reverse proxy: rewrite requests and responses for websocket over http2

[WeidiDeng]

Supports reverse proxying h2 websockets to backends. Fix 5565.

Requires upstream support, but can be tested with xcaddy build reverse-proxy-h2-websocket --replace golang.org/x/net=github.com/WeidiDeng/net@websocket-http2

[mholt]

Very neat, nice work @WeidiDeng 💯

[bt90]

I'm not 100% sure but a regular HTTP/2 GET request should contain the new setting parameter as outlined in RFC8441 Section 3?

[0-0] == Info: [HTTP/2] [0] ingress: read 45 bytes
[0-0] == Info: [HTTP/2] [0] <- FRAME[SETTINGS, len=36]
[0-0] == Info: [HTTP/2] [0] MAX_CONCURRENT_STREAMS: 250
[0-0] == Info: [HTTP/2] [0] ENABLE_PUSH: TRUE
[0-0] == Info: [HTTP/2] [0] notify MAX_CONCURRENT_STREAMS: 250
[0-0] == Info: [HTTP/2] [0] -> FRAME[SETTINGS, len=18]
[0-0] == Info: [HTTP/2] [0] -> FRAME[SETTINGS, ack=1]
[0-0] == Info: [HTTP/2] [0] -> FRAME[WINDOW_UPDATE, incr=1048510465]
[0-0] => Send SSL data, 5 bytes (0x5)
0000: 17 03 03 00 5a                                  ....Z
[0-0] => Send SSL data, 1 bytes (0x1)
0000: 17                                              .
[0-0] == Info: [HTTP/2] [0] egress: wrote 73 bytes
[0-0] == Info: [HTTP/2] cf_connect() -> 0, 1,
[0-0] == Info: using HTTP/2
[0-0] == Info: [HTTP/2] [1] OPENED stream for https://xxxxxxx.xxx/

Tested via curl:

curl --trace request.dump --trace-config http/2 https://example.com

[WeidiDeng]

i'm not sure about curl debug dump. But I tested this with my Chrome and it works. The setting frame is send at the start of a new http2 connection, so it's sent regardless of the method client uses.

Even without my patch, golang http2 sends the following settings:

The output doesn't list all of them.

[bt90]

Successfully tested in Firefox 👍