Introduce sbreserve_locked(), which asserts the socket buffer lock on

the socket buffer having its limits adjusted.  sbreserve() now acquires
the lock before calling sbreserve_locked().  In soreserve(), acquire
socket buffer locks across read-modify-writes of socket buffer fields,
and calls into sbreserve/sbrelease; make sure to acquire in keeping
with the socket buffer lock order.  In tcp_mss(), acquire the socket
buffer lock in the calling context so that we have atomic read-modify
-write on buffer sizes.

1 files changed, 6 insertions, 2 deletions

diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index 581fe9a..cab3354 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -2990,6 +2990,7 @@ tcp_mss(tp, offer)
 	 * Make the socket buffers an integral number of mss units;
 	 * if the mss is larger than the socket buffer, decrease the mss.
 	 */
+	SOCKBUF_LOCK(&so->so_snd);
 	if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe)
 		bufsize = metrics.rmx_sendpipe;
 	else
@@ -3001,10 +3002,12 @@ tcp_mss(tp, offer)
 		if (bufsize > sb_max)
 			bufsize = sb_max;
 		if (bufsize > so->so_snd.sb_hiwat)
-			(void)sbreserve(&so->so_snd, bufsize, so, NULL);
+			(void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
 	}
+	SOCKBUF_UNLOCK(&so->so_snd);
 	tp->t_maxseg = mss;
 
+	SOCKBUF_LOCK(&so->so_rcv);
 	if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe)
 		bufsize = metrics.rmx_recvpipe;
 	else
@@ -3014,8 +3017,9 @@ tcp_mss(tp, offer)
 		if (bufsize > sb_max)
 			bufsize = sb_max;
 		if (bufsize > so->so_rcv.sb_hiwat)
-			(void)sbreserve(&so->so_rcv, bufsize, so, NULL);
+			(void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
 	}
+	SOCKBUF_UNLOCK(&so->so_rcv);
 	/*
 	 * While we're here, check the others too
 	 */