[Bug 1857026] Re: OVN doesn't seem to support reverse DNS lookups for instances

[Frode Nordahl]

Deployed focal-wallaby from charm-neutron-api-plugin-ovn gate tests and patched Neutron for some unresolved issues at Wallaby. The need to do that is unfortunate but this verificat
ion is about the OVN pacakges, so let's focus on them.

With two instances running we can see the following information in the OVN DB:
$ sudo ovn-nbctl list dns
_uuid               : a62d480f-e5ad-421e-9e8a-ab4072232331
external_ids        : {ls_name=neutron-7d2d7f7e-ebb9-4625-a2ab-8bb6647f1988}
records             : {"182.0.168.192.in-addr.arpa"=zaza-neutrontests-ins-1.openstack.example, "239.0.168.192.in-addr.arpa"=zaza-neutrontests-ins-2.openstack.example, zaza-neutrontests-ins-1="192.168.0.182", zaza-neutrontests-ins-1.openstack.example="192.168.0.182", zaza-neutrontests-ins-2="192.168.0.239", zaza-neutrontests-ins-2.openstack.example="192.168.0.239"}

Control test:
>From instance forward DNS lookups of other instance names work:
$ host zaza-neutrontests-ins-1.openstack.example
zaza-neutrontests-ins-1.openstack.example has address 192.168.0.182

But reverse DNS lookup of other instance IP does not work:
$ host 192.168.0.182
Host 182.0.168.192.in-addr.arpa. not found: 3(NXDOMAIN)

Upgrade to packages from -proposed:
$ juju run --application ovn-chassis 'dpkg -l | grep ovn'
- Stdout: |
    ii  neutron-ovn-metadata-agent            2:18.1.1-0ubuntu2~cloud0                             all          Neutron is a virtual network service for Openstack - OVN metadata agent
    ii  ovn-common                            20.12.0-0ubuntu3.1~cloud0                            amd64        OVN common components
    ii  ovn-host                              20.12.0-0ubuntu3.1~cloud0                            amd64        OVN host components
  UnitId: ovn-chassis/0
- Stdout: |
    ii  neutron-ovn-metadata-agent            2:18.1.1-0ubuntu2~cloud0                             all          Neutron is a virtual network service for Openstack - OVN metadata agent
    ii  ovn-common                            20.12.0-0ubuntu3.1~cloud0                            amd64        OVN common components
    ii  ovn-host                              20.12.0-0ubuntu3.1~cloud0                            amd64        OVN host components
  UnitId: ovn-chassis/1

Confirm updated packages work:
$ sudo systemctl restart systemd-resolved
$ host zaza-neutrontests-ins-1.openstack.example
zaza-neutrontests-ins-1.openstack.example has address 192.168.0.182
$ host 192.168.0.182
182.0.168.192.in-addr.arpa domain name pointer zaza-neutrontests-ins-1.openstack.example.

** Tags removed: verification-needed verification-wallaby-needed
** Tags added: verification-done verification-wallaby-done

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https://bugs.launchpad.net/bugs/1857026

Title:
  OVN doesn't seem to support reverse DNS lookups for instances

Status in charm-ovn-central:
  Invalid
Status in Ubuntu Cloud Archive:
  Fix Released
Status in Ubuntu Cloud Archive wallaby series:
  Fix Committed
Status in ovn package in Ubuntu:
  Fix Released
Status in ovn source package in Focal:
  Fix Committed
Status in ovn source package in Hirsute:
  Won't Fix

Bug description:
  [Impact]
  At Focal we took a stance that moving forward new deployments of Charmed OpenStack should use OVN as the SDN. For clouds upgrading, Focal is also the point for which a migration from ML2/OVS to ML2/OVN should take place before further upgrades are applied.

  The current lack of support for reverse DNS lookup for IP addresses
  belonging to project instances would prevent users with applications
  depending on this feature to commence new deployments or upgrade
  through Focal and beyond.

  [Test Plan]
  Deploy a Charmed OpenStack and perform forward and reverse DNS lookups for instance names and addresses with the old and new packages to confirm.

  [Regression Potential]
  The instance DNS resolution in OVN works by looking up records in the OVN Southbound database. The CMS adds records for both forward and reverse lookups and the OVN controller needs to know how to look for them. The included patches have been available for several upstream releases without any reported issues. In addition we have been running internal clouds with these patches without issues.

  [Original Bug Description]
  There's an upstream bug that mentions this during implementation of regular DNS lookups - https://bugzilla.redhat.com/show_bug.cgi?id=1503521

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