[Bug 1948466] Re: [OVN] Mech driver fails to delete DHCP options during subnet deletion

[Andreas Hasenack]

Hello Rodolfo, or anyone else affected,

Accepted neutron into focal-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/neutron/2:16.4.2-0ubuntu6.3 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, what testing has been
performed on the package and change the tag from verification-needed-
focal to verification-done-focal. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-focal. 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 for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

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

** Tags added: verification-needed verification-needed-focal

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https://bugs.launchpad.net/bugs/1948466

Title:
  [OVN] Mech driver fails to delete DHCP options during subnet deletion

Status in Ubuntu Cloud Archive:
  Fix Released
Status in Ubuntu Cloud Archive ussuri series:
  Triaged
Status in neutron:
  Fix Released
Status in neutron package in Ubuntu:
  Fix Released
Status in neutron source package in Focal:
  Fix Committed

Bug description:
  == Original Bug Description ==

  Snippet: https://paste.opendev.org/show/810168/

  I can't provide a link to a CI execution, I saw this error in an
  internal CI. I'm still investigating when this could happen.

  == Ubuntu SRU Details ==

  [Impact]

  During subnet deletion the check in _remove_subnet_dhcp_options()
  results in the following traceback (taken from pastebin above in case
  it disappears) if dhcp_options['subnet'] is an empty dictionary:

  ExternalNetworksRBACTestJSON-2078932943-project-admin] Mechanism driver 'ovn' failed in delete_subnet_postcommit: KeyError: 'uuid'
   Traceback (most recent call last):
     File "/opt/stack/neutron/neutron/plugins/ml2/managers.py", line 482, in _call_on_drivers
       getattr(driver.obj, method_name)(context)
     File "/opt/stack/neutron/neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py", line 637, in delete_subnet_postcommit
       self._ovn_client.delete_subnet(context._plugin_context,
     File "/opt/stack/neutron/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py", line 2103, in delete_subnet
       self._remove_subnet_dhcp_options(subnet_id, txn)
     File "/opt/stack/neutron/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py", line 1971, in _remove_subnet_dhcp_options
       dhcp_options['subnet']['uuid']))
   KeyError: 'uuid'

  The fix ensures this check handles a dictionary correctly.

  [Test Case]

  In case we don't have a recreate for this:

  1) lxc launch ubuntu-daily:focal f1 && lxc exec f1 /bin/bash
  2) sudo add-apt-repository -p proposed
  3) sudo apt install python3-neutron
  4) cd /usr/lib/python3/dist-packages
  5) python3 -m unittest neutron.tests.unit.plugins.ml2.drivers.ovn.mech_driver.test_mech_driver.TestOVNMechanismDriver.test_remove_subnet_dhcp_options_in_ovn_ipv4
  6) re-run the test in step #5 after adding 'pdb.set_trace()' to the line before the check in neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py
     this way we can see what dhcp_options['subnet'] is set to, ensure the check behaves correctly, and try another run with dhcp_options['subnet'] = {}
  7) sudo add-apt-repository -r -p proposed

  [Regression Potential]

  This is a minimal change that is backward compatible with the previous
  check. The new check can still handle 'not None' in addition to
  handling an empty dictionary correctly. This has been fixed in Ubuntu
  Victoria packages (and above) since 2022-01-12, and has been fixed in
  the upstream stable/ussuri branch since 2021-10-25.

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