Update the metric of a neighbour's routes when its rttcost changes

Note that this slightly increases the amount of information sent out
to the local interface (up to three neighbour updates per received
packet, vs. up to two without this patch).

message.c

@@ -598,6 +598,7 @@ parse_packet(const unsigned char *from, struct interface *ifp,
     if(have_hello_rtt && hello_send_us && hello_rtt_receive_time) {
         int remote_waiting_us, local_waiting_us;
         int rtt;
+        int old_rttcost, changed = 0;
         remote_waiting_us = neigh->hello_send_us - hello_rtt_receive_time;
         local_waiting_us = time_us(neigh->hello_rtt_receive_time) -
             hello_send_us;
@@ -611,6 +612,7 @@ parse_packet(const unsigned char *from, struct interface *ifp,
         debugf("RTT to %s on %s sample result: %d us.\n",
                format_address(from), ifp->name, rtt);
 
+        old_rttcost = neighbour_rttcost(neigh);
         if (valid_rtt(neigh)) {
             /* Running exponential average. */
             neigh->rtt = (ifp->rtt_exponential_decay * MAX(rtt, 0)
@@ -621,6 +623,8 @@ parse_packet(const unsigned char *from, struct interface *ifp,
                (higher RTT) */
             neigh->rtt = MAX(2*rtt, 0);
         }
+        changed = (neighbour_rttcost(neigh) == old_rttcost ? 0 : 1);
+        update_neighbour_metric(neigh, changed);
         neigh->rtt_time = now;
     }
     return;