Support interface drivers that don't support mtu parameter for plug_new

The method signature before Mitaka did not have the mtu= parameter. We
should continue supporting the old signature, since it can be used in
out of tree interface drivers. The class is part of public neutron API,
so we should make an effort to not break out of tree code.

Change-Id: I8e0c07c76fd0b4c55b66c20ebe29cdb7c07d6f27
Closes-Bug: #1570392

neutron/agent/linux/interface.py

@@ -18,6 +18,7 @@ import abc
 import netaddr
 from oslo_config import cfg
 from oslo_log import log as logging
+from oslo_log import versionutils
 import six
 
 from neutron._i18n import _, _LE, _LI, _LW
@@ -245,8 +246,16 @@ class LinuxInterfaceDriver(object):
              bridge=None, namespace=None, prefix=None, mtu=None):
         if not ip_lib.device_exists(device_name,
                                     namespace=namespace):
-            self.plug_new(network_id, port_id, device_name, mac_address,
-                          bridge, namespace, prefix, mtu)
+            try:
+                self.plug_new(network_id, port_id, device_name, mac_address,
+                              bridge, namespace, prefix, mtu)
+            except TypeError:
+                versionutils.report_deprecated_feature(
+                    LOG,
+                    _LW('Interface driver does not support MTU parameter. '
+                        'This may not work in future releases.'))
+                self.plug_new(network_id, port_id, device_name, mac_address,
+                              bridge, namespace, prefix)
         else:
             LOG.info(_LI("Device %s already exists"), device_name)
 

neutron/tests/unit/agent/linux/test_interface.py

@@ -14,6 +14,7 @@
 #    under the License.
 
 import mock
+from oslo_log import versionutils
 import testtools
 
 from neutron.agent.common import config
@@ -55,6 +56,23 @@ class FakePort(object):
     network_id = network.id
 
 
+class FakeInterfaceDriverNoMtu(interface.LinuxInterfaceDriver):
+    # NOTE(ihrachys) this method intentially omit mtu= parameter, since that
+    # was the method signature before Mitaka. We should make sure the old
+    # signature still works.
+
+    def __init__(self, *args, **kwargs):
+        super(FakeInterfaceDriverNoMtu, self).__init__(*args, **kwargs)
+        self.plug_called = False
+
+    def plug_new(self, network_id, port_id, device_name, mac_address,
+                 bridge=None, namespace=None, prefix=None):
+        self.plug_called = True
+
+    def unplug(self, device_name, bridge=None, namespace=None, prefix=None):
+        pass
+
+
 class TestBase(base.BaseTestCase):
     def setUp(self):
         super(TestBase, self).setUp()
@@ -68,6 +86,19 @@ class TestBase(base.BaseTestCase):
         self.device_exists = self.device_exists_p.start()
 
 
+class TestABCDriverNoMtu(TestBase):
+
+    def test_plug_with_no_mtu_works(self):
+        driver = FakeInterfaceDriverNoMtu(self.conf)
+        self.device_exists.return_value = False
+        with mock.patch.object(
+                versionutils, 'report_deprecated_feature') as report:
+            driver.plug(
+                mock.Mock(), mock.Mock(), mock.Mock(), mock.Mock(), mtu=9000)
+        self.assertTrue(driver.plug_called)
+        self.assertTrue(report.called)
+
+
 class TestABCDriver(TestBase):
     def setUp(self):
         super(TestABCDriver, self).setUp()