topotests: add topotest to check bgp lu explicit-null service

The test ensures that the incoming prefixes are received with
the appropriate label value, and that connectivity is ensured
between prefixes.

Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>

tests/topotests/bgp_lu_explicitnull/r1/bgpd.conf

@@ -0,0 +1,15 @@
+router bgp 65500
+ bgp router-id 192.0.2.1
+ no bgp ebgp-requires-policy
+ bgp labeled-unicast explicit-null
+ neighbor 192.0.2.2 remote-as 65501
+!
+ address-family ipv4 unicast
+  no neighbor 192.0.2.2 activate
+  network 192.168.2.1/32
+ exit-address-family
+ !
+ address-family ipv4 labeled-unicast
+  neighbor 192.0.2.2 activate
+ exit-address-family
+!

tests/topotests/bgp_lu_explicitnull/r1/zebra.conf

@@ -0,0 +1,6 @@
+interface r1-eth0
+ ip address 192.0.2.1/24
+!
+interface r1-eth1
+ ip address 192.168.2.1/32
+!

tests/topotests/bgp_lu_explicitnull/r2/bgpd.conf

@@ -0,0 +1,15 @@
+router bgp 65501
+ bgp router-id 192.0.2.2
+ no bgp ebgp-requires-policy
+ bgp labeled-unicast explicit-null
+ neighbor 192.0.2.1 remote-as 65500
+!
+ address-family ipv4 unicast
+  no neighbor 192.0.2.1 activate
+  network 192.168.2.2/32
+ exit-address-family
+ !
+ address-family ipv4 labeled-unicast
+  neighbor 192.0.2.1 activate
+ exit-address-family
+!

tests/topotests/bgp_lu_explicitnull/r2/zebra.conf

@@ -0,0 +1,6 @@
+interface r2-eth0
+ ip address 192.0.2.2/24
+!
+interface r2-eth1
+ ip address 192.168.2.2/32
+!

tests/topotests/bgp_lu_explicitnull/test_bgp_lu_explicitnull.py

@@ -0,0 +1,194 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+#
+# test_bgp_explicitnull.py
+#
+# Part of NetDEF Topology Tests
+#
+# Copyright 2023 by 6WIND S.A.
+#
+
+"""
+test_bgp_lu_explicitnull.py: Test BGP LU label allocation
+"""
+
+import os
+import sys
+import json
+import functools
+import pytest
+
+# Save the Current Working Directory to find configuration files.
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+
+# pylint: disable=C0413
+# Import topogen and topotest helpers
+from lib import topotest
+from lib.topogen import Topogen, TopoRouter, get_topogen
+from lib.topolog import logger
+
+
+pytestmark = [pytest.mark.bgpd]
+
+
+# Basic scenario for BGP-LU. Nodes are directly connected.
+# The 192.168.2.2/32 prefix is advertised from r2 to r1
+# The explicit-null label should be used
+# The 192.168.2.1/32 prefix is advertised from r1 to r2
+# The explicit-null label should be used
+# Traffic from 192.168.2.1 to 192.168.2.2 should use explicit-null label
+#
+#  AS65500    BGP-LU        AS65501
+# +-----+                +-----+
+# |     |.1            .2|     |
+# |  1  +----------------+  2  + 192.168.0.2/32
+# |     |   192.0.2.0/24 |     |
+# +-----+                +-----+
+
+
+def build_topo(tgen):
+    "Build function"
+
+    # Create routers
+    tgen.add_router("r1")
+    tgen.add_router("r2")
+
+    # r1-r2
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+    # r1
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r1"])
+
+    # r2
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+
+
+def setup_module(mod):
+    "Sets up the pytest environment"
+    # This function initiates the topology build with Topogen...
+    tgen = Topogen(build_topo, mod.__name__)
+
+    # Skip if no mpls support
+    if not tgen.hasmpls:
+        logger.info("MPLS is not available, skipping test")
+        pytest.skip("MPLS is not available, skipping")
+        return
+
+    # ... and here it calls Mininet initialization functions.
+    tgen.start_topology()
+
+    # This is a sample of configuration loading.
+    router_list = tgen.routers()
+
+    # Enable mpls input for routers, so we can ping
+    sval = "net.mpls.conf.{}.input"
+    topotest.sysctl_assure(router_list["r2"], sval.format("r2-eth0"), 1)
+    topotest.sysctl_assure(router_list["r1"], sval.format("r1-eth0"), 1)
+
+    # For all registred routers, load the zebra configuration file
+    for rname, router in router_list.items():
+        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))
+        )
+
+    # After loading the configurations, this function loads configured daemons.
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    "Teardown the pytest environment"
+    tgen = get_topogen()
+
+    # This function tears down the whole topology.
+    tgen.stop_topology()
+
+
+def check_show_ip_label_prefix_found(router, ipversion, prefix, label):
+    output = json.loads(
+        router.vtysh_cmd("show {} route {} json".format(ipversion, prefix))
+    )
+    expected = {prefix: [{"prefix": prefix, "nexthops": [{"fib": True, "labels": [label]}]}]}
+    ret = topotest.json_cmp(output, expected)
+    if ret is None:
+        return "not good"
+    return None
+
+def test_converge_bgplu():
+    "Wait for protocol convergence"
+
+    tgen = get_topogen()
+    # Don't run this test if we have any failure.
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    # tgen.mininet_cli();
+    r1 = tgen.gears["r1"]
+    r2 = tgen.gears["r2"]
+    # Check r1 gets prefix 192.168.2.2/32
+    test_func = functools.partial(
+        check_show_ip_label_prefix_found,
+        tgen.gears["r1"],
+        "ip",
+        "192.168.2.2/32",
+        "0",
+    )
+    success, result = topotest.run_and_expect(test_func, None, count=10, wait=0.5)
+    assert (
+        success
+    ), "r1, prefix 192.168.2.2/32 from r2 not present"
+
+    # Check r2 gets prefix 192.168.2.1/32
+    test_func = functools.partial(
+        check_show_ip_label_prefix_found,
+        tgen.gears["r2"],
+        "ip",
+        "192.168.2.1/32",
+        "0",
+    )
+    success, result = topotest.run_and_expect(test_func, None, count=10, wait=0.5)
+    assert (
+        success
+    ), "r2, prefix 192.168.2.1/32 from r1 not present"
+
+def test_traffic_connectivity():
+    "Wait for protocol convergence"
+
+    tgen = get_topogen()
+    # Don't run this test if we have any failure.
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    def _check_ping(name, dest_addr, src_addr):
+        tgen = get_topogen()
+        output = tgen.gears[name].run("ping {} -c 1 -w 1 -I {}".format(dest_addr, src_addr))
+        logger.info(output)
+        if " 0% packet loss" not in output:
+            return True
+
+    logger.info("r1, check ping 192.168.2.2 from 192.168.2.1 is OK")
+    tgen = get_topogen()
+    func = functools.partial(_check_ping, "r1", "192.168.2.2", "192.168.2.1")
+    # tgen.mininet_cli()
+    success, result = topotest.run_and_expect(func, None, count=10, wait=0.5)
+    assert result is None, "r1, ping to 192.168.2.2 from 192.168.2.1 fails"
+
+def test_memory_leak():
+    "Run the memory leak test and report results."
+    tgen = get_topogen()
+    if not tgen.is_memleak_enabled():
+        pytest.skip("Memory leak test/report is disabled")
+
+    tgen.report_memory_leaks()
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))