Comment 13 for bug 1826419

Ubuntu SRU information

[Impact]
Use of Neutron internal DNS resolution for resolution of instances attached to the same project network is inconsistent due to use of configuration options for the actual hostname entries in the dnsmasq hosts file paired with the network 'dns_domain' attribute which is used to set the search path for the same dnsmasq instance.

[Test Case]
Deploy OpenStack with Neutron internal DNS support enabled
Configure neutron with a dns_domain of 'testcase.internal'
Set a dns_domain attribute on the project network ('designate.local')
Boot an instance attached to the network
DNS resolution within the host will be asymmetric in terms of the actual dns domain used.

  root@bionic-045546-2:~# host 192.168.21.222
  222.21.168.192.in-addr.arpa domain name pointer bionic-045546-2.testcase.internal.

  root@bionic-045546-2:~# host bionic-045546-2
  bionic-045546-2.designate.local has address 192.168.21.222

which should be

  root@bionic-045546-2:~# host bionic-045546-2
  bionic-045546-2.testcase.local has address 192.168.21.222

[Regression Potential]
Minimal; the proposed fix actually reverts changes in Neutron which altered the behaviour of the internal DNS support in Neutron incorrectly.

[Other Info]
This change in behaviour has been discussed at the upstream Neutron irc meeting with consensus that the behaviour changes are incorrect and should be reverted.