# Copyright (c) 2012 OpenStack Foundation.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import functools

import netaddr
from neutron_lib.api import converters
from neutron_lib.api.definitions import external_net as extnet_def
from neutron_lib.api.definitions import ip_allocation as ipalloc_apidef
from neutron_lib.api.definitions import port as port_def
from neutron_lib.api.definitions import portbindings as portbindings_def
from neutron_lib.api.definitions import provider_net as pnet_def
from neutron_lib.api.definitions import subnetpool as subnetpool_def
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
from neutron_lib import context as ctx
from neutron_lib.db import api as db_api
from neutron_lib.db import model_query
from neutron_lib.db import resource_extend
from neutron_lib.db import utils as ndb_utils
from neutron_lib import exceptions as exc
from neutron_lib.exceptions import address_scope as addr_scope_exc
from neutron_lib.exceptions import l3 as l3_exc
from neutron_lib.plugins import constants as plugin_constants
from neutron_lib.plugins import directory
from oslo_config import cfg
from oslo_db import exception as os_db_exc
from oslo_log import log as logging
from oslo_utils import excutils
from oslo_utils import uuidutils
from sqlalchemy import and_
from sqlalchemy import exc as sql_exc
from sqlalchemy import func
from sqlalchemy import not_

from neutron._i18n import _
from neutron.api.rpc.agentnotifiers import l3_rpc_agent_api
from neutron.common import _constants
from neutron.common import experimental
from neutron.common import ipv6_utils
from neutron.common import utils
from neutron.conf import experimental as c_exp
from neutron.db import db_base_plugin_common
from neutron.db import ipam_pluggable_backend
from neutron.db.models import segment as segment_db
from neutron.db import models_v2
from neutron.db import rbac_db_mixin as rbac_mixin
from neutron.db import rbac_db_models
from neutron.db import standardattrdescription_db as stattr_db
from neutron.extensions import subnetpool_prefix_ops
from neutron import ipam
from neutron.ipam import exceptions as ipam_exc
from neutron.ipam import subnet_alloc
from neutron import neutron_plugin_base_v2
from neutron.objects import address_scope as address_scope_obj
from neutron.objects import base as base_obj
from neutron.objects import network as network_obj
from neutron.objects import ports as port_obj
from neutron.objects import subnet as subnet_obj
from neutron.objects import subnetpool as subnetpool_obj


LOG = logging.getLogger(__name__)


def _ensure_subnet_not_used(context, subnet_id):
    models_v2.Subnet.write_lock_register(
        context, exc.SubnetInUse(subnet_id=subnet_id), id=subnet_id)
    try:
        registry.publish(
            resources.SUBNET, events.BEFORE_DELETE, None,
            payload=events.DBEventPayload(context, resource_id=subnet_id))
    except exceptions.CallbackFailure as e:
        raise exc.SubnetInUse(subnet_id=subnet_id, reason=e)


def _update_subnetpool_dict(orig_pool, new_pool):
    updated = {k: v for k, v in orig_pool.to_dict().items()
               if k not in orig_pool.synthetic_fields or k == 'shared'}

    new_pool = new_pool.copy()
    new_prefixes = new_pool.pop('prefixes', constants.ATTR_NOT_SPECIFIED)
    for k, v in new_pool.items():
        if k not in orig_pool.fields_no_update:
            updated[k] = v
    if new_prefixes is not constants.ATTR_NOT_SPECIFIED:
        orig_ip_set = netaddr.IPSet(orig_pool.prefixes)
        new_ip_set = netaddr.IPSet(new_prefixes)
        if not orig_ip_set.issubset(new_ip_set):
            msg = _("Existing prefixes must be "
                    "a subset of the new prefixes")
            raise exc.IllegalSubnetPoolPrefixUpdate(msg=msg)
        new_ip_set.compact()
        updated['prefixes'] = [str(prefix.cidr)
                               for prefix in new_ip_set.iter_cidrs()]
    else:
        updated['prefixes'] = [str(prefix)
                               for prefix in orig_pool.prefixes]
    return updated


def _port_query_hook(context, original_model, query):
    # Apply the port query only in non-admin and non-advsvc context
    if ndb_utils.model_query_scope_is_project(context, original_model):
        query = query.join(models_v2.Network,
                           models_v2.Network.id == models_v2.Port.network_id)
    return query


def _port_filter_hook(context, original_model, conditions):
    # Apply the port filter only in non-admin and non-advsvc context
    if ndb_utils.model_query_scope_is_project(context, original_model):
        conditions |= and_(
            models_v2.Network.project_id == context.project_id)
    return conditions


def _network_result_filter_hook(query, filters):
    # This filter matches the provider network attributes, defined in
    # ``neutron_lib.api.definitions.provider_net.ATTRIBUTES``.
    attr_to_field = {
        pnet_def.NETWORK_TYPE: segment_db.NetworkSegment.network_type,
        pnet_def.PHYSICAL_NETWORK: segment_db.NetworkSegment.physical_network,
        pnet_def.SEGMENTATION_ID: segment_db.NetworkSegment.segmentation_id
    }

    if any(attr for attr in pnet_def.ATTRIBUTES if attr in filters):
        query = query.join(
            segment_db.NetworkSegment,
            segment_db.NetworkSegment.network_id == models_v2.Network.id)
    for attr in (attr for attr in pnet_def.ATTRIBUTES if attr in filters):
        value = filters[attr]
        field = attr_to_field[attr]
        if utils.is_iterable_not_string(value):
            query = query.filter(field.in_(value))
        else:
            query = query.filter(field == value)

    return query


@registry.has_registry_receivers
class NeutronDbPluginV2(db_base_plugin_common.DbBasePluginCommon,
                        neutron_plugin_base_v2.NeutronPluginBaseV2,
                        rbac_mixin.RbacPluginMixin,
                        stattr_db.StandardAttrDescriptionMixin):
    """V2 Neutron plugin interface implementation using SQLAlchemy models.

    Whenever a non-read call happens the plugin will call an event handler
    class method (e.g., network_created()).  The result is that this class
    can be sub-classed by other classes that add custom behaviors on certain
    events.
    """

    # 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
    # This attribute specifies whether the plugin supports or not
    # filter validations. Name mangling is used in
    # order to ensure it is qualified by class
    __filter_validation_support = False

    def has_native_datastore(self):
        return True

    def __new__(cls, *args, **kwargs):
        model_query.register_hook(
            models_v2.Port,
            "port",
            query_hook=_port_query_hook,
            filter_hook=_port_filter_hook,
            result_filters=None)
        model_query.register_hook(
            models_v2.Network,
            'network',
            query_hook=None,
            filter_hook=None,
            result_filters=_network_result_filter_hook)
        return super().__new__(cls, *args, **kwargs)

    @staticmethod
    def _validate_ipv6_pd():
        try:
            if cfg.CONF.ipv6_pd_enabled:
                experimental.validate_experimental_enabled(
                    c_exp.EXPERIMENTAL_IPV6_PD)
        except cfg.NoSuchOptError:
            pass

    def __init__(self):
        self._validate_ipv6_pd()
        self.set_ipam_backend()
        if (cfg.CONF.notify_nova_on_port_status_changes or
                cfg.CONF.notify_nova_on_port_data_changes):
            # Import nova conditionally to support the use case of Neutron
            # being used outside of an OpenStack context.
            # pylint: disable=import-outside-toplevel
            from neutron.notifiers import nova
            self.nova_notifier = nova.Notifier.get_instance()
            # NOTE(arosen) These event listeners are here to hook into when
            # port status changes and notify nova about their change.
            if cfg.CONF.notify_nova_on_port_status_changes:
                db_api.sqla_listen(models_v2.Port, 'after_insert',
                                   self.nova_notifier.send_port_status)
                db_api.sqla_listen(models_v2.Port, 'after_update',
                                   self.nova_notifier.send_port_status)
                db_api.sqla_listen(
                    models_v2.Port.status, 'set',
                    self.nova_notifier.record_port_status_changed)
        if cfg.CONF.ironic.enable_notifications:
            # Import ironic notifier conditionally
            # pylint: disable=import-outside-toplevel
            from neutron.notifiers import ironic
            self.ironic_notifier = ironic.Notifier.get_instance()

    @registry.receives(resources.RBAC_POLICY, [events.BEFORE_CREATE,
                                               events.BEFORE_UPDATE,
                                               events.BEFORE_DELETE])
    def validate_network_rbac_policy_change(self, resource, event, trigger,
                                            payload=None):
        return self._validate_network_rbac_policy_change(
            resource, event, trigger, payload.context, payload)

    @db_api.retry_if_session_inactive()
    def _validate_network_rbac_policy_change(self, resource, event, trigger,
                                             context, payload):
        """Validates network RBAC policy changes.

        On creation, verify that the creator is an admin or that it owns the
        network it is sharing.

        On update and delete, make sure the tenant losing access does not have
        resources that depend on that access.
        """
        object_type = payload.metadata.get('object_type')
        policy = (payload.request_body if event == events.BEFORE_CREATE
                  else payload.latest_state)

        if (object_type != 'network' or
                policy['action'] != rbac_db_models.ACCESS_SHARED):
            # we only care about shared network policies
            return
        # The object a policy targets cannot be changed so we can look
        # at the original network for the update event as well.
        net = self._get_network(context, policy['object_id'])
        if event in (events.BEFORE_CREATE, events.BEFORE_UPDATE):
            # we still have to verify that the caller owns the network because
            # _get_network will succeed on a shared network
            if not context.is_admin and net['tenant_id'] != context.tenant_id:
                msg = _("Only admins can manipulate policies on networks "
                        "they do not own")
                raise exc.InvalidInput(error_message=msg)

        tenant_to_check = None
        self_sharing = policy['target_project'] == net['tenant_id']
        if self_sharing:
            return
        if event == events.BEFORE_UPDATE:
            new_tenant = payload.request_body['target_project']
            if policy['target_project'] != new_tenant:
                tenant_to_check = policy['target_project']

        if event == events.BEFORE_DELETE:
            tenant_to_check = policy['target_project']

        if tenant_to_check:
            self.ensure_no_project_ports_on_network(
                context, net['id'], net['tenant_id'], tenant_to_check)

    def ensure_no_project_ports_on_network(self, context, network_id,
                                           net_tenant_id, tenant_id):
        elevated = context.elevated()
        with db_api.CONTEXT_READER.using(elevated):
            ports = model_query.query_with_hooks(
                elevated, models_v2.Port).filter(
                    models_v2.Port.network_id == network_id)
            if tenant_id == '*':
                # for the wildcard we need to get all of the rbac entries to
                # see if any allow the remaining ports on the network.
                # any port with another RBAC entry covering it or one belonging
                # to the same tenant as the network owner is ok
                other_rbac_objs = network_obj.NetworkRBAC.get_objects(
                    elevated, object_id=network_id,
                    action=rbac_db_models.ACCESS_SHARED)
                allowed_tenants = [rbac['target_project'] for rbac
                                   in other_rbac_objs
                                   if rbac.target_project != tenant_id]
                allowed_tenants.append(net_tenant_id)
                ports = ports.filter(
                    ~models_v2.Port.tenant_id.in_(allowed_tenants))
                # Filter any port with project_id=''. These ports are related
                # to floating IPs, router ports (gateway, SNAT, FIP agent, HA
                # interface).
                ports = ports.filter(models_v2.Port.project_id.notin_(['']))
            else:
                # if there is a wildcard rule, we can return early because it
                # allows any ports
                if network_obj.NetworkRBAC.get_object(
                        elevated, object_id=network_id,
                        action=rbac_db_models.ACCESS_SHARED,
                        target_project='*'):
                    return
                ports = ports.filter(models_v2.Port.project_id == tenant_id)
            if ports.count():
                raise exc.InvalidSharedSetting(network=network_id)

    def set_ipam_backend(self):
        self.ipam = ipam_pluggable_backend.IpamPluggableBackend()

    def _validate_host_route(self, route, ip_version):
        try:
            netaddr.IPNetwork(route['destination'])
            netaddr.IPAddress(route['nexthop'])
        except netaddr.core.AddrFormatError:
            err_msg = _("Invalid route: %s") % route
            raise exc.InvalidInput(error_message=err_msg)
        except ValueError:
            # netaddr.IPAddress would raise this
            err_msg = _("Invalid route: %s") % route
            raise exc.InvalidInput(error_message=err_msg)
        self._validate_ip_version(ip_version, route['nexthop'], 'nexthop')
        self._validate_ip_version(ip_version, route['destination'],
                                  'destination')

    def _validate_shared_update(self, context, id, original, updated):
        # The only case that needs to be validated is when 'shared'
        # goes from True to False
        if updated['shared'] == original.shared or updated['shared']:
            return
        ports = model_query.query_with_hooks(
            context, models_v2.Port).filter(models_v2.Port.network_id == id)
        ports = ports.filter(not_(models_v2.Port.device_owner.startswith(
            constants.DEVICE_OWNER_NETWORK_PREFIX)))
        subnets = subnet_obj.Subnet.get_objects(context, network_id=id)
        tenant_ids = set([port['tenant_id'] for port in ports] +
                         [subnet['tenant_id'] for subnet in subnets])
        # raise if multiple tenants found or if the only tenant found
        # is not the owner of the network
        if (len(tenant_ids) > 1 or len(tenant_ids) == 1 and
                original.tenant_id not in tenant_ids):
            self._validate_projects_have_access_to_network(
                original, tenant_ids)

    def _validate_projects_have_access_to_network(self, network, project_ids):
        ctx_admin = ctx.get_admin_context()
        other_rbac_objs = network_obj.NetworkRBAC.get_objects(
            ctx_admin, object_id=network.id,
            action=rbac_db_models.ACCESS_SHARED)
        allowed_projects = {rbac['target_project'] for rbac in other_rbac_objs
                            if rbac.target_project != '*'}
        allowed_projects.add(network.project_id)
        if project_ids - allowed_projects:
            raise exc.InvalidSharedSetting(network=network.name)

    def _validate_ipv6_attributes(self, subnet, cur_subnet, has_cidr):
        if cur_subnet:
            self._validate_ipv6_update_dhcp(subnet, cur_subnet)
            return
        ra_mode_set = validators.is_attr_set(subnet.get('ipv6_ra_mode'))
        address_mode_set = validators.is_attr_set(
            subnet.get('ipv6_address_mode'))
        self._validate_ipv6_dhcp(ra_mode_set, address_mode_set,
                                 subnet['enable_dhcp'])
        if ra_mode_set and address_mode_set:
            self._validate_ipv6_combination(subnet['ipv6_ra_mode'],
                                            subnet['ipv6_address_mode'])
        if has_cidr and (address_mode_set or ra_mode_set):
            self._validate_eui64_applicable(subnet)

    def _validate_eui64_applicable(self, subnet):
        # Per RFC 4862, section 5.5.3, prefix length and interface
        # id together should be equal to 128. Currently neutron supports
        # EUI64 interface id only, thus limiting the prefix
        # length to be 64 only.
        if ipv6_utils.is_auto_address_subnet(subnet):
            if netaddr.IPNetwork(subnet['cidr']).prefixlen != 64:
                msg = _('Invalid CIDR %s for IPv6 address mode. '
                        'OpenStack uses the EUI-64 address format, '
                        'which requires the prefix to be /64')
                raise exc.InvalidInput(
                    error_message=(msg % subnet['cidr']))

    def _validate_ipv6_combination(self, ra_mode, address_mode):
        if ra_mode != address_mode:
            msg = _("ipv6_ra_mode set to '%(ra_mode)s' with ipv6_address_mode "
                    "set to '%(addr_mode)s' is not valid. "
                    "If both attributes are set, they must be the same value"
                    ) % {'ra_mode': ra_mode, 'addr_mode': address_mode}
            raise exc.InvalidInput(error_message=msg)

    def _validate_ipv6_dhcp(self, ra_mode_set, address_mode_set, enable_dhcp):
        if (ra_mode_set or address_mode_set) and not enable_dhcp:
            msg = _("ipv6_ra_mode or ipv6_address_mode cannot be set when "
                    "enable_dhcp is set to False")
            raise exc.InvalidInput(error_message=msg)

    def _validate_ipv6_update_dhcp(self, subnet, cur_subnet):
        if ('enable_dhcp' in subnet and not subnet['enable_dhcp']):
            msg = _("Cannot disable enable_dhcp with "
                    "ipv6 attributes set")

            ra_mode_set = validators.is_attr_set(subnet.get('ipv6_ra_mode'))
            address_mode_set = validators.is_attr_set(
                subnet.get('ipv6_address_mode'))

            if ra_mode_set or address_mode_set:
                raise exc.InvalidInput(error_message=msg)

            old_ra_mode_set = validators.is_attr_set(
                cur_subnet.get('ipv6_ra_mode'))
            old_address_mode_set = validators.is_attr_set(
                cur_subnet.get('ipv6_address_mode'))

            if old_ra_mode_set or old_address_mode_set:
                raise exc.InvalidInput(error_message=msg)

    def _create_bulk(self, resource, context, request_items):
        objects = []
        collection = "%ss" % resource
        items = request_items[collection]
        try:
            with db_api.CONTEXT_WRITER.using(context):
                for item in items:
                    obj_creator = getattr(self, 'create_%s' % resource)
                    objects.append(obj_creator(context, item))
        except Exception:
            with excutils.save_and_reraise_exception():
                LOG.error("An exception occurred while creating "
                          "the %(resource)s:%(item)s",
                          {'resource': resource, 'item': item})
        return objects

    @db_api.retry_if_session_inactive()
    def create_network_bulk(self, context, networks):
        return self._create_bulk('network', context, networks)

    @db_api.retry_if_session_inactive()
    def create_network(self, context, network):
        """Handle creation of a single network."""
        net_db = self.create_network_db(context, network)
        return self._make_network_dict(net_db, process_extensions=False,
                                       context=context)

    def create_network_db(self, context, network):
        # single request processing
        n = network['network']
        # TODO(ralonsoh): "tenant_id" reference should be removed.
        project_id = n.get('project_id') or n['tenant_id']
        with db_api.CONTEXT_WRITER.using(context):
            args = {'tenant_id': project_id,
                    'id': n.get('id') or uuidutils.generate_uuid(),
                    'name': n['name'],
                    'mtu': n.get('mtu', 0),
                    'admin_state_up': n['admin_state_up'],
                    'status': n.get('status', constants.NET_STATUS_ACTIVE),
                    'description': n.get('description')}
            network = models_v2.Network(**args)
            context.session.add(network)
            if n['shared']:
                np_rbac_args = {'project_id': network.project_id,
                                'object_id': network.id,
                                'action': rbac_db_models.ACCESS_SHARED,
                                'target_project': '*'}
                np_rbac_obj = network_obj.NetworkRBAC(context, **np_rbac_args)
                np_rbac_obj.create()
        return network

    @db_api.retry_if_session_inactive()
    def update_network(self, context, id, network, db_network=None):
        n = network['network']
        # we dont't use DB objects not belonging to the current active session
        db_network = (db_network if db_api.is_session_active(context.session)
                      else None)
        with db_api.CONTEXT_WRITER.using(context):
            network = db_network or self._get_network(context, id)
            # validate 'shared' parameter
            if 'shared' in n:
                entry = None
                for item in network.rbac_entries:
                    if (item.action == rbac_db_models.ACCESS_SHARED and
                            item.target_project == '*'):
                        entry = item
                        break
                setattr(network, 'shared', bool(entry))
                self._validate_shared_update(context, id, network, n)
                update_shared = n.pop('shared')
                if update_shared and not entry:
                    np_rbac_args = {'project_id': network.project_id,
                                    'object_id': network.id,
                                    'action': rbac_db_models.ACCESS_SHARED,
                                    'target_project': '*'}
                    np_rbac_obj = network_obj.NetworkRBAC(context,
                                                          **np_rbac_args)
                    np_rbac_obj.create()
                elif not update_shared and entry:
                    network_obj.NetworkRBAC.delete_objects(
                        context, object_id=network.id,
                        action=rbac_db_models.ACCESS_SHARED,
                        target_project='*')

                # TODO(ihrachys) Below can be removed when we make sqlalchemy
                # event listeners in neutron_lib/db/api.py to refresh expired
                # attributes.
                #
                # First trigger expiration of rbac_entries.
                context.session.flush()
                # Then fetch state for _make_network_dict use outside session
                # context.
                getattr(network, 'rbac_entries')

            # validate 'mtu' parameter
            if 'mtu' in n:
                self._validate_change_network_mtu(context, id, n['mtu'])

            # The filter call removes attributes from the body received from
            # the API that are logically tied to network resources but are
            # stored in other database tables handled by extensions
            network.update(
                ndb_utils.filter_non_model_columns(n, models_v2.Network))
        return self._make_network_dict(network, context=context)

    def _validate_change_network_mtu(self, context, id, mtu):
        # can support either ip_version
        if mtu >= constants.IPV6_MIN_MTU:
            return

        subnets = self._get_subnets_by_network(context, id)
        if len(subnets) == 0:
            return

        # at least one subnet present, if below IPv4 minimum we fail early
        if mtu < constants.IPV4_MIN_MTU:
            raise exc.NetworkMTUSubnetConflict(
                net_id=id, mtu=constants.IPV4_MIN_MTU)

        # We do not need to check IPv4 subnets as they will have been
        # caught by above IPV4_MIN_MTU check
        for subnet in subnets:
            if (subnet.ip_version == constants.IP_VERSION_6 and
                    mtu < constants.IPV6_MIN_MTU):
                raise exc.NetworkMTUSubnetConflict(
                    net_id=id, mtu=constants.IPV6_MIN_MTU)

    def _ensure_network_not_in_use(self, context, net_id):
        non_auto_ports = context.session.query(
            models_v2.Port.id).filter_by(network_id=net_id).filter(
                ~models_v2.Port.device_owner.in_(
                    _constants.AUTO_DELETE_PORT_OWNERS))
        if non_auto_ports.count():
            ports = [port.id for port in non_auto_ports.all()]
            reason = _("There are one or more ports still in use on the "
                       "network, id for these ports is: %s" % ",".join(ports))
            raise exc.NetworkInUse(net_id=net_id, reason=reason)

    @db_api.retry_if_session_inactive()
    def delete_network(self, context, id):
        registry.publish(resources.NETWORK, events.BEFORE_DELETE, self,
                         payload=events.DBEventPayload(
                             context, resource_id=id))
        with db_api.CONTEXT_READER.using(context):
            self._ensure_network_not_in_use(context, id)
            auto_delete_port_ids = [p.id for p in context.session.query(
                models_v2.Port.id).filter_by(network_id=id).filter(
                    models_v2.Port.device_owner.in_(
                        _constants.AUTO_DELETE_PORT_OWNERS))]
        for port_id in auto_delete_port_ids:
            try:
                self.delete_port(context.elevated(), port_id)
            except exc.PortNotFound:
                # Don't raise if something else concurrently deleted the port
                LOG.debug("Ignoring PortNotFound when deleting port '%s'. "
                          "The port has already been deleted.", port_id)
        # clean up subnets
        subnets = self._get_subnets_by_network(context, id)
        with db_api.exc_to_retry(os_db_exc.DBReferenceError):
            # retry reference errors so we can check the port type and
            # cleanup if a network-owned port snuck in without failing
            for subnet in subnets:
                self._delete_subnet(context, subnet)
                registry.publish(
                    resources.SUBNET, events.AFTER_DELETE, self,
                    payload=events.DBEventPayload(
                        context,
                        resource_id=subnet['id'],
                        metadata={'for_net_delete': True},
                        states=(subnet.to_dict(),)))
            with db_api.CONTEXT_WRITER.using(context):
                network_db = self._get_network(context, id)
                network = self._make_network_dict(network_db, context=context)
                registry.publish(resources.NETWORK, events.PRECOMMIT_DELETE,
                                 self, payload=events.DBEventPayload(
                                     context, resource_id=id,
                                     states=(network,)))
                # We expire network_db here because precommit deletion
                # might have left the relationship stale, for example,
                # if we deleted a segment.
                context.session.expire(network_db)
                network_db = self._get_network(context, id)
                context.session.delete(network_db)
        registry.publish(resources.NETWORK, events.AFTER_DELETE,
                         self, payload=events.DBEventPayload(
                             context, resource_id=id, states=(network,)))

    @db_api.retry_if_session_inactive()
    def get_network(self, context, id, fields=None):
        network = self._get_network(context, id)
        return self._make_network_dict(network, fields, context=context)

    @db_api.retry_if_session_inactive()
    def _get_networks(self, context, filters=None, fields=None,
                      sorts=None, limit=None, marker=None,
                      page_reverse=False):
        marker_obj = ndb_utils.get_marker_obj(self, context, 'network',
                                              limit, marker)
        return model_query.get_collection(
            context, models_v2.Network,
            # if caller needs postprocessing, it should implement it explicitly
            dict_func=None,
            filters=filters, fields=fields,
            sorts=sorts,
            limit=limit,
            marker_obj=marker_obj,
            page_reverse=page_reverse)

    @db_api.retry_if_session_inactive()
    def get_networks(self, context, filters=None, fields=None,
                     sorts=None, limit=None, marker=None,
                     page_reverse=False):
        make_network_dict = functools.partial(self._make_network_dict,
                                              context=context)
        return [
            make_network_dict(net, fields)
            for net in self._get_networks(
                context, filters=filters, fields=fields, sorts=sorts,
                limit=limit, marker=marker, page_reverse=page_reverse)
        ]

    @db_api.retry_if_session_inactive()
    def get_networks_count(self, context, filters=None):
        return model_query.get_collection_count(
            context, models_v2.Network, filters=filters,
            query_field=models_v2.Network.id.key)

    @db_api.retry_if_session_inactive()
    def create_subnet_bulk(self, context, subnets):
        return self._create_bulk('subnet', context, subnets)

    def _validate_ip_version(self, ip_version, addr, name):
        """Check IP field of a subnet match specified ip version."""
        ip = netaddr.IPNetwork(addr)
        if ip.version != ip_version:
            data = {'name': name,
                    'addr': addr,
                    'ip_version': ip_version}
            msg = _("%(name)s '%(addr)s' does not match "
                    "the ip_version '%(ip_version)s'") % data
            raise exc.InvalidInput(error_message=msg)

    def _validate_subnet(self, context, s, cur_subnet=None, is_pd=False):
        """Validate a subnet spec."""

        # This method will validate attributes which may change during
        # create_subnet() and update_subnet().
        # The method requires the subnet spec 's' has 'ip_version' field.
        # If 's' dict does not have 'ip_version' field in an API call
        # (e.g., update_subnet()), you need to set 'ip_version' field
        # before calling this method.

        ip_ver = s['ip_version']

        # We could be called without a cidr if a subnet pool is being used,
        # so remember that since some checks below require one and should
        # be skipped.
        has_cidr = False
        if validators.is_attr_set(s.get('cidr')):
            self._validate_ip_version(ip_ver, s['cidr'], 'cidr')
            net = netaddr.IPNetwork(s['cidr'])
            has_cidr = True

        # TODO(watanabe.isao): After we found a way to avoid the re-sync
        # from the agent side, this restriction could be removed.
        if cur_subnet:
            dhcp_was_enabled = cur_subnet.enable_dhcp
        else:
            dhcp_was_enabled = False
        # A subnet cidr of '::' is invalid, unless the caller has
        # indicated they are doing Prefix Delegation,
        # see https://bugs.launchpad.net/neutron/+bug/2028159
        if (has_cidr and ip_ver == constants.IP_VERSION_6 and
                net.network == netaddr.IPAddress('::') and not
                is_pd):
            error_message = _("IPv6 subnet '::' is not supported")
            raise exc.InvalidInput(error_message=error_message)
        if has_cidr and s.get('enable_dhcp') and not dhcp_was_enabled:
            error_message = _("Subnet has a prefix length that is "
                              "incompatible with DHCP service enabled")
            if ((ip_ver == 4 and net.prefixlen > 30) or
                    (ip_ver == 6 and net.prefixlen > 126)):
                raise exc.InvalidInput(error_message=error_message)

            if net.is_multicast():
                error_message = _("Multicast IP subnet is not supported "
                                  "if enable_dhcp is True")
                raise exc.InvalidInput(error_message=error_message)
            if net.is_loopback():
                error_message = _("Loopback IP subnet is not supported "
                                  "if enable_dhcp is True")
                raise exc.InvalidInput(error_message=error_message)
            if ip_ver == constants.IP_VERSION_4 and net.first == 0:
                error_message = _("First IP '0.0.0.0' of network is not "
                                  "supported if enable_dhcp is True.")
                raise exc.InvalidInput(error_message=error_message)

        gateway_ip = s.get('gateway_ip', constants.ATTR_NOT_SPECIFIED)
        if validators.is_attr_set(gateway_ip) or gateway_ip is None:
            # Validate the gateway IP, if defined in the request.
            if s['gateway_ip']:
                self._validate_ip_version(ip_ver, gateway_ip, 'gateway_ip')
                if has_cidr:
                    is_gateway_not_valid = (
                        ipam.utils.check_gateway_invalid_in_subnet(
                            s['cidr'], gateway_ip))
                    if is_gateway_not_valid:
                        error_message = _("Gateway is not valid on subnet")
                        raise exc.InvalidInput(error_message=error_message)

            # Ensure the current subnet gateway IP is not assigned to any port.
            # The subnet gateway IP cannot be modified or removed if in use
            # (assigned to a router interface).
            # Skip this check in case of create (s parameter won't have id).
            # NOTE(salv-orlando): There is slight chance of a race, when
            # a subnet-update and a router-interface-add operation are
            # executed concurrently
            s_gateway_ip = (netaddr.IPAddress(gateway_ip) if gateway_ip else
                            None)
            if (cur_subnet and
                    s_gateway_ip != cur_subnet['gateway_ip'] and
                    not ipv6_utils.is_ipv6_pd_enabled(s)):
                current_gateway_ip = str(cur_subnet['gateway_ip'])
                alloc = port_obj.IPAllocation.get_alloc_routerports(
                    context, cur_subnet['id'], gateway_ip=current_gateway_ip,
                    first=True)

                if alloc and alloc.port_id:
                    raise exc.GatewayIpInUse(
                        ip_address=current_gateway_ip,
                        port_id=alloc.port_id)

        if validators.is_attr_set(s.get('dns_nameservers')):
            if len(s['dns_nameservers']) > cfg.CONF.max_dns_nameservers:
                raise exc.DNSNameServersExhausted(
                    subnet_id=s.get('id', _('new subnet')),
                    quota=cfg.CONF.max_dns_nameservers)
            for dns in s['dns_nameservers']:
                try:
                    netaddr.IPAddress(dns)
                except Exception:
                    raise exc.InvalidInput(
                        error_message=(_("Error parsing dns address %s") %
                                       dns))
                self._validate_ip_version(ip_ver, dns, 'dns_nameserver')

        if validators.is_attr_set(s.get('host_routes')):
            if len(s['host_routes']) > cfg.CONF.max_subnet_host_routes:
                raise exc.HostRoutesExhausted(
                    subnet_id=s.get('id', _('new subnet')),
                    quota=cfg.CONF.max_subnet_host_routes)
            # check if the routes are all valid
            for rt in s['host_routes']:
                self._validate_host_route(rt, ip_ver)

        if ip_ver == 4:
            if validators.is_attr_set(s.get('ipv6_ra_mode')):
                raise exc.InvalidInput(
                    error_message=(_("ipv6_ra_mode is not valid when "
                                     "ip_version is 4")))
            if validators.is_attr_set(s.get('ipv6_address_mode')):
                raise exc.InvalidInput(
                    error_message=(_("ipv6_address_mode is not valid when "
                                     "ip_version is 4")))
        if ip_ver == 6:
            self._validate_ipv6_attributes(s, cur_subnet, has_cidr)

    def _validate_subnet_for_pd(self, subnet):
        """Validates that subnet parameters are correct for IPv6 PD"""
        if (subnet.get('ip_version') != constants.IP_VERSION_6):
            reason = _("Prefix Delegation can only be used with IPv6 "
                       "subnets.")
            raise exc.BadRequest(resource='subnets', msg=reason)

        mode_list = [constants.IPV6_SLAAC,
                     constants.DHCPV6_STATELESS]

        ra_mode = subnet.get('ipv6_ra_mode')
        if ra_mode not in mode_list:
            reason = _("IPv6 RA Mode must be SLAAC or Stateless for "
                       "Prefix Delegation.")
            raise exc.BadRequest(resource='subnets', msg=reason)

        address_mode = subnet.get('ipv6_address_mode')
        if address_mode not in mode_list:
            reason = _("IPv6 Address Mode must be SLAAC or Stateless for "
                       "Prefix Delegation.")
            raise exc.BadRequest(resource='subnets', msg=reason)

    def _validate_subnet_network_mtu(self, network, subnet):
        """Validates that network mtu is correct for subnet association"""
        mtu = network.mtu
        if not mtu or mtu >= constants.IPV6_MIN_MTU:
            return

        # if below IPv4 minimum we fail early
        if mtu < constants.IPV4_MIN_MTU:
            raise exc.NetworkMTUSubnetConflict(
                net_id=network.id, mtu=constants.IPV4_MIN_MTU)

        # We do not need to check IPv4 subnets as they will have been
        # caught by above IPV4_MIN_MTU check
        ip_version = subnet.get('ip_version')
        if (ip_version == constants.IP_VERSION_6 and
                mtu < constants.IPV6_MIN_MTU):
            raise exc.NetworkMTUSubnetConflict(
                net_id=network.id, mtu=constants.IPV6_MIN_MTU)

    def _update_router_gw_ports(self, context, network, subnet):
        l3plugin = directory.get_plugin(plugin_constants.L3)
        # The hasattr check for customized l3 plugins that may have no such
        # function.
        if l3plugin and hasattr(l3plugin, "update_router_gw_ports"):
            l3plugin.update_router_gw_ports(context, network, subnet)

    @db_api.retry_if_session_inactive()
    def _create_subnet_postcommit(self, context, result,
                                  network=None, ipam_subnet=None):
        # need to get db net obj with full subnet info either if no network
        # is passed or if passed network is an external net dict from
        # ml2 plugin (with only IDs in 'subnets')
        if not network or network.get(extnet_def.EXTERNAL):
            network = self._get_network(context,
                                        result['network_id'])

        if hasattr(network, 'external') and network.external:
            self._update_router_gw_ports(context,
                                         network,
                                         result)
        # If this subnet supports auto-addressing, then update any
        # internal ports on the network with addresses for this subnet.
        if ipv6_utils.is_auto_address_subnet(result):
            if not ipam_subnet:
                ipam_subnet = self.ipam.get_subnet(context, result['id'])
            updated_ports = self.ipam.add_auto_addrs_on_network_ports(
                context, result, ipam_subnet)
            for port_id in updated_ports:
                port_info = {'port': {'id': port_id}}
                try:
                    self.update_port(context, port_id, port_info)
                except exc.PortNotFound:
                    LOG.debug("Port %(p)s concurrently deleted while adding "
                              "address for new subnet %(s)s.", {'p': port_id,
                                                                's': result})

    def _get_subnetpool_id(self, context, subnet):
        """Return the subnetpool id for this request

        :param subnet: The subnet dict from the request
        """
        use_default_subnetpool = subnet.get('use_default_subnetpool')
        if use_default_subnetpool == constants.ATTR_NOT_SPECIFIED:
            use_default_subnetpool = False
        subnetpool_id = subnet.get('subnetpool_id')
        if subnetpool_id == constants.ATTR_NOT_SPECIFIED:
            subnetpool_id = None

        if use_default_subnetpool and subnetpool_id:
            msg = _('subnetpool_id and use_default_subnetpool cannot both be '
                    'specified')
            raise exc.BadRequest(resource='subnets', msg=msg)

        if subnetpool_id:
            return subnetpool_id

        if not use_default_subnetpool:
            return

        cidr = subnet.get('cidr')
        if validators.is_attr_set(cidr):
            ip_version = netaddr.IPNetwork(cidr).version
        else:
            ip_version = subnet.get('ip_version')
            if not validators.is_attr_set(ip_version):
                msg = _('ip_version must be specified in the absence of '
                        'cidr and subnetpool_id')
                raise exc.BadRequest(resource='subnets', msg=msg)

        if ip_version == 6 and cfg.CONF.ipv6_pd_enabled:
            return constants.IPV6_PD_POOL_ID

        subnetpool = self.get_default_subnetpool(context, ip_version)
        if subnetpool:
            return subnetpool['id']

        msg = _('No default subnetpool found for IPv%s') % ip_version
        raise exc.BadRequest(resource='subnets', msg=msg)

    @db_api.retry_if_session_inactive()
    def create_subnet(self, context, subnet):
        result, net, ipam_sub = self._create_subnet_precommit(context, subnet)
        self._create_subnet_postcommit(context, result, net, ipam_sub)
        return result

    def _create_subnet_precommit(self, context, subnet):
        """Creates subnet in DB, returns result, network, and ipam_subnet."""
        s = subnet['subnet']
        cidr = s.get('cidr', constants.ATTR_NOT_SPECIFIED)
        prefixlen = s.get('prefixlen', constants.ATTR_NOT_SPECIFIED)
        has_cidr = validators.is_attr_set(cidr)
        has_prefixlen = validators.is_attr_set(prefixlen)

        if has_cidr and has_prefixlen:
            msg = _('cidr and prefixlen must not be supplied together')
            raise exc.BadRequest(resource='subnets', msg=msg)

        if has_cidr:
            # turn the CIDR into a proper subnet
            net = netaddr.IPNetwork(s['cidr'])
            subnet['subnet']['cidr'] = '{}/{}'.format(
                net.network, net.prefixlen)

        subnetpool_id = self._get_subnetpool_id(context, s)
        if not subnetpool_id and not has_cidr:
            msg = _('a subnetpool must be specified in the absence of a cidr')
            raise exc.BadRequest(resource='subnets', msg=msg)

        validate = True
        is_pd = False
        if subnetpool_id:
            self.ipam.validate_pools_with_subnetpool(s)
            if subnetpool_id == constants.IPV6_PD_POOL_ID:
                is_pd = True
                if has_cidr:
                    # We do not currently support requesting a specific
                    # cidr with IPv6 prefix delegation. Set the subnetpool_id
                    # to None and allow the request to continue as normal.
                    subnetpool_id = None
                else:
                    prefix = constants.PROVISIONAL_IPV6_PD_PREFIX
                    subnet['subnet']['cidr'] = prefix
                    self._validate_subnet_for_pd(s)
                    validate = False
        else:
            if not has_cidr:
                msg = _('A cidr must be specified in the absence of a '
                        'subnet pool')
                raise exc.BadRequest(resource='subnets', msg=msg)

        if validate:
            self._validate_subnet(context, s, is_pd=is_pd)

        with db_api.CONTEXT_WRITER.using(context):
            network = self._get_network(context,
                                        subnet['subnet']['network_id'])
            self._validate_subnet_network_mtu(network, s)
            subnet, ipam_subnet = self.ipam.allocate_subnet(context,
                                                            network,
                                                            subnet['subnet'],
                                                            subnetpool_id)
            # TODO(ihrachys): make sqlalchemy refresh expired relationships
            getattr(network, 'subnets')
        result = self._make_subnet_dict(subnet, context=context)
        return result, network, ipam_subnet

    def _update_allocation_pools(self, subnet):
        """Gets new allocation pools and formats them correctly"""
        allocation_pools = self.ipam.generate_pools(subnet['cidr'],
                                                    subnet['gateway_ip'])
        return [{'start': str(netaddr.IPAddress(p.first,
                                                subnet['ip_version'])),
                 'end': str(netaddr.IPAddress(p.last, subnet['ip_version']))}
                for p in allocation_pools]

    @db_api.retry_if_session_inactive()
    def update_subnet(self, context, id, subnet):
        """Update the subnet with new info.

        The change however will not be realized until the client renew the
        dns lease or we support gratuitous DHCP offers
        """
        result, orig = self._update_subnet_precommit(context, id, subnet)
        return self._update_subnet_postcommit(context, orig, result)

    def _update_subnet_precommit(self, context, id, subnet):
        """All subnet update operations safe to enclose in a transaction.

        :param context: neutron api request context
        :param id: subnet id
        :param subnet: API request dictionary
        """
        s = subnet['subnet']
        new_cidr = s.get('cidr')
        subnet_obj = self._get_subnet_object(context, id)
        orig = self._make_subnet_dict(subnet_obj, fields=None, context=context)
        # Fill 'ip_version' and 'allocation_pools' fields with the current
        # value since _validate_subnet() expects subnet spec has 'ip_version'
        # and 'allocation_pools' fields.
        s['ip_version'] = subnet_obj.ip_version
        s['cidr'] = subnet_obj.cidr
        s['id'] = subnet_obj.id
        s['project_id'] = subnet_obj.project_id
        s['tenant_id'] = subnet_obj.project_id
        s['subnetpool_id'] = subnet_obj.subnetpool_id
        # Fill 'network_id' field with the current value since this is expected
        # by _validate_segment() in ipam_pluggable_backend.
        s['network_id'] = subnet_obj.network_id
        is_pd = s['subnetpool_id'] == constants.IPV6_PD_POOL_ID
        self._validate_subnet(context, s, cur_subnet=subnet_obj, is_pd=is_pd)
        db_pools = [netaddr.IPRange(p.start, p.end)
                    for p in subnet_obj.allocation_pools]

        if new_cidr and ipv6_utils.is_ipv6_pd_enabled(s):
            # This is an ipv6 prefix delegation-enabled subnet being given an
            # updated cidr by the plugin.
            s['cidr'] = netaddr.IPNetwork(new_cidr, s['ip_version'])
            # Update gateway_ip and allocation pools based on new cidr
            s['gateway_ip'] = utils.get_first_host_ip(
                s['cidr'], s['ip_version'])
            s['allocation_pools'] = self._update_allocation_pools(s)

        range_pools = None
        if s.get('allocation_pools') is not None:
            # Convert allocation pools to IPRange to simplify future checks
            range_pools = self.ipam.pools_to_ip_range(s['allocation_pools'])
            self.ipam.validate_allocation_pools(range_pools, s['cidr'])
            s['allocation_pools'] = range_pools

        # If either gateway_ip or allocation_pools were specified
        subnet_gateway = (subnet_obj.gateway_ip
                          if subnet_obj.gateway_ip else None)
        gateway_ip = s.get('gateway_ip', subnet_gateway)
        gateway_ip_changed = gateway_ip != subnet_gateway
        if gateway_ip_changed or s.get('allocation_pools') is not None:
            pools = range_pools if range_pools is not None else db_pools
            if gateway_ip:
                self.ipam.validate_gw_out_of_pools(gateway_ip, pools)

        registry.publish(
            resources.SUBNET, events.BEFORE_UPDATE, self,
            payload=events.DBEventPayload(
                context,
                resource_id=id,
                states=(orig, s,)))

        with db_api.CONTEXT_WRITER.using(context):
            subnet, changes = self.ipam.update_db_subnet(
                context, id, s, db_pools, subnet_obj=subnet_obj)
        return self._make_subnet_dict(subnet, context=context), orig

    @property
    def l3_rpc_notifier(self):
        if not hasattr(self, '_l3_rpc_notifier'):
            self._l3_rpc_notifier = l3_rpc_agent_api.L3AgentNotifyAPI()
        return self._l3_rpc_notifier

    @l3_rpc_notifier.setter
    def l3_rpc_notifier(self, value):
        self._l3_rpc_notifier = value

    def _update_subnet_postcommit(self, context, orig, result):
        """Subnet update operations that happen after transaction completes.

        :param context: neutron api request context
        :param orig: subnet dictionary representing state before update
        :param result: subnet dictionary representing state after update
        """
        update_ports_needed = (result['cidr'] != orig['cidr'] and
                               ipv6_utils.is_ipv6_pd_enabled(result))
        if update_ports_needed:
            # Find ports that have not yet been updated
            # with an IP address by Prefix Delegation, and update them
            filters = {'fixed_ips': {'subnet_id': [result['id']]}}
            ports = self.get_ports(context, filters=filters)
            routers = []
            for port in ports:
                for ip in port['fixed_ips']:
                    if ip['subnet_id'] == result['id']:
                        if (port['device_owner'] in
                                constants.ROUTER_INTERFACE_OWNERS):
                            routers.append(port['device_id'])
                            ip['ip_address'] = result['gateway_ip']
                        else:
                            # We remove ip_address and pass only PD subnet_id
                            # in port's fixed_ip for port_update. Later, IPAM
                            # drivers will allocate eui64 address with new
                            # prefix when they find PD subnet_id in port's
                            # fixed_ip.
                            ip.pop('ip_address', None)
                self.update_port(context, port['id'], {'port': port})
            # Send router_update to l3_agent
            if routers:
                self.l3_rpc_notifier.routers_updated(context, routers)

        registry.publish(
            resources.SUBNET, events.AFTER_UPDATE, self,
            payload=events.DBEventPayload(
                context,
                resource_id=result['id'],
                states=(orig, result,)))

        return result

    def _subnet_get_user_allocation(self, context, subnet_id):
        """Check if there are any user ports on subnet and return first."""
        return port_obj.IPAllocation.get_alloc_by_subnet_id(
            context, subnet_id, _constants.AUTO_DELETE_PORT_OWNERS)

    def _subnet_check_ip_allocations_internal_router_ports(self, context,
                                                           subnet_id):
        # Do not delete the subnet if IP allocations for internal
        # router ports still exist
        allocs = port_obj.IPAllocation.get_alloc_by_subnet_id(
            context, subnet_id, constants.ROUTER_INTERFACE_OWNERS, False)
        if allocs:
            LOG.debug("Subnet %s still has internal router ports, "
                      "cannot delete", subnet_id)
            raise exc.SubnetInUse(subnet_id=subnet_id)

    def _ensure_no_user_ports_on_subnet(self, context, id):
        alloc = self._subnet_get_user_allocation(context, id)
        if alloc:
            LOG.info("Found port (%(port_id)s, %(ip)s) having IP "
                     "allocation on subnet "
                     "%(subnet)s, cannot delete",
                     {'ip': alloc.ip_address,
                      'port_id': alloc.port_id,
                      'subnet': id})
            raise exc.SubnetInUse(subnet_id=id)

    def _remove_subnet_ip_allocations_from_ports(self, context, subnet):
        # Do not allow a subnet to be deleted if a router is attached to it
        sid = subnet['id']
        self._subnet_check_ip_allocations_internal_router_ports(
            context, sid)
        is_auto_addr_subnet = ipv6_utils.is_auto_address_subnet(subnet)
        if not is_auto_addr_subnet:
            # we only automatically remove IP addresses from user ports if
            # the IPs come from auto allocation subnets.
            self._ensure_no_user_ports_on_subnet(context, sid)

        port_obj.IPAllocation.delete_alloc_by_subnet_id(context, sid)

    @db_api.retry_if_session_inactive()
    def delete_subnet(self, context, id):
        LOG.debug("Deleting subnet %s", id)
        with db_api.CONTEXT_WRITER.using(context):
            _ensure_subnet_not_used(context, id)
            subnet = self._get_subnet_object(context, id)
            registry.publish(
                resources.SUBNET, events.PRECOMMIT_DELETE_ASSOCIATIONS, self,
                payload=events.DBEventPayload(context, resource_id=subnet.id))
            self._remove_subnet_ip_allocations_from_ports(context, subnet)
            self._delete_subnet(context, subnet)
        registry.publish(
            resources.SUBNET, events.AFTER_DELETE, self,
            payload=events.DBEventPayload(
                context,
                resource_id=id,
                states=(subnet.to_dict(),)))

    def _delete_subnet(self, context, subnet):
        with db_api.exc_to_retry(sql_exc.IntegrityError), \
                db_api.CONTEXT_WRITER.using(context):
            registry.publish(
                resources.SUBNET, events.PRECOMMIT_DELETE, self,
                payload=events.DBEventPayload(context,
                                              resource_id=subnet.id,
                                              states=(subnet,)))
            subnet.delete()
            # Delete related ipam subnet manually,
            # since there is no FK relationship
            self.ipam.delete_subnet(context, subnet.id)

    @db_api.retry_if_session_inactive()
    def get_subnet(self, context, id, fields=None):
        subnet_obj = self._get_subnet_object(context, id)
        return self._make_subnet_dict(subnet_obj, fields, context=context)

    @db_api.retry_if_session_inactive()
    def get_subnets(self, context, filters=None, fields=None,
                    sorts=None, limit=None, marker=None,
                    page_reverse=False):
        subnet_objs = self._get_subnets(context, filters, sorts, limit,
                                        marker, page_reverse)
        return [
            self._make_subnet_dict(subnet_object, fields, context)
            for subnet_object in subnet_objs
        ]

    @db_api.retry_if_session_inactive()
    def get_subnets_count(self, context, filters=None):
        filters = filters or {}
        return subnet_obj.Subnet.count(context, validate_filters=False,
                                       **filters)

    @db_api.retry_if_session_inactive()
    def get_subnets_by_network(self, context, network_id):
        return [self._make_subnet_dict(subnet_obj) for subnet_obj in
                self._get_subnets_by_network(context, network_id)]

    def _validate_address_scope_id(self, context, address_scope_id,
                                   subnetpool_id, sp_prefixes, ip_version):
        """Validate the address scope before associating.

        Subnetpool can associate with an address scope if
          - the tenant user is the owner of both the subnetpool and
            address scope
          - the user is associating the subnetpool with a shared
            address scope
          - there is no prefix conflict with the existing subnetpools
            associated with the address scope.
          - the address family of the subnetpool and address scope
            are the same
        """
        if not validators.is_attr_set(address_scope_id):
            return

        address_scope = self._get_address_scope(context, address_scope_id)
        is_accessible = (
            address_scope_obj.AddressScope.is_accessible(
                context, address_scope
            )
        )

        if not is_accessible:
            raise exc.IllegalSubnetPoolAssociationToAddressScope(
                subnetpool_id=subnetpool_id, address_scope_id=address_scope_id)

        as_ip_version = self.get_ip_version_for_address_scope(context,
                                                              address_scope_id)

        if ip_version != as_ip_version:
            raise exc.IllegalSubnetPoolIpVersionAssociationToAddressScope(
                subnetpool_id=subnetpool_id, address_scope_id=address_scope_id,
                ip_version=as_ip_version)

        self._check_subnetpool_address_scope_network_affinity(
            context, subnetpool_id, ip_version)

        subnetpools = subnetpool_obj.SubnetPool.get_objects(
            context, address_scope_id=address_scope_id)

        new_set = netaddr.IPSet(sp_prefixes)
        for sp in subnetpools:
            if sp.id == subnetpool_id:
                continue
            sp_set = netaddr.IPSet(sp.prefixes)
            if sp_set.intersection(new_set):
                raise exc.AddressScopePrefixConflict()

    def _check_subnetpool_address_scope_network_affinity(self, context,
                                                         subnetpool_id,
                                                         ip_version):
        """Check whether updating a subnet pool's address scope is allowed.

        - Identify the subnets that would be re-scoped
        - Identify the networks that would be affected by re-scoping
        - Find all subnets associated with the affected networks
        - Perform set difference (all - to_be_rescoped)
        - If the set difference yields non-zero result size, re-scoping the
        subnet pool will leave subnets in different address scopes and result
        in address scope / network affinity violations so raise an exception to
        block the operation.
        """

        # TODO(tidwellr) potentially lots of subnets here, optimize this code
        subnets_to_rescope = self._get_subnets_by_subnetpool(context,
                                                             subnetpool_id)
        rescoped_subnet_ids = set()
        affected_source_network_ids = set()
        for subnet in subnets_to_rescope:
            rescoped_subnet_ids.add(subnet.id)
            affected_source_network_ids.add(subnet.network_id)

        all_network_subnets = subnet_obj.Subnet.get_objects(
            context,
            network_id=affected_source_network_ids,
            ip_version=ip_version)
        all_affected_subnet_ids = {
            subnet.id for subnet in all_network_subnets}

        # Use set difference to identify the subnets that would be
        # violating address scope affinity constraints if the subnet
        # pool's address scope was changed.
        violations = all_affected_subnet_ids.difference(rescoped_subnet_ids)
        if violations:
            raise addr_scope_exc.NetworkAddressScopeAffinityError()

    def _check_subnetpool_update_allowed(self, context, subnetpool_id,
                                         address_scope_id):
        """Check if the subnetpool can be updated or not.

        If the subnetpool is associated to a shared address scope not owned
        by the tenant, then the subnetpool cannot be updated.
        """

        if not self.is_address_scope_owned_by_tenant(context,
                                                     address_scope_id):
            msg = _("subnetpool %(subnetpool_id)s cannot be updated when"
                    " associated with shared address scope "
                    "%(address_scope_id)s") % {
                        'subnetpool_id': subnetpool_id,
                        'address_scope_id': address_scope_id}
            raise exc.IllegalSubnetPoolUpdate(reason=msg)

    def _check_default_subnetpool_exists(self, context, ip_version):
        """Check if a default already exists for the given IP version.

        There can only be one default subnetpool for each IP family. Raise an
        InvalidInput error if a default has already been set.
        """
        if self.get_default_subnetpool(context, ip_version):
            msg = _("A default subnetpool for this IP family has already "
                    "been set. Only one default may exist per IP family")
            raise exc.InvalidInput(error_message=msg)

    @db_api.retry_if_session_inactive()
    def create_subnetpool(self, context, subnetpool):
        sp = subnetpool['subnetpool']
        sp_reader = subnet_alloc.SubnetPoolReader(sp)
        if sp_reader.is_default:
            self._check_default_subnetpool_exists(context,
                                                  sp_reader.ip_version)
        self._validate_address_scope_id(context, sp_reader.address_scope_id,
                                        sp_reader.id, sp_reader.prefixes,
                                        sp_reader.ip_version)
        pool_args = {'project_id': sp['tenant_id'],
                     'id': sp_reader.id,
                     'name': sp_reader.name,
                     'ip_version': sp_reader.ip_version,
                     'default_prefixlen':
                     sp_reader.default_prefixlen,
                     'min_prefixlen': sp_reader.min_prefixlen,
                     'max_prefixlen': sp_reader.max_prefixlen,
                     'is_default': sp_reader.is_default,
                     'shared': sp_reader.shared,
                     'default_quota': sp_reader.default_quota,
                     'address_scope_id': sp_reader.address_scope_id,
                     'description': sp_reader.description,
                     'prefixes': sp_reader.prefixes}
        subnetpool = subnetpool_obj.SubnetPool(context, **pool_args)
        subnetpool.create()

        return self._make_subnetpool_dict(subnetpool)

    @db_api.retry_if_session_inactive()
    def update_subnetpool(self, context, id, subnetpool):
        new_sp = subnetpool['subnetpool']

        with db_api.CONTEXT_WRITER.using(context):
            orig_sp = self._get_subnetpool(context, id=id)
            updated = _update_subnetpool_dict(orig_sp, new_sp)
            reader = subnet_alloc.SubnetPoolReader(updated)
            if reader.is_default and not orig_sp.is_default:
                self._check_default_subnetpool_exists(context,
                                                      reader.ip_version)
            if orig_sp.address_scope_id:
                self._check_subnetpool_update_allowed(context, id,
                                                      orig_sp.address_scope_id)

            self._validate_address_scope_id(context, reader.address_scope_id,
                                            id, reader.prefixes,
                                            reader.ip_version)
            address_scope_changed = (
                orig_sp.address_scope_id != reader.address_scope_id)

            orig_sp.update_fields(reader.subnetpool)
            orig_sp.update()

        if address_scope_changed:
            # Notify about the update of subnetpool's address scope
            registry.publish(resources.SUBNETPOOL_ADDRESS_SCOPE,
                             events.AFTER_UPDATE,
                             self.update_subnetpool,
                             payload=events.DBEventPayload(
                                 context, resource_id=id))

        for key in ['min_prefixlen', 'max_prefixlen', 'default_prefixlen']:
            updated['key'] = str(updated[key])
        resource_extend.apply_funcs(subnetpool_def.COLLECTION_NAME,
                                    updated, orig_sp.db_obj)
        return updated

    @db_api.retry_if_session_inactive()
    def get_subnetpool(self, context, id, fields=None):
        subnetpool = self._get_subnetpool(context, id)
        return self._make_subnetpool_dict(subnetpool, fields)

    @db_api.retry_if_session_inactive()
    def get_subnetpools(self, context, filters=None, fields=None,
                        sorts=None, limit=None, marker=None,
                        page_reverse=False):
        pager = base_obj.Pager(sorts, limit, page_reverse, marker)
        filters = filters or {}
        subnetpools = subnetpool_obj.SubnetPool.get_objects(
            context, _pager=pager, validate_filters=False, **filters)
        return [
            self._make_subnetpool_dict(pool, fields)
            for pool in subnetpools
        ]

    @db_api.retry_if_session_inactive()
    def get_default_subnetpool(self, context, ip_version):
        """Retrieve the default subnetpool for the given IP version."""
        filters = {'is_default': True,
                   'ip_version': ip_version}
        subnetpool = self.get_subnetpools(context, filters=filters)
        if subnetpool:
            return subnetpool[0]

    @db_api.retry_if_session_inactive()
    def delete_subnetpool(self, context, id):
        with db_api.CONTEXT_WRITER.using(context):
            subnetpool = self._get_subnetpool(context, id=id)
            if subnet_obj.Subnet.objects_exist(context, subnetpool_id=id):
                reason = _("Subnet pool has existing allocations")
                raise exc.SubnetPoolDeleteError(reason=reason)
            subnetpool.delete()

    @db_api.retry_if_session_inactive()
    def onboard_network_subnets(self, context, subnetpool_id, network_info):
        network_id = network_info.get('network_id')
        if not validators.is_attr_set(network_id):
            msg = _("network_id must be specified.")
            raise exc.InvalidInput(error_message=msg)
        if not self._network_exists(context, network_id):
            raise exc.NetworkNotFound(net_id=network_id)

        subnetpool = subnetpool_obj.SubnetPool.get_object(context,
                                                          id=subnetpool_id)
        if not subnetpool:
            raise exc.SubnetPoolNotFound(subnetpool_id=id)

        subnets_to_onboard = subnet_obj.Subnet.get_objects(
            context,
            network_id=network_id,
            ip_version=subnetpool.ip_version)

        self._onboard_network_subnets(context, subnets_to_onboard, subnetpool)

        if subnetpool.address_scope_id:
            # Notify all affected routers of any address scope changes
            registry.publish(resources.SUBNETPOOL_ADDRESS_SCOPE,
                             events.AFTER_UPDATE,
                             self.onboard_network_subnets,
                             payload=events.DBEventPayload(
                                 context, resource_id=subnetpool_id))

        onboard_info = []
        for subnet in subnets_to_onboard:
            onboard_info.append({'id': subnet.id, 'cidr': subnet.cidr})

        return onboard_info

    def _onboard_network_subnets(self, context, subnets_to_onboard,
                                 subnetpool):
        allocated_prefix_set = netaddr.IPSet(
            [x.cidr for x in subnet_obj.Subnet.get_objects(
                context,
                subnetpool_id=subnetpool.id)])
        prefixes_to_add = []

        for subnet in subnets_to_onboard:
            to_onboard_ipset = netaddr.IPSet([subnet.cidr])
            if to_onboard_ipset & allocated_prefix_set:
                args = {'subnet_id': subnet.id,
                        'cidr': subnet.cidr,
                        'subnetpool_id': subnetpool.id}
                msg = _('Onboarding subnet %(subnet_id)s: %(cidr)s conflicts '
                        'with allocated prefixes in subnet pool '
                        '%(subnetpool_id)s') % args
                raise exc.IllegalSubnetPoolUpdate(reason=msg)
            prefixes_to_add.append(subnet.cidr)

        with db_api.CONTEXT_WRITER.using(context):
            new_sp_prefixes = subnetpool.prefixes + prefixes_to_add
            sp_update_req = {'subnetpool': {'prefixes': new_sp_prefixes}}

            self.update_subnetpool(context, subnetpool.id, sp_update_req)
            for subnet in subnets_to_onboard:
                subnet.subnetpool_id = subnetpool.id
                subnet.update()

    def _check_mac_addr_update(self, context, port, new_mac, device_owner):
        if (device_owner and
                device_owner.startswith(
                    constants.DEVICE_OWNER_NETWORK_PREFIX)):
            raise exc.UnsupportedPortDeviceOwner(
                op=_("mac address update"), port_id=id,
                device_owner=device_owner)

    def _create_db_port_obj(self, context, port_data):
        mac_address = port_data.pop('mac_address', None)
        if mac_address:
            if self._is_mac_in_use(context, port_data['network_id'],
                                   mac_address):
                raise exc.MacAddressInUse(net_id=port_data['network_id'],
                                          mac=mac_address)
        else:
            mac_address = self._generate_macs()[0]
        db_port = models_v2.Port(mac_address=mac_address, **port_data)
        context.session.add(db_port)
        return db_port

    @db_api.retry_if_session_inactive()
    def create_port(self, context, port):
        db_port = self.create_port_db(context, port)
        return self._make_port_dict(db_port, process_extensions=False)

    @db_api.retry_if_session_inactive()
    def create_port_bulk(self, context, ports):
        return self._create_bulk('port', context, ports)

    def create_port_db(self, context, port):
        p = port['port']
        port_id = p.get('id') or uuidutils.generate_uuid()
        network_id = p['network_id']
        # TODO(ralonsoh): "tenant_id" reference should be removed.
        project_id = p.get('project_id') or p['tenant_id']
        if p.get('device_owner'):
            self._enforce_device_owner_not_router_intf_or_device_id(
                context, p.get('device_owner'), p.get('device_id'),
                project_id)

        port_data = dict(tenant_id=project_id,
                         name=p['name'],
                         id=port_id,
                         network_id=network_id,
                         admin_state_up=p['admin_state_up'],
                         status=p.get('status', constants.PORT_STATUS_ACTIVE),
                         device_id=p['device_id'],
                         device_owner=p['device_owner'],
                         description=p.get('description'))
        if p.get('mac_address') is not constants.ATTR_NOT_SPECIFIED:
            port_data['mac_address'] = p.get('mac_address')
        with db_api.CONTEXT_WRITER.using(context):
            # Ensure that the network exists.
            if not self._network_exists(context, network_id):
                raise exc.NetworkNotFound(net_id=network_id)

            # Create the port
            db_port = self._create_db_port_obj(context, port_data)
            p['mac_address'] = db_port.mac_address

            try:
                self.ipam.allocate_ips_for_port_and_store(
                    context, port, port_id)
                db_port.ip_allocation = (ipalloc_apidef.
                                         IP_ALLOCATION_IMMEDIATE)
            except ipam_exc.DeferIpam:
                db_port.ip_allocation = (ipalloc_apidef.
                                         IP_ALLOCATION_DEFERRED)
            fixed_ips = p['fixed_ips']
            if validators.is_attr_set(fixed_ips) and not fixed_ips:
                # [] was passed explicitly as fixed_ips. An unaddressed port.
                db_port.ip_allocation = ipalloc_apidef.IP_ALLOCATION_NONE

        return db_port

    def _validate_port_for_update(self, context, db_port, new_port, new_mac):
        changed_owner = 'device_owner' in new_port
        current_owner = (new_port.get('device_owner') or
                         db_port['device_owner'])
        changed_device_id = new_port.get('device_id') != db_port['device_id']
        current_device_id = new_port.get('device_id') or db_port['device_id']

        if current_owner and changed_device_id or changed_owner:
            self._enforce_device_owner_not_router_intf_or_device_id(
                context, current_owner, current_device_id,
                db_port['tenant_id'])

        if (new_mac and
                new_mac != converters.convert_to_sanitized_mac_address(
                    db_port['mac_address'])):
            self._check_mac_addr_update(context, db_port,
                                        new_mac, current_owner)

    @db_api.retry_if_session_inactive()
    def update_port(self, context, id, port, db_port=None):
        # we dont't use DB objects not belonging to the current active session
        db_port = (db_port if db_api.is_session_active(context.session)
                   else None)
        new_port = port['port']

        with db_api.CONTEXT_WRITER.using(context):
            db_port = db_port or self._get_port(context, id)
            new_mac = new_port.get('mac_address')
            self._validate_port_for_update(context, db_port, new_port, new_mac)
            # Note: _make_port_dict is called here to load extension data
            # (specifically host binding).  The IPAM plugin is separate from
            # the core plugin, so extensions are not loaded.
            #
            # The IPAM code could cheat and get it directly from db_port but it
            # would have to know about the implementation (remember ml2 has its
            # own port binding schema that differs from the generic one)
            #
            # This code could extract just the port binding host here and pass
            # that in.  The problem is that db_base_plugin_common shouldn't
            # know anything about port binding.  This compromise sends IPAM a
            # port_dict with all of the extension data loaded.
            try:
                self.ipam.update_port(
                    context,
                    old_port_db=db_port,
                    old_port=self._make_port_dict(db_port),
                    new_port=new_port)
            except ipam_exc.IPAddressChangeNotAllowed as e:
                raise exc.BadRequest(resource='ports', msg=e)
        return self._make_port_dict(db_port)

    @db_api.retry_if_session_inactive()
    def delete_port(self, context, id, port=None):
        with db_api.CONTEXT_WRITER.using(context):
            self.ipam.delete_port(context, id, port)

    def delete_ports_by_device_id(self, context, device_id, network_id=None):
        with db_api.CONTEXT_READER.using(context):
            query = (context.session.query(models_v2.Port.id)
                     .enable_eagerloads(False)
                     .filter(models_v2.Port.device_id == device_id))
            if network_id:
                query = query.filter(models_v2.Port.network_id == network_id)
            port_ids = [p[0] for p in query]
        for port_id in port_ids:
            try:
                self.delete_port(context, port_id)
            except exc.PortNotFound:
                # Don't raise if something else concurrently deleted the port
                LOG.debug("Ignoring PortNotFound when deleting port '%s'. "
                          "The port has already been deleted.",
                          port_id)

    @db_api.retry_if_session_inactive()
    @db_api.CONTEXT_READER
    def get_port(self, context, id, fields=None):
        lazy_fields = [models_v2.Port.port_forwardings,
                       models_v2.Port.distributed_port_binding]
        port = self._get_port(context, id, lazy_fields=lazy_fields)
        return self._make_port_dict(port, fields)

    def _get_ports_query(self, context, *args, filters=None, lazy_fields=None,
                         **kwargs):
        Port = models_v2.Port
        IPAllocation = models_v2.IPAllocation

        limit = kwargs.pop('limit', None)
        filters = filters or {}
        fixed_ips = filters.pop('fixed_ips', {})
        mac_address = filters.pop('mac_address', {})
        vif_type = filters.pop(portbindings_def.VIF_TYPE, None)
        query = model_query.get_collection_query(context, Port,
                                                 filters=filters,
                                                 lazy_fields=lazy_fields,
                                                 *args, **kwargs)
        ip_addresses = fixed_ips.get('ip_address')
        subnet_ids = fixed_ips.get('subnet_id')
        if vif_type is not None:
            query = query.filter(Port.port_bindings.any(vif_type=vif_type))
        if mac_address:
            sanitized_macs = [converters.convert_to_sanitized_mac_address(x)
                              for x in mac_address]
            query = query.filter(
                func.lower(Port.mac_address).in_(sanitized_macs))
        if ip_addresses:
            query = query.filter(
                Port.fixed_ips.any(IPAllocation.ip_address.in_(ip_addresses)))
        if subnet_ids:
            query = query.filter(
                Port.fixed_ips.any(IPAllocation.subnet_id.in_(subnet_ids)))
        if limit:
            query = query.limit(limit)
        query = query.distinct()
        return query

    @db_api.retry_if_session_inactive()
    @db_api.CONTEXT_READER
    def get_ports(self, context, filters=None, fields=None,
                  sorts=None, limit=None, marker=None,
                  page_reverse=False):
        marker_obj = ndb_utils.get_marker_obj(self, context, 'port',
                                              limit, marker)
        lazy_fields = [models_v2.Port.port_forwardings,
                       models_v2.Port.distributed_port_binding]
        query = self._get_ports_query(context, filters=filters,
                                      sorts=sorts, limit=limit,
                                      marker_obj=marker_obj,
                                      page_reverse=page_reverse,
                                      lazy_fields=lazy_fields)
        items = [self._make_port_dict(c, fields, bulk=True) for c in query]
        resource_extend.apply_funcs(port_def.COLLECTION_NAME_BULK, items, None)
        if limit and page_reverse:
            items.reverse()
        return items

    @db_api.retry_if_session_inactive()
    @db_api.CONTEXT_READER
    def get_ports_count(self, context, filters=None):
        return self._get_ports_query(context, filters=filters).count()

    def _enforce_device_owner_not_router_intf_or_device_id(self, context,
                                                           device_owner,
                                                           device_id,
                                                           tenant_id):
        """Prevent tenants from replacing the device id of router ports with
        a router uuid belonging to another tenant.
        """
        if device_owner not in constants.ROUTER_INTERFACE_OWNERS:
            return
        if not context.is_admin:
            # check to make sure device_id does not match another tenants
            # router.
            if device_id:
                if hasattr(self, 'get_router'):
                    try:
                        ctx_admin = context.elevated()
                        router = self.get_router(ctx_admin, device_id)
                    except l3_exc.RouterNotFound:
                        return
                else:
                    l3plugin = directory.get_plugin(plugin_constants.L3)
                    if l3plugin:
                        try:
                            ctx_admin = context.elevated()
                            router = l3plugin.get_router(ctx_admin,
                                                         device_id)
                        except l3_exc.RouterNotFound:
                            return
                    else:
                        # raise as extension doesn't support L3 anyways.
                        raise exc.DeviceIDNotOwnedByTenant(
                            device_id=device_id)
                if tenant_id != router['tenant_id']:
                    raise exc.DeviceIDNotOwnedByTenant(device_id=device_id)

    @db_api.retry_if_session_inactive()
    def add_prefixes(self, context, subnetpool_id, body):
        prefixes = subnetpool_prefix_ops.get_operation_request_body(body)
        with db_api.CONTEXT_WRITER.using(context):
            subnetpool = subnetpool_obj.SubnetPool.get_object(
                context, id=subnetpool_id)

            if not subnetpool:
                raise exc.SubnetPoolNotFound(subnetpool_id=id)
            if len(prefixes) == 0:
                # No prefixes were included in the request, simply return
                return {'prefixes': subnetpool.prefixes}

            new_sp_prefixes = subnetpool.prefixes + prefixes
            sp_update_req = {'subnetpool': {'prefixes': new_sp_prefixes}}
            sp = self.update_subnetpool(context, subnetpool_id, sp_update_req)
            return {'prefixes': sp['prefixes']}

    @db_api.retry_if_session_inactive()
    def remove_prefixes(self, context, subnetpool_id, body):
        prefixes = subnetpool_prefix_ops.get_operation_request_body(body)
        with db_api.CONTEXT_WRITER.using(context):
            subnetpool = subnetpool_obj.SubnetPool.get_object(
                context, id=subnetpool_id)
            if not subnetpool:
                raise exc.SubnetPoolNotFound(subnetpool_id=id)
            if len(prefixes) == 0:
                # No prefixes were included in the request, simply return
                return {'prefixes': subnetpool.prefixes}

            all_prefix_set = netaddr.IPSet(subnetpool.prefixes)
            removal_prefix_set = netaddr.IPSet(list(prefixes))
            if all_prefix_set.isdisjoint(removal_prefix_set):
                # The prefixes requested for removal are not in the prefix
                # list making this a no-op, so simply return.
                return {'prefixes': subnetpool.prefixes}

            subnets = subnet_obj.Subnet.get_objects(
                context, subnetpool_id=subnetpool_id)
            allocated_prefix_set = netaddr.IPSet([x.cidr for x in subnets])

            if not allocated_prefix_set.isdisjoint(removal_prefix_set):
                # One or more of the prefixes requested for removal have
                # been allocated by a real subnet, raise an exception to
                # indicate this.
                msg = _("One or more the prefixes to be removed is in use "
                        "by a subnet.")
                raise exc.IllegalSubnetPoolPrefixUpdate(msg=msg)

            new_prefixes = all_prefix_set.difference(removal_prefix_set)
            new_prefixes.compact()
            subnetpool.prefixes = [str(x) for x in new_prefixes.iter_cidrs()]
            subnetpool.update()
            return {'prefixes': subnetpool.prefixes}
