Merge pull request #7507 from ton31337/fix/bgpd_do_not_send_update_if_path_really_did_not_change

bgpd: Do not send BGP UPDATE if the route actually not changed

bgpd/bgp_advertise.h

@@ -83,6 +83,9 @@ struct bgp_adj_out {
 
 	/* Advertisement information.  */
 	struct bgp_advertise *adv;
+
+	/* Attribute hash */
+	uint32_t attr_hash;
 };
 
 RB_HEAD(bgp_adj_out_rb, bgp_adj_out);

bgpd/bgp_nb.c

@@ -351,6 +351,13 @@ const struct frr_yang_module_info frr_bgp_info = {
 				.modify = bgp_global_ebgp_requires_policy_modify,
 			}
 		},
+		{
+			.xpath = "/frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-bgp:bgp/global/suppress-duplicates",
+			.cbs = {
+				.cli_show = cli_show_router_bgp_suppress_duplicates,
+				.modify = bgp_global_suppress_duplicates_modify,
+			}
+		},
 		{
 			.xpath = "/frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-bgp:bgp/global/show-hostname",
 			.cbs = {

bgpd/bgp_nb.h

@@ -127,6 +127,7 @@ int bgp_global_fast_external_failover_modify(struct nb_cb_modify_args *args);
 int bgp_global_local_pref_modify(struct nb_cb_modify_args *args);
 int bgp_global_default_shutdown_modify(struct nb_cb_modify_args *args);
 int bgp_global_ebgp_requires_policy_modify(struct nb_cb_modify_args *args);
+int bgp_global_suppress_duplicates_modify(struct nb_cb_modify_args *args);
 int bgp_global_show_hostname_modify(struct nb_cb_modify_args *args);
 int bgp_global_show_nexthop_hostname_modify(struct nb_cb_modify_args *args);
 int bgp_global_import_check_modify(struct nb_cb_modify_args *args);
@@ -3639,6 +3640,9 @@ void cli_show_router_bgp_route_selection(struct vty *vty,
 void cli_show_router_bgp_ebgp_requires_policy(struct vty *vty,
 					      struct lyd_node *dnode,
 					      bool show_defaults);
+void cli_show_router_bgp_suppress_duplicates(struct vty *vty,
+					      struct lyd_node *dnode,
+					      bool show_defaults);
 void cli_show_router_bgp_default_shutdown(struct vty *vty,
 					  struct lyd_node *dnode,
 					  bool show_defaults);

bgpd/bgp_nb_config.c

@@ -1597,6 +1597,27 @@ int bgp_global_ebgp_requires_policy_modify(struct nb_cb_modify_args *args)
 	return NB_OK;
 }
 
+/*
+ * XPath:
+ * /frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-bgp:bgp/global/suppress-duplicates
+ */
+int bgp_global_suppress_duplicates_modify(struct nb_cb_modify_args *args)
+{
+	if (args->event != NB_EV_APPLY)
+		return NB_OK;
+
+	struct bgp *bgp;
+
+	bgp = nb_running_get_entry(args->dnode, NULL, true);
+
+	if (yang_dnode_get_bool(args->dnode, NULL))
+		SET_FLAG(bgp->flags, BGP_FLAG_SUPPRESS_DUPLICATES);
+	else
+		UNSET_FLAG(bgp->flags, BGP_FLAG_SUPPRESS_DUPLICATES);
+
+	return NB_OK;
+}
+
 /*
  * XPath:
  * /frr-routing:routing/control-plane-protocols/control-plane-protocol/frr-bgp:bgp/global/show-hostname

bgpd/bgp_packet.c

@@ -444,6 +444,13 @@ int bgp_generate_updgrp_packets(struct thread *thread)
 			 * yet.
 			 */
 			if (!next_pkt || !next_pkt->buffer) {
+				/* Make sure we supress BGP UPDATES
+				 * for normal processing later again.
+				 */
+				if (!paf->t_announce_route)
+					UNSET_FLAG(paf->subgroup->sflags,
+						   SUBGRP_STATUS_FORCE_UPDATES);
+
 				if (CHECK_FLAG(peer->cap,
 					       PEER_CAP_RESTART_RCV)) {
 					if (!(PAF_SUBGRP(paf))->t_coalesce
@@ -2116,6 +2123,11 @@ static int bgp_route_refresh_receive(struct peer *peer, bgp_size_t size)
 				peer->orf_plist[afi][safi];
 		}
 
+		/* Avoid supressing duplicate routes later
+		 * when processing in subgroup_announce_table().
+		 */
+		SET_FLAG(paf->subgroup->sflags, SUBGRP_STATUS_FORCE_UPDATES);
+
 		/* If the peer is configured for default-originate clear the
 		 * SUBGRP_STATUS_DEFAULT_ORIGINATE flag so that we will
 		 * re-advertise the

bgpd/bgp_updgrp.c

@@ -1387,6 +1387,11 @@ static int updgrp_policy_update_walkcb(struct update_group *updgrp, void *arg)
 	}
 
 	UPDGRP_FOREACH_SUBGRP (updgrp, subgrp) {
+		/* Avoid supressing duplicate routes later
+		 * when processing in subgroup_announce_table().
+		 */
+		SET_FLAG(subgrp->sflags, SUBGRP_STATUS_FORCE_UPDATES);
+
 		if (changed) {
 			if (bgp_debug_update(NULL, NULL, updgrp, 0))
 				zlog_debug(

bgpd/bgp_updgrp.h

@@ -252,19 +252,13 @@ struct update_subgroup {
 	uint64_t id;
 
 	uint16_t sflags;
+#define SUBGRP_STATUS_DEFAULT_ORIGINATE (1 << 0)
+#define SUBGRP_STATUS_FORCE_UPDATES (1 << 1)
 
-	/* Subgroup flags, see below  */
 	uint16_t flags;
+#define SUBGRP_FLAG_NEEDS_REFRESH (1 << 0)
 };
 
-/*
- * We need to do an outbound refresh to get this subgroup into a
- * consistent state.
- */
-#define SUBGRP_FLAG_NEEDS_REFRESH         (1 << 0)
-
-#define SUBGRP_STATUS_DEFAULT_ORIGINATE   (1 << 0)
-
 /*
  * Add the given value to the specified counter on a subgroup and its
  * parent structures.

bgpd/bgp_updgrp_adv.c

@@ -464,6 +464,7 @@ void bgp_adj_out_set_subgroup(struct bgp_dest *dest,
 	struct peer *adv_peer;
 	struct peer_af *paf;
 	struct bgp *bgp;
+	uint32_t attr_hash = attrhash_key_make(attr);
 
 	peer = SUBGRP_PEER(subgrp);
 	afi = SUBGRP_AFI(subgrp);
@@ -487,6 +488,26 @@ void bgp_adj_out_set_subgroup(struct bgp_dest *dest,
 			return;
 	}
 
+	/* Check if we are sending the same route. This is needed to
+	 * avoid duplicate UPDATES. For instance, filtering communities
+	 * at egress, neighbors will see duplicate UPDATES despite
+	 * the route wasn't changed actually.
+	 * Do not suppress BGP UPDATES for route-refresh.
+	 */
+	if (CHECK_FLAG(bgp->flags, BGP_FLAG_SUPPRESS_DUPLICATES)
+	    && !CHECK_FLAG(subgrp->sflags, SUBGRP_STATUS_FORCE_UPDATES)
+	    && adj->attr_hash == attr_hash) {
+		if (BGP_DEBUG(update, UPDATE_OUT)) {
+			char attr_str[BUFSIZ] = {0};
+
+			bgp_dump_attr(attr, attr_str, sizeof(attr_str));
+
+			zlog_debug("%s suppress UPDATE w/ attr: %s", peer->host,
+				   attr_str);
+		}
+		return;
+	}
+
 	if (adj->adv)
 		bgp_advertise_clean_subgroup(subgrp, adj);
 	adj->adv = bgp_advertise_new();
@@ -502,6 +523,7 @@ void bgp_adj_out_set_subgroup(struct bgp_dest *dest,
 	else
 		adv->baa = baa_new();
 	adv->adj = adj;
+	adj->attr_hash = attr_hash;
 
 	/* Add new advertisement to advertisement attribute list. */
 	bgp_advertise_add(adv->baa, adv);

bgpd/bgp_vty.c

@@ -119,6 +119,10 @@ FRR_CFG_DEFAULT_BOOL(BGP_EBGP_REQUIRES_POLICY,
 	{ .val_bool = false, .match_version = "< 7.4", },
 	{ .val_bool = true },
 )
+FRR_CFG_DEFAULT_BOOL(BGP_SUPPRESS_DUPLICATES,
+	{ .val_bool = false, .match_version = "< 7.6", },
+	{ .val_bool = true },
+)
 
 DEFINE_HOOK(bgp_inst_config_write,
 		(struct bgp *bgp, struct vty *vty),
@@ -487,6 +491,8 @@ int bgp_get_vty(struct bgp **bgp, as_t *as, const char *name,
 			SET_FLAG((*bgp)->flags, BGP_FLAG_DETERMINISTIC_MED);
 		if (DFLT_BGP_EBGP_REQUIRES_POLICY)
 			SET_FLAG((*bgp)->flags, BGP_FLAG_EBGP_REQUIRES_POLICY);
+		if (DFLT_BGP_SUPPRESS_DUPLICATES)
+			SET_FLAG((*bgp)->flags, BGP_FLAG_SUPPRESS_DUPLICATES);
 
 		ret = BGP_SUCCESS;
 	}
@@ -876,6 +882,7 @@ static int bgp_peer_clear(struct peer *peer, afi_t afi, safi_t safi,
 			  struct listnode **nnode, enum bgp_clear_type stype)
 {
 	int ret = 0;
+	struct peer_af *paf;
 
 	/* if afi/.safi not specified, spin thru all of them */
 	if ((afi == AFI_UNSPEC) && (safi == SAFI_UNSPEC)) {
@@ -883,6 +890,11 @@ static int bgp_peer_clear(struct peer *peer, afi_t afi, safi_t safi,
 		safi_t tmp_safi;
 
 		FOREACH_AFI_SAFI (tmp_afi, tmp_safi) {
+			paf = peer_af_find(peer, tmp_afi, tmp_safi);
+			if (paf && paf->subgroup)
+				SET_FLAG(paf->subgroup->sflags,
+					 SUBGRP_STATUS_FORCE_UPDATES);
+
 			if (!peer->afc[tmp_afi][tmp_safi])
 				continue;
 
@@ -901,6 +913,11 @@ static int bgp_peer_clear(struct peer *peer, afi_t afi, safi_t safi,
 			if (!peer->afc[afi][tmp_safi])
 				continue;
 
+			paf = peer_af_find(peer, afi, tmp_safi);
+			if (paf && paf->subgroup)
+				SET_FLAG(paf->subgroup->sflags,
+					 SUBGRP_STATUS_FORCE_UPDATES);
+
 			if (stype == BGP_CLEAR_SOFT_NONE)
 				ret = peer_clear(peer, nnode);
 			else
@@ -912,6 +929,11 @@ static int bgp_peer_clear(struct peer *peer, afi_t afi, safi_t safi,
 		if (!peer->afc[afi][safi])
 			return 1;
 
+		paf = peer_af_find(peer, afi, safi);
+		if (paf && paf->subgroup)
+			SET_FLAG(paf->subgroup->sflags,
+				 SUBGRP_STATUS_FORCE_UPDATES);
+
 		if (stype == BGP_CLEAR_SOFT_NONE)
 			ret = peer_clear(peer, nnode);
 		else
@@ -2555,6 +2577,37 @@ DEFUN_YANG(no_bgp_always_compare_med,
 	return nb_cli_apply_changes(vty, NULL);
 }
 
+DEFUN_YANG(bgp_suppress_duplicates,
+	   bgp_suppress_duplicates_cmd,
+	   "bgp suppress-duplicates",
+	   "BGP specific commands\n"
+	   "Suppress duplicate updates if the route actually not changed\n")
+{
+	nb_cli_enqueue_change(vty, "./global/suppress-duplicates",
+			      NB_OP_MODIFY, "true");
+	return nb_cli_apply_changes(vty, NULL);
+}
+
+DEFUN_YANG(no_bgp_suppress_duplicates,
+	   no_bgp_suppress_duplicates_cmd,
+	   "no bgp suppress-duplicates",
+	   NO_STR
+	   "BGP specific commands\n"
+	   "Suppress duplicate updates if the route actually not changed\n")
+{
+	nb_cli_enqueue_change(vty, "./global/suppress-duplicates",
+			      NB_OP_MODIFY, "false");
+	return nb_cli_apply_changes(vty, NULL);
+}
+
+void cli_show_router_bgp_suppress_duplicates(struct vty *vty,
+					      struct lyd_node *dnode,
+					      bool show_defaults)
+{
+	if (yang_dnode_get_bool(dnode, NULL) != SAVE_BGP_SUPPRESS_DUPLICATES)
+		vty_out(vty, " bgp suppress-duplicates\n");
+}
+
 DEFUN_YANG(bgp_ebgp_requires_policy,
 	   bgp_ebgp_requires_policy_cmd,
 	   "bgp ebgp-requires-policy",
@@ -17031,6 +17084,16 @@ int bgp_config_write(struct vty *vty)
 		if (bgp->reject_as_sets)
 			vty_out(vty, " bgp reject-as-sets\n");
 
+		/* Suppress duplicate updates if the route actually not changed
+		 */
+		if (!!CHECK_FLAG(bgp->flags, BGP_FLAG_SUPPRESS_DUPLICATES)
+		    != SAVE_BGP_SUPPRESS_DUPLICATES)
+			vty_out(vty, " %sbgp suppress-duplicates\n",
+				CHECK_FLAG(bgp->flags,
+					   BGP_FLAG_SUPPRESS_DUPLICATES)
+					? ""
+					: "no ");
+
 		/* BGP default ipv4-unicast. */
 		if (CHECK_FLAG(bgp->flags, BGP_FLAG_NO_DEFAULT_IPV4))
 			vty_out(vty, " no bgp default ipv4-unicast\n");
@@ -17614,6 +17677,10 @@ void bgp_vty_init(void)
 	install_element(BGP_NODE, &bgp_ebgp_requires_policy_cmd);
 	install_element(BGP_NODE, &no_bgp_ebgp_requires_policy_cmd);
 
+	/* bgp suppress-duplicates */
+	install_element(BGP_NODE, &bgp_suppress_duplicates_cmd);
+	install_element(BGP_NODE, &no_bgp_suppress_duplicates_cmd);
+
 	/* bgp reject-as-sets */
 	install_element(BGP_NODE, &bgp_reject_as_sets_cmd);
 	install_element(BGP_NODE, &no_bgp_reject_as_sets_cmd);

bgpd/bgpd.h

@@ -464,6 +464,7 @@ struct bgp {
 /* This flag is set if the instance is in administrative shutdown */
 #define BGP_FLAG_SHUTDOWN                 (1 << 27)
 #define BGP_FLAG_SUPPRESS_FIB_PENDING     (1 << 28)
+#define BGP_FLAG_SUPPRESS_DUPLICATES      (1 << 29)
 
 	enum global_mode GLOBAL_GR_FSM[BGP_GLOBAL_GR_MODE]
 				      [BGP_GLOBAL_GR_EVENT_CMD];

doc/user/bgp.rst

@@ -454,6 +454,17 @@ Reject routes with AS_SET or AS_CONFED_SET types
 
    This command enables rejection of incoming and outgoing routes having AS_SET or AS_CONFED_SET type.
 
+Suppress duplicate updates
+--------------------------
+
+.. index:: [no] bgp suppress-duplicates
+.. clicmd:: [no] bgp suppress-duplicates
+
+   For example, BGP routers can generate multiple identical announcements with
+   empty community attributes if stripped at egress. This is an undesired behavior.
+   Suppress duplicate updates if the route actually not changed.
+   Default: enabled.
+
 Disable checking if nexthop is connected on EBGP sessions
 ---------------------------------------------------------
 

tests/topotests/bgp_community_change_update/c1/bgpd.conf

@@ -0,0 +1,11 @@
+!
+debug bgp updates
+!
+router bgp 65001
+  no bgp ebgp-requires-policy
+  neighbor 10.0.1.2 remote-as external
+  neighbor 10.0.1.2 timers 3 10
+  address-family ipv4 unicast
+    redistribute connected
+  exit-address-family
+!

tests/topotests/bgp_community_change_update/c1/zebra.conf

@@ -0,0 +1,6 @@
+!
+interface c1-eth0
+ ip address 10.0.1.1/30
+!
+ip forwarding
+!

tests/topotests/bgp_community_change_update/test_bgp_community_change_update.py

@@ -0,0 +1,225 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2020 by
+# Donatas Abraitis <donatas.abraitis@gmail.com>
+#
+# Permission to use, copy, modify, and/or distribute this software
+# for any purpose with or without fee is hereby granted, provided
+# that the above copyright notice and this permission notice appear
+# in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND NETDEF DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NETDEF BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+#
+
+"""
+Reference: https://www.cmand.org/communityexploration
+
+                     --y2--
+                    /  |   \
+  c1 ---- x1 ---- y1   |   z1
+                    \  |   /
+                     --y3--
+
+1. z1 announces 192.168.255.254/32 to y2, y3.
+2. y2 and y3 tags this prefix at ingress with appropriate
+communities 65004:2 (y2) and 65004:3 (y3).
+3. x1 filters all communities at the egress to c1.
+4. Shutdown the link between y1 and y2.
+5. y1 will generate a BGP UPDATE message regarding the next-hop change.
+6. x1 will generate a BGP UPDATE message regarding community change.
+
+To avoid sending duplicate BGP UPDATE messages we should make sure
+we send only actual route updates. In this example, x1 will skip
+BGP UPDATE to c1 because the actual route is the same
+(filtered communities - nothing changes).
+"""
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+
+# pylint: disable=C0413
+from lib import topotest
+from lib.topogen import Topogen, TopoRouter, get_topogen
+from lib.topolog import logger
+from mininet.topo import Topo
+
+from lib.common_config import step
+from time import sleep
+
+
+class TemplateTopo(Topo):
+    def build(self, *_args, **_opts):
+        tgen = get_topogen(self)
+
+        tgen.add_router("z1")
+        tgen.add_router("y1")
+        tgen.add_router("y2")
+        tgen.add_router("y3")
+        tgen.add_router("x1")
+        tgen.add_router("c1")
+
+        # 10.0.1.0/30
+        switch = tgen.add_switch("s1")
+        switch.add_link(tgen.gears["c1"])
+        switch.add_link(tgen.gears["x1"])
+
+        # 10.0.2.0/30
+        switch = tgen.add_switch("s2")
+        switch.add_link(tgen.gears["x1"])
+        switch.add_link(tgen.gears["y1"])
+
+        # 10.0.3.0/30
+        switch = tgen.add_switch("s3")
+        switch.add_link(tgen.gears["y1"])
+        switch.add_link(tgen.gears["y2"])
+
+        # 10.0.4.0/30
+        switch = tgen.add_switch("s4")
+        switch.add_link(tgen.gears["y1"])
+        switch.add_link(tgen.gears["y3"])
+
+        # 10.0.5.0/30
+        switch = tgen.add_switch("s5")
+        switch.add_link(tgen.gears["y2"])
+        switch.add_link(tgen.gears["y3"])
+
+        # 10.0.6.0/30
+        switch = tgen.add_switch("s6")
+        switch.add_link(tgen.gears["y2"])
+        switch.add_link(tgen.gears["z1"])
+
+        # 10.0.7.0/30
+        switch = tgen.add_switch("s7")
+        switch.add_link(tgen.gears["y3"])
+        switch.add_link(tgen.gears["z1"])
+
+
+def setup_module(mod):
+    tgen = Topogen(TemplateTopo, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for i, (rname, router) in enumerate(router_list.items(), 1):
+        router.load_config(
+            TopoRouter.RD_ZEBRA, os.path.join(CWD, "{}/zebra.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_BGP, os.path.join(CWD, "{}/bgpd.conf".format(rname))
+        )
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_bgp_community_update_path_change():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    def _bgp_converge_initial():
+        output = json.loads(
+            tgen.gears["c1"].vtysh_cmd("show ip bgp neighbor 10.0.1.2 json")
+        )
+        expected = {
+            "10.0.1.2": {
+                "bgpState": "Established",
+                "addressFamilyInfo": {"ipv4Unicast": {"acceptedPrefixCounter": 8}},
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    step("Check if an initial topology is converged")
+    test_func = functools.partial(_bgp_converge_initial)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see bgp convergence in c1"
+
+    step("Disable link between y1 and y2")
+    tgen.gears["y1"].run("ip link set dev y1-eth1 down")
+
+    def _bgp_converge_link_disabled():
+        output = json.loads(tgen.gears["y1"].vtysh_cmd("show ip bgp nei 10.0.3.2 json"))
+        expected = {"10.0.3.2": {"bgpState": "Active"}}
+        return topotest.json_cmp(output, expected)
+
+    step("Check if a topology is converged after a link down between y1 and y2")
+    test_func = functools.partial(_bgp_converge_link_disabled)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see bgp convergence in y1"
+
+    def _bgp_check_for_duplicate_updates():
+        duplicate = False
+        i = 0
+        while i < 5:
+            if (
+                len(
+                    tgen.gears["c1"].run(
+                        'grep "10.0.1.2 rcvd 192.168.255.254/32 IPv4 unicast...duplicate ignored" bgpd.log'
+                    )
+                )
+                > 0
+            ):
+                duplicate = True
+            i += 1
+            sleep(0.5)
+        return duplicate
+
+    step("Check if we see duplicate BGP UPDATE message in c1 (suppress-duplicates)")
+    assert (
+        _bgp_check_for_duplicate_updates() == False
+    ), "Seen duplicate BGP UPDATE message in c1 from x1"
+
+    step("Disable bgp suppress-duplicates at x1")
+    tgen.gears["x1"].run(
+        "vtysh -c 'conf' -c 'router bgp' -c 'no bgp suppress-duplicates'"
+    )
+
+    step("Enable link between y1 and y2")
+    tgen.gears["y1"].run("ip link set dev y1-eth1 up")
+
+    def _bgp_converge_link_enabled():
+        output = json.loads(tgen.gears["y1"].vtysh_cmd("show ip bgp nei 10.0.3.2 json"))
+        expected = {
+            "10.0.3.2": {
+                "bgpState": "Established",
+                "addressFamilyInfo": {
+                    "ipv4Unicast": {"acceptedPrefixCounter": 5, "sentPrefixCounter": 4}
+                },
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    step("Check if a topology is converged after a link up between y1 and y2")
+    test_func = functools.partial(_bgp_converge_link_enabled)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see bgp convergence in y1"
+
+    step(
+        "Check if we see duplicate BGP UPDATE message in c1 (no bgp suppress-duplicates)"
+    )
+    assert (
+        _bgp_check_for_duplicate_updates() == True
+    ), "Didn't see duplicate BGP UPDATE message in c1 from x1"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))

tests/topotests/bgp_community_change_update/x1/bgpd.conf

@@ -0,0 +1,20 @@
+!
+debug bgp updates
+!
+router bgp 65002
+  no bgp ebgp-requires-policy
+  neighbor 10.0.1.1 remote-as external
+  neighbor 10.0.1.1 timers 3 10
+  neighbor 10.0.2.2 remote-as external
+  neighbor 10.0.2.2 timers 3 10
+  address-family ipv4 unicast
+    redistribute connected
+    neighbor 10.0.1.1 route-map c1 out
+  exit-address-family
+!
+bgp community-list standard c1 seq 1 permit 65004:2
+bgp community-list standard c1 seq 2 permit 65004:3
+!
+route-map c1 permit 10
+  set comm-list c1 delete
+!

tests/topotests/bgp_community_change_update/x1/zebra.conf

@@ -0,0 +1,9 @@
+!
+interface x1-eth0
+ ip address 10.0.1.2/30
+!
+interface x1-eth1
+ ip address 10.0.2.1/30
+!
+ip forwarding
+!

tests/topotests/bgp_community_change_update/y1/bgpd.conf

@@ -0,0 +1,12 @@
+router bgp 65003
+  no bgp ebgp-requires-policy
+  neighbor 10.0.2.1 remote-as external
+  neighbor 10.0.2.1 timers 3 10
+  neighbor 10.0.3.2 remote-as internal
+  neighbor 10.0.3.2 timers 3 10
+  neighbor 10.0.4.2 remote-as internal
+  neighbor 10.0.4.2 timers 3 10
+  address-family ipv4 unicast
+    redistribute connected
+  exit-address-family
+!

tests/topotests/bgp_community_change_update/y1/zebra.conf

@@ -0,0 +1,12 @@
+!
+interface y1-eth0
+ ip address 10.0.2.2/30
+!
+interface y1-eth1
+ ip address 10.0.3.1/30
+!
+interface y1-eth2
+ ip address 10.0.4.1/30
+!
+ip forwarding
+!

tests/topotests/bgp_community_change_update/y2/bgpd.conf

@@ -0,0 +1,18 @@
+router bgp 65003
+  no bgp ebgp-requires-policy
+  neighbor 10.0.3.1 remote-as internal
+  neighbor 10.0.3.1 timers 3 10
+  neighbor 10.0.5.2 remote-as internal
+  neighbor 10.0.5.2 timers 3 10
+  neighbor 10.0.6.2 remote-as external
+  neighbor 10.0.6.2 timers 3 10
+  address-family ipv4 unicast
+    redistribute connected
+    neighbor 10.0.3.1 route-reflector-client
+    neighbor 10.0.5.2 route-reflector-client
+    neighbor 10.0.6.2 route-map z1 in
+  exit-address-family
+!
+route-map z1 permit 10
+  set community 65004:2
+!

tests/topotests/bgp_community_change_update/y2/zebra.conf

@@ -0,0 +1,12 @@
+!
+interface y2-eth0
+ ip address 10.0.3.2/30
+!
+interface y2-eth1
+ ip address 10.0.5.1/30
+!
+interface y2-eth2
+ ip address 10.0.6.1/30
+!
+ip forwarding
+!

tests/topotests/bgp_community_change_update/y3/bgpd.conf

@@ -0,0 +1,18 @@
+router bgp 65003
+  no bgp ebgp-requires-policy
+  neighbor 10.0.4.1 remote-as internal
+  neighbor 10.0.4.1 timers 3 10
+  neighbor 10.0.5.1 remote-as internal
+  neighbor 10.0.5.1 timers 3 10
+  neighbor 10.0.7.2 remote-as external
+  neighbor 10.0.7.2 timers 3 10
+  address-family ipv4 unicast
+    redistribute connected
+    neighbor 10.0.4.1 route-reflector-client
+    neighbor 10.0.5.1 route-reflector-client
+    neighbor 10.0.7.2 route-map z1 in
+  exit-address-family
+!
+route-map z1 permit 10
+  set community 65004:3
+!

tests/topotests/bgp_community_change_update/y3/zebra.conf

@@ -0,0 +1,12 @@
+!
+interface y3-eth0
+ ip address 10.0.4.2/30
+!
+interface y3-eth1
+ ip address 10.0.5.2/30
+!
+interface y3-eth2
+ ip address 10.0.7.1/30
+!
+ip forwarding
+!

tests/topotests/bgp_community_change_update/z1/bgpd.conf

@@ -0,0 +1,10 @@
+router bgp 65004
+  no bgp ebgp-requires-policy
+  neighbor 10.0.6.1 remote-as external
+  neighbor 10.0.6.1 timers 3 10
+  neighbor 10.0.7.1 remote-as external
+  neighbor 10.0.7.1 timers 3 10
+  address-family ipv4 unicast
+    redistribute connected
+  exit-address-family
+!

tests/topotests/bgp_community_change_update/z1/zebra.conf

@@ -0,0 +1,12 @@
+!
+interface lo
+ ip address 192.168.255.254/32
+!
+interface z1-eth0
+ ip address 10.0.6.2/30
+!
+interface z1-eth1
+ ip address 10.0.7.2/30
+!
+ip forwarding
+!

yang/frr-bgp-common.yang

@@ -358,6 +358,13 @@ submodule frr-bgp-common {
         "Apply administrative shutdown to newly configured peers.";
     }
 
+    leaf suppress-duplicates {
+      type boolean;
+      default "true";
+      description
+        "Suppress duplicate updates if the route actually not changed.";
+    }
+
     leaf ebgp-requires-policy {
       type boolean;
       default "true";