draft-ietf-masque-connect-udp-04.txt   draft-ietf-masque-connect-udp-05.txt 
MASQUE D. Schinazi MASQUE D. Schinazi
Internet-Draft Google LLC Internet-Draft Google LLC
Intended status: Standards Track 12 July 2021 Intended status: Standards Track 7 October 2021
Expires: 13 January 2022 Expires: 10 April 2022
The CONNECT-UDP HTTP Method UDP Proxying Support for HTTP
draft-ietf-masque-connect-udp-04 draft-ietf-masque-connect-udp-05
Abstract Abstract
This document describes the CONNECT-UDP HTTP method. CONNECT-UDP is This document describes how to proxy UDP over HTTP. Similar to how
similar to the HTTP CONNECT method, but it uses UDP instead of TCP. the CONNECT method allows proxying TCP over HTTP, this document
defines a new mechanism to proxy UDP. It is built using HTTP
Extended CONNECT.
Discussion Venues Discussion Venues
This note is to be removed before publishing as an RFC. This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the MASQUE WG mailing list Discussion of this document takes place on the MASQUE WG mailing list
(masque@ietf.org), which is archived at (masque@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/masque/. https://mailarchive.ietf.org/arch/browse/masque/.
Source for this draft and an issue tracker can be found at Source for this draft and an issue tracker can be found at
skipping to change at page 1, line 42 skipping to change at page 1, line 44
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 13 January 2022. This Internet-Draft will expire on 10 April 2022.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 2 1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
2. Supported HTTP Versions . . . . . . . . . . . . . . . . . . . 3 2. Configuration of Clients . . . . . . . . . . . . . . . . . . 3
3. The CONNECT-UDP Method . . . . . . . . . . . . . . . . . . . 3 3. HTTP Exchanges . . . . . . . . . . . . . . . . . . . . . . . 3
4. Encoding of Proxied UDP Packets . . . . . . . . . . . . . . . 4 3.1. Proxy Handling . . . . . . . . . . . . . . . . . . . . . 4
5. Proxy Handling . . . . . . . . . . . . . . . . . . . . . . . 5 3.2. HTTP Request over HTTP/1.1 . . . . . . . . . . . . . . . 5
6. Performance Considerations . . . . . . . . . . . . . . . . . 5 3.3. HTTP Response over HTTP/1.1 . . . . . . . . . . . . . . . 5
6.1. Tunneling of ECN Marks . . . . . . . . . . . . . . . . . 6 3.4. HTTP Request over HTTP/2 and HTTP/3 . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 3.5. HTTP Response over HTTP/2 and HTTP/3 . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 3.6. Note About Draft Versions . . . . . . . . . . . . . . . . 7
8.1. HTTP Method . . . . . . . . . . . . . . . . . . . . . . . 6 4. Encoding of Proxied UDP Packets . . . . . . . . . . . . . . . 7
8.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 7 5. Performance Considerations . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. MTU Considerations . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 7 5.2. Tunneling of ECN Marks . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. HTTP Upgrade Token . . . . . . . . . . . . . . . . . . . 10
7.2. Datagram Format Type . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 12
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
This document describes the CONNECT-UDP HTTP method. CONNECT-UDP is This document describes how to proxy UDP over HTTP. Similar to how
similar to the HTTP CONNECT method (see section 4.3.6 of [RFC7231]), the CONNECT method (see Section 9.3.6 of [SEMANTICS]) allows proxying
but it uses UDP [UDP] instead of TCP [TCP]. TCP [TCP] over HTTP, this document defines a new mechanism to proxy
UDP [UDP].
UDP Proxying supports all versions of HTTP and uses HTTP Datagrams
[HTTP-DGRAM]. When using HTTP/2 or HTTP/3, UDP proxying uses HTTP
Extended CONNECT as described in [EXT-CONNECT2] and [EXT-CONNECT3].
When using HTTP/1.x, UDP proxying uses HTTP Upgrade as defined in
Section 7.8 of [SEMANTICS].
1.1. Conventions and Definitions 1.1. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
In this document, we use the term "proxy" to refer to the HTTP server In this document, we use the term "proxy" to refer to the HTTP server
that opens the UDP socket and responds to the CONNECT-UDP request. that opens the UDP socket and responds to the UDP proxying request.
If there are HTTP intermediaries (as defined in Section 2.3 of If there are HTTP intermediaries (as defined in Section 3.7 of
[RFC7230]) between the client and the proxy, those are referred to as [SEMANTICS]) between the client and the proxy, those are referred to
"intermediaries" in this document. as "intermediaries" in this document.
2. Supported HTTP Versions Note that, when the HTTP version in use does not support multiplexing
streams (such as HTTP/1.1), any reference to "stream" in this
document represents the entire connection.
The CONNECT-UDP method is defined for all versions of HTTP. UDP 2. Configuration of Clients
payloads are sent using HTTP Datagrams [HTTP-DGRAM]. Note that, when
the HTTP version in use does not support multiplexing streams (such
as HTTP/1.1), then any reference to "stream" in this document is
meant to represent the entire connection.
3. The CONNECT-UDP Method Clients are configured to use UDP Proxying over HTTP via an URI
Template [TEMPLATE]. The URI template MUST contain exactly two
variables: "target_host" and "target_port". Examples are shown
below:
The CONNECT-UDP method requests that the recipient establish a tunnel https://masque.example.org/{target_host}/{target_port}/
over a single HTTP stream to the destination origin server identified https://proxy.example.org:4443/masque?h={target_host}&p={target_port}
by the request-target and, if successful, thereafter restrict its https://proxy.example.org:4443/masque{?target_host,target_port}
behavior to blind forwarding of packets, in both directions, until
the tunnel is closed. Tunnels are commonly used to create an end-to-
end virtual connection, which can then be secured using QUIC [QUIC]
or another protocol running over UDP.
The request-target of a CONNECT-UDP request is a URI [RFC3986] which Figure 1: URI Template Examples
uses the "masque" scheme and an immutable path of "/". For example:
CONNECT-UDP masque://target.example.com:443/ HTTP/1.1 Since the original HTTP CONNECT method allowed conveying the target
Host: target.example.com:443 host and port but not the scheme, proxy authority, path, nor query,
there exist proxy configuration interfaces that only allow the user
to configure the proxy host and the proxy port. Client
implementations of this specification that are constrained by such
limitations MUST use the default template which is defined as:
"https://$PROXY_HOST:$PROXY_PORT/{target_host}/{target_port}/" where
$PROXY_HOST and $PROXY_PORT are the configured host and port of the
proxy respectively. Proxy deployments SHOULD use the default
template to facilitate interoperability with such clients.
When using HTTP/2 [H2] or later, CONNECT-UDP requests use HTTP 3. HTTP Exchanges
pseudo-headers with the following requirements:
* The ":method" pseudo-header field is set to "CONNECT-UDP". This document defines the "connect-udp" HTTP Upgrade Token. "connect-
udp" uses the Capsule Protocol as defined in [HTTP-DGRAM].
* The ":scheme" pseudo-header field is set to "masque". A "connect-udp" request requests that the recipient establish a
tunnel over a single HTTP stream to the destination target server
identified by the "target_host" and "target_port" variables of the
URI template (see Section 2). If the request is successful, the
proxy commits to converting received HTTP Datagrams into UDP packets
and vice versa until the tunnel is closed. Tunnels are commonly used
to create an end-to-end virtual connection, which can then be secured
using QUIC [QUIC] or another protocol running over UDP.
* The ":path" pseudo-header field is set to "/". When sending its UDP proxying request, the client SHALL perform URI
template expansion to determine the path and query of its request.
target_host supports using DNS names, IPv6 literals and IPv4
literals. Note that this URI template expansion requires using pct-
encoding, so for example if the target_host is "2001:db8::42", it
will be encoded in the URI as "2001%3Adb8%3A%3A42".
* The ":authority" pseudo-header field contains the host and port to A payload within a UDP proxying request message has no defined
connect to (similar to the authority-form of the request-target of semantics; a UDP proxying request with a non-empty payload is
CONNECT requests; see [RFC7230], Section 5.3). malformed.
A CONNECT-UDP request that does not conform to these restrictions is Responses to UDP proxying requests are not cacheable.
malformed (see [H2], Section 8.1.2.6).
The recipient proxy establishes a tunnel by directly opening a UDP 3.1. Proxy Handling
socket to the request-target. Any 2xx (Successful) response
indicates that the proxy has opened a socket to the request-target Upon receiving a UDP proxying request, the recipient proxy extracts
the "target_host" and "target_port" variables from the URI it has
reconstructed from the request headers, and establishes a tunnel by
directly opening a UDP socket to the requested target.
Unlike TCP, UDP is connection-less. The proxy that opens the UDP
socket has no way of knowing whether the destination is reachable.
Therefore it needs to respond to the request without waiting for a
packet from the target. However, if the target_host is a DNS name,
the proxy MUST perform DNS resolution before replying to the HTTP
request. If DNS resolution fails, the proxy MUST fail the request
and SHOULD send details using the Proxy-Status header [PROXY-STATUS].
Proxies can use connected UDP sockets if their operating system
supports them, as that allows the proxy to rely on the kernel to only
send it UDP packets that match the correct 5-tuple. If the proxy
uses a non-connected socket, it MUST validate the IP source address
and UDP source port on received packets to ensure they match the
client's request. Packets that do not match MUST be discarded by the
proxy.
The lifetime of the socket is tied to the request stream. The proxy
MUST keep the socket open while the request stream is open. If a
proxy is notified by its operating system that its socket is no
longer usable, it MUST close the request stream. Proxies MAY choose
to close sockets due to a period of inactivity, but they MUST close
the request stream before closing the socket. Proxies that close
sockets after a period of inactivity SHOULD NOT use a period lower
than two minutes, see Section 4.3 of [BEHAVE].
A successful response (as defined in Section 3.3 and Section 3.5)
indicates that the proxy has opened a socket to the requested target
and is willing to proxy UDP payloads. Any response other than a and is willing to proxy UDP payloads. Any response other than a
successful response indicates that the tunnel has not yet been successful response indicates that the request has failed, and the
formed. client MUST therefore abort the request.
A proxy MUST NOT send any Transfer-Encoding or Content-Length header 3.2. HTTP Request over HTTP/1.1
fields in a 2xx (Successful) response to CONNECT-UDP. A client MUST
treat a response to CONNECT-UDP containing any Content-Length or
Transfer-Encoding header fields as malformed.
A payload within a CONNECT-UDP request message has no defined When using HTTP/1.1, a UDP proxying request will meet the following
semantics; a CONNECT-UDP request with a non-empty payload is requirements:
malformed.
Responses to the CONNECT-UDP method are not cacheable. * the method SHALL be "CONNECT".
4. Encoding of Proxied UDP Packets * the request-target SHALL use absolute-form (see Section 3.2.2 of
[MESSAGING]).
UDP packets are encoded using HTTP Datagrams [HTTP-DGRAM]. The * the request SHALL include a single Host header containing the
payload of a UDP packet (referred to as "data octets" in [UDP]) is origin of the proxy.
sent unmodified in the "HTTP Datagram Payload" field of an HTTP
Datagram. In order to use HTTP Datagrams, the CONNECT-UDP client
will first decide whether or not to use HTTP Datagram Contexts and
then register its context ID (or lack thereof) using the
corresponding registration capsule, see [HTTP-DGRAM].
Since HTTP Datagrams require prior negotiation (for example, in * the request SHALL include a single "Connection" header with value
HTTP/3 it is necessary to both send and receive the H3_DATAGRAM "Upgrade".
SETTINGS Parameter), clients MUST NOT send any HTTP Datagrams until
they have established support on a given connection. If negotiation
of HTTP Datagrams fails (for example if an HTTP/3 SETTINGS frame was
received without the H3_DATAGRAM SETTINGS Parameter), the client MUST
consider its CONNECT-UDP request as failed.
The proxy that is creating the UDP socket to the destination responds * the request SHALL include a single "Upgrade" header with value
to the CONNECT-UDP request with a 2xx (Successful) response, and "connect-udp".
indicates it supports HTTP Datagrams by sending the corresponding
registration capsule.
Clients MAY optimistically start sending proxied UDP packets before For example, if the client is configured with URI template
receiving the response to its CONNECT-UDP request, noting however "https://proxy.example.org/{target_host}/{target_port}/" and wishes
that those may not be processed by the proxy if it responds to the to open a UDP proxying tunnel to target 192.0.2.42:443, it could send
CONNECT-UDP request with a failure, or if the datagrams arrive before the following request:
the CONNECT-UDP request.
Extensions to CONNECT-UDP MAY leverage the "Context Extensions" field CONNECT https://proxy.example.org/192.0.2.42/443/ HTTP/1.1
of registration capsules in order to negotiate different semantics or Host: proxy.example.org
encoding for UDP payloads. Connection: upgrade
Upgrade: connect-udp
5. Proxy Handling Figure 2: Example HTTP Request over HTTP/1.1
Unlike TCP, UDP is connection-less. The proxy that opens the UDP 3.3. HTTP Response over HTTP/1.1
socket has no way of knowing whether the destination is reachable.
Therefore it needs to respond to the CONNECT-UDP request without
waiting for a TCP SYN-ACK.
Proxies can use connected UDP sockets if their operating system The proxy SHALL indicate a successful response by replying with the
supports them, as that allows the proxy to rely on the kernel to only following requirements:
send it UDP packets that match the correct 5-tuple. If the proxy
uses a non-connected socket, it MUST validate the IP source address
and UDP source port on received packets to ensure they match the
client's CONNECT-UDP request. Packets that do not match MUST be
discarded by the proxy.
The lifetime of the socket is tied to the CONNECT-UDP stream. The * the HTTP status code on the response SHALL be 101 (Switching
proxy MUST keep the socket open while the CONNECT-UDP stream is open. Protocols).
Proxies MAY choose to close sockets due to a period of inactivity,
but they MUST close the CONNECT-UDP stream before closing the socket.
6. Performance Considerations * the reponse SHALL include a single "Connection" header with value
"Upgrade".
* the response SHALL include a single "Upgrade" header with value
"connect-udp".
* the response SHALL NOT include any Transfer-Encoding or Content-
Length header fields.
If any of these requirements are not met, the client MUST treat this
proxying attempt as failed and abort the connection.
For example, the proxy could respond with:
HTTP/1.1 101 Switching Protocols
Connection: upgrade
Upgrade: connect-udp
Figure 3: Example HTTP Response over HTTP/1.1
3.4. HTTP Request over HTTP/2 and HTTP/3
When using HTTP/2 [H2] or HTTP/3 [H3], UDP proxying requests use HTTP
pseudo-headers with the following requirements:
* The ":method" pseudo-header field SHALL be "CONNECT".
* The ":protocol" pseudo-header field SHALL be "connect-udp".
* The ":authority" pseudo-header field SHALL contain the authority
of the proxy.
* The ":path" and ":scheme" pseudo-header fields SHALL NOT be empty.
Their values SHALL contain the scheme and path from the URI
template after the URI template expansion process has been
completed.
A UDP proxying request that does not conform to these restrictions is
malformed (see Section 8.1.2.6 of [H2]).
For example, if the client is configured with URI template
"https://proxy.example.org/{target_host}/{target_port}/" and wishes
to open a UDP proxying tunnel to target 192.0.2.42:443, it could send
the following request:
HEADERS
:method = CONNECT
:protocol = connect-udp
:scheme = https
:path = /192.0.2.42/443/
:authority = proxy.example.org
Figure 4: Example HTTP Request over HTTP/2
3.5. HTTP Response over HTTP/2 and HTTP/3
The proxy SHALL indicate a successful response by replying with any
2xx (Successful) HTTP status code, without any Transfer-Encoding or
Content-Length header fields.
If any of these requirements are not met, the client MUST treat this
proxying attempt as failed and abort the request.
For example, the proxy could respond with:
HEADERS
:status = 200
Figure 5: Example HTTP Response over HTTP/2
3.6. Note About Draft Versions
[[RFC editor: please remove this section before publication.]]
In order to allow implementations to support multiple draft versions
of this specification during its development, we introduce the
"connect-udp-version" header. When sent by the client, it contains a
list of draft numbers supported by the client (e.g., "connect-udp-
version: 0, 2"). When sent by the proxy, it contains a single draft
number selected by the proxy from the list provided by the client
(e.g., "connect-udp-version: 2"). Sending this header is RECOMMENDED
but not required.
4. Encoding of Proxied UDP Packets
UDP packets are encoded using HTTP Datagrams [HTTP-DGRAM] with the
UDP_PAYLOAD HTTP Datagram Format Type (see value in Section 7.2).
When using the UDP_PAYLOAD HTTP Datagram Format Type, the payload of
a UDP packet (referred to as "data octets" in [UDP]) is sent
unmodified in the "HTTP Datagram Payload" field of an HTTP Datagram.
In order to use HTTP Datagrams, the client will first decide whether
or not to use HTTP Datagram Contexts and then register its context ID
(or lack thereof) using the corresponding registration capsule, see
[HTTP-DGRAM].
When sending a REGISTER_DATAGRAM_CONTEXT or
REGISTER_DATAGRAM_NO_CONTEXT capsule using the "Datagram Format Type"
set to UDP_PAYLOAD, the "Datagram Format Additional Data" field SHALL
be empty. Servers MUST NOT register contexts using the UDP_PAYLOAD
HTTP Datagram Format Type. Clients MUST NOT register more than one
context using the UDP_PAYLOAD HTTP Datagram Format Type. Endpoints
MUST NOT close contexts using the UDP_PAYLOAD HTTP Datagram Format
Type. If an endpoint detects a violation of any of these
requirements, it MUST abort the stream.
Clients MAY optimistically start sending proxied UDP packets before
receiving the response to its UDP proxying request, noting however
that those may not be processed by the proxy if it responds to the
request with a failure, or if the datagrams are received by the proxy
before the request.
Extensions to this mechanism MAY define new HTTP Datagram Format
Types in order to use different semantics or encodings for UDP
payloads.
5. Performance Considerations
Proxies SHOULD strive to avoid increasing burstiness of UDP traffic: Proxies SHOULD strive to avoid increasing burstiness of UDP traffic:
they SHOULD NOT queue packets in order to increase batching. they SHOULD NOT queue packets in order to increase batching.
When the protocol running over UDP that is being proxied uses When the protocol running over UDP that is being proxied uses
congestion control (e.g., [QUIC]), the proxied traffic will incur at congestion control (e.g., [QUIC]), the proxied traffic will incur at
least two nested congestion controllers. This can reduce performance least two nested congestion controllers. This can reduce performance
but the underlying HTTP connection MUST NOT disable congestion but the underlying HTTP connection MUST NOT disable congestion
control unless it has an out-of-band way of knowing with absolute control unless it has an out-of-band way of knowing with absolute
certainty that the inner traffic is congestion-controlled. certainty that the inner traffic is congestion-controlled.
If a client or proxy with a connection containing a CONNECT-UDP If a client or proxy with a connection containing a UDP proxying
stream disables congestion control, it MUST NOT signal ECN support on request stream disables congestion control, it MUST NOT signal ECN
that connection. That is, it MUST mark all IP headers with the Not- support on that connection. That is, it MUST mark all IP headers
ECT codepoint. It MAY continue to report ECN feedback via ACK_ECN with the Not-ECT codepoint. It MAY continue to report ECN feedback
frames, as the peer may not have disabled congestion control. via ACK_ECN frames, as the peer may not have disabled congestion
control.
When the protocol running over UDP that is being proxied uses loss When the protocol running over UDP that is being proxied uses loss
recovery (e.g., [QUIC]), and the underlying HTTP connection runs over recovery (e.g., [QUIC]), and the underlying HTTP connection runs over
TCP, the proxied traffic will incur at least two nested loss recovery TCP, the proxied traffic will incur at least two nested loss recovery
mechanisms. This can reduce performance as both can sometimes mechanisms. This can reduce performance as both can sometimes
independently retransmit the same data. To avoid this, HTTP/3 independently retransmit the same data. To avoid this, HTTP/3
datagrams SHOULD be used. datagrams SHOULD be used.
6.1. Tunneling of ECN Marks 5.1. MTU Considerations
CONNECT-UDP does not create an IP-in-IP tunnel, so the guidance in When using HTTP/3 with the QUIC Datagram extension [DGRAM], UDP
payloads are transmitted in QUIC DATAGRAM frames. Since those cannot
be fragmented, they can only carry payloads up to a given length
determined by the QUIC connection configuration and the path MTU. If
a proxy is using QUIC DATAGRAM frames and it receives a UDP payload
from the target that will not fit inside a QUIC DATAGRAM frame, the
proxy SHOULD NOT send the UDP payload in a DATAGRAM capsule, as that
defeats the end-to-end unreliability characteristic that methods such
as Datagram Packetization Layer Path MTU Discovery (DPLPMTUD) depend
on [RFC8899]. In this scenario, the proxy SHOULD drop the UDP
payload and send an ICMP "Packet Too Big" message to the target
[RFC4443].
5.2. Tunneling of ECN Marks
UDP proxying does not create an IP-in-IP tunnel, so the guidance in
[RFC6040] about transferring ECN marks between inner and outer IP [RFC6040] about transferring ECN marks between inner and outer IP
headers does not apply. There is no inner IP header in CONNECT-UDP headers does not apply. There is no inner IP header in UDP proxying
tunnels. tunnels.
Note that CONNECT-UDP clients do not have the ability in this Note that UDP proxying clients do not have the ability in this
specification to control the ECN codepoints on UDP packets the proxy specification to control the ECN codepoints on UDP packets the proxy
sends to the server, nor can proxies communicate the markings of each sends to the server, nor can proxies communicate the markings of each
UDP packet from server to proxy. UDP packet from server to proxy.
A CONNECT-UDP proxy MUST ignore ECN bits in the IP header of UDP A UDP proxy MUST ignore ECN bits in the IP header of UDP packets
packets received from the server, and MUST set the ECN bits to Not- received from the server, and MUST set the ECN bits to Not-ECT on UDP
ECT on UDP packets it sends to the server. These do not relate to packets it sends to the server. These do not relate to the ECN
the ECN markings of packets sent between client and proxy in any way. markings of packets sent between client and proxy in any way.
7. Security Considerations 6. Security Considerations
There are significant risks in allowing arbitrary clients to There are significant risks in allowing arbitrary clients to
establish a tunnel to arbitrary servers, as that could allow bad establish a tunnel to arbitrary servers, as that could allow bad
actors to send traffic and have it attributed to the proxy. Proxies actors to send traffic and have it attributed to the proxy. Proxies
that support CONNECT-UDP SHOULD restrict its use to authenticated that support UDP proxying SHOULD restrict its use to authenticated
users. users.
Because the CONNECT method creates a TCP connection to the target, Because the CONNECT method creates a TCP connection to the target,
the target has to indicate its willingness to accept TCP connections the target has to indicate its willingness to accept TCP connections
by responding with a TCP SYN-ACK before the proxy can send it by responding with a TCP SYN-ACK before the proxy can send it
application data. UDP doesn't have this property, so a CONNECT-UDP application data. UDP doesn't have this property, so a UDP proxy
proxy could send more data to an unwilling target than a CONNECT could send more data to an unwilling target than a CONNECT proxy.
proxy. However, in practice denial of service attacks target open However, in practice denial of service attacks target open TCP ports
TCP ports so the TCP SYN-ACK does not offer much protection in real so the TCP SYN-ACK does not offer much protection in real scenarios.
scenarios. Proxies MUST NOT introspect the contents of UDP payloads Proxies MUST NOT introspect the contents of UDP payloads as that
as that would lead to ossification of UDP-based protocols by proxies. would lead to ossification of UDP-based protocols by proxies.
8. IANA Considerations 7. IANA Considerations
8.1. HTTP Method 7.1. HTTP Upgrade Token
This document will request IANA to register "CONNECT-UDP" in the HTTP This document will request IANA to register "connect-udp" in the HTTP
Method Registry (IETF review) maintained at Upgrade Token Registry maintained at
<https://www.iana.org/assignments/http-methods>. <https://www.iana.org/assignments/http-upgrade-tokens>.
+-------------+------+------------+---------------+ Value: connect-udp
| Method Name | Safe | Idempotent | Reference |
+-------------+------+------------+---------------+
| CONNECT-UDP | no | no | This document |
+-------------+------+------------+---------------+
8.2. URI Scheme Registration Description: Proxying of UDP Payloads.
This document will request IANA to register the URI scheme "masque". Expected Version Tokens: None.
The syntax definition below uses Augmented Backus-Naur Form (ABNF) Reference: This document.
[RFC5234]. The definitions of "host" and "port" are adopted from
[RFC3986]. The syntax of a MASQUE URI is:
masque-URI = "masque:" "//" host ":" port "/" 7.2. Datagram Format Type
The "host" and "port" component MUST NOT be empty, and the "port" This document will request IANA to register UDP_PAYLOAD in the "HTTP
component MUST NOT be 0. Datagram Format Types" registry established by [HTTP-DGRAM].
9. References +=============+==========+===============+
| Type | Value | Specification |
+=============+==========+===============+
| UDP_PAYLOAD | 0xff6f00 | This Document |
+-------------+----------+---------------+
9.1. Normative References Table 1: Registered Datagram Format Type
8. References
8.1. Normative References
[DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", Work in Progress, Internet-
Draft, draft-ietf-quic-datagram-06, 5 October 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic-
datagram-06>.
[EXT-CONNECT2]
McManus, P., "Bootstrapping WebSockets with HTTP/2",
RFC 8441, DOI 10.17487/RFC8441, September 2018,
<https://www.rfc-editor.org/rfc/rfc8441>.
[EXT-CONNECT3]
Hamilton, R., "Bootstrapping WebSockets with HTTP/3", Work
in Progress, Internet-Draft, draft-ietf-httpbis-h3-
websockets-00, 9 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
h3-websockets-00>.
[H2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [H2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540, Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015, DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/rfc/rfc7540>. <https://www.rfc-editor.org/rfc/rfc7540>.
[H3] Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-34, 2 February 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-quic-
http-34>.
[HTTP-DGRAM] [HTTP-DGRAM]
Schinazi, D. and L. Pardue, "Using Datagrams with HTTP", Schinazi, D. and L. Pardue, "Using Datagrams with HTTP",
Work in Progress, Internet-Draft, draft-ietf-masque-h3- Work in Progress, Internet-Draft, draft-ietf-masque-h3-
datagram-03, 12 July 2021, datagram-04, 6 October 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-masque- <https://datatracker.ietf.org/doc/html/draft-ietf-masque-
h3-datagram-03>. h3-datagram-04>.
[MESSAGING]
Fielding, R. T., Nottingham, M., and J. Reschke,
"HTTP/1.1", Work in Progress, Internet-Draft, draft-ietf-
httpbis-messaging-19, 12 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
messaging-19>.
[QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based [QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000, Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021, DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>. <https://www.rfc-editor.org/rfc/rfc9000>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>. <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/rfc/rfc3986>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/rfc/rfc5234>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/rfc/rfc7230>.
[RFC7231] "*** BROKEN REFERENCE ***".
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[SEMANTICS]
Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
Semantics", Work in Progress, Internet-Draft, draft-ietf-
httpbis-semantics-19, 12 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
semantics-19>.
[TCP] Postel, J., "Transmission Control Protocol", STD 7, [TCP] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/rfc/rfc793>. <https://www.rfc-editor.org/rfc/rfc793>.
[TEMPLATE] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570,
DOI 10.17487/RFC6570, March 2012,
<https://www.rfc-editor.org/rfc/rfc6570>.
[UDP] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [UDP] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980, DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/rfc/rfc768>. <https://www.rfc-editor.org/rfc/rfc768>.
9.2. Informative References 8.2. Informative References
[BEHAVE] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/rfc/rfc4787>.
[PROXY-STATUS]
Nottingham, M. and P. Sikora, "The Proxy-Status HTTP
Response Header Field", Work in Progress, Internet-Draft,
draft-ietf-httpbis-proxy-status-06, 16 August 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
proxy-status-06>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/rfc/rfc4443>.
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion [RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, DOI 10.17487/RFC6040, November Notification", RFC 6040, DOI 10.17487/RFC6040, November
2010, <https://www.rfc-editor.org/rfc/rfc6040>. 2010, <https://www.rfc-editor.org/rfc/rfc6040>.
[RFC8899] Fairhurst, G., Jones, T., Tüxen, M., Rüngeler, I., and T.
Völker, "Packetization Layer Path MTU Discovery for
Datagram Transports", RFC 8899, DOI 10.17487/RFC8899,
September 2020, <https://www.rfc-editor.org/rfc/rfc8899>.
Acknowledgments Acknowledgments
This document is a product of the MASQUE Working Group, and the This document is a product of the MASQUE Working Group, and the
author thanks all MASQUE enthusiasts for their contibutions. This author thanks all MASQUE enthusiasts for their contibutions. This
proposal was inspired directly or indirectly by prior work from many proposal was inspired directly or indirectly by prior work from many
people. In particular, the author would like to thank Eric Rescorla people. In particular, the author would like to thank Eric Rescorla
for suggesting to use an HTTP method to proxy UDP. Thanks to Lucas for suggesting to use an HTTP method to proxy UDP. Thanks to Lucas
Pardue for their inputs on this document. Pardue for their inputs on this document.
Author's Address Author's Address
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