[Bug 1892405] Re: Removing router interface causes router to stop routing between all

[Corey Bryant]

This is fixed in hirsute-proposed now with neutron
2:17.0.0+git2020120911.b5ea767bc3-0ubuntu2.

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https://bugs.launchpad.net/bugs/1892405

Title:
  Removing router interface causes router to stop routing between all

Status in Ubuntu Cloud Archive:
  Triaged
Status in Ubuntu Cloud Archive ussuri series:
  Triaged
Status in Ubuntu Cloud Archive victoria series:
  Triaged
Status in neutron:
  In Progress
Status in neutron package in Ubuntu:
  Triaged
Status in neutron source package in Focal:
  Triaged
Status in neutron source package in Groovy:
  Triaged
Status in neutron source package in Hirsute:
  Triaged

Bug description:
  [Impact]
  Stumbled upon an issue where removing a DVR HA router interface renders all other subnets connected to that router to stop routing. VMs can't reach the HA port (IP) of the router (ping).

  Worked around this by:
  openstack router set --disabled <ROUTER>
  openstack router set --enable <ROUTER>

  This has happened more than once in the current deployment
   - cloud:bionic-stein
   - neutron 2:14.0.4-0ubuntu1~cloud1

  [Test Case]
  1. Reproducing the issue

  1a. Deploy openstack using stsstack-bundles
      https://launchpad.net/stsstack-bundles
       
  1b. Run the test script lp1892405_reproducer from comment #10

      The script does the following (Detailed steps in comment #4)
      - Create 3 projects P1, P2, P3
      - Create a router and network in each project, say R1,R2,R3 and 
        N1,N2,N3
      - Cross-connect networks by adding ports to router.
      - Launch VMs on N1, N2 (Ensure VMs are landed on 2 different compute 
        nodes)
      - ping from VM1 -> VM2 should be successful
      - Detach leg from N1 -> N3
      - Check for any packet loss during ping from VM1 -> VM2

      The script output shows the ping output from VM1 -> VM2 and there will 
      be packet loss            

  2. Install the package with fixed code

  3. Confirm bug have been fixed

  3a. Cleanup of projects P1,P2,P3 and associated resources created in 1b
      Re-enable the hypervisor which is disabled as part of 1b script.
      Command to enable:
      openstack compute service set --disable <hypervisor hostname> nova- 
      compute

  3b. Re-run the script 1b

      The script output shows the ping output from VM1 -> VM2 and there 
      should not be any packet loss

  [Where problems could occur]

  Upstream CI ran all the functional and tempest test cases that involves deletion of DVR port connected to router which should cover the scenarios involving the code change.
  Installation of new package will result in restart of neutron-openvswitch service and will take a few milliseconds to repopulate all the OVS flows.

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