configure the undercloud to use nameservers from virthost

When using libvirt, use nameserver derived from the
virthost /etc/resolv.conf file. This should work in
public/private networks.

Depends-On: I1e8e9d26469ac0034819c94029360379e2c6140c
Change-Id: Id35120df9dd5331e64a06ee886ccd64edf8834ec

roles/undercloud-deploy/defaults/main.yml

@@ -52,3 +52,7 @@ novajoin_connect_timeout: 5
 novajoin_read_timeout: 20
 
 libvirt_default_network_address: 192.168.122.1
+
+# only to be used in libvirt deployments, see environment config for details
+nameserver_from_virthost: false
+virthost_nameservers: []

roles/undercloud-deploy/tasks/create-scripts.yml

@@ -1,5 +1,17 @@
 # Creat the scripts that will be used to deploy the undercloud
 # environment.
+- name: Check the dns information provided by the virthost
+  shell: >
+    gawk '/^nameserver +/ { print $2 }' /etc/resolv.conf
+  delegate_to: virthost
+  register: virthost_nameservers_output
+  when: nameserver_from_virthost|bool
+
+- name: set name server facts
+  set_fact:
+    virthost_nameservers: "{{ virthost_nameservers_output.stdout_lines }}"
+  when: nameserver_from_virthost|bool
+
 - name: Create undercloud configuration
   template:
     src: "{{ undercloud_config_file }}"

roles/undercloud-deploy/templates/undercloud.conf.j2

@@ -74,7 +74,11 @@ undercloud_admin_host = {{undercloud_undercloud_admin_host|default(
 
 # Nameserver for the Undercloud node.
 # (string value)
-{% if undercloud_undercloud_nameservers is string %}
+{% if virthost_nameservers is string %}
+undercloud_nameservers = {{ virthost_nameservers }}
+{% elif virthost_nameservers is sequence and virthost_nameservers|length > 0 %}
+undercloud_nameservers = {{ virthost_nameservers|join(',') }}
+{% elif undercloud_undercloud_nameservers is string %}
 undercloud_nameservers = {{ undercloud_undercloud_nameservers }}
 {% elif undercloud_undercloud_nameservers is sequence %}
 undercloud_nameservers = {{ undercloud_undercloud_nameservers|join(',') }}