Enhanced RPL loop repair: send unicast DIO to source when detecting a loop from ext header, update rank along the path (when rank error is signaled)

core/net/rpl/rpl-ext-header.c

@@ -73,6 +73,7 @@ rpl_verify_header(int uip_ext_opt_offset)
   uint16_t sender_rank;
   uint8_t sender_closer;
   uip_ds6_route_t *route;
+  rpl_parent_t *sender = NULL;
 
   if(UIP_HBHO_BUF->len != RPL_HOP_BY_HOP_LEN - 8) {
     PRINTF("RPL: Hop-by-hop extension header has wrong size\n");
@@ -132,10 +133,25 @@ rpl_verify_header(int uip_ext_opt_offset)
 	 instance->current_dag->rank
 	 );
 
+  sender = nbr_table_get_from_lladdr(rpl_parents, packetbuf_addr(PACKETBUF_ADDR_SENDER));
+
+  if(UIP_EXT_HDR_OPT_RPL_BUF->flags & RPL_HDR_OPT_RANK_ERR) {
+    /* A rank error was signalled, attempt to repair it by updating
+     * the sender's rank from ext header */
+    sender->rank = sender_rank;
+    rpl_select_dag(instance, sender);
+  }
+
   if((down && !sender_closer) || (!down && sender_closer)) {
     PRINTF("RPL: Loop detected - senderrank: %d my-rank: %d sender_closer: %d\n",
 	   sender_rank, instance->current_dag->rank,
 	   sender_closer);
+    /* Attempt to repair the loop by sending a unicast DIO back to the sender
+     * so that it gets a fresh update of our rank. */
+    if(sender != NULL) {
+      instance->unicast_dio_target = sender;
+      rpl_schedule_unicast_dio_immediately(instance);
+    }
     if(UIP_EXT_HDR_OPT_RPL_BUF->flags & RPL_HDR_OPT_RANK_ERR) {
       RPL_STAT(rpl_stats.loop_errors++);
       PRINTF("RPL: Rank error signalled in RPL option!\n");

core/net/rpl/rpl-private.h

@@ -312,6 +312,7 @@ rpl_of_t *rpl_find_of(rpl_ocp_t);
 /* Timer functions. */
 void rpl_schedule_dao(rpl_instance_t *);
 void rpl_schedule_dao_immediately(rpl_instance_t *);
+void rpl_schedule_unicast_dio_immediately(rpl_instance_t *instance);
 void rpl_cancel_dao(rpl_instance_t *instance);
 void rpl_schedule_probing(rpl_instance_t *instance);
 

core/net/rpl/rpl-timers.c

@@ -327,6 +327,24 @@ rpl_cancel_dao(rpl_instance_t *instance)
   ctimer_stop(&instance->dao_lifetime_timer);
 }
 /*---------------------------------------------------------------------------*/
+static void
+handle_unicast_dio_timer(void *ptr)
+{
+  rpl_instance_t *instance = (rpl_instance_t *)ptr;
+  uip_ipaddr_t *target_ipaddr = rpl_get_parent_ipaddr(instance->unicast_dio_target);
+
+  if(target_ipaddr != NULL) {
+    dio_output(instance, target_ipaddr);
+  }
+}
+/*---------------------------------------------------------------------------*/
+void
+rpl_schedule_unicast_dio_immediately(rpl_instance_t *instance)
+{
+  ctimer_set(&instance->unicast_dio_timer, 0,
+                  handle_unicast_dio_timer, instance);
+}
+/*---------------------------------------------------------------------------*/
 #if RPL_WITH_PROBING
 static rpl_parent_t *
 get_probing_target(rpl_dag_t *dag)

core/net/rpl/rpl.h

@@ -230,6 +230,8 @@ struct rpl_instance {
   struct ctimer dio_timer;
   struct ctimer dao_timer;
   struct ctimer dao_lifetime_timer;
+  struct ctimer unicast_dio_timer;
+  rpl_parent_t *unicast_dio_target;
 };
 
 /*---------------------------------------------------------------------------*/