text: # Copyright (c) 2013 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 neutron_lib.api.definitions import external_net as extnet_apidef
  from neutron_lib.api.definitions import portbindings
  from neutron_lib.api.definitions import provider_net as provider
  from neutron_lib.api import validators
  from neutron_lib import constants
  from neutron_lib import exceptions as exc
  from neutron_lib.plugins.ml2 import api
  from oslo_config import cfg
  from oslo_log import log
  from oslo_utils import excutils
  import stevedore
  
  from neutron._i18n import _
  from neutron.conf.plugins.ml2 import config
  from neutron.db import api as db_api
  from neutron.db import segments_db
  from neutron.extensions import multiprovidernet as mpnet
  from neutron.extensions import vlantransparent
  from neutron.plugins.ml2.common import exceptions as ml2_exc
  from neutron.plugins.ml2 import models
  
  LOG = log.getLogger(__name__)
  
  MAX_BINDING_LEVELS = 10
  config.register_ml2_plugin_opts()
  
  
  class TypeManager(stevedore.named.NamedExtensionManager):
      """Manage network segment types using drivers."""
  
      def __init__(self):
          # Mapping from type name to DriverManager
          self.drivers = {}
  
          LOG.info("Configured type driver names: %s",
                   cfg.CONF.ml2.type_drivers)
          super(TypeManager, self).__init__('neutron.ml2.type_drivers',
                                            cfg.CONF.ml2.type_drivers,
                                            invoke_on_load=True)
          LOG.info("Loaded type driver names: %s", self.names())
          self._register_types()
          self._check_tenant_network_types(cfg.CONF.ml2.tenant_network_types)
          self._check_external_network_type(cfg.CONF.ml2.external_network_type)
  
      def _register_types(self):
          for ext in self:
              network_type = ext.obj.get_type()
              if network_type in self.drivers:
                  LOG.error("Type driver '%(new_driver)s' ignored because"
                            " type driver '%(old_driver)s' is already"
                            " registered for type '%(type)s'",
                            {'new_driver': ext.name,
                             'old_driver': self.drivers[network_type].name,
                             'type': network_type})
              else:
                  self.drivers[network_type] = ext
          LOG.info("Registered types: %s", self.drivers.keys())
  
      def _check_tenant_network_types(self, types):
          self.tenant_network_types = []
          for network_type in types:
              if network_type in self.drivers:
                  self.tenant_network_types.append(network_type)
              else:
                  LOG.error("No type driver for tenant network_type: %s. "
                            "Service terminated!", network_type)
                  raise SystemExit(1)
          LOG.info("Tenant network_types: %s", self.tenant_network_types)
  
      def _check_external_network_type(self, ext_network_type):
          if ext_network_type and ext_network_type not in self.drivers:
              LOG.error("No type driver for external network_type: %s. "
                        "Service terminated!", ext_network_type)
              raise SystemExit(1)
  
      def _process_provider_segment(self, segment):
          (network_type, physical_network,
           segmentation_id) = (self._get_attribute(segment, attr)
                               for attr in provider.ATTRIBUTES)
  
          if validators.is_attr_set(network_type):
              segment = {api.NETWORK_TYPE: network_type,
                         api.PHYSICAL_NETWORK: physical_network,
                         api.SEGMENTATION_ID: segmentation_id}
              self.validate_provider_segment(segment)
              return segment
  
          msg = _("network_type required")
          raise exc.InvalidInput(error_message=msg)
  
      def _process_provider_create(self, network):
          if any(validators.is_attr_set(network.get(attr))
                 for attr in provider.ATTRIBUTES):
              # Verify that multiprovider and provider attributes are not set
              # at the same time.
              if validators.is_attr_set(network.get(mpnet.SEGMENTS)):
                  raise mpnet.SegmentsSetInConjunctionWithProviders()
              segment = self._get_provider_segment(network)
              return [self._process_provider_segment(segment)]
          elif validators.is_attr_set(network.get(mpnet.SEGMENTS)):
              segments = [self._process_provider_segment(s)
                          for s in network[mpnet.SEGMENTS]]
              mpnet.check_duplicate_segments(segments, self.is_partial_segment)
              return segments
  
      def _match_segment(self, segment, filters):
          return all(not filters.get(attr) or segment.get(attr) in filters[attr]
                     for attr in provider.ATTRIBUTES)
  
      def _get_provider_segment(self, network):
          # TODO(manishg): Placeholder method
          # Code intended for operating on a provider segment should use
          # this method to extract the segment, even though currently the
          # segment attributes are part of the network dictionary. In the
          # future, network and segment information will be decoupled and
          # here we will do the job of extracting the segment information.
          return network
  
      def network_matches_filters(self, network, filters):
          if not filters:
              return True
          if any(validators.is_attr_set(network.get(attr))
                 for attr in provider.ATTRIBUTES):
              segments = [self._get_provider_segment(network)]
          elif validators.is_attr_set(network.get(mpnet.SEGMENTS)):
              segments = self._get_attribute(network, mpnet.SEGMENTS)
          else:
              return True
          return any(self._match_segment(s, filters) for s in segments)
  
      def _get_attribute(self, attrs, key):
          value = attrs.get(key)
          if value is constants.ATTR_NOT_SPECIFIED:
              value = None
          return value
  
      def extend_network_dict_provider(self, context, network):
          # this method is left for backward compat even though it would be
          # easy to change the callers in tree to use the bulk function
          return self.extend_networks_dict_provider(context, [network])
  
      def extend_networks_dict_provider(self, context, networks):
          ids = [network['id'] for network in networks]
          net_segments = segments_db.get_networks_segments(context, ids)
          for network in networks:
              segments = net_segments[network['id']]
              self._extend_network_dict_provider(network, segments)
  
      def _extend_network_dict_provider(self, network, segments):
          if not segments:
              LOG.debug("Network %s has no segments", network['id'])
              for attr in provider.ATTRIBUTES:
                  network[attr] = None
          elif len(segments) > 1:
              network[mpnet.SEGMENTS] = [
                  {provider.NETWORK_TYPE: segment[api.NETWORK_TYPE],
                   provider.PHYSICAL_NETWORK: segment[api.PHYSICAL_NETWORK],
                   provider.SEGMENTATION_ID: segment[api.SEGMENTATION_ID]}
                  for segment in segments]
          else:
              segment = segments[0]
              network[provider.NETWORK_TYPE] = segment[api.NETWORK_TYPE]
              network[provider.PHYSICAL_NETWORK] = segment[
                  api.PHYSICAL_NETWORK]
              network[provider.SEGMENTATION_ID] = segment[
                  api.SEGMENTATION_ID]
  
      def initialize(self):
          for network_type, driver in self.drivers.items():
              LOG.info("Initializing driver for type '%s'", network_type)
              driver.obj.initialize()
  
      def _add_network_segment(self, context, network_id, segment,
                               segment_index=0):
          segments_db.add_network_segment(
              context, network_id, segment, segment_index)
  
      def create_network_segments(self, context, network, tenant_id):
          """Call type drivers to create network segments."""
          segments = self._process_provider_create(network)
          with db_api.context_manager.writer.using(context):
              network_id = network['id']
              if segments:
                  for segment_index, segment in enumerate(segments):
                      segment = self.reserve_provider_segment(
                          context, segment)
                      self._add_network_segment(context, network_id, segment,
                                                segment_index)
              elif (cfg.CONF.ml2.external_network_type and
                    self._get_attribute(network, extnet_apidef.EXTERNAL)):
                  segment = self._allocate_ext_net_segment(context)
                  self._add_network_segment(context, network_id, segment)
              else:
                  segment = self._allocate_tenant_net_segment(context)
                  self._add_network_segment(context, network_id, segment)
  
      def reserve_network_segment(self, context, segment_data):
          """Call type drivers to reserve a network segment."""
          # Validate the data of segment
          if not validators.is_attr_set(segment_data[api.NETWORK_TYPE]):
              msg = _("network_type required")
              raise exc.InvalidInput(error_message=msg)
  
          net_type = self._get_attribute(segment_data, api.NETWORK_TYPE)
          phys_net = self._get_attribute(segment_data, api.PHYSICAL_NETWORK)
          seg_id = self._get_attribute(segment_data, api.SEGMENTATION_ID)
          segment = {api.NETWORK_TYPE: net_type,
                     api.PHYSICAL_NETWORK: phys_net,
                     api.SEGMENTATION_ID: seg_id}
  
          self.validate_provider_segment(segment)
  
          # Reserve segment in type driver
          with db_api.context_manager.writer.using(context):
              return self.reserve_provider_segment(context, segment)
  
      def is_partial_segment(self, segment):
          network_type = segment[api.NETWORK_TYPE]
          driver = self.drivers.get(network_type)
          if driver:
              return driver.obj.is_partial_segment(segment)
          else:
              msg = _("network_type value '%s' not supported") % network_type
              raise exc.InvalidInput(error_message=msg)
  
      def validate_provider_segment(self, segment):
          network_type = segment[api.NETWORK_TYPE]
          driver = self.drivers.get(network_type)
          if driver:
              driver.obj.validate_provider_segment(segment)
          else:
              msg = _("network_type value '%s' not supported") % network_type
              raise exc.InvalidInput(error_message=msg)
  
      def reserve_provider_segment(self, context, segment):
          network_type = segment.get(api.NETWORK_TYPE)
          driver = self.drivers.get(network_type)
          if isinstance(driver.obj, api.TypeDriver):
              return driver.obj.reserve_provider_segment(context.session,
                                                         segment)
          else:
              return driver.obj.reserve_provider_segment(context,
                                                         segment)
  
      def _allocate_segment(self, context, network_type):
          driver = self.drivers.get(network_type)
          if isinstance(driver.obj, api.TypeDriver):
              return driver.obj.allocate_tenant_segment(context.session)
          else:
              return driver.obj.allocate_tenant_segment(context)
  
      def _allocate_tenant_net_segment(self, context):
          for network_type in self.tenant_network_types:
              segment = self._allocate_segment(context, network_type)
              if segment:
                  return segment
          raise exc.NoNetworkAvailable()
  
      def _allocate_ext_net_segment(self, context):
          network_type = cfg.CONF.ml2.external_network_type
          segment = self._allocate_segment(context, network_type)
          if segment:
              return segment
          raise exc.NoNetworkAvailable()
  
      def release_network_segments(self, context, network_id):
          segments = segments_db.get_network_segments(context, network_id,
                                                      filter_dynamic=None)
  
          for segment in segments:
              self.release_network_segment(context, segment)
  
      def release_network_segment(self, context, segment):
          network_type = segment.get(api.NETWORK_TYPE)
          driver = self.drivers.get(network_type)
          if driver:
              if isinstance(driver.obj, api.TypeDriver):
                  driver.obj.release_segment(context.session, segment)
              else:
                  driver.obj.release_segment(context, segment)
          else:
              LOG.error("Failed to release segment '%s' because "
                        "network type is not supported.", segment)
  
      def allocate_dynamic_segment(self, context, network_id, segment):
          """Allocate a dynamic segment using a partial or full segment dict."""
          dynamic_segment = segments_db.get_dynamic_segment(
              context, network_id, segment.get(api.PHYSICAL_NETWORK),
              segment.get(api.SEGMENTATION_ID))
  
          if dynamic_segment:
              return dynamic_segment
  
          driver = self.drivers.get(segment.get(api.NETWORK_TYPE))
          if isinstance(driver.obj, api.TypeDriver):
              dynamic_segment = driver.obj.reserve_provider_segment(
                  context.session, segment)
          else:
              dynamic_segment = driver.obj.reserve_provider_segment(
                  context, segment)
          segments_db.add_network_segment(context, network_id, dynamic_segment,
                                          is_dynamic=True)
          return dynamic_segment
  
      def release_dynamic_segment(self, context, segment_id):
          """Delete a dynamic segment."""
          segment = segments_db.get_segment_by_id(context, segment_id)
          if segment:
              driver = self.drivers.get(segment.get(api.NETWORK_TYPE))
              if driver:
                  if isinstance(driver.obj, api.TypeDriver):
                      driver.obj.release_segment(context.session, segment)
                  else:
                      driver.obj.release_segment(context, segment)
                  segments_db.delete_network_segment(context, segment_id)
              else:
                  LOG.error("Failed to release segment '%s' because "
                            "network type is not supported.", segment)
          else:
              LOG.debug("No segment found with id %(segment_id)s", segment_id)
  
  
  class MechanismManager(stevedore.named.NamedExtensionManager):
      """Manage networking mechanisms using drivers."""
  
      def __init__(self):
          # Registered mechanism drivers, keyed by name.
          self.mech_drivers = {}
          # Ordered list of mechanism drivers, defining
          # the order in which the drivers are called.
          self.ordered_mech_drivers = []
  
          LOG.info("Configured mechanism driver names: %s",
                   cfg.CONF.ml2.mechanism_drivers)
          super(MechanismManager, self).__init__(
              'neutron.ml2.mechanism_drivers',
              cfg.CONF.ml2.mechanism_drivers,
              invoke_on_load=True,
              name_order=True,
              on_missing_entrypoints_callback=self._driver_not_found,
              on_load_failure_callback=self._driver_not_loaded
          )
          LOG.info("Loaded mechanism driver names: %s", self.names())
          self._register_mechanisms()
          self.host_filtering_supported = self.is_host_filtering_supported()
          if not self.host_filtering_supported:
              LOG.info("No mechanism drivers provide segment reachability "
                       "information for agent scheduling.")
  
      def _driver_not_found(self, names):
          msg = (_("The following mechanism drivers were not found: %s")
                 % names)
          LOG.critical(msg)
          raise SystemExit(msg)
  
      def _driver_not_loaded(self, manager, entrypoint, exception):
          LOG.critical("The '%(entrypoint)s' entrypoint could not be"
                       " loaded for the following reason: '%(reason)s'.",
                       {'entrypoint': entrypoint,
                        'reason': exception})
          raise SystemExit(str(exception))
  
      def _register_mechanisms(self):
          """Register all mechanism drivers.
  
          This method should only be called once in the MechanismManager
          constructor.
          """
          for ext in self:
              self.mech_drivers[ext.name] = ext
              self.ordered_mech_drivers.append(ext)
          LOG.info("Registered mechanism drivers: %s",
                   [driver.name for driver in self.ordered_mech_drivers])
  
      def initialize(self):
          for driver in self.ordered_mech_drivers:
              LOG.info("Initializing mechanism driver '%s'", driver.name)
              driver.obj.initialize()
  
      def _check_vlan_transparency(self, context):
          """Helper method for checking vlan transparecncy support.
  
          :param context: context parameter to pass to each method call
          :raises: neutron.extensions.vlantransparent.
          VlanTransparencyDriverError if any mechanism driver doesn't
          support vlan transparency.
          """
          if context.current.get('vlan_transparent'):
              for driver in self.ordered_mech_drivers:
                  if not driver.obj.check_vlan_transparency(context):
                      raise vlantransparent.VlanTransparencyDriverError()
  
      def _call_on_drivers(self, method_name, context,
                           continue_on_failure=False, raise_db_retriable=False):
          """Helper method for calling a method across all mechanism drivers.
  
          :param method_name: name of the method to call
          :param context: context parameter to pass to each method call
          :param continue_on_failure: whether or not to continue to call
          all mechanism drivers once one has raised an exception
          :param raise_db_retriable: whether or not to treat retriable db
          exception by mechanism drivers to propagate up to upper layer so
          that upper layer can handle it or error in ML2 player
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver call fails. or DB retriable error when
          raise_db_retriable=False. See neutron.db.api.is_retriable for
          what db exception is retriable
          """
          errors = []
          for driver in self.ordered_mech_drivers:
              try:
                  getattr(driver.obj, method_name)(context)
              except Exception as e:
                  if raise_db_retriable and db_api.is_retriable(e):
                      with excutils.save_and_reraise_exception():
                          LOG.debug("DB exception raised by Mechanism driver "
                                    "'%(name)s' in %(method)s",
                                    {'name': driver.name, 'method': method_name},
                                    exc_info=e)
                  LOG.exception(
                      "Mechanism driver '%(name)s' failed in %(method)s",
                      {'name': driver.name, 'method': method_name}
                  )
                  errors.append(e)
                  if not continue_on_failure:
                      break
          if errors:
              raise ml2_exc.MechanismDriverError(
                  method=method_name,
                  errors=errors
              )
  
      def create_network_precommit(self, context):
          """Notify all mechanism drivers during network creation.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver create_network_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._check_vlan_transparency(context)
          self._call_on_drivers("create_network_precommit", context,
                                raise_db_retriable=True)
  
      def create_network_postcommit(self, context):
          """Notify all mechanism drivers after network creation.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver create_network_postcommit call fails.
  
          Called after the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, where the network will be deleted, triggering
          any required cleanup. There is no guarantee that all mechanism
          drivers are called in this case.
          """
          self._call_on_drivers("create_network_postcommit", context)
  
      def update_network_precommit(self, context):
          """Notify all mechanism drivers during network update.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver update_network_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("update_network_precommit", context,
                                raise_db_retriable=True)
  
      def update_network_postcommit(self, context):
          """Notify all mechanism drivers after network update.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver update_network_postcommit call fails.
  
          Called after the database transaction. If any mechanism driver
          raises an error, then the error is logged but we continue to
          call every other mechanism driver. A MechanismDriverError is
          then reraised at the end to notify the caller of a failure.
          """
          self._call_on_drivers("update_network_postcommit", context,
                                continue_on_failure=True)
  
      def delete_network_precommit(self, context):
          """Notify all mechanism drivers during network deletion.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver delete_network_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("delete_network_precommit", context,
                                raise_db_retriable=True)
  
      def delete_network_postcommit(self, context):
          """Notify all mechanism drivers after network deletion.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver delete_network_postcommit call fails.
  
          Called after the database transaction. If any mechanism driver
          raises an error, then the error is logged but we continue to
          call every other mechanism driver. A MechanismDriverError is
          then reraised at the end to notify the caller of a failure. In
          general we expect the caller to ignore the error, as the
          network resource has already been deleted from the database
          and it doesn't make sense to undo the action by recreating the
          network.
          """
          self._call_on_drivers("delete_network_postcommit", context,
                                continue_on_failure=True)
  
      def create_subnet_precommit(self, context):
          """Notify all mechanism drivers during subnet creation.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver create_subnet_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("create_subnet_precommit", context,
                                raise_db_retriable=True)
  
      def create_subnet_postcommit(self, context):
          """Notify all mechanism drivers after subnet creation.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver create_subnet_postcommit call fails.
  
          Called after the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, where the subnet will be deleted, triggering
          any required cleanup. There is no guarantee that all mechanism
          drivers are called in this case.
          """
          self._call_on_drivers("create_subnet_postcommit", context)
  
      def update_subnet_precommit(self, context):
          """Notify all mechanism drivers during subnet update.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver update_subnet_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("update_subnet_precommit", context,
                                raise_db_retriable=True)
  
      def update_subnet_postcommit(self, context):
          """Notify all mechanism drivers after subnet update.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver update_subnet_postcommit call fails.
  
          Called after the database transaction. If any mechanism driver
          raises an error, then the error is logged but we continue to
          call every other mechanism driver. A MechanismDriverError is
          then reraised at the end to notify the caller of a failure.
          """
          self._call_on_drivers("update_subnet_postcommit", context,
                                continue_on_failure=True)
  
      def delete_subnet_precommit(self, context):
          """Notify all mechanism drivers during subnet deletion.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver delete_subnet_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("delete_subnet_precommit", context,
                                raise_db_retriable=True)
  
      def delete_subnet_postcommit(self, context):
          """Notify all mechanism drivers after subnet deletion.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver delete_subnet_postcommit call fails.
  
          Called after the database transaction. If any mechanism driver
          raises an error, then the error is logged but we continue to
          call every other mechanism driver. A MechanismDriverError is
          then reraised at the end to notify the caller of a failure. In
          general we expect the caller to ignore the error, as the
          subnet resource has already been deleted from the database
          and it doesn't make sense to undo the action by recreating the
          subnet.
          """
          self._call_on_drivers("delete_subnet_postcommit", context,
                                continue_on_failure=True)
  
      def create_port_precommit(self, context):
          """Notify all mechanism drivers during port creation.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver create_port_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("create_port_precommit", context,
                                raise_db_retriable=True)
  
      def create_port_postcommit(self, context):
          """Notify all mechanism drivers of port creation.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver create_port_postcommit call fails.
  
          Called after the database transaction. Errors raised by
          mechanism drivers are left to propagate to the caller, where
          the port will be deleted, triggering any required
          cleanup. There is no guarantee that all mechanism drivers are
          called in this case.
          """
          self._call_on_drivers("create_port_postcommit", context)
  
      def update_port_precommit(self, context):
          """Notify all mechanism drivers during port update.
  
          :raises: DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver update_port_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("update_port_precommit", context,
                                raise_db_retriable=True)
  
      def update_port_postcommit(self, context):
          """Notify all mechanism drivers after port update.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver update_port_postcommit call fails.
  
          Called after the database transaction. If any mechanism driver
          raises an error, then the error is logged but we continue to
          call every other mechanism driver. A MechanismDriverError is
          then reraised at the end to notify the caller of a failure.
          """
          self._call_on_drivers("update_port_postcommit", context,
                                continue_on_failure=True)
  
      def delete_port_precommit(self, context):
          """Notify all mechanism drivers during port deletion.
  
          :raises:DB retriable error if create_network_precommit raises them
          See neutron.db.api.is_retriable for what db exception is retriable
          or neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver delete_port_precommit call fails.
  
          Called within the database transaction. If a mechanism driver
          raises an exception, then a MechanismDriverError is propagated
          to the caller, triggering a rollback. There is no guarantee
          that all mechanism drivers are called in this case.
          """
          self._call_on_drivers("delete_port_precommit", context,
                                raise_db_retriable=True)
  
      def delete_port_postcommit(self, context):
          """Notify all mechanism drivers after port deletion.
  
          :raises: neutron.plugins.ml2.common.MechanismDriverError
          if any mechanism driver delete_port_postcommit call fails.
  
          Called after the database transaction. If any mechanism driver
          raises an error, then the error is logged but we continue to
          call every other mechanism driver. A MechanismDriverError is
          then reraised at the end to notify the caller of a failure. In
          general we expect the caller to ignore the error, as the
          port resource has already been deleted from the database
          and it doesn't make sense to undo the action by recreating the
          port.
          """
          self._call_on_drivers("delete_port_postcommit", context,
                                continue_on_failure=True)
  
      def bind_port(self, context):
          """Attempt to bind a port using registered mechanism drivers.
  
          :param context: PortContext instance describing the port
  
          Called outside any transaction to attempt to establish a port
          binding.
          """
          binding = context._binding
          LOG.debug("Attempting to bind port %(port)s on host %(host)s "
                    "for vnic_type %(vnic_type)s with profile %(profile)s",
                    {'port': context.current['id'],
                     'host': context.host,
                     'vnic_type': binding.vnic_type,
                     'profile': binding.profile})
          context._clear_binding_levels()
          if not self._bind_port_level(context, 0,
                                       context.network.network_segments):
              binding.vif_type = portbindings.VIF_TYPE_BINDING_FAILED
              LOG.error("Failed to bind port %(port)s on host %(host)s "
                        "for vnic_type %(vnic_type)s using segments "
                        "%(segments)s",
                        {'port': context.current['id'],
                         'host': context.host,
                         'vnic_type': binding.vnic_type,
                         'segments': context.network.network_segments})
  
      def _bind_port_level(self, context, level, segments_to_bind):
          binding = context._binding
          port_id = context.current['id']
          LOG.debug("Attempting to bind port %(port)s on host %(host)s "
                    "at level %(level)s using segments %(segments)s",
                    {'port': port_id,
                     'host': context.host,
                     'level': level,
                     'segments': segments_to_bind})
  
          if level == MAX_BINDING_LEVELS:
              LOG.error("Exceeded maximum binding levels attempting to bind "
                        "port %(port)s on host %(host)s",
                        {'port': context.current['id'],
                         'host': context.host})
              return False
  
          for driver in self.ordered_mech_drivers:
              if not self._check_driver_to_bind(driver, segments_to_bind,
                                                context._binding_levels):
                  continue
              try:
                  context._prepare_to_bind(segments_to_bind)
                  driver.obj.bind_port(context)
                  segment = context._new_bound_segment
                  if segment:
                      context._push_binding_level(
                          models.PortBindingLevel(port_id=port_id,
                                                  host=context.host,
                                                  level=level,
                                                  driver=driver.name,
                                                  segment_id=segment))
                      next_segments = context._next_segments_to_bind
                      if next_segments:
                          # Continue binding another level.
                          if self._bind_port_level(context, level + 1,
                                                   next_segments):
                              return True
                          else:
                              LOG.warning("Failed to bind port %(port)s on "
                                          "host %(host)s at level %(lvl)s",
                                          {'port': context.current['id'],
                                           'host': context.host,
                                           'lvl': level + 1})
                              context._pop_binding_level()
                      else:
                          # Binding complete.
                          LOG.debug("Bound port: %(port)s, "
                                    "host: %(host)s, "
                                    "vif_type: %(vif_type)s, "
                                    "vif_details: %(vif_details)s, "
                                    "binding_levels: %(binding_levels)s",
                                    {'port': port_id,
                                     'host': context.host,
                                     'vif_type': binding.vif_type,
                                     'vif_details': binding.vif_details,
                                     'binding_levels': context.binding_levels})
                          return True
              except Exception:
                  LOG.exception("Mechanism driver %s failed in "
                                "bind_port",
                                driver.name)
  
      def is_host_filtering_supported(self):
          return all(driver.obj.is_host_filtering_supported()
                     for driver in self.ordered_mech_drivers)
  
      def filter_hosts_with_segment_access(
              self, context, segments, candidate_hosts, agent_getter):
          """Filter hosts with access to at least one segment.
  
          :returns: a subset of candidate_hosts.
  
          This method returns all hosts from candidate_hosts with access to a
          segment according to at least one driver.
          """
          candidate_hosts = set(candidate_hosts)
          if not self.host_filtering_supported:
              return candidate_hosts
  
          hosts_with_access = set()
          for driver in self.ordered_mech_drivers:
              hosts = driver.obj.filter_hosts_with_segment_access(
                  context, segments, candidate_hosts, agent_getter)
              hosts_with_access |= hosts
              candidate_hosts -= hosts
              if not candidate_hosts:
                  break
          return hosts_with_access
  
      def _check_driver_to_bind(self, driver, segments_to_bind, binding_levels):
          # To prevent a possible binding loop, don't try to bind with
          # this driver if the same driver has already bound at a higher
          # level to one of the segments we are currently trying to
          # bind. Note that it is OK for the same driver to bind at
          # multiple levels using different segments.
          segment_ids_to_bind = {s[api.SEGMENTATION_ID]
                                 for s in segments_to_bind}
          for level in binding_levels:
              if (level.driver == driver.name and
                      level.segment_id in segment_ids_to_bind):
                  LOG.debug("segment %(segment)s is already bound "
                            "by driver %(driver)s",
                            {"segment": level.segment_id,
                             "driver": level.driver})
                  return False
          return True
  
      def get_workers(self):
          workers = []
          for driver in self.ordered_mech_drivers:
              workers += driver.obj.get_workers()
          return workers
  
  
  class ExtensionManager(stevedore.named.NamedExtensionManager):
      """Manage extension drivers using drivers."""
  
      def __init__(self):
          # Ordered list of extension drivers, defining
          # the order in which the drivers are called.
          self.ordered_ext_drivers = []
  
          LOG.info("Configured extension driver names: %s",
                   cfg.CONF.ml2.extension_drivers)
          super(ExtensionManager, self).__init__('neutron.ml2.extension_drivers',
                                                 cfg.CONF.ml2.extension_drivers,
                                                 invoke_on_load=True,
                                                 name_order=True)
          LOG.info("Loaded extension driver names: %s", self.names())
          self._register_drivers()
  
      def _register_drivers(self):
          """Register all extension drivers.
  
          This method should only be called once in the ExtensionManager
          constructor.
          """
          for ext in self:
              self.ordered_ext_drivers.append(ext)
          LOG.info("Registered extension drivers: %s",
                   [driver.name for driver in self.ordered_ext_drivers])
  
      def initialize(self):
          # Initialize each driver in the list.
          for driver in self.ordered_ext_drivers:
              LOG.info("Initializing extension driver '%s'", driver.name)
              driver.obj.initialize()
  
      def extension_aliases(self):
          exts = []
          for driver in self.ordered_ext_drivers:
              aliases = driver.obj.extension_aliases
              for alias in aliases:
                  if not alias:
                      continue
                  exts.append(alias)
                  LOG.info("Got %(alias)s extension from driver '%(drv)s'",
                           {'alias': alias, 'drv': driver.name})
          return exts
  
      def _call_on_ext_drivers(self, method_name, plugin_context, data, result):
          """Helper method for calling a method across all extension drivers."""
          for driver in self.ordered_ext_drivers:
              try:
                  getattr(driver.obj, method_name)(plugin_context, data, result)
              except Exception:
                  with excutils.save_and_reraise_exception():
                      LOG.info("Extension driver '%(name)s' failed in "
                               "%(method)s",
                               {'name': driver.name, 'method': method_name})
  
      def process_create_network(self, plugin_context, data, result):
          """Notify all extension drivers during network creation."""
          self._call_on_ext_drivers("process_create_network", plugin_context,
                                    data, result)
  
      def process_update_network(self, plugin_context, data, result):
          """Notify all extension drivers during network update."""
          self._call_on_ext_drivers("process_update_network", plugin_context,
                                    data, result)
  
      def process_create_subnet(self, plugin_context, data, result):
          """Notify all extension drivers during subnet creation."""
          self._call_on_ext_drivers("process_create_subnet", plugin_context,
                                    data, result)
  
      def process_update_subnet(self, plugin_context, data, result):
          """Notify all extension drivers during subnet update."""
          self._call_on_ext_drivers("process_update_subnet", plugin_context,
                                    data, result)
  
      def process_create_port(self, plugin_context, data, result):
          """Notify all extension drivers during port creation."""
          self._call_on_ext_drivers("process_create_port", plugin_context,
                                    data, result)
  
      def process_update_port(self, plugin_context, data, result):
          """Notify all extension drivers during port update."""
          self._call_on_ext_drivers("process_update_port", plugin_context,
                                    data, result)
  
      def _call_on_dict_driver(self, method_name, session, base_model, result):
          for driver in self.ordered_ext_drivers:
              try:
                  getattr(driver.obj, method_name)(session, base_model, result)
              except Exception:
                  LOG.exception("Extension driver '%(name)s' failed in "
                                "%(method)s",
                                {'name': driver.name, 'method': method_name})
                  raise ml2_exc.ExtensionDriverError(driver=driver.name)
  
      def extend_network_dict(self, session, base_model, result):
          """Notify all extension drivers to extend network dictionary."""
          self._call_on_dict_driver("extend_network_dict", session, base_model,
                                    result)
  
      def extend_subnet_dict(self, session, base_model, result):
          """Notify all extension drivers to extend subnet dictionary."""
          self._call_on_dict_driver("extend_subnet_dict", session, base_model,
                                    result)
  
      def extend_port_dict(self, session, base_model, result):
          """Notify all extension drivers to extend port dictionary."""
          self._call_on_dict_driver("extend_port_dict", session, base_model,
                                    result)
  