macvtap: Common functions and constants

Functions and constants that are shared between the macvtap ml2 driver
and the macvtap agent.

The review is submitted in three parts:
 - Part 1 (this part)
    Common functions that are used by the ml2 driver and the agent
 - Part 2
     The Mechanism Driver to support port binding for macvtap attachments
 - Part 3
    The Macvtap L2 Agent.

Partial-Bug: #1480979

Change-Id: I63a095e6f592b94372ff018f2e73373ad9414d99

neutron/common/constants.py

@@ -42,6 +42,7 @@ MINIMUM_AGENTS_FOR_HA = 2
 HA_ROUTER_STATE_ACTIVE = 'active'
 HA_ROUTER_STATE_STANDBY = 'standby'
 
+AGENT_TYPE_MACVTAP = 'Macvtap agent'
 PAGINATION_INFINITE = 'infinite'
 
 SORT_DIRECTION_ASC = 'asc'

neutron/plugins/ml2/drivers/macvtap/macvtap_common.py

@@ -0,0 +1,30 @@
+# Copyright (c) 2016 IBM Corp.
+#
+# All Rights Reserved.
+#
+#    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.
+
+from neutron.common import constants as n_const
+from neutron.plugins.common import utils as p_utils
+
+MAX_VLAN_POSTFIX_LEN = 5
+
+
+def get_vlan_device_name(src_dev, vlan):
+    """Generating the vlan device name."""
+
+    # Ensure that independent of the vlan len the same name prefix is used.
+    src_dev = p_utils.get_interface_name(src_dev,
+                                         max_len=n_const.DEVICE_NAME_MAX_LEN -
+                                         MAX_VLAN_POSTFIX_LEN)
+    return "%s.%s" % (src_dev, vlan)

neutron/tests/unit/plugins/ml2/drivers/macvtap/test_macvtap_common.py

@@ -0,0 +1,60 @@
+# Copyright (c) 2016 IBM Corp.
+#
+# All Rights Reserved.
+#
+#    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 hashlib
+import mock
+
+from neutron.plugins.ml2.drivers.macvtap import macvtap_common as m_common
+from neutron.tests import base
+
+MOCKED_HASH = "MOCKEDHASH"
+
+
+class MockSHA(object):
+    def hexdigest(self):
+        return MOCKED_HASH
+
+
+class MacvtapCommonTestCase(base.BaseTestCase):
+    @mock.patch.object(hashlib, 'sha1', return_value=MockSHA())
+    def test_get_vlan_device_name(self, mocked_hash):
+        # only the first six chars of the hash are being used in the algorithm
+        hash_used = MOCKED_HASH[0:6]
+        self.assertEqual('10charrrrr.1',
+                         m_common.get_vlan_device_name('10charrrrr', "1"))
+        self.assertEqual('11ch' + hash_used + '.1',
+                         m_common.get_vlan_device_name('11charrrrrr', "1"))
+        self.assertEqual('14ch' + hash_used + '.1',
+                         m_common.get_vlan_device_name('14charrrrrrrrr', "1"))
+        self.assertEqual('14ch' + hash_used + '.1111',
+                         m_common.get_vlan_device_name('14charrrrrrrrr',
+                                                       "1111"))
+
+    def test_get_vlan_subinterface_name_advanced(self):
+        """Ensure the same hash is used for long interface names.
+
+        If the generated vlan device name would be too long, make sure that
+        everything before the '.' is equal. This might be helpful when
+        debugging problems.
+        """
+
+        max_device_name = "15charrrrrrrrrr"
+        vlan_dev_name1 = m_common.get_vlan_device_name(max_device_name,
+                                                       "1")
+        vlan_dev_name2 = m_common.get_vlan_device_name(max_device_name,
+                                                       "1111")
+        self.assertEqual(vlan_dev_name1.partition(".")[0],
+                         vlan_dev_name2.partition(".")[0])