Listen on BSD is IPv4 or IPv6 only about yggdrasil-go

[Arceliar]

Followup, not sure if this is true of all BSDs, but I'm told that OpenBSD intentionally doesn't support dual-stack sockets. So the fix here is to listen on two sockets, one of which is bound to IPv4, and the other to IPv6.

This is tedious but not technically difficult to do. The bigger question is how to handle it in the config. We may need to support multiple listen addresses, or else figure out that the undefined address is used (and then listen on all addresses in such cases). If we allow for multiple addresses, then we need to handle the case where someone configures multiple addresses of the same type, which quickly becomes complicated. Perhaps, in the short term, we should only use a listen port (and then listen on all addresses on both IPv4 and IPv6), until the multiple address question is answered.

[Arceliar]

It sounds like another alternative is to do nothing, and continue to only listen on all IPv6 addresses on OpenBSD. OpenBSD users who need to listen on IPv4 could set up a 4-to-6 relay, or something like that.

[neilalexander]

If we do nothing then the user can fix this with relayd using something like this, as trn mentioned in the Matrix channel:

relay 6-to-4 {
  forward to 127.0.0.1 port 999
  listen on fd00::1 port 999
}

This isn't ideal but it does mean we aren't adding more platform-specific behaviour than is required. It'd be worth seeing if this is also true on FreeBSD and NetBSD.

[neilalexander]

Some quick research:

• FreeBSD 11 netstat -an shows tcp46/udp46. Accepts connections on both ::1 and 127.0.0.1.
• NetBSD 7.1.1 netstat -an shows tcp6/udp6. Accepts connections on both ::1 and 127.0.0.1.
• OpenBSD 6.2 netstat -an shows tcp6/udp6. Accepts connections on ::1 but not 127.0.0.1.

Seems that this issue is specific to OpenBSD.

[Arceliar]

I guess it should be enough for now to provide a workaround in the OpenBSD documentation.

[Arceliar]

#57 covers this well enough for now, I guess.