bgpd: fix labels in adj-rib-in

In a BGP L3VPN context using ADJ-RIB-IN (ie. enabled with
'soft-reconfiguration inbound'), after applying a deny route-map and
removing it, the remote MPLS label information is lost. As a result, BGP
is unable to re-install the related routes in the RIB.

For example,

> router bgp 65500
> [..]
>  neighbor 192.0.2.2 remote-as 65501
>  address-family ipv4 vpn
>   neighbor 192.0.2.2 activate
>   neighbor 192.0.2.2 soft-reconfiguration inbound

The 192.168.0.0/24 prefix has a remote label value of 102 in the BGP
RIB.

> # show bgp ipv4 vpn 192.168.0.0/24
>  BGP routing table entry for 444:1:192.168.0.0/24, version 2
>  [..]
>      192.168.0.0 from 192.0.2.2
>        Origin incomplete, metric 0, valid, external, best (First path received)
>        Extended Community: RT:52:100
>        Remote label: 102

A route-map now filter all incoming BGP updates:

> route-map rmap deny 1
> router bgp 65500
>  address-family ipv4 vpn
>   neighbor 192.0.2.2 route-map rmap in

The prefix is now filtered:

> # show bgp ipv4 vpn 192.168.0.0/24
> #

The route-map is detached:

> router bgp 65500
>  address-family ipv4 vpn
>   no neighbor 192.168.0.1 route-map rmap in

The BGP RIB entry is present but the remote label is lost:

> # show bgp ipv4 vpn 192.168.0.0/24
>  BGP routing table entry for 444:1:192.168.0.0/24, version 2
>  [..]
>      192.168.0.0 from 192.0.2.2
>        Origin incomplete, metric 0, valid, external, best (First path received)
>        Extended Community: RT:52:100

The reason for the loose is that labels are stored within struct attr ->
struct extra -> struct bgp_labels but not in the struct bgp_adj_in.

Reference the bgp_labels pointer in struct bgp_adj_in and use its values
when doing a soft reconfiguration of the BGP table.

Signed-off-by: Philippe Guibert <[email protected]>
Signed-off-by: Louis Scalbert <[email protected]>

bgpd/bgp_advertise.c

@@ -163,7 +163,7 @@ bool bgp_adj_out_lookup(struct peer *peer, struct bgp_dest *dest,
 
 
 void bgp_adj_in_set(struct bgp_dest *dest, struct peer *peer, struct attr *attr,
-		    uint32_t addpath_id)
+		    uint32_t addpath_id, struct bgp_labels *labels)
 {
 	struct bgp_adj_in *adj;
 
@@ -173,6 +173,10 @@ void bgp_adj_in_set(struct bgp_dest *dest, struct peer *peer, struct attr *attr,
 				bgp_attr_unintern(&adj->attr);
 				adj->attr = bgp_attr_intern(attr);
 			}
+			if (!bgp_labels_cmp(adj->labels, labels)) {
+				bgp_labels_unintern(&adj->labels);
+				adj->labels = bgp_labels_intern(labels);
+			}
 			return;
 		}
 	}
@@ -181,13 +185,15 @@ void bgp_adj_in_set(struct bgp_dest *dest, struct peer *peer, struct attr *attr,
 	adj->attr = bgp_attr_intern(attr);
 	adj->uptime = monotime(NULL);
 	adj->addpath_rx_id = addpath_id;
+	adj->labels = bgp_labels_intern(labels);
 	BGP_ADJ_IN_ADD(dest, adj);
 	bgp_dest_lock_node(dest);
 }
 
 void bgp_adj_in_remove(struct bgp_dest **dest, struct bgp_adj_in *bai)
 {
 	bgp_attr_unintern(&bai->attr);
+	bgp_labels_unintern(&bai->labels);
 	BGP_ADJ_IN_DEL(*dest, bai);
 	*dest = bgp_dest_unlock_node(*dest);
 	peer_unlock(bai->peer); /* adj_in peer reference */

bgpd/bgp_advertise.h

@@ -95,6 +95,9 @@ struct bgp_adj_in {
 	/* Received attribute.  */
 	struct attr *attr;
 
+	/* VPN label information */
+	struct bgp_labels *labels;
+
 	/* timestamp (monotime) */
 	time_t uptime;
 
@@ -135,7 +138,8 @@ struct bgp_synchronize {
 extern bool bgp_adj_out_lookup(struct peer *peer, struct bgp_dest *dest,
 			       uint32_t addpath_tx_id);
 extern void bgp_adj_in_set(struct bgp_dest *dest, struct peer *peer,
-			   struct attr *attr, uint32_t addpath_id);
+			   struct attr *attr, uint32_t addpath_id,
+			   struct bgp_labels *labels);
 extern bool bgp_adj_in_unset(struct bgp_dest **dest, struct peer *peer,
 			     uint32_t addpath_id);
 extern void bgp_adj_in_remove(struct bgp_dest **dest, struct bgp_adj_in *bai);

bgpd/bgp_label.c

@@ -90,6 +90,10 @@ struct bgp_labels *bgp_labels_intern(struct bgp_labels *labels)
 	if (!labels)
 		return NULL;
 
+	if (!labels->num_labels)
+		/* do not intern void labels structure */
+		return NULL;
+
 	find = (struct bgp_labels *)hash_get(labels_hash, labels, bgp_labels_hash_alloc);
 	find->refcnt++;
 

bgpd/bgp_route.c

@@ -4278,7 +4278,7 @@ void bgp_update(struct peer *peer, const struct prefix *p, uint32_t addpath_id,
 			memcpy(&attr->evpn_overlay, evpn,
 			       sizeof(struct bgp_route_evpn));
 		}
-		bgp_adj_in_set(dest, peer, attr, addpath_id);
+		bgp_adj_in_set(dest, peer, attr, addpath_id, &bgp_labels);
 	}
 
 	/* Update permitted loop count */
@@ -5351,8 +5351,8 @@ static void bgp_soft_reconfig_table_update(struct peer *peer,
 		if (pi->peer == peer)
 			break;
 
-	num_labels = bgp_path_info_num_labels(pi);
-	label_pnt = num_labels ? &pi->extra->labels->label[0] : NULL;
+	num_labels = ain->labels && ain->labels->num_labels;
+	label_pnt = num_labels ? &ain->labels->label[0] : NULL;
 	if (pi)
 		memcpy(&evpn, bgp_attr_get_evpn_overlay(pi->attr),
 		       sizeof(evpn));