Merge lp:~ltrager/maas/lp1519918 into lp:maas/1.9

[Lee Trager]

Add migration to check for invalid ',' in the dns_servers column of the subnet table.

MAAS has accepted a space separated list of DNS servers from the user for a long time. This list is converted into a Python list and finally to a SQL array. Before 1.8 we weren't validating that the user didn't mistakenly separate entries with a comma. Thus a user giving MAAS "10.245.200.27,10.245.200.1" would result in that entire string being added to the database as one entry in the array.

This adds a new data migration which iterates through all dns_servers in the subnet table and searches for any DNS entries with a ',' in them and splits it into multiple entries.

[Blake Rouse (blake-rouse)]

Looks good.

We need to be very sure that this is validated at the API and UI. Make sure tests exists for both the API and UI, to ensure this does not happen again.

review: Approve

[Lee Trager (ltrager)]

I've modified the subnet form to use the same method the general settings use to validate multiple IP addresses. Now both accept white space or comma delimited entries. I also realized that I was missing checking the general dns_servers setting in the migration.

[Blake Rouse (blake-rouse)]

Looks good. Don't forget trunk and let me know when it lands as it will need to be included in the MAAS tarball in trunk.

review: Approve

=== modified file 'src/maasserver/forms_subnet.py'
--- src/maasserver/forms_subnet.py	2015-09-15 15:51:00 +0000
+++ src/maasserver/forms_subnet.py	2015-12-02 02:56:35 +0000
@@ -17,6 +17,7 @@
 ]
 
 from django import forms
+from maasserver.fields import IPListFormField
 from maasserver.forms import MAASModelForm
 from maasserver.models.fabric import Fabric
 from maasserver.models.space import Space
@@ -59,6 +60,7 @@
     def clean(self):
         cleaned_data = super(SubnetForm, self).clean()
         cleaned_data = self._clean_name(cleaned_data)
+        cleaned_data = self._clean_dns_servers(cleaned_data)
         if self.instance.id is None:
             # We only allow the helpers when creating. When updating we require
             # the VLAN specifically. This is because we cannot make a correct
@@ -124,3 +126,15 @@
         if space is None:
             cleaned_data["space"] = Space.objects.get_default_space()
         return cleaned_data
+
+    def _clean_dns_servers(self, cleaned_data):
+        dns_servers = cleaned_data.get("dns_servers", None)
+        if dns_servers is None:
+            return cleaned_data
+        clean_dns_servers = []
+        for dns_server in dns_servers:
+            ip_list_form = IPListFormField()
+            ip_list_cleaned = ip_list_form.clean(dns_server)
+            clean_dns_servers += ip_list_cleaned.split(" ")
+        cleaned_data["dns_servers"] = clean_dns_servers
+        return cleaned_data

=== added file 'src/maasserver/migrations/0191_remove_comma_from_dns_servers.py'
--- src/maasserver/migrations/0191_remove_comma_from_dns_servers.py	1970-01-01 00:00:00 +0000
+++ src/maasserver/migrations/0191_remove_comma_from_dns_servers.py	2015-12-02 02:56:35 +0000
@@ -0,0 +1,528 @@
+import re
+
+from django.db import models
+from south.db import db
+# -*- coding: utf-8 -*-
+from south.utils import datetime_utils as datetime
+from south.v2 import DataMigration
+
+
+class Migration(DataMigration):
+
+    def forwards(self, orm):
+        # MAAS accepts a list of DNS servers. In the CLI and UI this list is
+        # provided as a space seperated list which is then converted into a
+        # Python list and finally a SQL array. MAAS < 1.8 did not check for
+        # comma seperated lists and added them as one entry to the database.
+        for subnet in orm['maasserver.Subnet'].objects.all():
+            new_dns_servers = []
+            for dns_server in subnet.dns_servers:
+                if ',' in dns_server:
+                    for i in dns_server.split(','):
+                        if i:
+                            new_dns_servers.append(i)
+                else:
+                    new_dns_servers.append(dns_server)
+            subnet.dns_servers = new_dns_servers
+            subnet.save()
+
+        for config in orm['maasserver.Config'].objects.all():
+            if (config.name == "upstream_dns" and
+                config.value is not None and ',' in config.value):
+                # From IPListFormField
+                separators = re.compile('[,\s]+')
+                ips = re.split(separators, config.value)
+                ips = [ip.strip() for ip in ips if ip != '']
+                config.value = ' '.join(ips)
+                config.save()
+            
+
+    def backwards(self, orm):
+        # No migration needed as this just fixes misformatted data
+        return
+
+    models = {
+        u'auth.group': {
+            'Meta': {'object_name': 'Group'},
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '80'}),
+            'permissions': ('django.db.models.fields.related.ManyToManyField', [], {'to': u"orm['auth.Permission']", 'symmetrical': 'False', 'blank': 'True'})
+        },
+        u'auth.permission': {
+            'Meta': {'ordering': "(u'content_type__app_label', u'content_type__model', u'codename')", 'unique_together': "((u'content_type', u'codename'),)", 'object_name': 'Permission'},
+            'codename': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'content_type': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['contenttypes.ContentType']"}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '50'})
+        },
+        u'auth.user': {
+            'Meta': {'object_name': 'User'},
+            'date_joined': ('django.db.models.fields.DateTimeField', [], {'default': 'datetime.datetime.now'}),
+            'email': ('django.db.models.fields.EmailField', [], {'unique': 'True', 'max_length': '75', 'blank': 'True'}),
+            'first_name': ('django.db.models.fields.CharField', [], {'max_length': '30', 'blank': 'True'}),
+            'groups': ('django.db.models.fields.related.ManyToManyField', [], {'symmetrical': 'False', 'related_name': "u'user_set'", 'blank': 'True', 'to': u"orm['auth.Group']"}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'is_active': ('django.db.models.fields.BooleanField', [], {'default': 'True'}),
+            'is_staff': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'is_superuser': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'last_login': ('django.db.models.fields.DateTimeField', [], {'default': 'datetime.datetime.now'}),
+            'last_name': ('django.db.models.fields.CharField', [], {'max_length': '30', 'blank': 'True'}),
+            'password': ('django.db.models.fields.CharField', [], {'max_length': '128'}),
+            'user_permissions': ('django.db.models.fields.related.ManyToManyField', [], {'symmetrical': 'False', 'related_name': "u'user_set'", 'blank': 'True', 'to': u"orm['auth.Permission']"}),
+            'username': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '30'})
+        },
+        u'contenttypes.contenttype': {
+            'Meta': {'ordering': "('name',)", 'unique_together': "(('app_label', 'model'),)", 'object_name': 'ContentType', 'db_table': "'django_content_type'"},
+            'app_label': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'model': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '100'})
+        },
+        u'maasserver.blockdevice': {
+            'Meta': {'ordering': "[u'id']", 'unique_together': "((u'node', u'name'),)", 'object_name': 'BlockDevice'},
+            'block_size': ('django.db.models.fields.IntegerField', [], {}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'id_path': ('django.db.models.fields.FilePathField', [], {'max_length': '100', 'null': 'True', 'blank': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'node': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Node']"}),
+            'size': ('django.db.models.fields.BigIntegerField', [], {}),
+            'tags': ('djorm_pgarray.fields.ArrayField', [], {'default': '[]', u'dbtype': "u'text'", 'null': 'False', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.bootresource': {
+            'Meta': {'unique_together': "((u'name', u'architecture'),)", 'object_name': 'BootResource'},
+            'architecture': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'extra': ('maasserver.fields.JSONObjectField', [], {'default': "u''", 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'rtype': ('django.db.models.fields.IntegerField', [], {'max_length': '10'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.bootresourcefile': {
+            'Meta': {'unique_together': "((u'resource_set', u'filetype'),)", 'object_name': 'BootResourceFile'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'extra': ('maasserver.fields.JSONObjectField', [], {'default': "u''", 'blank': 'True'}),
+            'filename': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'filetype': ('django.db.models.fields.CharField', [], {'default': "u'root-tgz'", 'max_length': '20'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'largefile': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.LargeFile']"}),
+            'resource_set': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'files'", 'to': u"orm['maasserver.BootResourceSet']"}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.bootresourceset': {
+            'Meta': {'unique_together': "((u'resource', u'version'),)", 'object_name': 'BootResourceSet'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'label': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'resource': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'sets'", 'to': u"orm['maasserver.BootResource']"}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'version': ('django.db.models.fields.CharField', [], {'max_length': '255'})
+        },
+        u'maasserver.bootsource': {
+            'Meta': {'object_name': 'BootSource'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'keyring_data': ('maasserver.fields.EditableBinaryField', [], {'blank': 'True'}),
+            'keyring_filename': ('django.db.models.fields.FilePathField', [], {'max_length': '100', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'url': ('django.db.models.fields.URLField', [], {'unique': 'True', 'max_length': '200'})
+        },
+        u'maasserver.bootsourcecache': {
+            'Meta': {'object_name': 'BootSourceCache'},
+            'arch': ('django.db.models.fields.CharField', [], {'max_length': '20'}),
+            'boot_source': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.BootSource']"}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'label': ('django.db.models.fields.CharField', [], {'max_length': '20'}),
+            'os': ('django.db.models.fields.CharField', [], {'max_length': '20'}),
+            'release': ('django.db.models.fields.CharField', [], {'max_length': '20'}),
+            'subarch': ('django.db.models.fields.CharField', [], {'max_length': '20'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.bootsourceselection': {
+            'Meta': {'unique_together': "((u'boot_source', u'os', u'release'),)", 'object_name': 'BootSourceSelection'},
+            'arches': ('djorm_pgarray.fields.ArrayField', [], {'default': 'None', u'dbtype': "u'text'", 'blank': 'True'}),
+            'boot_source': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.BootSource']"}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'labels': ('djorm_pgarray.fields.ArrayField', [], {'default': 'None', u'dbtype': "u'text'", 'blank': 'True'}),
+            'os': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '20', 'blank': 'True'}),
+            'release': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '20', 'blank': 'True'}),
+            'subarches': ('djorm_pgarray.fields.ArrayField', [], {'default': 'None', u'dbtype': "u'text'", 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.cacheset': {
+            'Meta': {'object_name': 'CacheSet'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.candidatename': {
+            'Meta': {'unique_together': "((u'name', u'position'),)", 'object_name': 'CandidateName'},
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.SlugField', [], {'max_length': '50'}),
+            'position': ('django.db.models.fields.IntegerField', [], {})
+        },
+        u'maasserver.componenterror': {
+            'Meta': {'object_name': 'ComponentError'},
+            'component': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '40'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'error': ('django.db.models.fields.CharField', [], {'max_length': '1000'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.config': {
+            'Meta': {'object_name': 'Config'},
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '255'}),
+            'value': ('maasserver.fields.JSONObjectField', [], {'null': 'True'})
+        },
+        u'maasserver.downloadprogress': {
+            'Meta': {'object_name': 'DownloadProgress'},
+            'bytes_downloaded': ('django.db.models.fields.IntegerField', [], {'null': 'True', 'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'error': ('django.db.models.fields.CharField', [], {'max_length': '1000', 'blank': 'True'}),
+            'filename': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'nodegroup': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.NodeGroup']"}),
+            'size': ('django.db.models.fields.IntegerField', [], {'null': 'True', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.event': {
+            'Meta': {'object_name': 'Event', 'index_together': "((u'node', u'id'),)"},
+            'action': ('django.db.models.fields.TextField', [], {'default': "u''", 'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'description': ('django.db.models.fields.TextField', [], {'default': "u''", 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'node': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Node']"}),
+            'type': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.EventType']"}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.eventtype': {
+            'Meta': {'object_name': 'EventType'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'description': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'level': ('django.db.models.fields.IntegerField', [], {'db_index': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '255'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.fabric': {
+            'Meta': {'object_name': 'Fabric'},
+            'class_type': ('django.db.models.fields.CharField', [], {'max_length': '256', 'null': 'True', 'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '256', 'null': 'True', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.fannetwork': {
+            'Meta': {'object_name': 'FanNetwork'},
+            'bridge': ('django.db.models.fields.CharField', [], {'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'dhcp': ('django.db.models.fields.NullBooleanField', [], {'null': 'True', 'blank': 'True'}),
+            'host_reserve': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'null': 'True', 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '256'}),
+            'off': ('django.db.models.fields.NullBooleanField', [], {'default': 'False', 'null': 'True', 'blank': 'True'}),
+            'overlay': ('maasserver.fields.IPv4CIDRField', [], {'unique': 'True'}),
+            'underlay': ('maasserver.fields.IPv4CIDRField', [], {'unique': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.filestorage': {
+            'Meta': {'unique_together': "((u'filename', u'owner'),)", 'object_name': 'FileStorage'},
+            'content': ('metadataserver.fields.BinaryField', [], {'blank': 'True'}),
+            'filename': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'key': ('django.db.models.fields.CharField', [], {'default': "u'da7bf4c7-97b5-11e5-b89d-525400cf186e'", 'unique': 'True', 'max_length': '36'}),
+            'owner': ('django.db.models.fields.related.ForeignKey', [], {'default': 'None', 'to': u"orm['auth.User']", 'null': 'True', 'on_delete': 'models.PROTECT', 'blank': 'True'})
+        },
+        u'maasserver.filesystem': {
+            'Meta': {'unique_together': "((u'partition', u'acquired'), (u'block_device', u'acquired'))", 'object_name': 'Filesystem'},
+            'acquired': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'block_device': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.BlockDevice']", 'null': 'True', 'blank': 'True'}),
+            'cache_set': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "u'filesystems'", 'null': 'True', 'to': u"orm['maasserver.CacheSet']"}),
+            'create_params': ('django.db.models.fields.CharField', [], {'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'filesystem_group': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "u'filesystems'", 'null': 'True', 'to': u"orm['maasserver.FilesystemGroup']"}),
+            'fstype': ('django.db.models.fields.CharField', [], {'default': "u'ext4'", 'max_length': '20'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'label': ('django.db.models.fields.CharField', [], {'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'mount_params': ('django.db.models.fields.CharField', [], {'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'mount_point': ('django.db.models.fields.CharField', [], {'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'partition': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Partition']", 'null': 'True', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'uuid': ('django.db.models.fields.CharField', [], {'max_length': '36'})
+        },
+        u'maasserver.filesystemgroup': {
+            'Meta': {'object_name': 'FilesystemGroup'},
+            'cache_mode': ('django.db.models.fields.CharField', [], {'max_length': '20', 'null': 'True', 'blank': 'True'}),
+            'cache_set': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.CacheSet']", 'null': 'True', 'blank': 'True'}),
+            'create_params': ('django.db.models.fields.CharField', [], {'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'group_type': ('django.db.models.fields.CharField', [], {'max_length': '20'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'uuid': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '36'})
+        },
+        u'maasserver.interface': {
+            'Meta': {'ordering': "(u'created',)", 'object_name': 'Interface'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'enabled': ('django.db.models.fields.BooleanField', [], {'default': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'ip_addresses': ('django.db.models.fields.related.ManyToManyField', [], {'symmetrical': 'False', 'to': u"orm['maasserver.StaticIPAddress']", 'null': 'True', 'blank': 'True'}),
+            'ipv4_params': ('maasserver.fields.JSONObjectField', [], {'default': "u''", 'blank': 'True'}),
+            'ipv6_params': ('maasserver.fields.JSONObjectField', [], {'default': "u''", 'blank': 'True'}),
+            'mac_address': ('maasserver.fields.MACAddressField', [], {'null': 'True', 'blank': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'node': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Node']", 'null': 'True', 'blank': 'True'}),
+            'params': ('maasserver.fields.JSONObjectField', [], {'default': "u''", 'blank': 'True'}),
+            'parents': ('django.db.models.fields.related.ManyToManyField', [], {'symmetrical': 'False', 'to': u"orm['maasserver.Interface']", 'null': 'True', 'through': u"orm['maasserver.InterfaceRelationship']", 'blank': 'True'}),
+            'tags': ('djorm_pgarray.fields.ArrayField', [], {'default': '[]', u'dbtype': "u'text'", 'null': 'False', 'blank': 'True'}),
+            'type': ('django.db.models.fields.CharField', [], {'max_length': '20'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'vlan': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.VLAN']", 'on_delete': 'models.PROTECT'})
+        },
+        u'maasserver.interfacerelationship': {
+            'Meta': {'object_name': 'InterfaceRelationship'},
+            'child': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'parent_relationships'", 'to': u"orm['maasserver.Interface']"}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'parent': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'children_relationships'", 'to': u"orm['maasserver.Interface']"}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.largefile': {
+            'Meta': {'object_name': 'LargeFile'},
+            'content': ('maasserver.fields.LargeObjectField', [], {}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'sha256': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '64'}),
+            'total_size': ('django.db.models.fields.BigIntegerField', [], {}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.licensekey': {
+            'Meta': {'unique_together': "((u'osystem', u'distro_series'),)", 'object_name': 'LicenseKey'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'distro_series': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'license_key': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'osystem': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.node': {
+            'Meta': {'object_name': 'Node'},
+            'agent_name': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'architecture': ('django.db.models.fields.CharField', [], {'max_length': '31', 'null': 'True', 'blank': 'True'}),
+            'bios_boot_method': ('django.db.models.fields.CharField', [], {'max_length': '31', 'null': 'True', 'blank': 'True'}),
+            'boot_cluster_ip': ('maasserver.fields.MAASIPAddressField', [], {'default': 'None', 'max_length': '39', 'null': 'True', 'blank': 'True'}),
+            'boot_disk': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'+'", 'on_delete': 'models.SET_NULL', 'default': 'None', 'to': u"orm['maasserver.PhysicalBlockDevice']", 'blank': 'True', 'null': 'True'}),
+            'boot_interface': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'+'", 'on_delete': 'models.SET_NULL', 'default': 'None', 'to': u"orm['maasserver.Interface']", 'blank': 'True', 'null': 'True'}),
+            'boot_type': ('django.db.models.fields.CharField', [], {'default': "u'fastpath'", 'max_length': '20'}),
+            'cpu_count': ('django.db.models.fields.IntegerField', [], {'default': '0'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'disable_ipv4': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'distro_series': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '20', 'blank': 'True'}),
+            'enable_ssh': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'error': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'blank': 'True'}),
+            'error_description': ('django.db.models.fields.TextField', [], {'default': "u''", 'blank': 'True'}),
+            'gateway_link_ipv4': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'+'", 'on_delete': 'models.SET_NULL', 'default': 'None', 'to': u"orm['maasserver.StaticIPAddress']", 'blank': 'True', 'null': 'True'}),
+            'gateway_link_ipv6': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'+'", 'on_delete': 'models.SET_NULL', 'default': 'None', 'to': u"orm['maasserver.StaticIPAddress']", 'blank': 'True', 'null': 'True'}),
+            'hostname': ('django.db.models.fields.CharField', [], {'default': "u''", 'unique': 'True', 'max_length': '255', 'blank': 'True'}),
+            'hwe_kernel': ('django.db.models.fields.CharField', [], {'max_length': '31', 'null': 'True', 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'installable': ('django.db.models.fields.BooleanField', [], {'default': 'True', 'db_index': 'True'}),
+            'license_key': ('django.db.models.fields.CharField', [], {'max_length': '30', 'null': 'True', 'blank': 'True'}),
+            'memory': ('django.db.models.fields.IntegerField', [], {'default': '0'}),
+            'min_hwe_kernel': ('django.db.models.fields.CharField', [], {'max_length': '31', 'null': 'True', 'blank': 'True'}),
+            'netboot': ('django.db.models.fields.BooleanField', [], {'default': 'True'}),
+            'nodegroup': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.NodeGroup']", 'null': 'True'}),
+            'osystem': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '20', 'blank': 'True'}),
+            'owner': ('django.db.models.fields.related.ForeignKey', [], {'default': 'None', 'to': u"orm['auth.User']", 'null': 'True', 'on_delete': 'models.PROTECT', 'blank': 'True'}),
+            'parent': ('django.db.models.fields.related.ForeignKey', [], {'default': 'None', 'related_name': "u'children'", 'null': 'True', 'blank': 'True', 'to': u"orm['maasserver.Node']"}),
+            'power_parameters': ('maasserver.fields.JSONObjectField', [], {'default': "u''", 'max_length': '32768', 'blank': 'True'}),
+            'power_state': ('django.db.models.fields.CharField', [], {'default': "u'unknown'", 'max_length': '10'}),
+            'power_state_updated': ('django.db.models.fields.DateTimeField', [], {'default': 'None', 'null': 'True'}),
+            'power_type': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '10', 'blank': 'True'}),
+            'routers': ('djorm_pgarray.fields.ArrayField', [], {'default': 'None', u'dbtype': "u'macaddr'", 'blank': 'True'}),
+            'skip_networking': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'skip_storage': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'status': ('django.db.models.fields.IntegerField', [], {'default': '0', 'max_length': '10'}),
+            'swap_size': ('django.db.models.fields.BigIntegerField', [], {'default': 'None', 'null': 'True', 'blank': 'True'}),
+            'system_id': ('django.db.models.fields.CharField', [], {'default': "u'node-da7bf4c6-97b5-11e5-b89d-525400cf186e'", 'unique': 'True', 'max_length': '41'}),
+            'tags': ('django.db.models.fields.related.ManyToManyField', [], {'to': u"orm['maasserver.Tag']", 'symmetrical': 'False'}),
+            'token': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['piston.Token']", 'null': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'zone': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Zone']", 'on_delete': 'models.SET_DEFAULT'})
+        },
+        u'maasserver.nodegroup': {
+            'Meta': {'object_name': 'NodeGroup'},
+            'api_key': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '18'}),
+            'api_token': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['piston.Token']", 'unique': 'True'}),
+            'cluster_name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '100', 'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'default_disable_ipv4': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'dhcp_key': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'maas_url': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'blank': 'True'}),
+            'name': ('maasserver.models.nodegroup.DomainNameField', [], {'max_length': '80', 'blank': 'True'}),
+            'status': ('django.db.models.fields.IntegerField', [], {'default': '1'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'uuid': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '36'})
+        },
+        u'maasserver.nodegroupinterface': {
+            'Meta': {'unique_together': "((u'nodegroup', u'name'),)", 'object_name': 'NodeGroupInterface'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'foreign_dhcp_ip': ('maasserver.fields.MAASIPAddressField', [], {'default': 'None', 'max_length': '39', 'null': 'True', 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'interface': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'blank': 'True'}),
+            'ip': ('maasserver.fields.MAASIPAddressField', [], {'max_length': '39'}),
+            'ip_range_high': ('maasserver.fields.MAASIPAddressField', [], {'default': 'None', 'max_length': '39', 'null': 'True', 'blank': 'True'}),
+            'ip_range_low': ('maasserver.fields.MAASIPAddressField', [], {'default': 'None', 'max_length': '39', 'null': 'True', 'blank': 'True'}),
+            'management': ('django.db.models.fields.IntegerField', [], {'default': '0'}),
+            'name': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'blank': 'True'}),
+            'nodegroup': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.NodeGroup']"}),
+            'static_ip_range_high': ('maasserver.fields.MAASIPAddressField', [], {'default': 'None', 'max_length': '39', 'null': 'True', 'blank': 'True'}),
+            'static_ip_range_low': ('maasserver.fields.MAASIPAddressField', [], {'default': 'None', 'max_length': '39', 'null': 'True', 'blank': 'True'}),
+            'subnet': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Subnet']", 'null': 'True', 'on_delete': 'models.PROTECT', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'vlan': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.VLAN']", 'on_delete': 'models.PROTECT'})
+        },
+        u'maasserver.partition': {
+            'Meta': {'object_name': 'Partition'},
+            'bootable': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'partition_table': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'partitions'", 'to': u"orm['maasserver.PartitionTable']"}),
+            'size': ('django.db.models.fields.BigIntegerField', [], {}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'uuid': ('django.db.models.fields.CharField', [], {'max_length': '36', 'unique': 'True', 'null': 'True', 'blank': 'True'})
+        },
+        u'maasserver.partitiontable': {
+            'Meta': {'object_name': 'PartitionTable'},
+            'block_device': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.BlockDevice']"}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'table_type': ('django.db.models.fields.CharField', [], {'default': 'None', 'max_length': '20'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.physicalblockdevice': {
+            'Meta': {'ordering': "[u'id']", 'object_name': 'PhysicalBlockDevice', '_ormbases': [u'maasserver.BlockDevice']},
+            u'blockdevice_ptr': ('django.db.models.fields.related.OneToOneField', [], {'to': u"orm['maasserver.BlockDevice']", 'unique': 'True', 'primary_key': 'True'}),
+            'model': ('django.db.models.fields.CharField', [], {'max_length': '255', 'blank': 'True'}),
+            'serial': ('django.db.models.fields.CharField', [], {'max_length': '255', 'blank': 'True'})
+        },
+        u'maasserver.space': {
+            'Meta': {'object_name': 'Space'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '256', 'null': 'True', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.sshkey': {
+            'Meta': {'unique_together': "((u'user', u'key'),)", 'object_name': 'SSHKey'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'key': ('django.db.models.fields.TextField', [], {}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['auth.User']"})
+        },
+        u'maasserver.sslkey': {
+            'Meta': {'unique_together': "((u'user', u'key'),)", 'object_name': 'SSLKey'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'key': ('django.db.models.fields.TextField', [], {}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['auth.User']"})
+        },
+        u'maasserver.staticipaddress': {
+            'Meta': {'object_name': 'StaticIPAddress'},
+            'alloc_type': ('django.db.models.fields.IntegerField', [], {'default': '0'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'hostname': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'ip': ('maasserver.fields.MAASIPAddressField', [], {'default': 'None', 'max_length': '39', 'unique': 'True', 'null': 'True', 'blank': 'True'}),
+            'subnet': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Subnet']", 'null': 'True', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'default': 'None', 'to': u"orm['auth.User']", 'null': 'True', 'on_delete': 'models.PROTECT', 'blank': 'True'})
+        },
+        u'maasserver.subnet': {
+            'Meta': {'unique_together': "((u'name', u'space'),)", 'object_name': 'Subnet'},
+            'cidr': ('maasserver.fields.CIDRField', [], {'unique': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'dns_servers': ('djorm_pgarray.fields.ArrayField', [], {'default': '[]', u'dbtype': "u'text'", 'blank': 'True'}),
+            'gateway_ip': ('maasserver.fields.MAASIPAddressField', [], {'max_length': '39', 'null': 'True', 'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'space': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Space']", 'on_delete': 'models.PROTECT'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'vlan': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.VLAN']", 'on_delete': 'models.PROTECT'})
+        },
+        u'maasserver.tag': {
+            'Meta': {'object_name': 'Tag'},
+            'comment': ('django.db.models.fields.TextField', [], {'blank': 'True'}),
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'definition': ('django.db.models.fields.TextField', [], {'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'kernel_opts': ('django.db.models.fields.TextField', [], {'null': 'True', 'blank': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '256'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'maasserver.userprofile': {
+            'Meta': {'object_name': 'UserProfile'},
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'user': ('django.db.models.fields.related.OneToOneField', [], {'to': u"orm['auth.User']", 'unique': 'True'})
+        },
+        u'maasserver.virtualblockdevice': {
+            'Meta': {'ordering': "[u'id']", 'object_name': 'VirtualBlockDevice', '_ormbases': [u'maasserver.BlockDevice']},
+            u'blockdevice_ptr': ('django.db.models.fields.related.OneToOneField', [], {'to': u"orm['maasserver.BlockDevice']", 'unique': 'True', 'primary_key': 'True'}),
+            'filesystem_group': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'virtual_devices'", 'to': u"orm['maasserver.FilesystemGroup']"}),
+            'uuid': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '36'})
+        },
+        u'maasserver.vlan': {
+            'Meta': {'unique_together': "((u'vid', u'fabric'),)", 'object_name': 'VLAN'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'fabric': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['maasserver.Fabric']"}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'mtu': ('django.db.models.fields.IntegerField', [], {'default': '1500'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '256', 'null': 'True', 'blank': 'True'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {}),
+            'vid': ('django.db.models.fields.IntegerField', [], {})
+        },
+        u'maasserver.zone': {
+            'Meta': {'ordering': "[u'name']", 'object_name': 'Zone'},
+            'created': ('django.db.models.fields.DateTimeField', [], {}),
+            'description': ('django.db.models.fields.TextField', [], {'blank': 'True'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '256'}),
+            'updated': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        u'piston.consumer': {
+            'Meta': {'object_name': 'Consumer'},
+            'description': ('django.db.models.fields.TextField', [], {}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'key': ('django.db.models.fields.CharField', [], {'max_length': '18'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '255'}),
+            'secret': ('django.db.models.fields.CharField', [], {'max_length': '32'}),
+            'status': ('django.db.models.fields.CharField', [], {'default': "'pending'", 'max_length': '16'}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "'consumers'", 'null': 'True', 'to': u"orm['auth.User']"})
+        },
+        u'piston.token': {
+            'Meta': {'object_name': 'Token'},
+            'callback': ('django.db.models.fields.CharField', [], {'max_length': '255', 'null': 'True', 'blank': 'True'}),
+            'callback_confirmed': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'consumer': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['piston.Consumer']"}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'is_approved': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'key': ('django.db.models.fields.CharField', [], {'max_length': '18'}),
+            'secret': ('django.db.models.fields.CharField', [], {'max_length': '32'}),
+            'timestamp': ('django.db.models.fields.IntegerField', [], {'default': '1448924301'}),
+            'token_type': ('django.db.models.fields.IntegerField', [], {}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "'tokens'", 'null': 'True', 'to': u"orm['auth.User']"}),
+            'verifier': ('django.db.models.fields.CharField', [], {'max_length': '10'})
+        }
+    }
+
+    complete_apps = ['maasserver']
+    symmetrical = True

=== modified file 'src/maasserver/tests/test_forms_subnet.py'
--- src/maasserver/tests/test_forms_subnet.py	2015-09-15 15:51:00 +0000
+++ src/maasserver/tests/test_forms_subnet.py	2015-12-02 02:56:35 +0000
@@ -14,6 +14,8 @@
 __metaclass__ = type
 __all__ = []
 
+import random
+
 from maasserver.forms_subnet import SubnetForm
 from maasserver.models.fabric import Fabric
 from maasserver.models.space import Space
@@ -277,3 +279,29 @@
         self.assertThat(
             subnet, MatchesStructure.byEquality(
                 gateway_ip=None, dns_servers=[]))
+
+    def test__clean_dns_servers_accepts_comma_separated_list(self):
+        subnet = factory.make_Subnet()
+        dns_servers = [factory.make_ip_address()
+                       for _ in range(random.randint(2, 10))]
+        form = SubnetForm(instance=subnet, data={
+            "dns_servers": ','.join(dns_servers)
+        })
+        self.assertTrue(form.is_valid(), form.errors)
+        form.save()
+        subnet = reload_object(subnet)
+        self.assertEquals(dns_servers,
+                          subnet.dns_servers)
+
+    def test__clean_dns_servers_accepts_space_separated_list(self):
+        subnet = factory.make_Subnet()
+        dns_servers = [factory.make_ip_address()
+                       for _ in range(random.randint(2, 10))]
+        form = SubnetForm(instance=subnet, data={
+            "dns_servers": " ".join(dns_servers)
+        })
+        self.assertTrue(form.is_valid(), form.errors)
+        form.save()
+        subnet = reload_object(subnet)
+        self.assertEquals(dns_servers,
+                          subnet.dns_servers)