Internet DRAFT - draft-schinazi-masque-connect-udp
draft-schinazi-masque-connect-udp
Network Working Group D. Schinazi
Internet-Draft Google LLC
Intended status: Experimental 16 April 2020
Expires: 18 October 2020
The CONNECT-UDP HTTP Method
draft-schinazi-masque-connect-udp-00
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 of this work is encouraged to happen on the MASQUE IETF
mailing list masque@ietf.org or on the GitHub repository which
contains the draft: https://github.com/DavidSchinazi/masque-drafts.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 18 October 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 2
2. Supported HTTP Versions . . . . . . . . . . . . . . . . . . . 2
3. The CONNECT-UDP Method . . . . . . . . . . . . . . . . . . . 3
4. Encoding of Proxied UDP Packets . . . . . . . . . . . . . . . 4
5. Datagram-Flow-Id Header Definition . . . . . . . . . . . . . 5
6. Server Handling . . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8.1. HTTP Method . . . . . . . . . . . . . . . . . . . . . . . 5
8.2. HTTP Header . . . . . . . . . . . . . . . . . . . . . . . 6
9. Normative References . . . . . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
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].
Discussion of this work is encouraged to happen on the MASQUE IETF
mailing list masque@ietf.org or on the GitHub repository which
contains the draft: https://github.com/DavidSchinazi/masque-drafts.
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.
2. Supported HTTP Versions
The CONNECT-UDP method is defined for all versions of HTTP. When the
HTTP version used runs over QUIC [QUIC], UDP payloads can be sent
over QUIC DATAGRAM frames [DGRAM]. Otherwise they are sent on the
stream where the CONNECT-UDP request was made. Note that when
multiple proxies are involved in a CONNECT-UDP request, all the HTTP
connections along the path need to be using HTTP/3 [H3] or later in
order for UDP payloads to be sent over QUIC DATAGRAM frames.
Additionally, 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.
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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, through one or more proxies, which can then
be secured using QUIC or another protocol running over UDP.
A client sending a CONNECT-UDP request MUST send the authority form
of request-target (Section 5.3 of [RFC7230]); i.e., the request-
target consists of only the host name and port number of the tunnel
destination, separated by a colon. For example,
CONNECT-UDP server.example.com:443 HTTP/1.1
Host: server.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" and ":path" pseudo-header fields MUST be omitted.
* The ":authority" pseudo-header field contains the host and port to
connect to (equivalent to the authority-form of the request-target
of CONNECT-UDP 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 can establish a tunnel either by directly opening
a UDP socket to the request-target or, if configured to use another
proxy, by forwarding the CONNECT-UDP request to the next inbound
proxy. Any 2xx (Successful) response indicates that the sender (and
all inbound proxies) will switch to tunnel mode immediately after the
blank line that concludes the successful response's header section;
data received after that blank line is from the server identified by
the request-target. Any response other than a successful response
indicates that the tunnel has not yet been formed and that the
connection remains governed by HTTP.
A tunnel is closed when a tunnel intermediary detects that either
side has closed its connection: the intermediary MUST attempt to send
any outstanding data that came from the closed side to the other
side, close both connections, and then discard any remaining data
left undelivered.
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A server MUST NOT send any Transfer-Encoding or Content-Length header
fields in a 2xx (Successful) response to CONNECT. 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
When the HTTP connection between client and proxy supports HTTP/3
datagrams [H3DGRAM], UDP packets can be encoded using QUIC DATAGRAM
frames. This support is ascertained by checking receipt of the
H3_DATAGRAM SETTINGS Parameter. Note that when there are multiple
proxies involved, this support needs to be ascertained on all the
HTTP connections that will carry proxied UDP packets.
If the client supports HTTP/3 datagrams and has received the
H3_DATAGRAM SETTINGS Parameter on this connection, it SHOULD attempt
to use HTTP/3 datagrams. This is accomplished by requesting a
datagram flow identifier from the flow identifier allocation service
[H3DGRAM]. That service generates an even flow identifier, and the
client sends it to the server by using the "Datagram-Flow-Id" header
(see Section 5).
If there are multiple proxies involved, proxies along the chain MUST
check whether their upstream connection supports HTTP/3 datagrams.
If it does not, that proxy MUST remove the "Datagram-Flow-Id" header
before forwarding the CONNECT-UDP request.
The proxy that is creating the UDP socket to the destination responds
to the CONNECT-UDP request with a 2xx (Successful) response, and MUST
echo the "Datagram-Flow-Id" header. Once the client has received the
"Datagram-Flow-Id" header on the successful response, it knows that
it can use the HTTP/3 datagram encoding to send proxied UDP packets
for this particular destination. It then encodes the payload of UDP
datagrams into the payload of HTTP/3 datagrams.
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 they arrive before the
CONNECT-UDP request.
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If HTTP/3 datagrams are not supported, the stream is used to convey
UDP payloads, by prefixing them with a 16-bit length.
5. Datagram-Flow-Id Header Definition
"Datagram-Flow-Id" is a Item Structured Header [STRUCT-HDR]. Its
value MUST be an Integer. Its ABNF is:
Datagram-Flow-Id = sh-integer
6. Server Handling
Unlike TCP, UDP is connection-less. The HTTP server 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.
Servers can use connected UDP sockets if their operating system
supports them, as that allows the HTTP server to rely on the kernel
to only send it UDP packets that match the correct 5-tuple. If the
server 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 server.
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.
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. HTTP Header
This document will request IANA to register the "Datagram-Flow-Id"
header in the "Permanent Message Header Field Names" registry
maintained at <https://www.iana.org/assignments/message-headers>.
+-------------------+----------+--------+---------------+
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+--------+---------------+
| Datagram-Flow-Id | http | exp | This document |
+-------------------+----------+--------+---------------+
9. 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-00, 26 February 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-quic-
datagram-00.txt>.
[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/info/rfc7540>.
[H3] Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-27, 21 February 2020, <http://www.ietf.org/
internet-drafts/draft-ietf-quic-http-27.txt>.
[H3DGRAM] Schinazi, D., "Using QUIC Datagrams with HTTP/3", Work in
Progress, Internet-Draft, draft-schinazi-quic-h3-datagram-
03, 12 March 2020, <http://www.ietf.org/internet-drafts/
draft-schinazi-quic-h3-datagram-03.txt>.
[QUIC] Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", Work in Progress, Internet-Draft,
draft-ietf-quic-transport-27, 21 February 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-quic-
transport-27.txt>.
[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/info/rfc2119>.
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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/info/rfc7230>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[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/info/rfc8174>.
[STRUCT-HDR]
Nottingham, M. and P. Kamp, "Structured Field Values for
HTTP", Work in Progress, Internet-Draft, draft-ietf-
httpbis-header-structure-17, 15 March 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-httpbis-
header-structure-17.txt>.
[TCP] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>.
[UDP] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/info/rfc768>.
Acknowledgments
This proposal was inspired directly or indirectly by prior work from
many people. The author would like to thank Eric Rescorla for
suggesting to use an HTTP method to proxy UDP.
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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