4 files changed, 128 insertions, 0 deletions
diff --git a/tests/topotests/bgp_tcp_mss_passive/__init__.py b/tests/topotests/bgp_tcp_mss_passive/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/topotests/bgp_tcp_mss_passive/__init__.py
diff --git a/tests/topotests/bgp_tcp_mss_passive/r1/frr.conf b/tests/topotests/bgp_tcp_mss_passive/r1/frr.conf
new file mode 100644
index 0000000000..a0fcd52a18
--- /dev/null
+++ b/tests/topotests/bgp_tcp_mss_passive/r1/frr.conf
@@ -0,0 +1,12 @@
+!
+interface r1-eth0
+ ip address 192.168.1.1/24
+!
+router bgp 65001
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.2 remote-as external
+ neighbor 192.168.1.2 timers 1 3
+ neighbor 192.168.1.2 timers connect 1
+ neighbor 192.168.1.2 passive
+ neighbor 192.168.1.2 tcp-mss 300
+!
diff --git a/tests/topotests/bgp_tcp_mss_passive/r2/frr.conf b/tests/topotests/bgp_tcp_mss_passive/r2/frr.conf
new file mode 100644
index 0000000000..7213975cc0
--- /dev/null
+++ b/tests/topotests/bgp_tcp_mss_passive/r2/frr.conf
@@ -0,0 +1,10 @@
+!
+interface r2-eth0
+ ip address 192.168.1.2/24
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.1.1 timers 1 3
+ neighbor 192.168.1.1 timers connect 1
+!
diff --git a/tests/topotests/bgp_tcp_mss_passive/test_bgp_tcp_mss_passive.py b/tests/topotests/bgp_tcp_mss_passive/test_bgp_tcp_mss_passive.py
new file mode 100644
index 0000000000..cd405f7b22
--- /dev/null
+++ b/tests/topotests/bgp_tcp_mss_passive/test_bgp_tcp_mss_passive.py
@@ -0,0 +1,106 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+#
+# Copyright (c) 2023 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+
+"""
+Test if TCP MSS is synced with passive neighbor.
+"""
+
+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
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for i, (rname, router) in enumerate(router_list.items(), 1):
+        router.load_frr_config(os.path.join(CWD, "{}/frr.conf".format(rname)))
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_bgp_tcp_mss_passive():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    def _bgp_check_tcp_mss_configured(router, neighbor, mss):
+        output = json.loads(router.vtysh_cmd("show bgp neighbors json"))
+        expected = {
+            neighbor: {
+                "bgpTcpMssConfigured": mss,
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(
+        _bgp_check_tcp_mss_configured, tgen.gears["r1"], "192.168.1.2", 300
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "r1 is not configured with TCP MSS 300"
+
+    test_func = functools.partial(
+        _bgp_check_tcp_mss_configured, tgen.gears["r2"], "192.168.1.1", 0
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "r2 is not configured with the default TCP MSS (1500)"
+
+    def _bgp_check_tcp_mss_synced(router, neighbor, mss):
+        output = json.loads(router.vtysh_cmd("show bgp neighbors json"))
+        expected = {
+            neighbor: {
+                "bgpTcpMssSynced": mss,
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(
+        _bgp_check_tcp_mss_synced, tgen.gears["r1"], "192.168.1.2", 288
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "r1 is not synced with TCP MSS 300"
+
+    test_func = functools.partial(
+        _bgp_check_tcp_mss_synced, tgen.gears["r2"], "192.168.1.1", 288
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "r2 is not synced with the default TCP MSS (1488)"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))