zebra: Prevent a kernel route from being there when a connected should

There exists a series of events where a kernel route is learned
first( that happens to be exactly what a connected route should be )
and FRR ends up with both a kernel route and a connected route,
leaving us in a very strange spot.  This code change just mirrors
the existing code of if there is a connected route drop the kernel
route.  Here we just do the reverse, if we have a kernel route
already and a connected should be created, remove the kernel and
keep the connected.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

diff --git a/zebra/connected.c b/zebra/connected.c
index 974a1c17a2925bbaba48b8b6eca0597b9ae6350b..ce26c14c052555fbe35b28555a690062a9340c32 100644 (file)
--- a/zebra/connected.c
+++ b/zebra/connected.c
@@ -176,6 +176,40 @@ static void connected_update(struct interface *ifp, struct connected *ifc)
                connected_announce(ifp, ifc);
 }
 
+/*
+ * This function goes through and handles the deletion of a kernel route that happened
+ * to be the exact same as the connected route, so that the connected route wins.
+ * This can happen during processing if we happen to receive events in a slightly
+ * unexpected order.  This is similiar to code in the other direction where if we
+ * have a kernel route don't install it if it perfectly matches a connected route.
+ */
+static void connected_remove_kernel_for_connected(afi_t afi, safi_t safi, struct zebra_vrf *zvrf,
+                                                 struct prefix *p, struct nexthop *nh)
+{
+       struct route_node *rn;
+       struct route_entry *re;
+       rib_dest_t *dest;
+       struct route_table *table = zebra_vrf_table(afi, SAFI_UNICAST, zvrf->vrf->vrf_id);
+
+       rn = route_node_match(table, p);
+       if (!rn)
+               return;
+
+       if (!prefix_same(&rn->p, p))
+               return;
+
+       dest = rib_dest_from_rnode(rn);
+       if (!dest || !dest->selected_fib)
+               return;
+
+       re = dest->selected_fib;
+       if (re->type != ZEBRA_ROUTE_KERNEL)
+               return;
+
+       rib_delete(afi, SAFI_UNICAST, zvrf->vrf->vrf_id, ZEBRA_ROUTE_KERNEL, 0, 0, p, NULL, nh, 0,
+                  zvrf->table_id, 0, 0, false);
+}
+
 /* Called from if_up(). */
 void connected_up(struct interface *ifp, struct connected *ifc)
 {
@@ -284,10 +318,13 @@ void connected_up(struct interface *ifp, struct connected *ifc)
        }
 
        if (!CHECK_FLAG(ifc->flags, ZEBRA_IFA_NOPREFIXROUTE)) {
+               connected_remove_kernel_for_connected(afi, SAFI_UNICAST, zvrf, &p, &nh);
+
                rib_add(afi, SAFI_UNICAST, zvrf->vrf->vrf_id,
                        ZEBRA_ROUTE_CONNECT, 0, flags, &p, NULL, &nh, 0,
                        zvrf->table_id, metric, 0, 0, 0, false);
 
+               connected_remove_kernel_for_connected(afi, SAFI_MULTICAST, zvrf, &p, &nh);
                rib_add(afi, SAFI_MULTICAST, zvrf->vrf->vrf_id,
                        ZEBRA_ROUTE_CONNECT, 0, flags, &p, NULL, &nh, 0,
                        zvrf->table_id, metric, 0, 0, 0, false);