ml2 lb: do not program arp responder when unused

When arp_responder is not set, the proxy flag is not set on the VXLAN
VTEP interface so no ARP/ND responses are sent. In this (default case)
it is unnecessary to populate the neighbor table on each VxLAN VTEP
interface.

Change-Id: I0fff2228b5b819829edac0bb6597ecb8e5a036ad

neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py

@@ -675,10 +675,12 @@ class LinuxBridgeManager(amb.CommonAgentManagerBase):
         return (agent_ip in entries and mac in entries)
 
     def add_fdb_ip_entry(self, mac, ip, interface):
-        ip_lib.IPDevice(interface).neigh.add(ip, mac)
+        if cfg.CONF.VXLAN.arp_responder:
+            ip_lib.IPDevice(interface).neigh.add(ip, mac)
 
     def remove_fdb_ip_entry(self, mac, ip, interface):
-        ip_lib.IPDevice(interface).neigh.delete(ip, mac)
+        if cfg.CONF.VXLAN.arp_responder:
+            ip_lib.IPDevice(interface).neigh.delete(ip, mac)
 
     def add_fdb_bridge_entry(self, mac, agent_ip, interface, operation="add"):
         utils.execute(['bridge', 'fdb', operation, mac, 'dev', interface,

neutron/tests/unit/plugins/ml2/drivers/linuxbridge/agent/test_linuxbridge_neutron_agent.py

@@ -940,7 +940,7 @@ class TestLinuxBridgeRpcCallbacks(base.BaseTestCase):
                 self.assertEqual(0, del_fn.call_count)
                 self.assertEqual(1, log.call_count)
 
-    def test_fdb_add(self):
+    def _test_fdb_add(self, proxy_enabled=False):
         fdb_entries = {'net_id':
                        {'ports':
                         {'agent_ip': [constants.FLOODING_ENTRY,
@@ -968,7 +968,17 @@ class TestLinuxBridgeRpcCallbacks(base.BaseTestCase):
                           check_exit_code=False),
             ]
             execute_fn.assert_has_calls(expected)
-            add_fn.assert_called_with('port_ip', 'port_mac')
+            if proxy_enabled:
+                add_fn.assert_called_with('port_ip', 'port_mac')
+            else:
+                add_fn.assert_not_called()
+
+    def test_fdb_add(self):
+        self._test_fdb_add(proxy_enabled=False)
+
+    def test_fdb_add_with_arp_responder(self):
+        cfg.CONF.set_override('arp_responder', True, 'VXLAN')
+        self._test_fdb_add(proxy_enabled=True)
 
     def test_fdb_ignore(self):
         fdb_entries = {'net_id':
@@ -999,7 +1009,7 @@ class TestLinuxBridgeRpcCallbacks(base.BaseTestCase):
 
             self.assertFalse(execute_fn.called)
 
-    def test_fdb_remove(self):
+    def _test_fdb_remove(self, proxy_enabled=False):
         fdb_entries = {'net_id':
                        {'ports':
                         {'agent_ip': [constants.FLOODING_ENTRY,
@@ -1025,9 +1035,19 @@ class TestLinuxBridgeRpcCallbacks(base.BaseTestCase):
                           check_exit_code=False),
             ]
             execute_fn.assert_has_calls(expected)
-            del_fn.assert_called_with('port_ip', 'port_mac')
+            if proxy_enabled:
+                del_fn.assert_called_with('port_ip', 'port_mac')
+            else:
+                del_fn.assert_not_called()
 
-    def test_fdb_update_chg_ip(self):
+    def test_fdb_remove(self):
+        self._test_fdb_remove(proxy_enabled=False)
+
+    def test_fdb_remove_with_arp_responder(self):
+        cfg.CONF.set_override('arp_responder', True, 'VXLAN')
+        self._test_fdb_remove(proxy_enabled=True)
+
+    def _test_fdb_update_chg_ip(self, proxy_enabled=False):
         fdb_entries = {'chg_ip':
                        {'net_id':
                         {'agent_ip':
@@ -1040,8 +1060,19 @@ class TestLinuxBridgeRpcCallbacks(base.BaseTestCase):
                                   return_value='') as del_fn:
             self.lb_rpc.fdb_update(None, fdb_entries)
 
-            del_fn.assert_called_with('port_ip_1', 'port_mac')
+            if proxy_enabled:
-            add_fn.assert_called_with('port_ip_2', 'port_mac')
+                del_fn.assert_called_with('port_ip_1', 'port_mac')
+                add_fn.assert_called_with('port_ip_2', 'port_mac')
+            else:
+                del_fn.assert_not_called()
+                add_fn.assert_not_called()
+
+    def test_fdb_update_chg_ip(self):
+        self._test_fdb_update_chg_ip(proxy_enabled=False)
+
+    def test_fdb_update_chg_ip_with_arp_responder(self):
+        cfg.CONF.set_override('arp_responder', True, 'VXLAN')
+        self._test_fdb_update_chg_ip(proxy_enabled=True)
 
     def test_fdb_update_chg_ip_empty_lists(self):
         fdb_entries = {'chg_ip': {'net_id': {'agent_ip': {}}}}