tests: Check if underlay IGP metric is reflected into BGP after cost changes

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

tests/topotests/bgp_set_metric_igp/r1/frr.conf

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+!
+int r1-eth0
+ ip address 10.0.0.1/24
+!
+int r1-eth1
+ ip address 10.0.1.1/24
+!
+router bgp 65001
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor 10.0.0.2 remote-as external
+ neighbor 10.0.1.2 remote-as external
+!

tests/topotests/bgp_set_metric_igp/r2/frr.conf

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+!
+int r2-eth0
+ ip address 10.0.0.2/24
+ ip router isis n2
+ isis circuit-type level-2-only
+ isis fast-reroute lfa level-2
+ isis network point-to-point
+ isis hello-interval 1
+ isis hello-multiplier 10
+!
+int r2-eth1
+ ip address 10.0.2.1/24
+ ip router isis n2
+ isis circuit-type level-2-only
+ isis fast-reroute lfa level-2
+ isis network point-to-point
+ isis hello-interval 1
+ isis hello-multiplier 10
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 10.0.0.1 remote-as external
+ neighbor 10.0.2.2 remote-as internal
+ address-family ipv4 unicast
+  neighbor 10.0.0.1 route-map igp out
+ exit-address-family
+!
+router isis n2
+ is-type level-2-only
+ net 49.0001.0000.0000.0002.00
+ lsp-mtu 1440
+exit
+!
+route-map igp permit 10
+ set metric igp
+exit

tests/topotests/bgp_set_metric_igp/r3/frr.conf

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+!
+int r3-eth0
+ ip address 10.0.1.2/24
+ ip router isis n3
+ isis circuit-type level-2-only
+ isis fast-reroute lfa level-2
+ isis network point-to-point
+ isis hello-interval 1
+ isis hello-multiplier 10
+!
+int r3-eth1
+ ip address 10.0.3.1/24
+ ip router isis n3
+ isis circuit-type level-2-only
+ isis fast-reroute lfa level-2
+ isis metric level-1 10
+ isis metric level-2 100
+ isis network point-to-point
+ isis hello-interval 1
+ isis hello-multiplier 10
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 10.0.1.1 remote-as external
+ neighbor 10.0.3.2 remote-as internal
+ address-family ipv4 unicast
+  neighbor 10.0.1.1 route-map igp out
+ exit-address-family
+!
+router isis n3
+ is-type level-2-only
+ net 49.0001.0000.0000.0003.00
+ lsp-mtu 1440
+exit
+!
+route-map igp permit 10
+ set metric igp
+exit

tests/topotests/bgp_set_metric_igp/r4/frr.conf

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+!
+int r4-eth0
+ ip address 10.0.2.2/24
+ ip router isis n4
+ isis circuit-type level-2-only
+ isis fast-reroute lfa level-2
+ isis network point-to-point
+ isis hello-interval 1
+ isis hello-multiplier 10
+!
+int r4-eth1
+ ip address 10.0.3.2/24
+ ip router isis n4
+ isis circuit-type level-2-only
+ isis fast-reroute lfa level-2
+ isis metric level-1 10
+ isis metric level-2 100
+ isis network point-to-point
+ isis hello-interval 1
+ isis hello-multiplier 10
+!
+int r4-eth2
+ ip address 10.0.4.1/24
+ ip router isis n4
+ isis circuit-type level-2-only
+ isis fast-reroute lfa level-2
+ isis network point-to-point
+ isis hello-interval 1
+ isis hello-multiplier 10
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 10.0.2.1 remote-as internal
+ neighbor 10.0.3.1 remote-as internal
+ neighbor 10.0.4.2 remote-as external
+!
+router isis n4
+ is-type level-2-only
+ net 49.0001.0000.0000.0004.00
+ lsp-mtu 1440
+exit

tests/topotests/bgp_set_metric_igp/r5/frr.conf

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+!
+int r5-eth0
+ ip address 10.0.4.2/24
+!
+router bgp 65005
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor 10.0.4.1 remote-as external
+ neighbor 10.0.4.1 timers 1 3
+ neighbor 10.0.4.1 timers connect 1
+ address-family ipv4 unicast
+  network 10.5.5.5/32
+ exit-address-family
+!

tests/topotests/bgp_set_metric_igp/test_bgp_set_metric_igp.py

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+#!/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
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def setup_module(mod):
+    topodef = {
+        "s1": ("r1", "r2"),
+        "s2": ("r1", "r3"),
+        "s3": ("r2", "r4"),
+        "s4": ("r3", "r4"),
+        "s5": ("r4", "r5"),
+    }
+    tgen = Topogen(topodef, 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_set_metric_igp():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+    r2 = tgen.gears["r2"]
+
+    def _bgp_converge():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 unicast json"))
+        expected = {
+            "routes": {
+                "10.5.5.5/32": [
+                    {
+                        "valid": True,
+                        "bestpath": True,
+                        "selectionReason": "MED",
+                        "metric": 20,
+                        "nexthops": [
+                            {
+                                "ip": "10.0.0.2",
+                                "hostname": "r2",
+                            }
+                        ],
+                    },
+                    {
+                        "valid": True,
+                        "bestpath": None,
+                        "metric": 110,
+                        "nexthops": [
+                            {
+                                "ip": "10.0.1.2",
+                                "hostname": "r3",
+                            }
+                        ],
+                    },
+                ]
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(
+        _bgp_converge,
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=120, wait=5)
+    assert result is None, "10.5.5.5/32 best path is not via r2 (MED == 20)"
+
+    r2.vtysh_cmd(
+        """
+configure terminal
+interface r2-eth1
+ isis metric level-2 6000
+"""
+    )
+
+    def _bgp_converge_after_isis_metric_changes():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 unicast json"))
+        expected = {
+            "routes": {
+                "10.5.5.5/32": [
+                    {
+                        "valid": True,
+                        "bestpath": None,
+                        "metric": 6010,
+                        "nexthops": [
+                            {
+                                "ip": "10.0.0.2",
+                                "hostname": "r2",
+                            }
+                        ],
+                    },
+                    {
+                        "valid": True,
+                        "bestpath": True,
+                        "selectionReason": "MED",
+                        "metric": 110,
+                        "nexthops": [
+                            {
+                                "ip": "10.0.1.2",
+                                "hostname": "r3",
+                            }
+                        ],
+                    },
+                ]
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(
+        _bgp_converge_after_isis_metric_changes,
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=120, wait=5)
+    assert result is None, "10.5.5.5/32 best path is not via r3 (MED == 110)"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))