proposal: x/net/http2/h2c: allow to disable http upgrade in h2c

[xieyuschen]

Proposal Details

changes

I add an option DisableH2CUpgrade to allow server to ignore the upgrading headers from the clients, it satisfies the bahavior mentioned in rfc7230 section 6.7

A server MAY ignore a received Upgrade
header field if it wishes to continue using the current protocol on
that connection.

So after the change, if DisableH2CUpgrade is specified, the server will use http/2 to serve http/2 requests while using http1.1 for http1.1 requests.

motivation

The H2C smuggle is verbose for a server behind some proxies. As the proxy is not controlled by the service maintainers, and it does need h2c for faster internal communication among servers, the prior knowledge way is enough in such scenarios.

This PR supports this feature by adding a new option, which is backward compatible as well.

[gabyhelp]

Related Issues and Documentation

• proposal: net/http: support unencrypted HTTP/2 (h2c) #67816
• x/net/http2/h2c: H2C handler uses incorrect headers to detect upgrade #45785 (closed)
• x/net/http2/h2c: uses obsolete upgrade mechanism #63565

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[seankhliao]

I'm not sure if any more work will be done on x/net/http2 as #67816 looks like it's likely to be accepted and explicitly drops support for upgrades.

[ianlancetaylor]

CC @neild @bradfitz

[gopherbot]

Change https://go.dev/cl/602716 mentions this issue: http2/h2c: allow to disable http upgrade in h2c

[xieyuschen]

I'm not sure if any more work will be done on x/net/http2 as #67816 looks like it's likely to be accepted and explicitly drops support for upgrades.

#67816 supposed to support h2c with prior knowledge only into the standard library, I quite appreciate the idea because the upgrading mechanism is complex with many issues while hasn't been widely adapted according to RFC9113#3.1.

But regard on the proposal/pr here, I feel like it could be recognised as an improvement for existing h2c package to allow users use prior knowledge way only.

It's nice if it's accept as an intermediate step in h2c until the h2c with prior knowledge enters the stdlib and go team deprecates the package golang.org/x/net/http2/h2c.

[xieyuschen]

CC @neild @bradfitz

Hi @neild @bradfitz could i know your idea about this change?