add http/3 local_port support

[yixinin]

#2736

[seanmonstar]

I see, and this option would really only apply to HTTP/3 because UDP? It would be problematic for HTTP/1 and 2 because once the port is used, all other connections would fail.

If I have that right, should the docs point out that this option only applies for HTTP/3? (I know curl has a similar option for all connections, and also LOCALPORTRANGE to try to handle the port already used, but seems annoying to me.)

[yixinin]

problematic

I see, and this option would really only apply to HTTP/3 because UDP? It would be problematic for HTTP/1 and 2 because once the port is used, all other connections would fail.

If I have that right, should the docs point out that this option only applies for HTTP/3? (I know curl has a similar option for all connections, and also LOCALPORTRANGE to try to handle the port already used, but seems annoying to me.)

correct, this local_port option only used for HTTP/3 (QUIC/UDP connection), it wont affect HTTP/1 or 2 (TCP connection), cause they have different 5-tuple, in most cases we don't need specify local_port, some special network environment especially P2P(Peer-To-Peer connection) need use local port which by (stun -> hole punch) through NAT.

[seanmonstar]

Sounds fair to me. Looks like CI is failing, want to fix and adjust the docs that this only affects HTTP/3?