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>

1 files changed, 48 insertions, 0 deletions

diff --git a/tests/topotests/lib/common_check.py b/tests/topotests/lib/common_check.py
new file mode 100644
index 0000000000..be3241fd20
--- /dev/null
+++ b/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)