tests: Add new test for static routes with multiple nexthops

tests/topotests/static_routing_nexthop/__init__.py

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+#test

tests/topotests/static_routing_nexthop/r1/baseline_configuration.json

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+{
+  "30.0.0.0/28":[
+    {
+      "prefix":"30.0.0.0/28",
+      "prefixLen":28,
+      "protocol":"static",
+      "nexthops":[
+        {
+          "fib":true,
+          "ip":"192.168.2.2",
+          "afi":"ipv4",
+          "active":true,
+          "weight":1
+        },
+        {
+          "fib":true,
+          "ip":"192.168.3.2",
+          "afi":"ipv4",
+          "active":true,
+          "weight":1
+        },
+        {
+          "fib":true,
+          "ip":"192.168.4.2",
+          "afi":"ipv4",
+          "active":true,
+          "weight":1
+        }
+      ]
+    }
+  ],
+  "192.168.0.0/16":[
+    {
+      "prefix":"192.168.0.0/16",
+      "prefixLen":16,
+      "protocol":"static",
+      "nexthops":[
+        {
+          "unreachable":true,
+          "blackhole":true,
+          "active":true,
+          "weight":1
+        }
+      ]
+    }
+  ]
+}

tests/topotests/static_routing_nexthop/r1/baseline_kernel_routes.txt

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+30.0.0.0/28 proto 196 metric 20
+        nexthop via 192.168.2.2 dev r1-eth0 weight 1
+        nexthop via 192.168.3.2 dev r1-eth1 weight 1
+        nexthop via 192.168.4.2 dev r1-eth2 weight 1
+blackhole 192.168.0.0/16 proto 196 metric 20
+192.168.2.0/24 dev r1-eth0 proto kernel scope link src 192.168.2.1
+192.168.3.0/24 dev r1-eth1 proto kernel scope link src 192.168.3.1
+192.168.4.0/24 dev r1-eth2 proto kernel scope link src 192.168.4.1

tests/topotests/static_routing_nexthop/r1/eth0_down_kernel_routes.txt

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+30.0.0.0/28 proto 196 metric 20
+        nexthop via 192.168.3.2 dev r1-eth1 weight 1
+        nexthop via 192.168.4.2 dev r1-eth2 weight 1
+blackhole 192.168.0.0/16 proto 196 metric 20
+192.168.2.0/24 dev r1-eth0 proto kernel scope link src 192.168.2.1 linkdown
+192.168.3.0/24 dev r1-eth1 proto kernel scope link src 192.168.3.1
+192.168.4.0/24 dev r1-eth2 proto kernel scope link src 192.168.4.1

tests/topotests/static_routing_nexthop/r1/frr.conf

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+!
+int r1-eth0
+ ip address 192.168.2.1/24
+!
+int r1-eth1
+ ip address 192.168.3.1/24
+!
+int r1-eth2
+ ip address 192.168.4.1/24
+!
+ip route 192.168.0.0/16 Null0
+ip route 30.0.0.1/28 192.168.2.2
+ip route 30.0.0.1/28 192.168.3.2
+ip route 30.0.0.1/28 192.168.4.2
+

tests/topotests/static_routing_nexthop/r2/frr.conf

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+!
+int r2-eth0
+ ip address 192.168.2.1/24
+!
+

tests/topotests/static_routing_nexthop/r3/frr.conf

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+!
+int r3-eth0
+ ip address 192.168.3.1/24
+!
+

tests/topotests/static_routing_nexthop/r4/frr.conf

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+!
+int r4-eth0
+ ip address 192.168.4.1/24
+!
+

tests/topotests/static_routing_nexthop/test_static_routing_nexthop.py

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+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+# Copyright (c) 2023 by
+# Abhishek Naik <[email protected]>
+#
+
+"""
+Test static route resolution over recursive nexthop
+"""
+
+import os
+import re
+import sys
+import json
+import pytest
+import functools
+
+pytestmark = pytest.mark.staticd
+
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+
+from lib import topotest
+from lib.topogen import Topogen, TopoRouter, get_topogen
+from lib.common_config import step
+
+
+def build_topo(tgen):
+    for router in range(1, 5):
+        tgen.add_router("r{}".format(router))
+
+    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["r1"])
+    switch.add_link(tgen.gears["r3"])
+
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r4"])
+
+
+@pytest.fixture(scope="module")
+def tgen(request):
+    "Setup/Teardown the environment and provide tgen argument to tests"
+
+    tgen = Topogen(build_topo, request.module.__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()
+    yield tgen
+    tgen.stop_topology()
+
+
+def test_static_routing_multipath_nexthops(tgen):
+    """
+    This test adds a static route with multiple nexthops.
+    Each nexthop resolves over a directly connected route configured on an interface
+    When one of the interfaces goes down, that nexthop gateway resolves over a blackhole aggregate
+    route.
+    This should result in that nexthop being withdrawn from the kernel, resulting in one fewer nexthop.
+    """
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+
+    def _verify_multipath_static_configuration():
+        output = json.loads(r1.vtysh_cmd("show ip route static json"))
+        reffile = os.path.join(CWD, "r1/baseline_configuration.json")
+        with open(reffile) as json_data:
+            file_contents = json_data.read()
+        expected = json.loads(file_contents)
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(_verify_multipath_static_configuration)
+
+    _, result = topotest.run_and_expect(test_func, None, count=1, wait=5)
+    assert result is None, "Baseline configuration failed"
+
+    def _verify_multipath_kernel_routes():
+        actual = r1.run("ip route show")
+        output = "\n".join(line.strip() for line in actual.splitlines())
+
+        reffile = os.path.join(CWD, "r1/baseline_kernel_routes.txt")
+        file_op = open(reffile).read().rstrip()
+        expected = "\n".join(line.strip() for line in actual.splitlines())
+
+        return topotest.get_textdiff(
+            output,
+            expected,
+            title1="Actual ip route show",
+            title2="Expected ip route show",
+        )
+
+    ok, result = topotest.run_and_expect(
+        _verify_multipath_kernel_routes, "", count=1, wait=5
+    )
+    assert ok, result
+
+    def _link_down_and_verify_multipath_kernel_routes():
+        r1.peer_link_enable("r1-eth0", False)
+
+        actual = r1.run("ip route show")
+        output = "\n".join(line.strip() for line in actual.splitlines())
+
+        reffile = os.path.join(CWD, "r1/eth0_down_kernel_routes.txt")
+        file_op = open(reffile).read().rstrip()
+        expected = "\n".join(line.strip() for line in actual.splitlines())
+        return topotest.get_textdiff(
+            output,
+            expected,
+            title1="Actual ip route show",
+            title2="Expected ip route show",
+        )
+
+    ok, result = topotest.run_and_expect(
+        _link_down_and_verify_multipath_kernel_routes, "", count=1, wait=5
+    )
+    assert ok, result