Meetings/Neutron blueprint ovs-firewall-driver

Purpose restatement
Design decisions
- openvswitch statelessness and security groups frontend API and DB: https://etherpad.openstack.org/p/ovs-firewall-driver-stateless-2
Overview of prototype
- all security group flows on integration bridge
- currently all on table 0, thinking about multi-table setup
- prototype tested on flat network setup; should work on other network types as-is since the tunnel OVS flows just pass the data to the integration bridge
- still a WIP: barely functional
  - adding IPv6 flows
  - adding multiple ports in range: debating trying out port bitmask or N flows for N ports?
  - TODO unit/integration tests (integration tests help is always appreciated)
Miscellaneous items:
- ovs_neutron_agent issues:
  - (1) firewall invoked before agent does anything in C[R]UD operations
    - need to at least extract VLAN provisioning out before firewall invocation (to have correct OVS action on ALLOW path)
  - (2) agent removes all flows at initialization (as well as deletes all vif's flows on port_bound)
- lacking ovs atomicity like iptables-restore has (all connections might be dropped/allowed): one possibility is to have a dynamic multi-table hotswap
- neutron-rootwrap-xen-dom0 bugs: https://bugs.launchpad.net/neutron/+bug/1185872/comments/3, https://bugs.launchpad.net/neutron/+bug/1259748
- table, priority, cookie, actions coordination: ok for now to be hard-coded in Neutron, but will need an abstraction layer in the future possibly