tests: Test neighbor X no-prepend replace-as dual-as

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

tests/topotests/bgp_dual_as/r1/frr.conf

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+!
+interface r1-eth0
+ ip address 10.0.0.1/24
+!
+router bgp 65000
+ no bgp ebgp-requires-policy
+ neighbor 10.0.0.2 remote-as 65002
+ neighbor 10.0.0.2 local-as 65001 no-prepend replace-as dual-as
+ neighbor 10.0.0.2 timers 3 10
+ neighbor 10.0.0.2 timers connect 1
+!

tests/topotests/bgp_dual_as/r2/frr.conf

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+!
+interface r2-eth0
+ ip address 10.0.0.2/24
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 10.0.0.1 remote-as 65001
+ neighbor 10.0.0.1 timers 3 10
+ neighbor 10.0.0.1 timers connect 1
+!

tests/topotests/bgp_dual_as/test_bgp_dual_as.py

@@ -0,0 +1,124 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+#
+# Copyright (c) 2024 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+
+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, get_topogen
+from lib.common_config import step
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    r1 = tgen.add_router("r1")
+    r2 = tgen.add_router("r2")
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(r1)
+    switch.add_link(r2)
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    for _, (rname, router) in enumerate(tgen.routers().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_dual_as():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+    r2 = tgen.gears["r2"]
+
+    def _bgp_converge_65001():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 summary json"))
+        expected = {
+            "ipv4Unicast": {
+                "as": 65000,
+                "peers": {
+                    "10.0.0.2": {
+                        "hostname": "r2",
+                        "remoteAs": 65002,
+                        "localAs": 65001,
+                        "state": "Established",
+                        "peerState": "OK",
+                    }
+                },
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_converge_65001)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Can't establish BGP session using local-as AS 65001"
+
+    step("Change remote-as from r2 to use global AS 65000")
+    r2.vtysh_cmd(
+        """
+    configure terminal
+     router bgp
+      neighbor 10.0.0.1 remote-as 65000
+    """
+    )
+
+    def _bgp_converge_65000():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 summary json"))
+        expected = {
+            "ipv4Unicast": {
+                "as": 65000,
+                "peers": {
+                    "10.0.0.2": {
+                        "hostname": "r2",
+                        "remoteAs": 65002,
+                        "localAs": 65000,
+                        "state": "Established",
+                        "peerState": "OK",
+                    }
+                },
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_converge_65000)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Can't establish BGP session using global AS 65000"
+
+
+def test_memory_leak():
+    "Run the memory leak test and report results."
+    tgen = get_topogen()
+    if not tgen.is_memleak_enabled():
+        pytest.skip("Memory leak test/report is disabled")
+
+    tgen.report_memory_leaks()
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))