Merge pull request FRRouting#19808 from opensourcerouting/fix/draft-ietf-idr-next-next-hop-nodes

bgpd: Put local BGP ID when sending NNHN TLV for NH characteristic

Author: Jafaral

bgpd/bgp_attr.c

@@ -3767,7 +3767,7 @@ static int bgp_attr_nhc(struct bgp_attr_parser_args *args)
 			zlog_debug("%pBP rcvd BGP NHC TLV code %d, length %d, value %p", peer,
 				   tlv->code, tlv->length, tlv->value);
 
-		/* draft-wang-idr-next-next-hop-nodes */
+		/* draft-ietf-idr-next-next-hop-nodes-00 */
 		if (tlv->code == BGP_ATTR_NHC_TLV_NNHN) {
 			if (tlv->length % IPV4_MAX_BYTELEN != 0) {
 				zlog_err("%pBP rcvd BGP NHC (NNHN TLV) length %d not a multiple of %d",
@@ -4640,6 +4640,7 @@ static void bgp_packet_nhc(struct stream *s, struct peer *peer, afi_t afi, safi_
 	prefix = bgp_dest_get_prefix(bpi->net);
 
 	total = bgp_path_info_mpath_count(bpi) * IPV4_MAX_BYTELEN;
+	total += IPV4_MAX_BYTELEN; /* Next-hop BGP ID */
 
 	stream_putc(s, BGP_ATTR_FLAG_OPTIONAL | BGP_ATTR_FLAG_TRANS);
 	stream_putc(s, BGP_ATTR_NHC);
@@ -4671,12 +4672,22 @@ static void bgp_packet_nhc(struct stream *s, struct peer *peer, afi_t afi, safi_
 	/* Put TLVs */
 
 	/* Begin NNHN TLV */
+	/*
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |    Characteristic Code = 2    |Characteristic Length(variable)|
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |                    Next-hop BGP ID                            |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 * |               Next-next-hop BGP IDs (variable)                |
+	 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	 */
 	if (bgp_path_info_mpath_count(bpi) > 1) {
 		if (bgp_debug_update(peer, NULL, NULL, 1))
 			zlog_debug("%pBP: Sending NHC TLV (%d) for %pFX", peer,
 				   BGP_ATTR_NHC_TLV_NNHN, prefix);
 		stream_putw(s, BGP_ATTR_NHC_TLV_NNHN);
 		stream_putw(s, total);
+		stream_put_ipv4(s, bpi->peer->local_id.s_addr);
 		stream_put_ipv4(s, bpi->peer->remote_id.s_addr);
 
 		for (exists = bgp_path_info_mpath_first(bpi); exists;

bgpd/bgp_nhc.c

@@ -89,9 +89,15 @@ uint64_t bgp_nhc_nnhn_count(struct bgp_nhc *nhc)
 		if (tlv->code == BGP_ATTR_NHC_TLV_NNHN) {
 			/* BGP Identifier is always 4-bytes (yet...) */
 			count = tlv->length / IPV4_MAX_BYTELEN;
-			break;
+			if (count <= 1)
+				return 0;
+
+			/* -1 is to exclude the next-hop BGP ID.
+			 * We care only about Next-next hops here.
+			 */
+			return count - 1;
 		}
 	}
 
-	return count;
+	return 0;
 }

bgpd/bgp_nhc.h

@@ -45,7 +45,7 @@ struct bgp_nhc {
 #define BGP_NHC_MIN_IPV6_LEN 24
 
 /* TLV values: */
-/* draft-wang-idr-next-next-hop-nodes */
+/* draft-ietf-idr-next-next-hop-nodes-00 */
 #define BGP_ATTR_NHC_TLV_NNHN 2
 /* draft-ietf-idr-entropy-label */
 #define BGP_ATTR_NHC_TLV_BGPID 3

bgpd/bgp_route.c

@@ -12663,7 +12663,9 @@ void route_vty_out_detail(struct vty *vty, struct bgp *bgp, struct bgp_dest *bn,
 					else
 						json_nhc_nnhn = json_object_new_array();
 
-					for (i = 0; i < tlv->length; i += IPV4_MAX_BYTELEN) {
+					/* First is Next-hop BGP ID, skip it. */
+					for (i = IPV4_MAX_BYTELEN; i < tlv->length;
+					     i += IPV4_MAX_BYTELEN) {
 						if (!json_paths) {
 							vty_out(vty, "       %pI4\n",
 								(struct in_addr *)&tlv->value[i]);