1 files changed, 16 insertions, 5 deletions

diff --git a/net/sctp/chunk.c b/net/sctp/chunk.c
index 9292294dbc12..7acaf15679b6 100644
--- a/net/sctp/chunk.c
+++ b/net/sctp/chunk.c
@@ -207,14 +207,25 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
         whole = 0;
         first_len = max;
 
+        /* Check to see if we have a pending SACK and try to let it be bundled
+         * with this message.  Do this if we don't have any data queued already.
+         * To check that, look at out_qlen and retransmit list.
+         * NOTE: we will not reduce to account for SACK, if the message would
+         * not have been fragmented.
+         */
+        if (timer_pending(&asoc->timers[SCTP_EVENT_TIMEOUT_SACK]) &&
+            asoc->outqueue.out_qlen == 0 &&
+            list_empty(&asoc->outqueue.retransmit) &&
+            msg_len > max)
+                max_data -= WORD_ROUND(sizeof(sctp_sack_chunk_t));
+
         /* Encourage Cookie-ECHO bundling. */
-        if (asoc->state < SCTP_STATE_COOKIE_ECHOED) {
+        if (asoc->state < SCTP_STATE_COOKIE_ECHOED)
                 max_data -= SCTP_ARBITRARY_COOKIE_ECHO_LEN;
 
-                /* This is the biggesr first_len we can have */
-                if (first_len > max_data)
-                        first_len = max_data;
-        }
+        /* Now that we adjusted completely, reset first_len */
+        if (first_len > max_data)
+                first_len = max_data;
 
         /* Account for a different sized first fragment */
         if (msg_len >= first_len) {