sctp: Start T3-RTX timer when fast retransmitting lowest TSN

When we are trying to fast retransmit the lowest outstanding TSN, we
need to restart the T3-RTX timer, so that subsequent timeouts will
correctly tag all the packets necessary for retransmissions.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Tested-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 33 insertions, 13 deletions

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 59edfd25a19c..5d3c441e84d3 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -208,6 +208,7 @@ void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
         INIT_LIST_HEAD(&q->sacked);
         INIT_LIST_HEAD(&q->abandoned);
 
+        q->fast_rtx = 0;
         q->outstanding_bytes = 0;
         q->empty = 1;
         q->cork  = 0;
@@ -500,6 +501,7 @@ void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
         case SCTP_RTXR_FAST_RTX:
                 SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
                 sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
+                q->fast_rtx = 1;
                 break;
         case SCTP_RTXR_PMTUD:
                 SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
@@ -543,10 +545,13 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
         sctp_xmit_t status;
         struct sctp_chunk *chunk, *chunk1;
         struct sctp_association *asoc;
+        int fast_rtx;
         int error = 0;
+        int timer = 0;
 
         asoc = q->asoc;
         lqueue = &q->retransmit;
+        fast_rtx = q->fast_rtx;
 
         /* RFC 2960 6.3.3 Handle T3-rtx Expiration
          *
@@ -587,13 +592,12 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
                 switch (status) {
                 case SCTP_XMIT_PMTU_FULL:
                         /* Send this packet.  */
-                        if ((error = sctp_packet_transmit(pkt)) == 0)
-                                *start_timer = 1;
+                        error = sctp_packet_transmit(pkt);
 
                         /* If we are retransmitting, we should only
                          * send a single packet.
                          */
-                        if (rtx_timeout) {
+                        if (rtx_timeout || fast_rtx) {
                                 list_add(lchunk, lqueue);
                                 lchunk = NULL;
                         }
@@ -603,8 +607,7 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 
                 case SCTP_XMIT_RWND_FULL:
                         /* Send this packet. */
-                        if ((error = sctp_packet_transmit(pkt)) == 0)
-                                *start_timer = 1;
+                        error = sctp_packet_transmit(pkt);
 
                         /* Stop sending DATA as there is no more room
                          * at the receiver.
@@ -615,8 +618,7 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
 
                 case SCTP_XMIT_NAGLE_DELAY:
                         /* Send this packet. */
-                        if ((error = sctp_packet_transmit(pkt)) == 0)
-                                *start_timer = 1;
+                        error = sctp_packet_transmit(pkt);
 
                         /* Stop sending DATA because of nagle delay. */
                         list_add(lchunk, lqueue);
@@ -635,7 +637,14 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
                         if (chunk->fast_retransmit > 0)
                                 chunk->fast_retransmit = -1;
 
-                        *start_timer = 1;
+                        /* Force start T3-rtx timer when fast retransmitting
+                         * the earliest outstanding TSN
+                         */
+                        if (!timer && fast_rtx &&
+                            ntohl(chunk->subh.data_hdr->tsn) ==
+                                             asoc->ctsn_ack_point + 1)
+                                timer = 2;
+
                         q->empty = 0;
 
                         /* Retrieve a new chunk to bundle. */
@@ -643,12 +652,16 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
                         break;
                 }
 
+                /* Set the timer if there were no errors */
+                if (!error && !timer)
+                        timer = 1;
+
                 /* If we are here due to a retransmit timeout or a fast
                  * retransmit and if there are any chunks left in the retransmit
                  * queue that could not fit in the PMTU sized packet, they need
                  * to be marked as ineligible for a subsequent fast retransmit.
                  */
-                if (rtx_timeout && !lchunk) {
+                if (rtx_timeout && fast_rtx) {
                         list_for_each_entry(chunk1, lqueue, transmitted_list) {
                                 if (chunk1->fast_retransmit > 0)
                                         chunk1->fast_retransmit = -1;
@@ -656,6 +669,12 @@ static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
                 }
         }
 
+        *start_timer = timer;
+
+        /* Clear fast retransmit hint */
+        if (fast_rtx)
+                q->fast_rtx = 0;
+
         return error;
 }
 
@@ -862,7 +881,8 @@ int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
                                                     rtx_timeout, &start_timer);
 
                         if (start_timer)
-                                sctp_transport_reset_timers(transport);
+                                sctp_transport_reset_timers(transport,
+                                                            start_timer-1);
 
                         /* This can happen on COOKIE-ECHO resend.  Only
                          * one chunk can get bundled with a COOKIE-ECHO.
@@ -977,7 +997,7 @@ int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
                         list_add_tail(&chunk->transmitted_list,
                                       &transport->transmitted);
 
-                        sctp_transport_reset_timers(transport);
+                        sctp_transport_reset_timers(transport, start_timer-1);
 
                         q->empty = 0;
 
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 9647fb277221..3f34f61221ec 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -191,7 +191,7 @@ static void sctp_transport_destroy(struct sctp_transport *transport)
 /* Start T3_rtx timer if it is not already running and update the heartbeat
  * timer.  This routine is called every time a DATA chunk is sent.
  */
-void sctp_transport_reset_timers(struct sctp_transport *transport)
+void sctp_transport_reset_timers(struct sctp_transport *transport, int force)
 {
         /* RFC 2960 6.3.2 Retransmission Timer Rules
          *
@@ -201,7 +201,7 @@ void sctp_transport_reset_timers(struct sctp_transport *transport)
          * address.
          */
 
-        if (!timer_pending(&transport->T3_rtx_timer))
+        if (force || !timer_pending(&transport->T3_rtx_timer))
                 if (!mod_timer(&transport->T3_rtx_timer,
                                jiffies + transport->rto))
                         sctp_transport_hold(transport);