ospfd: blackhole route removal for area range

ISSUE

When an area range is created in which there the sub-area has routes that are
smaller than the range, an ABR creates a blackhole route to cover the range.
When the range is removed, the blackhole route is not removed.

--A----B----C---

B is an ABR with A in area 1 and C in area 0.  If A advertises `10.2.0.0/30` and
`10.2.0.4/30` and B is configured with `area 0.0.0.1 range 10.2.0.0/29` a
blackhole is created on B (`blackhole 10.2.0.0/29 proto zebra`).  When the
area/range is removed via the command line, the blackhole remains in existence
even though the "range" route is removed from area 0 and the individual routes
are propagated.

PATCH

The reason for this behavior is that, prior to this patch, the range is deleted
from the area's list, so when ospf_abr_manage_discard_routes() gets called,
there is nothing to clean up.  The patch removes the discard route as part of
the processing of the command line (ospf_area_range_unset()).

Signed-off-by: JR Rivers <jrrivers@cumulusnetworks.com>
Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com>
Reviewed-by: Shrijeet Mukherjee <shm@cumulusnetworks.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 49 insertions, 1 deletions

diff --git a/ospfd/ospf_route.c b/ospfd/ospf_route.c
index a5d6d18c..c3acba34 100644
--- a/ospfd/ospf_route.c
+++ b/ospfd/ospf_route.c
@@ -954,6 +954,10 @@ ospf_add_discard_route (struct route_table *rt, struct ospf_area *area,
       ospf_route_free (rn->info);
   }
 
+  if (IS_DEBUG_OSPF_EVENT)
+    zlog_debug ("ospf_add_discard_route(): "
+		"adding %s/%d", inet_ntoa (p->prefix), p->prefixlen);
+
   new_or = ospf_route_new ();
   new_or->type = OSPF_DESTINATION_DISCARD;
   new_or->id.s_addr = 0;
@@ -969,8 +973,52 @@ ospf_add_discard_route (struct route_table *rt, struct ospf_area *area,
 }
 
 void
-ospf_delete_discard_route (struct prefix_ipv4 *p)
+ospf_delete_discard_route (struct route_table *rt, struct prefix_ipv4 *p)
 {
+  struct route_node *rn;
+  struct ospf_route *or;
+
+  if (IS_DEBUG_OSPF_EVENT)
+    zlog_debug ("ospf_delete_discard_route(): "
+		"deleting %s/%d", inet_ntoa (p->prefix), p->prefixlen);
+
+  rn = route_node_lookup (rt, (struct prefix*)p);
+
+  if (rn == NULL)
+    {
+      if (IS_DEBUG_OSPF_EVENT)
+	zlog_debug("ospf_delete_discard_route(): no route found");
+      return;
+    }
+
+  or = rn->info;
+
+  if (or->path_type == OSPF_PATH_INTRA_AREA)
+    {
+      if (IS_DEBUG_OSPF_EVENT)
+	zlog_debug ("ospf_delete_discard_route(): "
+		    "an intra-area route exists");
+      return;
+    }
+
+  if (or->type != OSPF_DESTINATION_DISCARD)
+    {
+      if (IS_DEBUG_OSPF_EVENT)
+	zlog_debug ("ospf_delete_discard_route(): "
+		    "not a discard entry");
+      return;
+    }
+
+  /* free the route entry and the route node */
+  ospf_route_free (rn->info);
+
+  rn->info = NULL;
+  route_unlock_node (rn);
+  route_unlock_node (rn);
+
+  /* remove the discard entry from the rib */
   ospf_zebra_delete_discard(p);
+
+  return;
 }