socket: Make shutdown() wake up a blocked accept().

A blocking accept (and some other operations) waits on &so->so_timeo. Once
it wakes up, it will detect the SBS_CANTRCVMORE bit.

The error from accept() is [ECONNABORTED] which is not the nicest one -- the
thread calling accept() needs to know out-of-band what is happening.

A spurious wakeup on so->so_timeo appears harmless (sleep retried) except
when lingering on close (SO_LINGER, and in that case there is no descriptor
to call shutdown() on) so this should be fairly safe.

A shutdown() already woke up a blocked accept() for TCP sockets, but not for
Unix domain sockets. This fix is generic for all domains.

This patch was sent to -hackers@ and -net@ on April 5.

MFC after:	2 weeks

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index ea55e4e2411b..7986c4b1b6c8 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -2429,9 +2429,11 @@ soshutdown(struct socket *so, int how)
 		sorflush(so);
 	if (how != SHUT_RD) {
 		error = (*pr->pr_usrreqs->pru_shutdown)(so);
+		wakeup(&so->so_timeo);
 		CURVNET_RESTORE();
 		return (error);
 	}
+	wakeup(&so->so_timeo);
 	CURVNET_RESTORE();
 	return (0);
 }