tests: Add basic BGP Long-lived Graceful restart tests

Signed-off-by: Donatas Abraitis <donatas.abraitis@gmail.com>

tests/topotests/bgp_llgr/r0/bgpd.conf

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+router bgp 65000
+ no bgp ebgp-requires-policy
+ bgp graceful-restart
+ bgp graceful-restart restart-time 1
+ bgp long-lived-graceful-restart stale-time 20
+ neighbor 192.168.0.2 remote-as external
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_llgr/r0/zebra.conf

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+!
+int lo
+ ip address 172.16.1.1/32
+!
+int r0-eth0
+ ip address 192.168.0.1/24
+!

tests/topotests/bgp_llgr/r1/bgpd.conf

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+router bgp 65001
+ no bgp ebgp-requires-policy
+ bgp graceful-restart
+ bgp graceful-restart restart-time 1
+ bgp long-lived-graceful-restart stale-time 20
+ neighbor 192.168.1.2 remote-as external
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_llgr/r1/zebra.conf

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+!
+int lo
+ ip address 172.16.1.1/32
+!
+int r1-eth0
+ ip address 192.168.1.1/24
+!

tests/topotests/bgp_llgr/r2/bgpd.conf

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+router bgp 65002
+ no bgp ebgp-requires-policy
+ bgp graceful-restart
+ bgp long-lived-graceful-restart stale-time 20
+ neighbor 192.168.0.1 remote-as external
+ neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.2.1 remote-as external
+ address-family ipv4 unicast
+   neighbor 192.168.1.1 weight 100

tests/topotests/bgp_llgr/r2/zebra.conf

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+!
+int r2-eth0
+ ip address 192.168.0.2/24
+!
+int r2-eth1
+ ip address 192.168.1.2/24
+!
+int r2-eth2
+ ip address 192.168.2.2/24
+!

tests/topotests/bgp_llgr/r3/bgpd.conf

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+router bgp 65003
+ bgp router-id 192.168.2.1
+ no bgp ebgp-requires-policy
+ bgp graceful-restart
+ bgp long-lived-graceful-restart stale-time 20
+ neighbor 192.168.2.2 remote-as external

tests/topotests/bgp_llgr/r3/zebra.conf

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+!
+int r3-eth0
+ ip address 192.168.2.1/24
+!

tests/topotests/bgp_llgr/test_bgp_llgr.py

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+#!/usr/bin/env python
+
+# Copyright (c) 2021 by
+# Donatas Abraitis <donatas.abraitis@gmail.com>
+#
+# Permission to use, copy, modify, and/or distribute this software
+# for any purpose with or without fee is hereby granted, provided
+# that the above copyright notice and this permission notice appear
+# in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND NETDEF DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NETDEF BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+#
+
+"""
+Test if BGP Long-lived Graceful Restart capability works:
+    Check if we can see 172.16.1.1/32 after initial converge in R3.
+    Check if we can see 172.16.1.1/32 as best selected due to higher weigth in R2.
+    Kill bgpd in R1.
+    Check if we can see 172.16.1.1/32 as stale in R2.
+    Check if we can see 172.16.1.1/32 depreferenced due to LLGR_STALE in R2.
+    Check if we can see 172.16.1.1/32 after R1 was killed in R3.
+"""
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+pytestmark = [pytest.mark.bgpd]
+
+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
+
+from lib.common_config import (
+    kill_router_daemons,
+    start_router_daemons,
+    step,
+)
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    for routern in range(0, 5):
+        tgen.add_router("r{}".format(routern))
+
+    switch = tgen.add_switch("s0")
+    switch.add_link(tgen.gears["r0"])
+    switch.add_link(tgen.gears["r2"])
+
+    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"])
+
+
+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_config(
+            TopoRouter.RD_ZEBRA, os.path.join(CWD, "{}/zebra.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_BGP, os.path.join(CWD, "{}/bgpd.conf".format(rname))
+        )
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_bgp_llgr():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r2 = tgen.gears["r2"]
+    r3 = tgen.gears["r3"]
+
+    def _bgp_converge(router):
+        output = json.loads(router.vtysh_cmd("show ip bgp json"))
+        expected = {
+            "routes": {
+                "172.16.1.1/32": [{"nexthops": [{"ip": "192.168.2.2", "used": True}]}]
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    step("Check if we can see 172.16.1.1/32 after initial converge in R3")
+    test_func = functools.partial(_bgp_converge, r3)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Cannot see 172.16.1.1/32 in r3"
+
+    def _bgp_weight_prefered_route(router):
+        output = json.loads(router.vtysh_cmd("show ip bgp 172.16.1.1/32 json"))
+        expected = {
+            "paths": [
+                {
+                    "bestpath": {"selectionReason": "Weight"},
+                    "nexthops": [
+                        {
+                            "ip": "192.168.1.1",
+                        }
+                    ],
+                }
+            ]
+        }
+        return topotest.json_cmp(output, expected)
+
+    step(
+        "Check if we can see 172.16.1.1/32 as best selected due to higher weigth in R2"
+    )
+    test_func = functools.partial(_bgp_weight_prefered_route, r2)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert (
+        result is None
+    ), "Prefix 172.16.1.1/32 is not selected as bests path due to weight"
+
+    step("Kill bgpd in R1")
+    kill_router_daemons(tgen, "r1", ["bgpd"])
+
+    def _bgp_stale_route(router):
+        output = json.loads(router.vtysh_cmd("show ip bgp 172.16.1.1/32 json"))
+        expected = {"paths": [{"community": {"string": "llgr-stale"}, "stale": True}]}
+        return topotest.json_cmp(output, expected)
+
+    step("Check if we can see 172.16.1.1/32 as stale in R2")
+    test_func = functools.partial(_bgp_stale_route, r2)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Prefix 172.16.1.1/32 is not stale"
+
+    def _bgp_llgr_depreference_route(router):
+        output = json.loads(router.vtysh_cmd("show ip bgp 172.16.1.1/32 json"))
+        expected = {
+            "paths": [
+                {
+                    "bestpath": {"selectionReason": "First path received"},
+                    "nexthops": [
+                        {
+                            "ip": "192.168.0.1",
+                        }
+                    ],
+                }
+            ]
+        }
+        return topotest.json_cmp(output, expected)
+
+    step("Check if we can see 172.16.1.1/32 depreferenced due to LLGR_STALE in R2")
+    test_func = functools.partial(_bgp_llgr_depreference_route, r2)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Prefix 172.16.1.1/32 is not depreferenced due to LLGR_STALE"
+
+    step("Check if we can see 172.16.1.1/32 after R1 was killed in R3")
+    test_func = functools.partial(_bgp_converge, r3)
+    success, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Cannot see 172.16.1.1/32 in r3"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))