Skip MTU check during deletion of Networks

MTU check can be skipped during deletion of Networks.
The MTU check doesn't provide any additional support during deletion
of the networks.

Also, if a network is created with MTU 'X' and the
global_mtu later on is decreased to 'Y', the created
network cannot be deleted due to the MTU check.

Change-Id: Ia838d2a661c5098f90b58b2cb31557f2ebf78868
Closes-Bug: #1713499

neutron/plugins/ml2/plugin.py

@@ -1937,7 +1937,8 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
         # change in segments could affect resulting network mtu, so let's
         # recalculate it
         network_db = self._get_network(context, network_id)
-        network_db.mtu = self._get_network_mtu(network_db)
+        network_db.mtu = self._get_network_mtu(network_db,
+            validate=(event != events.PRECOMMIT_DELETE))
         network_db.save(session=context.session)
 
         try:

neutron/tests/fullstack/resources/client.py

@@ -57,6 +57,11 @@ class ClientFixture(fixtures.Fixture):
         resp = update(id, body=body)
         return resp[resource_type]
 
+    def _delete_resource(self, resource_type, id):
+        delete = getattr(self.client, 'delete_%s' % resource_type)
+
+        return delete(id)
+
     def create_router(self, tenant_id, name=None, ha=False,
                       external_network=None):
         resource_type = 'router'
@@ -70,7 +75,7 @@ class ClientFixture(fixtures.Fixture):
 
     def create_network(self, tenant_id, name=None, external=False,
                        network_type=None, segmentation_id=None,
-                       physical_network=None):
+                       physical_network=None, mtu=None):
         resource_type = 'network'
 
         name = name or utils.get_rand_name(prefix=resource_type)
@@ -83,12 +88,17 @@ class ClientFixture(fixtures.Fixture):
             spec['provider:network_type'] = network_type
         if physical_network is not None:
             spec['provider:physical_network'] = physical_network
+        if mtu is not None:
+            spec['mtu'] = mtu
 
         return self._create_resource(resource_type, spec)
 
     def update_network(self, id, **kwargs):
         return self._update_resource('network', id, kwargs)
 
+    def delete_network(self, id):
+        return self._delete_resource('network', id)
+
     def create_subnet(self, tenant_id, network_id,
                       cidr, gateway_ip=None, name=None, enable_dhcp=True,
                       ipv6_address_mode='slaac', ipv6_ra_mode='slaac'):

neutron/tests/fullstack/resources/config.py

@@ -61,6 +61,7 @@ class NeutronConfigFixture(ConfigFixture):
                 'service_plugins': env_desc.service_plugins,
                 'auth_strategy': 'noauth',
                 'debug': 'True',
+                'global_physnet_mtu': env_desc.global_mtu,
                 'agent_down_time': str(env_desc.agent_down_time),
                 'transport_url':
                     'rabbit://%(user)s:%(password)s@%(host)s:5672/%(vhost)s' %

neutron/tests/fullstack/resources/environment.py

@@ -18,6 +18,7 @@ from neutronclient.common import exceptions as nc_exc
 from oslo_config import cfg
 
 from neutron.agent.linux import ip_lib
+from neutron.common import constants as common_const
 from neutron.common import utils as common_utils
 from neutron.plugins.ml2.drivers.linuxbridge.agent import \
     linuxbridge_neutron_agent as lb_agent
@@ -36,7 +37,8 @@ class EnvironmentDescription(object):
     def __init__(self, network_type='vxlan', l2_pop=True, qos=False,
                  mech_drivers='openvswitch,linuxbridge',
                  service_plugins='router', arp_responder=False,
-                 agent_down_time=75, router_scheduler=None):
+                 agent_down_time=75, router_scheduler=None,
+                 global_mtu=common_const.DEFAULT_NETWORK_MTU):
         self.network_type = network_type
         self.l2_pop = l2_pop
         self.qos = qos
@@ -45,7 +47,7 @@ class EnvironmentDescription(object):
         self.arp_responder = arp_responder
         self.agent_down_time = agent_down_time
         self.router_scheduler = router_scheduler
-
+        self.global_mtu = global_mtu
         self.service_plugins = service_plugins
         if self.qos:
             self.service_plugins += ',qos'

neutron/tests/fullstack/test_mtu.py

@@ -0,0 +1,61 @@
+# Copyright 2017 NEC India
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+# from neutronclient.common import exceptions
+from oslo_utils import uuidutils
+
+from neutron.tests.fullstack import base
+from neutron.tests.fullstack.resources import environment
+from neutron.tests.unit import testlib_api
+
+load_tests = testlib_api.module_load_tests
+
+
+class MTUNetworkTestSetup(base.BaseFullStackTestCase):
+    host_desc = []  # No need to register agents for this test case
+
+    def setUp(self):
+        env = environment.Environment(
+            environment.EnvironmentDescription(),
+            self.host_desc)
+        super(MTUNetworkTestSetup, self).setUp(env)
+
+        self.tenant_id = uuidutils.generate_uuid()
+
+    def _restart_neutron_server(self, global_mtu):
+        env = environment.Environment(
+            environment.EnvironmentDescription(global_mtu=global_mtu),
+            self.host_desc)
+        env.test_name = self.get_name()
+        self.useFixture(env)
+        env.neutron_server.restart()
+
+
+class TestMTUScenarios(MTUNetworkTestSetup):
+
+    def test_mtu_update_delete_network(self):
+        network = self.safe_client.create_network(self.tenant_id,
+                                                  name='mtu-test-network',
+                                                  mtu=1450)
+        self.safe_client.update_network(network['id'], mtu=9000)
+        res = self.safe_client.delete_network(network['id'])
+        self.assertEqual((), res)
+
+    def test_global_physnet_mtu_update_delete_network(self):
+        network = self.safe_client.create_network(self.tenant_id,
+                                                  name='mtu-test-network',
+                                                  mtu=1450)
+        self._restart_neutron_server(1400)
+        res = self.safe_client.delete_network(network['id'])
+        self.assertEqual((), res)