[BGP]Optimize BGP during peer down as well has avoid handling duplicate link up

src/sonic-frr/patch/0081-bgpd-Optimize-evaluate-paths-for-a-peer-going-down.patch

@@ -0,0 +1,57 @@
+From f63a4be085b28c5138b95d55681f2bfb38bdaf4f Mon Sep 17 00:00:00 2001
+From: Donald Sharp <sharpd@nvidia.com>
+Date: Fri, 24 Jan 2025 15:04:13 -0500
+Subject: [PATCH] bgpd: Optimize evaluate paths for a peer going down
+
+Currently when a directly connected peer is going down
+BGP gets a call back for nexthop tracking in addition
+the interface down events.  On the interface down
+event BGP goes through and sets up a per peer Q that
+holds all the bgp path info's associated with that peer
+and then it goes and processes this in the future.  In
+the meantime zebra is also at work and sends a nexthop
+removal event to BGP as well.  This triggers a complete
+walk of all path info's associated with the bnc( which
+happens to be all the path info's already scheduled
+for removal here shortly).  This evaluate paths
+is not an inexpensive operation in addition the work
+for handling this is already being done via the
+peer down queue.  Let's optimize the bnc handling
+of evaluate paths and check to see if the peer is
+still up to actually do the work here.
+
+Signed-off-by: Donald Sharp <sharpd@nvidia.com>
+
+diff --git a/bgpd/bgp_nht.c b/bgpd/bgp_nht.c
+index 3b6db31ea0..196cc00385 100644
+--- a/bgpd/bgp_nht.c
++++ b/bgpd/bgp_nht.c
+@@ -1258,6 +1258,25 @@ void evaluate_paths(struct bgp_nexthop_cache *bnc)
+ 	}
+
+ 	LIST_FOREACH (path, &(bnc->paths), nh_thread) {
++		/*
++		 * Currently when a peer goes down, bgp immediately
++		 * sees this via the interface events( if it is directly
++		 * connected).  And in this case it takes and puts on
++		 * a special peer queue all path info's associated with
++		 * but these items are not yet processed typically when
++		 * the nexthop is being handled here.  Thus we end
++		 * up in a situation where the process Queue for BGP
++		 * is being asked to look at the same path info multiple
++		 * times.  Let's just cut to the chase here and if
++		 * the bnc has a peer associated with it and the path info
++		 * being looked at uses that peer and the peer is no
++		 * longer established we know the path_info is being
++		 * handled elsewhere and we do not need to process
++		 * it here at all since the pathinfo is going away
++		 */
++		if (peer && path->peer == peer && !peer_established(peer->connection))
++			continue;
++
+ 		if (path->type == ZEBRA_ROUTE_BGP &&
+ 		    (path->sub_type == BGP_ROUTE_NORMAL ||
+ 		     path->sub_type == BGP_ROUTE_STATIC ||
+-- 
+2.43.2
+

src/sonic-frr/patch/0082-Revert-bgpd-upon-if-event-evaluate-bnc-with-matching.patch

@@ -0,0 +1,78 @@
+From 086c32eb5bf2ebfb4805f76219c1a3bc5dd9213e Mon Sep 17 00:00:00 2001
+From: dgsudharsan <sudharsand@nvidia.com>
+Date: Wed, 19 Feb 2025 17:24:39 +0000
+Subject: [PATCH] Revert "bgpd: upon if event, evaluate bnc with matching
+ nexthop"
+
+This reverts commit 58592be57783a3b24e7351af2a5afc61299768df.
+
+diff --git a/bgpd/bgp_nht.c b/bgpd/bgp_nht.c
+index 196cc00385..78eb1a9183 100644
+--- a/bgpd/bgp_nht.c
++++ b/bgpd/bgp_nht.c
+@@ -751,10 +751,6 @@ static void bgp_nht_ifp_table_handle(struct bgp *bgp,
+ 				     struct interface *ifp, bool up)
+ {
+ 	struct bgp_nexthop_cache *bnc;
+-	struct nexthop *nhop;
+-	uint16_t other_nh_count;
+-	bool nhop_ll_found = false;
+-	bool nhop_found = false;
+
+ 	if (ifp->ifindex == IFINDEX_INTERNAL) {
+ 		zlog_warn("%s: The interface %s ignored", __func__, ifp->name);
+@@ -762,42 +758,9 @@ static void bgp_nht_ifp_table_handle(struct bgp *bgp,
+ 	}
+
+ 	frr_each (bgp_nexthop_cache, table, bnc) {
+-		other_nh_count = 0;
+-		nhop_ll_found = bnc->ifindex_ipv6_ll == ifp->ifindex;
+-		for (nhop = bnc->nexthop; nhop; nhop = nhop->next) {
+-			if (nhop->ifindex == bnc->ifindex_ipv6_ll)
+-				continue;
+-
+-			if (nhop->ifindex != ifp->ifindex) {
+-				other_nh_count++;
+-				continue;
+-			}
+-			if (nhop->vrf_id != ifp->vrf->vrf_id) {
+-				other_nh_count++;
+-				continue;
+-			}
+-			nhop_found = true;
+-		}
+-
+-		if (!nhop_found && !nhop_ll_found)
+-			/* The event interface does not match the nexthop cache
+-			 * entry */
+-			continue;
+-
+-		if (!up && other_nh_count > 0)
+-			/* Down event ignored in case of multiple next-hop
+-			 * interfaces. The other might interfaces might be still
+-			 * up. The cases where all interfaces are down or a bnc
+-			 * is invalid are processed by a separate zebra rnh
+-			 * messages.
+-			 */
++		if (bnc->ifindex_ipv6_ll != ifp->ifindex)
+ 			continue;
+
+-		if (!nhop_ll_found) {
+-			evaluate_paths(bnc);
+-			continue;
+-		}
+-
+ 		bnc->last_update = monotime(NULL);
+ 		bnc->change_flags = 0;
+
+@@ -810,7 +773,6 @@ static void bgp_nht_ifp_table_handle(struct bgp *bgp,
+ 		if (up) {
+ 			SET_FLAG(bnc->flags, BGP_NEXTHOP_VALID);
+ 			SET_FLAG(bnc->change_flags, BGP_NEXTHOP_CHANGED);
+-			/* change nexthop number only for ll */
+ 			bnc->nexthop_num = 1;
+ 		} else {
+ 			UNSET_FLAG(bnc->flags, BGP_NEXTHOP_PEER_NOTIFIED);
+-- 
+2.43.2
+

src/sonic-frr/patch/series

@@ -59,3 +59,5 @@
 0077-frr-vtysh-dependencies-for-srv6-static-patches.patch
 0078-vtysh-de-conditionalize-and-reorder-install-node.patch
 0079-staticd-add-support-for-srv6.patch
+0081-bgpd-Optimize-evaluate-paths-for-a-peer-going-down.patch
+0082-Revert-bgpd-upon-if-event-evaluate-bnc-with-matching.patch