[PATCH 2/4] sctp: fix association hangs due to reneging packetsbelow the cumulative TSN ACK point

[Roberts, Lee A.]

From: Lee A. Roberts <lee.roberts@xxxxxx>

Resolve SCTP association hangs observed during SCTP stress
testing.  Observable symptoms include communications hangs
with data being held in the association reassembly and/or lobby
(ordering) queues.  Close examination of reassembly queue shows
missing packets.

In sctp_ulpq_renege_list(), do not renege packets below the
cumulative TSN ACK point.

Patch applies to linux-3.8 kernel.

Signed-off-by: Lee A. Roberts <lee.roberts@xxxxxx>
---
 net/sctp/ulpqueue.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff -uprN -X linux-3.8-vanilla/Documentation/dontdiff linux-3.8-SCTP+1/net/sctp/ulpqueue.c linux-3.8-SCTP+2/net/sctp/ulpqueue.c
--- linux-3.8-SCTP+1/net/sctp/ulpqueue.c	2013-02-18 16:58:34.000000000 -0700
+++ linux-3.8-SCTP+2/net/sctp/ulpqueue.c	2013-02-21 07:39:40.888281496 -0700
@@ -969,11 +969,16 @@ static __u16 sctp_ulpq_renege_list(struc
 
 	tsnmap = &ulpq->asoc->peer.tsn_map;
 
-	while ((skb = __skb_dequeue_tail(list)) != NULL) {
-		freed += skb_headlen(skb);
+	while ((skb = skb_peek_tail(list)) != NULL) {
 		event = sctp_skb2event(skb);
 		tsn = event->tsn;
 
+		/* Don't renege below the Cumulative TSN ACK Point. */
+		if (TSN_lte(tsn, sctp_tsnmap_get_ctsn(tsnmap)))
+			break;
+
+		__skb_unlink(skb, list);
+		freed += skb_headlen(skb);
 		sctp_ulpevent_free(event);
 		sctp_tsnmap_renege(tsnmap, tsn);
 		if (freed >= needed)
--
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