Force call of subscriber_callback when the ETX of a link is estimated…

… for the first time. Otherwise, it was not called in case of NO_ACK.

core/net/neighbor-info.c

@@ -61,12 +61,14 @@ update_metric(const rimeaddr_t *dest, int packet_metric)
   link_metric_t *metricp;
   link_metric_t recorded_metric, new_metric;
   unsigned long time;
+  int first_update = 0;
 
   metricp = (link_metric_t *)neighbor_attr_get_data(&attr_etx, dest);
   packet_metric = NEIGHBOR_INFO_ETX2FIX(packet_metric);
   if(metricp == NULL || *metricp == 0) {
     recorded_metric = NEIGHBOR_INFO_ETX2FIX(ETX_LIMIT);
     new_metric = packet_metric;
+    first_update = 1;
   } else {
     recorded_metric = *metricp;
     /* Update the EWMA of the ETX for the neighbor. */
@@ -84,7 +86,7 @@ update_metric(const rimeaddr_t *dest, int packet_metric)
     time = clock_seconds();
     neighbor_attr_set_data(&attr_etx, dest, &new_metric);
     neighbor_attr_set_data(&attr_timestamp, dest, &time);
-    if(new_metric != recorded_metric && subscriber_callback != NULL) {
+    if((first_update || new_metric != recorded_metric) && subscriber_callback != NULL) {
       subscriber_callback(dest, 1, new_metric);
     }
   }