[SCTP] Don't retransmit Gap-Acked TSNs

In general, this isn't a terrible problem at the protocol level 
(though inefficient), but causes _horrible_ problems with the way we 
do 'flight_size' calculation, eventually hitting xfer deadlock, 
since we think we already have more than enough DATA out on the wire.  

net/sctp/outqueue.c

@@ -2,7 +2,7 @@
  * Copyright (c) 1999-2000 Cisco, Inc.
  * Copyright (c) 1999-2001 Motorola, Inc.
  * Copyright (c) 2001 Intel Corp.
- * Copyright (c) 2001-2002 International Business Machines Corp.
+ * Copyright (c) 2001-2003 International Business Machines Corp.
  *
  * This file is part of the SCTP kernel reference Implementation
  *
@@ -374,6 +374,18 @@ static int sctp_flush_retran_queue(sctp_outqueue_t *q, sctp_packet_t *pkt,
 			continue;
 		}
 #endif
+
+		/* Make sure that Gap Acked TSNs are not retransmitted.  A
+		 * simple approach is just to move such TSNs out of the
+		 * way and into a 'transmitted' queue and skip to the
+		 * next chunk.
+		 */
+		if (chunk->tsn_gap_acked) {
+			list_add_tail(lchunk, &transport->transmitted);
+			lchunk = sctp_list_dequeue(lqueue);
+			continue;
+		}
+
 		/* Attempt to append this chunk to the packet. */
 		status = (*q->append_output)(pkt, chunk);