The CONNECT-UDP HTTP Method
draft-ietf-masque-connect-udp-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9298.
|
|
|---|---|---|---|
| Author | David Schinazi | ||
| Last updated | 2021-07-12 | ||
| Replaces | draft-schinazi-masque-connect-udp | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
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| Consensus boilerplate | Unknown | ||
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draft-ietf-masque-connect-udp-04
MASQUE D. Schinazi
Internet-Draft Google LLC
Intended status: Standards Track 12 July 2021
Expires: 13 January 2022
The CONNECT-UDP HTTP Method
draft-ietf-masque-connect-udp-04
Abstract
This document describes the CONNECT-UDP HTTP method. CONNECT-UDP is
similar to the HTTP CONNECT method, but it uses UDP instead of TCP.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the MASQUE WG mailing list
(masque@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/masque/.
Source for this draft and an issue tracker can be found at
https://github.com/ietf-wg-masque/draft-ietf-masque-connect-udp.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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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."
This Internet-Draft will expire on 13 January 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 2
2. Supported HTTP Versions . . . . . . . . . . . . . . . . . . . 3
3. The CONNECT-UDP Method . . . . . . . . . . . . . . . . . . . 3
4. Encoding of Proxied UDP Packets . . . . . . . . . . . . . . . 4
5. Proxy Handling . . . . . . . . . . . . . . . . . . . . . . . 5
6. Performance Considerations . . . . . . . . . . . . . . . . . 5
6.1. Tunneling of ECN Marks . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8.1. HTTP Method . . . . . . . . . . . . . . . . . . . . . . . 6
8.2. URI Scheme Registration . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
This document describes the CONNECT-UDP HTTP method. CONNECT-UDP is
similar to the HTTP CONNECT method (see section 4.3.6 of [RFC7231]),
but it uses UDP [UDP] instead of TCP [TCP].
1.1. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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.
If there are HTTP intermediaries (as defined in Section 2.3 of
[RFC7230]) between the client and the proxy, those are referred to as
"intermediaries" in this document.
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2. Supported HTTP Versions
The CONNECT-UDP method is defined for all versions of HTTP. UDP
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
The CONNECT-UDP method requests that the recipient establish a tunnel
over a single HTTP stream to the destination origin server identified
by the request-target and, if successful, thereafter restrict its
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
uses the "masque" scheme and an immutable path of "/". For example:
CONNECT-UDP masque://target.example.com:443/ HTTP/1.1
Host: target.example.com:443
When using HTTP/2 [H2] or later, CONNECT-UDP requests use HTTP
pseudo-headers with the following requirements:
* The ":method" pseudo-header field is set to "CONNECT-UDP".
* The ":scheme" pseudo-header field is set to "masque".
* The ":path" pseudo-header field is set to "/".
* The ":authority" pseudo-header field contains the host and port to
connect to (similar to the authority-form of the request-target of
CONNECT requests; see [RFC7230], Section 5.3).
A CONNECT-UDP request that does not conform to these restrictions is
malformed (see [H2], Section 8.1.2.6).
The recipient proxy establishes a tunnel by directly opening a UDP
socket to the request-target. Any 2xx (Successful) response
indicates that the proxy has opened a socket to the request-target
and is willing to proxy UDP payloads. Any response other than a
successful response indicates that the tunnel has not yet been
formed.
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A proxy MUST NOT send any Transfer-Encoding or Content-Length header
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
semantics; a CONNECT-UDP request with a non-empty payload is
malformed.
Responses to the CONNECT-UDP method are not cacheable.
4. Encoding of Proxied UDP Packets
UDP packets are encoded using HTTP Datagrams [HTTP-DGRAM]. 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 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
HTTP/3 it is necessary to both send and receive the H3_DATAGRAM
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
to the CONNECT-UDP request with a 2xx (Successful) response, and
indicates it supports HTTP Datagrams by sending the corresponding
registration capsule.
Clients MAY optimistically start sending proxied UDP packets before
receiving the response to its CONNECT-UDP request, noting however
that those may not be processed by the proxy if it responds to the
CONNECT-UDP request with a failure, or if the datagrams arrive before
the CONNECT-UDP request.
Extensions to CONNECT-UDP MAY leverage the "Context Extensions" field
of registration capsules in order to negotiate different semantics or
encoding for UDP payloads.
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5. Proxy Handling
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 CONNECT-UDP request without
waiting for a TCP SYN-ACK.
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 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
proxy MUST keep the socket open while the CONNECT-UDP stream is open.
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
Proxies SHOULD strive to avoid increasing burstiness of UDP traffic:
they SHOULD NOT queue packets in order to increase batching.
When the protocol running over UDP that is being proxied uses
congestion control (e.g., [QUIC]), the proxied traffic will incur at
least two nested congestion controllers. This can reduce performance
but the underlying HTTP connection MUST NOT disable congestion
control unless it has an out-of-band way of knowing with absolute
certainty that the inner traffic is congestion-controlled.
If a client or proxy with a connection containing a CONNECT-UDP
stream disables congestion control, it MUST NOT signal ECN support on
that connection. That is, it MUST mark all IP headers with the Not-
ECT codepoint. It MAY continue to report ECN feedback 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
recovery (e.g., [QUIC]), and the underlying HTTP connection runs over
TCP, the proxied traffic will incur at least two nested loss recovery
mechanisms. This can reduce performance as both can sometimes
independently retransmit the same data. To avoid this, HTTP/3
datagrams SHOULD be used.
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6.1. Tunneling of ECN Marks
CONNECT-UDP does not create an IP-in-IP tunnel, so the guidance in
[RFC6040] about transferring ECN marks between inner and outer IP
headers does not apply. There is no inner IP header in CONNECT-UDP
tunnels.
Note that CONNECT-UDP clients do not have the ability in this
specification to control the ECN codepoints on UDP packets the proxy
sends to the server, nor can proxies communicate the markings of each
UDP packet from server to proxy.
A CONNECT-UDP proxy MUST ignore ECN bits in the IP header of UDP
packets received from the server, and MUST set the ECN bits to Not-
ECT on UDP packets it sends to the server. These do not relate to
the ECN markings of packets sent between client and proxy in any way.
7. Security Considerations
There are significant risks in allowing arbitrary clients to
establish a tunnel to arbitrary servers, as that could allow bad
actors to send traffic and have it attributed to the proxy. Proxies
that support CONNECT-UDP SHOULD restrict its use to authenticated
users.
Because the CONNECT method creates a TCP connection to the target,
the target has to indicate its willingness to accept TCP connections
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
proxy could send more data to an unwilling target than a CONNECT
proxy. However, in practice denial of service attacks target open
TCP ports so the TCP SYN-ACK does not offer much protection in real
scenarios. Proxies MUST NOT introspect the contents of UDP payloads
as that would lead to ossification of UDP-based protocols by proxies.
8. IANA Considerations
8.1. HTTP Method
This document will request IANA to register "CONNECT-UDP" in the HTTP
Method Registry (IETF review) maintained at
<https://www.iana.org/assignments/http-methods>.
+-------------+------+------------+---------------+
| Method Name | Safe | Idempotent | Reference |
+-------------+------+------------+---------------+
| CONNECT-UDP | no | no | This document |
+-------------+------+------------+---------------+
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8.2. URI Scheme Registration
This document will request IANA to register the URI scheme "masque".
The syntax definition below uses Augmented Backus-Naur Form (ABNF)
[RFC5234]. The definitions of "host" and "port" are adopted from
[RFC3986]. The syntax of a MASQUE URI is:
masque-URI = "masque:" "//" host ":" port "/"
The "host" and "port" component MUST NOT be empty, and the "port"
component MUST NOT be 0.
9. References
9.1. Normative References
[H2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/rfc/rfc7540>.
[HTTP-DGRAM]
Schinazi, D. and L. Pardue, "Using Datagrams with HTTP",
Work in Progress, Internet-Draft, draft-ietf-masque-h3-
datagram-03, 12 July 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-masque-
h3-datagram-03>.
[QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<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>.
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[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
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[TCP] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/rfc/rfc793>.
[UDP] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/rfc/rfc768>.
9.2. Informative References
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, DOI 10.17487/RFC6040, November
2010, <https://www.rfc-editor.org/rfc/rfc6040>.
Acknowledgments
This document is a product of the MASQUE Working Group, and the
author thanks all MASQUE enthusiasts for their contibutions. This
proposal was inspired directly or indirectly by prior work from many
people. In particular, the author would like to thank Eric Rescorla
for suggesting to use an HTTP method to proxy UDP. Thanks to Lucas
Pardue for their inputs on this document.
Author's Address
David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, California 94043,
United States of America
Email: dschinazi.ietf@gmail.com
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