ospfd: do not generate type 4 LSA from NSSA ABR

In a topology like R1 -- R2 -- R5, with R2 being NSSA ABR and R5 being
ASBR redistributing external routes, the ABR R2 will translate type-7
LSA into type-5 and advertise to the backbone. In the current implementation
R2 is also advertising a type-4 LSA when there is no need.

RFC 3101: "...NSSA's border routers never originate Type-4 summary-LSAs
for the NSSA's AS boundary routers, since Type-7 AS-external-LSAs are
never flooded beyond the NSSA's border..."

With this PR a type-4 LSA will not be advertised

Signed-off-by: ckishimo <carles.kishimoto@gmail.com>

diff --git a/ospfd/ospf_abr.c b/ospfd/ospf_abr.c
index f6c05049990392fe2658369e35f81f39850dc09c..40a1ed3a8a11a17f382d556b85d4a81413d7a4a4 100644 (file)
--- a/ospfd/ospf_abr.c
+++ b/ospfd/ospf_abr.c
@@ -1153,6 +1153,15 @@ static void ospf_abr_announce_rtr(struct ospf *ospf, struct prefix_ipv4 *p,
                if (ospf_abr_nexthops_belong_to_area(or, area))
                        continue;
 
+               /* RFC3101: Do not generate ASBR type 4 LSA if NSSA ABR */
+               if (or->u.std.external_routing == OSPF_AREA_NSSA) {
+                       if (IS_DEBUG_OSPF_EVENT)
+                               zlog_debug(
+                                       "ospf_abr_announce_rtr(): do not generate LSA Type-4 %s from NSSA",
+                                       inet_ntoa(p->prefix));
+                       continue;
+               }
+
                if (area->external_routing != OSPF_AREA_DEFAULT) {
                        if (IS_DEBUG_OSPF_EVENT)
                                zlog_debug(