Merge "Make add_tap_interface resillient to removal"

neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py

@@ -407,6 +407,22 @@ class LinuxBridgeManager(amb.CommonAgentManagerBase):
 
     def add_tap_interface(self, network_id, network_type, physical_network,
                           segmentation_id, tap_device_name, device_owner):
+        """Add tap interface and handle interface missing exeptions."""
+        try:
+            return self._add_tap_interface(network_id, network_type,
+                                           physical_network, segmentation_id,
+                                           tap_device_name, device_owner)
+        except Exception:
+            with excutils.save_and_reraise_exception() as ctx:
+                if not ip_lib.device_exists(tap_device_name):
+                    # the exception was likely a side effect of the tap device
+                    # being removed during handling so we just return false
+                    # like we would if it didn't exist to begin with.
+                    ctx.reraise = False
+                    return False
+
+    def _add_tap_interface(self, network_id, network_type, physical_network,
+                          segmentation_id, tap_device_name, device_owner):
         """Add tap interface.
 
         If a VIF has been plugged into a network, this function will

neutron/tests/unit/plugins/ml2/drivers/linuxbridge/agent/test_linuxbridge_neutron_agent.py

@@ -909,6 +909,23 @@ class TestLinuxBridgeManager(base.BaseTestCase):
                                                    "physnet9", "1")
                 self.assertEqual(1, log.call_count)
 
+    @mock.patch.object(ip_lib, "device_exists", return_value=False)
+    def test_add_tap_interface_with_interface_disappearing(self, exists):
+        with mock.patch.object(self.lbm, "_add_tap_interface",
+                               side_effect=RuntimeError("No such dev")):
+            self.assertFalse(self.lbm.add_tap_interface("123",
+                                                        p_const.TYPE_VLAN,
+                                                        "physnet1", None,
+                                                        "tap1", "foo"))
+
+    @mock.patch.object(ip_lib, "device_exists", return_value=True)
+    def test_add_tap_interface_with_other_error(self, exists):
+        with mock.patch.object(self.lbm, "_add_tap_interface",
+                               side_effect=RuntimeError("No more fuel")):
+            self.assertRaises(RuntimeError, self.lbm.add_tap_interface, "123",
+                              p_const.TYPE_VLAN, "physnet1", None, "tap1",
+                              "foo")
+
     def test_add_tap_interface_owner_other(self):
         with mock.patch.object(ip_lib, "device_exists"):
             with mock.patch.object(self.lbm, "ensure_local_bridge"):