[SCTP] Flag a pmtu change request

Currently, if the socket is owned by the user, we drop the ICMP
message.  As a result SCTP forgets that path MTU changed and
never adjusting it's estimate.  This causes all subsequent
packets to be fragmented.  With this patch, we'll flag the association
that it needs to udpate it's estimate based on the already updated
routing information.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Sridhar Samudrala <sri@us.ibm.com>
diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index df94e3c..498edb0 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1231,6 +1231,10 @@
 	/* Get the lowest pmtu of all the transports. */
 	list_for_each(pos, &asoc->peer.transport_addr_list) {
 		t = list_entry(pos, struct sctp_transport, transports);
+		if (t->pmtu_pending && t->dst) {
+			sctp_transport_update_pmtu(t, dst_mtu(t->dst));
+			t->pmtu_pending = 0;
+		}
 		if (!pmtu || (t->pathmtu < pmtu))
 			pmtu = t->pathmtu;
 	}