selftests/net/af_unix: test listen() rejects wrong socket states

Add a regression test for the unix_listen() state check. The key case is
listen() on a bound socket that has already been connected: it is no
longer in TCP_CLOSE or TCP_LISTEN, so it must fail with EINVAL. A
prepare_peercred() call slipped in ahead of that check once left err at 0
and made listen() silently succeed there instead; this guards against a
repeat.

The neighbouring outcomes are covered too so they cannot regress the same
way: a bound socket in TCP_CLOSE listens fine, calling listen() again on a
socket already in TCP_LISTEN is allowed, and an unbound socket fails with
EINVAL.

Each case runs for both listenable socket types (SOCK_STREAM and
SOCK_SEQPACKET) and both pathname and abstract addresses.

Fixes: fd0a109a0f6b ("net, pidfs: prepare for handing out pidfds for reaped sk->sk_peer_pid")
Signed-off-by: John Ericson <mail@johnericson.me>
Link: https://patch.msgid.link/20260718182903.2295560-2-John.Ericson@Obsidian.Systems
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions