state for the file allows any particular open until
the delegation for the file has been returned.
A client failure or a network partition can result in failure to
respond to a recall callback. In this case, the server will revoke
the delegation which in turn will render useless any modified state
still on the client.
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9.2.1. Delegation Recovery
There are three situations that delegation recovery must deal with:
o Client reboot or restart
o Server reboot or restart
o Network partition (full or callback-only)
In the event the client reboots or restarts, the failure to renew
leases will result in the revocation of record locks and share
reservations. Delegations, however, may treated a bit differently.
There will be situations in which delegations will need to be
reestablished after a client reboots or restarts. The reason for
this is the client may have file data stored locally and this data
was associated with the previously held delegations. The client will
need to reestablish the appropriate file state on the server.
To allow for this type of client recovery, the server may extend the
period for delegation recovery beyond the typical lease expiration
period. This implies that requests from other clients that conflict
with these delegations will need to wait. This behavior is
consistent with the normal recall process may take significant time
because of the client's need to flush state to the server. This
longer interval would increase the window for clients to reboot and
consult stable storage so that the delegations can be reclaimed. For
open delegations, such delegations are reclaimed using OPEN with a
claim type of CLAIM_DELEGATE_PREV. (see the sections on "Data
Caching and Revocation" and "Operation 18: OPEN" for discussion of
open delegation and the details of OPEN respectively).
When the server reboots or restarts, delegations are reclaimed (using
the OPEN operation with CLAIM_DELEGATE_PREV) in a similar fashion to
record locks and share reservations. However, there is a slight
semantic difference. In the normal case if the server decides that a
delegation should not be granted, it performs the requested action
(e.g. OPEN) without granting any delegation. For reclaim, the server
grants the delegation but a special designation is applied so that
the client treats the delegation as having been granted but recalled
by the server. Because of this, the client has the duty to write all
modified state to the server and then return the delegation. This
process of handling delegation reclaim reconciles three principles of
the NFS Version 4 protocol:
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o Upon reclaim, a client reporting resources assigned to it by an
earlier server instance must be granted those resources.
o The server has unquestionable authority to determine whether
delegations are to be granted and, once granted, whether they
are to be continued.
o The use of callbacks is not to be depended upon until the client
has proven its ability to receive them.
When a network partition occurs, delegations are subject to freeing
by the server when the lease renewal period expires. This is similar
to the behavior for locks and share reservations. For delegations,
however, the server may extend the period in which conflicting
requests are held off. Eventually the occurrence of a conflicting
request from another client will cause revocation of the delegation.
A loss of the callback path (e.g. by later network configuration
change) will have the same effect. A recall request will fail and
revocation of the delegation will result.
A client normally finds out about revocation of a delegation when it
uses a stateid associated with a delegation and receives the error
NFS4ERR_EXPIRED. It also may find out about delegation revocation
after a client reboot when it attempts to reclaim a delegation and
receives that same error. Note that in the case of a revoked write
open delegation, there are issues because data may have been modified
by the client whose delegation is revoked and separately by other
clients. See the section "Revocation Recovery for Write Open
Delegation" for a discussion of such issues. Note also that when
delegations are revoked, information about the revoked delegation
will be written by the server to stable storage (as described in the
section "Crash Recovery"). This is done to deal with the case in
which a server reboots after revoking a delegation but before the
client holding the revoked delegation is notified about the
revocation.
9.3. Data Caching
When applications share access to a set of files they need to be
implemented so as to take account of the possibility of conflicting
access by another application. This is true whether the applications
in question execute on different clients or reside on the same
client.
Share reservations and record locks are the facilities the NFS
version 4 protocol provides to allow applications to coordinate
access by providing mutual exclusion facilities. The NFS version 4
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protocol's data caching must be implemented such that it does not
invalidate the assumptions that those using these facilities depend
upon.
9.3.1. Data Caching and OPENs
In order to avoid invalidating the sharing assumptions that
applications rely on, NFS version 4 clients should not provide cached
data to applications or modify it on behalf of an application when it
would not be valid to obtain or modify that same data via a READ or
WRITE operation.
Furthermore, in the absence of open delegation (see the section "Open
Delegation") two additional rules apply. Note that these rules are
obeyed in practice by many NFS version 2 and version 3 clients.
o First, cached data present on a client must be revalidated after
doing an OPEN. This is to ensure that the data for the OPENed
file is still correctly reflected in the client's cache. This
validation must be done at least when the client's OPEN
operation includes DENY=WRITE or BOTH thus terminating a period
in which other clients may have had the opportunity to open the
file with WRITE access. Clients may choose to do the
revalidation more often (i.e. at OPENs specifying DENY=NONE) to
parallel the NFS version 3 protocol's practice for the benefit
of users assuming this degree of cache revalidation.
o Second, modified data must be flushed to the server before
closing a file OPENed for write. This is complementary to the
first rule. If the data is not flushed at CLOSE, the
revalidation done after client OPENs as file is unable to
achieve its purpose. The other aspect to flushing the data
before close is that the data must be committed to stable
storage before the CLOSE operation is requested by the client.
In the case of a server reboot or restart and a CLOSEd file, it
may not be possible to retransmit the data to be written to the
file. Hence, this requirement.
9.3.2. Data Caching and File Locking
For those applications that choose to use file locking instead of
share reservations to exclude inconsistent file access, there is an
analogous set of constraints that apply to client side data caching.
These rules are effective only if the file locking is used in a way
that matches in an equivalent way the actual READ and WRITE
operations executed. This is opposed to file locking that is based
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on pure convention. For example, it is possible to manipulate a 2
megabyte file by dividing the file into two 1 (one) megabyte regions
and protecting access to the two regions by file locks on bytes 0
(zero) and 1 (one). A lock for write on byte 0 (zero) of the file
would represent the right to do READ and WRITE operations on the
first region. A lock for write on byte 1 (one) of the file would
represent the right to do READ and WRITE operations on the second
region. As long as all applications manipulating the file obey this
convention, they will work on a local file system. However, they may
not work with the NFS version 4 protocol unless clients refrain from
data caching.
The rules for data caching in the file locking environment are:
o First, when a client obtains a file lock for a particular
region, the data cache corresponding to that region (if any
cache data exists) must be revalidated. If the change attribute
indicates that the file may have been updated since the cached
data was obtained, the client must flush or invalidate the
cached data for the newly locked region. A client might choose
to invalidate all of non-modified cached data that it has for
the file but the only requirement for correct operation is to
invalidate all of the data in the newly locked region.
o Second, before releasing a write lock for a region, all modified
data for that region must be flushed to the server. The
modified data must also be written to stable storage.
Note that flushing data to the server and the invalidation of cached
data must reflect the actual byte ranges locked or unlocked.
Rounding these up or down to reflect client cache block boundaries
will cause problems if not carefully done. For example, writing a
modified block when only half of that block is within an area being
unlocked may cause invalid modification to the region outside the
unlocked area. This, in turn, may be part of a region locked by
another client. Clients can avoid this situation by synchronously
performing portions of write operations that overlap that portion
(initial or final) that is not a full block. Similarly, invalidating
a locked area which is not an integral number of full buffer blocks
would require the client to read one or two partial blocks from the
server if the revalidation procedure shows that the data which the
client possesses may not be valid.
The data that is written to the server as a pre-requisite of the
unlocking of a region must be written to stable storage. The client
may accomplish this with either synchronous writes or following
asynchronous writes by the COMMIT operation. This is required
because retransmission of the modified data after a server reboot
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might conflict with a lock held by another client.
A client implementation may choose to accommodate applications which
use record locking in non-standard ways (e.g. using a record lock as
a global semaphore) by flushing to the server more data upon an LOCKU
than is covered by the locked range. This may include modified data
within files other than the one for which the unlocks are being done.
In such cases, the client must not interfere with applications whose
READs and WRITEs are being done only within the bounds of record
locks which the application holds. For example, an application locks
a single byte of a file and proceeds to write that single byte. A
client that chose to handle a LOCKU by flushing all modified data to
the server could validly write that single byte in response to an
unrelated unlock. However, it would not be valid to write the entire
block in which that single written byte was located since it includes
an area that is not locked and might be locked by another client.
Client implementations can avoid this problem by dividing files with
modified data into those for which all modifications are done to
areas covered by an appropriate record lock and those for which there
are modifications not covered by a record lock. Any writes done for
the former class of files must not include areas not locked and thus
not modified on the client.
9.3.3. Data Caching and Mandatory File Locking
Client side data caching needs to respect mandatory file locking when
it is in effect. The presence of mandatory file locking for a given
file is indicated in the result flags for an OPEN. When mandatory
locking is in effect for a file, the client must check for an
appropriate file lock for data being read or written. If a lock
exists for the range being read or written, the client may satisfy
the request using the client's validated cache. If an appropriate
file lock is not held for the range of the read or write, the read or
write request must not be satisfied by the client's cache and the
request sent to the server for processing. When a read or write
request partially overlaps a locked region, the request should be
subdivided into multiple pieces with each region (locked or not)
treated appropriately.
9.3.4. Data Caching and File Identity
When clients cache data, the file data needs to organized according
to the file system object to which the data belongs. For NFS version
3 clients, the typical practice has been to assume for the purpose of
caching that distinct filehandles represent distinct file system
objects. The client then has the choice to organize and maintain the
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data cache on this basis.
In the NFS version 4 protocol, there is now the possibility to have
significant deviations from a "one filehandle per object" model
because a filehandle may be constructed on the basis of the object's
pathname. Therefore, clients need a reliable method to determine if
two filehandles designate the same file system object. If clients
simply assume that all distinct filehandles denote distinct objects
and proceed to do data caching on this basis, caching inconsistencies
would arise between the distinct client side objects which mapped to
the same server side object.
By providing a method to differentiate filehandles, the NFS version 4
protocol alleviates a potential functional digression in comparison
to the NFS version 3 protocol. Without this method, caching
inconsistencies within the same client could occur and this has not
been present in previous versions of the NFS protocol. Note that it
is possible to have such inconsistencies with applications executing
on multiple clients but that is not the issue being address here.
For the purposes of data caching, the following steps allow an NFS
version 4 client to determine whether two distinct filehandles denote
the same server side object:
o If GETATTR directed to two filehandles have different values of
the fsid attribute, then the filehandles represent distinct
objects.
o If GETATTR for any file with an fsid that matches the fsid of
the two filehandles in question returns a unique_handles
attribute with a value of TRUE, then the two objects are
distinct.
o If GETATTR directed to the two filehandles does not return the
fileid attribute for one or both of the handles, then the it
cannot be determined whether the two objects are the same.
Therefore, operations which depend on that knowledge (e.g.
client side data caching) cannot be done reliably.
o If GETATTR directed to the two filehandles returns different
values for the fileid attribute, then they are distinct objects.
o Otherwise they are the same object.
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9.4. Open Delegation
When a file is being OPENed, the server may delegate further handling
of opens and closes for that file to the opening client. Any such
delegation is recallable, since the circumstances that allowed for
the delegation are subject to change. In particular, the server may
receive a conflicting OPEN from another client, the server must
recall the delegation before deciding whether the OPEN from the other
client may be granted. Granting a delegation request is up to the
server and it may deny all such requests. The following is a typical
set of conditions that servers might use in deciding whether OPEN
should be delegated:
o The client must be able to respond to the server's callback
requests. The server will use the CB_NULL procedure for a test
of callback ability.
o The client must have responded properly to previous recalls.
o There must be no current open conflicting with the requested
delegation.
o There should be no current delegation that conflicts with the
delegation being requested.
o The probability of future conflicting open requests should be
low based on the recent history of the file.
o The existence of any server specific semantics of OPEN/CLOSE
that would make the required handling incompatible with the
prescribed handling that the delegated client would apply (see
below).
There are two types of open delegations, read and write. A read open
delegation allows a client to handle, on its own, requests to open a
file for reading that do not deny read access to others. Multiple
read open delegations may be outstanding simultaneously and do not
conflict. A write open delegation allows the client to handle, on
its own, all opens. Only one write open delegation may exist for a
given file at a given time and it is inconsistent with any read open
delegations.
When a client has a read open delegation, it may not make any changes
to the contents or attributes of the file but it is assured that no
other client may do so. When a client has a write open delegation,
it may modify the file data since no other client will be accessing
the file's data. The client holding a write delegation may only
affect file attributes which are intimately connected with the file
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data: object_size, time_modify.
When a client has an open delegation, it does not send OPENs or
CLOSEs to the server but updates the appropriate status internally.
For a read open delegation, opens that cannot be handled locally
(opens for write or that deny read access) must be sent to the
server.
When an open delegation is requested and granted, the response to the
OPEN contains an open delegation structure which specifies the
following:
o the type of delegation (read or write)
o space limitation information to control flushing of data on
close (write open delegation only, see the section "Open
Delegation and Data Caching")
o an nfsace4 specifying read and write permissions
o a stateid to represent the delegation for READ and WRITE
The stateid is separate and distinct from the stateid for the OPEN
proper. The standard stateid, unlike the delegation stateid, is
associated with a particular nfs_lockowner and will continue to be
valid after the delegation is recalled and the file remains open.
When a request internal to the client is made to open a file and open
delegation is in effect, it will be accepted or rejected solely on
the basis of the following conditions. Any requirement for other
checks to be made by the delegate should result in open delegation
being denied so that the checks can be made by the server itself.
o The access and deny bits for the request and the file as
described in the section "Share Reservations".
o The read and write permissions as determined below.
The nfsace4 passed with delegation can be used to avoid frequent
ACCESS calls. The permission check should be as follows:
o If the nfsace4 indicates that the open may be done, then it
should be granted without reference to the server.
o If the nfsace4 indicates that the open may not be done, then an
ACCESS request must be sent to the server to obtain the
definitive answer.
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The server may return an nfsace4 that is more restrictive than the
actual ACL of the file. This includes an nfsace4 that specifies
denial of all access. Note that some common practices such as
mapping the traditional user "root" to the user "nobody" may make it
incorrect to return the actual ACL of the file in the delegation
response.
The use of delegation together with various other forms of caching
creates the possibility that no server authentication will ever be
performed for a given user since all of the user's requests might be
satisfied locally. Where the client is depending on the server for
authentication, the client should be sure authentication occurs for
each user by use of the ACCESS operation. This should be the case
even if an ACCESS operation would not required otherwise. As
mentioned before, the server may enforce frequent authentication by
returning an nfsace4 denying all access with every open delegation.
9.4.1. Open Delegation and Data Caching
OPEN delegation allows much of the message overhead associated with
the opening and closing files to be eliminated. An open when an open
delegation is in effect does not require that a validation message be
sent to the server. The continued endurance of the "read open
delegation" provides a guarantee that no OPEN for write and thus no
write has occurred. Similarly, when closing a file opened for write
and if write open delegation is in effect, the data written does not
have to be flushed to the server until the open delegation is
recalled. The continued endurance of the open delegation provides a
guarantee that no open and thus no read or write has been done by
another client.
For the purposes of open delegation, READs and WRITEs done without an
OPEN are treated as the functional equivalent of a corresponding type
of OPEN. This refers to the READs and WRITEs that use the special
stateids consisting of all zero bits or all one bits. Therefore,
READs or WRITEs with a special stateid done by another client will
force the server to recall a write open delegation. A WRITE with a
special stateid done by another client will force a recall of read
open delegations.
With delegations, a client is able to avoid writing data to the
server when the CLOSE of a file is serviced. The CLOSE operation is
the usual point at which the client is notified of a lack of stable
storage for the modified file data generated by the application. At
the CLOSE, file data is written to the server and through normal
accounting the server is able to determine if the available file
system space for the data has been exceeded (i.e. server returns
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NFS4ERR_NOSPC or NFS4ERR_DQUOT). This accounting includes quotas.
The introduction of delegations requires that a alternative method be
in place for the same type of communication to occur between client
and server.
In the delegation response, the server provides either the limit of
the size of the file or the number of modified blocks and associated
block size. The server must ensure that the client will be able to
flush data to the server of a size equal to that provided in the
original delegation. The server must make this assurance for all
outstanding delegations. Therefore, the server must be careful in
its management of available space for new or modified data taking
into account available file system space and any applicable quotas.
The server can recall delegations as a result of managing the
available file system space. The client should abide by the server's
state space limits for delegations. If the client exceeds the stated
limits for the delegation, the server's behavior is undefined.
Based on server conditions, quotas or available file system space,
the server my grant write open delegations with very restrictive
space limitations. The limitations may be defined in a way that will
always force modified data to be flushed to the server on close.
With respect to authentication, flushing modified data to the server
after a CLOSE has occurred may be problematic. For example, the user
of the application may have logged off of the client and unexpired
authentication credentials may not be present. In this case, the
client may need to take special care to ensure that local unexpired
credentials will in fact be available. This may be accomplished by
tracking the expiration time of credentials and flushing data well in
advance of their expiration or by making private copies of
credentials to assure their availability when needed.
9.4.2. Open Delegation and File Locks
When a client holds a write open delegation, lock operations are
performed locally. This includes those required for mandatory file
locking. This can be done since the delegation implies that there
can be no conflicting locks. Similarly, all of the revalidations
that would normally be associated with obtaining locks and the
flushing of data associated with the releasing of locks need not be
done.
9.4.3. Recall of Open Delegation
The following events necessitate recall of an open delegation:
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o Potentially conflicting OPEN request (or READ/WRITE done with
"special" stateid)
o SETATTR issued by another client
o REMOVE request for the file
o RENAME request for the file as either source or target of the
RENAME
Whether a RENAME of a directory in the path leading to the file
results in recall of an open delegation depends on the semantics of
the server file system. If that file system denies such RENAMEs when
a file is open, the recall must be performed to determine whether the
file in question is, in fact, open.
In addition to the situations above, the server may choose to recall
open delegations at any time if resource constraints make it
advisable to do so. Clients should always be prepared for the
possibility of recall.
The server needs to employ special handling for a GETATTR where the
target is a file that has a write open delegation in effect. In this
case, the client holding the delegation needs to be interrogated.
The server will use a CB_GETATTR callback, if the GETATTR attribute
bits include any of the attributes that a write open delegate may
modify (object_size, time_modify, change).
When a client receives a recall for an open delegation, it needs to
update state on the server before returning the delegation. These
same updates must be done whenever a client chooses to return a
delegation voluntarily. The following items of state need to be
dealt with:
o If the file associated with the delegation is no longer open and
no previous CLOSE operation has been sent to the server, a CLOSE
operation must be sent to the server.
o If file has other open references at the client, then OPEN
operations must be sent to the server. The appropriate stateids
will be provided by the server for subsequent use by the client
since the delegation stateid will not longer be valid. These
OPEN requests are done with the claim type of
CLAIM_DELEGATE_CUR. This will allow the presentation of the
delegation stateid so that the client can establish the
appropriate rights to perform the OPEN. (see the section
"Operation 18: OPEN" for details.)
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o If there are granted file locks, the corresponding LOCK
operations need to be performed. This applies to the write open
delegation case only.
o For a write open delegation at the time of recall if the file is
not open for write, all modified data for the file must be
flushed to the server. If the delegation had not existed, the
client would have done this data flush before the CLOSE
operation.
o With the write open delegation in place, it is possible that the
file was truncated during the duration of the delegation. For
example, the truncation could have occurred as a result of an
OPEN UNCHECKED with a object_size attribute value of zero.
Therefore, if a truncation of the file has occurred and this
operation has not been propagated to the server, the truncation
must occur before any modified data is written to the server.
o Any modified data for the file needs to be flushed to the the
server.
In the case of write open delegation, file locking imposes some
additional requirements. The flushing of any modified data in any
region for which a write lock was released while the write open
delegation was in effect is what is required to precisely maintain
the associated invariant. However, because the write open delegation
implies no other locking by other clients, a simpler implementation
is to flush all modified data for the file (as described just above)
if any write lock has been released while the write open delegation
was in effect.
9.4.4. Delegation Revocation
At the point a delegation is revoked, if there are associated opens
on the client, the applications holding these opens need to be
notified. This notification usually occurs by returning errors for
READ/WRITE operations or when a close is attempted for the open file.
If no opens exist for the file at the point the delegation is
revoked, then notification of the revocation is unnecessary.
However, if there is modified data present at the client for the
file, the user of the application should be notified. Unfortunately,
it may not be possible to notify the user since active applications
may not be present at the client. See the section "Revocation
Recovery for Write Open Delegation" for additional details.
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9.5. Data Caching and Revocation
When locks and delegations are revoked, the assumptions upon which
successful caching depend are no longer guaranteed. The owner of the
locks or share reservations which have been revoked needs to be
notified. This notification includes applications with a file open
that has a corresponding delegation which has been revoked. Cached
data associated with the revocation must be removed from the client.
In the case of modified data existing in the client's cache, that
data must be removed from the client without it being written to the
server.
Notification to a lock owner will in many cases consist of simply
returning an error on the next and all subsequent READs/WRITEs to the
open file or on the close. Where the methods available to a client
to make such notification impossible because errors for certain
operations may not be returned, more drastic action such as signals
or process termination may be appropriate. The justification for
this is that an invariant for which an application depends on may be
violated. Depending on how errors are typically treated for the
client operating environment, further levels of notification
including logging, console messages, and GUI pop-ups may be in
appropriate.
9.5.1. Revocation Recovery for Write Open Delegation
Revocation recovery for a write open delegation poses the special
issue of modified data in the client cache while the file is not
open. In this situation, any client which does not flush modified
data to the server on each close must ensure that the user receives
appropriate notification of the failure as a result of the
revocation. Since such situations may require human action to
correct problems, notification schemes in which the appropriate user
or administrator is notified may be necessary. Logging and console
messages are typical examples.
If there is modified data on the client, it must not be flushed
normally to the server. A client may attempt to provide a copy of
the file data as modified during the delegation under a different
name in the file system name space to ease recovery. Unless the
client can determine that the file has not modified by any other
client, this technique must be limited to situations in which a
client has a complete cached copy of the file in question. Use of
such a technique may be limited to files under a certain size or may
only be used when sufficient disk space is guaranteed to be available
within the target file system and when the client has sufficient
buffering resources to keep the cached copy available until it is
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properly stored to the target file system.
9.6. Attribute Caching
The attributes discussed in this section do not include named
attributes. Individual named attributes are analogous to files and
caching of the data for these needs to be handled just as data
caching is for ordinary files. Similarly, LOOKUP results from an
OPENATTR directory are to be cached on the same basis as any other
pathnames and similarly for directory contents.
Clients may cache file attributes obtained from the server and use
them to avoid subsequent GETATTR requests. Such caching is write
through in that modification to file attributes is always done by
means of requests to the server and should not be done locally and
cached. The exception to this are modifications to attributes that
are intimately connected with data caching. Therefore, extending a
file by writing data to the local data cache is reflected immediately
in the object_size as seen on the client without this change being
immediately reflected on the server. Normally such changes are not
propagated directly to the server but when the modified data is
flushed to the server, analogous attribute changes are made on the
server. When open delegation is in effect, the modified attributes
may be returned to the server in the response to a CB_RECALL call.
The result of local caching of attributes is that the attribute
caches maintained on individual clients will not be coherent. Changes
made in one order on the server may be seen in a different order on
one client and in a third order on a different client.
The typical file system application programming interfaces do not
provide means to atomically modify or interrogate attributes for
multiple files at the same time. The following rules provide an
environment where the potential incoherences mentioned above can be
reasonably managed. These rules are derived from the practice of
previous NFS protocols.
o All attributes for a given file (per-fsid attributes excepted)
are cached as a unit at the client so that no non-
serializability can arise within the context of a single file.
o An upper time boundary is maintained on how long a client cache
entry can be kept without being refreshed from the server.
o When operations are performed that change attributes at the
server, the updated attribute set is requested as part of the
containing RPC. This includes directory operations that update
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attributes indirectly. This is accomplished by following the
modifying operation with a GETATTR operation and then using the
results of the GETATTR to update the client's cached attributes.
Note that if the full set of attributes to be cached is requested by
READDIR, the results can be cached by the client on the same basis as
attributes obtained via GETATTR.
A client may validate its cached version of attributes for a file by
fetching only the change attribute and assuming that if the change
attribute has the same value as it did when the attributes were
cached, then no attributes have changed. The possible exception is
the attribute time_access.
9.7. Name Caching
The results of LOOKUP and READDIR operations may be cached to avoid
the cost of subsequent LOOKUP operations. Just as in the case of
attribute caching inconsistencies may arise among the various client
caches. To mitigate the effects of these inconsistencies and given
the context of typical file system APIs, the following rules should
be followed:
o The results of unsuccessful LOOKUPs should not be cached, unless
they are specifically reverified at the point of use.
o An upper time boundary is maintained on how long a client name
cache entry can be kept without verifying that the entry has not
been made invalid by a directory change operation performed by
another client.
When a client is not making changes to a directory for which there
exist name cache entries, the client needs to periodically fetch
attributes for that directory to ensure that it is not being
modified. After determining that no modification has occurred, the
expiration time for the associated name cache entries may be updated
to be the current time plus the name cache staleness bound.
When a client is making changes to a given directory, it needs to
determine whether there have been changes made to the directory by
other clients. It does this by using the change attribute as
reported before and after the directory operation in the associated
change_info4 value returned for the operation. The server is able to
communicate to the client whether the change_info4 data is provided
atomically with respect to the directory operation. If the change
values are provided atomically, the client is then able to compare
the pre-operation change value with the change value in the client's
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name cache. If the comparison indicates that the directory was
updated by another client, the name cache associated with the
modified directory is purged from the client. If the comparison
indicates no modification, the name cache can be updated on the
client to reflect the directory operation and the associated timeout
extended. The post-operation change value needs to be saved as the
basis for future change_info4 comparisons.
As demonstrated by the scenario above, name caching requires that the
client revalidate name cache data by inspecting the change attribute
of a directory at the point when the name cache item was cached.
This requires that the server update the change attribute for
directories when the contents of the corresponding directory is
modified. For a client to use the change_info4 information
appropriately and correctly, the server must report the pre and post
operation change attribute values atomically. When the server is
unable to report the before and after values atomically with respect
to the directory operation, the server must indicate that fact in the
change_info4 return value. When the information is not atomically
reported, the client should not assume that other clients have not
changed the directory.
9.8. Directory Caching
The results of READDIR operations may be used to avoid subsequent
READDIR operations. Just as in the cases of attribute and name
caching inconsistencies may arise among the various client caches.
To mitigate the effects of these inconsistencies and given the
context of typical file system APIs, the following rules should be
followed:
o Cached READDIR information for a directory which is not obtained
in a single READDIR operation must always be a consistent
snapshot of directory contents. This is determined by using a
GETATTR before the first READDIR and after the last of READDIR
that contributes to the cache.
o An upper time boundary is maintained to indicate the length of
time a directory cache entry is considered valid before the
client must revalidate the cached information.
The revalidation technique parallels that discussed in the case of
name caching. When the client is not changing the directory in
question, checking the change attribute of the directory with GETATTR
is adequate. The lifetime of the cache entry can be extended at
these checkpoints. When a client is modifying the directory, the
client needs to use the change_info4 data to determine whether there
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are other clients modifying the directory. If it is determined that
no other client modifications are occurring, the client may update
its directory cache to reflect its own changes.
As demonstrated previously, directory caching requires that the
client revalidate directory cache data by inspecting the change
attribute of a directory at the point when the directory was cached.
This requires that the server update the change attribute for
directories when the contents of the corresponding directory is
modified. For a client to use the change_info4 information
appropriately and correctly, the server must report the pre and post
operation change attribute values atomically. When the server is
unable to report the before and after values atomically with respect
to the directory operation, the server must indicate that fact in the
change_info4 return value. When the information is not atomically
reported, the client should not assume that other clients have not
changed the directory.
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10. Minor Versioning
To address the requirement of an NFS protocol that can evolve as the
need arises, the NFS version 4 protocol contains the rules and
framework to allow for future minor changes or versioning.
The base assumption with respect to minor versioning is that any
future accepted minor version must follow the IETF process and be
documented in a standards track RFC. Therefore, each minor version
number will correspond to an RFC. Minor version zero of the NFS
version 4 protocol is represented by this RFC. The COMPOUND
procedure will support the encoding of the minor version being
requested by the client.
The following items represent the basic rules for the development of
minor versions. Note that a future minor version may decide to
modify or add to the following rules as part of the minor version
definition.
1 Procedures are not added or deleted
To maintain the general RPC model, NFS version 4 minor versions
will not add or delete procedures from the NFS program.
2 Minor versions may add operations to the COMPOUND procedure.
The addition of operations to the COMPOUND procedure does not
affect the RPC model.
2.1 Minor versions may append attributes to GETATTR4args, bitmap4,
and GETATTR4res.
This allows for the expansion of the attribute model to allow
for future growth or adaptation.
2.2 Minor version X must append any new attributes after the last
documented attribute.
Since attribute results are specified as an opaque array of
per-attribute XDR encoded results, the complexity of adding new
attributes in the midst of the current definitions will be too
burdensome.
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3 Minor versions must not modify the structure of an existing
operation's arguments or results.
Again the complexity of handling multiple structure definitions
for a single operation is too burdensome. New operations should
be added instead of modifying existing structures for a minor
version.
This rule does not preclude the following adaptations in a minor
version.
o adding bits to flag fields such as new attributes to
GETATTR's bitmap4 data type
o adding bits to existing attributes like ACLs that have flag
words
o extending enumerated types (including NFS4ERR_*) with new
values
4 Minor versions may not modify the structure of existing
attributes.
5 Minor versions may not delete operations.
This prevents the potential reuse of a particular operation
"slot" in a future minor version.
6 Minor versions may not delete attributes.
7 Minor versions may not delete flag bits or enumeration values.
8 Minor versions may declare an operation as mandatory to NOT
implement.
Specifying an operation as "mandatory to not implement" is
equivalent to obsoleting an operation. For the client, it means
that the operation should not be sent to the server. For the
server, an NFS error can be returned as opposed to "dropping"
the request as an XDR decode error. This approach allows for
the obsolescence of an operation while maintaining its structure
so that a future minor version can reintroduce the operation.
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8.1 Minor versions may declare attributes mandatory to NOT
implement.
8.2 Minor versions may declare flag bits or enumeration values as
mandatory to NOT implement.
9 Minor versions may downgrade features from mandatory to
recommended, or recommended to optional.
10 Minor versions may upgrade features from optional to recommended
or recommended to mandatory.
11 A client and server that support minor version X must support
minor versions 0 (zero) through X-1 as well.
12 No new features may be introduced as mandatory in a minor
version.
This rule allows for the introduction of new functionality and
forces the use of implementation experience before designating a
feature as mandatory.
13 A client MUST NOT attempt to use a stateid, file handle, or
similar returned object from the COMPOUND procedure with minor
version X for another COMPOUND procedure with minor version Y,
where X != Y.
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11. Internationalization
The primary issue in which NFS needs to deal with
internationalization, or i18n, is with respect to file names and
other strings as used within the protocol. NFS' choice of string
representation must allow reasonable name/string access to clients
which use various languages. The UTF-8 encoding allows for this type
of access and this choice is explained in the following.
11.1. Universal Versus Local Character Sets
[RFC1345] describes a table of 16 bit characters for many different
languages (the bit encodings match Unicode, though of course RFC1345
is somewhat out of date with respect to current Unicode assignments).
Each character from each language has a unique 16 bit value in the 16
bit character set. Thus this table can be thought of as a universal
character set. [RFC1345] then talks about groupings of subsets of the
entire 16 bit character set into "Charset Tables". For example one
might take all the Greek characters from the 16 bit table (which are
are consecutively allocated), and normalize their offsets to a table
that fits in 7 bits. Thus it is determined that "lower case alpha"
is in the same position as "upper case a" in the US-ASCII table, and
"upper case alpha" is in the same position as "lower case a" in the
US-ASCII table.
These normalized subset character sets can be thought of as "local
character sets", suitable for an operating system locale.
Local character sets are not suitable for the NFS protocol. Consider
someone who creates a file with a name in a Swedish character set. If
someone else later goes to access the file with their locale set to
the Swedish language, then there are no problems. But if someone in
say the US-ASCII locale goes to access the file, the file name will
look very different, because the Swedish characters in the 7 bit
table will now be represented in US-ASCII characters on the display.
It would be preferable to give the US-ASCII user a way to display the
file name using Swedish glyphs. In order to do that, the NFS protocol
would have to include the locale with the file name on each operation
to create a file.
But then what of the situation when there is a path name on the
server like:
/component-1/component-2/component-3
Each component could have been created with a different locale. If
one issues CREATE with multi-component path name, and if some of the
leading components already exist, what is to be done with the
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existing components? Is the current locale attribute replaced with
the user's current one? These types of situations quickly become too
complex when there is an alternate solution.
If NFS V4 used a universal 16 bit or 32 bit character set (or a
encoding of a 16 bit or 32 bit character set into octets), then
server and client need not care if the locale of the user accessing
the file is different than the locale of the user who created the
file. The unique 16 bit or 32 bit encoding of the character allows
for determination of what language the character is from and also how
to display that character on the client. The server need not know
what locales are used.
11.2. Overview of Universal Character Set Standards
The previous section makes a case for using a universal character set
in NFS version 4. This section makes the case for using UTF-8 as the
specific universal character set for NFS version 4.
[RFC2279] discusses UTF-* (UTF-8 and other UTF-XXX encodings),
Unicode, and UCS-*. There are two standards bodies managing universal
code sets:
o ISO/IEC which has the standard 10646-1
o Unicode which has the Unicode standard
Both standards bodies have pledged to track each other's assignments
of character codes.
The following is a brief analysis of the various standards.
UCS Universal Character Set. This is ISO/IEC 10646-1: "a
multi-octet character set called the Universal Character
Set (UCS), which encompasses most of the world's writing
systems."
UCS-2 a two octet per character encoding that addresses the first
2^16 characters of UCS. Currently there are no UCS
characters beyond that range.
UCS-4 a four octet per character encoding that permits the
encoding of up to 2^31 characters.
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UTF UCS transformation format.
UTF-1 Only historical interest; it has been removed from 10646-1
UTF-7 Encodes the entire "repertoire" of UCS "characters using
only octets with the higher order bit clear". [RFC2152]
describes UTF-7. UTF-7 accomplishes this by reserving one
of the 7bit US-ASCII characters as a "shift" character to
indicate non-US-ASCII characters.
UTF-8 Unlike UTF-7, uses all 8 bits of the octets. US-ASCII
characters are encoded as before unchanged. Any octet with
the high bit cleared can only mean a US-ASCII character.
The high bit set means that a UCS character is being
encoded.
UTF-16 Encodes UCS-4 characters into UCS-2 characters using a
reserved range in UCS-2.
Unicode Unicode and UCS-2 are the same; [RFC2279] states:
Up to the present time, changes in Unicode and amendments
to ISO/IEC 10646 have tracked each other, so that the
character repertoires and code point assignments have
remained in sync. The relevant standardization committees
have committed to maintain this very useful synchronism.
11.3. Difficulties with UCS-4, UCS-2, Unicode
Adapting existing applications, and file systems to multi-octet
schemes like UCS and Unicode can be difficult. A significant amount
of code has been written to process streams of bytes. Also there are
many existing stored objects described with 7 bit or 8 bit
characters. Doubling or quadrupling the bandwidth and storage
requirements seems like an expensive way to accomplish I18N.
UCS-2 and Unicode are "only" 16 bits long. That might seem to be
enough but, according to [Unicode1], 38,887 Unicode characters are
already assigned. And according to [Unicode2] there are still more
languages that need to be added.
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11.4. UTF-8 and its solutions
UTF-8 solves problems for NFS that exist with the use of UCS and
Unicode. UTF-8 will encode 16 bit and 32 bit characters in a way
that will be compact for most users. The encoding table from UCS-4 to
UTF-8, as copied from [RFC2279]:
UCS-4 range (hex.) UTF-8 octet sequence (binary)
0000 0000-0000 007F 0xxxxxxx
0000 0080-0000 07FF 110xxxxx 10xxxxxx
0000 0800-0000 FFFF 1110xxxx 10xxxxxx 10xxxxxx
0001 0000-001F FFFF 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
0020 0000-03FF FFFF 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
0400 0000-7FFF FFFF 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
10xxxxxx
See [RFC2279] for precise encoding and decoding rules. Note because
of UTF-16, the algorithm from Unicode/UCS-2 to UTF-8 needs to account
for the reserved range between D800 and DFFF.
Note that the 16 bit UCS or Unicode characters require no more than 3
octets to encode into UTF-8
Interestingly, UTF-8 has room to handle characters larger than 31
bits, because the leading octet of form:
1111111x
is not defined. If needed, ISO could either use that octet to
indicate a sequence of an encoded 8 octet character, or perhaps use
11111110 to permit the next octet to indicate an even more expandable
character set.
So using UTF-8 to represent character encodings means never having to
run out of room.
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12. Error Definitions
NFS error numbers are assigned to failed operations within a compound
request. A compound request contains a number of NFS operations that
have their results encoded in sequence in a compound reply. The
results of successful operations will consist of an NFS4_OK status
followed by the encoded results of the operation. If an NFS
operation fails, an error status will be entered in the reply and the
compound request will be terminated.
A description of each defined error follows:
NFS4_OK Indicates the operation completed successfully.
NFS4ERR_ACCES Permission denied. The caller does not have the
correct permission to perform the requested
operation. Contrast this with NFS4ERR_PERM,
which restricts itself to owner or privileged
user permission failures.
NFS4ERR_BADHANDLE Illegal NFS file handle. The file handle failed
internal consistency checks.
NFS4ERR_BADTYPE An attempt was made to create an object of a
type not supported by the server.
NFS4ERR_BAD_COOKIE READDIR cookie is stale.
NFS4ERR_BAD_SEQID The sequence number in a locking request is
neither the next expected number or the last
number processed.
NFS4ERR_BAD_STATEID A stateid generated by the current server
instance, but which does not designate any
locking state (either current or superseded)
for a current lockowner-file pair, was used.
NFS4ERR_CLID_INUSE The SETCLIENTID procedure has found that a
client id is already in use by another client.
NFS4ERR_DENIED An attempt to lock a file is denied. Since
this may be a temporary condition, the client
is encouraged to retry the lock request (with
exponential backoff of timeout) until the lock
is accepted.
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NFS4ERR_DQUOT Resource (quota) hard limit exceeded. The
user's resource limit on the server has been
exceeded.
NFS4ERR_EXIST File exists. The file specified already exists.
NFS4ERR_EXPIRED A lease has expired that is being used in the
current procedure.
NFS4ERR_FBIG File too large. The operation would have caused
a file to grow beyond the server's limit.
NFS4ERR_FHEXPIRED The file handle provided is volatile and has
expired at the server.
NFS4ERR_GRACE The server is in its recovery or grace period
which should match the lease period of the
server.
NFS4ERR_INVAL Invalid argument or unsupported argument for an
operation. Two examples are attempting a
READLINK on an object other than a symbolic
link or attempting to SETATTR a time field on a
server that does not support this operation.
NFS4ERR_IO I/O error. A hard error (for example, a disk
error) occurred while processing the requested
operation.
NFS4ERR_ISDIR Is a directory. The caller specified a
directory in a non-directory operation.
NFS4ERR_JUKEBOX The server initiated the request, but was not
able to complete it in a timely fashion. The
client should wait and then try the request
with a new RPC transaction ID. For example,
this error should be returned from a server
that supports hierarchical storage and receives
a request to process a file that has been
migrated. In this case, the server should start
the immigration process and respond to client
with this error.
NFS4ERR_LOCKED A read or write operation was attempted on a
locked file.
NFS4ERR_MINOR_VERS_MISMATCH
The server has received a request that
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specifies an unsupported minor version. The
server must return a COMPOUND4res with a zero
length operations result array.
NFS4ERR_MLINK Too many hard links.
NFS4ERR_MOVED The filesystem which contains the current
filehandle object has been relocated or
migrated to another server. The client may
obtain the new filesystem location by obtaining
the "fs_locations" attribute for the current
filehandle. For further discussion, refer to
the section "Filesystem Migration or
Relocation".
NFS4ERR_NAMETOOLONG The filename in an operation was too long.
NFS4ERR_NODEV No such device.
NFS4ERR_NOENT No such file or directory. The file or
directory name specified does not exist.
NFS4ERR_NOFILEHANDLE The logical current file handle value has not
been set properly. This may be a result of a
malformed COMPOUND operation (i.e. no PUTFH or
PUTROOTFH before an operation that requires the
current file handle be set).
NFS4ERR_NOSPC No space left on device. The operation would
have caused the server's file system to exceed
its limit.
NFS4ERR_NOTDIR Not a directory. The caller specified a non-
directory in a directory operation.
NFS4ERR_NOTEMPTY An attempt was made to remove a directory that
was not empty.
NFS4ERR_NOTSUPP Operation is not supported.
NFS4ERR_NOT_CONFIRMED The client has not confirmed the use of either
a clientid or an OPEN.
NFS4ERR_NOT_SYNC Update synchronization mismatch was detected
during a SETATTR operation.
NFS4ERR_NXIO I/O error. No such device or address.
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NFS4ERR_OLD_STATEID A stateid which designates the locking state
for a lockowner-file at an earlier time was
used.
NFS4ERR_PERM Not owner. The operation was not allowed
because the caller is either not a privileged
user (root) or not the owner of the target of
the operation.
NFS4ERR_READDIR_NOSPC The encoded response to a READDIR request
exceeds the size limit set by the initial
request.
NFS4ERR_RESOURCE For the processing of the COMPOUND procedure,
the server may exhaust available resources and
can not continue processing procedures within
the COMPOUND operation. This error will be
returned from the server in those instances of
resource exhaustion related to the processing
of the COMPOUND procedure.
NFS4ERR_ROFS Read-only file system. A modifying operation
was attempted on a read-only file system.
NFS4ERR_SAME This error is returned by the NVERIFY operation
to signify that the attributes compared were
the same as provided in the client's request.
NFS4ERR_SERVERFAULT An error occurred on the server which does not
map to any of the legal NFS version 4 protocol
error values. The client should translate this
into an appropriate error. UNIX clients may
choose to translate this to EIO.
NFS4ERR_SHARE_DENIED An attempt to OPEN a file with a share
reservation has failed because of a share
conflict.
NFS4ERR_STALE Invalid file handle. The file handle given in
the arguments was invalid. The file referred to
by that file handle no longer exists or access
to it has been revoked.
NFS4ERR_STALE_CLIENTID A clientid not recognized by the server was
used in a locking request.
NFS4ERR_STALE_STATEID A stateid generated by an earlier server
instance was used.
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NFS4ERR_SYMLINK The current file handle provided for a LOOKUP
is not a directory but a symbolic link.
NFS4ERR_TOOSMALL Buffer or request is too small.
NFS4ERR_WRONGSEC The security mechanism being used by the client
for the procedure does not match the server's
security policy. The client should change the
security mechanism being used and retry the
operation.
NFS4ERR_XDEV Attempt to do a cross-device hard link.
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13. NFS Version 4 Requests
For the NFS version 4 RPC program, there are two traditional RPC
procedures: NULL and COMPOUND. All other functionality is defined as
a set of operations and these operations are defined in normal
XDR/RPC syntax and semantics. However, these operations are
encapsulated within the COMPOUND procedure. This requires that the
client combine one or more of the NFS version 4 operations into a
single request.
The NFS4_CALLBACK program is used to provide server to client
signaling and is constructed in a similar fashion as the NFS version
4 program. The procedures CB_NULL and CB_COMPOUND are defined in the
same way as NULL and COMPOUND are within the NFS program. The
CB_COMPOUND request also encapsulates the remaining operations of the
NFS4_CALLBACK program. There is no predefined RPC program number for
the NFS4_CALLBACK program. It is up to the client to specify a
program number in the "transient" program range. The program and
port number of the NFS4_CALLBACK program are provided by the client
as part of the SETCLIENTID operation and therefore is fixed for the
life of the client instantiation.
13.1. Compound Procedure
The COMPOUND procedure provides the opportunity for better
performance within high latency networks. The client can avoid
cumulative latency of multiple RPCs by combining multiple dependent
operations into a single COMPOUND procedure. A compound operation
may provide for protocol simplification by allowing the client to
combine basic procedures into a single request that is customized for
the client's environment.
The basics of the COMPOUND procedures construction is:
+-----------+-----------+-----------+--
| op + args | op + args | op + args |
+-----------+-----------+-----------+--
and the reply looks like this:
+------------+-----------------------+-----------------------+--
|last status | status + op + results | status + op + results |
+------------+-----------------------+-----------------------+--
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13.2. Evaluation of a Compound Request
The server will process the COMPOUND procedure by evaluating each of
the operations within the COMPOUND procedure in order. Each
component operation consists of a 32 bit operation code, followed by
the argument of length determined by the type of operation. The
results of each operation are encoded in sequence into a reply
buffer. The results of each operation are preceded by the opcode and
a status code (normally zero). If an operation results in a non-zero
status code, the status will be encoded and evaluation of the
compound sequence will halt and the reply will be returned.
There are no atomicity requirements for the operations contained
within the COMPOUND procedure. The operations being evaluated as
part of a COMPOUND request may be evaluated simultaneously with other
COMPOUND requests that the server receives.
It is the client's responsibility for recovering from any partially
completed COMPOUND procedure. Therefore, the client should avoid
overly complex COMPOUND procedures in the event of the failure of an
operation with the procedure.
Each operation assumes a "current" and "saved" filehandle that is
available as part of the execution context of the compound request.
Operations may set, change, or return the current filehandle. The
"saved" filehandle is used for temporary storage of a filehandle
value and as operands for the RENAME and LINK operations.
13.3. Operation Values
The operations encoded in the COMPOUND procedure are identified by
operation values. To avoid overlap with the RPC procedure numbers,
operations 0 (zero) and 1 are not defined. Operation 2 it not
defined but reserved for future use with minor versioning.
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14. NFS Version 4 Procedures
14.1. Procedure 0: NULL - No Operation
SYNOPSIS
<null>
ARGUMENT
void;
RESULT
void;
DESCRIPTION
Standard NULL procedure. Void argument, void response. This
procedure has no functionality associated with it. Because of this
it is sometimes used to measure the overhead of processing a
service request. Therefore, the server should ensure that no
unnecessary work is done in servicing this procedure.
ERRORS
None.
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14.2. Procedure 1: COMPOUND - Compound Operations
SYNOPSIS
compoundargs -> compoundres
ARGUMENT
union nfs_argop4 switch (nfs_opnum4 argop) {
case <OPCODE>: <argument>;
...
};
struct COMPOUND4args {
utf8string tag;
uint32_t minorversion;
nfs_argop4 argarray<>;
};
RESULT
union nfs_resop4 switch (nfs_opnum4 resop){
case <OPCODE>: <result>;
...
};
struct COMPOUND4res {
nfsstat4 status;
utf8string tag;
nfs_resop4 resarray<>;
};
DESCRIPTION
The COMPOUND procedure is used to combine one or more of the NFS
operations into a single RPC request. The main NFS RPC program has
two main procedures: NULL and COMPOUND. All other operations use
the COMPOUND procedure as a wrapper.
The COMPOUND procedure is used to combine individual operations
into a single RPC request. The server interprets each of the
operations in turn. If an operation is executed by the server and
the status of that operation is NFS4_OK, then the next operation in
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the COMPOUND procedure is executed. The server continues this
process until there are no more operations to be executed or one of
the operations has a status value other than NFS4_OK.
In the processing of the COMPOUND procedure, the server may find
that it does not have the available resources to execute any or all
of the operations within the COMPOUND sequence. In this case, the
error NFS4ERR_RESOURCE will be returned for the particular
operation within the COMPOUND procedure where the resource
exhaustion occurred. This assumes that all previous operations
within the COMPOUND sequence have been evaluated successfully. The
results for all of the evaluated operations must be returned to the
client.
The COMPOUND arguments contain a "minorversion" field. The initial
and default value for this field is 0 (zero). This field will be
used by future minor versions such that the client can communicate
to the server what minor version is being requested. If the server
receives a COMPOUND procedure with a minorversion field value that
it does not support, the server MUST return an error of
NFS4ERR_MINOR_VERS_MISMATCH and a zero length resultdata array.
Contained within the COMPOUND results is a "status" field. If the
results array length is non-zero, this status must be equivalent to
the status of the last operation that was executed within the
COMPOUND procedure. Therefore, if an operation incurred an error
then the "status" value will be the same error value as is being
returned for the operation that failed.
Note that operations, 0 (zero) and 1 (one) are not defined for the
COMPOUND procedure. If the server receives an operation array with
either of these included, an error of NFS4ERR_NOTSUPP must be
returned. Operation 2 is not defined but reserved for future
definition and use with minor versioning. If the server receives a
operation array that contains operation 2 and the minorversion
field has a value of 0 (zero), an error of NFS4ERR_NOTSUPP is
returned. If an operation array contains an operation 2 and the
minorversion field is non-zero and the server does not support the
minor version, the server returns an error of
NFS4ERR_MINOR_VERS_MISMATCH. Therefore, the
NFS4ERR_MINOR_VERS_MISMATCH error takes precedence over all other
errors.
IMPLEMENTATION
Note that the definition of the "tag" in both the request and
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response are left to the implementor. It may be used to summarize
the content of the compound request for the benefit of packet
sniffers and engineers debugging implementations.
Since an error of any type may occur after only a portion of the
operations have been evaluated, the client must be prepared to
recover from any failure. If the source of an NFS4ERR_RESOURCE
error was a complex or lengthy set of operations, it is likely that
if the number of operations were reduced the server would be able
to evaluate them successfully. Therefore, the client is
responsible for dealing with this type of complexity in recovery.
ERRORS
All errors defined in the protocol
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14.2.1. Operation 3: ACCESS - Check Access Rights
SYNOPSIS
(cfh), accessreq -> supported, accessrights
ARGUMENT
const ACCESS4_READ = 0x00000001;
const ACCESS4_LOOKUP = 0x00000002;
const ACCESS4_MODIFY = 0x00000004;
const ACCESS4_EXTEND = 0x00000008;
const ACCESS4_DELETE = 0x00000010;
const ACCESS4_EXECUTE = 0x00000020;
struct ACCESS4args {
/* CURRENT_FH: object */
uint32_t access;
};
RESULT
struct ACCESS4resok {
uint32_t supported;
uint32_t access;
};
union ACCESS4res switch (nfsstat4 status) {
case NFS4_OK:
ACCESS4resok resok4;
default:
void;
};
DESCRIPTION
ACCESS determines the access rights that a user, as identified by
the credentials in the RPC request, has with respect to the file
system object specified by the current filehandle. The client
encodes the set of access rights that are to be checked in the bit
mask "access". The server checks the permissions encoded in the
bit mask. If a status of NFS4_OK is returned, two bit masks are
included in the response. The first, "supported", represents the
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access rights for which the server can verify reliably. The
second, "access", represents the access rights available to the
user for the filehandle provided. On success, the current
filehandle retains its value.
Note that the supported field will contain only as many values as
was originally sent in the arguments. For example, if the client
sends an ACCESS operation with only the ACCESS4_READ value set and
the server supports this value, the server will return only
ACCESS4_READ even if it could have reliably checked other values.
The results of this operation are necessarily advisory in nature.
A return status of NFS4_OK and the appropriate bit set in the bit
mask does not imply that such access will be allowed to the file
system object in the future. This is because access rights can be
revoked by the server at any time.
The following access permissions may be requested:
ACCESS4_READ Read data from file or read a directory.
ACCESS4_LOOKUP Look up a name in a directory (no meaning for non-
directory objects).
ACCESS4_MODIFY Rewrite existing file data or modify existing
directory entries.
ACCESS4_EXTEND Write new data or add directory entries.
ACCESS4_DELETE Delete an existing directory entry (no meaning for
non-directory objects).
ACCESS4_EXECUTE Execute file (no meaning for a directory).
IMPLEMENTATION
In general, it is not sufficient for the client to attempt to
deduce access permissions by inspecting the uid, gid, and mode
fields in the file attributes. This is because the server may
perform uid or gid mapping or enforce additional access control
restrictions. It is also possible that the server may not be in
the same ID space as the client. In these cases (and perhaps
others), the client can not reliably perform an access check with
only current file attributes.
In the NFS version 2 protocol, the only reliable way to determine
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whether an operation was allowed was to try it and see if it
succeeded or failed. Using the ACCESS procedure in the NFS version
4 protocol, the client can ask the server to indicate whether or
not one or more classes of operations are permitted. The ACCESS
operation is provided to allow clients to check before doing a
series of operations. This is useful in operating systems (such as
UNIX) where permission checking is done only when a directory is
opened. The intent is to make the behavior of opening a remote
file more consistent with the behavior of opening a local file.
For the NFS version 4 protocol, the use of the ACCESS procedure
when opening a regular file is deprecated in favor of using OPEN.
The information returned by the server in response to an ACCESS
call is not permanent. It was correct at the exact time that the
server performed the checks, but not necessarily afterwards. The
server can revoke access permission at any time.
The client should use the effective credentials of the user to
build the authentication information in the ACCESS request used to
determine access rights. It is the effective user and group
credentials that are used in subsequent read and write operations.
Many implementations do not directly support the ACCESS_DELETE
permission. Operating systems like UNIX will ignore the
ACCESS_DELETE bit if set on an access request on a non-directory
object. In these systems, delete permission on a file is
determined by the access permissions on the directory in which the
file resides, instead of being determined by the permissions of the
file itself. Therefore, the mask returned enumerating which access
rights can be determined will have the ACCESS_DELETE value set to
0. This indicates to the client that the server was unable to
check that particular access right. The ACCESS_DELETE bit in the
access mask returned will then be ignored by the client.
ERRORS
NFS4ERR_IO
NFS4ERR_ACCES
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_WRONGSEC
NFS4ERR_MOVED
NFS4ERR_RESOURCE
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14.2.2. Operation 4: CLOSE - Close File
SYNOPSIS
(cfh), stateid -> stateid
ARGUMENT
struct CLOSE4args {
/* CURRENT_FH: object */
stateid4 stateid;
};
RESULT
union CLOSE4res switch (nfsstat4 status) {
case NFS4_OK:
stateid4 stateid;
default:
void;
};
DESCRIPTION
The CLOSE operation releases share reservations for the file as
specified by the current filehandle. The share reservations and
other state information released at the server as a result of this
CLOSE is only associated with the supplied stateid. State
associated with other OPENs is not affected.
If record locks are held, the client SHOULD release all locks
before issuing a CLOSE. The server MAY free all outstanding locks
on CLOSE but some servers may not support the CLOSE of a file that
still has record locks held. The server MUST return failure if any
locks would exist after the CLOSE.
On success, the current filehandle retains its value.
IMPLEMENTATION
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ERRORS
NFS4ERR_BADHANDLE
NFS4ERR_BAD_STATEID
NFS4ERR_EXPIRED
NFS4ERR_FHEXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_MOVED
NFS4ERR_OLD_STATEID
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_STALE_STATEID
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14.2.3. Operation 5: COMMIT - Commit Cached Data
SYNOPSIS
(cfh), offset, count -> verifier
ARGUMENT
struct COMMIT4args {
/* CURRENT_FH: file */
offset4 offset;
count4 count;
};
RESULT
struct COMMIT4resok {
writeverf4 verf;
};
union COMMIT4res switch (nfsstat4 status) {
case NFS4_OK:
COMMIT4resok resok4;
default:
void;
};
DESCRIPTION
The COMMIT operation forces or flushes data to stable storage for
the file specified by the current file handle. The flushed data is
that which was previously written with a WRITE operation which had
the stable field set to UNSTABLE4.
The offset specifies the position within the file where the flush
is to begin. An offset value of 0 (zero) means to flush data
starting at the beginning of the file. The count specifies the
number of bytes of data to flush. If count is 0 (zero), a flush
from offset to the end of the file is done.
The server returns a write verifier upon successful completion of
the COMMIT. The write verifier is used by the client to determine
if the server has restarted or rebooted between the initial
WRITE(s) and the COMMIT. The client does this by comparing the
write verifier returned from the initial writes and the verifier
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returned by the COMMIT procedure. The server must vary the value
of the write verifier at each server event or instantiation that
may lead to a loss of uncommitted data. Most commonly this occurs
when the server is rebooted; however, other events at the server
may result in uncommitted data loss as well.
On success, the current filehandle retains its value.
IMPLEMENTATION
The COMMIT procedure is similar in operation and semantics to the
POSIX fsync(2) system call that synchronizes a file's state with
the disk (file data and metadata is flushed to disk or stable
storage). COMMIT performs the same operation for a client, flushing
any unsynchronized data and metadata on the server to the server's
disk or stable storage for the specified file. Like fsync(2), it
may be that there is some modified data or no modified data to
synchronize. The data may have been synchronized by the server's
normal periodic buffer synchronization activity. COMMIT should
return NFS4_OK, unless there has been an unexpected error.
COMMIT differs from fsync(2) in that it is possible for the client
to flush a range of the file (most likely triggered by a buffer-
reclamation scheme on the client before file has been completely
written).
The server implementation of COMMIT is reasonably simple. If the
server receives a full file COMMIT request, that is starting at
offset 0 and count 0, it should do the equivalent of fsync()'ing
the file. Otherwise, it should arrange to have the cached data in
the range specified by offset and count to be flushed to stable
storage. In both cases, any metadata associated with the file must
be flushed to stable storage before returning. It is not an error
for there to be nothing to flush on the server. This means that
the data and metadata that needed to be flushed have already been
flushed or lost during the last server failure.
The client implementation of COMMIT is a little more complex.
There are two reasons for wanting to commit a client buffer to
stable storage. The first is that the client wants to reuse a
buffer. In this case, the offset and count of the buffer are sent
to the server in the COMMIT request. The server then flushes any
cached data based on the offset and count, and flushes any metadata
associated with the file. It then returns the status of the flush
and the write verifier. The other reason for the client to
generate a COMMIT is for a full file flush, such as may be done at
close. In this case, the client would gather all of the buffers
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for this file that contain uncommitted data, do the COMMIT
operation with an offset of 0 and count of 0, and then free all of
those buffers. Any other dirty buffers would be sent to the server
in the normal fashion.
After a buffer is written by the client with the stable parameter
set to UNSTABLE4, the buffer must be considered as modified by the
client until the buffer has either been flushed via a COMMIT
operation or written via a WRITE operation with stable parameter
set to FILE_SYNC4 or DATA_SYNC4. This is done to prevent the buffer
from being freed and reused before the data can be flushed to
stable storage on the server.
When a response is returned from either a WRITE or a COMMIT
operation and it contains a write verifier that is different than
previously returned by the server, the client will need to
retransmit all of the buffers containing uncommitted cached data to
the server. How this is to be done is up to the implementor. If
there is only one buffer of interest, then it should probably be
sent back over in a WRITE request with the appropriate stable
parameter. If there is more than one buffer, it might be
worthwhile retransmitting all of the buffers in WRITE requests with
the stable parameter set to UNSTABLE4 and then retransmitting the
COMMIT operation to flush all of the data on the server to stable
storage. The timing of these retransmissions is left to the
implementor.
The above description applies to page-cache-based systems as well
as buffer-cache-based systems. In those systems, the virtual
memory system will need to be modified instead of the buffer cache.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_IO
NFS4ERR_LOCKED
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.4. Operation 6: CREATE - Create a Non-Regular File Object
SYNOPSIS
(cfh), name, type -> (cfh), change_info
ARGUMENT
union createtype4 switch (nfs_ftype4 type) {
case NF4LNK:
linktext4 linkdata;
case NF4BLK:
case NF4CHR:
specdata4 devdata;
case NF4SOCK:
case NF4FIFO:
case NF4DIR:
case NF4ATTRDIR:
void;
};
struct CREATE4args {
/* CURRENT_FH: directory for creation */
component4 objname;
createtype4 objtype;
};
RESULT
struct CREATE4resok {
change_info4 cinfo;
};
union CREATE4res switch (nfsstat4 status) {
case NFS4_OK:
CREATE4resok resok4;
default:
void;
};
DESCRIPTION
The CREATE operation creates a non-regular file object in a
directory with a given name. The OPEN procedure MUST be used to
create a regular file.
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The objname specifies the name for the new object. If the objname
has a length of 0 (zero), the error NFS4ERR_INVAL will be returned.
The objtype determines the type of object to be created: directory,
attribute directory, symlink, etc.
If an object of the same name already exists in the directory, the
server will return the error NFS4ERR_EXIST.
For the directory where the new file object was created, the server
returns change_info4 information in cinfo. With the atomic field
of the change_info4 struct, the server will indicate if the before
and after change attributes were obtained atomically with respect
to the file object creation.
The current filehandle is replaced by that of the new object.
IMPLEMENTATION
If the client desires to set attribute values after the create, a
SETATTR operation can be added to the COMPOUND request so that the
appropriate attributes will be set.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_BADTYPE
NFS4ERR_DQUOT
NFS4ERR_EXIST
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_MOVED
NFS4ERR_NAMETOOLONG
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOSPC
NFS4ERR_NOTDIR
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
NFS4ERR_WRONGSEC
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14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting Recovery
SYNOPSIS
clientid ->
ARGUMENT
struct DELEGPURGE4args {
clientid4 clientid;
};
RESULT
struct DELEGPURGE4res {
nfsstat4 status;
};
DESCRIPTION
Purges all of the delegations awaiting recovery for a given client.
This is useful for clients which do not commit delegation
information to stable storage to indicate that conflicting requests
need not be delayed by the server awaiting recovery of delegation
information.
This operation should also be used by clients which do have
delegation information on stable storage after doing all of
delegation recovery that is needed. Using DELEGPURGE will prevent
any delegations which were made by the server but were not sent to
the client and committed to stable storage from holding up other
clients making conflicting requests.
ERRORS
NFS4ERR_RESOURCE
NFS4ERR_STALE_CLIENTID
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14.2.6. Operation 8: DELEGRETURN - Return Delegation
SYNOPSIS
stateid ->
ARGUMENT
struct DELEGRETURN4args {
stateid4 stateid;
};
RESULT
struct DELEGRETURN4res {
nfsstat4 status;
};
DESCRIPTION
Returns the delegation represented by the given stateid.
ERRORS
NFS4ERR_BAD_STATEID
NFS4ERR_OLD_STATEID
NFS4ERR_RESOURCE
NFS4ERR_STALE_STATEID
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14.2.7. Operation 9: GETATTR - Get Attributes
SYNOPSIS
(cfh), attrbits -> attrbits, attrvals
ARGUMENT
struct GETATTR4args {
/* CURRENT_FH: directory or file */
bitmap4 attr_request;
};
RESULT
struct GETATTR4resok {
fattr4 obj_attributes;
};
union GETATTR4res switch (nfsstat4 status) {
case NFS4_OK:
GETATTR4resok resok4;
default:
void;
};
DESCRIPTION
The GETATTR operation will obtain attributes for the file system
object specified by the current filehandle. The client sets a bit
in the bitmap argument for each attribute value that it would like
the server to return. The server returns an attribute bitmap that
indicates the attribute values for which it was able to return,
followed by the attribute values ordered lowest attribute number
first.
The server must return a value for each attribute that the client
requests if the attribute is supported by the server. If the
server does not support an attribute or cannot approximate a useful
value then it must not return the attribute value and must not set
the attribute bit in the result bitmap. The server must return an
error if it supports an attribute but cannot obtain its value. In
that case no attribute values will be returned.
All servers must support the mandatory attributes as specified in
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the section "File Attributes".
On success, the current filehandle retains its value.
IMPLEMENTATION
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_JUKEBOX
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.8. Operation 10: GETFH - Get Current Filehandle
SYNOPSIS
(cfh) -> filehandle
ARGUMENT
/* CURRENT_FH: */
void;
RESULT
struct GETFH4resok {
nfs_fh4 object;
};
union GETFH4res switch (nfsstat4 status) {
case NFS4_OK:
GETFH4resok resok4;
default:
void;
};
DESCRIPTION
This operation returns the current filehandle value.
On success, the current filehandle retains its value.
IMPLEMENTATION
Operations that change the current filehandle like LOOKUP or CREATE
do not automatically return the new filehandle as a result. For
instance, if a client needs to lookup a directory entry and obtain
its filehandle then the following request is needed.
PUTFH (directory filehandle)
LOOKUP (entry name)
GETFH
ERRORS
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NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.9. Operation 11: LINK - Create Link to a File
SYNOPSIS
(sfh), (cfh), newname -> (cfh), change_info
ARGUMENT
struct LINK4args {
/* SAVED_FH: source object */
/* CURRENT_FH: target directory */
component4 newname;
};
RESULT
struct LINK4resok {
change_info4 cinfo;
};
union LINK4res switch (nfsstat4 status) {
case NFS4_OK:
LINK4resok resok4;
default:
void;
};
DESCRIPTION
The LINK operation creates an additional newname for the file
represented by the saved filehandle in the directory represented by
the current filehandle. The existing file and the target directory
must reside within the same file system on the server. On success
the current filehandle represents the newly created file.
For the target directory, the server returns change_info4
information in cinfo. With the atomic field of the change_info4
struct, the server will indicate if the before and after change
attributes were obtained atomically with respect to the link
creation.
If the newname has a length of 0 (zero), the error NFS4ERR_INVAL
will be returned.
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IMPLEMENTATION
Changes to any property of the "hard" linked files are reflected in
all of the linked files. When a link is made to a file, the
attributes for the file should have a value for numlinks that is
one greater than the value before the LINK operation.
The comments under RENAME regarding object and target residing on
the same file system apply here as well. The comments regarding the
target name applies as well.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_DQUOT
NFS4ERR_EXIST
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_MLINK
NFS4ERR_MOVED
NFS4ERR_NAMETOOLONG
NFS4ERR_NOSPC
NFS4ERR_NOTDIR
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
NFS4ERR_XDEV
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14.2.10. Operation 12: LOCK - Create Lock
SYNOPSIS
(cfh) type, seqid, reclaim, owner, offset, length -> stateid,
access
ARGUMENT
enum nfs4_lock_type {
READ_LT = 1,
WRITE_LT = 2,
READW_LT = 3, /* blocking read */
WRITEW_LT = 4 /* blocking write */
};
struct LOCK4args {
/* CURRENT_FH: file */
nfs_lock_type4 locktype;
seqid4 seqid;
bool reclaim;
stateid4 stateid;
offset4 offset;
length4 length;
};
RESULT
union LOCK4res switch (nfsstat4 status) {
case NFS4_OK:
stateid4 stateid;
default:
void;
};
DESCRIPTION
The LOCK operation requests a record lock for the byte range
specified by the offset and length parameters. The lock type is
also specified to be one of the nfs4_lock_types. If this is a
reclaim request, the reclaim parameter will be TRUE;
To lock the whole or entire file, the offset value should be 0
(zero) and the length should have a value of all 1's (maximum value
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for length4 data type).
On success, the current filehandle retains its value.
IMPLEMENTATION
The File Locking section contains a full description of this and
the other file locking operations.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_BAD_SEQID
NFS4ERR_BAD_STATEID
NFS4ERR_DENIED
NFS4ERR_EXPIRED
NFS4ERR_FHEXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_ISDIR
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_OLD_STATEID
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_STALE_CLIENTID
NFS4ERR_STALE_STATEID
NFS4ERR_WRONGSEC
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14.2.11. Operation 13: LOCKT - Test For Lock
SYNOPSIS
(cfh) type, owner, offset, length -> {void, NFS4ERR_DENIED ->
owner}
ARGUMENT
struct LOCKT4args {
/* CURRENT_FH: file */
nfs_lock_type4 locktype;
nfs_lockowner4 owner;
offset4 offset;
length4 length;
};
RESULT
union LOCKT4res switch (nfsstat4 status) {
case NFS4ERR_DENIED:
nfs_lockowner owner;
case NFS4_OK:
void;
default:
void;
};
DESCRIPTION
The LOCKT operation tests the lock as specified in the arguments.
The owner of the lock is returned in the event it is currently
being held; if no lock is held, nothing other than NFS4_OK is
returned.
On success, the current filehandle retains its value.
IMPLEMENTATION
The File Locking section contains a full description of this and
the other file locking procedures.
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ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_DENIED
NFS4ERR_FHEXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_ISDIR
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_STALE_CLIENTID
NFS4ERR_WRONGSEC
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14.2.12. Operation 14: LOCKU - Unlock File
SYNOPSIS
(cfh) type, seqid, stateid, offset, length -> stateid
ARGUMENT
struct LOCKU4args {
/* CURRENT_FH: file */
nfs_lock_type4 type;
seqid4 seqid;
stateid4 stateid;
offset4 offset;
length4 length;
};
RESULT
union LOCKU4res switch (nfsstat4 status) {
case NFS4_OK:
stateid4 stateid;
default:
void;
};
DESCRIPTION
The LOCKU operation unlocks the record lock specified by the
parameters.
On success, the current filehandle retains its value.
IMPLEMENTATION
The File Locking section contains a full description of this and
the other file locking procedures.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_BAD_SEQID
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NFS4ERR_BAD_STATEID
NFS4ERR_EXPIRED
NFS4ERR_FHEXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_OLD_STATEID
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_STALE_CLIENTID
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14.2.13. Operation 15: LOOKUP - Lookup Filename
SYNOPSIS
(cfh), filenames -> (cfh)
ARGUMENT
struct LOOKUP4args {
/* CURRENT_FH: directory */
pathname4 path;
};
RESULT
struct LOOKUP4res {
/* CURRENT_FH: object */
nfsstat4 status;
};
DESCRIPTION
This operation LOOKUPs or finds a file system object starting from
the directory specified by the current filehandle. LOOKUP
evaluates the pathname contained in the array of names and obtains
a new current filehandle from the final name. All but the final
name in the list must be the names of directories.
If the pathname cannot be evaluated either because a component does
not exist or because the client does not have permission to
evaluate a component of the path, then an error will be returned
and the current filehandle will be unchanged.
If the path is a zero length array or if any component in the path
is of zero length, the error NFS4ERR_INVAL will be returned.
IMPLEMENTATION
If the client prefers a partial evaluation of the path then a
sequence of LOOKUP operations can be substituted e.g.
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PUTFH (directory filehandle)
LOOKUP "pub" "foo" "bar"
GETFH
or
PUTFH (directory filehandle)
LOOKUP "pub"
GETFH
LOOKUP "foo"
GETFH
LOOKUP "bar"
GETFH
NFS version 4 servers depart from the semantics of previous NFS
versions in allowing LOOKUP requests to cross mountpoints on the
server. The client can detect a mountpoint crossing by comparing
the fsid attribute of the directory with the fsid attribute of the
directory looked up. If the fsids are different then the new
directory is a server mountpoint. Unix clients that detect a
mountpoint crossing will need to mount the server's filesystem.
Servers that limit NFS access to "shares" or "exported" filesystems
should provide a pseudo-filesystem into which the exported
filesystems can be integrated, so that clients can browse the
server's namespace. The clients view of a pseudo filesystem will
be limited to paths that lead to exported filesystems.
Note: previous versions of the protocol assigned special semantics
to the names "." and "..". NFS version 4 assigns no special
semantics to these names. The LOOKUPP operator must be used to
lookup a parent directory.
Note that this procedure does not follow symbolic links. The
client is responsible for all parsing of filenames including
filenames that are modified by symbolic links encountered during
the lookup process.
If the current file handle supplied is not a directory but a
symbolic link, the error NFS4ERR_SYMLINK is returned as the error.
For all other non-directory file types, the error NFS4ERR_NOTDIR is
returned.
ERRORS
NFS4ERR_ACCES
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NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_MOVED
NFS4ERR_NAMETOOLONG
NFS4ERR_NOENT
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOTDIR
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_SYMLINK
NFS4ERR_WRONGSEC
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14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory
SYNOPSIS
(cfh) -> (cfh)
ARGUMENT
/* CURRENT_FH: object */
void;
RESULT
struct LOOKUPP4res {
/* CURRENT_FH: directory */
nfsstat4 status;
};
DESCRIPTION
The current filehandle is assumed to refer to a directory. LOOKUPP
assigns the filehandle for its parent directory to be the current
filehandle. If there is no parent directory an NFS4ERR_ENOENT
error must be returned. Therefore, NFS4ERR_ENOENT will be returned
by the server when the current filehandle is at the root or top of
the server's file tree.
IMPLEMENTATION
As for LOOKUP, LOOKUPP will also cross mountpoints.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_MOVED
NFS4ERR_NOENT
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
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NFS4ERR_WRONGSEC
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14.2.15. Operation 17: NVERIFY - Verify Difference in Attributes
SYNOPSIS
(cfh), attrbits, attrvals -> -
ARGUMENT
struct NVERIFY4args {
/* CURRENT_FH: object */
bitmap4 attr_request;
fattr4 obj_attributes;
};
RESULT
struct NVERIFY4res {
nfsstat4 status;
};
DESCRIPTION
This operation is used to prefix a sequence of operations to be
performed if one or more attributes have changed on some filesystem
object. If all the attributes match then the error NFS4ERR_SAME
must be returned.
IMPLEMENTATION
This operation is useful as a cache validation operator. If the
object to which the attributes belong has changed then the
following operations may obtain new data associated with that
object. For instance, to check if a file has been changed and
obtain new data if it has:
PUTFH (public)
LOOKUP "pub" "foo" "bar"
NVERIFY attrbits attrs
READ 0 32767
ERRORS
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NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_SAME
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.16. Operation 18: OPEN - Open a Regular File
SYNOPSIS
(cfh), claim, openhow, owner, seqid, access, deny -> (cfh),
stateid, rflags, open_confirm, delegation
ARGUMENT
struct OPEN4args {
open_claim4 claim;
openflag4 openhow;
nfs_lockowner4 owner;
seqid4 seqid;
uint32_t share_access;
uint32_t share_deny;
};
enum createmode4 {
UNCHECKED4 = 0,
GUARDED4 = 1,
EXCLUSIVE4 = 2
};
union createhow4 switch (createmode4 mode) {
case UNCHECKED4:
case GUARDED4:
fattr4 createattrs;
case EXCLUSIVE4:
createverf4 verf;
};
enum opentype4 {
OPEN4_NOCREATE = 0,
OPEN4_CREATE = 1
};
union openflag4 switch (opentype4 opentype) {
case OPEN4_CREATE:
createhow4 how;
default:
void;
};
/* Next definitions used for OPEN delegation */
enum limit_by4 {
NFS_LIMIT_SIZE = 1,
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NFS_LIMIT_BLOCKS = 2
/* others as needed */
};
struct nfs_modified_limit4 {
uint32_t num_blocks;
uint32_t bytes_per_block;
};
union nfs_space_limit4 switch (limit_by4 limitby) {
/* limit specified as file size */
case NFS_LIMIT_SIZE:
uint64_t filesize;
/* limit specified by number of blocks */
case NFS_LIMIT_BLOCKS:
nfs_modified_limit4 mod_blocks;
} ;
/*
* Share Access and Deny constants for open argument
*/
const OPEN4_SHARE_ACCESS_READ = 0x00000001;
const OPEN4_SHARE_ACCESS_WRITE = 0x00000002;
const OPEN4_SHARE_ACCESS_BOTH = 0x00000003;
const OPEN4_SHARE_DENY_NONE = 0x00000000;
const OPEN4_SHARE_DENY_READ = 0x00000001;
const OPEN4_SHARE_DENY_WRITE = 0x00000002;
const OPEN4_SHARE_DENY_BOTH = 0x00000003;
enum open_delegation_type4 {
OPEN_DELEGATE_NONE = 0,
OPEN_DELEGATE_READ = 1,
OPEN_DELEGATE_WRITE = 2
};
enum open_claim_type4 {
CLAIM_NULL = 0,
CLAIM_PREVIOUS = 1,
CLAIM_DELEGATE_CUR = 2,
CLAIM_DELEGATE_PREV = 3
};
struct open_claim_delegate_cur4 {
pathname4 file;
stateid4 delegate_stateid;
};
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union open_claim4 switch (open_claim_type4 claim) {
/*
* No special rights to file. Ordinary OPEN of the specified file.
*/
case CLAIM_NULL:
/* CURRENT_FH: directory */
pathname4 file;
/*
* Right to the file established by an open previous to server
* reboot. File identified by filehandle obtained at that time
* rather than by name.
*/
case CLAIM_PREVIOUS:
/* CURRENT_FH: file being reclaimed */
uint32_t delegate_type;
/*
* Right to file based on a delegation granted by the server.
* File is specified by name.
*/
case CLAIM_DELEGATE_CUR:
/* CURRENT_FH: directory */
open_claim_delegate_cur4 delegate_cur_info;
/* Right to file based on a delegation granted to a previous boot
* instance of the client. File is specified by name.
*/
case CLAIM_DELEGATE_PREV:
/* CURRENT_FH: directory */
pathname4 file_delegate_prev;
};
RESULT
const OPEN4_RESULT_MLOCK = 0x00000001;
struct open_read_delegation4 {
stateid4 stateid; /* Stateid for delegation*/
bool recall; /* Pre-recalled flag for
delegations obtained
by reclaim
(CLAIM_PREVIOUS) */
nfsace4 permissions; /* Defines users who don't
need an ACCESS call to
open for read */
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};
struct open_write_delegation4 {
stateid4 stateid; /* Stateid for delegation
be flushed to the server
on close. */
bool recall; /* Pre-recalled flag for
delegations obtained
by reclaim
(CLAIM_PREVIOUS) */
nfs_space_limit4 space_limit; /* Defines condition that
the client must check to
determine whether the
file needs to be flushed
to the server on close.
*/
nfsace4 permissions; /* Defines users who don't
need an ACCESS call as
part of a delegated
open. */
};
union open_delegation4
switch (open_delegation_type4 delegation_type) {
case OPEN_DELEGATE_NONE:
void;
case OPEN_DELEGATE_READ:
open_read_delegation4 read;
case OPEN_DELEGATE_WRITE:
open_write_delegation4 write;
};
struct OPEN4resok {
stateid4 stateid; /* Stateid for open */
uint32_t rflags; /* Result flags */
cookieverf4 open_confirm; /* OPEN_CONFIRM verifier */
open_delegation4 delegation; /* Info on any open
delegation */
};
union OPEN4res switch (nfsstat4 status) {
case NFS4_OK:
/* CURRENT_FH: opened file */
OPEN4resok result;
default:
void;
};
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DESCRIPTION
The OPEN operation creates and/or opens a regular file in a
directory with the provided name. If the file does not exist at
the server and creation is desired, specification of the method of
creation is provided by the openhow parameter. The client has the
choice of three creation methods: UNCHECKED, GUARDED, or EXCLUSIVE.
UNCHECKED means that the file should be created without checking
for the existence of a duplicate object in the same directory. For
this type of create, createattrs specifies the initial set of
attributes for the file (NOTE: need to define exactly which
attributes should be set and if the file exists, should the
attributes be modified if the file exists). If GUARDED is
specified, the server checks for the presence of a duplicate object
by name before performing the create. If a duplicate exists, an
error of NFS4ERR_EXIST is returned as the status. If the object
does not exist, the request is performed as described for
UNCHECKED.
EXCLUSIVE specifies that the server is to follow exclusive creation
semantics, using the verifier to ensure exclusive creation of the
target. The server should check for the presence of a duplicate
object by name. If the object does not exist, the server creates
the object and stores the verifier with the object. If the object
does exist and the stored verifier matches the client provided
verifier, the server uses the existing object as the newly created
object. If the stored verifier does not match, then an error of
NFS4ERR_EXIST is returned. No attributes may be provided in this
case, since the server may use an attribute of the target object to
store the verifier. (NOTE: does a specific attribute need to be
specified for storage of verifier )
Upon successful creation, the current filehandle is replaced by
that of the new object.
The OPEN procedure provides for DOS SHARE capability with the use
of the access and deny fields of the OPEN arguments. The client
specifies at OPEN the required access and deny modes. For clients
that do not directly support SHAREs (i.e. Unix), the expected deny
value is DENY_NONE. In the case that there is a existing SHARE
reservation that conflicts with the OPEN request, the server
returns the error NFS4ERR_DENIED. For a complete SHARE request,
the client must provide values for the owner and seqid fields for
the OPEN argument. For additional discussion of SHARE semantics
see the section on 'Share Reservations'.
In the case that the client is recovering state from a server
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failure, the reclaim field of the OPEN argument is used to signify
that the request is meant to reclaim state previously held.
The "claim" field of the OPEN argument is used to specify the file
to be opened and the state information which the client claims to
possess. There are four basic claim types which cover the various
situations for an OPEN. They are as follows:
CLAIM_NULL For the client, this is a new OPEN
request and there is no previous state
associate with the file for the client.
CLAIM_PREVIOUS The client is claiming basic OPEN state
for a file that was held previous to a
server reboot. Generally used when a
server is returning persistent file
handles; the client may not have the
file name to reclaim the OPEN.
CLAIM_DELEGATE_CUR The client is claiming a delegation for
OPEN as granted by the server.
Generally this is done as part of
recalling a delegation.
CLAIM_DELEGATE_PREV The client is claiming a delegation
granted to a previous client instance;
used after the client reboots.
For OPEN requests whose claim type is other than CLAIM_PREVIOUS
(i.e. requests other than those devoted to reclaiming opens after a
server reboot) that reach the server during its grace or lease
expiration period, the server returns an error of NFS4ERR_GRACE.
For any OPEN request, the server may return an open delegation,
which allows further opens and closes to be handled locally on the
client as described in the section Open Delegation. Note that
delegation is up to the server to decide. The client should never
assume that delegation will or will not be granted in a particular
instance. It should always be prepared for either case. A partial
exception is the reclaim (CLAIM_PREVIOUS) case, in which a
delegation type is claimed. In this case, delegation will always
be granted, although the server may specify an immediate recall in
the delegation structure.
IMPLEMENTATION
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The OPEN procedure contains support for EXCLUSIVE create. The
mechanism is similar to the support in NFS version 3 [RFC1813]. As
in NFS version 3, this mechanism provides reliable exclusive
creation. Exclusive create is invoked when the how parameter is
EXCLUSIVE. In this case, the client provides a verifier that can
reasonably be expected to be unique. A combination of a client
identifier, perhaps the client network address, and a unique number
generated by the client, perhaps the RPC transaction identifier,
may be appropriate.
If the object does not exist, the server creates the object and
stores the verifier in stable storage. For file systems that do not
provide a mechanism for the storage of arbitrary file attributes,
the server may use one or more elements of the object meta-data to
store the verifier. The verifier must be stored in stable storage
to prevent erroneous failure on retransmission of the request. It
is assumed that an exclusive create is being performed because
exclusive semantics are critical to the application. Because of the
expected usage, exclusive CREATE does not rely solely on the
normally volatile duplicate request cache for storage of the
verifier. The duplicate request cache in volatile storage does not
survive a crash and may actually flush on a long network partition,
opening failure windows. In the UNIX local file system
environment, the expected storage location for the verifier on
creation is the meta-data (time stamps) of the object. For this
reason, an exclusive object create may not include initial
attributes because the server would have nowhere to store the
verifier.
If the server can not support these exclusive create semantics,
possibly because of the requirement to commit the verifier to
stable storage, it should fail the OPEN request with the error,
NFS4ERR_NOTSUPP.
During an exclusive CREATE request, if the object already exists,
the server reconstructs the object's verifier and compares it with
the verifier in the request. If they match, the server treats the
request as a success. The request is presumed to be a duplicate of
an earlier, successful request for which the reply was lost and
that the server duplicate request cache mechanism did not detect.
If the verifiers do not match, the request is rejected with the
status, NFS4ERR_EXIST.
Once the client has performed a successful exclusive create, it
must issue a SETATTR to set the correct object attributes. Until
it does so, it should not rely upon any of the object attributes,
since the server implementation may need to overload object meta-
data to store the verifier. The subsequent SETATTR must not occur
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in the same COMPOUND request as the OPEN. This separation will
guarantee that the exclusive create mechanism will continue to
function properly in the face of retransmission of the request.
Use of the GUARDED attribute does not provide exactly-once
semantics. In particular, if a reply is lost and the server does
not detect the retransmission of the request, the procedure can
fail with NFS4ERR_EXIST, even though the create was performed
successfully.
For SHARE reservations, the client must specify a value for access
that is one of READ, WRITE, or BOTH. For deny, the client must
specify one of NONE, READ, WRITE, or BOTH. If the client fails to
do this, the server must return NFS4ERR_INVAL.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BAD_SEQID
NFS4ERR_DQUOT
NFS4ERR_EXIST
NFS4ERR_GRACE
NFS4ERR_IO
NFS4ERR_MOVED
NFS4ERR_NAMETOOLONG
NFS4ERR_NOSPC
NFS4ERR_NOTDIR
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_SHARE_DENIED
NFS4ERR_STALE_CLIENTID
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14.2.17. Operation 19: OPENATTR - Open Named Attribute Directory
SYNOPSIS
(cfh) -> (cfh)
ARGUMENT
/* CURRENT_FH: file or directory */
void;
RESULT
struct OPENATTR4res {
/* CURRENT_FH: name attr directory*/
nfsstat4 status;
};
DESCRIPTION
The OPENATTR operation is used to obtain the filehandle of the
named attribute directory associated with the current filehandle.
The result of the OPENATTR will be a filehandle of type NF4ATTRDIR.
From this filehandle, READDIR and LOOKUP procedures can be used to
obtain filehandles for the various named attributes associated with
the original file system object. Filehandles returned within the
named attribute directory will have a type of NF4NAMEDATTR.
IMPLEMENTATION
If the server does not support named attributes for the current
filehandle, an error of NFS4ERR_NOTSUPP will be returned to the
client.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_JUKEBOX
NFS4ERR_MOVED
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NFS4ERR_NOENT
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open
SYNOPSIS
(cfh), seqid, open_confirm-> stateid
ARGUMENT
struct OPEN_CONFIRM4args {
/* CURRENT_FH: opened file */
seqid4 seqid;
cookieverf4 open_confirm; /* OPEN_CONFIRM verifier */
};
RESULT
struct OPEN_CONFIRM4resok {
stateid4 stateid;
};
union OPEN_CONFIRM4res switch (nfsstat4 status) {
case NFS4_OK:
OPEN_CONFIRM4resok resok4;
default:
void;
};
DESCRIPTION
This operation is used to confirm the sequence id usage for the
first time that a nfs_lockowner is used by a client. The OPEN
operation returns a opaque confirmation cookie that is then passed
to this operation along with the next sequence id for the
nfs_lockowner. The sequence id passed to the OPEN_CONFIRM must be
1 (one) greater than the seqid passed to the OPEN operation from
which the open_confirm value was obtained. If the receives an
unexpected sequence id with respect to the original open, then the
server assumes that the client will not confirm the original OPEN
and all state associated with the original OPEN is released by the
server.
On success, the current filehandle retains its value.
IMPLEMENTATION
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When the client first initiates contact with a server for a
particular nfs_lockowner, the sequence id value needs to be
confirmed with the server. The two step process of OPENing a file
and then OPEN_CONFIRMing the sequence id for the nfs_lockowner is
meant to deal with an OPEN operation that is retransmitted within
the network. The server must hold unconfirmed OPEN state until one
of three events occur. The client sends an OPEN_CONFIRM request
with the appropriate sequence id and confirmation cookie within the
lease period. Second, the client sends a request with a sequence
id that incorrect for the nfs_lockowner (out of sequence). Third,
the client send no request for the nfs_lockowner within the lease
period.
ERRORS
NFS4ERR_BADHANDLE
NFS4ERR_BAD_SEQID
NFS4ERR_EXPIRED
NFS4ERR_FHEXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_MOVED
NFS4ERR_NOENT
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.19. Operation 21: PUTFH - Set Current Filehandle
SYNOPSIS
filehandle -> (cfh)
ARGUMENT
struct PUTFH4args {
nfs4_fh object;
};
RESULT
struct PUTFH4res {
/* CURRENT_FH: */
nfsstat4 status;
};
DESCRIPTION
Replaces the current filehandle with the filehandle provided as an
argument.
IMPLEMENTATION
Commonly used as the first operator in any NFS request to set the
context for following operations.
ERRORS
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_MOVED
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.20. Operation 22: PUTPUBFH - Set Public Filehandle
SYNOPSIS
- -> (cfh)
ARGUMENT
void;
RESULT
struct PUTPUBFH4res {
/* CURRENT_FH: root fh */
nfsstat4 status;
};
DESCRIPTION
Replaces the current filehandle with the filehandle that represents
the public filehandle of the server's name space. This filehandle
may be different from the "root" filehandle which may be associated
with some other directory on the server.
IMPLEMENTATION
Used as the first operator in any NFS request to set the context
for following operations.
ERRORS
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_WRONGSEC
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14.2.21. Operation 23: PUTROOTFH - Set Root Filehandle
SYNOPSIS
- -> (cfh)
ARGUMENT
void;
RESULT
struct PUTROOTFH4res {
/* CURRENT_FH: root fh */
nfsstat4 status;
};
DESCRIPTION
Replaces the current filehandle with the filehandle that represents
the root of the server's name space. From this filehandle a LOOKUP
operation can locate any other filehandle on the server. This
filehandle may be different from the "public" filehandle which may
be associated with some other directory on the server.
IMPLEMENTATION
Commonly used as the first operator in any NFS request to set the
context for following operations.
ERRORS
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_WRONGSEC
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14.2.22. Operation 24: READ - Read from File
SYNOPSIS
(cfh), offset, count, stateid -> eof, data
ARGUMENT
struct READ4args {
/* CURRENT_FH: file */
stateid4 stateid;
offset4 offset;
count4 count;
};
RESULT
struct READ4resok {
bool eof;
opaque data<>;
};
union READ4res switch (nfsstat4 status) {
case NFS4_OK:
READ4resok resok4;
default:
void;
};
DESCRIPTION
The READ operation reads data from the regular file identified by
the current filehandle.
The client provides an offset of where the READ is to start and a
count of how many bytes are to be read. An offset of 0 (zero)
means to read data starting at the beginning of the file. If
offset is greater than or equal to the size of the file, the
status, NFS4_OK, is returned with a data length set to 0 (zero) and
eof set to TRUE. The READ is subject to access permissions
checking.
If the client specifies a count value of 0 (zero), the READ
succeeds and returns 0 (zero) bytes of data again subject to access
permissions checking. The server may choose to return fewer bytes
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than specified by the client. The client needs to check for this
condition and handle the condition appropriately.
The stateid value for a READ request represents a value returned
from a previous record lock or share reservation request. Used by
the server to verify that the associated lock is still valid and to
update lease timeouts for the client.
If the read ended at the end-of-file (formally, in a correctly
formed READ request, if offset + count is equal to the size of the
file), eof is returned as TRUE; otherwise it is FALSE. A successful
READ of an empty file will always return eof as TRUE.
IMPLEMENTATION
It is possible for the server to return fewer than count bytes of
data. If the server returns less than the count requested and eof
set to FALSE, the client should issue another READ to get the
remaining data. A server may return less data than requested under
several circumstances. The file may have been truncated by another
client or perhaps on the server itself, changing the file size from
what the requesting client believes to be the case. This would
reduce the actual amount of data available to the client. It is
possible that the server may back off the transfer size and reduce
the read request return. Server resource exhaustion may also occur
necessitating a smaller read return.
If the file is locked the server will return an NFS4ERR_LOCKED
error. Since the lock may be of short duration, the client may
choose to retransmit the READ request (with exponential backoff)
until the operation succeeds.
ERRORS
NFS4ERR_ACCES NFS4ERR_BADHANDLE NFS4ERR_BAD_STATEID NFS4ERR_DENIED
NFS4ERR_EXPIRED NFS4ERR_FHEXPIRED NFS4ERR_GRACE NFS4ERR_INVAL
NFS4ERR_IO NFS4ERR_JUKEBOX NFS4ERR_LOCKED NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE NFS4ERR_NOT_CONFIRMED NFS4ERR_NXIO
NFS4ERR_OLD_STATEID NFS4ERR_RESOURCE NFS4ERR_SERVERFAULT
NFS4ERR_STALE NFS4ERR_STALE_STATEID NFS4ERR_WRONGSEC
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14.2.23. Operation 25: READDIR - Read Directory
SYNOPSIS
(cfh), cookie, cookieverf, dircount, maxcount, attrbits ->
cookieverf { cookie, filename, attrbits, attributes }
ARGUMENT
struct READDIR4args {
/* CURRENT_FH: directory */
nfs_cookie4 cookie;
cookieverf4 cookieverf;
count4 dircount;
count4 maxcount;
bitmap4 attr_request;
};
RESULT
struct entry4 {
nfs_cookie4 cookie;
component4 name;
fattr4 attrs;
entry4 *nextentry;
};
struct dirlist4 {
entry4 *entries;
bool eof;
};
struct READDIR4resok {
cookieverf4 cookieverf;
dirlist4 reply;
};
union READDIR4res switch (nfsstat4 status) {
case NFS4_OK:
READDIR4resok resok4;
default:
void;
};
DESCRIPTION
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The READDIR operation retrieves a variable number of entries from a
file system directory and returns client requested attributes for
each entry along with information to allow the client to request
additional directory entries in a subsequent READDIR.
The arguments contain a cookie value that represents where the
READDIR should start within the directory. A value of 0 (zero) for
the cookie is used to start reading at the beginning of the
directory. For subsequent READDIR requests, the client specifies a
cookie value that is provided by the server on a previous READDIR
request.
The cookieverf value should be set to 0 (zero) when the cookie
value is 0 (zero) (first directory read). On subsequent requests,
it should be a cookieverf as returned by the server. The
cookieverf must match that returned by the READDIR in which the
cookie was acquired.
The dircount portion of the argument is a hint of the maximum
number of bytes of directory information that should be returned.
This value is the XDR encoded length of the name of the directory
entries and the cookie value for the entries. The server may
return less data.
The maxcount value of the argument is the maximum number of bytes
for the result. This maximum size represents all of the data being
returned and includes the XDR overhead. The server may return less
data. If the server is unable to return a single directory entry
within the maxcount limit, the error NFS4ERR_READDIR_NOSPC will be
returned to the client.
Finally, attrbits represents the list of attributes to be returned
for each directory entry supplied by the server.
On successful return, the server's response will provide a list of
directory entries. Each of these entries contains the name of the
directory entry, a cookie value for that entry, and the associated
attributes as requested.
The cookie value is only meaningful to the server and is used as a
"bookmark" for the directory entry. As mentioned, this cookie is
used by the client for subsequent READDIR operations so that it may
continue reading a directory. The cookie is similar in concept to
a READ offset but should not be interpreted as such by the client.
Ideally, the cookie value should not change if the directory is
modified.
In some cases, the server may encounter an error while obtaining
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the attributes for a directory entry. Instead of returning an
error for the entire READDIR operation, the server can instead
return the attribute 'fattr4_rdattr_error'. With this, the server
is able to communicate the failure to the client and not fail the
entire operation in the instance of what might be a transient
failure. Obviously, the client must request the
fattr4_rdattr_error attribute for this method to work properly. If
the client does not request the attribute, the server has no choice
but to return failure for the entire READDIR operation.
For some file system environments, the directory entries "." and
".." have special meaning and in other environments, they may not.
If the server supports these special entries within a directory,
they should not be returned to the client as part of the READDIR
response. To enable some client environments, the cookie values of
0, 1, and 2 are to be considered reserved. For READDIR arguments,
cookie values of 1 and 2 should not be used and for READDIR results
cookie values of 0, 1, and 2 should not returned.
IMPLEMENTATION
The server's file system directory representations can differ
greatly. A client's programming interfaces may also be bound to
the local operating environment in a way that does not translate
well into the NFS protocol. Therefore the use of the dircount and
maxcount fields are provided to allow the client the ability to
provide guidelines to the server. If the client is aggressive
about attribute collection during a READDIR, the server has an idea
of how to limit the encoded response. The dircount field provides
a hint on the number of entries based solely on the names of the
directory entries.
The cookieverf may be used by the server to help manage cookie
values that may become stale. It should be a rare occurrence that
a server is unable to continue properly reading a directory with
the provided cookie/cookieverf pair. The server should make every
effort to avoid this condition since the application at the client
may not be able to properly handle this type of failure.
The use of the cookieverf will also protect the client from using
READDIR cookie values that may be stale. For example, if the file
system has been migrated, the server may or may not be able to use
the same cookie values to service READDIR as the previous server
used. With the client providing the cookieverf, the server is able
to provide the appropriate response to the client. This prevents
the case where the server may accept a cookie value but the
underlying directory has changed and the response is invalid from
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the client's context of its previous READDIR.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_BAD_COOKIE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_JUKEBOX
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOTDIR
NFS4ERR_NOTSUPP
NFS4ERR_READDIR_NOSPC
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_TOOSMALL
NFS4ERR_WRONGSEC
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14.2.24. Operation 26: READLINK - Read Symbolic Link
SYNOPSIS
(cfh) -> linktext
ARGUMENT
/* CURRENT_FH: symlink */
void;
RESULT
struct READLINK4resok {
linktext4 link;
};
union READLINK4res switch (nfsstat4 status) {
case NFS4_OK:
READLINK4resok resok4;
default:
void;
};
DESCRIPTION
READLINK reads the data associated with a symbolic link. The data
is a UTF-8 string that is opaque to the server. That is, whether
created by an NFS client or created locally on the server, the data
in a symbolic link is not interpreted when created, but is simply
stored.
IMPLEMENTATION
A symbolic link is nominally a pointer to another file. The data
is not necessarily interpreted by the server, just stored in the
file. It is possible for a client implementation to store a path
name that is not meaningful to the server operating system in a
symbolic link. A READLINK operation returns the data to the client
for interpretation. If different implementations want to share
access to symbolic links, then they must agree on the
interpretation of the data in the symbolic link.
The READLINK operation is only allowed on objects of type, NF4LNK.
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The server should return the error, NFS4ERR_INVAL, if the object is
not of type, NF4LNK.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_JUKEBOX
NFS4ERR_MOVED
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.25. Operation 27: REMOVE - Remove Filesystem Object
SYNOPSIS
(cfh), filename -> change_info
ARGUMENT
struct REMOVE4args {
/* CURRENT_FH: directory */
component4 target;
};
RESULT
struct REMOVE4resok {
change_info4 cinfo;
}
union REMOVE4res switch (nfsstat4 status) {
case NFS4_OK:
REMOVE4resok resok4;
default:
void;
}
DESCRIPTION
The REMOVE operation removes (deletes) a directory entry named by
filename from the directory corresponding to the current
filehandle. If the entry in the directory was the last reference
to the corresponding file system object, the object may be
destroyed.
For the directory where the filename was removed, the server
returns change_info4 information in cinfo. With the atomic field
of the change_info4 struct, the server will indicate if the before
and after change attributes were obtained atomically with respect
to the removal.
IMPLEMENTATION
NFS versions 2 and 3 required a different operator RMDIR for
directory removal. NFS version 4 REMOVE can be used to delete any
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directory entry independent of its file type.
The concept of last reference is server specific. However, if the
numlinks field in the previous attributes of the object had the
value 1, the client should not rely on referring to the object via
a file handle. Likewise, the client should not rely on the
resources (disk space, directory entry, and so on.) formerly
associated with the object becoming immediately available. Thus, if
a client needs to be able to continue to access a file after using
REMOVE to remove it, the client should take steps to make sure that
the file will still be accessible. The usual mechanism used is to
use RENAME to rename the file from its old name to a new hidden
name.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_IO
NFS4ERR_MOVED
NFS4ERR_NAMETOOLONG
NFS4ERR_NOENT
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOTDIR
NFS4ERR_NOTEMPTY
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.26. Operation 28: RENAME - Rename Directory Entry
SYNOPSIS
(sfh), oldname (cfh), newname -> source_change_info,
target_change_info
ARGUMENT
struct RENAME4args {
/* SAVED_FH: source directory */
component4 oldname;
/* CURRENT_FH: target directory */
component4 newname;
};
RESULT
struct RENAME4resok {
change_info4 source_cinfo;
change_info4 target_cinfo;
};
union RENAME4res switch (nfsstat4 status) {
case NFS4_OK:
RENAME4resok resok4;
default:
void;
};
DESCRIPTION
The RENAME operation renames the object identified by oldname in
the source directory corresponding to the saved filehandle to
newname in the target directory corresponding to the current
filehandle. The operation is required to be atomic to the client.
Source and target directories must reside on the same file system
on the server.
If the target directory already contains an entry with the name,
newname, the source object must be compatible with the target:
either both are non-directories or both are directories and the
target must be empty. If compatible, the existing target is
removed before the rename occurs. If they are not compatible or if
the target is a directory but not empty, the server will return the
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error, NFS4ERR_EXIST.
If oldname and newname both refer to the same file (they might be
hard links of each other), then RENAME should perform no action and
return success.
For both directories involved in the RENAME, the server returns
change_info4 information. With the atomic field of the
change_info4 struct, the server will indicate if the before and
after change attributes were obtained atomically with respect to
the rename.
IMPLEMENTATION
The RENAME operation must be atomic to the client. The statement
"source and target directories must reside on the same file system
on the server" means that the fsid fields in the attributes for the
directories are the same. If they reside on different file systems,
the error, NFS4ERR_XDEV, is returned. Even though the operation is
atomic, the status, NFS4ERR_MLINK, may be returned if the server
used a "unlink/link/unlink" sequence internally.
A filehandle may or may not become stale or expire on a rename.
However, server implementors are strongly encouraged to attempt to
keep file handles from becoming stale or expiring in this fashion.
On some servers, the filenames, "." and "..", are illegal as either
oldname or newname. In addition, neither oldname nor newname can
be an alias for the source directory. These servers will return
the error, NFS4ERR_INVAL, in these cases.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_DQUOT
NFS4ERR_EXIST
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_ISDIR
NFS4ERR_MLINK
NFS4ERR_MOVED
NFS4ERR_NAMETOOLONG
NFS4ERR_NOENT
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NFS4ERR_NOFILEHANDLE
NFS4ERR_NOSPC
NFS4ERR_NOTDIR
NFS4ERR_NOTEMPTY
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
NFS4ERR_XDEV
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14.2.27. Operation 29: RENEW - Renew a Lease
SYNOPSIS
stateid -> ()
ARGUMENT
struct RENEW4args {
stateid4 stateid;
};
RESULT
struct RENEW4res {
nfsstat4 status;
};
DESCRIPTION
The RENEW operation is used by the client to renew leases which it
currently holds at a server. In processing the RENEW request, the
server renews all leases associated with the client. The
associated leases are determined by the client id provided via the
SETCLIENTID procedure.
The stateid for RENEW may not be one of the special stateids
consisting of all bits 0 (zero) or all bits 1.
IMPLEMENTATION
ERRORS
NFS4ERR_BAD_STATEID
NFS4ERR_EXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_MOVED
NFS4ERR_OLD_STATEID
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE_STATEID
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NFS4ERR_WRONGSEC
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14.2.28. Operation 30: RESTOREFH - Restore Saved Filehandle
SYNOPSIS
(sfh) -> (cfh)
ARGUMENT
/* SAVED_FH: */
void;
RESULT
struct RESTOREFH4res {
/* CURRENT_FH: value of saved fh */
nfsstat4 status;
};
DESCRIPTION
Set the current filehandle to the value in the saved filehandle.
If there is no saved filehandle then return an error NFS4ERR_INVAL.
IMPLEMENTATION
Operations like OPEN and LOOKUP use the current filehandle to
represent a directory and replace it with a new filehandle.
Assuming the previous filehandle was saved with a SAVEFH operator,
the previous filehandle can be restored as the current filehandle.
This is commonly used to obtain post-operation attributes for the
directory, e.g.
PUTFH (directory filehandle)
SAVEFH
GETATTR attrbits (pre-op dir attrs)
CREATE optbits "foo" attrs
GETATTR attrbits (file attributes)
RESTOREFH
GETATTR attrbits (post-op dir attrs)
ERRORS
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NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.29. Operation 31: SAVEFH - Save Current Filehandle
SYNOPSIS
(cfh) -> (sfh)
ARGUMENT
/* CURRENT_FH: */
void;
RESULT
struct SAVEFH4res {
/* SAVED_FH: value of current fh */
nfsstat4 status;
};
DESCRIPTION
Save the current filehandle. If a previous filehandle was saved
then it is no longer accessible. The saved filehandle can be
restored as the current filehandle with the RESTOREFH operator.
On success, the current filehandle retains its value.
IMPLEMENTATION
ERRORS
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.30. Operation 32: SECINFO - Obtain Available Security
SYNOPSIS
(cfh), name -> { secinfo }
ARGUMENT
struct SECINFO4args {
/* CURRENT_FH: */
component4 name;
};
RESULT
enum rpc_gss_svc_t {
RPC_GSS_SVC_NONE = 1,
RPC_GSS_SVC_INTEGRITY = 2,
RPC_GSS_SVC_PRIVACY = 3
};
struct rpcsec_gss_info {
sec_oid4 oid;
qop4 qop;
rpc_gss_svc_t service;
};
struct secinfo4 {
uint32_t flavor;
opaque flavor_info<>; /* null for AUTH_SYS, AUTH_NONE;
contains rpcsec_gss_info for
RPCSEC_GSS. */
};
typedef secinfo4 SECINFO4resok<>;
union SECINFO4res switch (nfsstat4 status) {
case NFS4_OK:
SECINFO4resok resok4;
default:
void;
};
DESCRIPTION
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The SECINFO operation is used by the client to obtain a list of
valid RPC authentication flavors for a specific file handle, file
name pair. The result will contain an array which represents the
security mechanisms available. The array entries are represented
by the secinfo4 structure. The field 'flavor' will contain a value
of AUTH_NONE, AUTH_SYS (as defined in [RFC1831]), or RPCSEC_GSS (as
defined in [RFC2203]).
For the flavors, AUTH_NONE, and AUTH_SYS no additional security
information is returned. For a return value of RPCSEC_GSS, a
security triple is returned that contains the mechanism object id
(as defined in [RFC2078]), the quality of protection (as defined in
[RFC2078]) and the service type (as defined in [RFC2203]). It is
possible for SECINFO to return multiple entries with flavor equal
to RPCSEC_GSS with different security triple values.
IMPLEMENTATION
The SECINFO operation is expected to be used by the NFS client when
the error value of NFS4ERR_WRONGSEC is returned from another NFS
operation. This signifies to the client that the server's security
policy is different from what the client is currently using. At
this point, the client is expected to obtain a list of possible
security flavors and choose what best suits its policies.
It is recommended that the client issue the SECINFO call protected
by a security triple that uses either rpc_gss_svc_integrity or
rpc_gss_svc_privacy service. The use of rpc_gss_svc_none would
allow an attacker in the middle to modify the SECINFO results such
that the client might select a weaker algorithm in the set allowed
by server, making the client and/or server vulnerable to further
attacks.
ERRORS
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_MOVED
NFS4ERR_NAMETOOLONG
NFS4ERR_NOENT
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOTDIR
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.31. Operation 33: SETATTR - Set Attributes
SYNOPSIS
(cfh), attrbits, attrvals -> -
ARGUMENT
struct SETATTR4args {
/* CURRENT_FH: target object */
stateid4 stateid;
fattr4 obj_attributes;
};
RESULT
struct SETATTR4res {
nfsstat4 status;
bitmap4 attrsset;
};
DESCRIPTION
The SETATTR operation changes one or more of the attributes of a
file system object. The new attributes are specified with a bitmap
and the attributes that follow the bitmap in bit order.
The stateid is necessary for SETATTRs that change the size of file
(modify the attribute object_size). This stateid represents a
record lock, share reservation, or delegation which must be valid
for the SETATTR to modify the file data.
On either success or failure of the operation, the server will
return the attrsset bitmask to represent what (if any) attributes
were successfully set.
IMPLEMENTATION
The file size attribute is used to request changes to the size of a
file. A value of 0 (zero) causes the file to be truncated, a value
less than the current size of the file causes data from new size to
the end of the file to be discarded, and a size greater than the
current size of the file causes logically zeroed data bytes to be
added to the end of the file. Servers are free to implement this
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using holes or actual zero data bytes. Clients should not make any
assumptions regarding a server's implementation of this feature,
beyond that the bytes returned will be zeroed. Servers must
support extending the file size via SETATTR.
SETATTR is not guaranteed atomic. A failed SETATTR may partially
change a file's attributes.
Changing the size of a file with SETATTR indirectly changes the
time_modify. A client must account for this as size changes can
result in data deletion.
If server and client times differ, programs that compare client
time to file times can break. A time maintenance protocol should be
used to limit client/server time skew.
If the server cannot successfully set all the attributes it must
return an NFS4ERR_INVAL error. If the server can only support 32
bit offsets and sizes, a SETATTR request to set the size of a file
to larger than can be represented in 32 bits will be rejected with
this same error.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_DENIED
NFS4ERR_DQUOT
NFS4ERR_EXPIRED
NFS4ERR_FBIG
NFS4ERR_FHEXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_JUKEBOX
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOSPC
NFS4ERR_NOTSUPP
NFS4ERR_PERM
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.32. Operation 34: SETCLIENTID - Negotiate Clientid
SYNOPSIS
seqid, client, callback -> clientid
ARGUMENT
struct SETCLIENTID4args {
seqid4 seqid;
bool confirm;
nfs_client_id4 client;
cb_client4 callback;
};
RESULT
struct SETCLIENTID4resok {
clientid4 clientid;
cookieverf4 setclientid_confirm;
};
union SETCLIENTID4res switch (nfsstat4 status) {
case NFS4_OK:
SETCLIENTID4resok resok4;
case NFS4ERR_CLID_INUSE:
clientaddr4 client_using;
default:
void;
};
DESCRIPTION
The SETCLIENTID operation introduces the ability of the client to
notify the server of its intention to use a particular client
identifier and verifier pair. Upon successful completion the
server will return a clientid which is used in subsequent file
locking requests. The client may request a confirmation of the
SETCLIENTID operation by setting the confirm argument field to
TRUE. The server will then return a confirmation cookie. The
client will use the SETCLIENTID_CONFIRM operation to return the
cookie and the next sequence id to the server.
The callback information provided in this operation will be used if
the client is granted a open delegation at a future point.
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Therefore, the client must correctly reflect the program and port
numbers for the callback program at the time SETCLIENTID is used.
IMPLEMENTATION
The server takes the verifier and client identification supplied
and searches for a match of the client identification. If no match
is found the server saves the principal/uid information along with
the verifier and client identification and returns a unique
clientid that is used as a shorthand reference to the supplied
information.
If the server finds matching client identification and a
corresponding match in principal/uid, the server releases all
locking state for the client and returns a new clientid.
The principal or principal to user identifier mapping is taken from
the credential presented in the RPC. As mentioned, the server will
use the credential and associated principal for the matching with
existing clientids. If the client is a traditional host based
client like a Unix NFS client, then the credential presented may be
the host credential. If the client is a user level client or light
weight client, the credential used may be the end user's
credential. The client should take care in choosing an appropriate
credential since denial of service attacks could be attempted by a
rogue client that has access to the credential.
ERRORS
NFS4ERR_CLID_INUSE
NFS4ERR_INVAL
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
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14.2.33. Operation 35: SETCLIENTID_CONFIRM - Confirm Clientid
SYNOPSIS
seqid, setclientid_confirm -> -
ARGUMENT
struct SETCLIENTID_CONFIRM4args {
seqid4seqid;
cookieverf4setclientid_confirm;
};
RESULT
struct SETCLIENTID_CONFIRM4res {
nfsstat4status;
};
DESCRIPTION
This operation is used by the client to confirm the results from a
previous call to SETCLIENTID. The client provides a sequence id
that is 1 (one) greater than the sequence id provided with the
corresponding SETCLIENTID operation. The client also provides the
server supplied opaque confirmation cookie. The server responds
with a simple status of success or failure.
IMPLEMENTATION
The SETCLIENTID_CONFIRM operation is optional and its use is
determined by the client when it sends the initial SETCLIENTID
operation to the server. If the server is told that the client
wants to confirm the SETCLIENTID operation, then all state
previously held by the client (if applicable) is held until the
receipt of the SETCLIENTID_CONFIRM is successful. The server
should choose a confirmation cookie value that is reasonably unique
for the client.
ERRORS
NFS4ERR_CLID_INUSE
NFS4ERR_INVAL
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NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
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14.2.34. Operation 36: VERIFY - Verify Same Attributes
SYNOPSIS
(cfh), attrbits, attrvals -> -
ARGUMENT
struct VERIFY4args {
/* CURRENT_FH: object */
bitmap4 attr_request;
fattr4 obj_attributes;
};
RESULT
struct VERIFY4res {
nfsstat4 status;
};
DESCRIPTION
The VERIFY operation is used to verify that attributes have a value
assumed by the client before proceeding with following operations
in the compound request. The current filehandle retains its value
after successful completion of the operation.
IMPLEMENTATION
One possible use of the VERIFY operation is the following compound
sequence. With this the client is attempting to verify that the
file being removed will match what the client expects to be
removed. This sequence can help prevent the unintended deletion of
a file.
PUTFH (directory filehandle)
LOOKUP (file name)
VERIFY (filehandle == fh)
PUTFH (directory filehandle)
REMOVE (file name)
This sequence does not prevent a second client from removing and
creating a new file in the middle of this sequence but it does help
avoid the unintended result.
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ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_FHEXPIRED
NFS4ERR_INVAL
NFS4ERR_JUKEBOX
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOTSUPP
NFS4ERR_RESOURCE
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_WRONGSEC
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14.2.35. Operation 37: WRITE - Write to File
SYNOPSIS
(cfh), offset, count, stability, stateid, data -> count, committed,
verifier
ARGUMENT
enum stable_how4 {
UNSTABLE4 = 0,
DATA_SYNC4 = 1,
FILE_SYNC4 = 2
};
struct WRITE4args {
/* CURRENT_FH: file */
stateid4 stateid;
offset4 offset;
stable_how4 stable;
opaque data<>;
};
RESULT
struct WRITE4resok {
count4 count;
stable_how4 committed;
writeverf4 verf;
};
union WRITE4res switch (nfsstat4 status) {
case NFS4_OK:
WRITE4resok resok4;
default:
void;
};
DESCRIPTION
The WRITE operation is used to write data to a regular file. The
target file is specified by the current filehandle. The offset
specifies the offset where the data should be written. An offset
of 0 (zero) specifies that the write should start at the beginning
of the file. The count represents the number of bytes of data that
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are to be written. If the count is 0 (zero), the WRITE will
succeed and return a count of 0 (zero) subject to permissions
checking. The server may choose to write fewer bytes than
requested by the client.
Part of the write request is a specification of how the write is to
be performed. The client specifies with the stable parameter the
method of how the data is to be processed by the server. If stable
is FILE_SYNC4, the server must commit the data written plus all
file system metadata to stable storage before returning results.
This corresponds to the NFS version 2 protocol semantics. Any
other behavior constitutes a protocol violation. If stable is
DATA_SYNC4, then the server must commit all of the data to stable
storage and enough of the metadata to retrieve the data before
returning. The server implementor is free to implement DATA_SYNC4
in the same fashion as FILE_SYNC4, but with a possible performance
drop. If stable is UNSTABLE4, the server is free to commit any
part of the data and the metadata to stable storage, including all
or none, before returning a reply to the client. There is no
guarantee whether or when any uncommitted data will subsequently be
committed to stable storage. The only guarantees made by the server
are that it will not destroy any data without changing the value of
verf and that it will not commit the data and metadata at a level
less than that requested by the client.
The stateid returned from a previous record lock or share
reservation request is provided as part of the argument. The
stateid is used by the server to verify that the associated lock is
still valid and to update lease timeouts for the client.
Upon successful completion, the following results are returned.
The count result is the number of bytes of data written to the
file. The server may write fewer bytes than requested. If so, the
actual number of bytes written starting at location, offset, is
returned.
The server also returns an indication of the level of commitment of
the data and metadata via committed. If the server committed all
data and metadata to stable storage, committed should be set to
FILE_SYNC4. If the level of commitment was at least as strong as
DATA_SYNC4, then committed should be set to DATA_SYNC4. Otherwise,
committed must be returned as UNSTABLE4. If stable was FILE4_SYNC,
then committed must also be FILE_SYNC4: anything else constitutes a
protocol violation. If stable was DATA_SYNC4, then committed may be
FILE_SYNC4 or DATA_SYNC4: anything else constitutes a protocol
violation. If stable was UNSTABLE4, then committed may be either
FILE_SYNC4, DATA_SYNC4, or UNSTABLE4.
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The final portion of the result is the write verifier, verf. The
write verifier is a cookie that the client can use to determine
whether the server has changed state between a call to WRITE and a
subsequent call to either WRITE or COMMIT. This cookie must be
consistent during a single instance of the NFS version 4 protocol
service and must be unique between instances of the NFS version 4
protocol server, where uncommitted data may be lost.
If a client writes data to the server with the stable argument set
to UNSTABLE4 and the reply yields a committed response of
DATA_SYNC4 or UNSTABLE4, the client will follow up some time in the
future with a COMMIT operation to synchronize outstanding
asynchronous data and metadata with the server's stable storage,
barring client error. It is possible that due to client crash or
other error that a subsequent COMMIT will not be received by the
server.
On success, the current filehandle retains its value.
IMPLEMENTATION
It is possible for the server to write fewer than count bytes of
data. In this case, the server should not return an error unless
no data was written at all. If the server writes less than count
bytes, the client should issue another WRITE to write the remaining
data.
It is assumed that the act of writing data to a file will cause the
time_modified of the file to be updated. However, the
time_modified of the file should not be changed unless the contents
of the file are changed. Thus, a WRITE request with count set to 0
should not cause the time_modified of the file to be updated.
The definition of stable storage has been historically a point of
contention. The following expected properties of stable storage
may help in resolving design issues in the implementation. Stable
storage is persistent storage that survives:
1. Repeated power failures.
2. Hardware failures (of any board, power supply, etc.).
3. Repeated software crashes, including reboot cycle.
This definition does not address failure of the stable storage
module itself.
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The verifier is defined to allow a client to detect different
instances of an NFS version 4 protocol server over which cached,
uncommitted data may be lost. In the most likely case, the verifier
allows the client to detect server reboots. This information is
required so that the client can safely determine whether the server
could have lost cached data. If the server fails unexpectedly and
the client has uncommitted data from previous WRITE requests (done
with the stable argument set to UNSTABLE4 and in which the result
committed was returned as UNSTABLE4 as well) it may not have
flushed cached data to stable storage. The burden of recovery is on
the client and the client will need to retransmit the data to the
server.
A suggested verifier would be to use the time that the server was
booted or the time the server was last started (if restarting the
server without a reboot results in lost buffers).
The committed field in the results allows the client to do more
effective caching. If the server is committing all WRITE requests
to stable storage, then it should return with committed set to
FILE_SYNC4, regardless of the value of the stable field in the
arguments. A server that uses an NVRAM accelerator may choose to
implement this policy. The client can use this to increase the
effectiveness of the cache by discarding cached data that has
already been committed on the server.
Some implementations may return NFS4ERR_NOSPC instead of
NFS4ERR_DQUOT when a user's quota is exceeded.
ERRORS
NFS4ERR_ACCES
NFS4ERR_BADHANDLE
NFS4ERR_BAD_STATEID
NFS4ERR_DENIED
NFS4ERR_DQUOT
NFS4ERR_EXPIRED
NFS4ERR_FBIG
NFS4ERR_FHEXPIRED
NFS4ERR_GRACE
NFS4ERR_INVAL
NFS4ERR_IO
NFS4ERR_JUKEBOX
NFS4ERR_LOCKED
NFS4ERR_MOVED
NFS4ERR_NOFILEHANDLE
NFS4ERR_NOSPC
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NFS4ERR_OLD_STATEID
NFS4ERR_RESOURCE
NFS4ERR_ROFS
NFS4ERR_SERVERFAULT
NFS4ERR_STALE
NFS4ERR_STALE_STATEID
NFS4ERR_WRONGSEC
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15. NFS Version 4 Callback Procedures
The procedures used for callbacks are defined in the following
sections. In the interest of clarity, the terms "client" and
"server" refer to NFS clients and servers, despite the fact that for
an individual callback RPC, the sense of these terms would be
precisely the opposite.
15.1. Procedure 0: CB_NULL - No Operation
SYNOPSIS
<null>
ARGUMENT
void;
RESULT
void;
DESCRIPTION
Standard NULL procedure. Void argument, void response. This
procedure has no functionality associated with it.
ERRORS
None.
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15.2. Procedure 1: CB_COMPOUND - Compound Operations
SYNOPSIS
compoundargs -> compoundres
ARGUMENT
enum nfs_cb_opnum4 {
OP_CB_GETATTR = 3,
OP_CB_RECALL = 4
};
union nfs_cb_argop4 switch (unsigned argop) {
case OP_CB_GETATTR: CB_GETATTR4args opcbgetattr;
case OP_CB_RECALL: CB_RECALL4args opcbrecall;
};
struct CB_COMPOUND4args {
utf8string tag;
uint32_t minorversion;
nfs_cb_argop4 argarray<>;
};
RESULT
union nfs_cb_resop4 switch (unsigned resop){
case OP_CB_GETATTR: CB_GETATTR4res opcbgetattr;
case OP_CB_RECALL: CB_RECALL4res opcbrecall;
};
struct CB_COMPOUND4args {
utf8string tag;
uint32_t minorversion;
nfs_cb_argop4 argarray<>;
};
struct CB_COMPOUND4res {
nfsstat4 status;
utf8string tag;
nfs_cb_resop4 resarray<>;
};
DESCRIPTION
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The CB_COMPOUND procedure is used to combine one or more of the
callback procedures into a single RPC request. The main callback
RPC program has two main procedures: CB_NULL and CB_COMPOUND. All
other operations use the CB_COMPOUND procedure as a wrapper.
In the processing of the CB_COMPOUND procedure, the client may find
that it does not have the available resources to execute any or all
of the operations within the CB_COMPOUND sequence. In this case,
the error NFS4ERR_RESOURCE will be returned for the particular
operation within the CB_COMPOUND procedure where the resource
exhaustion occurred. This assumes that all previous operations
within the CB_COMPOUND sequence have been evaluated successfully.
Contained within the CB_COMPOUND results is a 'status' field. This
status must be equivalent to the status of the last operation that
was executed within the CB_COMPOUND procedure. Therefore, if an
operation incurred an error then the 'status' value will be the
same error value as is being returned for the operation that
failed.
IMPLEMENTATION
The CB_COMPOUND procedure is used to combine individual operations
into a single RPC request. The client interprets each of the
operations in turn. If an operation is executed by the client and
the status of that operation is NFS4_OK, then the next operation in
the CB_COMPOUND procedure is executed. The client continues this
process until there are no more operations to be executed or one of
the operations has a status value other than NFS4_OK.
ERRORS
All errors defined in the protocol
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15.2.1. Operation 3: CB_GETATTR - Get Attributes
SYNOPSIS
fh, attrbits -> attrbits, attrvals
ARGUMENT
struct CB_GETATTR4args {
nfs_fh4 fh;
bitmap4 attr_request;
};
RESULT
struct CB_GETATTR4resok {
fattr4 obj_attributes;
};
union CB_GETATTR4res switch (nfsstat4 status) {
case NFS4_OK:
CB_GETATTR4resok resok4;
default:
void;
};
DESCRIPTION
The CB_GETATTR operation is used to obtain the attributes modified
by an open delegate to allow the server to respond to GETATTR
requests for a file which is the subject of an open delegation.
IMPLEMENTATION
The client returns attrbits and the associated attribute values
only for attributes that it may change (change, time_modify,
object_size). It may further limit the response to attributes that
it has in fact changed during the scope of the delegation.
ERRORS
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NFS4ERR_FHEXPIRED
NFS4ERR_RESOURCE
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15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation
SYNOPSIS
stateid, truncate, fh -> status
ARGUMENT
struct CB_RECALL4args {
stateid4 stateid;
bool truncate;
nfs_fh4 fh;
};
RESULT
struct CB_RECALL4res {
nfsstat4 status;
};
DESCRIPTION
The CB_RECALL operation is used to begin the process of recalling
an open delegation and returning it to the server.
The truncate flag is used to optimize recall for a file which is
about to be truncated to zero. When it is set, the client is freed
of obligation to propagate modified data for the file to the
server, since this data is irrelevant.
IMPLEMENTATION
The client should reply to the callback immediately. Replying does
not complete the recall. The recall is not complete until the
delegation is returned using a DELEGRETURN.
ERRORS
NFS4ERR_FHEXPIRED
NFS4ERR_RESOURCE
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16. Security Considerations
The major security feature to consider is the authentication of the
user making the request of NFS service. Consideration should also be
given to the integrity and privacy of this NFS request. These
specific issues are discussed as part of the section on "RPC and
Security Flavor".
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17. RPC definition file
/*
* Copyright (C) The Internet Society (1998,1999).
* All Rights Reserved.
*/
/*
* nfs4_prot.x
*
*/
%#pragma ident "@(#)nfs4_prot.x 1.70 99/12/16"
/*
* Basic typedefs for RFC 1832 data type definitions
*/
typedef int int32_t;
typedef unsigned int uint32_t;
typedef hyper int64_t;
typedef unsigned hyper uint64_t;
/*
* Sizes
*/
const NFS4_FHSIZE = 128;
const NFS4_CREATEVERFSIZE = 8;
const NFS4_COOKIEVERFSIZE = 8;
/*
* File types
*/
enum nfs_ftype4 {
NF4REG = 1, /* Regular File */
NF4DIR = 2, /* Directory */
NF4BLK = 3, /* Special File - block device */
NF4CHR = 4, /* Special File - character device */
NF4LNK = 5, /* Symbolic Link */
NF4SOCK = 6, /* Special File - socket */
NF4FIFO = 7, /* Special File - fifo */
NF4ATTRDIR = 8, /* Attribute Directory */
NF4NAMEDATTR = 9 /* Named Attribute */
};
/*
* Error status
*/
enum nfsstat4 {
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NFS4_OK = 0,
NFS4ERR_PERM = 1,
NFS4ERR_NOENT = 2,
NFS4ERR_IO = 5,
NFS4ERR_NXIO = 6,
NFS4ERR_ACCES = 13,
NFS4ERR_EXIST = 17,
NFS4ERR_XDEV = 18,
NFS4ERR_NODEV = 19,
NFS4ERR_NOTDIR = 20,
NFS4ERR_ISDIR = 21,
NFS4ERR_INVAL = 22,
NFS4ERR_FBIG = 27,
NFS4ERR_NOSPC = 28,
NFS4ERR_ROFS = 30,
NFS4ERR_MLINK = 31,
NFS4ERR_NAMETOOLONG = 63,
NFS4ERR_NOTEMPTY = 66,
NFS4ERR_DQUOT = 69,
NFS4ERR_STALE = 70,
NFS4ERR_BADHANDLE = 10001,
NFS4ERR_NOT_SYNC = 10002,
NFS4ERR_BAD_COOKIE = 10003,
NFS4ERR_NOTSUPP = 10004,
NFS4ERR_TOOSMALL = 10005,
NFS4ERR_SERVERFAULT = 10006,
NFS4ERR_BADTYPE = 10007,
NFS4ERR_JUKEBOX = 10008,
NFS4ERR_SAME = 10009,/* nverify says attrs same */
NFS4ERR_DENIED = 10010,/* lock unavailable */
NFS4ERR_EXPIRED = 10011,/* lock lease expired */
NFS4ERR_LOCKED = 10012,/* I/O failed due to lock */
NFS4ERR_GRACE = 10013,/* in grace period */
NFS4ERR_FHEXPIRED = 10014,/* file handle expired */
NFS4ERR_SHARE_DENIED = 10015,/* share reserve denied */
NFS4ERR_WRONGSEC = 10016,/* wrong security flavor */
NFS4ERR_CLID_INUSE = 10017,/* clientid in use */
NFS4ERR_RESOURCE = 10018,/* resource exhaustion */
NFS4ERR_MOVED = 10019,/* filesystem relocated */
NFS4ERR_NOFILEHANDLE = 10020,/* current FH is not set */
NFS4ERR_MINOR_VERS_MISMATCH = 10021,/* minor vers not supp */
NFS4ERR_STALE_CLIENTID = 10022,
NFS4ERR_STALE_STATEID = 10023,
NFS4ERR_OLD_STATEID = 10024,
NFS4ERR_BAD_STATEID = 10025,
NFS4ERR_BAD_SEQID = 10026,
NFS4ERR_NOT_CONFIRMED = 10027
};
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/*
* Basic data types
*/
typedef uint32_t bitmap4<>;
typedef uint64_t offset4;
typedef uint32_t count4;
typedef uint64_t length4;
typedef uint64_t clientid4;
typedef uint64_t stateid4;
typedef uint32_t seqid4;
typedef opaque utf8string<>;
typedef utf8string component4;
typedef component4 pathname4<>;
typedef uint64_t nfs_lockid4;
typedef uint64_t nfs_cookie4;
typedef utf8string linktext4;
typedef opaque sec_oid4<>;
typedef uint32_t qop4;
typedef uint32_t mode4;
typedef uint32_t writeverf4;
typedef opaque createverf4[NFS4_CREATEVERFSIZE];
typedef opaque cookieverf4[NFS4_COOKIEVERFSIZE];
/*
* Timeval
*/
struct nfstime4 {
int64_t seconds;
uint32_t nseconds;
};
/*
* File access handle
*/
typedef opaque nfs_fh4<NFS4_FHSIZE>;
/*
* File attribute definitions
*/
/*
* FSID structure for major/minor
*/
struct fsid4 {
uint64_t major;
uint64_t minor;
};
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/*
* Filesystem locations attribute for relocation/migration
*/
struct fs_location4 {
utf8string server<>;
pathname4 rootpath;
};
struct fs_locations4 {
pathname4 fs_root;
fs_location4 locations<>;
};
/*
* Various Access Control Entry definitions
*/
/*
* Mask that indicates which Access Control Entries are supported.
* Values for the fattr4_aclsupport attribute.
*/
const ACL4_SUPPORT_ALLOW_ACL = 0x00000001;
const ACL4_SUPPORT_DENY_ACL = 0x00000002;
const ACL4_SUPPORT_AUDIT_ACL = 0x00000004;
const ACL4_SUPPORT_ALARM_ACL = 0x00000008;
typedef uint32_t acetype4;
/*
* acetype4 values, others can be added as needed.
*/
const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;
const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;
const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002;
const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003;
/*
* ACE flag
*/
typedef uint32_t aceflag4;
/*
* ACE flag values
*/
const ACE4_FILE_INHERIT_ACE = 0x00000001;
const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002;
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const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004;
const ACE4_INHERIT_ONLY_ACE = 0x00000008;
const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010;
const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020;
const ACE4_IDENTIFIER_GROUP = 0x00000040;
/*
* ACE mask
*/
typedef uint32_t acemask4;
/*
* ACE mask values
*/
const ACE4_READ_DATA = 0x00000001;
const ACE4_LIST_DIRECTORY = 0x00000001;
const ACE4_WRITE_DATA = 0x00000002;
const ACE4_ADD_FILE = 0x00000002;
const ACE4_APPEND_DATA = 0x00000004;
const ACE4_ADD_SUBDIRECTORY = 0x00000004;
const ACE4_READ_STREAMS = 0x00000008;
const ACE4_WRITE_STREAMS = 0x00000010;
const ACE4_EXECUTE = 0x00000020;
const ACE4_DELETE_CHILD = 0x00000040;
const ACE4_READ_ATTRIBUTES = 0x00000080;
const ACE4_WRITE_ATTRIBUTES = 0x00000100;
const ACE4_DELETE = 0x00010000;
const ACE4_READ_ACL = 0x00020000;
const ACE4_WRITE_ACL = 0x00040000;
const ACE4_WRITE_OWNER = 0x00080000;
const ACE4_SYNCHRONIZE = 0x00100000;
/*
* ACE4_GENERIC_READ -- defined as combination of
* ACE4_READ_ACL |
* ACE4_READ_DATA |
* ACE4_READ_ATTRIBUTES |
* ACE4_SYNCHRONIZE
*/
const ACE4_GENERIC_READ = 0x00120081;
/*
* ACE4_GENERIC_WRITE -- defined as combination of
* ACE4_READ_ACL |
* ACE4_WRITE_DATA |
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* ACE4_WRITE_ATTRIBUTES |
* ACE4_WRITE_ACL |
* ACE4_APPEND_DATA |
* ACE4_SYNCHRONIZE
*/
const ACE4_GENERIC_WRITE = 0x00160102;
/*
* ACE4_GENERIC_EXECUTE -- defined as combination of
* ACE4_READ_ACL
* ACE4_READ_ATTRIBUTES
* ACE4_EXECUTE
* ACE4_SYNCHRONIZE
*/
const ACE4_GENERIC_EXECUTE = 0x001200A0;
/*
* Access Control Entry definition
*/
struct nfsace4 {
acetype4 type;
aceflag4 flag;
acemask4 access_mask;
utf8string who;
};
/*
* Special data/attribute associated with
* file types NF4BLK and NF4CHR.
*/
struct specdata4 {
uint32_t specdata1;
uint32_t specdata2;
};
/*
* Values for fattr4_fh_expire_type
*/
const FH4_PERSISTENT = 0x00000000;
const FH4_NOEXPIRE_WITH_OPEN = 0x00000001;
const FH4_VOLATILE_ANY = 0x00000002;
const FH4_VOL_MIGRATION = 0x00000004;
const FH4_VOL_RENAME = 0x00000008;
typedef bitmap4 fattr4_supported_attrs;
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typedef nfs_ftype4 fattr4_type;
typedef uint32_t fattr4_fh_expire_type;
typedef uint64_t fattr4_change;
typedef uint64_t fattr4_size;
typedef bool fattr4_link_support;
typedef bool fattr4_symlink_support;
typedef bool fattr4_named_attr;
typedef fsid4 fattr4_fsid;
typedef bool fattr4_unique_handles;
typedef uint32_t fattr4_lease_time;
typedef nfsstat4 fattr4_rdattr_error;
typedef nfsace4 fattr4_acl<>;
typedef uint32_t fattr4_aclsupport;
typedef bool fattr4_archive;
typedef bool fattr4_cansettime;
typedef bool fattr4_case_insensitive;
typedef bool fattr4_case_preserving;
typedef bool fattr4_chown_restricted;
typedef uint64_t fattr4_fileid;
typedef uint64_t fattr4_files_avail;
typedef nfs_fh4 fattr4_filehandle;
typedef uint64_t fattr4_files_free;
typedef uint64_t fattr4_files_total;
typedef fs_locations4 fattr4_fs_locations;
typedef bool fattr4_hidden;
typedef bool fattr4_homogeneous;
typedef uint64_t fattr4_maxfilesize;
typedef uint32_t fattr4_maxlink;
typedef uint32_t fattr4_maxname;
typedef uint64_t fattr4_maxread;
typedef uint64_t fattr4_maxwrite;
typedef utf8string fattr4_mimetype;
typedef mode4 fattr4_mode;
typedef bool fattr4_no_trunc;
typedef uint32_t fattr4_numlinks;
typedef utf8string fattr4_owner;
typedef utf8string fattr4_owner_group;
typedef uint64_t fattr4_quota_hard;
typedef uint64_t fattr4_quota_soft;
typedef uint64_t fattr4_quota_used;
typedef specdata4 fattr4_rawdev;
typedef uint64_t fattr4_space_avail;
typedef uint64_t fattr4_space_free;
typedef uint64_t fattr4_space_total;
typedef uint64_t fattr4_space_used;
typedef bool fattr4_system;
typedef nfstime4 fattr4_time_access;
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typedef nfstime4 fattr4_time_backup;
typedef nfstime4 fattr4_time_create;
typedef nfstime4 fattr4_time_delta;
typedef nfstime4 fattr4_time_metadata;
typedef nfstime4 fattr4_time_modify;
typedef utf8string fattr4_version;
typedef nfstime4 fattr4_volatility;
/*
* Mandatory Attributes
*/
const FATTR4_SUPPORTED_ATTRS = 0;
const FATTR4_TYPE = 1;
const FATTR4_PERSISTENT_FH = 2;
const FATTR4_CHANGE = 3;
const FATTR4_SIZE = 4;
const FATTR4_LINK_SUPPORT = 5;
const FATTR4_SYMLINK_SUPPORT = 6;
const FATTR4_NAMED_ATTR = 7;
const FATTR4_FSID = 8;
const FATTR4_UNIQUE_HANDLES = 9;
const FATTR4_LEASE_TIME = 10;
const FATTR4_RDATTR_ERROR = 11;
/*
* Recommended Attributes
*/
const FATTR4_ACL = 12;
const FATTR4_ARCHIVE = 13;
const FATTR4_CANSETTIME = 14;
const FATTR4_CASE_INSENSITIVE = 15;
const FATTR4_CASE_PRESERVING = 16;
const FATTR4_CHOWN_RESTRICTED = 17;
const FATTR4_FILEHANDLE = 18;
const FATTR4_FILEID = 19;
const FATTR4_FILES_AVAIL = 20;
const FATTR4_FILES_FREE = 21;
const FATTR4_FILES_TOTAL = 22;
const FATTR4_FS_LOCATIONS = 23;
const FATTR4_HIDDEN = 24;
const FATTR4_HOMOGENEOUS = 25;
const FATTR4_MAXFILESIZE = 26;
const FATTR4_MAXLINK = 27;
const FATTR4_MAXNAME = 28;
const FATTR4_MAXREAD = 29;
const FATTR4_MAXWRITE = 30;
const FATTR4_MIMETYPE = 31;
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const FATTR4_MODE = 32;
const FATTR4_NO_TRUNC = 33;
const FATTR4_NUMLINKS = 34;
const FATTR4_OWNER = 35;
const FATTR4_OWNER_GROUP = 36;
const FATTR4_QUOTA_HARD = 37;
const FATTR4_QUOTA_SOFT = 38;
const FATTR4_QUOTA_USED = 39;
const FATTR4_RAWDEV = 40;
const FATTR4_SPACE_AVAIL = 41;
const FATTR4_SPACE_FREE = 42;
const FATTR4_SPACE_TOTAL = 43;
const FATTR4_SPACE_USED = 44;
const FATTR4_SYSTEM = 45;
const FATTR4_TIME_ACCESS = 46;
const FATTR4_TIME_BACKUP = 47;
const FATTR4_TIME_CREATE = 48;
const FATTR4_TIME_DELTA = 49;
const FATTR4_TIME_METADATA = 50;
const FATTR4_TIME_MODIFY = 51;
const FATTR4_VERSION = 52;
const FATTR4_VOLATILITY = 53;
typedef opaque attrlist4<>;
/*
* File attribute container
*/
struct fattr4 {
bitmap4 attrmask;
attrlist4 attr_vals;
};
/*
* Change info for the client
*/
struct change_info4 {
bool atomic;
fattr4_change before;
fattr4_change after;
};
struct clientaddr4 {
/* see struct rpcb in RFC 1833 */
string r_netid<>; /* network id */
string r_addr<>; /* universal address */
};
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/*
* Callback program info as provided by the client
*/
struct cb_client4 {
unsigned int cb_program;
clientaddr4 cb_location;
};
/*
* Client ID
*/
struct nfs_client_id4 {
opaque verifier[4];
opaque id<>;
};
struct nfs_lockowner4 {
clientid4 clientid;
opaque owner<>;
};
enum nfs_lock_type4 {
READ_LT = 1,
WRITE_LT = 2,
READW_LT = 3, /* blocking read */
WRITEW_LT = 4 /* blocking write */
};
/*
* ACCESS: Check access permission
*/
const ACCESS4_READ = 0x00000001;
const ACCESS4_LOOKUP = 0x00000002;
const ACCESS4_MODIFY = 0x00000004;
const ACCESS4_EXTEND = 0x00000008;
const ACCESS4_DELETE = 0x00000010;
const ACCESS4_EXECUTE = 0x00000020;
struct ACCESS4args {
/* CURRENT_FH: object */
uint32_t access;
};
struct ACCESS4resok {
uint32_t supported;
uint32_t access;
};
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union ACCESS4res switch (nfsstat4 status) {
case NFS4_OK:
ACCESS4resok resok4;
default:
void;
};
/*
* CLOSE: Close a file and release share locks
*/
struct CLOSE4args {
/* CURRENT_FH: object */
stateid4 stateid;
};
union CLOSE4res switch (nfsstat4 status) {
case NFS4_OK:
stateid4 stateid;
default:
void;
};
/*
* COMMIT: Commit cached data on server to stable storage
*/
struct COMMIT4args {
/* CURRENT_FH: file */
offset4 offset;
count4 count;
};
struct COMMIT4resok {
writeverf4 verf;
};
union COMMIT4res switch (nfsstat4 status) {
case NFS4_OK:
COMMIT4resok resok4;
default:
void;
};
/*
* CREATE: Create a file
*/
union createtype4 switch (nfs_ftype4 type) {
case NF4LNK:
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linktext4 linkdata;
case NF4BLK:
case NF4CHR:
specdata4 devdata;
case NF4SOCK:
case NF4FIFO:
case NF4DIR:
case NF4ATTRDIR:
void;
};
struct CREATE4args {
/* CURRENT_FH: directory for creation */
component4 objname;
createtype4 objtype;
};
struct CREATE4resok {
change_info4 cinfo;
};
union CREATE4res switch (nfsstat4 status) {
case NFS4_OK:
CREATE4resok resok4;
default:
void;
};
/*
* DELEGPURGE: Purge Delegations Awaiting Recovery
*/
struct DELEGPURGE4args {
clientid4 clientid;
};
struct DELEGPURGE4res {
nfsstat4 status;
};
/*
* DELEGRETURN: Return a delegation
*/
struct DELEGRETURN4args {
stateid4 stateid;
};
struct DELEGRETURN4res {
nfsstat4 status;
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};
/*
* GETATTR: Get file attributes
*/
struct GETATTR4args {
/* CURRENT_FH: directory or file */
bitmap4 attr_request;
};
struct GETATTR4resok {
fattr4 obj_attributes;
};
union GETATTR4res switch (nfsstat4 status) {
case NFS4_OK:
GETATTR4resok resok4;
default:
void;
};
/*
* GETFH: Get current filehandle
*/
struct GETFH4resok {
nfs_fh4 object;
};
union GETFH4res switch (nfsstat4 status) {
case NFS4_OK:
GETFH4resok resok4;
default:
void;
};
/*
* LINK: Create link to an object
*/
struct LINK4args {
/* SAVED_FH: source object */
/* CURRENT_FH: target directory */
component4 newname;
};
struct LINK4resok {
change_info4 cinfo;
};
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union LINK4res switch (nfsstat4 status) {
case NFS4_OK:
LINK4resok resok4;
default:
void;
};
/*
* LOCK/LOCKT/LOCKU: Record lock management
*/
struct LOCK4args {
/* CURRENT_FH: file */
nfs_lock_type4 locktype;
seqid4 seqid;
bool reclaim;
stateid4 stateid;
offset4 offset;
length4 length;
};
union LOCK4res switch (nfsstat4 status) {
case NFS4_OK:
stateid4 stateid;
default:
void;
};
struct LOCKT4args {
/* CURRENT_FH: file */
nfs_lock_type4 locktype;
nfs_lockowner4 owner;
offset4 offset;
length4 length;
};
union LOCKT4res switch (nfsstat4 status) {
case NFS4ERR_DENIED:
nfs_lockowner4 owner;
case NFS4_OK:
void;
default:
void;
};
struct LOCKU4args {
/* CURRENT_FH: file */
nfs_lock_type4 type;
seqid4 seqid;
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stateid4 stateid;
offset4 offset;
length4 length;
};
union LOCKU4res switch (nfsstat4 status) {
case NFS4_OK:
stateid4 stateid;
default:
void;
};
/*
* LOOKUP: Lookup filename
*/
struct LOOKUP4args {
/* CURRENT_FH: directory */
pathname4 path;
};
struct LOOKUP4res {
/* CURRENT_FH: object */
nfsstat4 status;
};
/*
* LOOKUPP: Lookup parent directory
*/
struct LOOKUPP4res {
/* CURRENT_FH: directory */
nfsstat4 status;
};
/*
* NVERIFY: Verify attributes different
*/
struct NVERIFY4args {
/* CURRENT_FH: object */
bitmap4 attr_request;
fattr4 obj_attributes;
};
struct NVERIFY4res {
nfsstat4 status;
};
/*
* Various definitions for OPEN
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*/
enum createmode4 {
UNCHECKED4 = 0,
GUARDED4 = 1,
EXCLUSIVE4 = 2
};
union createhow4 switch (createmode4 mode) {
case UNCHECKED4:
case GUARDED4:
fattr4 createattrs;
case EXCLUSIVE4:
createverf4 verf;
};
enum opentype4 {
OPEN4_NOCREATE = 0,
OPEN4_CREATE = 1
};
union openflag4 switch (opentype4 opentype) {
case OPEN4_CREATE:
createhow4 how;
default:
void;
};
/* Next definitions used for OPEN delegation */
enum limit_by4 {
NFS_LIMIT_SIZE = 1,
NFS_LIMIT_BLOCKS = 2
/* others as needed */
};
struct nfs_modified_limit4 {
uint32_t num_blocks;
uint32_t bytes_per_block;
};
union nfs_space_limit4 switch (limit_by4 limitby) {
/* limit specified as file size */
case NFS_LIMIT_SIZE:
uint64_t filesize;
/* limit specified by number of blocks */
case NFS_LIMIT_BLOCKS:
nfs_modified_limit4 mod_blocks;
} ;
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/*
* Share Access and Deny constants for open argument
*/
const OPEN4_SHARE_ACCESS_READ = 0x00000001;
const OPEN4_SHARE_ACCESS_WRITE = 0x00000002;
const OPEN4_SHARE_ACCESS_BOTH = 0x00000003;
const OPEN4_SHARE_DENY_NONE = 0x00000000;
const OPEN4_SHARE_DENY_READ = 0x00000001;
const OPEN4_SHARE_DENY_WRITE = 0x00000002;
const OPEN4_SHARE_DENY_BOTH = 0x00000003;
enum open_delegation_type4 {
OPEN_DELEGATE_NONE = 0,
OPEN_DELEGATE_READ = 1,
OPEN_DELEGATE_WRITE = 2
};
enum open_claim_type4 {
CLAIM_NULL = 0,
CLAIM_PREVIOUS = 1,
CLAIM_DELEGATE_CUR = 2,
CLAIM_DELEGATE_PREV = 3
};
struct open_claim_delegate_cur4 {
pathname4 file;
stateid4 delegate_stateid;
};
union open_claim4 switch (open_claim_type4 claim) {
/*
* No special rights to file. Ordinary OPEN of the specified file.
*/
case CLAIM_NULL:
/* CURRENT_FH: directory */
pathname4 file;
/*
* Right to the file established by an open previous to server
* reboot. File identified by filehandle obtained at that time
* rather than by name.
*/
case CLAIM_PREVIOUS:
/* CURRENT_FH: file being reclaimed */
uint32_t delegate_type;
/*
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* Right to file based on a delegation granted by the server.
* File is specified by name.
*/
case CLAIM_DELEGATE_CUR:
/* CURRENT_FH: directory */
open_claim_delegate_cur4 delegate_cur_info;
/* Right to file based on a delegation granted to a previous boot
* instance of the client. File is specified by name.
*/
case CLAIM_DELEGATE_PREV:
/* CURRENT_FH: directory */
pathname4 file_delegate_prev;
};
/*
* OPEN: Open a file, potentially receiving an open delegation
*/
struct OPEN4args {
open_claim4 claim;
openflag4 openhow;
nfs_lockowner4 owner;
seqid4 seqid;
uint32_t share_access;
uint32_t share_deny;
};
/*
* Result flags
*/
/* Mandatory locking is in effect for this file. */
const OPEN4_RESULT_MLOCK = 0x00000001;
struct open_read_delegation4 {
stateid4 stateid; /* Stateid for delegation*/
bool recall; /* Pre-recalled flag for
delegations obtained
by reclaim
(CLAIM_PREVIOUS) */
nfsace4 permissions; /* Defines users who don't
need an ACCESS call to
open for read */
};
struct open_write_delegation4 {
stateid4 stateid; /* Stateid for delegation
be flushed to the server
on close. */
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bool recall; /* Pre-recalled flag for
delegations obtained
by reclaim
(CLAIM_PREVIOUS) */
nfs_space_limit4 space_limit; /* Defines condition that
the client must check to
determine whether the
file needs to be flushed
to the server on close.
*/
nfsace4 permissions; /* Defines users who don't
need an ACCESS call as
part of a delegated
open. */
};
union open_delegation4
switch (open_delegation_type4 delegation_type) {
case OPEN_DELEGATE_NONE:
void;
case OPEN_DELEGATE_READ:
open_read_delegation4 read;
case OPEN_DELEGATE_WRITE:
open_write_delegation4 write;
};
struct OPEN4resok {
stateid4 stateid; /* Stateid for open */
uint32_t rflags; /* Result flags */
cookieverf4 open_confirm; /* OPEN_CONFIRM verifier */
open_delegation4 delegation; /* Info on any open
delegation */
};
union OPEN4res switch (nfsstat4 status) {
case NFS4_OK:
/* CURRENT_FH: opened file */
OPEN4resok result;
default:
void;
};
/*
* OPENATTR: open named attributes directory
*/
struct OPENATTR4res {
/* CURRENT_FH: name attr directory*/
nfsstat4 status;
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};
struct OPEN_CONFIRM4args {
/* CURRENT_FH: opened file */
seqid4 seqid;
cookieverf4 open_confirm; /* OPEN_CONFIRM verifier */
};
struct OPEN_CONFIRM4resok {
stateid4 stateid;
};
union OPEN_CONFIRM4res switch (nfsstat4 status) {
case NFS4_OK:
OPEN_CONFIRM4resok resok4;
default:
void;
};
/*
* PUTFH: Set current filehandle
*/
struct PUTFH4args {
nfs_fh4 object;
};
struct PUTFH4res {
/* CURRENT_FH: */
nfsstat4 status;
};
/*
* PUTPUBFH: Set public filehandle
*/
struct PUTPUBFH4res {
/* CURRENT_FH: public fh */
nfsstat4 status;
};
/*
* PUTROOTFH: Set root filehandle
*/
struct PUTROOTFH4res {
/* CURRENT_FH: root fh */
nfsstat4 status;
};
/*
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* READ: Read from file
*/
struct READ4args {
/* CURRENT_FH: file */
stateid4 stateid;
offset4 offset;
count4 count;
};
struct READ4resok {
bool eof;
opaque data<>;
};
union READ4res switch (nfsstat4 status) {
case NFS4_OK:
READ4resok resok4;
default:
void;
};
/*
* READDIR: Read directory
*/
struct READDIR4args {
/* CURRENT_FH: directory */
nfs_cookie4 cookie;
cookieverf4 cookieverf;
count4 dircount;
count4 maxcount;
bitmap4 attr_request;
};
struct entry4 {
nfs_cookie4 cookie;
component4 name;
fattr4 attrs;
entry4 *nextentry;
};
struct dirlist4 {
entry4 *entries;
bool eof;
};
struct READDIR4resok {
cookieverf4 cookieverf;
dirlist4 reply;
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};
union READDIR4res switch (nfsstat4 status) {
case NFS4_OK:
READDIR4resok resok4;
default:
void;
};
/*
* READLINK: Read symbolic link
*/
struct READLINK4resok {
linktext4 link;
};
union READLINK4res switch (nfsstat4 status) {
case NFS4_OK:
READLINK4resok resok4;
default:
void;
};
/*
* REMOVE: Remove filesystem object
*/
struct REMOVE4args {
/* CURRENT_FH: directory */
component4 target;
};
struct REMOVE4resok {
change_info4 cinfo;
};
union REMOVE4res switch (nfsstat4 status) {
case NFS4_OK:
REMOVE4resok resok4;
default:
void;
};
/*
* RENAME: Rename directory entry
*/
struct RENAME4args {
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/* SAVED_FH: source directory */
component4 oldname;
/* CURRENT_FH: target directory */
component4 newname;
};
struct RENAME4resok {
change_info4 source_cinfo;
change_info4 target_cinfo;
};
union RENAME4res switch (nfsstat4 status) {
case NFS4_OK:
RENAME4resok resok4;
default:
void;
};
/*
* RENEW: Renew a Lease
*/
struct RENEW4args {
stateid4 stateid;
};
struct RENEW4res {
nfsstat4 status;
};
/*
* RESTOREFH: Restore saved filehandle
*/
struct RESTOREFH4res {
/* CURRENT_FH: value of saved fh */
nfsstat4 status;
};
/*
* SAVEFH: Save current filehandle
*/
struct SAVEFH4res {
/* SAVED_FH: value of current fh */
nfsstat4 status;
};
/*
* SECINFO: Obtain Available Security Mechanisms
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*/
struct SECINFO4args {
/* CURRENT_FH: */
component4 name;
};
/*
* From RFC 2203
*/
enum rpc_gss_svc_t {
RPC_GSS_SVC_NONE = 1,
RPC_GSS_SVC_INTEGRITY = 2,
RPC_GSS_SVC_PRIVACY = 3
};
struct rpcsec_gss_info {
sec_oid4 oid;
qop4 qop;
rpc_gss_svc_t service;
};
struct secinfo4 {
uint32_t flavor;
/* null for AUTH_SYS, AUTH_NONE;
contains rpcsec_gss_info for
RPCSEC_GSS. */
opaque flavor_info<>;
};
typedef secinfo4 SECINFO4resok<>;
union SECINFO4res switch (nfsstat4 status) {
case NFS4_OK:
SECINFO4resok resok4;
default:
void;
};
/*
* SETATTR: Set attributes
*/
struct SETATTR4args {
/* CURRENT_FH: target object */
stateid4 stateid;
fattr4 obj_attributes;
};
struct SETATTR4res {
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nfsstat4 status;
bitmap4 attrsset;
};
/*
* SETCLIENTID
*/
struct SETCLIENTID4args {
seqid4 seqid;
bool confirm;
nfs_client_id4 client;
cb_client4 callback;
};
struct SETCLIENTID4resok {
clientid4 clientid;
cookieverf4 setclientid_confirm;
};
union SETCLIENTID4res switch (nfsstat4 status) {
case NFS4_OK:
SETCLIENTID4resok resok4;
case NFS4ERR_CLID_INUSE:
clientaddr4 client_using;
default:
void;
};
struct SETCLIENTID_CONFIRM4args {
seqid4 seqid;
cookieverf4 setclientid_confirm;
};
struct SETCLIENTID_CONFIRM4res {
nfsstat4 status;
};
/*
* VERIFY: Verify attributes same
*/
struct VERIFY4args {
/* CURRENT_FH: object */
bitmap4 attr_request;
fattr4 obj_attributes;
};
struct VERIFY4res {
nfsstat4 status;
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};
/*
* WRITE: Write to file
*/
enum stable_how4 {
UNSTABLE4 = 0,
DATA_SYNC4 = 1,
FILE_SYNC4 = 2
};
struct WRITE4args {
/* CURRENT_FH: file */
stateid4 stateid;
offset4 offset;
stable_how4 stable;
opaque data<>;
};
struct WRITE4resok {
count4 count;
stable_how4 committed;
writeverf4 verf;
};
union WRITE4res switch (nfsstat4 status) {
case NFS4_OK:
WRITE4resok resok4;
default:
void;
};
/*
* Operation arrays
*/
enum nfs_opnum4 {
OP_ACCESS = 3,
OP_CLOSE = 4,
OP_COMMIT = 5,
OP_CREATE = 6,
OP_DELEGPURGE = 7,
OP_DELEGRETURN = 8,
OP_GETATTR = 9,
OP_GETFH = 10,
OP_LINK = 11,
OP_LOCK = 12,
OP_LOCKT = 13,
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OP_LOCKU = 14,
OP_LOOKUP = 15,
OP_LOOKUPP = 16,
OP_NVERIFY = 17,
OP_OPEN = 18,
OP_OPENATTR = 19,
OP_OPEN_CONFIRM = 20,
OP_PUTFH = 21,
OP_PUTPUBFH = 22,
OP_PUTROOTFH = 23,
OP_READ = 24,
OP_READDIR = 25,
OP_READLINK = 26,
OP_REMOVE = 27,
OP_RENAME = 28,
OP_RENEW = 29,
OP_RESTOREFH = 30,
OP_SAVEFH = 31,
OP_SECINFO = 32,
OP_SETATTR = 33,
OP_SETCLIENTID = 34,
OP_SETCLIENTID_CONFIRM = 35,
OP_VERIFY = 36,
OP_WRITE = 37
};
union nfs_argop4 switch (nfs_opnum4 argop) {
case OP_ACCESS: ACCESS4args opaccess;
case OP_CLOSE: CLOSE4args opclose;
case OP_COMMIT: COMMIT4args opcommit;
case OP_CREATE: CREATE4args opcreate;
case OP_DELEGPURGE: DELEGPURGE4args opdelegpurge;
case OP_DELEGRETURN: DELEGRETURN4args opdelegreturn;
case OP_GETATTR: GETATTR4args opgetattr;
case OP_GETFH: void;
case OP_LINK: LINK4args oplink;
case OP_LOCK: LOCK4args oplock;
case OP_LOCKT: LOCK4args oplockt;
case OP_LOCKU: LOCK4args oplocku;
case OP_LOOKUP: LOOKUP4args oplookup;
case OP_LOOKUPP: void;
case OP_NVERIFY: NVERIFY4args opnverify;
case OP_OPEN: OPEN4args opopen;
case OP_OPENATTR: void;
case OP_OPEN_CONFIRM: OPEN_CONFIRM4args opopen_confirm;
case OP_PUTFH: PUTFH4args opputfh;
case OP_PUTPUBFH: void;
case OP_PUTROOTFH: void;
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case OP_READ: READ4args opread;
case OP_READDIR: READDIR4args opreaddir;
case OP_READLINK: void;
case OP_REMOVE: REMOVE4args opremove;
case OP_RENAME: RENAME4args oprename;
case OP_RENEW: RENEW4args oprenew;
case OP_RESTOREFH: void;
case OP_SAVEFH: void;
case OP_SECINFO: SECINFO4args opsecinfo;
case OP_SETATTR: SETATTR4args opsetattr;
case OP_SETCLIENTID: SETCLIENTID4args opsetclientid;
case OP_SETCLIENTID_CONFIRM: SETCLIENTID_CONFIRM4args
opsetclientid_confirm;
case OP_VERIFY: VERIFY4args opverify;
case OP_WRITE: WRITE4args opwrite;
};
union nfs_resop4 switch (nfs_opnum4 resop){
case OP_ACCESS: ACCESS4res opaccess;
case OP_CLOSE: CLOSE4res opclose;
case OP_COMMIT: COMMIT4res opcommit;
case OP_CREATE: CREATE4res opcreate;
case OP_DELEGPURGE: DELEGPURGE4res opdelegpurge;
case OP_DELEGRETURN: DELEGRETURN4res opdelegreturn;
case OP_GETATTR: GETATTR4res opgetattr;
case OP_GETFH: GETFH4res opgetfh;
case OP_LINK: LINK4res oplink;
case OP_LOCK: LOCK4res oplock;
case OP_LOCKT: LOCKT4res oplockt;
case OP_LOCKU: LOCKU4res oplocku;
case OP_LOOKUP: LOOKUP4res oplookup;
case OP_LOOKUPP: LOOKUPP4res oplookupp;
case OP_NVERIFY: NVERIFY4res opnverify;
case OP_OPEN: OPEN4res opopen;
case OP_OPENATTR: OPENATTR4res opopenattr;
case OP_OPEN_CONFIRM: OPEN_CONFIRM4res opopen_confirm;
case OP_PUTFH: PUTFH4res opputfh;
case OP_PUTPUBFH: PUTPUBFH4res opputpubfh;
case OP_PUTROOTFH: PUTROOTFH4res opputrootfh;
case OP_READ: READ4res opread;
case OP_READDIR: READDIR4res opreaddir;
case OP_READLINK: READLINK4res opreadlink;
case OP_REMOVE: REMOVE4res opremove;
case OP_RENAME: RENAME4res oprename;
case OP_RENEW: RENEW4res oprenew;
case OP_RESTOREFH: RESTOREFH4res oprestorefh;
case OP_SAVEFH: SAVEFH4res opsavefh;
case OP_SECINFO: SECINFO4res opsecinfo;
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case OP_SETATTR: SETATTR4res opsetattr;
case OP_SETCLIENTID: SETCLIENTID4res opsetclientid;
case OP_SETCLIENTID_CONFIRM: SETCLIENTID_CONFIRM4res
opsetclientid_confirm;
case OP_VERIFY: VERIFY4res opverify;
case OP_WRITE: WRITE4res opwrite;
};
struct COMPOUND4args {
utf8string tag;
uint32_t minorversion;
nfs_argop4 argarray<>;
};
struct COMPOUND4res {
nfsstat4 status;
utf8string tag;
nfs_resop4 resarray<>;
};
/*
* Remote file service routines
*/
program NFS4_PROGRAM {
version NFS_V4 {
void
NFSPROC4_NULL(void) = 0;
COMPOUND4res
NFSPROC4_COMPOUND(COMPOUND4args) = 1;
} = 4;
} = 100003;
/*
* NFS4 Callback Procedure Definitions and Program
*/
/*
* CB_GETATTR: Get Current Attributes
*/
struct CB_GETATTR4args {
nfs_fh4 fh;
bitmap4 attr_request;
};
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struct CB_GETATTR4resok {
fattr4 obj_attributes;
};
union CB_GETATTR4res switch (nfsstat4 status) {
case NFS4_OK:
CB_GETATTR4resok resok4;
default:
void;
};
/*
* CB_RECALL: Recall an Open Delegation
*/
struct CB_RECALL4args {
stateid4 stateid;
bool truncate;
nfs_fh4 fh;
};
struct CB_RECALL4res {
nfsstat4 status;
};
/*
* Various definitions for CB_COMPOUND
*/
enum nfs_cb_opnum4 {
OP_CB_GETATTR = 3,
OP_CB_RECALL = 4
};
union nfs_cb_argop4 switch (unsigned argop) {
case OP_CB_GETATTR: CB_GETATTR4args opcbgetattr;
case OP_CB_RECALL: CB_RECALL4args opcbrecall;
};
union nfs_cb_resop4 switch (unsigned resop){
case OP_CB_GETATTR: CB_GETATTR4res opcbgetattr;
case OP_CB_RECALL: CB_RECALL4res opcbrecall;
};
struct CB_COMPOUND4args {
utf8string tag;
uint32_t minorversion;
nfs_cb_argop4 argarray<>;
};
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struct CB_COMPOUND4res {
nfsstat4 status;
utf8string tag;
nfs_cb_resop4 resarray<>;
};
/*
* Program number is in the transient range since the client
* will assign the exact transient program number and provide
* that to the server via the SETCLIENTID operation.
*/
program NFS4_CALLBACK {
version NFS_CB {
void
CB_NULL(void) = 0;
CB_COMPOUND4res
CB_COMPOUND(CB_COMPOUND4args) = 1;
} = 1;
} = 40000000;
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18. Bibliography
[Gray]
C. Gray, D. Cheriton, "Leases: An Efficient Fault-Tolerant Mechanism
for Distributed File Cache Consistency," Proceedings of the Twelfth
Symposium on Operating Systems Principles, p. 202-210, December 1989.
[Juszczak]
Juszczak, Chet, "Improving the Performance and Correctness of an NFS
Server," USENIX Conference Proceedings, USENIX Association, Berkeley,
CA, June 1990, pages 53-63. Describes reply cache implementation
that avoids work in the server by handling duplicate requests. More
important, though listed as a side-effect, the reply cache aids in
the avoidance of destructive non-idempotent operation re-application
-- improving correctness.
[Kazar]
Kazar, Michael Leon, "Synchronization and Caching Issues in the
Andrew File System," USENIX Conference Proceedings, USENIX
Association, Berkeley, CA, Dallas Winter 1988, pages 27-36. A
description of the cache consistency scheme in AFS. Contrasted with
other distributed file systems.
[Macklem]
Macklem, Rick, "Lessons Learned Tuning the 4.3BSD Reno Implementation
of the NFS Protocol," Winter USENIX Conference Proceedings, USENIX
Association, Berkeley, CA, January 1991. Describes performance work
in tuning the 4.3BSD Reno NFS implementation. Describes performance
improvement (reduced CPU loading) through elimination of data copies.
[Mogul]
Mogul, Jeffrey C., "A Recovery Protocol for Spritely NFS," USENIX
File System Workshop Proceedings, Ann Arbor, MI, USENIX Association,
Berkeley, CA, May 1992. Second paper on Spritely NFS proposes a
lease-based scheme for recovering state of consistency protocol.
[Nowicki]
Nowicki, Bill, "Transport Issues in the Network File System," ACM
SIGCOMM newsletter Computer Communication Review, April 1989. A
brief description of the basis for the dynamic retransmission work.
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[Pawlowski]
Pawlowski, Brian, Ron Hixon, Mark Stein, Joseph Tumminaro, "Network
Computing in the UNIX and IBM Mainframe Environment," Uniforum `89
Conf. Proc., (1989) Description of an NFS server implementation for
IBM's MVS operating system.
[RFC1094]
Sun Microsystems, Inc., "NFS: Network File System Protocol
Specification", RFC1094, March 1989.
http://www.ietf.org/rfc/rfc1094.txt
[RFC1345]
Simonsen, K., "Character Mnemonics & Character Sets", RFC1345,
Rationel Almen Planlaegning, June 1992.
http://www.ietf.org/rfc/rfc1345.txt
[RFC1700]
Reynolds, J., Postel, J., "Assigned Numbers", RFC1700, ISI, October
1994
http://www.ietf.org/rfc/rfc1700.txt
[RFC1813]
Callaghan, B., Pawlowski, B., Staubach, P., "NFS Version 3 Protocol
Specification", RFC1813, Sun Microsystems, Inc., June 1995.
http://www.ietf.org/rfc/rfc1813.txt
[RFC1831]
Srinivasan, R., "RPC: Remote Procedure Call Protocol Specification
Version 2", RFC1831, Sun Microsystems, Inc., August 1995.
http://www.ietf.org/rfc/rfc1831.txt
[RFC1832]
Srinivasan, R., "XDR: External Data Representation Standard",
RFC1832, Sun Microsystems, Inc., August 1995.
http://www.ietf.org/rfc/rfc1832.txt
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[RFC1833]
Srinivasan, R., "Binding Protocols for ONC RPC Version 2", RFC1833,
Sun Microsystems, Inc., August 1995.
http://www.ietf.org/rfc/rfc1833.txt
[RFC2025]
Adams, C., "The Simple Public-Key GSS-API Mechanism (SPKM)", RFC2025,
Bell-Northern Research, October 1996.
http://www.ietf.org/rfc/rfc2026.txt
[RFC2054]
Callaghan, B., "WebNFS Client Specification", RFC2054, Sun
Microsystems, Inc., October 1996
http://www.ietf.org/rfc/rfc2054.txt
[RFC2055]
Callaghan, B., "WebNFS Server Specification", RFC2054, Sun
Microsystems, Inc., October 1996
http://www.ietf.org/rfc/rfc2055.txt
[RFC2078]
Linn, J., "Generic Security Service Application Program Interface,
Version 2", RFC2078, OpenVision Technologies, January 1997.
http://www.ietf.org/rfc/rfc2078.txt
[RFC2152]
Goldsmith, D., "UTF-7 A Mail-Safe Transformation Format of Unicode",
RFC2152, Apple Computer, Inc., May 1997
http://www.ietf.org/rfc/rfc2152.txt
[RFC2203]
Eisler, M., Chiu, A., Ling, L., "RPCSEC_GSS Protocol Specification",
RFC2203, Sun Microsystems, Inc., August 1995.
http://www.ietf.org/rfc/rfc2203.txt
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[RFC2279]
Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC2279,
Alis Technologies, January 1998.
http://www.ietf.org/rfc/rfc2279.txt
[RFC2623]
Eisler, M., "NFS Version 2 and Version 3 Security Issues and the NFS
Protocol's Use of RPCSEC_GSS and Kerberos V5", RFC2623, Sun
Microsystems, June 1999
http://www.ietf.org/rfc/rfc2623.txt
[RFC2624]
Shepler, S., "NFS Version 4 Design Considerations", RFC2624, Sun
Microsystems, June 1999
http://www.ietf.org/rfc/rfc2624.txt
[Sandberg]
Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh, B. Lyon, "Design
and Implementation of the Sun Network Filesystem," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA, Summer 1985. The
basic paper describing the SunOS implementation of the NFS version 2
protocol, and discusses the goals, protocol specification and trade-
offs.
[Srinivasan]
Srinivasan, V., Jeffrey C. Mogul, "Spritely NFS: Implementation and
Performance of Cache Consistency Protocols", WRL Research Report
89/5, Digital Equipment Corporation Western Research Laboratory, 100
Hamilton Ave., Palo Alto, CA, 94301, May 1989. This paper analyzes
the effect of applying a Sprite-like consistency protocol applied to
standard NFS. The issues of recovery in a stateful environment are
covered in [Mogul].
[Unicode1]
"Unicode Technical Report #8 - The Unicode Standard, Version 2.1",
Unicode, Inc., The Unicode Consortium, P.O. Box 700519, San Jose, CA
95710-0519 USA, September 1998
http://www.unicode.org/unicode/reports/tr8.html
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[Unicode2]
"Unsupported Scripts" Unicode, Inc., The Unicode Consortium, P.O. Box
700519, San Jose, CA 95710-0519 USA, October 1998
http://www.unicode.org/unicode/standard/unsupported.html
[XNFS]
The Open Group, Protocols for Interworking: XNFS, Version 3W, The
Open Group, 1010 El Camino Real Suite 380, Menlo Park, CA 94025, ISBN
1-85912-184-5, February 1998.
HTML version available: http://www.opengroup.org
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19. Authors and Contributors
General feedback related to this document should be directed to:
nfsv4-wg@sunroof.eng.sun.com
or the editor.
19.1. Editor's Address
Spencer Shepler
Sun Microsystems, Inc.
7808 Moonflower Drive
Austin, Texas 78750
Phone: +1 512-349-9376
E-mail: shepler@eng.sun.com
19.2. Authors' Addresses
Carl Beame
Hummingbird Communications Ltd.
E-mail: beame@bws.com
Brent Callaghan
Sun Microsystems, Inc.
901 San Antonio Road
Palo Alto, CA 94303
Phone: +1 650-786-5067
E-mail: brent.callaghan@eng.sun.com
Mike Eisler
Sun Microsystems, Inc.
5565 Wilson Road
Colorado Springs, CO 80919
Phone: +1 719-599-9026
E-mail: mre@eng.sun.com
Dave Noveck
Network Appliance
495 East Java Drive
Sunnyvale, CA 94089
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Phone: +1 781-861-9291
E-mail: dave.noveck@netapp.com
David Robinson
Sun Microsystems, Inc.
901 San Antonio Road
Palo Alto, CA 94303
Phone: +1 650-786-5088
E-mail: david.robinson@eng.sun.com
Robert Thurlow
Sun Microsystems, Inc.
901 San Antonio Road
Palo Alto, CA 94303
Phone: +1 650-786-5096
E-mail: robert.thurlow@eng.sun.com
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20. Full Copyright Statement
"Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
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