Support for disabling DHCP server configuration

The distinct possibility exists that a user may wish to utilize
a pre-existing dhcp server.  This is a first initial step to help
facilitate that use case.

Partial-Bug: #1459636
Change-Id: Icb45b1d50f29ad369d1473adbe4ae9f2e03fe5ae

playbooks/roles/ironic-install/README.md

@@ -41,6 +41,12 @@ As for controlling if a partition image is utilized or an image is created with
 create_image_via_dib: true
 transform_boot_image: false
 
+By default this role installs dnsmasq to act as a DHCP server for provisioning hosts.  In the event this is not required, set the following configuration:
+
+include_dhcp_server: false
+
+In the event of an external DHCP server being used, the user will need to configure their DHCP server such that PXE, and iPXE chain loading occurs.
+
 Additional default variables exist in defaults/main.yml, however these are mainly limited to settings which are unlikely to be modified, unless a user has a custom Ironic Python Agent image, or needs to modify where the httpboot folder is set to.
 
 Dependencies

playbooks/roles/ironic-install/defaults/main.yml

@@ -56,3 +56,7 @@ deploy_image_filename: "trusty-server-cloudimg-amd64.img"
 deploy_image: "{{http_boot_folder}}/{{deploy_image_filename}}"
 # Use cirros instead of building an image via diskimage-builder
 use_cirros: false
+# By default Bifrost will deploy dnsmasq to utilize as an integrated DHCP
+# server.  If you already have a DHCP server, you will need to disable
+# this setting, and perform manual configuration of your DHCP server.
+include_dhcp_server: true

playbooks/roles/ironic-install/tasks/main.yml

@@ -171,18 +171,20 @@
   copy: src=/usr/lib/ipxe/undionly.kpxe dest=/tftpboot/
 - name: "Deploy dnsmasq configuration file"
   template: src=dnsmasq.conf.j2 dest=/etc/dnsmasq.conf
+  when: include_dhcp_server == true or '"true" in include_dhcp_server'
 # NOTE(Shrews) When testing, we want to use our custom dnsmasq.conf file,
 # not the one supplied by libvirt. And the libvirt started dnsmasq processes
 # are not controlled by upstart, so we need to manually kill those.
 - name: "Looking for libvirt dnsmasq config"
   stat: path=/etc/dnsmasq.d/libvirt-bin
   register: test_libvirt_dnsmasq
+  when: include_dhcp_server == true or '"true" in include_dhcp_server'
 - name: "Disabling libvirt dnsmasq config"
   command: mv /etc/dnsmasq.d/libvirt-bin /etc/dnsmasq.d/libvirt-bin~
-  when: test_libvirt_dnsmasq.stat.exists == true and testing == true
+  when: (include_dhcp_server == true or '"true" in include_dhcp_server') and test_libvirt_dnsmasq.stat.exists == true and testing == true
 - name: "Stopping existing libvirt dnsmasq processes"
   command: killall -w dnsmasq
-  when: testing == true
+  when: testing == true and (include_dhcp_server == true or '"true" in include_dhcp_server')
 # NOTE(Shrews) We need to enable ip forwarding for the libvirt bridge to
 # operate properly with dnsmasq. This should be done before starting dnsmasq.
 - name: "Enabling IP forwarding in sysctl"
@@ -205,8 +207,12 @@
   service: name={{ item }} state=restarted
   with_items:
     - xinetd
-    - dnsmasq
     - nginx
+- name: "Ensuring dnsmasq is running with current config"
+  service: name={{ item }} state=restarted
+  with_items:
+    - dnsmasq
+  when: include_dhcp_server == true or '"true" in include_dhcp_server'
 - name: "Sending services a reload signal"
   service: name={{ item }} state=reloaded
   with_items:
@@ -214,6 +220,7 @@
     - nginx
 - name: "Sending services a force-reload signal"
   command: /etc/init.d/dnsmasq force-reload
+  when: include_dhcp_server == true or '"true" in include_dhcp_server'
 # Similar logic to below can be utilized to retrieve files
 - name: "Determine if folder exists, else create and populate folder."
   stat: path=/tftpboot/master_images