4 files changed, 54 insertions, 23 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 37e982510bea..880dae2ca87b 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -738,6 +738,7 @@ struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
 
         peer->partial_bytes_acked = 0;
         peer->flight_size = 0;
+        peer->burst_limited = 0;
 
         /* Set the transport's RTO.initial value */
         peer->rto = asoc->rto_initial;
diff --git a/net/sctp/output.c b/net/sctp/output.c
index 9e8e0ea844be..b210d2077e28 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -615,7 +615,6 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
         sctp_xmit_t retval = SCTP_XMIT_OK;
         size_t datasize, rwnd, inflight, flight_size;
         struct sctp_transport *transport = packet->transport;
-        __u32 max_burst_bytes;
         struct sctp_association *asoc = transport->asoc;
         struct sctp_outq *q = &asoc->outqueue;
 
@@ -648,28 +647,6 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
                 }
         }
 
-        /* sctpimpguide-05 2.14.2
-         * D) When the time comes for the sender to
-         * transmit new DATA chunks, the protocol parameter Max.Burst MUST
-         * first be applied to limit how many new DATA chunks may be sent.
-         * The limit is applied by adjusting cwnd as follows:
-         *      if ((flightsize + Max.Burst * MTU) < cwnd)
-         *              cwnd = flightsize + Max.Burst * MTU
-         */
-        max_burst_bytes = asoc->max_burst * asoc->pathmtu;
-        if ((flight_size + max_burst_bytes) < transport->cwnd) {
-                transport->cwnd = flight_size + max_burst_bytes;
-                SCTP_DEBUG_PRINTK("%s: cwnd limited by max_burst: "
-                                  "transport: %p, cwnd: %d, "
-                                  "ssthresh: %d, flight_size: %d, "
-                                  "pba: %d\n",
-                                  __func__, transport,
-                                  transport->cwnd,
-                                  transport->ssthresh,
-                                  transport->flight_size,
-                                  transport->partial_bytes_acked);
-        }
-
         /* RFC 2960 6.1  Transmission of DATA Chunks
          *
          * B) At any given time, the sender MUST NOT transmit new data
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 5732661c87d3..2f2377369e2b 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -931,6 +931,14 @@ static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
                                 goto sctp_flush_out;
                 }
 
+                /* Apply Max.Burst limitation to the current transport in
+                 * case it will be used for new data.  We are going to
+                 * rest it before we return, but we want to apply the limit
+                 * to the currently queued data.
+                 */
+                if (transport)
+                        sctp_transport_burst_limited(transport);
+
                 /* Finally, transmit new packets.  */
                 while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
                         /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
@@ -976,6 +984,10 @@ static int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
                                 packet = &transport->packet;
                                 sctp_packet_config(packet, vtag,
                                                    asoc->peer.ecn_capable);
+                                /* We've switched transports, so apply the
+                                 * Burst limit to the new transport.
+                                 */
+                                sctp_transport_burst_limited(transport);
                         }
 
                         SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
@@ -1070,6 +1082,9 @@ sctp_flush_out:
                 packet = &t->packet;
                 if (!sctp_packet_empty(packet))
                         error = sctp_packet_transmit(packet);
+
+                /* Clear the burst limited state, if any */
+                sctp_transport_burst_reset(t);
         }
 
         return error;
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 2df29cbdaf5a..9a6cb22d129f 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -576,6 +576,43 @@ void sctp_transport_lower_cwnd(struct sctp_transport *transport,
                           transport->cwnd, transport->ssthresh);
 }
 
+/* Apply Max.Burst limit to the congestion window:
+ * sctpimpguide-05 2.14.2
+ * D) When the time comes for the sender to
+ * transmit new DATA chunks, the protocol parameter Max.Burst MUST
+ * first be applied to limit how many new DATA chunks may be sent.
+ * The limit is applied by adjusting cwnd as follows:
+ *      if ((flightsize+ Max.Burst * MTU) < cwnd)
+ *              cwnd = flightsize + Max.Burst * MTU
+ */
+
+void sctp_transport_burst_limited(struct sctp_transport *t)
+{
+        struct sctp_association *asoc = t->asoc;
+        u32 old_cwnd = t->cwnd;
+        u32 max_burst_bytes;
+
+        if (t->burst_limited)
+                return;
+
+        max_burst_bytes = t->flight_size + (asoc->max_burst * asoc->pathmtu);
+        if (max_burst_bytes < old_cwnd) {
+                t->cwnd = max_burst_bytes;
+                t->burst_limited = old_cwnd;
+        }
+}
+
+/* Restore the old cwnd congestion window, after the burst had it's
+ * desired effect.
+ */
+void sctp_transport_burst_reset(struct sctp_transport *t)
+{
+        if (t->burst_limited) {
+                t->cwnd = t->burst_limited;
+                t->burst_limited = 0;
+        }
+}
+
 /* What is the next timeout value for this transport? */
 unsigned long sctp_transport_timeout(struct sctp_transport *t)
 {
@@ -598,6 +635,7 @@ void sctp_transport_reset(struct sctp_transport *t)
          * (see Section 6.2.1)
          */
         t->cwnd = min(4*asoc->pathmtu, max_t(__u32, 2*asoc->pathmtu, 4380));
+        t->burst_limited = 0;
         t->ssthresh = asoc->peer.i.a_rwnd;
         t->last_rto = t->rto = asoc->rto_initial;
         t->rtt = 0;