[feature] HTTP v3 support

[tsmethurst]

Currently via gin-gonic we support HTTP version 2 and below. It could be handy to investigate what's required for providing HTTP v3 support, which apparently offers quite some performance enhancements: https://en.wikipedia.org/wiki/HTTP/3.

From what I can tell, Caddy already has support for HTTP v3, and since that's written in Go it might be a good source of inspiration for us :)

[Fastidious]

How will this apply if someone is already using Caddy to proxy traffic to GtS?

[tsmethurst]

How will this apply if someone is already using Caddy to proxy traffic to GtS?

Well, if they've got HTTP3 enabled in Caddy, then the connection will be HTTP3 to Caddy, then HTTP2 to GtS most likely. If we implement HTTP3 in GtS then it'll be HTTP3 on every hop instead.

[andriibeee]

both caddy and gin use go-quic for http/3 handling and it seems like gin already supports it https://github.com/gin-gonic/gin/blob/e46bd521859fdfc83c508f1d42c92cb7f91e9fcb/gin.go#L604

[NyaaaWhatsUpDoc]

HTTP/3 is a totally different protocol, and it would be relying on those connecting to follow the Alt-Svc header to establish an HTTP/3 connection. this is fine for client to server connections, but semantically for server to server connections this feels a little off since it's effectively having redirects on the AP endpoints. it would also require updating the http client library to even support it too.

i think this is probably worth waiting until Go finish their standard library implementation of it and see from there so we can hopefully just enable it transparently, at least for the server-to-server side of things.