ospfd: fix - correct neighbor index on changing/p2p/virtual links

ospfd keeps a list of neighbor routers for each configured interface. This
 list is indexed using the neighbor router id in case of point-to-point and
 virtual link types, otherwise the list is indexed using the neighbor's
 source IP (RFC 2328, page 96). The router adds itself as a "pseudo" neighbor
 on each link, and also keeps a pointer called (nbr_self) to the neighbor
 structure. This takes place when the interface is first configured. Currently
 ospfd adds this pseudo neighbor before the link parameters are fully configure,
 including whether the link type is point-to-point or virtual link. This causes
 the pseudo neighbor to be always indexed using the source IP address regardless
 of th link type. For point-to-point and virtual links, this causes the lookup
 for the pseudo neighbor to always fail because the lookup is done using the
 router id whereas the neighbor was added using its source IP address.
 This becomes really problematic if there is a state change that requires a
 rebuild of nbr_self, changing the router id for example. When resetting
 nbr_self, the router first tries to remove the pseudo neighbor form its
 neighbor list on each link by looking it up and resetting any references to it
 before freeing the neighbor structure. since the lookup fails to retrieve any
 references in the case of point-to-point and virtual links the neighbor
 structure is freed leaving dangling references to it. Any access to the
 neighbor list after that is bound to stumble over this dangling pointer
 causing ospfd to crash.

Signed-off-by: Jafar Al-Gharaibeh <jafar@atcorp.com>
Tested-by: NetDEF CI System <cisystem@netdef.org>
(cherry picked from commit bb01bdd740339b0c07d8ed0786811801b2a79192)

1 files changed, 32 insertions, 1 deletions

diff --git a/ospfd/ospf_neighbor.c b/ospfd/ospf_neighbor.c
index 36251655a..46fcc6ba2 100644
--- a/ospfd/ospf_neighbor.c
+++ b/ospfd/ospf_neighbor.c
@@ -185,6 +185,35 @@ ospf_nbr_delete (struct ospf_neighbor *nbr)
 
       route_unlock_node (rn);
     }
+  else
+    {
+      /*
+       * This neighbor was not found, but before we move on and
+       * free the neighbor structre, make sure that it was not
+       * indexed incorrectly and ended up in the "worng" place
+       */
+
+      /* Reverse the lookup rules */
+      if (oi->type == OSPF_IFTYPE_VIRTUALLINK ||
+	  oi->type == OSPF_IFTYPE_POINTOPOINT)
+	p.u.prefix4 = nbr->src;
+      else
+	p.u.prefix4 = nbr->router_id;
+
+      rn = route_node_lookup (oi->nbrs, &p);
+      if (rn){
+	/* We found the neighbor!
+	 * Now make sure it is not the exact same neighbor
+	 * structure that we are about to free
+	 */
+	if (nbr == rn->info){
+	  /* Same neighbor, drop the reference to it */
+	  rn->info = NULL;
+	  route_unlock_node (rn);
+	}
+	route_unlock_node (rn);
+      }
+    }
 
   /* Free ospf_neighbor structure. */
   ospf_nbr_free (nbr);
@@ -211,7 +240,9 @@ ospf_nbr_bidirectional (struct in_addr *router_id,
 void
 ospf_nbr_self_reset (struct ospf_interface *oi)
 {
-  ospf_nbr_delete (oi->nbr_self);
+  if (oi->nbr_self)
+    ospf_nbr_delete (oi->nbr_self);
+
   oi->nbr_self = ospf_nbr_new (oi);
   ospf_nbr_add_self (oi);
 }