sctp: do not update a_rwnd if we are not issuing a sack

marceloleitner · davem330 · commit 07b4d6a17494 · 2016-03-20T16:31:11.000-04:00
The SACK can be lost pretty much elsewhere, but if its allocation fail,
we know we are not sending it, so it is better to revert a_rwnd to its
previous value as this may give it a chance to issue a window update
later.

Signed-off-by: Marcelo Ricardo Leitner &lt;marcelo.leitner@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
@@ -215,10 +215,14 @@ static int sctp_gen_sack(struct sctp_association *asoc, int force,
 		sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
 				SCTP_TO(SCTP_EVENT_TIMEOUT_SACK));
 	} else {
+		__u32 old_a_rwnd = asoc->a_rwnd;
+
 		asoc->a_rwnd = asoc->rwnd;
 		sack = sctp_make_sack(asoc);
-		if (!sack)
+		if (!sack) {
+			asoc->a_rwnd = old_a_rwnd;
 			goto nomem;
+		}
 
 		asoc->peer.sack_needed = 0;
 		asoc->peer.sack_cnt = 0;
