RPL DAO timers and management:

* Added a DAO lifetime timer that sends out a new DAO after half the lifetime of the DAO. This allows implementing DAO route soft state that avoids routing tables in the network keeping stale routes for ever.
* Added ways to schedule a new DAO transmission as well as cancelling an active DAO transmit timer, which makes it possible to do nodes that don't send DAOs.

core/net/rpl/rpl-private.h

@@ -309,6 +309,9 @@ 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_cancel_dao(rpl_instance_t *instance);
+
 void rpl_reset_dio_timer(rpl_instance_t *);
 void rpl_reset_periodic_timer(void);
 

core/net/rpl/rpl-timers.c

@@ -194,6 +194,28 @@ rpl_reset_dio_timer(rpl_instance_t *instance)
 #endif /* RPL_LEAF_ONLY */
 }
 /*---------------------------------------------------------------------------*/
+static void handle_dao_timer(void *ptr);
+static void
+set_dao_lifetime_timer(rpl_instance_t *instance)
+{
+  if(rpl_get_mode() == RPL_MODE_FEATHER) {
+    return;
+  }
+
+  /* Set up another DAO within half the expiration time, if such a
+     time has been configured */
+  if(instance->lifetime_unit != 0xffff && instance->default_lifetime != 0xff) {
+    clock_time_t expiration_time;
+    expiration_time = (clock_time_t)instance->default_lifetime *
+      (clock_time_t)instance->lifetime_unit *
+      CLOCK_SECOND / 2;
+    PRINTF("RPL: Scheduling DAO lifetime timer %u ticks in the future\n",
+           (unsigned)expiration_time);
+    ctimer_set(&instance->dao_lifetime_timer, expiration_time,
+               handle_dao_timer, instance);
+  }
+}
+/*---------------------------------------------------------------------------*/
 static void
 handle_dao_timer(void *ptr)
 {
@@ -215,11 +237,16 @@ handle_dao_timer(void *ptr)
   } else {
     PRINTF("RPL: No suitable DAO parent\n");
   }
+
   ctimer_stop(&instance->dao_timer);
+
+  if(etimer_expired(&instance->dao_lifetime_timer.etimer)) {
+    set_dao_lifetime_timer(instance);
+  }
 }
 /*---------------------------------------------------------------------------*/
-void
-rpl_schedule_dao(rpl_instance_t *instance)
+static void
+schedule_dao(rpl_instance_t *instance, clock_time_t latency)
 {
   clock_time_t expiration_time;
 
@@ -228,13 +255,38 @@ rpl_schedule_dao(rpl_instance_t *instance)
   if(!etimer_expired(&instance->dao_timer.etimer)) {
     PRINTF("RPL: DAO timer already scheduled\n");
   } else {
-    expiration_time = RPL_DAO_LATENCY / 2 +
-      (random_rand() % (RPL_DAO_LATENCY));
+    if(latency != 0) {
+      expiration_time = latency / 2 +
+        (random_rand() % (latency));
+    } else {
+      expiration_time = 0;
+    }
     PRINTF("RPL: Scheduling DAO timer %u ticks in the future\n",
            (unsigned)expiration_time);
     ctimer_set(&instance->dao_timer, expiration_time,
                handle_dao_timer, instance);
+
+    set_dao_lifetime_timer(instance);
   }
 }
 /*---------------------------------------------------------------------------*/
+void
+rpl_schedule_dao(rpl_instance_t *instance)
+{
+  schedule_dao(instance, RPL_DAO_LATENCY);
+}
+/*---------------------------------------------------------------------------*/
+void
+rpl_schedule_dao_immediately(rpl_instance_t *instance)
+{
+  schedule_dao(instance, 0);
+}
+/*---------------------------------------------------------------------------*/
+void
+rpl_cancel_dao(rpl_instance_t *instance)
+{
+  ctimer_stop(&instance->dao_timer);
+  ctimer_stop(&instance->dao_lifetime_timer);
+}
+/*---------------------------------------------------------------------------*/
 #endif /* UIP_CONF_IPV6 */

core/net/rpl/rpl.h

@@ -225,6 +225,7 @@ struct rpl_instance {
   clock_time_t dio_next_delay; /* delay for completion of dio interval */
   struct ctimer dio_timer;
   struct ctimer dao_timer;
+  struct ctimer dao_lifetime_timer;
 };
 
 /*---------------------------------------------------------------------------*/