From e000b1abf32400e6530c7cf614ebc89a57767dc6 Mon Sep 17 00:00:00 2001
From: nvt-se <nvt-se>
Date: Mon, 14 Jun 2010 12:44:37 +0000
Subject: [PATCH] A major update to ContikiRPL resulting in a reduced code
 footprint by 300 bytes, as well as cleaner protocol logic.

* Made parent management uniform.

* Simplified the DIO processing.

* Improved the Objective Function API and its documentation.

* Removed redundant code at various places.

* Improved identifier naming.

* Switched visualization from candidate parents to preferred parents only.

* Made DAO ACK transmissions configurable.

* Improved initial ETX guess by using a cached local confidence value.

* Added a periodical rank recalculation function to reduce
  the maximum stack depth.

* Increased the Trickle redundancy constant to ensure faster
  topological updates.
---
 core/net/rpl/rpl-dag.c    | 388 +++++++++++++++++++-------------------
 core/net/rpl/rpl-icmp6.c  |  45 +++--
 core/net/rpl/rpl-of-etx.c |  62 ++++--
 core/net/rpl/rpl-of0.c    |  31 +--
 core/net/rpl/rpl-timers.c |  17 +-
 core/net/rpl/rpl.c        |  38 +---
 core/net/rpl/rpl.h        |  54 ++++--
 7 files changed, 335 insertions(+), 300 deletions(-)

diff --git a/core/net/rpl/rpl-dag.c b/core/net/rpl/rpl-dag.c
index e0bd305c9..ac69278d1 100644
--- a/core/net/rpl/rpl-dag.c
+++ b/core/net/rpl/rpl-dag.c
@@ -32,7 +32,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: rpl-dag.c,v 1.26 2010/06/14 11:35:21 adamdunkels Exp $
+ * $Id: rpl-dag.c,v 1.27 2010/06/14 12:44:37 nvt-se Exp $
  */
 /**
  * \file
@@ -45,15 +45,14 @@
 
 #include "net/uip.h"
 #include "net/uip-nd6.h"
-#include "sys/ctimer.h"
 #include "lib/list.h"
 #include "lib/memb.h"
+#include "sys/ctimer.h"
 
 #include <limits.h>
 #include <string.h>
 
 #define DEBUG DEBUG_ANNOTATE
-
 #include "net/uip-debug.h"
 
 /************************************************************************/
@@ -68,7 +67,7 @@ static rpl_of_t *objective_functions[] = {&rpl_of_etx, NULL};
 #endif /* !RPL_CONF_MAX_DAG_ENTRIES */
 
 #ifndef RPL_CONF_MAX_PARENTS
-#define RPL_MAX_PARENTS       4
+#define RPL_MAX_PARENTS       8
 #else
 #define RPL_MAX_PARENTS       RPL_CONF_MAX_PARENTS
 #endif /* !RPL_CONF_MAX_PARENTS */
@@ -97,31 +96,32 @@ static rpl_of_t *objective_functions[] = {&rpl_of_etx, NULL};
 MEMB(parent_memb, struct rpl_parent, RPL_MAX_PARENTS);
 
 static rpl_dag_t dag_table[RPL_MAX_DAG_ENTRIES];
-
-#define POISON_ROUTES 1
 /************************************************************************/
+/* Remove DAG parents with a rank that is at least the same as minimum_rank.
+ * If the argument poison_routes is non-null, the function also sends
+ * no-DAOs to these parents.
+ */
+#define POISON_ROUTES 1
+
 static void
-remove_parents(rpl_dag_t *dag, rpl_parent_t *exception, int poison_routes)
+remove_parents(rpl_dag_t *dag, rpl_rank_t minimum_rank, int poison_routes)
 {
   rpl_parent_t *p, *p2;
 
-  PRINTF("RPL: Removing parents %s poisoning routes\n",
-	 poison_routes == POISON_ROUTES ? "and" : "without");
+  PRINTF("RPL: Removing parents (minimum rank %u, poisoning routes %d\n",
+	minimum_rank, poison_routes);
 
-  for(p = list_head(dag->parents); p != NULL;) {
-   if(p != exception) {
-     if(poison_routes == POISON_ROUTES) {
-       /* Send no-DAOs to old parents. */
-       dao_output(p, ZERO_LIFETIME);
-     }
+  for(p = list_head(dag->parents); p != NULL; p = p2) {
+    p2 = p->next;
+    if(p->rank >= minimum_rank) {
+      if(poison_routes == POISON_ROUTES) {
+	/* Send no-DAOs to old parents. */
+	dao_output(p, ZERO_LIFETIME);
+      }
 
-     p2 = p->next;
-     rpl_remove_parent(dag, p);
-     p = p2;
-   } else {
-     p = p->next;
-   }
- }
+      rpl_remove_parent(dag, p);
+    }
+  }
 }
 /************************************************************************/
 static int
@@ -129,14 +129,13 @@ should_send_dao(rpl_dag_t *dag, rpl_dio_t *dio, rpl_parent_t *p)
 {
   return 1;
   return dio->dst_adv_supported && dio->dst_adv_trigger &&
-         dio->dtsn > p->dtsn && p == dag->best_parent;
+         dio->dtsn > p->dtsn && p == dag->preferred_parent;
 }
 /************************************************************************/
 static int
-acceptable_rank_increase(rpl_dag_t *dag, rpl_parent_t *p)
+acceptable_rank(rpl_dag_t *dag, rpl_rank_t rank)
 {
-  return !dag->max_rankinc || 
-    dag->of->increment_rank(p->rank, p) <= dag->min_rank + dag->max_rankinc;
+  return rank != INFINITE_RANK && rank <= dag->min_rank + dag->max_rankinc;
 }
 /************************************************************************/
 rpl_dag_t *
@@ -164,7 +163,7 @@ rpl_set_root(uip_ipaddr_t *dag_id)
   dag->grounded = RPL_GROUNDED;
   dag->rank = ROOT_RANK;
   dag->of = rpl_find_of(RPL_DEFAULT_OCP);
-  dag->best_parent = NULL;
+  dag->preferred_parent = NULL;
   dag->dtsn_out = 1; /* Trigger DAOs from the beginning. */
 
   memcpy(&dag->dag_id, dag_id, sizeof(dag->dag_id));
@@ -228,16 +227,19 @@ rpl_set_default_route(rpl_dag_t *dag, uip_ipaddr_t *from)
 rpl_dag_t *
 rpl_alloc_dag(uint8_t instance_id)
 {
-  int i;
+  rpl_dag_t *dag;
+  rpl_dag_t *end;
 
-  for(i = 0; i < RPL_MAX_DAG_ENTRIES; i++) {
-    if(dag_table[i].used == 0) {
-      memset(&dag_table[i], 0, sizeof(dag_table[0]));
-      dag_table[i].parents = &dag_table[i].parent_list;
-      list_init(dag_table[i].parents);
-      dag_table[i].instance_id = instance_id;
-      dag_table[i].def_route = NULL;
-      return &dag_table[i];
+  for(dag = &dag_table[0], end = dag + RPL_MAX_DAG_ENTRIES; dag < end; dag++) {
+    if(dag->used == 0) {
+      memset(dag, 0, sizeof(*dag));
+      dag->parents = &dag->parent_list;
+      list_init(dag->parents);
+      dag->instance_id = instance_id;
+      dag->def_route = NULL;
+      dag->rank = INFINITE_RANK;
+      dag->min_rank = INFINITE_RANK;
+      return dag;
     }
   }
   return NULL;
@@ -254,7 +256,7 @@ rpl_free_dag(rpl_dag_t *dag)
   rpl_remove_routes(dag);
 
   /* Remove parents and the default route. */
-  remove_parents(dag, NULL, !POISON_ROUTES);
+  remove_parents(dag, 0, !POISON_ROUTES);
   rpl_set_default_route(dag, NULL);
 
   ctimer_stop(&dag->dio_timer);
@@ -276,15 +278,12 @@ rpl_add_parent(rpl_dag_t *dag, rpl_dio_t *dio, uip_ipaddr_t *addr)
 
   memcpy(&p->addr, addr, sizeof(p->addr));
   p->dag = dag;
-  p->rank = dio->dag_rank;
+  p->rank = dio->rank;
   p->local_confidence = 0;
   p->dtsn = 0;
 
   list_add(dag->parents, p);
 
-  /* Draw a line between the node and its parent in Cooja. */
-  ANNOTATE("#L %u 1\n", addr->u8[sizeof(*addr) - 1]);
-
   return p;
 }
 /************************************************************************/
@@ -304,7 +303,7 @@ rpl_find_parent(rpl_dag_t *dag, uip_ipaddr_t *addr)
 
 /************************************************************************/
 rpl_parent_t *
-rpl_preferred_parent(rpl_dag_t *dag)
+rpl_select_parent(rpl_dag_t *dag)
 {
   rpl_parent_t *p;
   rpl_parent_t *best;
@@ -317,12 +316,32 @@ rpl_preferred_parent(rpl_dag_t *dag)
       best = dag->of->best_parent(best, p);
     }
   }
-  if(dag->best_parent != best) {
-    dag->best_parent = best; /* Cache the value. */
+
+  if(dag->preferred_parent != best) {
+
+    /* Visualize the change of the preferred parent in Cooja. */
+    ANNOTATE("#L %u 0\n",
+	     dag->preferred_parent->addr.u8[sizeof(best->addr) - 1]);
+    ANNOTATE("#L %u 1\n", best->addr.u8[sizeof(best->addr) - 1]);
+
+    dag->preferred_parent = best; /* Cache the value. */
     rpl_set_default_route(dag, &best->addr);
     /* The DAO parent set changed - schedule a DAO transmission. */
     rpl_schedule_dao(dag);
+    PRINTF("RPL: New preferred parent, rank changed from %u to %u\n",
+	   (unsigned)dag->rank, dag->of->calculate_rank(best, 0));
   }
+
+  /* Update the DAG rank, since link-layer information may have changed
+     the local confidence. */
+  dag->rank = dag->of->calculate_rank(best, 0);
+  if(best->rank < dag->min_rank) {
+    dag->min_rank = best->rank;
+  } else if(!acceptable_rank(dag, best->rank)) {
+    remove_parents(dag, 0, POISON_ROUTES);
+    return NULL;
+  }
+
   return best;
 }
 /************************************************************************/
@@ -331,9 +350,6 @@ rpl_remove_parent(rpl_dag_t *dag, rpl_parent_t *parent)
 {
   uip_ds6_defrt_t *defrt;
 
-  ANNOTATE("#L %u 0\n",
-           parent->addr.u8[sizeof(parent->addr) - 1]);
-
   /* Remove uIPv6 routes that have this parent as the next hop. **/
   uip_ds6_route_rm_by_nexthop(&parent->addr);
   defrt = uip_ds6_defrt_lookup(&parent->addr);
@@ -436,10 +452,11 @@ join_dag(uip_ipaddr_t *from, rpl_dio_t *dio)
   dag->preference = dio->preference;
   dag->grounded = dio->grounded;
   dag->instance_id = dio->instance_id;
-  dag->rank = dag->of->increment_rank(dio->dag_rank, p);
+  dag->rank = dag->of->calculate_rank(NULL, dio->rank);
   dag->min_rank = dag->rank; /* So far this is the lowest rank we know */
   dag->version = dio->version;
-  dag->best_parent = p;
+  dag->preferred_parent = p;
+  ANNOTATE("#L %u 1\n", p->addr.u8[sizeof(p->addr) - 1]);
 
   dag->dio_intdoubl = dio->dag_intdoubl;
   dag->dio_intmin = dio->dag_intmin;
@@ -473,7 +490,7 @@ global_repair(uip_ipaddr_t *from, rpl_dag_t *dag, rpl_dio_t *dio)
 {
   rpl_parent_t *p;
 
-  remove_parents(dag, NULL, !POISON_ROUTES);
+  remove_parents(dag, 0, !POISON_ROUTES);
   dag->version = dio->version;
   dag->dtsn_out = 1;
   dag->of->reset(dag);
@@ -482,7 +499,8 @@ global_repair(uip_ipaddr_t *from, rpl_dag_t *dag, rpl_dio_t *dio)
     dag->rank = INFINITE_RANK;
   } else {
     rpl_set_default_route(dag, from);
-    dag->rank = dag->of->increment_rank(dio->dag_rank, p);
+    dag->rank = dag->of->calculate_rank(NULL, dio->rank);
+    dag->min_rank = dag->rank;
     rpl_reset_dio_timer(dag, 1);
     if(should_send_dao(dag, dio, p)) {
       rpl_schedule_dao(dag);
@@ -506,18 +524,82 @@ rpl_repair_dag(rpl_dag_t *dag)
 }
 /************************************************************************/
 void
+rpl_recalculate_ranks(void)
+{
+  rpl_dag_t *dag;
+  rpl_parent_t *p;
+
+  /*
+   * We recalculate ranks when we receive feedback from the system rather
+   * than RPL protocol messages. This periodical recalculation is called
+   * from a timer in order to keep the stack depth reasonably low.
+   */
+  dag = rpl_get_dag(RPL_ANY_INSTANCE);
+  if(dag != NULL) {
+    for(p = list_head(dag->parents); p != NULL; p = p->next) {
+      if(p->updated) {
+	p->updated = 0;
+	rpl_process_parent_event(dag, p);
+	/*
+	 * Stop calculating here because the parent list may have changed.
+	 * If more ranks need to be recalculated, it will be taken care of
+	 * in subsequent calls to this functions.
+	 */
+	break;
+      }
+    }
+  }
+}
+/************************************************************************/
+int
+rpl_process_parent_event(rpl_dag_t *dag, rpl_parent_t *p)
+{
+  rpl_rank_t parent_rank;
+  rpl_rank_t old_rank;
+
+  /* Update the parent rank. */
+  parent_rank = p->rank;
+  old_rank = dag->rank;
+
+  if(rpl_select_parent(dag) == NULL) {
+    /* No suitable parent; trigger a local repair. */
+    PRINTF("RPL: No more parents, triggering a local repair\n");
+    dag->rank = INFINITE_RANK;
+    rpl_reset_dio_timer(dag, 1);
+    return 1;
+  }
+
+  if(old_rank != dag->rank) {
+    if(dag->rank < dag->min_rank) {
+      dag->min_rank = dag->rank;
+    }
+    PRINTF("RPL: Moving in the DAG from rank %hu to %hu\n",
+	   old_rank, dag->rank);
+    PRINTF("RPL: The new preferred parent is ");
+    PRINT6ADDR(&dag->preferred_parent->addr);
+    PRINTF(" (rank %u)\n", (unsigned)(dag->preferred_parent->rank));
+    rpl_reset_dio_timer(dag, 1);
+  }
+
+  if(!acceptable_rank(dag, dag->of->calculate_rank(NULL, parent_rank))) {
+    /* The candidate parent is no longer valid: the rank increase resulting
+       from the choice of it as a parent would be too high. */
+    return 0;
+  }
+
+  return 1;
+}
+/************************************************************************/
+void
 rpl_process_dio(uip_ipaddr_t *from, rpl_dio_t *dio)
 {
   rpl_dag_t *dag;
   rpl_parent_t *p;
-  rpl_parent_t *preferred_parent;
-  rpl_rank_t new_rank;
-  uint8_t new_parent;
 
   dag = rpl_get_dag(dio->instance_id);
   if(dag == NULL) {
-    /* Always join the first possible DAG that is not of INF_RANK. */
-    if(dio->dag_rank != INFINITE_RANK) {
+    /* Join the first possible DAG of this RPL instance. */
+    if(dio->rank != INFINITE_RANK) {
       join_dag(from, dio);
     } else {
       PRINTF("RPL: Ignoring DIO from node with infinite rank: ");
@@ -527,12 +609,6 @@ rpl_process_dio(uip_ipaddr_t *from, rpl_dio_t *dio)
     return;
   }
 
-  if(dag->instance_id != dio->instance_id) {
-    /* We avoid joining more than one RPL instance. */
-    PRINTF("RPL: Cannot join another RPL instance\n");
-    return;
-  }
-
   if(memcmp(&dag->dag_id, &dio->dag_id, sizeof(dag->dag_id))) {
     PRINTF("RPL: Ignoring DIO for another DAG within our instance\n");
     return;
@@ -554,107 +630,57 @@ rpl_process_dio(uip_ipaddr_t *from, rpl_dio_t *dio)
     return;
   }
 
-  /* This DIO pertains to a DAG that we are already part of. */
+  if(dag->rank == ROOT_RANK) {
+    return;
+  }
+
+  if(dio->rank == INFINITE_RANK) {
+    rpl_reset_dio_timer(dag, 1);
+    return;
+  }
+
+  /* At this point, we know that this DIO pertains to a DAG that
+     we are already part of. */
+
   p = rpl_find_parent(dag, from);
-  if(p != NULL) {
-    if(should_send_dao(dag, dio, p)) {
-      rpl_schedule_dao(dag);
+  if(p == NULL) {
+    if(RPL_PARENT_COUNT(dag) == RPL_MAX_PARENTS && dio->rank >= dag->rank) {
+      /* Try to make room for a new parent. */
+      remove_parents(dag, dio->rank, !POISON_ROUTES);
     }
-    p->dtsn = dio->dtsn;
 
-    if(p->rank > dio->dag_rank) {
-      p->rank = dio->dag_rank;
-      rpl_reset_dio_timer(dag, 1);
-    } else if(p->rank < dio->dag_rank) {
-      PRINTF("RPL: Existing parent ");
-      PRINT6ADDR(from);
-      PRINTF(" got a higher rank (%hu -> %hu)\n",
-             p->rank, dio->dag_rank);
-      p->rank = dio->dag_rank;
-      if(RPL_PARENT_COUNT(dag) > 1) {
-        /* Since we have alternative parents, we can simply drop this one. */
-        rpl_remove_parent(dag, p);
-	p = rpl_preferred_parent(dag);
-	if(p != NULL) {
-          rpl_set_default_route(dag, &p->addr);
-	}
-	return;
-      } else if(dag->of->increment_rank(dio->dag_rank, p) <= dag->min_rank + dag->max_rankinc) {
-        preferred_parent = rpl_preferred_parent(dag);
-        if(p == preferred_parent) {
-          new_rank = dag->of->increment_rank(dio->dag_rank, p);
-          rpl_set_default_route(dag, &p->addr);
-	  dag->rank = new_rank;
-	  PRINTF("RPL: New rank is %hu, max is %hu\n",
-		dag->rank, dag->min_rank + dag->max_rankinc);
-        }
-      } else {
-        PRINTF("RPL: Cannot find an acceptable preferred parent\n");
-        /* do local repair - jump down the DAG */
-        remove_parents(dag, NULL, POISON_ROUTES);
-        dag->rank = INFINITE_RANK;
-      }
-      rpl_reset_dio_timer(dag, 1);
-    } else {
-      /* Assume consistency and increase the DIO counter. */
-      PRINTF("RPL: Received a consistent DIO\n");
-      dag->dio_counter++;
-    }
-  }
-
-  if(dio->dag_rank < dag->rank) {
-    /* Message from a node closer to the root, but we might still be out of allowed rank-range */
-    if(dag->max_rankinc > 0 && dag->min_rank + dag->max_rankinc <
-       dag->of->increment_rank(dio->dag_rank, NULL)) {
-        PRINTF("RPL: Could not add parent, resulting rank too high\n");
-        return;
-    }
-    new_parent = 0;
+    /* Add the DIO sender as a candidate parent. */
+    p = rpl_add_parent(dag, dio, from);
     if(p == NULL) {
-      p = rpl_add_parent(dag, dio, from);
-      if(p == NULL) {
-        PRINTF("RPL: Could not add parent\n");
-        return;
-      }
-
-      PRINTF("RPL: New parent with rank %hu: ", p->rank);
+      PRINTF("RPL: Failed to add a new parent (");
       PRINT6ADDR(from);
-      PRINTF("\n");
-      new_parent = 1;
+      PRINTF(")\n");
+      return;
     }
 
-    new_rank = dag->of->increment_rank(dio->dag_rank, p);
-    if(new_rank < dag->rank) {
-      PRINTF("RPL: Moving up within the DAG from rank %hu to %hu\n",
-             dag->rank, new_rank);
-      dag->rank = new_rank;
-      dag->min_rank = new_rank; /* So far this is the lowest rank we know */
-      rpl_reset_dio_timer(dag, 1);
-
-      /* Remove old def-route and add the new */
-      /* fix handling of destination prefix   */
-      rpl_set_default_route(dag, from);
-
-      if(new_parent) {
-        remove_parents(dag, p, POISON_ROUTES);
-      }
-    }
-  } else if(dio->dag_rank == dag->rank) {
-    /* Message from a sibling. */
-  } else {
-    /* Message from a node at a longer distance from the root. If the
-       node is in the parent list, we just remove it. */
-    if(p != NULL && p->rank < dio->dag_rank) {
-      PRINTF("RPL: Parent ");
-      PRINT6ADDR(&p->addr);
-      PRINTF(" has increased in rank from %hu to %hu. Removing it.\n",
-             p->rank, dio->dag_rank);
-      rpl_remove_parent(dag, p);
-      if(RPL_PARENT_COUNT(dag) == 0) {
-        dag->rank = INFINITE_RANK;
-      }
-    }
+    PRINTF("RPL: New candidate parent with rank %u: ", (unsigned)p->rank);
+    PRINT6ADDR(from);
+    PRINTF("\n");
   }
+
+  /* We have an allocated candidate parent, process the DIO further. */
+
+  if(p->rank != dio->rank) {
+    p->rank = dio->rank;
+    if(rpl_process_parent_event(dag, p) == 0) {
+      /* The candidate parent no longer exists. */
+      return;
+    }
+    printf("X1.2\n");
+  } else {
+    PRINTF("RPL: Received consistent DIO\n");
+    dag->dio_counter++;
+  }
+
+  if(should_send_dao(dag, dio, p)) {
+    rpl_schedule_dao(dag);
+  }
+  p->dtsn = dio->dtsn;
 }
 /************************************************************************/
 void
@@ -662,51 +688,17 @@ rpl_ds6_neighbor_callback(uip_ds6_nbr_t *nbr)
 {
   rpl_dag_t *dag;
   rpl_parent_t *p;
-  rpl_parent_t *new_p;
-
-  if(nbr->isused) {
-    PRINTF("RPL: Neighbor state %u: ", nbr->state);
-    PRINT6ADDR(&nbr->ipaddr);
-    PRINTF("\n");
-    return;
-  }
-
-  PRINTF("RPL: Removing neighbor ");
-  PRINT6ADDR(&nbr->ipaddr);
-  PRINTF("\n");
 
   dag = rpl_get_dag(RPL_ANY_INSTANCE);
-  if(dag == NULL) {
-    return;
-  }
-
-  p = rpl_find_parent(dag, &nbr->ipaddr);
-  if(p != NULL) {
-    if(p == dag->best_parent) {
-      /* Try to select a new preferred parent. */
-      new_p = rpl_preferred_parent(dag);
-      if(new_p == NULL) {
-        rpl_free_dag(dag);
-        return;
-      }
-
-      if(acceptable_rank_increase(dag, new_p)) {
-        dag->rank = dag->of->increment_rank(new_p->rank, new_p);
-        if(dag->rank < dag->min_rank) {
-          dag->min_rank = dag->rank;
-        }
-        PRINTF("RPL: New rank is %hu, max is %hu\n",
-		dag->rank, dag->min_rank + dag->max_rankinc);
-        rpl_set_default_route(dag, &new_p->addr);
-      } else {
-        PRINTF("RPL: Cannot select the preferred parent\n");
-        /* do local repair - jump down the DAG */
-        rpl_set_default_route(dag, NULL);
-        remove_parents(dag, NULL, POISON_ROUTES);
-        dag->rank = INFINITE_RANK;
-        rpl_reset_dio_timer(dag, 1);
-      }
+  if(!nbr->isused && dag) {
+    PRINTF("RPL: Removing neighbor ");
+    PRINT6ADDR(&nbr->ipaddr);
+    PRINTF("\n");
+    p = rpl_find_parent(dag, &nbr->ipaddr);
+    if(p != NULL) {
+      p->rank = INFINITE_RANK;
+      /* Trigger DAG rank recalculation. */
+      p->updated = 1;
     }
-    rpl_remove_parent(dag, p);
   }
 }
diff --git a/core/net/rpl/rpl-icmp6.c b/core/net/rpl/rpl-icmp6.c
index 9f75e0e29..53c3a261c 100644
--- a/core/net/rpl/rpl-icmp6.c
+++ b/core/net/rpl/rpl-icmp6.c
@@ -33,7 +33,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: rpl-icmp6.c,v 1.20 2010/06/12 10:55:46 joxe Exp $
+ * $Id: rpl-icmp6.c,v 1.21 2010/06/14 12:44:37 nvt-se Exp $
  */
 /**
  * \file
@@ -203,7 +203,6 @@ dio_input(void)
     PRINTF("RPL: Neighbor already in neighbor cache\n");
   }
 
-
   buffer_length = uip_len - uip_l2_l3_icmp_hdr_len;
 
   /* Process the DIO base option. */
@@ -212,9 +211,11 @@ dio_input(void)
 
   dio.instance_id = buffer[i++];
   dio.version = buffer[i++];
-  dio.dag_rank = (buffer[i] << 8) + buffer[i + 1];
+  dio.rank = (buffer[i] << 8) + buffer[i + 1];
   i += 2;
 
+  PRINTF("RPL: Incoming DIO rank %u\n", (unsigned)dio.rank);
+
   dio.grounded = buffer[i] & RPL_DIO_GROUNDED;
   dio.dst_adv_trigger = buffer[i] & RPL_DIO_DEST_ADV_TRIGGER;
   dio.dst_adv_supported = buffer[i] & RPL_DIO_DEST_ADV_SUPPORTED;
@@ -304,7 +305,6 @@ dio_output(rpl_dag_t *dag, uip_ipaddr_t *uc_addr)
   uip_ipaddr_t addr;
 
   /* DAG Information Solicitation */
-  PRINTF("RPL: Sending a DIO with rank: %u\n", (unsigned)dag->rank);
   pos = 0;
 
   buffer = UIP_ICMP_PAYLOAD;
@@ -354,13 +354,13 @@ dio_output(rpl_dag_t *dag, uip_ipaddr_t *uc_addr)
     pos += 4;
     memset(&buffer[pos], 0, 4);
     pos += 4;
-    memcpy(&buffer[pos], &(dag->prefix_info.prefix), 16);
+    memcpy(&buffer[pos], &dag->prefix_info.prefix, 16);
     pos += 16;
-    PRINTF("RPL: Sending prefix info in DIO ");
+    PRINTF("RPL: Sending prefix info in DIO for ");
     PRINT6ADDR(&dag->prefix_info.prefix);
     PRINTF("\n");
   } else {
-    PRINTF("RPL: No prefix to announce. len:%d\n",
+    PRINTF("RPL: No prefix to announce (len %d)\n",
            dag->prefix_info.length);
   }
 
@@ -395,7 +395,6 @@ dao_input(void)
   uint8_t subopt_type;
   uip_ipaddr_t prefix;
   uip_ds6_route_t *rep;
-  rpl_parent_t *n;
   uint8_t buffer_length;
   int pos;
   int len;
@@ -417,6 +416,14 @@ dao_input(void)
 
   pos = 0;
   instance_id = buffer[pos++];
+
+  dag = rpl_get_dag(instance_id);
+  if(dag == NULL) {
+    PRINTF("RPL: Ignoring a DAO for a different RPL instance (%u)\n",
+           instance_id);
+    return;
+  }
+
   flags = buffer[pos++];
   /* reserved */
   pos++;
@@ -429,14 +436,6 @@ dao_input(void)
     pos += 16;
   }
 
-  /* handle the target option */
-  dag = rpl_get_dag(instance_id);
-  if(dag == NULL) {
-    PRINTF("RPL: Ignoring a DAO for a different RPL instance (%u)\n",
-           instance_id);
-    return;
-  }
-
   /* Check if there are any DIO suboptions. */
   i = pos;
   for(; i < buffer_length; i += len) {
@@ -450,6 +449,7 @@ dao_input(void)
 
     switch(subopt_type) {
     case RPL_DIO_SUBOPT_TARGET:
+      /* handle the target option */
       prefixlen = buffer[i + 3];
       memset(&prefix, 0, sizeof(prefix));
       memcpy(&prefix, buffer + i + 4, (prefixlen + 7) / CHAR_BIT);
@@ -493,11 +493,12 @@ dao_input(void)
   }
 
   if(learned_from == RPL_ROUTE_FROM_UNICAST_DAO) {
-    if((n = rpl_preferred_parent(dag)) != NULL) {
+    if(dag->preferred_parent) {
       PRINTF("RPL: Forwarding DAO to parent ");
-      PRINT6ADDR(&n->addr);
+      PRINT6ADDR(&dag->preferred_parent->addr);
       PRINTF("\n");
-      uip_icmp6_send(&n->addr, ICMP6_RPL, RPL_CODE_DAO, buffer_length);
+      uip_icmp6_send(&dag->preferred_parent->addr,
+	ICMP6_RPL, RPL_CODE_DAO, buffer_length);
     } else if(flags & RPL_DAO_K_FLAG) {
       dao_ack_output(dag, &dao_sender_addr, sequence);
     }
@@ -536,7 +537,11 @@ dao_output(rpl_parent_t *n, uint32_t lifetime)
   pos = 0;
 
   buffer[pos++] = dag->instance_id;
-  buffer[pos++] = RPL_DAO_K_FLAG; /* no ack request, no DODAGID */
+#if RPL_CONF_DAO_ACK
+  buffer[pos++] = RPL_DAO_K_FLAG; /* DAO ACK request, no DODAGID */
+#else
+  buffer[pos++] = 0; /* No DAO ACK request, no DODAGID */
+#endif
   buffer[pos++] = 0; /* reserved */
   buffer[pos++] = dao_sequence & 0xff;
 
diff --git a/core/net/rpl/rpl-of-etx.c b/core/net/rpl/rpl-of-etx.c
index 054e29a61..139d6532b 100644
--- a/core/net/rpl/rpl-of-etx.c
+++ b/core/net/rpl/rpl-of-etx.c
@@ -32,7 +32,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: rpl-of-etx.c,v 1.4 2010/06/03 12:12:20 nvt-se Exp $
+ * $Id: rpl-of-etx.c,v 1.5 2010/06/14 12:44:37 nvt-se Exp $
  */
 /**
  * \file
@@ -49,18 +49,19 @@
 static void reset(void *);
 static void parent_state_callback(rpl_parent_t *, int, int);
 static rpl_parent_t *best_parent(rpl_parent_t *, rpl_parent_t *);
-static rpl_rank_t increment_rank(rpl_rank_t, rpl_parent_t *);
+static rpl_rank_t calculate_rank(rpl_parent_t *, rpl_rank_t);
 
 rpl_of_t rpl_of_etx = {
   reset,
   parent_state_callback,
   best_parent,
-  increment_rank,
+  calculate_rank,
   1
 };
 
 #define LINK_ETX_MIN			1
 #define LINK_ETX_MAX			10
+#define LINK_ETX_GUESS			(LINK_ETX_MAX - 1)
 #define PATH_ETX_MIN			1
 #define PATH_ETX_MAX			200
 #define PARENT_SWITCH_ETX_THRESHOLD	0.5
@@ -82,13 +83,7 @@ parent_state_callback(rpl_parent_t *parent, int known, int etx)
 
   dag = (rpl_dag_t *)parent->dag;
 
-  if(known) {
-    if(min_path_etx != INFINITE_RANK) {
-      dag->rank = min_path_etx + etx;
-      PRINTF("RPL: New path ETX: %u  min_path_etx=%u etx=%u\n",
-             (unsigned)(min_path_etx + etx), min_path_etx, etx);
-    }
-  } else {
+  if(!known) {
     if(RPL_PARENT_COUNT(dag) == 1) {
       /* Our last parent has disappeared, set the path ETX to INFINITE_RANK. */
       min_path_etx = INFINITE_RANK;
@@ -97,24 +92,38 @@ parent_state_callback(rpl_parent_t *parent, int known, int etx)
 }
 
 static rpl_rank_t
-increment_rank(rpl_rank_t rank, rpl_parent_t *parent)
+calculate_rank(rpl_parent_t *p, rpl_rank_t base_rank)
 {
+  rpl_dag_t *dag;
   rpl_rank_t new_rank;
+  rpl_rank_t rank_increase;
 
-  PRINTF("RPL: OF1 increment rank\n");
+  PRINTF("RPL: OF1 calculate rank\n");
 
-  if(parent != NULL && parent->rank < min_path_etx) {
-    min_path_etx = parent->rank;
-    PRINTF("RPL: min_path_etx updated to:%u\n", min_path_etx);
+  dag = (rpl_dag_t *)p->dag;
+
+  rank_increase = p == NULL ? LINK_ETX_GUESS : p->local_confidence;
+  rank_increase += dag->min_hoprankinc;
+
+  if(base_rank == 0) {
+    if(p == NULL) {
+      return INFINITE_RANK;
+    }
+    base_rank = p->rank;
   }
 
-  if(INFINITE_RANK - rank < LINK_ETX_MAX) {
+  if(base_rank < min_path_etx) {
+    min_path_etx = base_rank;
+    PRINTF("RPL: min_path_etx updated to %u\n", min_path_etx);
+  }
+
+  if(INFINITE_RANK - base_rank < rank_increase) {
     /* Reached the maximum rank. */
     new_rank = INFINITE_RANK;
   } else {
    /* Calculate the rank based on the new rank information from DIO or
       stored otherwise. */
-    new_rank = rank + LINK_ETX_MAX;
+    new_rank = base_rank + rank_increase;
   }
 
   PRINTF("RPL: Path ETX %u\n", (unsigned)new_rank);
@@ -125,7 +134,24 @@ increment_rank(rpl_rank_t rank, rpl_parent_t *parent)
 static rpl_parent_t *
 best_parent(rpl_parent_t *p1, rpl_parent_t *p2)
 {
-  if(p1->rank < p2->rank) {
+  rpl_dag_t *dag;
+  rpl_rank_t p1_rank;
+  rpl_rank_t p2_rank;
+
+  p1_rank = calculate_rank(p1, 0);
+  p2_rank = calculate_rank(p2, 0);
+
+  /* Maintain stability of the preferred parent in case of similar ranks. */
+  if(p1_rank == p2_rank) {
+    dag = (rpl_dag_t *)p1->dag;
+    if(p1 == dag->preferred_parent) {
+      return p1;
+    } else if(p2 == dag->preferred_parent) {
+      return p2;
+    }
+  }
+
+  if(p1_rank < p2_rank) {
     return p1;
   }
 
diff --git a/core/net/rpl/rpl-of0.c b/core/net/rpl/rpl-of0.c
index 0cf795d14..e490d9d4d 100644
--- a/core/net/rpl/rpl-of0.c
+++ b/core/net/rpl/rpl-of0.c
@@ -32,7 +32,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: rpl-of0.c,v 1.4 2010/05/31 14:22:00 nvt-se Exp $
+ * $Id: rpl-of0.c,v 1.5 2010/06/14 12:44:37 nvt-se Exp $
  */
 /**
  * \file
@@ -48,13 +48,13 @@
 
 static void reset(void *);
 static rpl_parent_t *best_parent(rpl_parent_t *, rpl_parent_t *);
-static rpl_rank_t increment_rank(rpl_rank_t, rpl_parent_t *);
+static rpl_rank_t calculate_rank(rpl_parent_t *, rpl_rank_t);
 
 rpl_of_t rpl_of0 = {
   reset,
   NULL,
   best_parent,
-  increment_rank,
+  calculate_rank,
   0
 };
 
@@ -70,14 +70,21 @@ reset(void *dag)
 }
 
 static rpl_rank_t
-increment_rank(rpl_rank_t rank, rpl_parent_t *parent)
+calculate_rank(rpl_parent_t *p, rpl_rank_t base_rank)
 {
-  if((rpl_rank_t)(rank + DEFAULT_RANK_INCREMENT) < rank) {
+  if(base_rank == 0) {
+    if(p == NULL) {
+      return INFINITE_RANK;
+    }
+    base_rank = p->rank;
+  }
+
+  if((rpl_rank_t)(base_rank + DEFAULT_RANK_INCREMENT) < base_rank) {
     PRINTF("RPL: OF0 rank %d incremented to infinite rank due to wrapping\n",
-        rank);
+        base_rank);
     return INFINITE_RANK;
   }
-  return rank + DEFAULT_RANK_INCREMENT;
+  return base_rank + DEFAULT_RANK_INCREMENT;
 }
 
 static rpl_parent_t *
@@ -91,15 +98,17 @@ best_parent(rpl_parent_t *p1, rpl_parent_t *p2)
   PRINTF(" (confidence %d, rank %d)\n",
         p2->local_confidence, p2->rank);
 
+  if(p1->rank < p2->rank) {
+    return p1;
+  } else if(p2->rank < p1->rank) {
+    return p2;
+  }
+
   if(p1->local_confidence > p2->local_confidence) {
     return p1;
   } else if(p2->local_confidence > p1->local_confidence) {
     return p2;
   }
 
-  if(p1->rank < p2->rank) {
-    return p1;
-  }
-
   return p2;
 }
diff --git a/core/net/rpl/rpl-timers.c b/core/net/rpl/rpl-timers.c
index 1302cb441..bc7ed1527 100644
--- a/core/net/rpl/rpl-timers.c
+++ b/core/net/rpl/rpl-timers.c
@@ -32,7 +32,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: rpl-timers.c,v 1.9 2010/06/14 11:35:21 adamdunkels Exp $
+ * $Id: rpl-timers.c,v 1.10 2010/06/14 12:44:37 nvt-se Exp $
  */
 /**
  * \file
@@ -42,9 +42,9 @@
  */
 
 #include "contiki-conf.h"
-#include "sys/ctimer.h"
 #include "net/rpl/rpl.h"
 #include "lib/random.h"
+#include "sys/ctimer.h"
 
 #define DEBUG DEBUG_ANNOTATE
 #include "net/uip-debug.h"
@@ -66,6 +66,7 @@ static void
 handle_periodic_timer(void *ptr)
 {
   rpl_purge_routes();
+  rpl_recalculate_ranks();
 
   /* handle DIS */
 #ifdef RPL_DIS_SEND
@@ -84,7 +85,7 @@ new_dio_interval(rpl_dag_t *dag)
   unsigned long time;
 
   /* TODO: too small timer intervals for many cases */
-  time = 1L << dag->dio_intcurrent;
+  time = 1UL << dag->dio_intcurrent;
 
   /* need to convert from milliseconds to CLOCK_TICKS */
   time = (time * CLOCK_SECOND) / 1000;
@@ -128,7 +129,7 @@ handle_dio_timer(void *ptr)
     if(uip_ds6_get_link_local(ADDR_PREFERRED) != NULL) {
       dio_send_ok = 1;
     } else {
-      PRINTF("RPL: Postponing DIO transmission since link local addres is not ok\n");
+      PRINTF("RPL: Postponing DIO transmission since link local address is not ok\n");
       ctimer_set(&dag->dio_timer, CLOCK_SECOND, &handle_dio_timer, dag);
       return;
     }
@@ -166,7 +167,7 @@ rpl_reset_periodic_timer(void)
   ctimer_set(&periodic_timer, CLOCK_SECOND, handle_periodic_timer, NULL);
 }
 /************************************************************************/
-/* Resets the DIO timer in the DAG and starts-up the interval */
+/* Resets the DIO timer in the DAG to its minimal interval. */
 void
 rpl_reset_dio_timer(rpl_dag_t *dag, uint8_t force)
 {
@@ -182,7 +183,6 @@ static void
 handle_dao_timer(void *ptr)
 {
   rpl_dag_t *dag;
-  rpl_parent_t *n;
 
   dag = (rpl_dag_t *)ptr;
 
@@ -194,10 +194,9 @@ handle_dao_timer(void *ptr)
 
   /* Send the DAO to the best parent. rpl-07 section C.2 lists the
      fan-out as being under investigation. */
-  n = rpl_preferred_parent(dag);
-  if(n != NULL) {
+  if(dag->preferred_parent != NULL) {
     PRINTF("RPL: handle_dao_timer - sending DAO\n");
-    dao_output(n, DEFAULT_ROUTE_LIFETIME);
+    dao_output(dag->preferred_parent, DEFAULT_ROUTE_LIFETIME);
   } else {
     PRINTF("RPL: Could not find a parent to send a DAO to \n");
   }
diff --git a/core/net/rpl/rpl.c b/core/net/rpl/rpl.c
index 35f63addb..04042f925 100644
--- a/core/net/rpl/rpl.c
+++ b/core/net/rpl/rpl.c
@@ -32,7 +32,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: rpl.c,v 1.6 2010/06/03 15:20:56 nvt-se Exp $
+ * $Id: rpl.c,v 1.7 2010/06/14 12:44:37 nvt-se Exp $
  */
 /**
  * \file
@@ -53,12 +53,6 @@
 #include <limits.h>
 
 /************************************************************************/
-#ifndef RPL_CONF_MAX_ROUTE_ENTRIES
-#define RPL_MAX_ROUTE_ENTRIES   10
-#else
-#define RPL_MAX_ROUTE_ENTRIES   RPL_CONF_MAX_ROUTE_ENTRIES
-#endif /* !RPL_CONF_MAX_ROUTE_ENTRIES */
-
 extern uip_ds6_route_t uip_ds6_routing_table[UIP_DS6_ROUTE_NB];
 /************************************************************************/
 void
@@ -151,6 +145,12 @@ neighbor_callback(const rimeaddr_t *addr, int known, int etx)
     return;
   }
 
+  if(etx != parent->local_confidence) {
+    /* Trigger DAG rank recalculation. */
+    parent->updated = 1;
+  }
+  parent->local_confidence = etx;
+
   if(dag->of->parent_state_callback != NULL) {
     dag->of->parent_state_callback(parent, known, etx);
   }
@@ -159,28 +159,8 @@ neighbor_callback(const rimeaddr_t *addr, int known, int etx)
     PRINTF("RPL: Removing parent ");
     PRINT6ADDR(&parent->addr);
     PRINTF(" because of bad connectivity (ETX %d)\n", etx);
-    rpl_remove_parent(dag, parent);
-    if(RPL_PARENT_COUNT(dag) == 0) {
-      rpl_free_dag(dag);
-    } else {
-      /* Select a new default route. */
-      parent = rpl_preferred_parent(dag);
-      if(parent != NULL) {
-	PRINTF("RPL: Switching preferred parent to ");
-        PRINT6ADDR(&parent->addr);
-        PRINTF("\n");
-        rpl_set_default_route(dag, &parent->addr);
-      }
-    }
-  } else {
-    parent->local_confidence = ~0 - etx;
-    PRINTF("RPL: Updating the local confidence value for this parent to %d\n",
-           parent->local_confidence);
-    if(parent != dag->best_parent &&
-       dag->of->best_parent(parent, dag->best_parent) == parent) {
-      dag->best_parent = parent;
-      rpl_set_default_route(dag, &parent->addr);
-    }
+    parent->rank = INFINITE_RANK;
+    parent->updated = 1;
   }
 }
 /************************************************************************/
diff --git a/core/net/rpl/rpl.h b/core/net/rpl/rpl.h
index dd9d63981..895432768 100644
--- a/core/net/rpl/rpl.h
+++ b/core/net/rpl/rpl.h
@@ -30,7 +30,7 @@
  *
  * Author: Joakim Eriksson, Nicolas Tsiftes
  *
- * $Id: rpl.h,v 1.18 2010/06/14 11:33:58 adamdunkels Exp $
+ * $Id: rpl.h,v 1.19 2010/06/14 12:44:37 nvt-se Exp $
  */
 
 #ifndef RPL_H
@@ -110,7 +110,7 @@
 #define RPL_DEFAULT_OCP                 1
 
 /* TODO: pick these from OCP later? */
-#define DEFAULT_MAX_RANKINC             16
+#define DEFAULT_MAX_RANKINC             10
 #define DEFAULT_MIN_HOPRANKINC          4
 
 /* Represents 2^n ms. */
@@ -120,7 +120,7 @@
 #define DEFAULT_DIO_INTERVAL_DOUBLINGS  8
 
 /* Desired DIO redundancy. */
-#define DEFAULT_DIO_REDUNDANCY          1
+#define DEFAULT_DIO_REDUNDANCY          5
 
 /* Expire DAOs from neighbors that do not respond in this time. (seconds) */
 #define DAO_EXPIRATION_TIMEOUT          60
@@ -158,25 +158,47 @@ struct rpl_parent {
   rpl_rank_t rank;
   uint8_t local_confidence;
   uint8_t dtsn;
+  uint8_t updated;
 };
 
 typedef struct rpl_parent rpl_parent_t;
 
+/*---------------------------------------------------------------------------*/
+/*
+ * API for RPL objective functions (OF)
+ *
+ * reset(dag)
+ *
+ *  Resets the objective function state for a specific DAG. This function is
+ *  called when doing a global repair on the DAG.
+ *
+ * parent_state_callback(parent, known, etx)
+ *
+ *  Receives link-layer neighbor information. The parameter "known" is set
+ *  either to 0 or 1. The "etx" parameter specifies the current
+ *  ETX(estimated transmissions) for the neighbor.
+ *
+ * best_parent(parent1, parent2)
+ *
+ *  Compares two parents and returns the best one, according to the OF.
+ *
+ * calculate_rank(parent, base_rank)
+ *
+ *  Calculates a rank value using the parent rank and a base rank.
+ *  If "parent" is NULL, the objective function selects a default increment
+ *  that is adds to the "base_rank". Otherwise, the OF uses information known
+ *  about "parent" to select an increment to the "base_rank".
+ */
 struct rpl_of {
   void (*reset)(void *);
   void (*parent_state_callback)(rpl_parent_t *, int, int);
   rpl_parent_t *(*best_parent)(rpl_parent_t *, rpl_parent_t *);
-
-  /* Increment the rank - the rank that just have been received in a DIO
-     (or if picked from a parent) is the first argument. This is considered
-     the valid rank to calculate based on. The second argument is the parent
-     that is related to this calculation - if any (can be NULL) */
-  rpl_rank_t (*increment_rank)(rpl_rank_t rank, rpl_parent_t *parent);
+  rpl_rank_t (*calculate_rank)(rpl_parent_t *, rpl_rank_t);
   rpl_ocp_t ocp;
 };
 
-
 typedef struct rpl_of rpl_of_t;
+/*---------------------------------------------------------------------------*/
 
 /* RPL DIO prefix suboption */
 struct rpl_prefix {
@@ -192,7 +214,7 @@ typedef struct rpl_prefix rpl_prefix_t;
 struct rpl_dio {
   uip_ipaddr_t dag_id;
   rpl_ocp_t ocp;
-  rpl_rank_t dag_rank;
+  rpl_rank_t rank;
   uint8_t grounded;
   uint8_t dst_adv_trigger;
   uint8_t dst_adv_supported;
@@ -216,7 +238,7 @@ struct rpl_dag {
   /* DAG configuration */
   rpl_of_t *of;
   uip_ipaddr_t dag_id;
-  /* this is  the current def-router that is set - used for routing "upwards" */
+  /* The current default router - used for routing "upwards" */
   uip_ds6_defrt_t *def_route;
   rpl_rank_t rank;
   rpl_rank_t min_rank; /* should be reset per DODAG iteration! */
@@ -245,7 +267,7 @@ struct rpl_dag {
   uint16_t dio_next_delay; /* delay for completion of dio interval */
   struct ctimer dio_timer;
   struct ctimer dao_timer;
-  rpl_parent_t *best_parent;
+  rpl_parent_t *preferred_parent;
   void *parent_list;
   list_t parents;
   rpl_prefix_t prefix_info;
@@ -254,7 +276,7 @@ struct rpl_dag {
 typedef struct rpl_dag rpl_dag_t;
 
 /*---------------------------------------------------------------------------*/
-/* RPL macro functions. */
+/* RPL macros. */
 #define RPL_PARENT_COUNT(dag)	list_length((dag)->parents)
 /*---------------------------------------------------------------------------*/
 /* ICMPv6 functions for RPL. */
@@ -270,6 +292,7 @@ int rpl_set_prefix(rpl_dag_t *dag, uip_ipaddr_t *prefix, int len);
 int rpl_repair_dag(rpl_dag_t *dag);
 int rpl_set_default_route(rpl_dag_t *dag, uip_ipaddr_t *from);
 void rpl_process_dio(uip_ipaddr_t *, rpl_dio_t *);
+int rpl_process_parent_event(rpl_dag_t *, rpl_parent_t *);
 
 /* DAG allocation and deallocation. */
 rpl_dag_t *rpl_alloc_dag(uint8_t);
@@ -279,7 +302,8 @@ void rpl_free_dag(rpl_dag_t *);
 rpl_parent_t *rpl_add_parent(rpl_dag_t *, rpl_dio_t *dio, uip_ipaddr_t *);
 rpl_parent_t *rpl_find_parent(rpl_dag_t *, uip_ipaddr_t *);
 int rpl_remove_parent(rpl_dag_t *, rpl_parent_t *);
-rpl_parent_t *rpl_preferred_parent(rpl_dag_t *dag);
+rpl_parent_t *rpl_select_parent(rpl_dag_t *dag);
+void rpl_recalculate_ranks(void);
 
 void rpl_join_dag(rpl_dag_t *);
 rpl_dag_t *rpl_get_dag(int instance_id);