Fix NodeLocal DNS IPv6 address formatting (missing [] for host:port) in IPv6-only deployments

[kanyahal06]

What would you like to be added

• When deploying an IPv6-only Kubernetes cluster using Kubespray v2.29.1 with:

  ipv6_stack: true
  ipv4_stack: false
  

  in the k8s-cluster.yml

• The nodelocaldns pods fail to start and continuously crash. On inspecting the logs, the issue is traced to incorrect IPv6 address formatting in the generated nodelocaldns ConfigMap.

• In the template: "roles/kubernetes-apps/ansible/templates/nodelocaldns-config.yml.j2"

  IPv6 addresses are rendered without square brackets [] when used in IP:port format.
  Example (current behavior):
  fd00::10:53

  This is invalid for IPv6 when combined with ports and leads to parsing failures.
  Correct format should be:
  [fd00::10]:53

• Update the nodelocaldns-config.yml.j2 template to conditionally wrap IPv6 addresses with square brackets when used with ports.

  {% if ipv6_stack and not ipv4_stack %}
  [{{ some_ip }}]:{{ port }}
  {% else %}
  {{ some_ip }}:{{ port }}
  {% endif %}
  

Why is this needed

• nodelocaldns pods fail to start
• Continuous crash loops observed
• DNS resolution inside the cluster is impacted
• Breaks functionality in IPv6-only clusters