[FRR] Fix zebra memory leak when bgp fib suppress pending is enabled (sonic-net#17484) (sonic-net#17977)

Fix zebra leaking memory with fib suppress enabled. Porting the fix from
FRRouting/frr#14983

While running test_stress_route.py, systems with lower memory started to throw low memory logs. On further investigation, a memory leak has been found in zebra which was fixed in the FRR community.

Author: dgsudharsan

src/sonic-frr/patch/0033-zebra-The-dplane_fpm_nl-return-path-leaks-memory.patch

@@ -0,0 +1,57 @@
+From c13964525dae96299dc54daf635609971576a09e Mon Sep 17 00:00:00 2001
+From: Donald Sharp <[email protected]>
+Date: Mon, 11 Dec 2023 13:41:36 -0500
+Subject: [PATCH] zebra: The dplane_fpm_nl return path leaks memory
+
+The route entry created when using a ctx to pass route
+entry data backup to the master pthread in zebra is
+being leaked.  Prevent this from happening.
+
+Signed-off-by: Donald Sharp <[email protected]>
+
+diff --git a/zebra/rib.h b/zebra/rib.h
+index 016106312..e99eee67c 100644
+--- a/zebra/rib.h
++++ b/zebra/rib.h
+@@ -352,6 +352,8 @@ extern void _route_entry_dump(const char *func, union prefixconstptr pp,
+ 			      union prefixconstptr src_pp,
+ 			      const struct route_entry *re);
+ 
++void zebra_rib_route_entry_free(struct route_entry *re);
++
+ struct route_entry *
+ zebra_rib_route_entry_new(vrf_id_t vrf_id, int type, uint8_t instance,
+ 			  uint32_t flags, uint32_t nhe_id, uint32_t table_id,
+diff --git a/zebra/rt_netlink.c b/zebra/rt_netlink.c
+index 6bdc15592..fc9e8c457 100644
+--- a/zebra/rt_netlink.c
++++ b/zebra/rt_netlink.c
+@@ -1001,6 +1001,8 @@ int netlink_route_change_read_unicast_internal(struct nlmsghdr *h,
+ 						 re, ng, startup, ctx);
+ 			if (ng)
+ 				nexthop_group_delete(&ng);
++			if (ctx)
++				zebra_rib_route_entry_free(re);
+ 		} else {
+ 			/*
+ 			 * I really don't see how this is possible
+diff --git a/zebra/zebra_rib.c b/zebra/zebra_rib.c
+index f2f20bcf7..1cefdfae7 100644
+--- a/zebra/zebra_rib.c
++++ b/zebra/zebra_rib.c
+@@ -4136,6 +4136,12 @@ struct route_entry *zebra_rib_route_entry_new(vrf_id_t vrf_id, int type,
+ 
+ 	return re;
+ }
++
++void zebra_rib_route_entry_free(struct route_entry *re)
++{
++	XFREE(MTYPE_RE, re);
++}
++
+ /*
+  * Internal route-add implementation; there are a couple of different public
+  * signatures. Callers in this path are responsible for the memory they
+-- 
+2.17.1
+

src/sonic-frr/patch/series

@@ -29,6 +29,7 @@ cross-compile-changes.patch
 0030-bgpd-Treat-EOR-as-withdrawn-to-avoid-unwanted-handli.patch
 0031-bgpd-Ignore-handling-NLRIs-if-we-received-MP_UNREACH.patch
 0032-zebra-Fix-fpm-multipath-encap-addition.patch
+0033-zebra-The-dplane_fpm_nl-return-path-leaks-memory.patch
 0034-fpm-Use-vrf_id-for-vrf-not-tabled_id.patch
 0035-fpm-ignore-route-from-default-table.patch
 0036-Add-support-of-bgp-l3vni-evpn.patch