SCTP: Do not retransmit chunks that are newer then rtt.

When performing a retransmit, do not include the chunk if
it was sent less then 1 rtt ago.  The reason is that we
may receive the SACK very soon and wouldn't retransmit.
Suggested by Randy Stewart.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

net/sctp/outqueue.c

@@ -421,6 +421,13 @@ void sctp_retransmit_mark(struct sctp_outq *q,
 		 */
 		if ((fast_retransmit && (chunk->fast_retransmit > 0)) ||
 		   (!fast_retransmit && !chunk->tsn_gap_acked)) {
+			/* If this chunk was sent less then 1 rto ago, do not
+			 * retransmit this chunk, but give the peer time
+			 * to acknowlege it.
+			 */
+			if ((jiffies - chunk->sent_at) < transport->rto)
+				continue;
+
 			/* RFC 2960 6.2.1 Processing a Received SACK
 			 *
 			 * C) Any time a DATA chunk is marked for