[SCTP]: Include sk_buff overhead while updating the peer's receive window.

Currently if the sender is sending small messages, it can cause a receiver
to run out of receive buffer space even when the advertised receive window
is still open and results in packet drops and retransmissions. Including
a overhead while updating the sender's view of peer receive window will
reduce the chances of receive buffer space overshooting the receive window.

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

2 files changed, 10 insertions, 3 deletions

diff --git a/net/sctp/output.c b/net/sctp/output.c
index cdc5a3936766..3ef4351dd956 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -633,7 +633,7 @@ static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet,
                  * data will fit or delay in hopes of bundling a full
                  * sized packet.
                  */
-                if (len < asoc->pathmtu - packet->overhead) {
+                if (len < asoc->frag_point) {
                         retval = SCTP_XMIT_NAGLE_DELAY;
                         goto finish;
                 }
@@ -645,7 +645,13 @@ static sctp_xmit_t sctp_packet_append_data(struct sctp_packet *packet,
         /* Keep track of how many bytes are in flight to the receiver. */
         asoc->outqueue.outstanding_bytes += datasize;
 
-        /* Update our view of the receiver's rwnd. */
+        /* Update our view of the receiver's rwnd. Include sk_buff overhead
+         * while updating peer.rwnd so that it reduces the chances of a
+         * receiver running out of receive buffer space even when receive
+         * window is still open. This can happen when a sender is sending
+         * sending small messages.
+         */
+        datasize += sizeof(struct sk_buff);
         if (datasize < rwnd)
                 rwnd -= datasize;
         else
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 37074a39ecbb..739582415bf6 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -416,7 +416,8 @@ void sctp_retransmit_mark(struct sctp_outq *q,
                          * (Section 7.2.4)), add the data size of those
                          * chunks to the rwnd.
                          */
-                        q->asoc->peer.rwnd += sctp_data_size(chunk);
+                        q->asoc->peer.rwnd += (sctp_data_size(chunk) +
+                                                sizeof(struct sk_buff));
                         q->outstanding_bytes -= sctp_data_size(chunk);
                         transport->flight_size -= sctp_data_size(chunk);