undercloud subnet dns_nameservers option default overrides undercloud_nameservers in global conf

[Harald Jensås]

Using 'undercloud_nameservers' in global config broken by mistake in https://review.opendev.org/#/c/667380?

 Related Infrared change: https://review.gerrithub.io/c/redhat-openstack/infrared/+/471626

UPDATE:
 constants.CTLPLANE_DNS_NAMESERVERS_DEFAULT = []

This is the default for [ctlplane-subnet]/dns_nameservers

Code[1] - should set 'undercloud_nameservers' if [ctlplane-subnet]/dns_nameservers is not-set (i.e default [])
        if s.get('dns_nameservers'):
            env['UndercloudCtlplaneSubnets'][subnet].update(
                {'DnsNameServers': s['dns_nameservers']})
        else:
            env['UndercloudCtlplaneSubnets'][subnet].update(
                {'DnsNameServers': CONF['undercloud_nameservers']})

It is possible this worked in CI because of this script that removed test coverage in CI executes:
https://review.opendev.org/#/c/296362/3/scripts/tripleo.sh

[1] https://opendev.org/openstack/python-tripleoclient/src/branch/master/tripleoclient/v1/undercloud_config.py#L340-L345

[Harald Jensås (harald-jensas)]

We have unit test coverage that show's that setting the subnets dns_nameserver = [] and undercloud_nameservers = ['10.10.10.10', '10.10.10.11'] set 'DnsNameServers': ['10.10.10.10', '10.10.10.11'].

https://opendev.org/openstack/python-tripleoclient/src/branch/master/tripleoclient/tests/v1/undercloud/test_config.py#L129
https://opendev.org/openstack/python-tripleoclient/src/branch/master/tripleoclient/tests/v1/undercloud/test_config.py#L175

The reporter tell me overcloud nodes got 192.168.24.5 as nameserver. constants.CTLPLANE_DHCP_START_DEFAULT = ['192.168.24.5'], if no nameserver is specified when creating the subnet neutron probably default to the IP address of the dhcp agent's dnsmasq which is the first address of the allocation pool.

The reporter assure's me that undercloud_nameservers = 10.10.160.1 is set in undercloud.conf.

[Harald Jensås (harald-jensas)]

Trying to reproduce with
########################

file: undercloud.conf
-------------------------------------------------------------------
[DEFAULT]

local_interface = eth1
local_ip = 172.20.0.1/26
undercloud_admin_host = 172.20.0.2
undercloud_hostname = leafs.lab.example.com
undercloud_nameservers = 172.20.0.254
undercloud_ntp_servers = 0.se.pool.ntp.org
undercloud_public_host = 172.20.0.3
undercloud_debug = true

[ctlplane-subnet]
cidr = 172.20.0.0/26
dhcp_start = 172.20.0.10
dhcp_end = 172.20.0.19
inspection_iprange = 172.20.0.20,172.20.0.29
gateway = 172.20.0.62
masquerade = true
-------------------------------------------------------------------

Result
######

file: tripleo-config-generated-env-files/undercloud_parameters.yaml
-------------------------------------------------------------------
  UndercloudCtlplaneSubnets:
    ctlplane-subnet:
      AllocationPools:
      - end: 172.20.0.19
        start: 172.20.0.10
      DnsNameServers:
      - 172.20.0.254 <-- DnsNameservers == undercloud_nameservers
      HostRoutes: []
      NetworkCidr: 172.20.0.0/26
      NetworkGateway: 172.20.0.62
-------------------------------------------------------------------

(undercloud) [stack@leafs ~]$ openstack subnet show ctlplane-subnet -c dns_nameservers
+-----------------+--------------+
| Field | Value |
+-----------------+--------------+
| dns_nameservers | 172.20.0.254 |
+-----------------+--------------+

[Harald Jensås (harald-jensas)]

Works for me: https://bugs.launchpad.net/tripleo/+bug/1848517/comments/2