DVS: provide a dhcp_driver class for plugin

Enable the plugin to override the base DHCP DeviceManager.

This patch does the following:
1. provide a class that overrides the default. This is required
   so that we can override the device_manager class
2. Introduces two new configuration variables:
    - dhcp_override_mac - enables the driver to override the
      neutron port mac address. This should be used when the DHCP
      agent is running on a VM that is connected to the DVS. This
      can save the admin the bother of setting 'forged transmits'
      to enable. This should be the MAC address of the VM
    - dvs_integration_bridge - the name of the bridge to plug the
      interface. This may be a dedicated bride that is connected
      to the DVS

This enables one to use the simple DVS plugin and actaully get a
DHCP address.

NOTE: a port group that can see all of the tags should be
configured. This is the port group that the dvs_integration_bridge
should be attached to.

DocImpact

Change-Id: I6b0742b363e551e09a8c44fd59c698a90d180efd
Depends-on: cee3664a77487750c2c5f68f1df97f3d80362e17

devstack/lib/vmware_dvs

@@ -81,6 +81,7 @@ function neutron_plugin_configure_dhcp_agent {
     iniset $Q_DHCP_CONF_FILE DEFAULT enable_isolated_metadata True
     iniset $Q_DHCP_CONF_FILE DEFAULT enable_metadata_network True
     iniset $Q_DHCP_CONF_FILE DEFAULT ovs_integration_bridge $OVS_BRIDGE
+    iniset $Q_DHCP_CONF_FILE DEFAULT dhcp_driver "vmware_nsx.plugins.dvs.dhcp.Dnsmasq"
 }
 
 function neutron_plugin_configure_l3_agent {

vmware_nsx/plugins/dvs/dhcp.py

@@ -0,0 +1,73 @@
+# Copyright 2012 OpenStack Foundation
+# 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 oslo_config import cfg
+from oslo_log import log as logging
+
+from neutron.agent.common import ovs_lib
+from neutron.agent.linux import dhcp
+
+LOG = logging.getLogger(__name__)
+
+OPTS = [
+    cfg.StrOpt('dvs_integration_bridge',
+               default='br-dvs',
+               help=_('Name of Open vSwitch bridge to use for DVS networks')),
+    cfg.StrOpt('dhcp_override_mac',
+               help=_('Override the MAC address of the DHCP interface')),
+]
+
+cfg.CONF.register_opts(OPTS)
+
+
+class DeviceManager(dhcp.DeviceManager):
+
+    def plug(self, network, port, interface_name):
+        mac_address = (cfg.CONF.dhcp_override_mac
+                       if cfg.CONF.dhcp_override_mac
+                       else port.mac_address)
+        self.driver.plug(network.id,
+                         port.id,
+                         interface_name,
+                         mac_address,
+                         namespace=network.namespace,
+                         mtu=network.get('mtu'),
+                         bridge=cfg.CONF.dvs_integration_bridge)
+        vlan_tag = getattr(network, 'provider:segmentation_id',
+                           None)
+        # Treat vlans
+        if vlan_tag and vlan_tag != 0:
+            br_dvs = ovs_lib.OVSBridge(self.conf.dvs_integration_bridge)
+            # When ovs_use_veth is set to True, the DEV_NAME_PREFIX
+            # will be changed from 'tap' to 'ns-' in
+            # OVSInterfaceDriver
+            dvs_port_name = interface_name.replace('ns-', 'tap')
+            br_dvs.set_db_attribute("Port", dvs_port_name, "tag", vlan_tag)
+
+    def unplug(self, device_name, network):
+        self.driver.unplug(
+            device_name, bridge=cfg.CONF.dvs_integration_bridge,
+            namespace=network.namespace)
+
+
+class Dnsmasq(dhcp.Dnsmasq):
+
+    def __init__(self, conf, network, process_monitor,
+                 version=None, plugin=None):
+        super(Dnsmasq, self).__init__(conf, network, process_monitor,
+                                      version=version, plugin=plugin)
+        # Using the DeviceManager that enables us to directly plug the OVS
+        LOG.debug("Using the DVS DeviceManager")
+        self.device_manager = DeviceManager(conf, plugin)