static_arp: T9268: Fix deletion of static ARP entries

2 files changed, 46 insertions, 4 deletions

diff --git a/smoketest/scripts/cli/test_protocols_static_arp.py b/smoketest/scripts/cli/test_protocols_static_arp.py
index f89cdacbb..47b04a48a 100755
--- a/smoketest/scripts/cli/test_protocols_static_arp.py
+++ b/smoketest/scripts/cli/test_protocols_static_arp.py
@@ -86,5 +86,39 @@ class TestARP(VyOSUnitTestSHIM.TestCase):
                 print(entry)
             self.assertTrue(found)
 
+    def test_static_arp_deletion(self):
+        # deleting the "protocols static arp" node must remove the
+        # previously installed PERMANENT ARP entry from the kernel
+        host = '192.0.2.10'
+        mac = '00:01:02:03:04:0a'
+
+        def get_static_arp_entry():
+            # Return our static (PERMANENT) neighbour, matched by dst + dev.
+            arp_table = json.loads(cmdl(['ip', '-j', '-4', 'neigh', 'show']))
+            for entry in arp_table:
+                if (
+                    entry['dst'] == host
+                    and entry['dev'] == interface
+                    and 'PERMANENT' in entry.get('state', [])
+                ):
+                    return entry
+            return None
+
+        self.cli_set(base_path + ['interface', interface, 'address', host, 'mac', mac])
+        self.cli_commit()
+
+        # the static PERMANENT entry must be present with all configured fields
+        entry = get_static_arp_entry()
+        self.assertIsNotNone(entry)
+        self.assertEqual(entry['dst'], host)
+        self.assertEqual(entry['lladdr'], mac)
+        self.assertEqual(entry['dev'], interface)
+
+        # delete the whole node and verify the static entry is gone
+        self.cli_delete(base_path)
+        self.cli_commit()
+
+        self.assertIsNone(get_static_arp_entry())
+
 if __name__ == '__main__':
     unittest.main(verbosity=2, failfast=VyOSUnitTestSHIM.TestCase.debug_on())
diff --git a/src/conf_mode/protocols_static_arp.py b/src/conf_mode/protocols_static_arp.py
index 87dc5229e..2b5570ab0 100755
--- a/src/conf_mode/protocols_static_arp.py
+++ b/src/conf_mode/protocols_static_arp.py
@@ -32,10 +32,18 @@ def get_config(config=None):
     base = ['protocols', 'static', 'arp']
     arp = conf.get_config_dict(base, get_first_key=True)
 
-    if 'interface' in arp:
-        for interface in arp['interface']:
-            tmp = node_changed(conf, base + ['interface', interface, 'address'], recursive=True)
-            if tmp: arp['interface'][interface].update({'address_old' : tmp})
+    # Collect both configured interfaces and interfaces removed in this commit
+    # (e.g. deleting the whole node), so their old ARP entries get cleaned up.
+    interfaces = set(arp.get('interface', {}))
+    interfaces.update(node_changed(conf, base + ['interface']))
+
+    for interface in interfaces:
+        tmp = node_changed(
+            conf, base + ['interface', interface, 'address'], recursive=True
+        )
+        if tmp:
+            arp.setdefault('interface', {}).setdefault(interface, {})
+            arp['interface'][interface].update({'address_old': tmp})
 
     return arp