Comment 0 for bug 1671379

Description
===========
Normaly, VM which migrates to destination node can send several RARP packets during KVM's live-migration in my openstack environment.
In neutron ML2 hierarchical port binding environment,
I find that the physical port associated to a vlan physical provider's ovs bridge on destination node cannot dump any rarp packets when VM migrates to destination node.

Steps to reproduce
==================
1. create a vxlan type network: netA
2. create a subnet for netA: subA
3. create a vm in compute1 node: vmA
4. tcpdump the physical port associated to a ovs bridge in compute2 node: tcpdump -i ens33 -w ens33.pcap
5. live migrate the vm to the other compute node: compute2 node
6. open ens33.pcap in wireshark

Expected result
===============
find several rarp packets

Actual result
=============
find not any rarp packets

Environment
===========
OpenStack：Kilo 2015.1.2
OS: CentOS 7.1.1503
Libvirt：1.2.17

Logs & Configs
==============
hierarchical port binding configuration:
controller node:
#neutron
/etc/neutron/plugins/ml2/ml2_conf.ini
[ml2]
type_drivers = vxlan,vlan
tenant_network_types = vxlan,vlan
mechanism_drivers=ml2_h3c,openvswitch
#ml2_h3c, a mechanism driver owned by New H3C Group which is a provider of New IT solutions , allocates dynamic
#vlan segment for the existing mechanism driver "openvswitch"

[ml2_type_vlan]
network_vlan_ranges = compute1_physicnet1:100:1000, compute2_physicnet1:100:1000
[ml2_type_vxlan]
vni_ranges=1:500

compute1 node:
#neutron
/etc/neutron/plugins/openvswitch/ovs_neutron_plugin.ini
[ovs]
bridge_mappings=compute1_physicnet1:br-ens33

compute2 node:
#neutron
/etc/neutron/plugins/openvswitch/ovs_neutron_plugin.ini
[ovs]
bridge_mappings=compute2_physicnet1:br-ens33

Analysis
==============
After reading the live-migration relevant code of nova, neutron-server and neutron-openvswitch-agent, I think that it may be a bug.

The brief relevant process：

1. source compute node(nova-compute) compute1 node
   self.driver(libvirt).live_migration
         dom.migrateToURI2 ---------------Excecute migration to dest node
         self._live_migration_monitor------------------ Monitor migration finished
             self._post_live_migration ---------------- Migration finished
                 self.compute_rpcapi.post_live_migration_at_destination --------- Notify destination node

2.1. destination compute node (neutron-openvswitch-agent) compute2 node
   rpc_loop ------ monitor vm's tapxxxx port plug
      self.process_network_ports
         self.treat_devices_added_or_updated
              self.plugin_rpc.get_devices_details_list -------The port details shows that the port still is bound to
                                                               "compute1_physicnet1", not the physical network
                                                                provider "compute2_physicnet1" existing in
                                                               destination compute node.
              self.treat_vif_port
                  self.port_bound
                      self.provision_local_vlan ----------- There is not matched physical bridge at the time. As a
                                                             result, the tap port can not been set any vlan tag.
                                                             Eventually, br-ens33, the physical bridge, drops rarp
                                                             packets from the starting vm.

2.2 destination compute node (nova-compute) compute2 node
    post_live_migration_at_destination nova/compute/manager.py
        self.network_api.migrate_instance_finish
            self._update_port_binding_for_instance ------------Notify neutron migrate port binding:host_id

3. controller node(neutron-server)
   ml2_h3c: fill self._new_bound_segment and self._next_segments_to_bind with compute2_physicnet1
            for openvswitch driver
   openvswitch: bind port with compute2_physicnet1's allocated segment from level 0 driver ml2_h3c

In the current process of kilo, ml2 driver finishes port bind at the last step 3.
it's too late to make neutron-openvswitch-agent get suitable port details from neutron-server
to set correct vlan tag for vm port and adds relevant flow for ovs bridges that nova notifies neutron-server the
event that port changes binding_hostid in ml2 hierarchical port binding.

It seems that liberty, mitaka exists the same problem.