sctp: Send user messages to the lower layer as one

Currenlty, sctp breaks up user messages into fragments and
sends each fragment to the lower layer by itself.  This means
that for each fragment we go all the way down the stack
and back up.  This also discourages bundling of multiple
fragments when they can fit into a sigle packet (ex: due
to user setting a low fragmentation threashold).

We introduce a new command SCTP_CMD_SND_MSG and hand the
whole message down state machine.  The state machine and
the side-effect parser will cork the queue, add all chunks
from the message to the queue, and then un-cork the queue
thus causing the chunks to get transmitted.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

1 files changed, 14 insertions, 12 deletions

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index a7e544e3f28a..95a5623d79a0 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1814,20 +1814,22 @@ SCTP_STATIC int sctp_sendmsg(struct kiocb *iocb, struct sock *sk,
 		sctp_set_owner_w(chunk);
 
 		chunk->transport = chunk_tp;
-
-		/* Send it to the lower layers.  Note:  all chunks
-		 * must either fail or succeed.   The lower layer
-		 * works that way today.  Keep it that way or this
-		 * breaks.
-		 */
-		err = sctp_primitive_SEND(asoc, chunk);
-		/* Did the lower layer accept the chunk? */
-		if (err)
-			sctp_chunk_free(chunk);
-		SCTP_DEBUG_PRINTK("We sent primitively.\n");
 	}
 
-	sctp_datamsg_put(datamsg);
+	/* Send it to the lower layers.  Note:  all chunks
+	 * must either fail or succeed.   The lower layer
+	 * works that way today.  Keep it that way or this
+	 * breaks.
+	 */
+	err = sctp_primitive_SEND(asoc, datamsg);
+	/* Did the lower layer accept the chunk? */
+	if (err)
+		sctp_datamsg_free(datamsg);
+	else
+		sctp_datamsg_put(datamsg);
+
+	SCTP_DEBUG_PRINTK("We sent primitively.\n");
+
 	if (err)
 		goto out_free;
 	else