Internet DRAFT - draft-mcmanus-httpbis-h2-websockets
draft-mcmanus-httpbis-h2-websockets
Network Working Group P. McManus
Internet-Draft Mozilla
Intended status: Standards Track November 11, 2017
Expires: May 15, 2018
Bootstrapping WebSockets with HTTP/2
draft-mcmanus-httpbis-h2-websockets-02
Abstract
This document defines a mechanism for running the WebSocket Protocol
[RFC6455] over a single stream of an HTTP/2 connection.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 15, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The ENABLE_CONNECT_PROTOCOL SETTINGS Parameter . . . . . . . 3
4. The Extended CONNECT Method . . . . . . . . . . . . . . . . . 3
5. Using Extended CONNECT To Bootstrap The WebSocket Protocol . 4
5.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Design Considerations . . . . . . . . . . . . . . . . . . . . 5
7. About Intermediaries . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
11. Normative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The Hypertext Transfer Protocol (HTTP) provides compatible resource
level semantics across different versions but it does not offer
compatibility at the connection management level. Other protocols,
such as WebSockets, that rely on connection management details of
HTTP must be updated for new versions of HTTP.
The WebSocket Protocol [RFC6455] uses the HTTP/1.1 [RFC7230] Upgrade
mechanism to transition a TCP connection from HTTP into a WebSocket
connection. A different approach must be taken with HTTP/2
[RFC7540]. The multiplexing nature of HTTP/2 does not allow
connection wide header and status codes such as the Upgrade and
Connection request headers or the 101 response code due to its
multiplexing nature. These are all required by the [RFC6455] opening
handshake.
Being able to bootstrap WebSockets from HTTP/2 allows one TCP
connection to be shared by both protocols and extends HTTP/2's more
efficient use of the network to WebSockets.
This document extends the HTTP/2 CONNECT method. The extension
allows the substitution of a new protocol name to connect to rather
than the external host normally used by CONNECT. The result is a
tunnel on a single HTTP/2 stream that can carry data for WebSockets
(or any other protocol). The other streams on the connection may
carry more extended CONNECT tunnels, traditional HTTP/2 data, or a
mixture of both.
This tunneled stream will be multiplexed with other regular streams
on the connection and enjoys the normal priority, cancellation, and
flow control features of HTTP/2.
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Streams that successfully establish a WebSocket connection using a
tunneled stream and the modifications to the opening handshake
defined in this document then use the traditional WebSocket Protocol
treating the stream as if were the TCP connection in that
specification.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in BCP 14,
[RFC2119].
3. The ENABLE_CONNECT_PROTOCOL SETTINGS Parameter
This document adds a new SETTINGS Parameter to those defined by
[RFC7540] Section 6.5.2.
The new parameter is ENABLE_CONNECT_PROTOCOL (type = 0x8). The value
of the parameter MUST be 0 or 1.
Upon receipt of ENABLE_CONNECT_PROTOCOL with a value of 1 a client
MAY use the Extended CONNECT definition of this document when
creating new streams. Receipt of this parameter by a server does not
have any impact.
A sender MUST NOT send a ENABLE_CONNECT_PROTOCOL parameter with the
value of 0 after previously sending a value of 1.
The use of a SETTINGS Parameter to opt-in to an otherwise
incompatible protocol change is a use of "Extending HTTP/2" defined
by section 5.5 of [RFC7540]. If a client were to use the provisions
of the extended CONNECT method defined in this document without first
receiving a ENABLE_CONNECT_PROTOCOL parameter with the value of 1 it
would be a protocol violation.
4. The Extended CONNECT Method
The CONNECT Method of [RFC7540] Section 8.3 is modified in the
following ways:
o A new pseudo-header :protocol MAY be included on request HEADERS
indicating the desired protocol to be spoken on the tunnel created
by CONNECT. The pseudo-header is single valued and contains a
value from the HTTP Upgrade Token Registry defined by [RFC7230].
o On requests bearing the :protocol pseudo-header, the :scheme and
:path pseudo-header fields SHOULD be included.
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o On requests bearing the :protocol pseudo-header, the :authority
pseudo-header field is interpreted according to [RFC7540]
Section 8.1.2.3 instead of [RFC7540] Section 8.3. In particular
the server MUST not make a new TCP connection to the host and port
indicated by the :authority.
Upon receiving a CONNECT request bearing the :protocol pseudo-header
the server establishes a tunnel to another service of the protocol
type indicated by the pseudo-header. This service may or may not be
co-located with the server.
5. Using Extended CONNECT To Bootstrap The WebSocket Protocol
The pseudo-header :protocol MUST be included in the CONNECT request
and it MUST have a value of websocket to initiate a WebSocket
connection on an HTTP/2 stream. Other HTTP request and response
headers, such as those for manipulating cookies, may be included in
the HEADERS with the CONNECT :method as usual. This request replaces
the GET based request in [RFC6455] and is used to process the
WebSockets opening handshake.
The scheme of the Target URI [RFC7230] MUST be https for wss schemed
WebSockets and http for ws schemed WebSockets. The websocket URI is
still used for proxy autoconfiguration.
[RFC6455] requires the use of Connection and Upgrade headers that are
not part of HTTP/2. They MUST not be included in the CONNECT request
defined here.
[RFC6455] requires the use of a Host header which is also not part of
HTTP/2. The Host information is conveyed as part of the :authority
pseudo-header which is required on every HTTP/2 transaction.
Implementations using this extended CONNECT to bootstrap WebSockets
do not do the processing of the [RFC6455] Sec-WebSocket-Key and Sec-
WebSocket-Accept headers as that functionality has been superceded by
the :protocol pseudo-header.
The Sec-WebSocket-Version, Origin [RFC6454], Sec-WebSocket-Protocol,
and Sec-WebSocket-Extensions headers are used on the CONNECT request
and response headers in the same way as defined in [RFC6455]. Note
that HTTP/1 header names were case insensitive and HTTP/2 requires
they be encoded as lower case.
After successfully processing the opening handshake the peers should
proceed with The WebSocket Protocol [RFC6455] using the HTTP/2 stream
from the CONNECT transaction as if it were the TCP connection
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referred to in [RFC6455]. The state of the WebSocket connection at
this point is OPEN as defined by [RFC6455] Section 4.1.
5.1. Example
[[ From Client ]] [[ From Server ]]
SETTINGS
ENABLE_CONNECT_PROTOCOL = 1
HEADERS + END_HEADERS
:method = CONNECT
:protocol = websocket
:scheme = https
:path = /chat
:authority = server.example.com:443
sec-websocket-protocol = chat, superchat
sec-websocket-extensions = permessage-deflate
sec-websocket-version = 13
origin = http://www.example.com
HEADERS + END_HEADERS
:status = 200
sec-websocket-protocol = chat
DATA
WebSocket Data
DATA + END_STREAM
WebSocket Data
DATA + END_STREAM
WebSocket Data
6. Design Considerations
A more native integration with HTTP/2 is certainly possible with
larger additions to HTTP/2. This design was selected to minimize the
solution complexity while still addressing the primary concern of
running HTTP/2 and WebSockets concurrently.
7. About Intermediaries
This document does not change how WebSockets interacts with HTTP
proxies. If a client wishing to speak WebSockets connects via HTTP/2
to a HTTP proxy it should continue to use a traditional (i.e. not
with a :protocol pseudo-header) CONNECT to tunnel through that proxy
to the WebSocket server via HTTP.
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The resulting version of HTTP on that tunnel determines whether
WebSockets is initiated directly or via a modified CONNECT request
described in this document.
8. Security Considerations
[RFC6455] ensures that non WebSockets clients, especially
XMLHttpRequest based clients, cannot make a WebSocket connection.
Its primary mechanism for doing that is the use of Sec- prefixed
request headers that cannot be created by XMLHttpRequest based
clients. This specification addresses that concern in two ways:
o The CONNECT method is prohibited from being used by XMLHttpRequest
o The use of a pseudo-header is something that is connection
specific and HTTP/2 does not ever allow to be created outside of
the protocol stack.
9. IANA Considerations
This document establishes a entry for the HTTP/2 Settings Registry
that was established by [RFC7540] Section 11.3
Name: ENABLE_CONNECT_PROTOCOL
Code: 0x8
Initial Value: 0
Specification: This document
10. Acknowledgments
The 2017 HTTP Workshop had a very productive discussion that helped
determine the key problem and acceptable level of solution
complexity.
11. Normative References
[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>.
[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
DOI 10.17487/RFC6454, December 2011,
<https://www.rfc-editor.org/info/rfc6454>.
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[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011,
<https://www.rfc-editor.org/info/rfc6455>.
[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>.
[RFC7540] 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>.
Author's Address
Patrick McManus
Mozilla
Email: mcmanus@ducksong.com
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