Only update MTU in update code for MTU

The ML2 create_network_db was re-passing in the entire network
with extensions like vlan_transparency present that was causing
issues in the base update function it was calling.

This corrects the behavior by having it only update the MTU, which
is the only thing it was intending to update in the first place.

Change-Id: I723c5c138e0830de98f6024c7635ec65065e9346
Closes-Bug: #1446784
(cherry picked from commit f85de393c4)

neutron/plugins/ml2/plugin.py

@@ -598,7 +598,7 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
 
             if net_data.get(api.MTU, 0) > 0:
                 res = super(Ml2Plugin, self).update_network(context,
-                    result['id'], network)
+                    result['id'], {'network': {api.MTU: net_data[api.MTU]}})
                 result[api.MTU] = res.get(api.MTU, 0)
 
         return result, mech_context

neutron/tests/unit/plugins/ml2/test_plugin.py

@@ -266,6 +266,28 @@ class TestMl2NetworksV2(test_plugin.TestNetworksV2,
             self.assertEqual(db_api.MAX_RETRIES + 1, f.call_count)
 
 
+class TestMl2NetworksWithVlanTransparencyAndMTU(TestMl2NetworksV2):
+    def setUp(self, plugin=None):
+        config.cfg.CONF.set_override('path_mtu', 1000, group='ml2')
+        config.cfg.CONF.set_override('segment_mtu', 1000, group='ml2')
+        config.cfg.CONF.set_override('advertise_mtu', True)
+        config.cfg.CONF.set_override('vlan_transparent', True)
+        super(TestMl2NetworksWithVlanTransparencyAndMTU, self).setUp(plugin)
+
+    def test_create_network_vlan_transparent_and_mtu(self):
+        data = {'network': {'name': 'net1',
+                            mpnet.SEGMENTS:
+                            [{pnet.NETWORK_TYPE: 'vlan',
+                              pnet.PHYSICAL_NETWORK: 'physnet1'}],
+                            'tenant_id': 'tenant_one'}}
+        network_req = self.new_create_request('networks', data)
+        res = network_req.get_response(self.api)
+        self.assertEqual(201, res.status_int)
+        network = self.deserialize(self.fmt, res)['network']
+        self.assertEqual(network['mtu'], 1000)
+        self.assertIn('vlan_transparent', network)
+
+
 class TestMl2SubnetsV2(test_plugin.TestSubnetsV2,
                        Ml2PluginV2TestCase):
     pass