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 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	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
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2021 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	and restrictions with respect to this document. Code Components		and restrictions with respect to this document. Code Components
	extracted from this document must include Simplified BSD License text		extracted from this document must include Simplified BSD License text
	as described in Section 4.e of the Trust Legal Provisions and are		as described in Section 4.e of the Trust Legal Provisions and are
	provided without warranty as described in the Simplified BSD License.		provided without warranty as described in the Simplified BSD License.
	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
End of changes. 63 change blocks.
	176 lines changed or deleted		395 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/