Change external_network_bridge default to ''

This changes the default for external_network_bridge to '' to
encourage operators to deploy L3 agents in the correct manner.

This patch also adds a functional test to ensure that namespaces
with an existing external gateway interface are not torn down and
rewired on change.

Closes-Bug: #1563070
Change-Id: If533cf7c4c379be78f5a15073accaff7f65973ab

neutron/agent/common/config.py

@@ -83,14 +83,14 @@ AVAILABILITY_ZONE_OPTS = [
 ]
 
 EXT_NET_BRIDGE_OPTS = [
-    cfg.StrOpt('external_network_bridge', default='br-ex',
+    cfg.StrOpt('external_network_bridge', default='',
                deprecated_for_removal=True,
                help=_("Name of bridge used for external network "
-                      "traffic. This should be set to an empty value for the "
-                      "Linux Bridge. When this parameter is set, each L3 "
-                      "agent can be associated with no more than one external "
-                      "network. This option is deprecated and will be removed "
-                      "in the M release.")),
+                      "traffic. When this parameter is set, the L3 agent will "
+                      "plug an interface directly into an external bridge "
+                      "which will not allow any wiring by the L2 agent. Using "
+                      "this will result in incorrect port statuses. This "
+                      "option is deprecated and will be removed in Ocata."))
 ]
 
 

neutron/db/l3_db.py

@@ -332,7 +332,7 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
             ext_net_id = agent['configurations'].get(
                 'gateway_external_network_id')
             ext_bridge = agent['configurations'].get(
-                'external_network_bridge', 'br-ex')
+                'external_network_bridge', '')
             if (ext_net_id == network_id or
                     (not ext_net_id and not ext_bridge)):
                 return

neutron/tests/functional/agent/l3/test_legacy_router.py

@@ -24,6 +24,7 @@ from neutron.agent.linux import ip_lib
 from neutron.callbacks import events
 from neutron.callbacks import registry
 from neutron.callbacks import resources
+from neutron.tests import base as tests_base
 from neutron.tests.common import machine_fixtures
 from neutron.tests.common import net_helpers
 from neutron.tests.functional.agent.l3 import framework
@@ -96,6 +97,39 @@ class L3AgentTestCase(framework.L3AgentTestFramework):
 
         self.assertIsNone(device.route.get_gateway())
 
+    def _make_bridge(self):
+        bridge = framework.get_ovs_bridge(tests_base.get_rand_name())
+        bridge.create()
+        self.addCleanup(bridge.destroy)
+        return bridge
+
+    def test_external_network_bridge_change(self):
+        bridge1, bridge2 = self._make_bridge(), self._make_bridge()
+        self.agent.conf.set_override('external_network_bridge',
+                                     bridge1.br_name)
+        router_info = self.generate_router_info(False)
+        router = self.manage_router(self.agent, router_info)
+        gw_port = router.router['gw_port']
+        gw_inf_name = router.get_external_device_name(gw_port['id'])
+
+        self.assertIn(gw_inf_name,
+                      [v.port_name for v in bridge1.get_vif_ports()])
+        # changeing the external_network_bridge should have no impact since
+        # the interface exists.
+        self.agent.conf.set_override('external_network_bridge',
+                                     bridge2.br_name)
+        self.manage_router(self.agent, router_info)
+        self.assertIn(gw_inf_name,
+                      [v.port_name for v in bridge1.get_vif_ports()])
+        self.assertNotIn(gw_inf_name,
+                         [v.port_name for v in bridge2.get_vif_ports()])
+        namespaces.Namespace.delete(router.router_namespace)
+        self.manage_router(self.agent, router_info)
+        self.assertIn(gw_inf_name,
+                      [v.port_name for v in bridge2.get_vif_ports()])
+        self.assertNotIn(gw_inf_name,
+                         [v.port_name for v in bridge1.get_vif_ports()])
+
     def test_legacy_router_ns_rebuild(self):
         router_info = self.generate_router_info(False)
         router = self.manage_router(self.agent, router_info)

neutron/tests/unit/agent/l3/test_agent.py

@@ -1813,7 +1813,7 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
 
         self.mock_driver.unplug.assert_called_with(
             stale_devnames[0],
-            bridge="br-ex",
+            bridge="",
             namespace=ri.ns_name,
             prefix=l3_agent.EXTERNAL_DEV_PREFIX)
 
@@ -1994,6 +1994,7 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
         self._test_process_routers_update_router_deleted(True)
 
     def test_process_router_if_compatible_with_no_ext_net_in_conf(self):
+        self.conf.set_override('external_network_bridge', 'br-ex')
         agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
         self.plugin_api.get_external_network_id.return_value = 'aaa'
 
@@ -2022,6 +2023,7 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
         self.assertFalse(self.plugin_api.get_external_network_id.called)
 
     def test_process_router_if_compatible_with_stale_cached_ext_net(self):
+        self.conf.set_override('external_network_bridge', 'br-ex')
         agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
         self.plugin_api.get_external_network_id.return_value = 'aaa'
         agent.target_ex_net_id = 'bbb'
@@ -2037,6 +2039,7 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
             agent.context)
 
     def test_process_router_if_compatible_w_no_ext_net_and_2_net_plugin(self):
+        self.conf.set_override('external_network_bridge', 'br-ex')
         agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
 
         router = {'id': _uuid(),
@@ -2078,7 +2081,6 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
                   'external_gateway_info': {'network_id': 'aaa'}}
 
         agent.router_info = {}
-        self.conf.set_override('external_network_bridge', '')
         agent._process_router_if_compatible(router)
         self.assertIn(router['id'], agent.router_info)
 

neutron/tests/unit/debug/test_commands.py

@@ -173,7 +173,7 @@ class TestDebugCommands(base.BaseTestCase):
                                                      'fake_port',
                                                      'tap12345678-12',
                                                      'aa:bb:cc:dd:ee:ffa',
-                                                     bridge='br-ex',
+                                                     bridge='',
                                                      namespace=namespace),
                                       mock.call.init_l3('tap12345678-12',
                                                         ['10.0.0.3/24'],
@@ -223,7 +223,7 @@ class TestDebugCommands(base.BaseTestCase):
         self.driver.assert_has_calls([mock.call.get_device_name(mock.ANY),
                                       mock.call.unplug('tap12345678-12',
                                                        namespace=namespace,
-                                                       bridge='br-ex')])
+                                                       bridge='')])
 
     def test_list_probe(self):
         cmd = commands.ListProbe(self.app, None)

releasenotes/notes/change_external_network_bridge_default-5de3a0c19182eb70.yaml

@@ -0,0 +1,16 @@
+---
+prelude: >
+    The default value for 'external_network_bridge' in the L3 agent is now ''.
+upgrade:
+  - The default value for 'external_network_bridge' has been changed to ''
+    since that is the preferred way to configure the L3 agent and will be the
+    only way in future releases. If you have not explicitly set this value
+    and you use the L3 agent, you will need to set this value to 'br-ex' to
+    match the old default.
+    If you are using 'br-ex', you should switch to '', ensure your external
+    network has a flat segment and ensure your L2 agent has a bridge_mapping
+    entry between the external network's flat segment physnet and 'br-ex' to
+    get the same connectivity. If the external network did not already have
+    the flat segment, you will need to detach all routers from the external
+    networks, delete the incorrect segment type, add the flat segment, and
+    re-attach the routers.