bgpd: upon if event, evaluate bnc with matching nexthop

In BGP, when an interface event is detected or triggered,
the BNC that have a next-hop that matches the interface
are not evaluated.

The paths attached to the bnc context are evaluated in the
following situation:
- In the up event case, if at least one next-hop interface
matched the event interface.
- In the down event case, if there is no alternate next-hop
that does not use the event interface.

Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>

diff --git a/bgpd/bgp_nht.c b/bgpd/bgp_nht.c
index 6fa5c252a69866e05ffbce7fb4545428fed5f4dd..83a7fbd412e877eddd6d34c34a4ce2a10a15ace4 100644 (file)
--- a/bgpd/bgp_nht.c
+++ b/bgpd/bgp_nht.c
@@ -707,9 +707,40 @@ static void bgp_nht_ifp_table_handle(struct bgp *bgp,
                                     struct interface *ifp, bool up)
 {
        struct bgp_nexthop_cache *bnc;
+       struct nexthop *nhop;
+       uint8_t other_nh_count;
+       bool nhop_found;
 
        frr_each (bgp_nexthop_cache, table, bnc) {
-               if (bnc->ifindex_ipv6_ll != ifp->ifindex)
+               other_nh_count = 0;
+               nhop_found = bnc->ifindex_ipv6_ll == ifp->ifindex;
+               for (nhop = bnc->nexthop; nhop; nhop = nhop->next) {
+                       if (nhop->ifindex == bnc->ifindex_ipv6_ll)
+                               continue;
+
+                       if (nhop->ifindex != ifp->ifindex) {
+                               other_nh_count++;
+                               continue;
+                       }
+                       if (nhop->vrf_id != ifp->vrf->vrf_id) {
+                               other_nh_count++;
+                               continue;
+                       }
+                       nhop_found = true;
+               }
+
+               if (!nhop_found)
+                       /* The event interface does not match the nexthop cache
+                        * entry */
+                       continue;
+
+               if (!up && other_nh_count > 0)
+                       /* Down event ignored in case of multiple next-hop
+                        * interfaces. The other might interfaces might be still
+                        * up. The cases where all interfaces are down or a bnc
+                        * is invalid are processed by a separate zebra rnh
+                        * messages.
+                        */
                        continue;
 
                bnc->last_update = monotime(NULL);