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 source IP address of the neighbor on the link. This conforms
to RFC 2328 (page 96). The router adds itself as a "pseudo " neighbor
on each link, and also keeps a pointer called (nbr_self) to this
neighbor structure. This takes place when the interface is first configured.
ospfd adds this pseudo neighbor before the link parameters are fully
configured, including whether the link type is point-to-point or virtual
link. The causes the pseudo neighbor to be always indexed using the source
address regardless of its 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 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 <[email protected]>
---
diff --git a/ospfd/ospf_interface.c b/ospfd/ospf_interface.c
index f4242b0..d54bc47 100644
--- a/ospfd/ospf_interface.c
+++ b/ospfd/ospf_interface.c
@@ -232,8 +232,8 @@ ospf_if_new (struct ospf *ospf, struct interface
*ifp, struct prefix *p)
/* Set default values. */
ospf_if_reset_variables (oi);
- /* Add pseudo neighbor. */
- oi->nbr_self = ospf_nbr_new (oi);
+ /* Set pseudo neighbor to Null */
+ oi->nbr_self = NULL;
oi->ls_upd_queue = route_table_init ();
oi->t_ls_upd_event = NULL;
@@ -902,7 +902,9 @@ ospf_vl_new (struct ospf *ospf, struct ospf_vl_data
*vl_data)
if (IS_DEBUG_OSPF_EVENT)
zlog_debug ("ospf_vl_new(): set associated area to the backbone");
- ospf_nbr_add_self (voi);
+ /* Add pseudo neighbor. */
+ ospf_nbr_self_reset (voi);
+
ospf_area_add_if (voi->area, voi);
ospf_if_stream_set (voi);
diff --git a/ospfd/ospf_neighbor.c b/ospfd/ospf_neighbor.c
index 862de5e..86ab442 100644
--- a/ospfd/ospf_neighbor.c
+++ b/ospfd/ospf_neighbor.c
@@ -181,6 +181,31 @@ ospf_nbr_delete (struct ospf_neighbor *nbr)
route_unlock_node (rn);
}
+ else
+ {
+ /*
+ * This neighbor was not found, but bfore 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
+ */
+ assert (nbr != rn->info);
+ }
+ route_unlock_node (rn);
+ }
/* Free ospf_neighbor structure. */
ospf_nbr_free (nbr);
@@ -207,7 +232,9 @@ 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);
}
diff --git a/ospfd/ospfd.c b/ospfd/ospfd.c
index c9fcdc3..cc76e9e 100644
--- a/ospfd/ospfd.c
+++ b/ospfd/ospfd.c
@@ -754,9 +754,6 @@ add_ospf_interface (struct connected *co, struct
ospf_area *area)
oi->params = ospf_lookup_if_params (co->ifp, oi->address->u.prefix4);
oi->output_cost = ospf_if_get_output_cost (oi);
- /* Add pseudo neighbor. */
- ospf_nbr_add_self (oi);
-
/* Relate ospf interface to ospf instance. */
oi->ospf = area->ospf;
@@ -765,6 +762,9 @@ add_ospf_interface (struct connected *co, struct
ospf_area *area)
skip network type setting. */
oi->type = IF_DEF_PARAMS (co->ifp)->type;
+ /* Add pseudo neighbor. */
+ ospf_nbr_self_reset (oi);
+
ospf_area_add_if (oi->area, oi);
/* if router_id is not configured, dont bring up
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