Override MTU for os_vif attachments

os-vif does not current respect the neutron provided mtu, it just uses
the configuration inside os-vif. This is a big regression from mitaka
and liberty.

Long term, this is something os-vif will be able to do by correctly
parsing and acting on the network info. For now we just set the mtu for
a second time once os-vif has done what it wants to do.

Closes-Bug: #1623876

Change-Id: Id4ca38fa1bb84f8cdb5edcd9ccb7acd8c8e9b60c

nova/tests/unit/virt/libvirt/test_vif.py

@@ -12,6 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
 import os
 
 import fixtures
@@ -1598,3 +1599,40 @@ def test_config_os_vif_ovs_hybrid(self, mock_convert_vif,
                 <filterref
                  filter="nova-instance-instance-00000001-22522562e2aa"/>
             </interface>""", cfg.to_xml())
+
+    @mock.patch('nova.network.linux_net._set_device_mtu')
+    @mock.patch("nova.network.os_vif_util.nova_to_osvif_instance")
+    @mock.patch("nova.network.os_vif_util.nova_to_osvif_vif")
+    @mock.patch.object(os_vif, "plug")
+    def test_plug_ovs_vif_no_mtu(self, mock_plug,
+                              mock_convert_vif, mock_convert_inst,
+                              mock_set_mtu):
+        mock_convert_vif.return_value = self.os_vif_bridge
+        mock_convert_inst.return_value = self.os_vif_inst_info
+
+        d = vif.LibvirtGenericVIFDriver()
+        # Hack the network mtu in the vif_bridge object - make sure to copy it
+        # so we don't change state on a global object during a test run.
+        vif_bridge = copy.deepcopy(self.vif_bridge)
+        vif_bridge['network']._set_meta({'mtu': None})
+        d.plug(self.instance, vif_bridge)
+
+        self.assertFalse(mock_set_mtu.called)
+
+    @mock.patch('nova.network.linux_net._set_device_mtu')
+    @mock.patch("nova.network.os_vif_util.nova_to_osvif_instance")
+    @mock.patch("nova.network.os_vif_util.nova_to_osvif_vif")
+    @mock.patch.object(os_vif, "plug")
+    def test_plug_ovs_vif_mtu(self, mock_plug,
+                              mock_convert_vif, mock_convert_inst,
+                              mock_set_mtu):
+        mock_convert_vif.return_value = self.os_vif_ovs
+        mock_convert_inst.return_value = self.os_vif_inst_info
+
+        d = vif.LibvirtGenericVIFDriver()
+        d.plug(self.instance, self.vif_ovs)
+
+        mock_set_mtu.assert_any_call("br0", 1000)
+        mock_set_mtu.assert_any_call("qvbdc065497-3c", 1000)
+        mock_set_mtu.assert_any_call("qvodc065497-3c", 1000)
+        self.assertEqual(3, mock_set_mtu.call_count)

nova/virt/libvirt/vif.py

@@ -772,7 +772,7 @@ def plug_vrouter(self, instance, vif):
         except processutils.ProcessExecutionError:
             LOG.exception(_LE("Failed while plugging vif"), instance=instance)
 
-    def _plug_os_vif(self, instance, vif):
+    def _plug_os_vif(self, instance, vif, raw_vif):
         instance_info = os_vif_util.nova_to_osvif_instance(instance)
 
         try:
@@ -782,6 +782,22 @@ def _plug_os_vif(self, instance, vif):
                    % {'ex': ex})
             raise exception.NovaException(msg)
 
+        # TODO(johngarbutt) remove this hack once 1623876 is fixed in os-vif
+        network = raw_vif.get('network')
+        mtu = network.get_meta('mtu') if network else None
+        if mtu is not None:
+            linux_net._set_device_mtu(network["bridge"], mtu)
+
+        if (isinstance(vif, os_vif.objects.vif.VIFBridge) and
+            hasattr(vif, "port_profile") and
+            isinstance(vif.port_profile,
+                       os_vif.objects.vif.VIFPortProfileOpenVSwitch)):
+            veths = [
+                ("qvb%s" % vif.id)[:network_model.NIC_NAME_LEN],
+                ("qvo%s" % vif.id)[:network_model.NIC_NAME_LEN]]
+            for veth in veths:
+                linux_net._set_device_mtu(veth, mtu)
+
     def plug(self, instance, vif):
         vif_type = vif['type']
 
@@ -798,7 +814,7 @@ def plug(self, instance, vif):
         # Try os-vif codepath first
         vif_obj = os_vif_util.nova_to_osvif_vif(vif)
         if vif_obj is not None:
-            self._plug_os_vif(instance, vif_obj)
+            self._plug_os_vif(instance, vif_obj, vif)
             return
 
         # Legacy non-os-vif codepath