Implement DVR-aware announcement of fixed IP's in neutron-dynamic-routing

[Ryan Tidwell]

The current implementation of neutron-dynamic-routing is compatible with DVR, but is not optimized for DVR. It currently announces next-hops for all tenant subnets through the central router on the network node. Announcing next-hops via the FIP gateway on the compute node was never implemented due to the pre-requisite of having DVR fast-exit in place for packets to be routed through the FIP namespace properly. With DVR fast-exit now in place, it's time to consider adding DVR-aware /32 and/or /128 announcements for fixed IP's using the FIP gateway as the next-hop.

[Ryan Tidwell (ryan-tidwell)]

Just adding a little more context:

This was initially within the scope of the initial implementation for mitaka. However, we realized that DVR fast-exit was required to actually have packets forwarded through the FIP namespace. I've had the code for this floating around for a while but never proposed it for review since it seemed pointless to push code that would just cause network traffic to black-hole. The changes I have (and am close to deploying internally) involve:

1. adding an attribute to the bgp-speaker extension to allow toggling of DVR-aware announcements
2. adding a method to https://github.com/openstack/neutron-dynamic-routing/blob/master/neutron_dynamic_routing/db/bgp_db.py for looking up DVR fixed IP routes
3. adding a line here https://github.com/openstack/neutron-dynamic-routing/blob/master/neutron_dynamic_routing/db/bgp_db.py#L478 to include the DVR fixed IP routes
4. subscribing to PORT_UPDATE events to be able to push a route update to the appropriate agents when a live migration occurs

Obviously we don't have to hash out the details here and what I have right now will be iterated on, but I just wanted to share my sense of the scope of the changes involved.

[Miguel Lavalle (minsel)]

@Ryan,

Thanks for the additional context. It seems like a sensible next step. We will discuss this RFE in the next drivers meeting.

I am assuming you will propose the same code you will be testing in your employer's internal deployment, correct?

[Ryan Tidwell (ryan-tidwell)]

Correct. The first patch set to be proposed would be what I've posted internally. Obviously that is only a starting point and can be iterated and improved upon based on reviewer feedback.

[Miguel Lavalle (minsel)]

This RFE was reviewed and approved during today's drivers meeting

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/581098

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/581098
Committed: https://git.openstack.org/cgit/openstack/neutron-dynamic-routing/commit/?id=69e9888b0159ba3c9af09e1eceb48df76e4be839
Submitter: Zuul
Branch: master

commit 69e9888b0159ba3c9af09e1eceb48df76e4be839
Author: Ryan Tidwell <email address hidden>
Date: Tue May 29 12:40:30 2018 -0500

    Implement DVR-aware fixed IP lookups

    This change adds DVR-aware announcements for routable fixed IP's
    to be sent, thereby routing traffic directly to the appropriate
    compute node instead of the centralized router on the network node.

    Change-Id: I3aecdd7979dba97dab12a6550655c90a57f56cb3
    Partial-Bug: #1775250

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/rocky
Review: https://review.opendev.org/686225

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/686225
Committed: https://git.openstack.org/cgit/openstack/neutron-dynamic-routing/commit/?id=032486a3a4a3279c824b5e78f7c13c6086a680d4
Submitter: Zuul
Branch: stable/rocky

commit 032486a3a4a3279c824b5e78f7c13c6086a680d4
Author: Ryan Tidwell <email address hidden>
Date: Tue May 29 12:40:30 2018 -0500

    Implement DVR-aware fixed IP lookups

    This change adds DVR-aware announcements for routable fixed IP's
    to be sent, thereby routing traffic directly to the appropriate
    compute node instead of the centralized router on the network node.

    Conflicts:
        neutron_dynamic_routing/db/bgp_db.py

    Change-Id: I3aecdd7979dba97dab12a6550655c90a57f56cb3
    Partial-Bug: #1775250
    (cherry picked from commit 69e9888b0159ba3c9af09e1eceb48df76e4be839)