tests: Add a very basic dump bgp PATH.. topotest

None of the bgp dump code was even tested.  Add a bit
of basic stuff that it at least generates a dump file.
This can be extended at a future time.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

tests/topotests/dump_of_bgp/r1/frr.conf

@@ -0,0 +1,12 @@
+!
+int r1-eth0
+ ip address 192.168.1.1/24
+!
+router bgp 65001
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.2 remote-as external
+ neighbor 192.168.1.2 timers 1 3
+ neighbor 192.168.1.2 timers connect 1
+ neighbor 192.168.1.2 capability dynamic
+ !
+!

tests/topotests/dump_of_bgp/r2/frr.conf

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+!
+int lo
+ ip address 10.10.10.10/32
+!
+int r2-eth0
+ ip address 192.168.1.2/24
+!
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 192.168.1.1 remote-as external
+ neighbor 192.168.1.1 timers 1 3
+ neighbor 192.168.1.1 timers connect 1
+ !
+ address-family ipv4 unicast
+  redistribute connected
+ exit-address-family
+!

tests/topotests/dump_of_bgp/test_dump_of_bgp.py

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+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+# Copyright (c) 2024 by Nvidia Corporation
+# Donald Sharp <sharpd@nvidia.com>
+
+import os
+import sys
+import json
+import pytest
+import functools
+from lib.topolog import logger
+
+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, get_topogen
+
+
+def setup_module(mod):
+    topodef = {"s1": ("r1", "r2")}
+    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_dump():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    logger.info("Test the ability for bgp to dump a file specified")
+    r1 = tgen.gears["r1"]
+
+    logger.info("Converge BGP")
+    def _converge():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 unicast 10.10.10.10/32 json"))
+        expected = {
+            "paths": [
+                {
+                    "valid": True,
+                    "nexthops": [
+                        {
+                            "hostname": "r2",
+                            "accessible": True,
+                        }
+                    ],
+                }
+            ]
+        }
+        return topotest.json_cmp(output, expected)
+
+    test_func = functools.partial(
+        _converge,
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=30, wait=1)
+    assert result is None, "Can't converge"
+
+    logger.info("Dumping file")
+    ####
+    # Create a dump file
+    ####
+    r1.vtysh_cmd(
+        """
+    configure terminal
+    dump bgp all bgp_dump.file
+    """
+    )
+
+    def _test_dump_file_existence():
+        dump_file = "{}/r1/bgp_dump.file".format(tgen.logdir)
+
+        logger.info("Looking for {} file".format(dump_file))
+        logger.info(os.path.isfile(dump_file))
+        return os.path.isfile(dump_file)
+
+    logger.info("Ensure that Log file exists")
+    _, result = topotest.run_and_expect(_test_dump_file_existence, True, count=30, wait = 3)
+    assert result is True
+
+    # At this point all we have done is ensure that the dump file
+    # is generated for r1.  What is correctness of the dump anyways?
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))