zebra: Add operational retrieval of Multipath Number

The multipath number specified is not available through
the yang data and is not retrievable.  Make it so.
At this point in time do not allow this to be set from
yang.  Perhaps in the future.

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

tests/topotests/zebra_operational_data/r1/frr.conf

@@ -0,0 +1,41 @@
+log timestamp precision 6
+log file frr.log
+
+no debug memstats-at-exit
+
+debug northbound notifications
+debug northbound libyang
+debug northbound events
+debug northbound callbacks
+
+debug mgmt backend datastore frontend transaction
+debug mgmt client frontend
+debug mgmt client backend
+
+interface r1-eth0
+  ip address 1.1.1.1/24
+  ipv6 address 2001:1111::1/64
+exit
+
+interface r1-eth1
+  ip address 2.2.2.1/24
+  ipv6 address 2002:2222::1/64
+exit
+
+interface r1-eth2 vrf red
+  ip address 3.3.3.1/24
+  ipv6 address 2003:333::1/64
+exit
+
+interface r1-eth3 vrf red
+  ip address 4.4.4.1/24
+  ipv6 address 2004:4444::1/64
+exit
+
+ip route 11.0.0.0/8 Null0
+ip route 11.11.11.11/32 1.1.1.2
+ip route 12.12.12.12/32 2.2.2.2
+
+ip route 13.0.0.0/8 Null0 vrf red
+ip route 13.13.13.13/32 3.3.3.2 vrf red
+ip route 14.14.14.14/32 4.4.4.2 vrf red

tests/topotests/zebra_operational_data/test_zebra_operational.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 eval: (blacken-mode 1) -*-
+# SPDX-License-Identifier: ISC
+#
+# Copyright (c) 2025 Nvidia Inc.
+# Donald Sharp
+#
+"""
+Test zebra operational values
+"""
+
+import pytest
+import json
+from lib.topogen import Topogen
+from lib.topolog import logger
+
+
+pytestmark = [pytest.mark.mgmtd]
+
+
+@pytest.fixture(scope="module")
+def tgen(request):
+    "Setup/Teardown the environment and provide tgen argument to tests"
+
+    topodef = {"s1": ("r1",), "s2": ("r1",), "s3": ("r1",), "s4": ("r1",)}
+
+    tgen = Topogen(topodef, request.module.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+    for rname, router in router_list.items():
+        # Setup VRF red
+        router.net.add_l3vrf("red", 10)
+        router.net.add_loop("lo-red")
+        router.net.attach_iface_to_l3vrf("lo-red", "red")
+        router.net.attach_iface_to_l3vrf(rname + "-eth2", "red")
+        router.net.attach_iface_to_l3vrf(rname + "-eth3", "red")
+        router.load_frr_config("frr.conf")
+
+    tgen.start_router()
+    yield tgen
+    tgen.stop_topology()
+
+
+def test_zebra_operationalr(tgen):
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+
+    output = json.loads(r1.vtysh_cmd("show mgmt get-data /frr-zebra:zebra"))
+
+    logger.info("Output")
+    logger.info(output)
+
+    logger.info("Ensuring that the max-multipath value is returned")
+    assert "max-multipath" in output["frr-zebra:zebra"].keys()
+
+
+if __name__ == "__main__":
+    # To suppress tracebacks, either use the following pytest call or add "--tb=no" to cli
+    # retval = pytest.main(["-s", "--tb=no"])
+    retval = pytest.main(["-s"])
+    sys.exit(retval)

yang/frr-zebra.yang

@@ -2842,6 +2842,17 @@ module frr-zebra {
   container zebra {
     description
       "Data model for the Zebra daemon.";
+    leaf max-multipath {
+      config false;
+      type uint16 {
+        range "1..65535";
+      }
+      description
+        "The maximum number of nexthops for a route.  At this point it
+         is unlikely that a multipath number will ever get larger then
+         1024 but to allow for future expansions, the yang returns a
+         16 bit number";
+    }
     leaf ip-forwarding {
       type boolean;
       description

zebra/zebra_nb.c

@@ -25,6 +25,12 @@ const struct frr_yang_module_info frr_zebra_info = {
 	.name = "frr-zebra",
 	.features = features,
 	.nodes = {
+		{
+			.xpath = "/frr-zebra:zebra/max-multipath",
+			.cbs = {
+				.get_elem = zebra_max_multipath_get_elem,
+			}
+		},
 		{
 			.xpath = "/frr-zebra:zebra/ip-forwarding",
 			.cbs = {

zebra/zebra_nb.h

@@ -14,6 +14,7 @@ extern "C" {
 extern const struct frr_yang_module_info frr_zebra_info;
 
 /* prototypes */
+struct yang_data *zebra_max_multipath_get_elem(struct nb_cb_get_elem_args *args);
 int get_route_information_rpc(struct nb_cb_rpc_args *args);
 int get_v6_mroute_info_rpc(struct nb_cb_rpc_args *args);
 int get_vrf_info_rpc(struct nb_cb_rpc_args *args);

zebra/zebra_nb_state.c

@@ -1157,3 +1157,12 @@ lib_vrf_zebra_ribs_rib_route_route_entry_nexthop_group_nexthop_weight_get_elem(
 
 	return NULL;
 }
+
+/*
+ * XPath:
+ * /frr-zebra:zebra/max-multipath
+ */
+struct yang_data *zebra_max_multipath_get_elem(struct nb_cb_get_elem_args *args)
+{
+	return yang_data_new_uint16(args->xpath, zrouter.multipath_num);
+}