zebra: Trust kernel and System routes

If we receive a valid message from the kernel that
is either a kernel or system route, we should trust
that the route is legit and just use it.

Old behavior:

K * 172.22.0.0/15 [0/0] via 172.22.2.254, eva_dummy1 inactive, 00:00:16

New Behavior:

K>* 172.22.0.0/15 [0/0] via 172.22.2.254, eva_dummy1, 00:02:35

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

zebra/zebra_rib.c

@@ -437,6 +437,14 @@ static int nexthop_active(afi_t afi, struct route_entry *re,
 	if (CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_EVPN_RVTEP))
 		return 1;
 
+	/*
+	 * If the kernel has sent us a route, then
+	 * by golly gee whiz it's a good route.
+	 */
+	if (re->type == ZEBRA_ROUTE_KERNEL ||
+	    re->type == ZEBRA_ROUTE_SYSTEM)
+		return 1;
+
 	/* Skip nexthops that have been filtered out due to route-map */
 	/* The nexthops are specific to this route and so the same */
 	/* nexthop for a different route may not have this flag set */