zebra: return fully-resolved route to NHT clients

tests/topotests/zebra_nht_double_recursion/r1/bgpd.conf

@@ -0,0 +1,12 @@
+router bgp 65001
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor 10.0.0.2 remote-as internal
+ neighbor 10.0.0.2 update-source lo
+ neighbor 10.0.0.2 timers 1 3
+ neighbor 10.0.0.2 timers connect 1
+ neighbor 10.0.0.3 remote-as internal
+ neighbor 10.0.0.3 update-source lo
+ neighbor 10.0.0.3 timers 1 3
+ neighbor 10.0.0.3 timers connect 1
+!

tests/topotests/zebra_nht_double_recursion/r1/ospfd.conf

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+!
+interface lo
+ ip ospf passive
+!
+interface r1-eth0
+ ip ospf dead-interval 4
+ ip ospf hello-interval 1
+ ip ospf cost 10
+!
+interface r1-eth1
+ ip ospf dead-interval 4
+ ip ospf hello-interval 1
+ ip ospf cost 30
+!
+router ospf
+ router-id 10.0.0.1
+ network 0.0.0.0/0 area 0

tests/topotests/zebra_nht_double_recursion/r1/zebra.conf

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+!
+interface lo
+ ip address 10.0.0.1/32
+!
+interface r1-eth0
+ ip address 192.168.12.1/24
+!
+interface r1-eth1
+ ip address 192.168.13.1/24
+!

tests/topotests/zebra_nht_double_recursion/r2/bgpd.conf

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+router bgp 65001
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor 10.0.0.1 remote-as internal
+ neighbor 10.0.0.1 update-source lo
+ neighbor 10.0.0.1 timers 1 3
+ neighbor 10.0.0.1 timers connect 1
+ neighbor 192.168.24.4 remote-as external
+ neighbor 192.168.24.4 timers 1 3
+ neighbor 192.168.24.4 timers connect 1
+ address-family ipv4
+  redistribute connected route-map connected-to-bgp
+ exit-address-family
+!
+route-map connected-to-bgp permit 10
+ set metric 100
+ set community no-export
+!

tests/topotests/zebra_nht_double_recursion/r2/ospfd.conf

@@ -0,0 +1,13 @@
+!
+interface lo
+ ip ospf passive
+!
+interface r2-eth0
+ ip ospf dead-interval 4
+ ip ospf hello-interval 1
+ ip ospf cost 10
+!
+router ospf
+ router-id 10.0.0.2
+ network 192.168.12.0/24 area 0
+ network 10.0.0.2/32 area 0

tests/topotests/zebra_nht_double_recursion/r2/zebra.conf

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+!
+interface lo
+ ip address 10.0.0.2/32
+!
+interface r2-eth0
+ ip address 192.168.12.2/24
+!
+interface r2-eth1
+ ip address 192.168.24.2/24
+!

tests/topotests/zebra_nht_double_recursion/r3/bgpd.conf

@@ -0,0 +1,18 @@
+router bgp 65001
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor 10.0.0.1 remote-as internal
+ neighbor 10.0.0.1 update-source lo
+ neighbor 10.0.0.1 timers 1 3
+ neighbor 10.0.0.1 timers connect 1
+ neighbor 192.168.34.4 remote-as external
+ neighbor 192.168.34.4 timers 1 3
+ neighbor 192.168.34.4 timers connect 1
+ address-family ipv4
+  redistribute connected route-map connected-to-bgp
+ exit-address-family
+!
+route-map connected-to-bgp permit 10
+ set metric 100
+ set community no-export
+!

tests/topotests/zebra_nht_double_recursion/r3/ospfd.conf

@@ -0,0 +1,13 @@
+!
+interface lo
+ ip ospf passive
+!
+interface r3-eth0
+ ip ospf dead-interval 4
+ ip ospf hello-interval 1
+ ip ospf cost 30
+!
+router ospf
+ router-id 10.0.0.3
+ network 192.168.13.0/24 area 0
+ network 10.0.0.3/32 area 0

tests/topotests/zebra_nht_double_recursion/r3/zebra.conf

@@ -0,0 +1,10 @@
+!
+interface lo
+ ip address 10.0.0.3/32
+!
+interface r3-eth0
+ ip address 192.168.13.3/24
+!
+interface r3-eth1
+ ip address 192.168.34.3/24
+!

tests/topotests/zebra_nht_double_recursion/r4/bgpd.conf

@@ -0,0 +1,13 @@
+router bgp 65002
+ no bgp ebgp-requires-policy
+ no bgp network import-check
+ neighbor 192.168.24.2 remote-as external
+ neighbor 192.168.24.2 timers 1 3
+ neighbor 192.168.24.2 timers connect 1
+ neighbor 192.168.34.3 remote-as external
+ neighbor 192.168.34.3 timers 1 3
+ neighbor 192.168.34.3 timers connect 1
+ address-family ipv4
+  network 10.0.0.4/32
+ exit-address-family
+!

tests/topotests/zebra_nht_double_recursion/r4/zebra.conf

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+!
+interface lo
+ ip address 10.0.0.4/32
+!
+interface r4-eth0
+ ip address 192.168.24.4/24
+!
+interface r4-eth1
+ ip address 192.168.34.4/24
+!

tests/topotests/zebra_nht_double_recursion/test_nht_double_recusion.py

@@ -0,0 +1,207 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+#
+# Copyright (C) 2024 by Palo Alto Networks, Inc.
+# Enke Chen <[email protected]>
+#
+
+"""
+Test to make sure the nexthop being tracked is resolved recursivley to
+an OSPF route so that the right IGP metric is given to BGP for bestpath
+calculation.
+
+In this test, on r2/r3, the "next-hop-self" is not configured, and the
+connected routes are redistributed into BGP for the nexthop reachability
+of the EBGP routes.
+
+IP Addresses for the loopback interfaces:
+
+  r1: 10.0.0.1/32
+  r2: 10.0.0.2/32
+  r3: 10.0.0.3/32
+  r4: 10.0.0.4/32
+
+10.0.0.4/32 is redistributed into BGP on r4, and is advertised to both
+r2 and r3.  Then r1 receives 10.0.0.4/32 from both r2 and r3, and each of
+the nexthops is resolved to another BGP route which is then resolved to
+an OSPF route.
+
+On r1, the best path for 10.0.0.4/32 should be the one from r2 due to
+the lower IGP metric (10 vs 30) to the nexthop.
+
+
+                    10               30
+              r2  ------- r1 (UUT) ------- r3
+              |                            |
+         ebgp |                            | ebgp
+              |                            |
+              +----------- r4 -------------+
+                     .24.4    .34.4
+
+
+On r1 (UUT):
+
+[BGP] 10.0.0.4/32: nexthop 192.168.24.4
+                   nexthop 192.168.34.4
+
+192.168.24.4 --> [BGP] 192.168.24.0/24
+192.168.34.4 --> [BGP] 192.168.34.0/24
+
+[BGP] 192.168.24.0/24: nexthop 10.0.0.2
+[BGP] 192.168.34.0/24: nexthop 10.0.0.3
+
+10.0.0.2 --> [OSPF] 10.0.0.2/32, nexthop xxx, intf xxx
+10.0.0.3 --> [OSPF] 10.0.0.3/32, nexthop xxx, intf xxx
+"""
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+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, TopoRouter, get_topogen
+from lib.common_config import step
+
+pytestmark = [pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    for routern in range(1, 5):
+        tgen.add_router("r{}".format(routern))
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+    switch = tgen.add_switch("s2")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r3"])
+
+    switch = tgen.add_switch("s3")
+    switch.add_link(tgen.gears["r2"])
+    switch.add_link(tgen.gears["r4"])
+
+    switch = tgen.add_switch("s4")
+    switch.add_link(tgen.gears["r3"])
+    switch.add_link(tgen.gears["r4"])
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for i, (rname, router) in enumerate(router_list.items(), 1):
+        router.load_config(
+            TopoRouter.RD_ZEBRA, os.path.join(CWD, "{}/zebra.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_OSPF, os.path.join(CWD, "{}/ospfd.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_BGP, os.path.join(CWD, "{}/bgpd.conf".format(rname))
+        )
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_nht_recursive():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r1 = tgen.gears["r1"]
+    r2 = tgen.gears["r2"]
+    r3 = tgen.gears["r3"]
+    r4 = tgen.gears["r4"]
+
+    def _check_ip_nht_24_4():
+        output = json.loads(r1.vtysh_cmd("show ip nht 192.168.24.4 json"))
+        expected = {
+	  "default":{
+	    "ipv4":{
+	      "192.168.24.4":{
+	        "prefixes":[
+	          {
+	            "prefix":"192.168.24.0/24"
+	          },
+	          {
+	            "prefix":"10.0.0.2/32"
+	          }
+	        ],
+	        "resolvedProtocol":"ospf"
+	      }
+	    }
+	  }
+	}
+        return topotest.json_cmp(output, expected)
+
+    def _check_ip_nht_34_4():
+        output = json.loads(r1.vtysh_cmd("show ip nht 192.168.34.4 json"))
+        expected = {
+	  "default":{
+	    "ipv4":{
+	      "192.168.34.4":{
+	        "prefixes":[
+	          {
+	            "prefix":"192.168.34.0/24"
+	          },
+	          {
+	            "prefix":"10.0.0.3/32"
+	          }
+	        ],
+	        "resolvedProtocol":"ospf"
+	      }
+	    }
+	  }
+	}
+        return topotest.json_cmp(output, expected)
+
+    def _bgp_check_igp_metric_bestpath():
+        output = json.loads(r1.vtysh_cmd("show bgp ipv4 unicast 10.0.0.4/32 json"))
+        expected = {
+            "paths": [
+                {
+                    "bestpath": {"selectionReason": "IGP Metric"},
+                    "nexthops": [{"ip": "192.168.24.4", "hostname": "r2", "metric": 10, "accessible": True}],
+                },
+                {
+                    "nexthops": [{"ip": "192.168.34.4", "hostname": "r3", "metric": 30, "accessible": True}],
+                },
+            ]
+        }
+        return topotest.json_cmp(output, expected)
+
+    # Check ip nht resolved to ospf
+    test_func = functools.partial(_check_ip_nht_24_4)
+    _, result = topotest.run_and_expect(test_func, None, count=20, wait=2)
+    assert result is None, "ip nht for 24.4 not resolved to ospf"
+
+    # Check ip nht resolved to ospf
+    test_func = functools.partial(_check_ip_nht_34_4)
+    _, result = topotest.run_and_expect(test_func, None, count=20, wait=2)
+    assert result is None, "ip nht for 34.4 not resolved to ospf"
+
+    # Check BGP bestpath selected on IGP metric
+    test_func = functools.partial(_bgp_check_igp_metric_bestpath)
+    _, result = topotest.run_and_expect(test_func, None, count=20, wait=2)
+    assert result is None, "BGP bestpath not selected on igp metric"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))