zebra: fix crash with nexthop group group type

The following crash happens when ZEBRA attempts to check
if the nexthop of the route has labeled nexthops or not.

> FRRouting#6  0x000055b590b14078 in zebra_rib_labeled_unicast (re=0x55b592b80640) at zebra/zebra_rib.c:671
> FRRouting#7  0x000055b590b14b1a in rib_process_add_fib (zvrf=0x55b592b6a740, rn=0x55b5929f02f0, new=0x55b592b80640) at zebra/zebra_rib.c:994
> FRRouting#8  0x000055b590b15ce9 in rib_process (rn=0x55b5929f02f0) at zebra/zebra_rib.c:1481
> FRRouting#9  0x000055b590b18927 in process_subq_route (lnode=0x55b592b806f0, qindex=8 '\b') at zebra/zebra_rib.c:2653
> FRRouting#10 0x000055b590b1a227 in process_subq (subq=0x55b5928a8d80, qindex=META_QUEUE_BGP) at zebra/zebra_rib.c:3256
> FRRouting#11 0x000055b590b1a30f in meta_queue_process (dummy=0x55b5928a8be0, data=0x55b5928a8c80) at zebra/zebra_rib.c:3295
> FRRouting#12 0x00007fdfd2790368 in work_queue_run (thread=0x7ffd2e913e10) at lib/workqueue.c:282
> FRRouting#13 0x00007fdfd277e5e6 in event_call (thread=0x7ffd2e913e10) at lib/event.c:1974
> FRRouting#14 0x00007fdfd26fcf43 in frr_run (master=0x55b59261aee0) at lib/libfrr.c:1214
> FRRouting#15 0x000055b590a9912b in main (argc=9, argv=0x7ffd2e9140e8) at zebra/main.c:509

When a nexthop group with TYPE_GROUP is used, the dependent
nexthop groups must be used instead.

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

zebra/zebra_rib.c

@@ -656,22 +656,44 @@ struct route_entry *rib_lookup_ipv4(struct prefix_ipv4 *p, vrf_id_t vrf_id)
 	return NULL;
 }
 
+static int _zebra_rib_labeled_unicast(struct nexthop_group *nhg)
+{
+	struct nexthop *nexthop = NULL;
+
+	for (ALL_NEXTHOPS_PTR(nhg, nexthop))
+		if (!nexthop->nh_label || !nexthop->nh_label->num_labels)
+			return 0;
+	return 1;
+}
 /*
  * Is this RIB labeled-unicast? It must be of type BGP and all paths
  * (nexthops) must have a label.
  */
 int zebra_rib_labeled_unicast(struct route_entry *re)
 {
-	struct nexthop *nexthop = NULL;
+	struct nexthop_group_id *nhgid;
+	struct nhg_hash_entry *nhe_tmp;
 
 	if (re->type != ZEBRA_ROUTE_BGP)
 		return 0;
 
-	for (ALL_NEXTHOPS(re->nhe->nhg, nexthop))
-		if (!nexthop->nh_label || !nexthop->nh_label->num_labels)
-			return 0;
+        if (re->nhe == NULL)
+		return 0;
 
-	return 1;
+	if (CHECK_FLAG(re->nhe->nhg.flags, NEXTHOP_GROUP_TYPE_GROUP)) {
+		for (nhgid = re->nhe->nhg.group; nhgid; nhgid = nhgid->next) {
+			nhe_tmp = zebra_nhg_lookup_id(nhgid->id_grp);
+			if (nhe_tmp)
+				nhgid->nhg = &nhe_tmp->nhg;
+			else
+				nhgid->nhg = NULL;
+			if (nhgid->nhg)
+				if (_zebra_rib_labeled_unicast(nhgid->nhg))
+					return 1;
+		}
+		return 0;
+	}
+	return _zebra_rib_labeled_unicast(&re->nhe->nhg);
 }