Rehome abstract class LinuxInterfaceDriver definition

This change will allow other third party plugins to inherit from this
class without importing Neutron but neutron-lib.

Change-Id: I29ff894a0da2df0c12aa6e90e8266e4d7aa30770
Related-Bug: #1879307

neutron_lib/agent/linux/interface.py

@@ -0,0 +1,31 @@
+#    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.
+
+import abc
+
+from neutron_lib import constants
+
+
+class LinuxInterfaceDriver(object, metaclass=abc.ABCMeta):
+
+    DEV_NAME_LEN = constants.LINUX_DEV_LEN
+    DEV_NAME_PREFIX = constants.TAP_DEVICE_PREFIX
+
+    @abc.abstractmethod
+    def plug_new(self, network_id, port_id, device_name, mac_address,
+                 bridge=None, namespace=None, prefix=None, mtu=None,
+                 link_up=True):
+        """Plug in the interface only for new devices that don't exist yet."""
+
+    @abc.abstractmethod
+    def unplug(self, device_name, bridge=None, namespace=None, prefix=None):
+        """Unplug the interface."""

releasenotes/notes/rehome-linuxinterfacedriver-874c5e17f2675eab.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - The abstract class LinuxInterfaceDriver is now defined in
+    ``neutron-lib.agent.linux.interface``. It contains only the
+    abstract methods and the class variables.