[RFE] Add agent specific API for l2 agent extensions

I believe the feature request belongs to Mitaka to unblock subprojects. I am open to send a BP for the feature.

Which subproject is blocked by this?

Gary, it's bgpvn and sfc for the start.

I'd like to see proposal (either in the form of devref or spec) that outlines the proposed approach, but yes. If the L2 agent is here to stay and many projects need their services, we gotta figure out a way whereby they can co-exist without hassle.

Based on [1], this needs a spec/devref, but we're to a point where so many initiatives rely on the agents that we can't afford to ignore this problem any further.

[1] http://eavesdrop.openstack.org/meetings/neutron_drivers/2015/neutron_drivers.2015-12-01-15.00.log.html

Fix proposed to branch: master
Review: https://review.openstack.org/263819

Fix proposed to branch: master
Review: https://review.openstack.org/267591

Reviewed: https://review.openstack.org/263819
Committed: https://git.openstack.org/cgit/openstack/neutron-specs/commit/?id=9eb9d7d911b5c5938d0f9af4aea93cbb8399bc10
Submitter: Jenkins
Branch: master

commit 9eb9d7d911b5c5938d0f9af4aea93cbb8399bc10
Author: Ihar Hrachyshka <email address hidden>
Date: Tue Jan 5 18:35:14 2016 +0100

    Agent specific API for L2 agent extensions

    This proposal should be quick to implement and unblock extensions
    interested in injecting OpenFlow rules; while we work on a more long
    term solution that would manage feature flows in a more controlled way.

    Change-Id: I0c6937a747a7930f08a494cf237b6e50f141a49c
    Partial-Bug: #1517903

Reviewed: https://review.openstack.org/267591
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=ea8d60f561d06ec64de26caf39cdb3c397492789
Submitter: Jenkins
Branch: master

commit ea8d60f561d06ec64de26caf39cdb3c397492789
Author: David Shaughnessy <email address hidden>
Date: Wed Jan 13 13:26:57 2016 +0000

    Added agent specific API support to L2 extensions

    - Introduces an API to allow l2-agents to access resources within
      the Open vSwitch Agent, specifically the integration and tunnel bridges.
    - adds consume_api method to the AgentCoreResourceExtension class.
    - modifies the AgentExtensionManager class to accept the AgentExtensionAPI
      class as an optional argument.
    - adds the OVSAgentExtensionAPI class.
    - modifies ovs_lib and ofswitch to include a list of uuid stamps
      to exempt from flow deletion.
    - adds the OVSBridgeCookieMixin class that manages the distribution of
      cookies and maintains the list of reserved cookies.
    - modifies OVSNeutronAgent to initialize OVSAgentExtensionAPI and pass
      into the AgentExtensionManager.

    Partial-Bug: #1517903
    Co-Authored-By: Nate Johnston <email address hidden>
    Co-Authored-By: Thomas Morin <email address hidden>
    Implements: blueprint l2-api-extensions

    Change-Id: I7cb61f30689dff2d7895d444060dedc1532a63ec

Documented in devref: https://review.openstack.org/#/c/287263/