Add support for default dns for subnet

This change allows a configurable default dns server list
which will be pre-populated within the subnet creation screen.

Change-Id: I89f3813ec6a5a05b575ea1bc775a861f2d2f1e59
Closes-bug: #1504680

doc/source/topics/settings.rst

@@ -1333,6 +1333,18 @@ a later release. If there exists a default Subnet Pool it will be automatically
 detected through the Neutron API and the label will be set to the name of the
 default Subnet Pool.
 
+``default_dns_nameservers``:
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. versionadded:: 10.0.0(Newton)
+
+Default: ``None`` (Empty)
+
+Default DNS servers you would like to use when a subnet is created. This is
+only a default. Users can still choose a different list of dns servers.
+
+Example: ``["8.8.8.8", "8.8.4.4", "208.67.222.222"]``
+
 ``OPENSTACK_SSL_CACERT``
 ------------------------
 

openstack_dashboard/dashboards/project/networks/subnets/views.py

@@ -15,6 +15,7 @@
 """
 Views for managing Neutron Subnets.
 """
+from django.conf import settings
 from django.core.urlresolvers import reverse
 from django.utils.translation import ugettext_lazy as _
 
@@ -48,10 +49,17 @@ class CreateView(workflows.WorkflowView):
             msg = _("Unable to retrieve network.")
             exceptions.handle(self.request, msg, redirect=redirect)
 
+    def get_default_dns_servers(self):
+        # this returns the default dns servers to be used for new subnets
+        dns_default = "\n".join(getattr(settings, 'OPENSTACK_NEUTRON_NETWORK',
+                                        {}).get('default_dns_nameservers', ''))
+        return dns_default
+
     def get_initial(self):
         network = self.get_object()
         return {"network_id": self.kwargs['network_id'],
-                "network_name": network.name_or_id}
+                "network_name": network.name_or_id,
+                "dns_nameservers": self.get_default_dns_servers()}
 
 
 class UpdateView(workflows.WorkflowView):

openstack_dashboard/local/local_settings.py.example

@@ -271,6 +271,13 @@ OPENSTACK_NEUTRON_NETWORK = {
     'enable_vpn': True,
     'enable_fip_topology_check': True,
 
+    # Default dns servers you would like to use when a subnet is
+    # created.  This is only a default, users can still choose a different
+    # list of dns servers when creating a new subnet.
+    # The entries below are examples only, and are not appropriate for
+    # real deployments
+    # 'default_dns_nameservers': ["8.8.8.8", "8.8.4.4", "208.67.222.222"],
+
     # Neutron can be configured with a default Subnet Pool to be used for IPv4
     # subnet-allocation. Specify the label you wish to display in the Address
     # pool selector on the create subnet step if you want to use this feature.