Comment 1:

Maybe OpenBSD could fix their TCP/IP stack to make
IPV6_V6ONLY work correctly (not be ignored) before
IPv6 launch day too?

Comment 2:

Haha... it won't, as you know.
They made a decision in 2002, btw OpenBSD 3.1 and 3.2.
<http://www.openbsd.org/plus32.html>;
- Remove IPv4 mapped address support from TCP input code, and remove is_ipv6().
- Add net.inet6.ip6.v6only sysctl(8) flag.

Comment 3:

We can target cgo support for OpenBSD 5.2 (scheduled for release on 1st November 2012).
The current pthread implementation does not provide the necessary functionality required
for cgo.

Comment 4:

Re IPV6_V6ONLY, OpenBSD sockets are either IPv4-only or IPv6-only (OpenBSD does not
route IPv4 traffic to an IPv6 socket), hence IPV6_V6ONLY is meaningless. If you want an
IPv6 only socket one can create an AF_INET6 socket - that is IPv6-only by design.
See the "Interaction between IPv4/v6 sockets" section of:
http://www.openbsd.org/cgi-bin/man.cgi?query=inet6&apropos=0&sektion=0&manpath=OpenBSD+Current&arch=i386&format=html

Comment 5:

That's not the meaning I am concerned with.
The definition of listening to "tcp" in Go is to
accept both IPv4 and IPv6 connections, and
most systems let you set IPV6_V6ONLY=0
to accomplish this.  OpenBSD does not.
I expect that this will just have to be a documented
bug in package net when using OpenBSD.

Comment 6:

This issue was closed by revision 708db79.

Status changed to Fixed.