text: # Copyright (C) 2014,2015 VA Linux Systems Japan K.K.
  # Copyright (C) 2014,2015 YAMAMOTO Takashi <yamamoto at valinux co jp>
  # All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  from oslo_log import log as logging
  from oslo_utils import excutils
  
  from neutron._i18n import _
  from neutron.agent.common import ovs_lib
  from neutron.plugins.ml2.drivers.openvswitch.agent.common import constants \
          as ovs_consts
  from neutron.plugins.ml2.drivers.openvswitch.agent.openflow \
      import br_cookie
  from neutron.plugins.ml2.drivers.openvswitch.agent.openflow.native \
      import ofswitch
  
  
  LOG = logging.getLogger(__name__)
  
  
  class OVSAgentBridge(ofswitch.OpenFlowSwitchMixin,
                       br_cookie.OVSBridgeCookieMixin, ovs_lib.OVSBridge):
      """Common code for bridges used by OVS agent"""
  
      _cached_dpid = None
  
      def _get_dp(self):
          """Get (dp, ofp, ofpp) tuple for the switch.
  
          A convenient method for openflow message composers.
          """
          while True:
              if self._cached_dpid is None:
                  dpid = self.get_datapath_id()
                  LOG.info("Bridge %(br_name)s has datapath-ID %(dpid)s",
                           {"br_name": self.br_name, "dpid": dpid})
                  if dpid is None:
                      raise RuntimeError(_("Unknown datapath id."))
                  self._cached_dpid = int(dpid, 16)
              try:
                  dp = self._get_dp_by_dpid(self._cached_dpid)
                  return dp, dp.ofproto, dp.ofproto_parser
              except RuntimeError:
                  with excutils.save_and_reraise_exception() as ctx:
                      # Retry if dpid has been changed.
                      # NOTE(yamamoto): Open vSwitch change its dpid on
                      # some events.
                      # REVISIT(yamamoto): Consider to set dpid statically.
                      new_dpid = int(self.get_datapath_id(), 16)
                      if new_dpid != self._cached_dpid:
                          LOG.info("Bridge %(br_name)s changed its "
                                   "datapath-ID from %(old)x to %(new)x", {
                                       "br_name": self.br_name,
                                       "old": self._cached_dpid,
                                       "new": new_dpid,
                                   })
                          ctx.reraise = False
                      self._cached_dpid = new_dpid
  
      def setup_controllers(self, conf):
          controllers = [
              "tcp:%(address)s:%(port)s" % {
                  "address": conf.OVS.of_listen_address,
                  "port": conf.OVS.of_listen_port,
              }
          ]
          self.add_protocols(ovs_consts.OPENFLOW13)
          self.set_controller(controllers)
  
          # NOTE(ivc): Force "out-of-band" controller connection mode (see
          # "In-Band Control" [1]).
          #
          # By default openvswitch uses "in-band" controller connection mode
          # which adds hidden OpenFlow rules (only visible by issuing ovs-appctl
          # bridge/dump-flows <br>) and leads to a network loop on br-tun. As of
          # now the OF controller is hosted locally with OVS which fits the
          # "out-of-band" mode. If the remote OF controller is ever to be
          # supported by openvswitch agent in the future, "In-Band Control" [1]
          # should be taken into consideration for physical bridge only, but
          # br-int and br-tun must be configured with the "out-of-band"
          # controller connection mode.
          #
          # [1] https://github.com/openvswitch/ovs/blob/master/DESIGN.md
          self.set_controllers_connection_mode("out-of-band")
  
      def drop_port(self, in_port):
          self.install_drop(priority=2, in_port=in_port)
  