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.
  
  import copy
  
  from eventlet import greenthread
  from neutron_lib.api.definitions import portbindings
  from neutron_lib.api.definitions import provider_net
  from neutron_lib.api import validators
  from neutron_lib.callbacks import events
  from neutron_lib.callbacks import exceptions
  from neutron_lib.callbacks import registry
  from neutron_lib.callbacks import resources
  from neutron_lib import constants as const
  from neutron_lib import exceptions as exc
  from neutron_lib.plugins import directory
  from oslo_config import cfg
  from oslo_db import exception as os_db_exception
  from oslo_log import helpers as log_helpers
  from oslo_log import log
  from oslo_serialization import jsonutils
  from oslo_utils import excutils
  from oslo_utils import importutils
  from oslo_utils import uuidutils
  import sqlalchemy
  from sqlalchemy.orm import exc as sa_exc
  
  from neutron._i18n import _, _LE, _LI, _LW
  from neutron.agent import securitygroups_rpc as sg_rpc
  from neutron.api.rpc.agentnotifiers import dhcp_rpc_agent_api
  from neutron.api.rpc.handlers import dhcp_rpc
  from neutron.api.rpc.handlers import dvr_rpc
  from neutron.api.rpc.handlers import metadata_rpc
  from neutron.api.rpc.handlers import resources_rpc
  from neutron.api.rpc.handlers import securitygroups_rpc
  from neutron.api.v2 import attributes
  from neutron.common import constants as n_const
  from neutron.common import rpc as n_rpc
  from neutron.common import topics
  from neutron.common import utils
  from neutron.db import _model_query as model_query
  from neutron.db import _resource_extend as resource_extend
  from neutron.db import _utils as db_utils
  from neutron.db import address_scope_db
  from neutron.db import agents_db
  from neutron.db import agentschedulers_db
  from neutron.db import allowedaddresspairs_db as addr_pair_db
  from neutron.db import api as db_api
  from neutron.db import db_base_plugin_v2
  from neutron.db import dvr_mac_db
  from neutron.db import external_net_db
  from neutron.db import extradhcpopt_db
  from neutron.db.models import securitygroup as sg_models
  from neutron.db import models_v2
  from neutron.db import provisioning_blocks
  from neutron.db.quota import driver  # noqa
  from neutron.db import securitygroups_rpc_base as sg_db_rpc
  from neutron.db import segments_db
  from neutron.db import subnet_service_type_db_models as service_type_db
  from neutron.db import vlantransparent_db
  from neutron.extensions import allowedaddresspairs as addr_pair
  from neutron.extensions import availability_zone as az_ext
  from neutron.extensions import extra_dhcp_opt as edo_ext
  from neutron.extensions import multiprovidernet as mpnet
  from neutron.extensions import portsecurity as psec
  from neutron.extensions import providernet as provider
  from neutron.extensions import vlantransparent
  from neutron.plugins.ml2.common import exceptions as ml2_exc
  from neutron.plugins.ml2 import config  # noqa
  from neutron.plugins.ml2 import db
  from neutron.plugins.ml2 import driver_api as api
  from neutron.plugins.ml2 import driver_context
  from neutron.plugins.ml2.extensions import qos as qos_ext
  from neutron.plugins.ml2 import managers
  from neutron.plugins.ml2 import models
  from neutron.plugins.ml2 import ovo_rpc
  from neutron.plugins.ml2 import rpc
  from neutron.quota import resource_registry
  from neutron.services.qos import qos_consts
  from neutron.services.segments import plugin as segments_plugin
  
  LOG = log.getLogger(__name__)
  
  MAX_BIND_TRIES = 10
  
  
  SERVICE_PLUGINS_REQUIRED_DRIVERS = {
      'qos': [qos_ext.QOS_EXT_DRIVER_ALIAS]
  }
  
  
  def _ml2_port_result_filter_hook(query, filters):
      values = filters and filters.get(portbindings.HOST_ID, [])
      if not values:
          return query
      bind_criteria = models.PortBinding.host.in_(values)
      return query.filter(models_v2.Port.port_binding.has(bind_criteria))
  
  
  @resource_extend.has_resource_extenders
  @registry.has_registry_receivers
  class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
                  dvr_mac_db.DVRDbMixin,
                  external_net_db.External_net_db_mixin,
                  sg_db_rpc.SecurityGroupServerRpcMixin,
                  agentschedulers_db.AZDhcpAgentSchedulerDbMixin,
                  addr_pair_db.AllowedAddressPairsMixin,
                  vlantransparent_db.Vlantransparent_db_mixin,
                  extradhcpopt_db.ExtraDhcpOptMixin,
                  address_scope_db.AddressScopeDbMixin,
                  service_type_db.SubnetServiceTypeMixin):
  
      """Implement the Neutron L2 abstractions using modules.
  
      Ml2Plugin is a Neutron plugin based on separately extensible sets
      of network types and mechanisms for connecting to networks of
      those types. The network types and mechanisms are implemented as
      drivers loaded via Python entry points. Networks can be made up of
      multiple segments (not yet fully implemented).
      """
  
      # This attribute specifies whether the plugin supports or not
      # bulk/pagination/sorting operations. Name mangling is used in
      # order to ensure it is qualified by class
      __native_bulk_support = True
      __native_pagination_support = True
      __native_sorting_support = True
  
      # List of supported extensions
      _supported_extension_aliases = ["provider", "external-net", "binding",
                                      "quotas", "security-group", "agent",
                                      "dhcp_agent_scheduler",
                                      "multi-provider", "allowed-address-pairs",
                                      "extra_dhcp_opt", "subnet_allocation",
                                      "net-mtu", "vlan-transparent",
                                      "address-scope",
                                      "availability_zone",
                                      "network_availability_zone",
                                      "default-subnetpools",
                                      "subnet-service-types"]
  
      @property
      def supported_extension_aliases(self):
          if not hasattr(self, '_aliases'):
              aliases = self._supported_extension_aliases[:]
              aliases += self.extension_manager.extension_aliases()
              sg_rpc.disable_security_group_extension_by_config(aliases)
              vlantransparent.disable_extension_by_config(aliases)
              self._aliases = aliases
          return self._aliases
  
      def __new__(cls, *args, **kwargs):
          model_query.register_hook(
              models_v2.Port,
              "ml2_port_bindings",
              query_hook=None,
              filter_hook=None,
              result_filters=_ml2_port_result_filter_hook)
          return super(Ml2Plugin, cls).__new__(cls, *args, **kwargs)
  
      @resource_registry.tracked_resources(
          network=models_v2.Network,
          port=models_v2.Port,
          subnet=models_v2.Subnet,
          subnetpool=models_v2.SubnetPool,
          security_group=sg_models.SecurityGroup,
          security_group_rule=sg_models.SecurityGroupRule)
      def __init__(self):
          # First load drivers, then initialize DB, then initialize drivers
          self.type_manager = managers.TypeManager()
          self.extension_manager = managers.ExtensionManager()
          self.mechanism_manager = managers.MechanismManager()
          super(Ml2Plugin, self).__init__()
          self.type_manager.initialize()
          self.extension_manager.initialize()
          self.mechanism_manager.initialize()
          self._setup_dhcp()
          self._start_rpc_notifiers()
          self.add_agent_status_check_worker(self.agent_health_check)
          self.add_workers(self.mechanism_manager.get_workers())
          self._verify_service_plugins_requirements()
          LOG.info(_LI("Modular L2 Plugin initialization complete"))
  
      def _setup_rpc(self):
          """Initialize components to support agent communication."""
          self.endpoints = [
              rpc.RpcCallbacks(self.notifier, self.type_manager),
              securitygroups_rpc.SecurityGroupServerRpcCallback(),
              dvr_rpc.DVRServerRpcCallback(),
              dhcp_rpc.DhcpRpcCallback(),
              agents_db.AgentExtRpcCallback(),
              metadata_rpc.MetadataRpcCallback(),
              resources_rpc.ResourcesPullRpcCallback()
          ]
  
      def _setup_dhcp(self):
          """Initialize components to support DHCP."""
          self.network_scheduler = importutils.import_object(
              cfg.CONF.network_scheduler_driver
          )
          self.add_periodic_dhcp_agent_status_check()
  
      def _verify_service_plugins_requirements(self):
          for service_plugin in cfg.CONF.service_plugins:
              extension_drivers = SERVICE_PLUGINS_REQUIRED_DRIVERS.get(
                  service_plugin, []
              )
              for extension_driver in extension_drivers:
                  if extension_driver not in self.extension_manager.names():
                      raise ml2_exc.ExtensionDriverNotFound(
                          driver=extension_driver, service_plugin=service_plugin
                      )
  
      @registry.receives(resources.PORT,
                         [provisioning_blocks.PROVISIONING_COMPLETE])
      def _port_provisioned(self, rtype, event, trigger, context, object_id,
                            **kwargs):
          port_id = object_id
          port = db.get_port(context, port_id)
          if not port or not port.port_binding:
              LOG.debug("Port %s was deleted so its status cannot be updated.",
                        port_id)
              return
          if port.port_binding.vif_type in (portbindings.VIF_TYPE_BINDING_FAILED,
                                            portbindings.VIF_TYPE_UNBOUND):
              # NOTE(kevinbenton): we hit here when a port is created without
              # a host ID and the dhcp agent notifies that its wiring is done
              LOG.debug("Port %s cannot update to ACTIVE because it "
                        "is not bound.", port_id)
              return
          else:
              # port is bound, but we have to check for new provisioning blocks
              # one last time to detect the case where we were triggered by an
              # unbound port and the port became bound with new provisioning
              # blocks before 'get_port' was called above
              if provisioning_blocks.is_object_blocked(context, port_id,
                                                       resources.PORT):
                  LOG.debug("Port %s had new provisioning blocks added so it "
                            "will not transition to active.", port_id)
                  return
          self.update_port_status(context, port_id, const.PORT_STATUS_ACTIVE)
  
      @log_helpers.log_method_call
      def _start_rpc_notifiers(self):
          """Initialize RPC notifiers for agents."""
          self.ovo_notifier = ovo_rpc.OVOServerRpcInterface()
          self.notifier = rpc.AgentNotifierApi(topics.AGENT)
          self.agent_notifiers[const.AGENT_TYPE_DHCP] = (
              dhcp_rpc_agent_api.DhcpAgentNotifyAPI()
          )
  
      @log_helpers.log_method_call
      def start_rpc_listeners(self):
          """Start the RPC loop to let the plugin communicate with agents."""
          self._setup_rpc()
          self.topic = topics.PLUGIN
          self.conn = n_rpc.create_connection()
          self.conn.create_consumer(self.topic, self.endpoints, fanout=False)
          self.conn.create_consumer(
              topics.SERVER_RESOURCE_VERSIONS,
              [resources_rpc.ResourcesPushToServerRpcCallback()],
              fanout=True)
          # process state reports despite dedicated rpc workers
          self.conn.create_consumer(topics.REPORTS,
                                    [agents_db.AgentExtRpcCallback()],
                                    fanout=False)
          return self.conn.consume_in_threads()
  
      def start_rpc_state_reports_listener(self):
          self.conn_reports = n_rpc.create_connection()
          self.conn_reports.create_consumer(topics.REPORTS,
                                            [agents_db.AgentExtRpcCallback()],
                                            fanout=False)
          return self.conn_reports.consume_in_threads()
  
      def _filter_nets_provider(self, context, networks, filters):
          return [network
                  for network in networks
                  if self.type_manager.network_matches_filters(network, filters)
                  ]
  
      def _check_mac_update_allowed(self, orig_port, port, binding):
          unplugged_types = (portbindings.VIF_TYPE_BINDING_FAILED,
                             portbindings.VIF_TYPE_UNBOUND)
          new_mac = port.get('mac_address')
          mac_change = (new_mac is not None and
                        orig_port['mac_address'] != new_mac)
          if (mac_change and binding.vif_type not in unplugged_types):
              raise exc.PortBound(port_id=orig_port['id'],
                                  vif_type=binding.vif_type,
                                  old_mac=orig_port['mac_address'],
                                  new_mac=port['mac_address'])
          return mac_change
  
      def _process_port_binding(self, mech_context, attrs):
          plugin_context = mech_context._plugin_context
          binding = mech_context._binding
          port = mech_context.current
          port_id = port['id']
          changes = False
  
          host = const.ATTR_NOT_SPECIFIED
          if attrs and portbindings.HOST_ID in attrs:
              host = attrs.get(portbindings.HOST_ID) or ''
  
          original_host = binding.host
          if (validators.is_attr_set(host) and
              original_host != host):
              binding.host = host
              changes = True
  
          vnic_type = attrs and attrs.get(portbindings.VNIC_TYPE)
          if (validators.is_attr_set(vnic_type) and
              binding.vnic_type != vnic_type):
              binding.vnic_type = vnic_type
              changes = True
  
          # treat None as clear of profile.
          profile = None
          if attrs and portbindings.PROFILE in attrs:
              profile = attrs.get(portbindings.PROFILE) or {}
  
          if profile not in (None, const.ATTR_NOT_SPECIFIED,
                             self._get_profile(binding)):
              binding.profile = jsonutils.dumps(profile)
              if len(binding.profile) > models.BINDING_PROFILE_LEN:
                  msg = _("binding:profile value too large")
                  raise exc.InvalidInput(error_message=msg)
              changes = True
  
          # Unbind the port if needed.
          if changes:
              binding.vif_type = portbindings.VIF_TYPE_UNBOUND
              binding.vif_details = ''
              db.clear_binding_levels(plugin_context, port_id, original_host)
              mech_context._clear_binding_levels()
              port['status'] = const.PORT_STATUS_DOWN
              super(Ml2Plugin, self).update_port(
                  mech_context._plugin_context, port_id,
                  {attributes.PORT: {'status': const.PORT_STATUS_DOWN}})
  
          if port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
              binding.vif_type = portbindings.VIF_TYPE_UNBOUND
              binding.vif_details = ''
              db.clear_binding_levels(plugin_context, port_id, original_host)
              mech_context._clear_binding_levels()
              binding.host = ''
  
          self._update_port_dict_binding(port, binding)
          # merging here brings binding changes into the session so they can be
          # committed since the binding attached to the context is detached from
          # the session
          plugin_context.session.merge(binding)
          return changes
  
      @db_api.retry_db_errors
      def _bind_port_if_needed(self, context, allow_notify=False,
                               need_notify=False):
          for count in range(1, MAX_BIND_TRIES + 1):
              if count > 1:
                  # yield for binding retries so that we give other threads a
                  # chance to do their work
                  greenthread.sleep(0)
  
                  # multiple attempts shouldn't happen very often so we log each
                  # attempt after the 1st.
                  LOG.info(_LI("Attempt %(count)s to bind port %(port)s"),
                           {'count': count, 'port': context.current['id']})
  
              bind_context, need_notify, try_again = self._attempt_binding(
                  context, need_notify)
  
              if count == MAX_BIND_TRIES or not try_again:
                  if self._should_bind_port(context):
                      # At this point, we attempted to bind a port and reached
                      # its final binding state. Binding either succeeded or
                      # exhausted all attempts, thus no need to try again.
                      # Now, the port and its binding state should be committed.
                      context, need_notify, try_again = (
                          self._commit_port_binding(context, bind_context,
                                                    need_notify, try_again))
                  else:
                      context = bind_context
  
              if not try_again:
                  if allow_notify and need_notify:
                      self._notify_port_updated(context)
                  return context
  
          LOG.error(_LE("Failed to commit binding results for %(port)s "
                        "after %(max)s tries"),
                    {'port': context.current['id'], 'max': MAX_BIND_TRIES})
          return context
  
      def _should_bind_port(self, context):
          return (context._binding.host and context._binding.vif_type
                  in (portbindings.VIF_TYPE_UNBOUND,
                      portbindings.VIF_TYPE_BINDING_FAILED))
  
      def _attempt_binding(self, context, need_notify):
          try_again = False
  
          if self._should_bind_port(context):
              bind_context = self._bind_port(context)
  
              if bind_context.vif_type != portbindings.VIF_TYPE_BINDING_FAILED:
                  # Binding succeeded. Suggest notifying of successful binding.
                  need_notify = True
              else:
                  # Current attempt binding failed, try to bind again.
                  try_again = True
              context = bind_context
  
          return context, need_notify, try_again
  
      def _bind_port(self, orig_context):
          # Construct a new PortContext from the one from the previous
          # transaction.
          port = orig_context.current
          orig_binding = orig_context._binding
          new_binding = models.PortBinding(
              host=orig_binding.host,
              vnic_type=orig_binding.vnic_type,
              profile=orig_binding.profile,
              vif_type=portbindings.VIF_TYPE_UNBOUND,
              vif_details=''
          )
          self._update_port_dict_binding(port, new_binding)
          new_context = driver_context.PortContext(
              self, orig_context._plugin_context, port,
              orig_context.network.current, new_binding, None,
              original_port=orig_context.original)
  
          # Attempt to bind the port and return the context with the
          # result.
          self.mechanism_manager.bind_port(new_context)
          return new_context
  
      def _commit_port_binding(self, orig_context, bind_context,
                               need_notify, try_again):
          port_id = orig_context.current['id']
          plugin_context = orig_context._plugin_context
          orig_binding = orig_context._binding
          new_binding = bind_context._binding
  
          # After we've attempted to bind the port, we begin a
          # transaction, get the current port state, and decide whether
          # to commit the binding results.
          with db_api.context_manager.writer.using(plugin_context):
              # Get the current port state and build a new PortContext
              # reflecting this state as original state for subsequent
              # mechanism driver update_port_*commit() calls.
              try:
                  port_db = self._get_port(plugin_context, port_id)
                  cur_binding = port_db.port_binding
              except exc.PortNotFound:
                  port_db, cur_binding = None, None
              if not port_db or not cur_binding:
                  # The port has been deleted concurrently, so just
                  # return the unbound result from the initial
                  # transaction that completed before the deletion.
                  LOG.debug("Port %s has been deleted concurrently", port_id)
                  return orig_context, False, False
              # Since the mechanism driver bind_port() calls must be made
              # outside a DB transaction locking the port state, it is
              # possible (but unlikely) that the port's state could change
              # concurrently while these calls are being made. If another
              # thread or process succeeds in binding the port before this
              # thread commits its results, the already committed results are
              # used. If attributes such as binding:host_id, binding:profile,
              # or binding:vnic_type are updated concurrently, the try_again
              # flag is returned to indicate that the commit was unsuccessful.
              oport = self._make_port_dict(port_db)
              port = self._make_port_dict(port_db)
              network = bind_context.network.current
              if port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
                  # REVISIT(rkukura): The PortBinding instance from the
                  # ml2_port_bindings table, returned as cur_binding
                  # from port_db.port_binding above, is
                  # currently not used for DVR distributed ports, and is
                  # replaced here with the DistributedPortBinding instance from
                  # the ml2_distributed_port_bindings table specific to the host
                  # on which the distributed port is being bound. It
                  # would be possible to optimize this code to avoid
                  # fetching the PortBinding instance in the DVR case,
                  # and even to avoid creating the unused entry in the
                  # ml2_port_bindings table. But the upcoming resolution
                  # for bug 1367391 will eliminate the
                  # ml2_distributed_port_bindings table, use the
                  # ml2_port_bindings table to store non-host-specific
                  # fields for both distributed and non-distributed
                  # ports, and introduce a new ml2_port_binding_hosts
                  # table for the fields that need to be host-specific
                  # in the distributed case. Since the PortBinding
                  # instance will then be needed, it does not make sense
                  # to optimize this code to avoid fetching it.
                  cur_binding = db.get_distributed_port_binding_by_host(
                      plugin_context, port_id, orig_binding.host)
              cur_context = driver_context.PortContext(
                  self, plugin_context, port, network, cur_binding, None,
                  original_port=oport)
  
              # Commit our binding results only if port has not been
              # successfully bound concurrently by another thread or
              # process and no binding inputs have been changed.
              commit = ((cur_binding.vif_type in
                         [portbindings.VIF_TYPE_UNBOUND,
                          portbindings.VIF_TYPE_BINDING_FAILED]) and
                        orig_binding.host == cur_binding.host and
                        orig_binding.vnic_type == cur_binding.vnic_type and
                        orig_binding.profile == cur_binding.profile)
  
              if commit:
                  # Update the port's binding state with our binding
                  # results.
                  cur_binding.vif_type = new_binding.vif_type
                  cur_binding.vif_details = new_binding.vif_details
                  db.clear_binding_levels(plugin_context, port_id,
                                          cur_binding.host)
                  db.set_binding_levels(plugin_context,
                                        bind_context._binding_levels)
                  # refresh context with a snapshot of updated state
                  cur_context._binding = copy.deepcopy(cur_binding)
                  cur_context._binding_levels = bind_context._binding_levels
  
                  # Update PortContext's port dictionary to reflect the
                  # updated binding state.
                  self._update_port_dict_binding(port, cur_binding)
  
                  # Update the port status if requested by the bound driver.
                  if (bind_context._binding_levels and
                      bind_context._new_port_status):
                      port_db.status = bind_context._new_port_status
                      port['status'] = bind_context._new_port_status
  
                  # Call the mechanism driver precommit methods, commit
                  # the results, and call the postcommit methods.
                  self.mechanism_manager.update_port_precommit(cur_context)
          if commit:
              # Continue, using the port state as of the transaction that
              # just finished, whether that transaction committed new
              # results or discovered concurrent port state changes.
              # Also, Trigger notification for successful binding commit.
              kwargs = {
                  'context': plugin_context,
                  'port': port,
                  'mac_address_updated': False,
                  'original_port': oport,
              }
              registry.notify(resources.PORT, events.AFTER_UPDATE,
                              self, **kwargs)
              self.mechanism_manager.update_port_postcommit(cur_context)
              need_notify = True
              try_again = False
          else:
              try_again = True
  
          return cur_context, need_notify, try_again
  
      def _update_port_dict_binding(self, port, binding):
          port[portbindings.VNIC_TYPE] = binding.vnic_type
          port[portbindings.PROFILE] = self._get_profile(binding)
          if port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
              port[portbindings.HOST_ID] = ''
              port[portbindings.VIF_TYPE] = portbindings.VIF_TYPE_DISTRIBUTED
              port[portbindings.VIF_DETAILS] = {}
          else:
              port[portbindings.HOST_ID] = binding.host
              port[portbindings.VIF_TYPE] = binding.vif_type
              port[portbindings.VIF_DETAILS] = self._get_vif_details(binding)
  
      def _get_vif_details(self, binding):
          if binding.vif_details:
              try:
                  return jsonutils.loads(binding.vif_details)
              except Exception:
                  LOG.error(_LE("Serialized vif_details DB value '%(value)s' "
                                "for port %(port)s is invalid"),
                            {'value': binding.vif_details,
                             'port': binding.port_id})
          return {}
  
      def _get_profile(self, binding):
          if binding.profile:
              try:
                  return jsonutils.loads(binding.profile)
              except Exception:
                  LOG.error(_LE("Serialized profile DB value '%(value)s' for "
                                "port %(port)s is invalid"),
                            {'value': binding.profile,
                             'port': binding.port_id})
          return {}
  
      @staticmethod
      @resource_extend.extends([attributes.PORTS])
      def _ml2_extend_port_dict_binding(port_res, port_db):
          plugin = directory.get_plugin()
          # None when called during unit tests for other plugins.
          if port_db.port_binding:
              plugin._update_port_dict_binding(port_res, port_db.port_binding)
  
      # ML2's resource extend functions allow extension drivers that extend
      # attributes for the resources to add those attributes to the result.
  
      @staticmethod
      @resource_extend.extends([attributes.NETWORKS])
      def _ml2_md_extend_network_dict(result, netdb):
          plugin = directory.get_plugin()
          session = plugin._object_session_or_new_session(netdb)
          plugin.extension_manager.extend_network_dict(session, netdb, result)
  
      @staticmethod
      @resource_extend.extends([attributes.PORTS])
      def _ml2_md_extend_port_dict(result, portdb):
          plugin = directory.get_plugin()
          session = plugin._object_session_or_new_session(portdb)
          plugin.extension_manager.extend_port_dict(session, portdb, result)
  
      @staticmethod
      @resource_extend.extends([attributes.SUBNETS])
      def _ml2_md_extend_subnet_dict(result, subnetdb):
          plugin = directory.get_plugin()
          session = plugin._object_session_or_new_session(subnetdb)
          plugin.extension_manager.extend_subnet_dict(session, subnetdb, result)
  
      @staticmethod
      def _object_session_or_new_session(sql_obj):
          session = sqlalchemy.inspect(sql_obj).session
          if not session:
              session = db_api.get_reader_session()
          return session
  
      def _notify_port_updated(self, mech_context):
          port = mech_context.current
          segment = mech_context.bottom_bound_segment
          if not segment:
              # REVISIT(rkukura): This should notify agent to unplug port
              network = mech_context.network.current
              LOG.debug("In _notify_port_updated(), no bound segment for "
                        "port %(port_id)s on network %(network_id)s",
                        {'port_id': port['id'], 'network_id': network['id']})
              return
          self.notifier.port_update(mech_context._plugin_context, port,
                                    segment[api.NETWORK_TYPE],
                                    segment[api.SEGMENTATION_ID],
                                    segment[api.PHYSICAL_NETWORK])
  
      def _delete_objects(self, context, resource, objects):
          delete_op = getattr(self, 'delete_%s' % resource)
          for obj in objects:
              try:
                  delete_op(context, obj['result']['id'])
              except KeyError:
                  LOG.exception(_LE("Could not find %s to delete."),
                                resource)
              except Exception:
                  LOG.exception(_LE("Could not delete %(res)s %(id)s."),
                                {'res': resource,
                                 'id': obj['result']['id']})
  
      def _create_bulk_ml2(self, resource, context, request_items):
          objects = []
          collection = "%ss" % resource
          items = request_items[collection]
          obj_before_create = getattr(self, '_before_create_%s' % resource)
          for item in items:
              obj_before_create(context, item)
          with db_api.context_manager.writer.using(context):
              obj_creator = getattr(self, '_create_%s_db' % resource)
              for item in items:
                  try:
                      attrs = item[resource]
                      result, mech_context = obj_creator(context, item)
                      objects.append({'mech_context': mech_context,
                                      'result': result,
                                      'attributes': attrs})
  
                  except Exception as e:
                      with excutils.save_and_reraise_exception():
                          utils.attach_exc_details(
                              e, _LE("An exception occurred while creating "
                                     "the %(resource)s:%(item)s"),
                              {'resource': resource, 'item': item})
  
          postcommit_op = getattr(self, '_after_create_%s' % resource)
          for obj in objects:
              try:
                  postcommit_op(context, obj['result'], obj['mech_context'])
              except Exception:
                  with excutils.save_and_reraise_exception():
                      resource_ids = [res['result']['id'] for res in objects]
                      LOG.exception(_LE("ML2 _after_create_%(res)s "
                                        "failed for %(res)s: "
                                        "'%(failed_id)s'. Deleting "
                                        "%(res)ss %(resource_ids)s"),
                                    {'res': resource,
                                     'failed_id': obj['result']['id'],
                                     'resource_ids': ', '.join(resource_ids)})
                      # _after_handler will have deleted the object that threw
                      to_delete = [o for o in objects if o != obj]
                      self._delete_objects(context, resource, to_delete)
          return objects
  
      def _get_network_mtu(self, network):
          mtus = []
          try:
              segments = network[mpnet.SEGMENTS]
          except KeyError:
              segments = [network]
          for s in segments:
              segment_type = s[provider_net.NETWORK_TYPE]
              try:
                  type_driver = self.type_manager.drivers[segment_type].obj
              except KeyError:
                  # NOTE(ihrachys) This can happen when type driver is not loaded
                  # for an existing segment, or simply when the network has no
                  # segments at the specific time this is computed.
                  # In the former case, while it's probably an indication of
                  # a bad setup, it's better to be safe than sorry here. Also,
                  # several unit tests use non-existent driver types that may
                  # trigger the exception here.
                  if segment_type and s[provider_net.SEGMENTATION_ID]:
                      LOG.warning(
                          _LW("Failed to determine MTU for segment "
                              "%(segment_type)s:%(segment_id)s; network "
                              "%(network_id)s MTU calculation may be not "
                              "accurate"),
                          {
                              'segment_type': segment_type,
                              'segment_id': s[provider_net.SEGMENTATION_ID],
                              'network_id': network['id'],
                          }
                      )
              else:
                  mtu = type_driver.get_mtu(s[provider_net.PHYSICAL_NETWORK])
                  # Some drivers, like 'local', may return None; the assumption
                  # then is that for the segment type, MTU has no meaning or
                  # unlimited, and so we should then ignore those values.
                  if mtu:
                      mtus.append(mtu)
          return min(mtus) if mtus else 0
  
      def _before_create_network(self, context, network):
          net_data = network[attributes.NETWORK]
          registry.notify(resources.NETWORK, events.BEFORE_CREATE, self,
                          context=context, network=net_data)
  
      def _create_network_db(self, context, network):
          net_data = network[attributes.NETWORK]
          tenant_id = net_data['tenant_id']
          with db_api.context_manager.writer.using(context):
              net_db = self.create_network_db(context, network)
              result = self._make_network_dict(net_db, process_extensions=False,
                                               context=context)
              self.extension_manager.process_create_network(context, net_data,
                                                            result)
              self._process_l3_create(context, result, net_data)
              net_data['id'] = result['id']
              self.type_manager.create_network_segments(context, net_data,
                                                        tenant_id)
              self.type_manager.extend_network_dict_provider(context, result)
              # Update the transparent vlan if configured
              if utils.is_extension_supported(self, 'vlan-transparent'):
                  vlt = vlantransparent.get_vlan_transparent(net_data)
                  net_db['vlan_transparent'] = vlt
                  result['vlan_transparent'] = vlt
  
              result[api.MTU] = self._get_network_mtu(result)
  
              if az_ext.AZ_HINTS in net_data:
                  self.validate_availability_zones(context, 'network',
                                                   net_data[az_ext.AZ_HINTS])
                  az_hints = az_ext.convert_az_list_to_string(
                                                  net_data[az_ext.AZ_HINTS])
                  net_db[az_ext.AZ_HINTS] = az_hints
                  result[az_ext.AZ_HINTS] = az_hints
              registry.notify(resources.NETWORK, events.PRECOMMIT_CREATE, self,
                              context=context, request=net_data, network=result)
  
              resource_extend.apply_funcs('networks', result, net_db)
              mech_context = driver_context.NetworkContext(self, context,
                                                           result)
              self.mechanism_manager.create_network_precommit(mech_context)
          return result, mech_context
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def create_network(self, context, network):
          self._before_create_network(context, network)
          result, mech_context = self._create_network_db(context, network)
          return self._after_create_network(context, result, mech_context)
  
      def _after_create_network(self, context, result, mech_context):
          kwargs = {'context': context, 'network': result}
          registry.notify(resources.NETWORK, events.AFTER_CREATE, self, **kwargs)
          try:
              self.mechanism_manager.create_network_postcommit(mech_context)
          except ml2_exc.MechanismDriverError:
              with excutils.save_and_reraise_exception():
                  LOG.error(_LE("mechanism_manager.create_network_postcommit "
                                "failed, deleting network '%s'"), result['id'])
                  self.delete_network(context, result['id'])
  
          return result
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def create_network_bulk(self, context, networks):
          objects = self._create_bulk_ml2(attributes.NETWORK, context, networks)
          return [obj['result'] for obj in objects]
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def update_network(self, context, id, network):
          net_data = network[attributes.NETWORK]
          provider._raise_if_updates_provider_attributes(net_data)
  
          with db_api.context_manager.writer.using(context):
              original_network = super(Ml2Plugin, self).get_network(context, id)
              updated_network = super(Ml2Plugin, self).update_network(context,
                                                                      id,
                                                                      network)
              self.extension_manager.process_update_network(context, net_data,
                                                            updated_network)
              self._process_l3_update(context, updated_network, net_data)
              self.type_manager.extend_network_dict_provider(context,
                                                             updated_network)
  
              # ToDO(QoS): This would change once EngineFacade moves out
              db_network = self._get_network(context, id)
              # Expire the db_network in current transaction, so that the join
              # relationship can be updated.
              context.session.expire(db_network)
              updated_network = self._make_network_dict(
                  db_network, context=context)
  
              kwargs = {'context': context, 'network': updated_network,
                        'original_network': original_network,
                        'request': net_data}
              registry.notify(
                  resources.NETWORK, events.PRECOMMIT_UPDATE, self, **kwargs)
  
              # TODO(QoS): Move out to the extension framework somehow.
              need_network_update_notify = (
                  qos_consts.QOS_POLICY_ID in net_data and
                  original_network[qos_consts.QOS_POLICY_ID] !=
                  updated_network[qos_consts.QOS_POLICY_ID])
  
              mech_context = driver_context.NetworkContext(
                  self, context, updated_network,
                  original_network=original_network)
              self.mechanism_manager.update_network_precommit(mech_context)
  
          # TODO(apech) - handle errors raised by update_network, potentially
          # by re-calling update_network with the previous attributes. For
          # now the error is propagated to the caller, which is expected to
          # either undo/retry the operation or delete the resource.
          kwargs = {'context': context, 'network': updated_network,
                    'original_network': original_network}
          registry.notify(resources.NETWORK, events.AFTER_UPDATE, self, **kwargs)
          self.mechanism_manager.update_network_postcommit(mech_context)
          if need_network_update_notify:
              self.notifier.network_update(context, updated_network)
          return updated_network
  
      @db_api.retry_if_session_inactive()
      def get_network(self, context, id, fields=None):
          with db_api.context_manager.reader.using(context):
              result = super(Ml2Plugin, self).get_network(context, id, None)
              self.type_manager.extend_network_dict_provider(context, result)
              result[api.MTU] = self._get_network_mtu(result)
  
          return db_utils.resource_fields(result, fields)
  
      @db_api.retry_if_session_inactive()
      def get_networks(self, context, filters=None, fields=None,
                       sorts=None, limit=None, marker=None, page_reverse=False):
          with db_api.context_manager.reader.using(context):
              nets = super(Ml2Plugin,
                           self).get_networks(context, filters, None, sorts,
                                              limit, marker, page_reverse)
              self.type_manager.extend_networks_dict_provider(context, nets)
  
              nets = self._filter_nets_provider(context, nets, filters)
  
              for net in nets:
                  net[api.MTU] = self._get_network_mtu(net)
  
          return [db_utils.resource_fields(net, fields) for net in nets]
  
      def get_network_contexts(self, context, network_ids):
          """Return a map of network_id to NetworkContext for network_ids."""
          net_filters = {'id': list(set(network_ids))}
          nets_by_netid = {
              n['id']: n for n in self.get_networks(context,
                                                    filters=net_filters)
          }
          segments_by_netid = segments_db.get_networks_segments(
              context, list(nets_by_netid.keys()))
          netctxs_by_netid = {
              net_id: driver_context.NetworkContext(
                  self, context, nets_by_netid[net_id],
                  segments=segments_by_netid[net_id])
              for net_id in nets_by_netid.keys()
          }
          return netctxs_by_netid
  
      @utils.transaction_guard
      def delete_network(self, context, id):
          # the only purpose of this override is to protect this from being
          # called inside of a transaction.
          return super(Ml2Plugin, self).delete_network(context, id)
  
      @registry.receives(resources.NETWORK, [events.PRECOMMIT_DELETE])
      def _network_delete_precommit_handler(self, rtype, event, trigger,
                                            context, network_id, **kwargs):
          network = self.get_network(context, network_id)
          mech_context = driver_context.NetworkContext(self,
                                                       context,
                                                       network)
          # TODO(kevinbenton): move this mech context into something like
          # a 'delete context' so it's not polluting the real context object
          setattr(context, '_mech_context', mech_context)
          self.mechanism_manager.delete_network_precommit(
              mech_context)
  
      @registry.receives(resources.NETWORK, [events.AFTER_DELETE])
      def _network_delete_after_delete_handler(self, rtype, event, trigger,
                                               context, network, **kwargs):
          try:
              self.mechanism_manager.delete_network_postcommit(
                  context._mech_context)
          except ml2_exc.MechanismDriverError:
              # TODO(apech) - One or more mechanism driver failed to
              # delete the network.  Ideally we'd notify the caller of
              # the fact that an error occurred.
              LOG.error(_LE("mechanism_manager.delete_network_postcommit"
                            " failed"))
          self.notifier.network_delete(context, network['id'])
  
      def _before_create_subnet(self, context, subnet):
          # TODO(kevinbenton): BEFORE notification should be added here
          pass
  
      def _create_subnet_db(self, context, subnet):
          with db_api.context_manager.writer.using(context):
              result, net_db, ipam_sub = self._create_subnet_precommit(
                  context, subnet)
              self.extension_manager.process_create_subnet(
                  context, subnet[attributes.SUBNET], result)
              network = self._make_network_dict(net_db, context=context)
              self.type_manager.extend_network_dict_provider(context, network)
              network[api.MTU] = self._get_network_mtu(network)
              mech_context = driver_context.SubnetContext(self, context,
                                                          result, network)
              self.mechanism_manager.create_subnet_precommit(mech_context)
  
          # TODO(kevinbenton): move this to '_after_subnet_create'
          # db base plugin post commit ops
          self._create_subnet_postcommit(context, result, net_db, ipam_sub)
  
          return result, mech_context
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def create_subnet(self, context, subnet):
          self._before_create_subnet(context, subnet)
          result, mech_context = self._create_subnet_db(context, subnet)
          return self._after_create_subnet(context, result, mech_context)
  
      def _after_create_subnet(self, context, result, mech_context):
          kwargs = {'context': context, 'subnet': result}
          registry.notify(resources.SUBNET, events.AFTER_CREATE, self, **kwargs)
          try:
              self.mechanism_manager.create_subnet_postcommit(mech_context)
          except ml2_exc.MechanismDriverError:
              with excutils.save_and_reraise_exception():
                  LOG.error(_LE("mechanism_manager.create_subnet_postcommit "
                                "failed, deleting subnet '%s'"), result['id'])
                  self.delete_subnet(context, result['id'])
          return result
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def create_subnet_bulk(self, context, subnets):
          objects = self._create_bulk_ml2(attributes.SUBNET, context, subnets)
          return [obj['result'] for obj in objects]
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def update_subnet(self, context, id, subnet):
          with db_api.context_manager.writer.using(context):
              updated_subnet, original_subnet = self._update_subnet_precommit(
                  context, id, subnet)
              self.extension_manager.process_update_subnet(
                  context, subnet[attributes.SUBNET], updated_subnet)
              updated_subnet = self.get_subnet(context, id)
              mech_context = driver_context.SubnetContext(
                  self, context, updated_subnet, network=None,
                  original_subnet=original_subnet)
              self.mechanism_manager.update_subnet_precommit(mech_context)
  
          self._update_subnet_postcommit(context, original_subnet,
                                         updated_subnet)
          # TODO(apech) - handle errors raised by update_subnet, potentially
          # by re-calling update_subnet with the previous attributes. For
          # now the error is propagated to the caller, which is expected to
          # either undo/retry the operation or delete the resource.
          self.mechanism_manager.update_subnet_postcommit(mech_context)
          return updated_subnet
  
      @utils.transaction_guard
      def delete_subnet(self, context, id):
          # the only purpose of this override is to protect this from being
          # called inside of a transaction.
          return super(Ml2Plugin, self).delete_subnet(context, id)
  
      @registry.receives(resources.SUBNET, [events.PRECOMMIT_DELETE])
      def _subnet_delete_precommit_handler(self, rtype, event, trigger,
                                           context, subnet_id, **kwargs):
          record = self._get_subnet(context, subnet_id)
          subnet = self._make_subnet_dict(record, context=context)
          network = self.get_network(context, subnet['network_id'])
          mech_context = driver_context.SubnetContext(self, context,
                                                      subnet, network)
          # TODO(kevinbenton): move this mech context into something like
          # a 'delete context' so it's not polluting the real context object
          setattr(context, '_mech_context', mech_context)
          self.mechanism_manager.delete_subnet_precommit(mech_context)
  
      @registry.receives(resources.SUBNET, [events.AFTER_DELETE])
      def _subnet_delete_after_delete_handler(self, rtype, event, trigger,
                                              context, subnet, **kwargs):
          try:
              self.mechanism_manager.delete_subnet_postcommit(
                  context._mech_context)
          except ml2_exc.MechanismDriverError:
              # TODO(apech) - One or more mechanism driver failed to
              # delete the subnet.  Ideally we'd notify the caller of
              # the fact that an error occurred.
              LOG.error(_LE("mechanism_manager.delete_subnet_postcommit failed"))
  
      # TODO(yalei) - will be simplified after security group and address pair be
      # converted to ext driver too.
      def _portsec_ext_port_create_processing(self, context, port_data, port):
          attrs = port[attributes.PORT]
          port_security = ((port_data.get(psec.PORTSECURITY) is None) or
                           port_data[psec.PORTSECURITY])
  
          # allowed address pair checks
          if self._check_update_has_allowed_address_pairs(port):
              if not port_security:
                  raise addr_pair.AddressPairAndPortSecurityRequired()
          else:
              # remove ATTR_NOT_SPECIFIED
              attrs[addr_pair.ADDRESS_PAIRS] = []
  
          if port_security:
              self._ensure_default_security_group_on_port(context, port)
          elif self._check_update_has_security_groups(port):
              raise psec.PortSecurityAndIPRequiredForSecurityGroups()
  
      def _setup_dhcp_agent_provisioning_component(self, context, port):
          subnet_ids = [f['subnet_id'] for f in port['fixed_ips']]
          if (db.is_dhcp_active_on_any_subnet(context, subnet_ids) and
              any(self.get_configuration_dict(a).get('notifies_port_ready')
                  for a in self.get_dhcp_agents_hosting_networks(
                      context, [port['network_id']]))):
              # at least one of the agents will tell us when the dhcp config
              # is ready so we setup a provisioning component to prevent the
              # port from going ACTIVE until a dhcp_ready_on_port
              # notification is received.
              provisioning_blocks.add_provisioning_component(
                  context, port['id'], resources.PORT,
                  provisioning_blocks.DHCP_ENTITY)
          else:
              provisioning_blocks.remove_provisioning_component(
                  context, port['id'], resources.PORT,
                  provisioning_blocks.DHCP_ENTITY)
  
      def _before_create_port(self, context, port):
          attrs = port[attributes.PORT]
          if not attrs.get('status'):
              attrs['status'] = const.PORT_STATUS_DOWN
  
          registry.notify(resources.PORT, events.BEFORE_CREATE, self,
                          context=context, port=attrs)
          # NOTE(kevinbenton): triggered outside of transaction since it
          # emits 'AFTER' events if it creates.
          self._ensure_default_security_group(context, attrs['tenant_id'])
  
      def _create_port_db(self, context, port):
          attrs = port[attributes.PORT]
          with db_api.context_manager.writer.using(context):
              dhcp_opts = attrs.get(edo_ext.EXTRADHCPOPTS, [])
              port_db = self.create_port_db(context, port)
              result = self._make_port_dict(port_db, process_extensions=False)
              self.extension_manager.process_create_port(context, attrs, result)
              self._portsec_ext_port_create_processing(context, result, port)
  
              # sgids must be got after portsec checked with security group
              sgids = self._get_security_groups_on_port(context, port)
              self._process_port_create_security_group(context, result, sgids)
              network = self.get_network(context, result['network_id'])
              binding = db.add_port_binding(context, result['id'])
              mech_context = driver_context.PortContext(self, context, result,
                                                        network, binding, None)
              self._process_port_binding(mech_context, attrs)
  
              result[addr_pair.ADDRESS_PAIRS] = (
                  self._process_create_allowed_address_pairs(
                      context, result,
                      attrs.get(addr_pair.ADDRESS_PAIRS)))
              self._process_port_create_extra_dhcp_opts(context, result,
                                                        dhcp_opts)
              kwargs = {'context': context, 'port': result}
              registry.notify(
                  resources.PORT, events.PRECOMMIT_CREATE, self, **kwargs)
              self.mechanism_manager.create_port_precommit(mech_context)
              self._setup_dhcp_agent_provisioning_component(context, result)
  
          resource_extend.apply_funcs('ports', result, port_db)
          return result, mech_context
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def create_port(self, context, port):
          self._before_create_port(context, port)
          result, mech_context = self._create_port_db(context, port)
          return self._after_create_port(context, result, mech_context)
  
      def _after_create_port(self, context, result, mech_context):
          # notify any plugin that is interested in port create events
          kwargs = {'context': context, 'port': result}
          registry.notify(resources.PORT, events.AFTER_CREATE, self, **kwargs)
  
          try:
              self.mechanism_manager.create_port_postcommit(mech_context)
          except ml2_exc.MechanismDriverError:
              with excutils.save_and_reraise_exception():
                  LOG.error(_LE("mechanism_manager.create_port_postcommit "
                                "failed, deleting port '%s'"), result['id'])
                  self.delete_port(context, result['id'], l3_port_check=False)
          try:
              bound_context = self._bind_port_if_needed(mech_context)
          except ml2_exc.MechanismDriverError:
              with excutils.save_and_reraise_exception():
                  LOG.error(_LE("_bind_port_if_needed "
                                "failed, deleting port '%s'"), result['id'])
                  self.delete_port(context, result['id'], l3_port_check=False)
  
          return bound_context.current
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def create_port_bulk(self, context, ports):
          objects = self._create_bulk_ml2(attributes.PORT, context, ports)
          return [obj['result'] for obj in objects]
  
      # TODO(yalei) - will be simplified after security group and address pair be
      # converted to ext driver too.
      def _portsec_ext_port_update_processing(self, updated_port, context, port,
                                              id):
          port_security = ((updated_port.get(psec.PORTSECURITY) is None) or
                           updated_port[psec.PORTSECURITY])
  
          if port_security:
              return
  
          # check the address-pairs
          if self._check_update_has_allowed_address_pairs(port):
              #  has address pairs in request
              raise addr_pair.AddressPairAndPortSecurityRequired()
          elif (not
           self._check_update_deletes_allowed_address_pairs(port)):
              # not a request for deleting the address-pairs
              updated_port[addr_pair.ADDRESS_PAIRS] = (
                      self.get_allowed_address_pairs(context, id))
  
              # check if address pairs has been in db, if address pairs could
              # be put in extension driver, we can refine here.
              if updated_port[addr_pair.ADDRESS_PAIRS]:
                  raise addr_pair.AddressPairAndPortSecurityRequired()
  
          # checks if security groups were updated adding/modifying
          # security groups, port security is set
          if self._check_update_has_security_groups(port):
              raise psec.PortSecurityAndIPRequiredForSecurityGroups()
          elif (not
            self._check_update_deletes_security_groups(port)):
              # Update did not have security groups passed in. Check
              # that port does not have any security groups already on it.
              filters = {'port_id': [id]}
              security_groups = (
                  super(Ml2Plugin, self)._get_port_security_group_bindings(
                          context, filters)
                       )
              if security_groups:
                  raise psec.PortSecurityPortHasSecurityGroup()
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def update_port(self, context, id, port):
          attrs = port[attributes.PORT]
          need_port_update_notify = False
          bound_mech_contexts = []
          with db_api.context_manager.writer.using(context):
              port_db = self._get_port(context, id)
              binding = port_db.port_binding
              if not binding:
                  raise exc.PortNotFound(port_id=id)
              mac_address_updated = self._check_mac_update_allowed(
                  port_db, attrs, binding)
              need_port_update_notify |= mac_address_updated
              original_port = self._make_port_dict(port_db)
              updated_port = super(Ml2Plugin, self).update_port(context, id,
                                                                port)
              self.extension_manager.process_update_port(context, attrs,
                                                         updated_port)
              self._portsec_ext_port_update_processing(updated_port, context,
                                                       port, id)
  
              if (psec.PORTSECURITY in attrs) and (
                          original_port[psec.PORTSECURITY] !=
                          updated_port[psec.PORTSECURITY]):
                  need_port_update_notify = True
              # TODO(QoS): Move out to the extension framework somehow.
              # Follow https://review.openstack.org/#/c/169223 for a solution.
              if (qos_consts.QOS_POLICY_ID in attrs and
                      original_port[qos_consts.QOS_POLICY_ID] !=
                      updated_port[qos_consts.QOS_POLICY_ID]):
                  need_port_update_notify = True
  
              if addr_pair.ADDRESS_PAIRS in attrs:
                  need_port_update_notify |= (
                      self.update_address_pairs_on_port(context, id, port,
                                                        original_port,
                                                        updated_port))
              need_port_update_notify |= self.update_security_group_on_port(
                  context, id, port, original_port, updated_port)
              network = self.get_network(context, original_port['network_id'])
              need_port_update_notify |= self._update_extra_dhcp_opts_on_port(
                  context, id, port, updated_port)
              levels = db.get_binding_levels(context, id, binding.host)
              # one of the operations above may have altered the model call
              # _make_port_dict again to ensure latest state is reflected so mech
              # drivers, callback handlers, and the API caller see latest state.
              # We expire here to reflect changed relationships on the obj.
              # Repeatable read will ensure we still get the state from this
              # transaction in spite of concurrent updates/deletes.
              context.session.expire(port_db)
              updated_port.update(self._make_port_dict(port_db))
              mech_context = driver_context.PortContext(
                  self, context, updated_port, network, binding, levels,
                  original_port=original_port)
              need_port_update_notify |= self._process_port_binding(
                  mech_context, attrs)
  
              kwargs = {
                  'context': context,
                  'port': updated_port,
                  'original_port': original_port,
              }
              registry.notify(
                  resources.PORT, events.PRECOMMIT_UPDATE, self, **kwargs)
  
              # For DVR router interface ports we need to retrieve the
              # DVRPortbinding context instead of the normal port context.
              # The normal Portbinding context does not have the status
              # of the ports that are required by the l2pop to process the
              # postcommit events.
  
              # NOTE:Sometimes during the update_port call, the DVR router
              # interface port may not have the port binding, so we cannot
              # create a generic bindinglist that will address both the
              # DVR and non-DVR cases here.
              # TODO(Swami): This code need to be revisited.
              if port_db['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
                  dist_binding_list = db.get_distributed_port_bindings(context,
                                                                       id)
                  for dist_binding in dist_binding_list:
                      levels = db.get_binding_levels(context, id,
                                                     dist_binding.host)
                      dist_mech_context = driver_context.PortContext(
                          self, context, updated_port, network,
                          dist_binding, levels, original_port=original_port)
                      self.mechanism_manager.update_port_precommit(
                          dist_mech_context)
                      bound_mech_contexts.append(dist_mech_context)
              else:
                  self.mechanism_manager.update_port_precommit(mech_context)
                  self._setup_dhcp_agent_provisioning_component(
                      context, updated_port)
                  bound_mech_contexts.append(mech_context)
  
          # Notifications must be sent after the above transaction is complete
          kwargs = {
              'context': context,
              'port': updated_port,
              'mac_address_updated': mac_address_updated,
              'original_port': original_port,
          }
          registry.notify(resources.PORT, events.AFTER_UPDATE, self, **kwargs)
  
          # Note that DVR Interface ports will have bindings on
          # multiple hosts, and so will have multiple mech_contexts,
          # while other ports typically have just one.
          # Since bound_mech_contexts has both the DVR and non-DVR
          # contexts we can manage just with a single for loop.
          try:
              for mech_context in bound_mech_contexts:
                  self.mechanism_manager.update_port_postcommit(
                      mech_context)
          except ml2_exc.MechanismDriverError:
              LOG.error(_LE("mechanism_manager.update_port_postcommit "
                            "failed for port %s"), id)
  
          self.check_and_notify_security_group_member_changed(
              context, original_port, updated_port)
          need_port_update_notify |= self.is_security_group_member_updated(
              context, original_port, updated_port)
  
          if original_port['admin_state_up'] != updated_port['admin_state_up']:
              need_port_update_notify = True
          # NOTE: In the case of DVR ports, the port-binding is done after
          # router scheduling when sync_routers is called and so this call
          # below may not be required for DVR routed interfaces. But still
          # since we don't have the mech_context for the DVR router interfaces
          # at certain times, we just pass the port-context and return it, so
          # that we don't disturb other methods that are expecting a return
          # value.
          bound_context = self._bind_port_if_needed(
              mech_context,
              allow_notify=True,
              need_notify=need_port_update_notify)
          return bound_context.current
  
      def _process_distributed_port_binding(self, mech_context, context, attrs):
          plugin_context = mech_context._plugin_context
          binding = mech_context._binding
          port = mech_context.current
          port_id = port['id']
  
          if binding.vif_type != portbindings.VIF_TYPE_UNBOUND:
              binding.vif_details = ''
              binding.vif_type = portbindings.VIF_TYPE_UNBOUND
              if binding.host:
                  db.clear_binding_levels(plugin_context, port_id, binding.host)
              binding.host = ''
  
          self._update_port_dict_binding(port, binding)
          binding.host = attrs and attrs.get(portbindings.HOST_ID)
          binding.router_id = attrs and attrs.get('device_id')
          # merge into session to reflect changes
          plugin_context.session.merge(binding)
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def update_distributed_port_binding(self, context, id, port):
          attrs = port[attributes.PORT]
  
          host = attrs and attrs.get(portbindings.HOST_ID)
          host_set = validators.is_attr_set(host)
  
          if not host_set:
              LOG.error(_LE("No Host supplied to bind DVR Port %s"), id)
              return
  
          binding = db.get_distributed_port_binding_by_host(context,
                                                            id, host)
          device_id = attrs and attrs.get('device_id')
          router_id = binding and binding.get('router_id')
          update_required = (not binding or
              binding.vif_type == portbindings.VIF_TYPE_BINDING_FAILED or
              router_id != device_id)
          if update_required:
              try:
                  with db_api.context_manager.writer.using(context):
                      orig_port = self.get_port(context, id)
                      if not binding:
                          binding = db.ensure_distributed_port_binding(
                              context, id, host, router_id=device_id)
                      network = self.get_network(context,
                                                 orig_port['network_id'])
                      levels = db.get_binding_levels(context, id, host)
                      mech_context = driver_context.PortContext(self,
                          context, orig_port, network,
                          binding, levels, original_port=orig_port)
                      self._process_distributed_port_binding(
                          mech_context, context, attrs)
              except (os_db_exception.DBReferenceError, exc.PortNotFound):
                  LOG.debug("DVR Port %s has been deleted concurrently", id)
                  return
              self._bind_port_if_needed(mech_context)
  
      def _pre_delete_port(self, context, port_id, port_check):
          """Do some preliminary operations before deleting the port."""
          LOG.debug("Deleting port %s", port_id)
          try:
              # notify interested parties of imminent port deletion;
              # a failure here prevents the operation from happening
              kwargs = {
                  'context': context,
                  'port_id': port_id,
                  'port_check': port_check
              }
              registry.notify(
                  resources.PORT, events.BEFORE_DELETE, self, **kwargs)
          except exceptions.CallbackFailure as e:
              # NOTE(armax): preserve old check's behavior
              if len(e.errors) == 1:
                  raise e.errors[0].error
              raise exc.ServicePortInUse(port_id=port_id, reason=e)
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def delete_port(self, context, id, l3_port_check=True):
          self._pre_delete_port(context, id, l3_port_check)
          # TODO(armax): get rid of the l3 dependency in the with block
          router_ids = []
          l3plugin = directory.get_plugin(const.L3)
  
          with db_api.context_manager.writer.using(context):
              try:
                  port_db = self._get_port(context, id)
                  binding = port_db.port_binding
              except exc.PortNotFound:
                  LOG.debug("The port '%s' was deleted", id)
                  return
              port = self._make_port_dict(port_db)
  
              network = self.get_network(context, port['network_id'])
              bound_mech_contexts = []
              device_owner = port['device_owner']
              if device_owner == const.DEVICE_OWNER_DVR_INTERFACE:
                  bindings = db.get_distributed_port_bindings(context,
                                                              id)
                  for bind in bindings:
                      levels = db.get_binding_levels(context, id,
                                                     bind.host)
                      mech_context = driver_context.PortContext(
                          self, context, port, network, bind, levels)
                      self.mechanism_manager.delete_port_precommit(mech_context)
                      bound_mech_contexts.append(mech_context)
              else:
                  levels = db.get_binding_levels(context, id,
                                                 binding.host)
                  mech_context = driver_context.PortContext(
                      self, context, port, network, binding, levels)
                  self.mechanism_manager.delete_port_precommit(mech_context)
                  bound_mech_contexts.append(mech_context)
              if l3plugin:
                  router_ids = l3plugin.disassociate_floatingips(
                      context, id, do_notify=False)
  
              LOG.debug("Calling delete_port for %(port_id)s owned by %(owner)s",
                        {"port_id": id, "owner": device_owner})
              super(Ml2Plugin, self).delete_port(context, id)
  
          self._post_delete_port(
              context, port, router_ids, bound_mech_contexts)
  
      def _post_delete_port(
          self, context, port, router_ids, bound_mech_contexts):
          kwargs = {
              'context': context,
              'port': port,
              'router_ids': router_ids,
          }
          registry.notify(resources.PORT, events.AFTER_DELETE, self, **kwargs)
          try:
              # Note that DVR Interface ports will have bindings on
              # multiple hosts, and so will have multiple mech_contexts,
              # while other ports typically have just one.
              for mech_context in bound_mech_contexts:
                  self.mechanism_manager.delete_port_postcommit(mech_context)
          except ml2_exc.MechanismDriverError:
              # TODO(apech) - One or more mechanism driver failed to
              # delete the port.  Ideally we'd notify the caller of the
              # fact that an error occurred.
              LOG.error(_LE("mechanism_manager.delete_port_postcommit failed for"
                            " port %s"), port['id'])
          self.notifier.port_delete(context, port['id'])
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive(context_var_name='plugin_context')
      def get_bound_port_context(self, plugin_context, port_id, host=None,
                                 cached_networks=None):
          with db_api.context_manager.reader.using(plugin_context) as session:
              try:
                  port_db = (session.query(models_v2.Port).
                             enable_eagerloads(False).
                             filter(models_v2.Port.id.startswith(port_id)).
                             one())
              except sa_exc.NoResultFound:
                  LOG.info(_LI("No ports have port_id starting with %s"),
                           port_id)
                  return
              except sa_exc.MultipleResultsFound:
                  LOG.error(_LE("Multiple ports have port_id starting with %s"),
                            port_id)
                  return
              port = self._make_port_dict(port_db)
              network = (cached_networks or {}).get(port['network_id'])
  
              if not network:
                  network = self.get_network(plugin_context, port['network_id'])
  
              if port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
                  binding = db.get_distributed_port_binding_by_host(
                      plugin_context, port['id'], host)
                  if not binding:
                      LOG.error(_LE("Binding info for DVR port %s not found"),
                                port_id)
                      return None
                  levels = db.get_binding_levels(plugin_context,
                                                 port_db.id, host)
                  port_context = driver_context.PortContext(
                      self, plugin_context, port, network, binding, levels)
              else:
                  # since eager loads are disabled in port_db query
                  # related attribute port_binding could disappear in
                  # concurrent port deletion.
                  # It's not an error condition.
                  binding = port_db.port_binding
                  if not binding:
                      LOG.info(_LI("Binding info for port %s was not found, "
                                   "it might have been deleted already."),
                               port_id)
                      return
                  levels = db.get_binding_levels(plugin_context, port_db.id,
                                                 port_db.port_binding.host)
                  port_context = driver_context.PortContext(
                      self, plugin_context, port, network, binding, levels)
  
          return self._bind_port_if_needed(port_context)
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive(context_var_name='plugin_context')
      def get_bound_ports_contexts(self, plugin_context, dev_ids, host=None):
          result = {}
          with db_api.context_manager.reader.using(plugin_context):
              dev_to_full_pids = db.partial_port_ids_to_full_ids(
                  plugin_context, dev_ids)
              # get all port objects for IDs
              port_dbs_by_id = db.get_port_db_objects(
                  plugin_context, dev_to_full_pids.values())
              # get all networks for PortContext construction
              netctxs_by_netid = self.get_network_contexts(
                  plugin_context,
                  {p.network_id for p in port_dbs_by_id.values()})
              for dev_id in dev_ids:
                  port_id = dev_to_full_pids.get(dev_id)
                  port_db = port_dbs_by_id.get(port_id)
                  if (not port_id or not port_db or
                          port_db.network_id not in netctxs_by_netid):
                      result[dev_id] = None
                      continue
                  port = self._make_port_dict(port_db)
                  if port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
                      binding = db.get_distributed_port_binding_by_host(
                          plugin_context, port['id'], host)
                      bindlevelhost_match = host
                  else:
                      binding = port_db.port_binding
                      bindlevelhost_match = binding.host if binding else None
                  if not binding:
                      LOG.info(_LI("Binding info for port %s was not found, "
                                   "it might have been deleted already."),
                               port_id)
                      result[dev_id] = None
                      continue
                  levels = [l for l in port_db.binding_levels
                            if l.host == bindlevelhost_match]
                  levels = sorted(levels, key=lambda l: l.level)
                  network_ctx = netctxs_by_netid.get(port_db.network_id)
                  port_context = driver_context.PortContext(
                      self, plugin_context, port, network_ctx, binding, levels)
                  result[dev_id] = port_context
  
          return {d: self._bind_port_if_needed(pctx) if pctx else None
                  for d, pctx in result.items()}
  
      @utils.transaction_guard
      @db_api.retry_if_session_inactive()
      def update_port_status(self, context, port_id, status, host=None,
                             network=None):
          """
          Returns port_id (non-truncated uuid) if the port exists.
          Otherwise returns None.
          network can be passed in to avoid another get_network call if
          one was already performed by the caller.
          """
          updated = False
          with db_api.context_manager.writer.using(context):
              port = db.get_port(context, port_id)
              if not port:
                  LOG.debug("Port %(port)s update to %(val)s by agent not found",
                            {'port': port_id, 'val': status})
                  return None
              if (port.status != status and
                  port['device_owner'] != const.DEVICE_OWNER_DVR_INTERFACE):
                  original_port = self._make_port_dict(port)
                  port.status = status
                  # explicit flush before _make_port_dict to ensure extensions
                  # listening for db events can modify the port if necessary
                  context.session.flush()
                  updated_port = self._make_port_dict(port)
                  levels = db.get_binding_levels(context, port.id,
                                                 port.port_binding.host)
                  mech_context = driver_context.PortContext(
                      self, context, updated_port, network, port.port_binding,
                      levels, original_port=original_port)
                  self.mechanism_manager.update_port_precommit(mech_context)
                  updated = True
              elif port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
                  binding = db.get_distributed_port_binding_by_host(
                      context, port['id'], host)
                  if not binding:
                      return
                  binding.status = status
                  updated = True
  
          if (updated and
              port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE):
              with db_api.context_manager.writer.using(context):
                  port = db.get_port(context, port_id)
                  if not port:
                      LOG.warning(_LW("Port %s not found during update"),
                                  port_id)
                      return
                  original_port = self._make_port_dict(port)
                  network = network or self.get_network(
                      context, original_port['network_id'])
                  port.status = db.generate_distributed_port_status(context,
                                                                    port['id'])
                  updated_port = self._make_port_dict(port)
                  levels = db.get_binding_levels(context, port_id, host)
                  mech_context = (driver_context.PortContext(
                      self, context, updated_port, network,
                      binding, levels, original_port=original_port))
                  self.mechanism_manager.update_port_precommit(mech_context)
  
          if updated:
              self.mechanism_manager.update_port_postcommit(mech_context)
              kwargs = {'context': context, 'port': mech_context.current,
                        'original_port': original_port}
              if status == const.PORT_STATUS_ACTIVE:
                  # NOTE(kevinbenton): this kwarg was carried over from
                  # the RPC handler that used to call this. it's not clear
                  # who uses it so maybe it can be removed. added in commit
                  # 3f3874717c07e2b469ea6c6fd52bcb4da7b380c7
                  kwargs['update_device_up'] = True
              registry.notify(resources.PORT, events.AFTER_UPDATE, self,
                              **kwargs)
  
          if port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
              db.delete_distributed_port_binding_if_stale(context, binding)
  
          return port['id']
  
      @db_api.retry_if_session_inactive()
      def port_bound_to_host(self, context, port_id, host):
          if not host:
              return
          port = db.get_port(context, port_id)
          if not port:
              LOG.debug("No Port match for: %s", port_id)
              return
          if port['device_owner'] == const.DEVICE_OWNER_DVR_INTERFACE:
              bindings = db.get_distributed_port_bindings(context,
                                                          port_id)
              for b in bindings:
                  if b.host == host:
                      return port
              LOG.debug("No binding found for DVR port %s", port['id'])
              return
          else:
              port_host = db.get_port_binding_host(context, port_id)
              return port if (port_host == host) else None
  
      @db_api.retry_if_session_inactive()
      def get_ports_from_devices(self, context, devices):
          port_ids_to_devices = dict(
              (self._device_to_port_id(context, device), device)
              for device in devices)
          port_ids = list(port_ids_to_devices.keys())
          ports = db.get_ports_and_sgs(context, port_ids)
          for port in ports:
              # map back to original requested id
              port_id = next((port_id for port_id in port_ids
                             if port['id'].startswith(port_id)), None)
              port['device'] = port_ids_to_devices.get(port_id)
  
          return ports
  
      @staticmethod
      def _device_to_port_id(context, device):
          # REVISIT(rkukura): Consider calling into MechanismDrivers to
          # process device names, or having MechanismDrivers supply list
          # of device prefixes to strip.
          for prefix in n_const.INTERFACE_PREFIXES:
              if device.startswith(prefix):
                  return device[len(prefix):]
          # REVISIT(irenab): Consider calling into bound MD to
          # handle the get_device_details RPC
          if not uuidutils.is_uuid_like(device):
              port = db.get_port_from_device_mac(context, device)
              if port:
                  return port.id
          return device
  
      def filter_hosts_with_network_access(
              self, context, network_id, candidate_hosts):
          segments = segments_db.get_network_segments(context, network_id)
          return self.mechanism_manager.filter_hosts_with_segment_access(
              context, segments, candidate_hosts, self.get_agents)
  
      def check_segment_for_agent(self, segment, agent):
          for mech_driver in self.mechanism_manager.ordered_mech_drivers:
              driver_agent_type = getattr(mech_driver.obj, 'agent_type', None)
              if driver_agent_type and driver_agent_type == agent['agent_type']:
                  if mech_driver.obj.check_segment_for_agent(segment, agent):
                      return True
          return False
  
      @registry.receives(resources.SEGMENT, (events.PRECOMMIT_CREATE,
                                             events.PRECOMMIT_DELETE,
                                             events.AFTER_CREATE,
                                             events.AFTER_DELETE))
      def _handle_segment_change(self, rtype, event, trigger, context, segment):
          if (event == events.PRECOMMIT_CREATE and
              not isinstance(trigger, segments_plugin.Plugin)):
              # TODO(xiaohhui): Now, when create network, ml2 will reserve
              # segment and trigger this event handler. This event handler
              # will reserve segment again, which will lead to error as the
              # segment has already been reserved. This check could be removed
              # by unifying segment creation procedure.
              return
  
          network_id = segment.get('network_id')
  
          if event == events.PRECOMMIT_CREATE:
              updated_segment = self.type_manager.reserve_network_segment(
                  context, segment)
              # The segmentation id might be from ML2 type driver, update it
              # in the original segment.
              segment[api.SEGMENTATION_ID] = updated_segment[api.SEGMENTATION_ID]
          elif event == events.PRECOMMIT_DELETE:
              self.type_manager.release_network_segment(context, segment)
  
          try:
              self._notify_mechanism_driver_for_segment_change(
                  event, context, network_id)
          except ml2_exc.MechanismDriverError:
              with excutils.save_and_reraise_exception():
                  LOG.error(_LE("mechanism_manager error occurred when "
                                "handle event %(event)s for segment "
                                "'%(segment)s'"),
                            {'event': event, 'segment': segment['id']})
  
      def _notify_mechanism_driver_for_segment_change(self, event,
                                                      context, network_id):
          network_with_segments = self.get_network(context, network_id)
          mech_context = driver_context.NetworkContext(
              self, context, network_with_segments,
              original_network=network_with_segments)
          if (event == events.PRECOMMIT_CREATE or
              event == events.PRECOMMIT_DELETE):
              self.mechanism_manager.update_network_precommit(mech_context)
          elif event == events.AFTER_CREATE or event == events.AFTER_DELETE:
              self.mechanism_manager.update_network_postcommit(mech_context)
  