[Bug 1783654] Re: DVR process flow not installed on physical bridge for shared tenant network

[Timo Aaltonen]

Hello Arjun, or anyone else affected,

Accepted neutron into bionic-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/neutron/2:12.0.4-0ubuntu1 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-bionic to verification-done-bionic. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-bionic. In either case, without details of
your testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance!

** Changed in: neutron (Ubuntu Bionic)
       Status: Triaged => Fix Committed

** Tags added: verification-needed verification-needed-bionic

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