sctp: introduce sctp_dst_mtu

Which makes sure that the MTU respects the minimum value of
SCTP_DEFAULT_MINSEGMENT and that it is correctly aligned.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index a290254..039fdb86 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1405,11 +1405,9 @@ void sctp_assoc_sync_pmtu(struct sctp_association *asoc)
 		return;
 
 	/* Get the lowest pmtu of all the transports. */
-	list_for_each_entry(t, &asoc->peer.transport_addr_list,
-				transports) {
+	list_for_each_entry(t, &asoc->peer.transport_addr_list, transports) {
 		if (t->pmtu_pending && t->dst) {
-			sctp_transport_update_pmtu(
-					t, SCTP_TRUNC4(dst_mtu(t->dst)));
+			sctp_transport_update_pmtu(t, sctp_dst_mtu(t->dst));
 			t->pmtu_pending = 0;
 		}
 		if (!pmtu || (t->pathmtu < pmtu))