added nbr policy for Contiki RPL that avoids thrashing the nbr table with new entries all the time

core/net/rpl/rpl-nbr-policy.c

@@ -0,0 +1,244 @@
+/*
+ * Copyright (c) 2014-2015, Yanzi Networks AB.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *    1. Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *    2. Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *    3. Neither the name of the copyright holders nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+/**
+ * \addtogroup uip6
+ * @{
+ */
+
+
+/**
+ * \file
+ *
+ * Default RPL NBR policy
+ * decides when to add a new discovered node to the nbr table from RPL.
+ *
+ * \author Joakim Eriksson <joakime@sics.se>
+ * Contributors: Niclas Finne <nfi@sics.se>, Oriol Piñol <oriol@yanzi.se>,
+ *
+ */
+
+#include "net/rpl/rpl-private.h"
+#include "net/nbr-table.h"
+#include "net/ipv6/uip-ds6-nbr.h"
+#include "net/ipv6/uip-ds6-route.h"
+
+#define DEBUG DEBUG_NONE
+#include "net/ip/uip-debug.h"
+
+/*
+ * Policy for neighbor adds
+ * - one node is locked (default route)
+ * - max X children (nexthops)
+ * - max Y "best parents"
+ * => at least MAX_NBRS - (Y + X + 1) free slots for other.
+ */
+
+#define MAX_CHILDREN (NBR_TABLE_MAX_NEIGHBORS - 3)
+
+static int num_parents; /* any node that are possible parents */
+static int num_children;  /* all children that we have as nexthop */
+static int num_free;
+static uip_ds6_nbr_t *worst_rank_nbr; /* the parent that has the worst rank */
+static rpl_rank_t worst_rank;
+/*---------------------------------------------------------------------------*/
+static void
+update_nbr(void)
+{
+  uip_ds6_nbr_t *nbr;
+  rpl_parent_t *parent;
+  int num_used;
+  int is_used;
+  rpl_rank_t rank;
+
+  worst_rank = 0;
+  worst_rank_nbr = NULL;
+  num_used = 0;
+  num_parents = 0;
+  num_children = 0;
+
+  nbr = nbr_table_head(ds6_neighbors);
+  while(nbr != NULL) {
+    linkaddr_t *lladdr = nbr_table_get_lladdr(ds6_neighbors, nbr);
+    is_used = 0;
+
+    parent = rpl_get_parent((uip_lladdr_t *)lladdr);
+    if(parent != NULL) {
+      num_parents++;
+      is_used++;
+
+      if(parent->dag != NULL && parent->dag->preferred_parent == parent) {
+        /* This is the preferred parent for the DAG and must not be removed */
+
+        /* Note: this assumes that only RPL adds default routes. */
+
+      } else if(worst_rank < INFINITE_RANK &&
+                parent->rank > 0 &&
+                parent->dag != NULL &&
+                parent->dag->instance != NULL &&
+                (rank = parent->dag->instance->of->calculate_rank(parent, 0)) > worst_rank) {
+        /* This is the worst-rank neighbor - this is a good candidate for removal */
+        worst_rank = rank;
+        worst_rank_nbr = nbr;
+      }
+    }
+
+    /* Check if this neighbor is used as nexthop and therefor being a
+       RPL child. */
+    if(uip_ds6_route_is_nexthop((uip_lladdr_t *)lladdr) != 0) {
+      is_used++;
+      num_children++;
+    }
+
+    if(is_used == 0) {
+      /* This neighbor is neither parent or child and can be safely removed */
+      worst_rank_nbr = nbr;
+      worst_rank = INFINITE_RANK;
+    } else if(is_used > 1) {
+      /* Both parent and child - this should never happen! */
+      PRINTF("NBR-POLICY: *** Neighbor is both child and candidate parent: ");
+      PRINTLLADDR((uip_lladdr_t *)lladdr);
+      PRINTF("\n");
+    }
+
+    nbr = nbr_table_next(ds6_neighbors, nbr);
+    num_used++;
+  }
+  /* how many more IP neighbors can be have? */
+  num_free = NBR_TABLE_MAX_NEIGHBORS - num_used;
+
+  PRINTF("NBR-POLICY: Free: %d, Children: %d, Parents: %d Routes: %d\n",
+	 num_free, num_children, num_parents, uip_ds6_route_num_routes());
+}
+/*---------------------------------------------------------------------------*/
+static int
+remove_worst_nbr(void)
+{
+  /* we assume that it is possible to remove the worst parent at the moment */
+  if(worst_rank_nbr != NULL) {
+    PRINTF("Removing worst ranked nbr ");
+    PRINTLLADDR((uip_lladdr_t*)nbr_table_get_lladdr(ds6_neighbors, worst_rank_nbr));
+    PRINTF(" with rank %d\n", worst_rank);
+    if(uip_ds6_nbr_rm(worst_rank_nbr)) {
+      worst_rank_nbr = NULL;
+      return 1;
+    }
+    PRINTF("FAILED to remove worst ranked nbr!\n");
+    return 0;
+  }
+  PRINTF("FAILED to remove worst rank nbr - no found\n");
+  return 0;
+}
+/*---------------------------------------------------------------------------*/
+/* Called whenever we get a unicast DIS - e.g. someone that already
+   have this node in its table - since it is a unicast */
+static int
+check_add_from_dis(uip_ipaddr_t *from)
+{
+
+  /* do a lookup to see if it is alread there - then allow add/update */
+  if(uip_ds6_nbr_lookup(from)) {
+    return 1;
+  }
+  update_nbr();
+  if(num_free > 0) {
+    return 1;
+  }
+  if(num_children < MAX_CHILDREN) {
+    return remove_worst_nbr();
+  }
+  return 0;
+}
+/*---------------------------------------------------------------------------*/
+static int
+check_add_from_dio(uip_ipaddr_t *from, rpl_dio_t *dio)
+{
+  rpl_instance_t *instance;
+  rpl_rank_t rank;
+
+  /* Do a lookup to see if it is already there - then allow add/update. */
+  if(uip_ds6_nbr_lookup(from)) {
+    return 1;
+  }
+
+  update_nbr();
+
+  /* If there is room for this neighbor just add it. */
+  if(num_free > 0) {
+    return 1;
+  }
+
+  instance = rpl_get_instance(dio->instance_id);
+  if(instance == NULL || instance->current_dag == NULL) {
+    PRINTF("Did not find instance id: %d\n", dio->instance_id);
+    return 0;
+  }
+
+  /* Add the new neighbor only if it is better than the preferred parent. */
+  rank = instance->of->calculate_rank(NULL, dio->rank);
+  if(rank < worst_rank - instance->min_hoprankinc / 2) {
+    /* Found *great* neighbor - add! */
+    PRINTF("Found better neighbor %d < %d - add to cache...\n",
+           rank, worst_rank);
+
+    return remove_worst_nbr();
+  }
+
+  PRINTF("Found worse neighbor with new %d and old %d - NOT add to cache.\n",
+         rank, worst_rank);
+  return 0;
+}
+/*---------------------------------------------------------------------------*/
+static int
+check_add_from_dao(uip_ipaddr_t *from)
+{
+  /* Do a lookup to see if it is alread there - then allow add/update. */
+  if(uip_ds6_nbr_lookup(from)) {
+    return 1;
+  }
+
+  update_nbr();
+
+  /* Check if this DAO sender is not yet neighbor and there is already too
+     many children. */
+  if(num_children >= MAX_CHILDREN) {
+    PRINTF("Can not add another child - already at max.\n");
+    return 0;
+  }
+
+  return 1;
+}
+/*---------------------------------------------------------------------------*/
+const struct nbr_policy rpl_nbr_policy = {
+  check_add_from_dis,
+  check_add_from_dio,
+  check_add_from_dao
+};
+/*---------------------------------------------------------------------------*/
+/** @}*/