tests: Check if Paths-Limit capability works

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

tests/topotests/bgp_addpath_paths_limit/r1/frr.conf

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+!
+int r1-eth0
+ ip address 192.168.1.1/24
+!
+router bgp 65001
+ timers bgp 3 10
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.2 remote-as external
+ neighbor 192.168.1.2 timers connect 5
+ address-family ipv4 unicast
+  neighbor 192.168.1.2 addpath-rx-paths-limit 2
+ exit-address-family
+!

tests/topotests/bgp_addpath_paths_limit/r2/frr.conf

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+!
+int r2-eth0
+ ip address 192.168.1.2/24
+!
+int r2-eth1
+ ip address 192.168.2.2/24
+!
+int r2-eth2
+ ip address 192.168.7.2/24
+!
+router bgp 65002
+ timers bgp 3 10
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.7.7 remote-as external
+ neighbor 192.168.7.7 timers connect 5
+ neighbor 192.168.2.3 remote-as external
+ neighbor 192.168.2.3 timers connect 5
+ neighbor 192.168.2.3 weight 3
+ neighbor 192.168.2.4 remote-as external
+ neighbor 192.168.2.4 timers connect 5
+ neighbor 192.168.2.4 weight 4
+ neighbor 192.168.2.5 remote-as external
+ neighbor 192.168.2.5 timers connect 5
+ neighbor 192.168.2.5 weight 5
+ neighbor 192.168.2.6 remote-as external
+ neighbor 192.168.2.6 timers connect 5
+ neighbor 192.168.2.6 weight 6
+ address-family ipv4 unicast
+  neighbor 192.168.1.1 addpath-tx-all-paths
+  neighbor 192.168.1.1 prefix-list announce out
+  neighbor 192.168.7.7 addpath-tx-all-paths
+  neighbor 192.168.7.7 prefix-list announce out
+ exit-address-family
+!
+ip prefix-list announce seq 5 permit 172.16.16.254/32
+!

tests/topotests/bgp_addpath_paths_limit/r3/frr.conf

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+!
+int lo
+ ip address 172.16.16.254/32
+!
+int r3-eth0
+ ip address 192.168.2.3/24
+!
+router bgp 65003
+ timers bgp 3 10
+ no bgp ebgp-requires-policy
+ neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers connect 5
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_addpath_paths_limit/r4/frr.conf

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+!
+int lo
+ ip address 172.16.16.254/32
+!
+int r4-eth0
+ ip address 192.168.2.4/24
+!
+router bgp 65004
+ timers bgp 3 10
+ no bgp ebgp-requires-policy
+ neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers connect 5
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_addpath_paths_limit/r5/frr.conf

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+!
+int lo
+ ip address 172.16.16.254/32
+!
+int r5-eth0
+ ip address 192.168.2.5/24
+!
+router bgp 65005
+ timers bgp 3 10
+ no bgp ebgp-requires-policy
+ neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers connect 5
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_addpath_paths_limit/r6/frr.conf

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+!
+int lo
+ ip address 172.16.16.254/32
+!
+int r6-eth0
+ ip address 192.168.2.6/24
+!
+router bgp 65006
+ timers bgp 3 10
+ no bgp ebgp-requires-policy
+ neighbor 192.168.2.2 remote-as external
+ neighbor 192.168.2.2 timers connect 5
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_addpath_paths_limit/r7/frr.conf

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+!
+int r7-eth0
+ ip address 192.168.7.7/24
+!
+router bgp 65007
+ timers bgp 3 10
+ no bgp ebgp-requires-policy
+ neighbor 192.168.7.2 remote-as external
+ neighbor 192.168.7.2 timers connect 5
+ address-family ipv4 unicast
+  neighbor 192.168.7.2 addpath-rx-paths-limit 3
+ exit-address-family
+!

tests/topotests/bgp_addpath_paths_limit/test_bgp_addpath_paths_limit.py

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+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+# Copyright (c) 2024 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+
+"""
+Test if Paths-Limit capability works as expected.
+"""
+
+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, 8):
+        tgen.add_router("r{}".format(routern))
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
+    switch.add_link(tgen.gears["r5"])
+    switch.add_link(tgen.gears["r6"])
+
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r7"])
+    switch.add_link(tgen.gears["r2"])
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for _, (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_addpath_paths_limit():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+    r2 = tgen.gears["r2"]
+    r7 = tgen.gears["r7"]
+
+    def _bgp_converge():
+        output = json.loads(r2.vtysh_cmd("show bgp neighbor json"))
+        expected = {
+            "192.168.7.7": {
+                "neighborCapabilities": {
+                    "pathsLimit": {
+                        "ipv4Unicast": {
+                            "advertisedAndReceived": True,
+                            "advertisedPathsLimit": 0,
+                            "receivedPathsLimit": 3,
+                        }
+                    }
+                }
+            },
+            "192.168.1.1": {
+                "neighborCapabilities": {
+                    "pathsLimit": {
+                        "ipv4Unicast": {
+                            "advertisedAndReceived": True,
+                            "advertisedPathsLimit": 0,
+                            "receivedPathsLimit": 2,
+                        }
+                    }
+                }
+            },
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_bgp_converge)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Can't converge initially"
+
+    def _bgp_check_received_routes(router, expected):
+        output = json.loads(
+            router.vtysh_cmd("show bgp ipv4 unicast 172.16.16.254/32 json")
+        )
+
+        if "paths" not in output:
+            return "No paths received"
+
+        return topotest.json_cmp(len(output["paths"]), expected)
+
+    test_func = functools.partial(_bgp_check_received_routes, r1, 2)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Received routes count is not as expected"
+
+    test_func = functools.partial(_bgp_check_received_routes, r7, 3)
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Received routes count is not as expected"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))