[PATCH 2/3] sctp: fix association hangs due to reassembly/orderinglogic

[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.  Events being reneged from the
ordering queue may correspond to multiple TSNs; identify
and renege all affected packets from the tsnmap.

Patch applies to linux-3.8 kernel.

Signed-off-by: Lee A. Roberts <lee.roberts@xxxxxx>
---
 net/sctp/ulpqueue.c |   30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 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	2013-02-20 08:17:53.679233365
-0700
@@ -962,20 +962,40 @@ static __u16 sctp_ulpq_renege_list(struc
 		struct sk_buff_head *list, __u16 needed)
 {
 	__u16 freed = 0;
-	__u32 tsn;
-	struct sk_buff *skb;
+	__u32 tsn, last_tsn;
+	struct sk_buff *skb, *flist, *last;
 	struct sctp_ulpevent *event;
 	struct sctp_tsnmap *tsnmap;
 
 	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;
+
+		/* Events in ordering queue may have multiple fragments
+		 * corresponding to additional TSNs.  Find the last one.
+		 */
+		flist = skb_shinfo(skb)->frag_list;
+		for (last = flist; flist; flist = flist->next)
+			last = flist;
+		if (last)
+			last_tsn = sctp_skb2event(last)->tsn;
+		else
+			last_tsn = tsn;
+
+		/* Unlink the event, then renege all applicable TSNs. */
+		__skb_unlink(skb, list);
+		freed += skb_headlen(skb);
 		sctp_ulpevent_free(event);
-		sctp_tsnmap_renege(tsnmap, tsn);
+		while (TSN_lte(tsn, last_tsn)) {
+			sctp_tsnmap_renege(tsnmap, tsn);
+			tsn++;
+		}
 		if (freed >= needed)
 			return freed;
 	}

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