okd/playbooks/init/validate_hostnames.yml

---
- name: Validate node hostnames
  hosts: oo_nodes_to_config
  tasks:
  - name: Query DNS for IP address of {{ openshift.common.hostname }}
    shell:
      getent ahostsv4 {{ openshift.common.hostname }} | head -n 1 | awk '{ print $1 }'
    register: lookupip
    changed_when: false
    failed_when: false
  - name: Warn user about bad openshift_hostname values
    pause:
      prompt:
        The hostname {{ openshift.common.hostname }} for {{ ansible_nodename }}
        doesn't resolve to an IP address owned by this host. Please set
        openshift_hostname variable to a hostname that when resolved on the host
        in question resolves to an IP address matching an interface on this
        host. This host will fail liveness checks for pods utilizing hostPorts,
        press ENTER to continue or CTRL-C to abort.
      seconds: "{{ 10 if openshift_override_hostname_check | default(false) | bool else omit }}"
    when:
    - lookupip.stdout != '127.0.0.1'
    - lookupip.stdout not in ansible_all_ipv4_addresses