From fdada4b1d06e7ba496cc0badc521a16b3635267a Mon Sep 17 00:00:00 2001
From: mvs <mvs@openbsd.org>
Date: Fri, 22 Mar 2024 17:34:11 +0000
Subject: [PATCH] Use sorflush() instead of direct unp_scan(..., unp_discard)
 to discard dead unix(4) sockets.

The difference in direct unp_scan() and sorflush() is the mbuf(9) chain.
For the first case it is still linked to the `so_rcv', for the second it
is not. This is required to make `sb_mtx' mutex(9) the only `so_rcv'
sockbuf protection and remove socket re-locking from the most of
uipc_*send() paths. The unlinked mbuf(9) chain doesn't require any
protection, so this allows to perform sleeping unp_discard() lockless.

Also, the mbuf(9) chain of the discarded socket still contains addresses
of file descriptors and it is much safer to unlink it before FRELE()
them. This is the reason to commit this diff standalone.

ok bluhm
---
 sys/kern/uipc_socket.c | 3 +--
 sys/kern/uipc_usrreq.c | 4 ++--
 sys/sys/socketvar.h    | 3 ++-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index 85032afee9d..7b04935ef0d 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_socket.c,v 1.320 2024/02/12 22:48:27 mvs Exp $	*/
+/*	$OpenBSD: uipc_socket.c,v 1.321 2024/03/22 17:34:11 mvs Exp $	*/
 /*	$NetBSD: uipc_socket.c,v 1.21 1996/02/04 02:17:52 christos Exp $	*/
 
 /*
@@ -65,7 +65,6 @@ void	sotask(void *);
 void	soreaper(void *);
 void	soput(void *);
 int	somove(struct socket *, int);
-void	sorflush(struct socket *);
 
 void	filt_sordetach(struct knote *kn);
 int	filt_soread(struct knote *kn, long hint);
diff --git a/sys/kern/uipc_usrreq.c b/sys/kern/uipc_usrreq.c
index b01cad482d6..7dc83db4d51 100644
--- a/sys/kern/uipc_usrreq.c
+++ b/sys/kern/uipc_usrreq.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_usrreq.c,v 1.201 2024/03/17 19:47:08 mvs Exp $	*/
+/*	$OpenBSD: uipc_usrreq.c,v 1.202 2024/03/22 17:34:11 mvs Exp $	*/
 /*	$NetBSD: uipc_usrreq.c,v 1.18 1996/02/09 19:00:50 christos Exp $	*/
 
 /*
@@ -1438,7 +1438,7 @@ unp_gc(void *arg __unused)
 				 */
 				so = unp->unp_socket;
 				solock(so);
-				unp_scan(so->so_rcv.sb_mb, unp_discard);
+				sorflush(so);
 				sounlock(so);
 			}
 		}
diff --git a/sys/sys/socketvar.h b/sys/sys/socketvar.h
index 9ef1cafe71a..dc34b1c5c61 100644
--- a/sys/sys/socketvar.h
+++ b/sys/sys/socketvar.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: socketvar.h,v 1.124 2024/02/12 22:48:27 mvs Exp $	*/
+/*	$OpenBSD: socketvar.h,v 1.125 2024/03/22 17:34:11 mvs Exp $	*/
 /*	$NetBSD: socketvar.h,v 1.18 1996/02/09 18:25:38 christos Exp $	*/
 
 /*-
@@ -394,6 +394,7 @@ int	sosend(struct socket *, struct mbuf *, struct uio *,
 	    struct mbuf *, struct mbuf *, int);
 int	sosetopt(struct socket *, int, int, struct mbuf *);
 int	soshutdown(struct socket *, int);
+void	sorflush(struct socket *);
 void	sowakeup(struct socket *, struct sockbuf *);
 void	sorwakeup(struct socket *);
 void	sowwakeup(struct socket *);
-- 
2.20.1