Switch OVS agent to l2 agent extensions

[Haim Daniel]

Currently the OVSSfcAgent inherits from OVSNeutronAgent in order to reuse it's code. This implementation has a few drawbacks:

1. Many lines of OVSNeutronAgent are still duplicated, as the overriden functions have no support for inserting sfc specific logic in them. This is considered bad practice according to the neutron stadium guidelines: http://docs.openstack.org/developer/neutron/stadium/sub_project_guidelines.html#code-reuse

2. This is fragile and each change in OVSNeutronAgent can potentially break the code, since the SfcAgent lives outside of the neutron tree, and there are no backwards api compatibility guarantees.

The more proper and robust way is by using l2 extensions as described here: http://docs.openstack.org/developer/neutron/devref/l2_agent_extensions.html#open-vswitch-agent-api

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/334398

[Bernard Cafarelli (bcafarel)]

I will take a look at it

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/351789

[OpenStack Infra (hudson-openstack)]

Change abandoned by Ihar Hrachyshka (<email address hidden>) on branch: master
Review: https://review.openstack.org/334398
Reason: I guess SFC folks go with longer approach: https://review.openstack.org/#/c/351789/ and won't land this as a short term fix.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/351789
Committed: https://git.openstack.org/cgit/openstack/networking-sfc/commit/?id=518395e6b2ab028c6b3955fd96c074d6efb83527
Submitter: Jenkins
Branch: master

commit 518395e6b2ab028c6b3955fd96c074d6efb83527
Author: Bernard Cafarelli <email address hidden>
Date: Fri Aug 5 16:56:13 2016 +0200

    Replace OVSSfcAgent by a L2 agent extension

    Currently the OVSSfcAgent inherits from OVSNeutronAgent in order to
    reuse its code. This commit replaces it by a L2 agent extension.

    The L2 agent extension handles generic code, and dispatches specific
    code to driver modules.

    The only supported driver currently is Open vSwitch.

    This is enabled by adding sfc to agent->extensions configuration
    parameter in ml2_conf.ini

    Change-Id: I6bd4fd80e312d48287b2bc7b44e3cdcdf3bdf508
    Closes-Bug: #1586024

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/networking-sfc 3.0.0 release.