sctp: Select a working primary during sctp_connectx()

When sctp_connectx() is used, we pick the first address as
primary, even though it may not have worked.  This results
in excessive retransmits and poor performance.  We should
select the address that the association was established with.
Reported-by: Thomas Dreibholz <dreibh@iem.uni-due.de>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

net/sctp/associola.c

@@ -512,7 +512,13 @@ void sctp_assoc_set_primary(struct sctp_association *asoc,
 	 * to this destination address earlier. The sender MUST set
 	 * CYCLING_CHANGEOVER to indicate that this switch is a
 	 * double switch to the same destination address.
+	 *
+	 * Really, only bother is we have data queued or outstanding on
+	 * the association.
 	 */
+	if (!asoc->outqueue.outstanding_bytes && !asoc->outqueue.out_qlen)
+		return;
+
 	if (transport->cacc.changeover_active)
 		transport->cacc.cycling_changeover = changeover;
 

net/sctp/sm_sideeffect.c

@@ -1418,6 +1418,8 @@ static int sctp_cmd_interpreter(sctp_event_t event_type,
 			asoc->init_last_sent_to = t;
 			chunk->transport = t;
 			t->init_sent_count++;
+			/* Set the new transport as primary */
+			sctp_assoc_set_primary(asoc, t);
 			break;
 
 		case SCTP_CMD_INIT_RESTART: