topotests: add bgp duplicate nexthop test

Add a topotest that ensures that when addpath is enabled and two
paths with same nexthop are received, they are sent to ZEBRA which
detects 'duplicate nexthop'.

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

tests/topotests/bgp_duplicate_nexthop/r1/bgpd.conf

@@ -0,0 +1,13 @@
+router bgp 64500
+ bgp router-id 192.0.2.1
+ no bgp ebgp-requires-policy
+ neighbor rrserver peer-group
+ neighbor rrserver remote-as 64500
+ neighbor rrserver update-source lo
+ neighbor rrserver timers connect 2
+ neighbor 192.0.2.3 peer-group rrserver
+ address-family ipv4 unicast
+  neighbor rrserver next-hop-self
+  neighbor rrserver activate
+  exit-address-family
+!

tests/topotests/bgp_duplicate_nexthop/r1/isisd.conf

@@ -0,0 +1,26 @@
+hostname r1
+interface lo
+ ip router isis 1
+ isis passive
+!
+interface r1-eth1
+ ip router isis 1
+ isis network point-to-point
+!
+interface r1-eth2
+ ip router isis 1
+ isis network point-to-point
+!
+interface r1-eth4
+ ip router isis 1
+ isis network point-to-point
+!
+router isis 1
+ net 49.0123.6452.0001.00
+ is-type level-2-only
+ mpls-te on
+ segment-routing on
+ segment-routing global-block 16000 17000
+ segment-routing node-msd 10
+ segment-routing prefix 192.0.2.1/32 index 1
+!

tests/topotests/bgp_duplicate_nexthop/r1/zebra.conf

@@ -0,0 +1,24 @@
+log stdout
+interface lo
+ ip address 192.0.2.1/32
+!
+interface r1-eth0
+ ip address 172.31.10.1/24
+!
+interface r1-eth1
+ ip address 172.31.0.1/24
+ mpls enable
+!
+interface r1-eth2
+ ip address 172.31.2.1/24
+ mpls enable
+!
+interface r1-eth3
+ ip address 172.31.11.1/24
+ mpls enable
+!
+interface r1-eth4
+ ip address 172.31.8.1/24
+ mpls enable
+!
+

tests/topotests/bgp_duplicate_nexthop/r3/bgpd.conf

@@ -0,0 +1,16 @@
+router bgp 64500 view one
+ bgp router-id 192.0.2.3
+ neighbor rr peer-group
+ neighbor rr remote-as 64500
+ neighbor rr update-source lo
+ neighbor 192.0.2.1 peer-group rr
+ neighbor 192.0.2.5 peer-group rr
+ neighbor 192.0.2.6 peer-group rr
+ neighbor 192.0.2.8 peer-group rr
+ !
+ address-family ipv4 unicast
+  neighbor rr activate
+  neighbor rr route-reflector-client
+  neighbor rr addpath-tx-all-paths
+ exit-address-family
+!

tests/topotests/bgp_duplicate_nexthop/r3/isisd.conf

@@ -0,0 +1,38 @@
+hostname r3
+interface lo
+ ip router isis 1
+ isis passive
+!
+interface r3-eth0
+ ip router isis 1
+ isis network point-to-point
+!
+interface r3-eth1
+ ip router isis 1
+ isis network point-to-point
+!
+interface r3-eth2
+ ip router isis 1
+ isis network point-to-point
+!
+interface r3-eth3
+ ip router isis 1
+ isis network point-to-point
+!
+interface r3-eth4
+ ip router isis 1
+ isis network point-to-point
+!
+interface r3-eth5
+ ip router isis 1
+ isis network point-to-point
+!
+router isis 1
+ net 49.0123.6452.0003.00
+ is-type level-2-only
+ mpls-te on
+ segment-routing on
+ segment-routing global-block 16000 17000
+ segment-routing node-msd 10
+ segment-routing prefix 192.0.2.3/32 index 3
+!

tests/topotests/bgp_duplicate_nexthop/r3/zebra.conf

@@ -0,0 +1,16 @@
+log stdout
+interface lo
+ ip address 192.0.2.3/32
+!
+interface r3-eth0
+ ip address 172.31.0.3/24
+ mpls enable
+!
+interface r3-eth1
+ ip address 172.31.4.3/24
+ mpls enable
+!
+interface r3-eth2
+ ip address 172.31.5.3/24
+ mpls enable
+!

tests/topotests/bgp_duplicate_nexthop/r4/isisd.conf

@@ -0,0 +1,30 @@
+hostname r4
+interface lo
+ ip router isis 1
+ isis passive
+!
+interface r4-eth0
+ ip router isis 1
+ isis network point-to-point
+!
+interface r4-eth1
+ ip router isis 1
+ isis network point-to-point
+!
+interface r4-eth2
+ ip router isis 1
+ isis network point-to-point
+!
+interface r4-eth3
+ ip router isis 1
+ isis network point-to-point
+!
+router isis 1
+ net 49.0123.6452.0004.00
+ is-type level-2-only
+ mpls-te on
+ segment-routing on
+ segment-routing global-block 16000 17000
+ segment-routing node-msd 10
+ segment-routing prefix 192.0.2.4/32 index 4
+!

tests/topotests/bgp_duplicate_nexthop/r4/zebra.conf

@@ -0,0 +1,20 @@
+log stdout
+interface lo
+ ip address 192.0.2.4/32
+!
+interface r4-eth0
+ ip address 172.31.2.4/24
+ mpls enable
+!
+interface r4-eth1
+ ip address 172.31.6.4/24
+ mpls enable
+!
+interface r4-eth2
+ ip address 172.31.7.4/24
+ mpls enable
+!
+interface r4-eth3
+ mpls enable
+!
+

tests/topotests/bgp_duplicate_nexthop/r5/bgpd.conf

@@ -0,0 +1,19 @@
+router bgp 64500
+ bgp router-id 192.0.2.5
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor rrserver peer-group
+ neighbor rrserver remote-as 64500
+ neighbor rrserver update-source lo
+ neighbor rrserver timers connect 2
+ neighbor 192.0.2.3 peer-group rrserver
+ address-family ipv4 unicast
+  network 192.0.2.9/32
+  network 192.0.2.8/32 route-map rmap
+  neighbor rrserver activate
+  neighbor rrserver addpath-tx-all-paths
+ exit-address-family
+!
+route-map rmap permit 1
+ set ip next-hop 192.0.2.9
+exit

tests/topotests/bgp_duplicate_nexthop/r5/isisd.conf

@@ -0,0 +1,26 @@
+hostname r5
+interface lo
+ ip router isis 1
+ isis passive
+!
+interface r5-eth1
+ ip router isis 1
+ isis network point-to-point
+!
+interface r5-eth2
+ ip router isis 1
+ isis network point-to-point
+!
+interface r5-eth3
+ ip router isis 1
+ isis network point-to-point
+!
+router isis 1
+ net 49.0123.6452.0005.00
+ is-type level-2-only
+ mpls-te on
+ segment-routing on
+ segment-routing global-block 16000 17000
+ segment-routing node-msd 10
+ segment-routing prefix 192.0.2.5/32 index 55
+!

tests/topotests/bgp_duplicate_nexthop/r5/zebra.conf

@@ -0,0 +1,19 @@
+log stdout
+mpls label dynamic-block 5000 5999
+interface lo
+ ip address 192.0.2.5/32
+!
+interface r5-eth0
+ ip address 172.31.12.5/24
+!
+interface r5-eth1
+ ip address 172.31.4.5/24
+ mpls enable
+!
+interface r5-eth2
+ ip address 172.31.7.5/24
+ mpls enable
+!
+interface r5-eth3
+ ip address 172.31.21.5/24
+!

tests/topotests/bgp_duplicate_nexthop/r6/bgpd.conf

@@ -0,0 +1,19 @@
+router bgp 64500
+ bgp router-id 192.0.2.6
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor rrserver peer-group
+ neighbor rrserver remote-as 64500
+ neighbor rrserver update-source lo
+ neighbor rrserver bfd
+ neighbor 192.0.2.3 peer-group rrserver
+ address-family ipv4 unicast
+  network 192.0.2.9/32
+  network 192.0.2.8/32 route-map rmap
+  neighbor rrserver activate
+  neighbor rrserver addpath-tx-all-paths
+ exit-address-family
+!
+route-map rmap permit 1
+ set ip next-hop 192.0.2.9
+exit

tests/topotests/bgp_duplicate_nexthop/r6/isisd.conf

@@ -0,0 +1,22 @@
+hostname r6
+interface lo
+ ip router isis 1
+ isis passive
+!
+interface r6-eth1
+ ip router isis 1
+ isis network point-to-point
+!
+interface r6-eth2
+ ip router isis 1
+ isis network point-to-point
+!
+router isis 1
+ net 49.0123.6452.0006.00
+ is-type level-2-only
+ mpls-te on
+ segment-routing on
+ segment-routing global-block 16000 17000
+ segment-routing node-msd 10
+ segment-routing prefix 192.0.2.6/32 index 6
+!

tests/topotests/bgp_duplicate_nexthop/r6/zebra.conf

@@ -0,0 +1,20 @@
+log stdout
+mpls label dynamic-block 6000 6999
+interface lo
+ ip address 192.0.2.6/32
+!
+interface r6-eth0
+ ip address 172.31.13.6/24
+!
+interface r6-eth1
+ ip address 172.31.5.6/24
+ mpls enable
+!
+interface r6-eth2
+ ip address 172.31.6.6/24
+ mpls enable
+!
+interface r6-eth3
+ ip address 172.31.22.6/24
+!
+

tests/topotests/bgp_duplicate_nexthop/test_bgp_duplicate_nexthop.py

@@ -0,0 +1,458 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+
+#
+# test_bgp_duplicate_nexthop.py
+#
+# Copyright 2024 6WIND S.A.
+#
+
+"""
+ test_bgp_nhg_duplicate_nexthop.py:
+ Check that the FRR BGP daemon on r1 selects updates with same nexthops
+
+
++---+----+          +---+----+          +--------+
+|        |          |        +          |        |
+|  r1    +----------+  r3    +----------+  r5    +
+|        |          |  rr    +    +-----+        |
++++-+----+          +--------+\  /      +--------+
+    |                          \/
+    |                          /\
+    |               +--------+/  \      +--------+
+    |               |        +    +-----+        +
+    +---------------+  r4    +----------+  r6    +
+                    |        |          |        |
+                    +--------+          +--------+
+"""
+
+import os
+import sys
+import json
+from functools import partial
+import pytest
+import functools
+
+# 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.common_check import ip_check_path_selection, iproute2_check_path_selection
+from lib.common_config import step
+from lib.topogen import Topogen, TopoRouter, get_topogen
+from lib.topolog import logger
+
+# Required to instantiate the topology builder class.
+
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    "Build function"
+
+    # Create 7 PE routers.
+    tgen.add_router("r1")
+    tgen.add_router("r3")
+    tgen.add_router("r4")
+    tgen.add_router("r5")
+    tgen.add_router("r6")
+
+    # switch
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r5"])
+
+    switch = tgen.add_switch("s5")
+    switch.add_link(tgen.gears["r6"])
+
+    switch = tgen.add_switch("s6")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
+
+    switch = tgen.add_switch("s7")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r4"])
+
+    switch = tgen.add_switch("s8")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r5"])
+
+    switch = tgen.add_switch("s9")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r6"])
+
+    switch = tgen.add_switch("s10")
+    switch.add_link(tgen.gears["r4"])
+    switch.add_link(tgen.gears["r6"])
+
+    switch = tgen.add_switch("s11")
+    switch.add_link(tgen.gears["r4"])
+    switch.add_link(tgen.gears["r5"])
+
+    switch = tgen.add_switch("s12")
+    switch.add_link(tgen.gears["r5"])
+
+    switch = tgen.add_switch("s13")
+    switch.add_link(tgen.gears["r6"])
+
+    switch = tgen.add_switch("s14")
+    switch.add_link(tgen.gears["r1"])
+
+
+def setup_module(mod):
+    "Sets up the pytest environment"
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    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_ISIS, os.path.join(CWD, "{}/isisd.conf".format(rname))
+        )
+        if rname in ("r1", "r3", "r5", "r6"):
+            router.load_config(
+                TopoRouter.RD_BGP, os.path.join(CWD, "{}/bgpd.conf".format(rname))
+            )
+
+    # Initialize all routers.
+    tgen.start_router()
+
+
+def teardown_module(_mod):
+    "Teardown the pytest environment"
+    tgen = get_topogen()
+
+    tgen.stop_topology()
+
+
+def check_ipv4_prefix_with_multiple_nexthops(prefix, multipath=True):
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    logger.info(
+        f"Check that {prefix} unicast entry is installed with paths for r5 and r6"
+    )
+
+    r5_nh = [
+        {
+            "ip": "192.0.2.5",
+            "active": True,
+            "recursive": True,
+        },
+        {
+            "ip": "172.31.0.3",
+            "interfaceName": "r1-eth1",
+            "active": True,
+            "labels": [
+                16055,
+            ],
+        },
+        {
+            "ip": "172.31.2.4",
+            "interfaceName": "r1-eth2",
+            "active": True,
+            "labels": [
+                16055,
+            ],
+        },
+    ]
+
+    r6_nh = [
+        {
+            "ip": "192.0.2.6",
+            "active": True,
+            "recursive": True,
+        },
+        {
+            "ip": "172.31.0.3",
+            "interfaceName": "r1-eth1",
+            "active": True,
+            "labels": [
+                16006,
+            ],
+        },
+        {
+            "ip": "172.31.2.4",
+            "interfaceName": "r1-eth2",
+            "active": True,
+            "labels": [
+                16006,
+            ],
+        },
+    ]
+
+    expected = {
+        prefix: [
+            {
+                "prefix": prefix,
+                "protocol": "bgp",
+                "metric": 0,
+                "table": 254,
+                "nexthops": [],
+            }
+        ]
+    }
+    for nh in r5_nh:
+        expected[prefix][0]["nexthops"].append(nh)
+    if multipath:
+        for nh in r6_nh:
+            expected[prefix][0]["nexthops"].append(nh)
+
+    test_func = functools.partial(
+        ip_check_path_selection, tgen.gears["r1"], prefix, expected
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert (
+        result is None
+    ), f"Failed to check that {prefix} uses the IGP label 16055 and 16006"
+
+
+def get_nh_formatted(nexthop, fib=True, duplicate=False):
+    nh = dict(nexthop)
+    if duplicate:
+        nh.update({"duplicate": True})
+    if fib:
+        nh.update({"fib": True})
+    return nh
+
+
+def check_ipv4_prefix_recursive_with_multiple_nexthops(
+    prefix, recursive_nexthop, multipath=True
+):
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+    logger.info(
+        f"Check that {prefix} unicast entry is correctly recursive via {recursive_nexthop} with paths for r5 and r6"
+    )
+
+    r5_nh = [
+        {
+            "ip": "172.31.0.3",
+            "interfaceName": "r1-eth1",
+            "active": True,
+            "labels": [
+                16055,
+            ],
+        },
+        {
+            "ip": "172.31.2.4",
+            "interfaceName": "r1-eth2",
+            "active": True,
+            "labels": [
+                16055,
+            ],
+        },
+    ]
+
+    r6_nh = [
+        {
+            "ip": "172.31.0.3",
+            "interfaceName": "r1-eth1",
+            "active": True,
+            "labels": [
+                16006,
+            ],
+        },
+        {
+            "ip": "172.31.2.4",
+            "interfaceName": "r1-eth2",
+            "active": True,
+            "labels": [
+                16006,
+            ],
+        },
+    ]
+
+    expected = {
+        prefix: [
+            {
+                "prefix": prefix,
+                "protocol": "bgp",
+                "metric": 0,
+                "table": 254,
+                "nexthops": [],
+            }
+        ]
+    }
+
+    recursive_nh = [
+        {
+            "ip": recursive_nexthop,
+            "active": True,
+            "recursive": True,
+        },
+    ]
+    for nh in recursive_nh:
+        expected[prefix][0]["nexthops"].append(get_nh_formatted(nh, fib=False))
+
+    for nh in r5_nh:
+        expected[prefix][0]["nexthops"].append(get_nh_formatted(nh))
+
+    if multipath:
+        for nh in r6_nh:
+            expected[prefix][0]["nexthops"].append(get_nh_formatted(nh))
+
+        for nh in recursive_nh:
+            expected[prefix][0]["nexthops"].append(
+                get_nh_formatted(nh, fib=False, duplicate=True)
+            )
+
+        for nh in r5_nh:
+            expected[prefix][0]["nexthops"].append(
+                get_nh_formatted(nh, fib=False, duplicate=True)
+            )
+
+        for nh in r6_nh:
+            expected[prefix][0]["nexthops"].append(
+                get_nh_formatted(nh, fib=False, duplicate=True)
+            )
+
+    test_func = functools.partial(
+        ip_check_path_selection, tgen.gears["r1"], prefix, expected
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert (
+        result is None
+    ), f"Failed to check that {prefix} is correctly recursive via {recursive_nexthop}"
+
+
+def check_ipv4_prefix_with_multiple_nexthops_linux(prefix):
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    step(
+        f"Check that {prefix} unicast entry is installed with paths for r5 and r6 on Linux"
+    )
+
+    r5_nh = [
+        {
+            "encap": "mpls",
+            "dst": "16055",
+            "gateway": "172.31.0.3",
+            "dev": "r1-eth1",
+        },
+        {
+            "encap": "mpls",
+            "dst": "16055",
+            "gateway": "172.31.2.4",
+            "dev": "r1-eth2",
+        },
+    ]
+
+    r6_nh = [
+        {
+            "encap": "mpls",
+            "dst": "16006",
+            "gateway": "172.31.0.3",
+            "dev": "r1-eth1",
+        },
+        {
+            "encap": "mpls",
+            "dst": "16006",
+            "gateway": "172.31.2.4",
+            "dev": "r1-eth2",
+        },
+    ]
+
+    expected = [
+        {
+            "dst": prefix,
+            "protocol": "bgp",
+            "metric": 20,
+            "nexthops": [],
+        }
+    ]
+
+    # only one path
+    for nh in r5_nh:
+        expected[0]["nexthops"].append(nh)
+    for nh in r6_nh:
+        expected[0]["nexthops"].append(nh)
+
+    test_func = functools.partial(
+        iproute2_check_path_selection, tgen.routers()["r1"], prefix, expected
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert (
+        result is None
+    ), f"Failed to check that {prefix} unicast entry is installed with paths for r5 and r6 on Linux"
+
+
+def test_bgp_ipv4_convergence():
+    """
+    Check that R1 has received the 192.0.2.9/32 prefix from R5, and R6
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    logger.info("Ensure that the 192.0.2.9/32 route is available")
+    check_ipv4_prefix_with_multiple_nexthops("192.0.2.9/32")
+
+    check_ipv4_prefix_with_multiple_nexthops_linux("192.0.2.9")
+
+
+def test_bgp_ipv4_recursive_routes():
+    """
+    Check that R1 has received the recursive routes, and duplicate nexthops are in zebra, but are not installed
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    check_ipv4_prefix_recursive_with_multiple_nexthops("192.0.2.8/32", "192.0.2.9")
+
+    check_ipv4_prefix_with_multiple_nexthops_linux("192.0.2.8")
+
+
+def test_bgp_ipv4_recursive_routes_when_no_mpath():
+    """
+    Unconfigure multipath ibgp
+    Check that duplicate nexthops are not in zebra
+    """
+    tgen = get_topogen()
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    tgen.gears["r1"].vtysh_cmd(
+        """
+        configure terminal
+        router bgp
+        address family ipv4 unicast
+        maximum-paths ibgp 1
+        """,
+        isjson=False,
+    )
+    tgen.gears["r1"].vtysh_cmd("clear bgp ipv4 *")
+    check_ipv4_prefix_with_multiple_nexthops("192.0.2.9/32", multipath=False)
+
+    check_ipv4_prefix_recursive_with_multiple_nexthops(
+        "192.0.2.8/32", "192.0.2.9", multipath=False
+    )
+
+
+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))

tests/topotests/lib/common_check.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: ISC
+#
+# common_check.py
+#
+# Copyright 2024 6WIND S.A.
+
+#
+import json
+from lib import topotest
+
+
+def ip_check_path_selection(router, ipaddr_str, expected, vrf_name=None):
+    if vrf_name:
+        cmdstr = f'show ip route vrf {vrf_name} {ipaddr_str} json'
+    else:
+        cmdstr = f'show ip route {ipaddr_str} json'
+    try:
+        output = json.loads(router.vtysh_cmd(cmdstr))
+    except:
+        output = {}
+
+    ret = topotest.json_cmp(output, expected)
+    if ret is None:
+        num_nh_expected = len(expected[ipaddr_str][0]["nexthops"])
+        num_nh_observed = len(output[ipaddr_str][0]["nexthops"])
+        if num_nh_expected == num_nh_observed:
+            return ret
+        return "{}, prefix {} does not have the correct number of nexthops : observed {}, expected {}".format(
+            router.name, ipaddr_str, num_nh_observed, num_nh_expected
+        )
+    return ret
+
+
+def iproute2_check_path_selection(router, ipaddr_str, expected, vrf_name=None):
+    if not topotest.iproute2_is_json_capable():
+        return None
+
+    if vrf_name:
+        cmdstr = f'ip -json route show vrf {vrf_name} {ipaddr_str}'
+    else:
+        cmdstr = f'ip -json route show {ipaddr_str}'
+    try:
+        output = json.loads(cmdstr)
+    except:
+        output = []
+
+    return topotest.json_cmp(output, expected)