IPv6 support in backend

[jengelh]

The backend is lacking IPv6 support.

./BSRPC.pm:    socket(S, PF_INET, SOCK_STREAM, $tcpproto) || die("socket: $!\n");
./BSServer.pm:      socket($s , PF_INET, SOCK_STREAM, $tcpproto) || die "socket: $!\n";
./BSWatcher.pm:  socket($fd, PF_INET, SOCK_STREAM, $tcpproto) || die("socket: $!\n");

By switching this to PF_INET6, and some sockaddr_in calls to pack_sockaddr_in6, it should be possible to offer both (as IPv4 connections get mapped onto v6 by way of ::ffff:x.y.z.a).

[laf0rge]

This is really surprising in 2022, particularly as the communication is based on HTTP. I have an untested patch in https://github.com/laf0rge/open-build-service/tree/ipv6 but currently don't have a development setup with a "playground" OBS instance to test it. Maybe it can serve a s a basis if somebody wants to pick this up?

[laf0rge]

pinging @mlschroe as he covered that topic in #12550

[mlschroe]

I've got it already mostly running, it just needs some polishing.

[laf0rge]

I think this can also be closed now that 6436640 is merged?

[mlschroe]

Yes, right. Sorry.