[FRR] Fixing zebra to handle non notification of better admin won (#17184)

* [FRR]Fixing zebra to handle non notification of better admin won

* Updating the patch with latest changes from FRR

src/sonic-frr/patch/0027-zebra-Fix-non-notification-of-better-admin-won.patch

@@ -0,0 +1,70 @@
+From 41b759505afb261211f40e386a30f6cf3870a094 Mon Sep 17 00:00:00 2001
+From: dgsudharsan <sudharsand@nvidia.com>
+Date: Tue, 21 Nov 2023 17:55:24 +0000
+Subject: [PATCH] zebra: Fix non-notification of better admin won If there
+ happens to be a entry in the zebra rib that has a lower admin distance then a
+ newly received re, zebra would not notify the upper level protocol about this
+ happening.  Imagine a case where there is a connected route for say a /32 and
+ bgp receives a route from a peer that is the same route as the connected. 
+ Since BGP has no network statement and perceives the route as being `good`
+ bgp will install the route into zebra.  Zebra will look at the new bgp re and
+ correctly identify that the re is not something that it will use and do
+ nothing.  This change notices this and sends up a BETTER_ADMIN_WON route
+ notification.
+
+
+diff --git a/zebra/zebra_rib.c b/zebra/zebra_rib.c
+index 039c44cc09..f2f20bcf7b 100644
+--- a/zebra/zebra_rib.c
++++ b/zebra/zebra_rib.c
+@@ -1209,6 +1209,7 @@ static void rib_process(struct route_node *rn)
+ 	rib_dest_t *dest;
+ 	struct zebra_vrf *zvrf = NULL;
+ 	struct vrf *vrf;
++	struct route_entry *proto_re_changed = NULL;
+ 
+ 	vrf_id_t vrf_id = VRF_UNKNOWN;
+ 
+@@ -1278,6 +1279,7 @@ static void rib_process(struct route_node *rn)
+ 		 * skip it.
+ 		 */
+ 		if (CHECK_FLAG(re->status, ROUTE_ENTRY_CHANGED)) {
++			proto_re_changed = re;
+ 			if (!nexthop_active_update(rn, re)) {
+ 				const struct prefix *p;
+ 				struct rib_table_info *info;
+@@ -1363,6 +1365,8 @@ static void rib_process(struct route_node *rn)
+ 	 * new_selected --- RE entry that is newly SELECTED
+ 	 * old_fib      --- RE entry currently in kernel FIB
+ 	 * new_fib      --- RE entry that is newly to be in kernel FIB
++	 * proto_re_changed -- RE that is the last changed entry in the
++	 *                     list of RE's.
+ 	 *
+ 	 * new_selected will get SELECTED flag, and is going to be redistributed
+ 	 * the zclients. new_fib (which can be new_selected) will be installed
+@@ -1417,6 +1421,22 @@ static void rib_process(struct route_node *rn)
+ 		}
+ 	}
+ 
++	/*
++	 * If zebra has a new_selected and a proto_re_changed
++	 * entry that was not the old selected and the protocol
++	 * is different, zebra should notify the upper level
++	 * protocol that the sent down entry was not selected
++	 */
++	if (new_selected && proto_re_changed &&
++	    proto_re_changed != old_selected &&
++	    new_selected->type != proto_re_changed->type) {
++		struct rib_table_info *info = srcdest_rnode_table_info(rn);
++
++		zsend_route_notify_owner(rn, proto_re_changed,
++					 ZAPI_ROUTE_BETTER_ADMIN_WON, info->afi,
++					 info->safi);
++	}
++
+ 	/* Update fib according to selection results */
+ 	if (new_fib && old_fib)
+ 		rib_process_update_fib(zvrf, rn, old_fib, new_fib);
+-- 
+2.17.1
+

src/sonic-frr/patch/series

@@ -26,3 +26,4 @@ cross-compile-changes.patch
 0024-bgpd-Do-not-process-NLRIs-if-the-attribute-length-is.patch
 0025-bgpd-Use-treat-as-withdraw-for-tunnel-encapsulation-.patch
 0026-zebra-Add-encap-type-when-building-packet-for-FPM.patch
+0027-zebra-Fix-non-notification-of-better-admin-won.patch