Deploy custom resolv.conf for OpenStack flavour CC EE

[marwinski]

What would you like to be added:

Our CC EE colleagues requested to have the following option set in the /etc/resolv.conf file:

options rotate timeout:1

The OpenStack extension should ensure a proper /etc/resolv.conf file for this platform flavour. This affects all linux distributions which use systemd-resoled for network name resolution (Ubuntu, Garden Linux).

As an alternative a new kubelet-resolv.conf file could be created with that option and passed to the kubelet via the kubelet resolvConf option.

Why is this needed:

This option is requested by the platform and cannot easily be added by the operating system in a consistent way.

Based on DHCP information or user configuration systemd-resolved creates two resolv.conf files under /run/systemd/resolve:

• resolv.conf
• stub-resolv.conf

One of those two files is normally linked from /etc/resolv.conf. The first contains the name servers as provided by DHCP or configuration. The second points to 127.0.0.53 which is served by systemd-resolved which resolves the request.

There is no option telling systemd-resolved to add the above mentioned option to the resolv.conf file. There is no need to have it in the stub-resolv.conf file as this functionality is taken care of by systemd-resolved.

The problem is that stub-resolve.conf cannot be used by pods as the IP address 127.0.0.53 is not routable from within pods. A resolv.conf file with real DNS server addresses must be used.