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This bug was fixed in the package neutron - 2:13.0.1-0ubuntu1

---------------
neutron (2:13.0.1-0ubuntu1) cosmic; urgency=medium

  * New stable point release for OpenStack Rocky.
  * d/p/revert-dvr-add-error-handling.patch: Cherry-picked from upstream to
    revert DVR regressions (LP: #1751396)
  * d/p/revert-dvr-inter-tenant.patch: Cherry-picked from upstream to revert
    DVR regression (LP: #1783654).

 -- Corey Bryant <corey.bryant@xxxxxxxxxxxxx>  Tue, 02 Oct 2018 17:18:19
-0400

** Changed in: neutron (Ubuntu Cosmic)
       Status: Triaged => Fix Released

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https://bugs.launchpad.net/bugs/1783654

Title:
  DVR process flow not installed on physical bridge for shared tenant
  network

Status in Ubuntu Cloud Archive:
  Triaged
Status in Ubuntu Cloud Archive pike series:
  Invalid
Status in Ubuntu Cloud Archive queens series:
  Triaged
Status in Ubuntu Cloud Archive rocky series:
  Triaged
Status in neutron:
  Fix Released
Status in neutron package in Ubuntu:
  Fix Released
Status in neutron source package in Bionic:
  Triaged
Status in neutron source package in Cosmic:
  Fix Released

Bug description:
  Seems like collateral from
  https://bugs.launchpad.net/neutron/+bug/1751396

  In DVR, the distributed gateway port's IP and MAC are shared in the
  qrouter across all hosts.

  The dvr_process_flow on the physical bridge (which replaces the shared
  router_distributed MAC address with the unique per-host MAC when its
  the source), is missing, and so is the drop rule which instructs the
  bridge to drop all traffic destined for the shared distributed MAC.

  Because of this, we are seeing the router MAC on the network
  infrastructure, causing it on flap on br-int on every compute host:

  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
     11     4  fa:16:3e:42:a2:ec    1
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
     11     4  fa:16:3e:42:a2:ec    2
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
      1     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
     11     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
     11     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
      1     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
      1     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
      1     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
      1     4  fa:16:3e:42:a2:ec    1
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
     11     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
     11     4  fa:16:3e:42:a2:ec    0
  root@milhouse:~# ovs-appctl fdb/show br-int | grep fa:16:3e:42:a2:ec
     11     4  fa:16:3e:42:a2:ec    0

  Where port 1 is phy-br-vlan, connecting to the physical bridge, and
  port 11 is the correct local qr-interface. Because these dvr flows are
  missing on br-vlan, pkts w/ source mac ingress into the host and br-
  int learns it upstream.

  The symptom is when pinging a VM's floating IP, we see occasional
  packet loss (10-30%), and sometimes the responses are sent upstream by
  br-int instead of the qrouter, so the ICMP replies come with fixed IP
  of the replier since no NAT'ing took place, and on the tenant network
  rather than external network.

  When I force net_shared_only to False here, the problem goes away:
  https://github.com/openstack/neutron/blob/stable/pike/neutron/plugins/ml2/drivers/openvswitch/agent/ovs_dvr_neutron_agent.py#L436

  It should we noted we *ONLY* need to do this on our dvr_snat host. The
  dvr process's are missing on every compute host. But if we shut
  qrouter on the snat host, FIP functionality works and DVR mac stops
  flapping on others. Or if we apply fix only to snat host, it works.
  Perhaps there is something on SNAT node that is unique


  Ubuntu SRU details:
  -------------------
  [Impact]
  See above

  [Test Case]
  Deploy OpenStack with dvr enabled and then follow the steps above.

  [Regression Potential]
  The patches that are backported have already landed upstream in the corresponding stable branches, helping to minimize any regression potential.

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