zebra: accept bgp remote mac-ip update if the higher-seq-local mac is not bgp-ready

If a local-MAC or local-neigh is not active locally it is not sent to BGP.
At this point if BGP rxes a remote route it accepts it and installs in
zebra. Zebra was rejecting BGP's update if it had a higher seq local (inactive)
entry. This would result in bgp and zebra falling out of sync.

In some cases zebra would delete the local-inactive entries in sometime (as
a part of the dplane/kernel garbage collection). This would leave zebra
with missing remote entries (which were still present in bgpd).

This change allows lower-seq BGP updates to overwrite zebra's local entry if
that entry happens to be local-inactive.

Note: This logic was already in use for sync-mac-ip updates. Extended the
same logic to remote-mac-ip updates.

Ticket: CM-31626

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>

1 files changed, 19 insertions, 32 deletions

diff --git a/zebra/zebra_evpn_neigh.c b/zebra/zebra_evpn_neigh.c
index d6de60cc22..1f45b72e3a 100644
--- a/zebra/zebra_evpn_neigh.c
+++ b/zebra/zebra_evpn_neigh.c
@@ -529,16 +529,21 @@ static void zebra_evpn_local_neigh_deref_mac(zebra_neigh_t *n,
 }
 
 bool zebra_evpn_neigh_is_bgp_seq_ok(zebra_evpn_t *zevpn, zebra_neigh_t *n,
-				    struct ethaddr *macaddr, uint32_t seq)
+				    struct ethaddr *macaddr, uint32_t seq,
+				    bool sync)
 {
 	char macbuf[ETHER_ADDR_STRLEN];
 	char ipbuf[INET6_ADDRSTRLEN];
 	uint32_t tmp_seq;
+	const char *n_type;
 
-	if (CHECK_FLAG(n->flags, ZEBRA_NEIGH_LOCAL))
+	if (CHECK_FLAG(n->flags, ZEBRA_NEIGH_LOCAL)) {
 		tmp_seq = n->loc_seq;
-	else
+		n_type = "local";
+	} else {
 		tmp_seq = n->rem_seq;
+		n_type = "remote";
+	}
 
 	if (seq < tmp_seq) {
 		/* if the neigh was never advertised to bgp we must accept
@@ -547,10 +552,12 @@ bool zebra_evpn_neigh_is_bgp_seq_ok(zebra_evpn_t *zevpn, zebra_neigh_t *n,
 		 */
 		if (CHECK_FLAG(n->flags, ZEBRA_NEIGH_LOCAL)
 		    && !zebra_evpn_neigh_is_ready_for_bgp(n)) {
-			if (IS_ZEBRA_DEBUG_EVPN_MH_NEIGH)
+			if (IS_ZEBRA_DEBUG_EVPN_MH_NEIGH
+			    || IS_ZEBRA_DEBUG_VXLAN)
 				zlog_debug(
-					"sync-macip accept vni %u mac %s IP %s lower seq %u f 0x%x",
-					zevpn->vni,
+					"%s-macip accept vni %u %s mac %s IP %s lower seq %u f 0x%x",
+					sync ? "sync" : "remote", zevpn->vni,
+					n_type,
 					prefix_mac2str(macaddr, macbuf,
 						       sizeof(macbuf)),
 					ipaddr2str(&n->ip, ipbuf,
@@ -559,10 +566,10 @@ bool zebra_evpn_neigh_is_bgp_seq_ok(zebra_evpn_t *zevpn, zebra_neigh_t *n,
 			return true;
 		}
 
-		if (IS_ZEBRA_DEBUG_EVPN_MH_NEIGH)
+		if (IS_ZEBRA_DEBUG_EVPN_MH_NEIGH || IS_ZEBRA_DEBUG_VXLAN)
 			zlog_debug(
-				"sync-macip ignore vni %u mac %s IP %s as existing has higher seq %u f 0x%x",
-				zevpn->vni,
+				"%s-macip ignore vni %u %s mac %s IP %s as existing has higher seq %u f 0x%x",
+				sync ? "sync" : "remote", zevpn->vni, n_type,
 				prefix_mac2str(macaddr, macbuf, sizeof(macbuf)),
 				ipaddr2str(&n->ip, ipbuf, sizeof(ipbuf)),
 				tmp_seq, n->flags);
@@ -2133,7 +2140,6 @@ void process_neigh_remote_macip_add(zebra_evpn_t *zevpn, struct zebra_vrf *zvrf,
 {
 	zebra_neigh_t *n;
 	int update_neigh = 0;
-	uint32_t tmp_seq;
 	char buf[ETHER_ADDR_STRLEN];
 	char buf1[INET6_ADDRSTRLEN];
 	zebra_mac_t *old_mac = NULL;
@@ -2170,8 +2176,6 @@ void process_neigh_remote_macip_add(zebra_evpn_t *zevpn, struct zebra_vrf *zvrf,
 			}
 
 		} else {
-			const char *n_type;
-
 			/* When host moves but changes its (MAC,IP)
 			 * binding, BGP may install a MACIP entry that
 			 * corresponds to "older" location of the host
@@ -2180,27 +2184,10 @@ void process_neigh_remote_macip_add(zebra_evpn_t *zevpn, struct zebra_vrf *zvrf,
 			 * the sequence number and ignore this update
 			 * if appropriate.
 			 */
-			if (CHECK_FLAG(n->flags, ZEBRA_NEIGH_LOCAL)) {
-				tmp_seq = n->loc_seq;
-				n_type = "local";
-			} else {
-				tmp_seq = n->rem_seq;
-				n_type = "remote";
-			}
-			if (seq < tmp_seq) {
-				if (IS_ZEBRA_DEBUG_VXLAN)
-					zlog_debug(
-						"Ignore remote MACIP ADD VNI %u MAC %s%s%s as existing %s Neigh has higher seq %u",
-						zevpn->vni,
-						prefix_mac2str(&mac->macaddr,
-							       buf,
-							       sizeof(buf)),
-						" IP ",
-						ipaddr2str(ipaddr, buf1,
-							   sizeof(buf1)),
-						n_type, tmp_seq);
+
+			if (!zebra_evpn_neigh_is_bgp_seq_ok(
+				    zevpn, n, &mac->macaddr, seq, false))
 				return;
-			}
 			if (CHECK_FLAG(n->flags, ZEBRA_NEIGH_LOCAL)) {
 				old_static = zebra_evpn_neigh_is_static(n);
 				if (IS_ZEBRA_DEBUG_EVPN_MH_NEIGH)