bgpd: fix accept-own routes received by a route reflector

When using the bgp-accept-own community, with the
'attribute-unchanged next-hop' command, the advertised
mpls vpn updates that are reflected by a route reflector
are received, but are not selected.

Once the accept-own community is detected, a new bgp_path
is created, in addition of the original one; then the
next-hop of the NLRI is checked, but fails for two reasons:
- the next-hop tracking returns the real IP reachability
status for prefixes that have the BGP_ROUTE_IMPORTED subtype.
This is what happens with bgp updates with the accept-own
community.
- as the next-hop was unchanged and was the peer IP in the VRF.
Consequently, the new bgp_path is considered inactive in the
default VRF, and is not selected.

The incoming bgp updates with the accept-own community should
not be checked against the next-hop tracking. As the bgp_path
subtype has been changed to BGP_ROUTE_IMPORTED, let us check
the bgp subtype before calling the 'bgp_find_or_add_nexthop()'
function in the 'bgp_update()' call.

Fixes: 46dbf9d0c0b9 bgpd: ("Implement ACCEPT_OWN extended community")
Fixes: 376797711f4d - bgpd: track mpls vpn nexthops
Fixes: e6110f755718 bgpd: ("fix use nexthop tracking for exported vpn paths")

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

1 files changed, 17 insertions, 2 deletions

diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
index c2e554cddb..b267f0d6bd 100644
--- a/bgpd/bgp_route.c
+++ b/bgpd/bgp_route.c
@@ -4744,7 +4744,8 @@ void bgp_update(struct peer *peer, const struct prefix *p, uint32_t addpath_id,
 		 * labeled-unicast.. */
 		if (((afi == AFI_IP || afi == AFI_IP6) &&
 		     (safi == SAFI_UNICAST || safi == SAFI_LABELED_UNICAST ||
-		      safi == SAFI_MPLS_VPN)) ||
+		      (safi == SAFI_MPLS_VPN &&
+		       pi->sub_type != BGP_ROUTE_IMPORTED))) ||
 		    (safi == SAFI_EVPN &&
 		     bgp_evpn_is_prefix_nht_supported(p))) {
 			if (safi != SAFI_EVPN && peer->sort == BGP_PEER_EBGP
@@ -4784,6 +4785,13 @@ void bgp_update(struct peer *peer, const struct prefix *p, uint32_t addpath_id,
 							 BGP_PATH_VALID);
 			}
 		} else {
+			/* case mpls-vpn routes with accept-own community
+			 * (which have the BGP_ROUTE_IMPORTED subtype)
+			 * case other afi/safi not supporting nexthop tracking
+			 */
+			if (accept_own)
+				bgp_path_info_set_flag(dest, pi,
+						       BGP_PATH_ACCEPT_OWN);
 			bgp_path_info_set_flag(dest, pi, BGP_PATH_VALID);
 		}
 
@@ -4915,7 +4923,8 @@ void bgp_update(struct peer *peer, const struct prefix *p, uint32_t addpath_id,
 	/* Nexthop reachability check. */
 	if (((afi == AFI_IP || afi == AFI_IP6) &&
 	     (safi == SAFI_UNICAST || safi == SAFI_LABELED_UNICAST ||
-	      safi == SAFI_MPLS_VPN)) ||
+	      (safi == SAFI_MPLS_VPN &&
+	       new->sub_type != BGP_ROUTE_IMPORTED))) ||
 	    (safi == SAFI_EVPN && bgp_evpn_is_prefix_nht_supported(p))) {
 		if (safi != SAFI_EVPN && peer->sort == BGP_PEER_EBGP
 		    && peer->ttl == BGP_DEFAULT_TTL
@@ -4944,6 +4953,12 @@ void bgp_update(struct peer *peer, const struct prefix *p, uint32_t addpath_id,
 			bgp_path_info_unset_flag(dest, new, BGP_PATH_VALID);
 		}
 	} else {
+		/* case mpls-vpn routes with accept-own community
+		 * (which have the BGP_ROUTE_IMPORTED subtype)
+		 * case other afi/safi not supporting nexthop tracking
+		 */
+		if (accept_own)
+			bgp_path_info_set_flag(dest, new, BGP_PATH_ACCEPT_OWN);
 		bgp_path_info_set_flag(dest, new, BGP_PATH_VALID);
 	}