[SCTP]: Fix 'fast retransmit' to send a TSN only once.

SCTP used to "fast retransmit" a TSN every time we hit the number
of missing reports for the TSN.  However the Implementers Guide
specifies that we should only "fast retransmit" a given TSN once.
Subsequent retransmits should be timeouts only. Also change the
number of missing reports to 3 as per the latest IG(similar to TCP).

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 9 insertions, 7 deletions

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 8c522ae031bb..072f407848a6 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -700,7 +700,7 @@ struct sctp_chunk {
         __u8 ecn_ce_done;       /* Have we processed the ECN CE bit? */
         __u8 pdiscard;          /* Discard the whole packet now? */
         __u8 tsn_gap_acked;     /* Is this chunk acked by a GAP ACK? */
-        __u8 fast_retransmit;    /* Is this chunk fast retransmitted? */
+        __s8 fast_retransmit;    /* Is this chunk fast retransmitted? */
         __u8 tsn_missing_report; /* Data chunk missing counter. */
 };
 
diff --git a/net/sctp/output.c b/net/sctp/output.c
index a40991ef72c9..437cba7260a4 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -608,7 +608,7 @@ static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet,
          *    When a Fast Retransmit is being performed the sender SHOULD
          *    ignore the value of cwnd and SHOULD NOT delay retransmission.
          */
-        if (!chunk->fast_retransmit)
+        if (chunk->fast_retransmit <= 0)
                 if (transport->flight_size >= transport->cwnd) {
                         retval = SCTP_XMIT_RWND_FULL;
                         goto finish;
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index efb72faba20c..f148f9576dd2 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -406,7 +406,7 @@ void sctp_retransmit_mark(struct sctp_outq *q,
                  * chunks that are not yet acked should be added to the
                  * retransmit queue.
                  */
-                if ((fast_retransmit && chunk->fast_retransmit) ||
+                if ((fast_retransmit && (chunk->fast_retransmit > 0)) ||
                    (!fast_retransmit && !chunk->tsn_gap_acked)) {
                         /* RFC 2960 6.2.1 Processing a Received SACK
                          *
@@ -603,7 +603,8 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
                         /* Mark the chunk as ineligible for fast retransmit 
                          * after it is retransmitted.
                          */
-                        chunk->fast_retransmit = 0;
+                        if (chunk->fast_retransmit > 0)
+                                chunk->fast_retransmit = -1;
 
                         *start_timer = 1;
                         q->empty = 0;
@@ -621,7 +622,8 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
                         list_for_each(lchunk1, lqueue) {
                                 chunk1 = list_entry(lchunk1, struct sctp_chunk,
                                                     transmitted_list);
-                                chunk1->fast_retransmit = 0;
+                                if (chunk1->fast_retransmit > 0)
+                                        chunk1->fast_retransmit = -1;
                         }
                 }
         }
@@ -1562,11 +1564,11 @@ static void sctp_mark_missing(struct sctp_outq *q,
                 /*
                  * M4) If any DATA chunk is found to have a
                  * 'TSN.Missing.Report'
-                 * value larger than or equal to 4, mark that chunk for
+                 * value larger than or equal to 3, mark that chunk for
                  * retransmission and start the fast retransmit procedure.
                  */
 
-                if (chunk->tsn_missing_report >= 4) {
+                if (chunk->tsn_missing_report >= 3) {
                         chunk->fast_retransmit = 1;
                         do_fast_retransmit = 1;
                 }