Commit 8db966ac21 for frr
commit 8db966ac2187aedf14a8b825be97682db14feaed
Author: Nageswara Soma <nsoma@cisco.com>
Date: Tue Oct 13 17:27:14 2026 -0700
tests: Add BFD peering address move topotest
Move an IPv4 peering subnet carrying IPv6 unicast
from one link to another while the BGP session stays
up. Verify that the BFD session follows it to the
new interface and that the remote peer learns the
new global and link-local IPv6 next hops, without a
BGP reset.
r2 runs no BFD, so r1's session stays down and BFD
cannot reset BGP. Only the connected address
refresh in bgpd can move the session to the new
interface.
Signed-off-by: Nageswara Soma <nsoma@cisco.com>
diff --git a/tests/topotests/bgp_bfd_address_move/r1/frr.conf b/tests/topotests/bgp_bfd_address_move/r1/frr.conf
new file mode 100644
index 0000000000..6d964505d2
--- /dev/null
+++ b/tests/topotests/bgp_bfd_address_move/r1/frr.conf
@@ -0,0 +1,11 @@
+router bgp 65001
+ bgp router-id 192.0.2.1
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor 10.0.0.2 remote-as 65002
+ neighbor 10.0.0.2 bfd
+ address-family ipv6 unicast
+ network 2001:db8:100::/64
+ neighbor 10.0.0.2 activate
+ exit-address-family
+!
diff --git a/tests/topotests/bgp_bfd_address_move/r2/frr.conf b/tests/topotests/bgp_bfd_address_move/r2/frr.conf
new file mode 100644
index 0000000000..f021f669bc
--- /dev/null
+++ b/tests/topotests/bgp_bfd_address_move/r2/frr.conf
@@ -0,0 +1,8 @@
+router bgp 65002
+ bgp router-id 192.0.2.2
+ no bgp ebgp-requires-policy
+ neighbor 10.0.0.1 remote-as 65001
+ address-family ipv6 unicast
+ neighbor 10.0.0.1 activate
+ exit-address-family
+!
diff --git a/tests/topotests/bgp_bfd_address_move/test_bgp_bfd_address_move.py b/tests/topotests/bgp_bfd_address_move/test_bgp_bfd_address_move.py
new file mode 100644
index 0000000000..c2cbf975ae
--- /dev/null
+++ b/tests/topotests/bgp_bfd_address_move/test_bgp_bfd_address_move.py
@@ -0,0 +1,166 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+# Copyright (c) 2026 by
+# Nageswara Soma <nsoma@cisco.com>
+
+"""Verify BFD and the advertised next hop follow a moved peering subnet."""
+
+import json
+import os
+import sys
+from functools import partial
+
+import pytest
+
+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, get_topogen
+
+pytestmark = [pytest.mark.bfdd, pytest.mark.bgpd]
+
+PEER = "10.0.0.2"
+PREFIX = "2001:db8:100::/64"
+
+
+def build_topo(tgen):
+ r1 = tgen.add_router("r1")
+ r2 = tgen.add_router("r2")
+
+ switch = tgen.add_switch("s1")
+ switch.add_link(r1, nodeif="r1-eth0")
+ switch.add_link(r2, nodeif="r2-eth0")
+
+ switch = tgen.add_switch("s2")
+ switch.add_link(r1, nodeif="r1-eth1")
+ switch.add_link(r2, nodeif="r2-eth1")
+
+
+def setup_module(mod):
+ tgen = Topogen(build_topo, mod.__name__)
+ tgen.start_topology()
+
+ for router in tgen.routers().values():
+ router.load_frr_config()
+
+ tgen.start_router()
+
+ for index, router in enumerate(tgen.routers().values(), start=1):
+ router.run("sysctl -w net.ipv6.conf.all.accept_dad=0")
+ for link, interface in enumerate(("eth0", "eth1"), start=1):
+ ifname = "{}-{}".format(router.name, interface)
+ router.run("sysctl -w net.ipv6.conf.{}.accept_dad=0".format(ifname))
+ router.run(
+ "ip -6 address replace 2001:db8:{}::{}/64 dev {}".format(
+ link, index, ifname
+ )
+ )
+ router.run(
+ "ip address replace 10.0.0.{}/24 dev {}-eth0".format(index, router.name)
+ )
+
+
+def teardown_module(_mod):
+ get_topogen().stop_topology()
+
+
+def get_neighbor(router):
+ neighbors = router.vtysh_cmd("show bgp neighbors {} json".format(PEER), isjson=True)
+ return neighbors.get(PEER, {})
+
+
+def check_established(router):
+ return topotest.json_cmp(get_neighbor(router), {"bgpState": "Established"})
+
+
+def check_bfd_interface(router, interface):
+ peers = router.vtysh_cmd("show bfd peers json", isjson=True)
+ for entry in peers:
+ if entry.get("peer") == PEER:
+ if entry.get("interface") == interface:
+ return None
+ return "BFD peer expected interface={}, observed {}".format(
+ interface, entry
+ )
+ return "BFD peer {} not found: {}".format(PEER, peers)
+
+
+def get_link_local(router, interface):
+ output = router.run("ip -6 -j address show dev {} scope link".format(interface))
+ for entry in json.loads(output):
+ for addr in entry.get("addr_info", []):
+ if "local" in addr:
+ return addr["local"]
+ assert False, "no link-local address on {}: {}".format(interface, output)
+
+
+def check_nexthops(router, global_nh, link_local):
+ output = router.vtysh_cmd(
+ "show bgp ipv6 unicast {} json".format(PREFIX), isjson=True
+ )
+ expected = {
+ "paths": [
+ {
+ "nexthops": [
+ {"ip": global_nh, "scope": "global"},
+ {"ip": link_local, "scope": "link-local"},
+ ]
+ }
+ ]
+ }
+ return topotest.json_cmp(output, expected)
+
+
+def test_bfd_follows_address_move_without_reset():
+ tgen = get_topogen()
+ if tgen.routers_have_failure():
+ pytest.skip(tgen.errors)
+
+ r1 = tgen.gears["r1"]
+ r2 = tgen.gears["r2"]
+
+ # r2 runs no BFD, so r1's session stays down and cannot reset BGP.
+ test_func = partial(check_established, r1)
+ _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+ assert result is None, result
+
+ test_func = partial(check_bfd_interface, r1, "r1-eth0")
+ _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+ assert result is None, result
+
+ test_func = partial(
+ check_nexthops, r2, "2001:db8:1::1", get_link_local(r1, "r1-eth0")
+ )
+ _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+ assert result is None, result
+
+ dropped = get_neighbor(r1)["connectionsDropped"]
+
+ r1.run("ip address add 10.0.0.1/24 dev r1-eth1")
+ r2.run("ip address add 10.0.0.2/24 dev r2-eth1")
+ r1.run("ip address del 10.0.0.1/24 dev r1-eth0")
+ r2.run("ip address del 10.0.0.2/24 dev r2-eth0")
+
+ test_func = partial(check_bfd_interface, r1, "r1-eth1")
+ _, result = topotest.run_and_expect(test_func, None, count=15, wait=1)
+ assert result is None, result
+
+ test_func = partial(
+ check_nexthops, r2, "2001:db8:2::1", get_link_local(r1, "r1-eth1")
+ )
+ _, result = topotest.run_and_expect(test_func, None, count=15, wait=1)
+ assert result is None, result
+
+ neighbor = get_neighbor(r1)
+ assert neighbor.get("bgpState") == "Established", neighbor.get("bgpState")
+ assert neighbor["connectionsDropped"] == dropped, "BGP session reset: {}".format(
+ neighbor.get("lastResetDueTo")
+ )
+
+
+if __name__ == "__main__":
+ args = ["-s"] + sys.argv[1:]
+ sys.exit(pytest.main(args))