From 490791eaa4d32aadfc77cfbcfb4cd718147426cb Mon Sep 17 00:00:00 2001
From: Adam Dunkels <adam@thingsquare.com>
Date: Wed, 20 Nov 2013 14:08:20 +0100
Subject: [PATCH] Add a check for the case when the parent neighbor may have
 gone away to avoid using a NULL pointer

---
 core/net/rpl/rpl-dag.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/core/net/rpl/rpl-dag.c b/core/net/rpl/rpl-dag.c
index 9560553bf..dff633a72 100644
--- a/core/net/rpl/rpl-dag.c
+++ b/core/net/rpl/rpl-dag.c
@@ -553,13 +553,17 @@ rpl_add_parent(rpl_dag_t *dag, rpl_dio_t *dio, uip_ipaddr_t *addr)
   if(lladdr != NULL) {
     /* Add parent in rpl_parents */
     p = nbr_table_add_lladdr(rpl_parents, (rimeaddr_t *)lladdr);
-    p->dag = dag;
-    p->rank = dio->rank;
-    p->dtsn = dio->dtsn;
-    p->link_metric = RPL_INIT_LINK_METRIC * RPL_DAG_MC_ETX_DIVISOR;
+    if(p == NULL) {
+      PRINTF("RPL: rpl_add_parent p NULL\n");
+    } else {
+      p->dag = dag;
+      p->rank = dio->rank;
+      p->dtsn = dio->dtsn;
+      p->link_metric = RPL_INIT_LINK_METRIC * RPL_DAG_MC_ETX_DIVISOR;
 #if RPL_DAG_MC != RPL_DAG_MC_NONE
-    memcpy(&p->mc, &dio->mc, sizeof(p->mc));
+      memcpy(&p->mc, &dio->mc, sizeof(p->mc));
 #endif /* RPL_DAG_MC != RPL_DAG_MC_NONE */
+    }
   }
 
   return p;