Merge lp:~mpontillo/maas/subnet-dns-override-maas-dns-for-default-gw--bug-1576116 into lp:~maas-committers/maas/trunk

[Mike Pontillo]

When deploying a node, override the MAAS DNS server with the DNS servers specified on the subnet for the default gateway, when specifying DNS servers for the loopback interface.

[Mike Pontillo (mpontillo)]

I think this is ready for review now. This branch implements the work we discussed the other day: making curtin's default DNS servers (for the loopback interface) consistent with the DNS servers on the default gateway's subnet. Previously, the DNS server was always the rack-facing MAAS IP address.

The code was relatively simple, but it was pretty gnarly to unit test all the different permutations.

[Gavin Panella (allenap)]

Looks good. A few comments but they're all minor.

review: Approve

[Mike Pontillo (mpontillo)]

Thanks for the review. Some replies below.

[MAAS Lander (maas-lander)]

The attempt to merge lp:~mpontillo/maas/subnet-dns-override-maas-dns-for-default-gw--bug-1576116 into lp:maas failed. Below is the output from the failed tests.

Hit:1 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial InRelease
Hit:2 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-updates InRelease
Hit:3 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-backports InRelease
Get:4 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]
Fetched 94.5 kB in 0s (225 kB/s)
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
    --no-install-recommends install apache2 archdetect-deb authbind bash bind9 bind9utils build-essential bzr bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools git gjs ipython isc-dhcp-common libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm postgresql pxelinux python3-all python3-apt python3-bson python3-convoy python3-crochet python3-cssselect python3-curtin python3-dev python3-distro-info python3-django python3-django-nose python3-django-piston3 python3-dnspython python3-docutils python3-formencode python3-hivex python3-httplib2 python3-jinja2 python3-jsonschema python3-lxml python3-netaddr python3-netifaces python3-novaclient python3-oauth python3-oauthlib python3-openssl python3-paramiko python3-petname python3-pexpect python3-psycopg2 python3-pyinotify python3-pyparsing python3-pyvmomi python3-requests python3-seamicroclient python3-setuptools python3-simplestreams python3-sphinx python3-tempita python3-twisted python3-txtftp python3-tz python3-yaml python3-zope.interface python-bson python-crochet python-django python-django-piston python-djorm-ext-pgarray python-formencode python-lxml python-netaddr python-netifaces python-pocket-lint python-psycopg2 python-simplejson python-tempita python-twisted python-yaml socat syslinux-common tgt ubuntu-cloudimage-keyring wget xvfb
Reading package lists...
Building dependency tree...
Reading state information...
apache2 is already the newest version (2.4.18-2ubuntu3).
archdetect-deb is already the newest version (1.117ubuntu2).
authbind is already the newest version (2.1.1+nmu1).
build-essential is already the newest version (12.1ubuntu2).
curl is already the newest version (7.47.0-1ubuntu2).
debhelper is already the newest version (9.20160115ubuntu3).
distro-info is already the newest version (0.14build1).
freeipmi-tools is already the newest version (1.4.11-1ubuntu1).
git is already the newest version (1:2.7.4-0ubuntu1).
isc-dhcp-common is already the newest version (4.3.3-5ubuntu12).
libjs-angularjs is already the newest version (1.2.28-1ubuntu2).
libjs-jquery is already the newest version (1.11.3+dfsg-4).
libjs-yui3-full is already the newest version (3.5.1-1ubuntu3).
libjs-yui3-min is already the newest version (3.5.1-1ubuntu3).
make is already the newest version (4.1-6).
postgresql is already the newest version (9.5+173).
pxelinux is already the newest version (3:6.03+dfsg-11ubuntu1).
python-django is already the newest version (1.8.7-1ubuntu5)...

[MAAS Lander (maas-lander)]

The attempt to merge lp:~mpontillo/maas/subnet-dns-override-maas-dns-for-default-gw--bug-1576116 into lp:maas failed. Below is the output from the failed tests.

Get:1 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]
Hit:2 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial InRelease
Get:3 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-updates InRelease [95.7 kB]
Hit:4 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-backports InRelease
Get:5 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [315 kB]
Get:6 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages [293 kB]
Fetched 799 kB in 0s (1,768 kB/s)
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
    --no-install-recommends install apache2 archdetect-deb authbind bash bind9 bind9utils build-essential bzr bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools git gjs ipython isc-dhcp-common libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm postgresql pxelinux python3-all python3-apt python3-bson python3-convoy python3-crochet python3-cssselect python3-curtin python3-dev python3-distro-info python3-django python3-django-nose python3-django-piston3 python3-dnspython python3-docutils python3-formencode python3-hivex python3-httplib2 python3-jinja2 python3-jsonschema python3-lxml python3-netaddr python3-netifaces python3-novaclient python3-oauth python3-oauthlib python3-openssl python3-paramiko python3-petname python3-pexpect python3-psycopg2 python3-pyinotify python3-pyparsing python3-pyvmomi python3-requests python3-seamicroclient python3-setuptools python3-simplestreams python3-sphinx python3-tempita python3-twisted python3-txtftp python3-tz python3-yaml python3-zope.interface python-bson python-crochet python-django python-django-piston python-djorm-ext-pgarray python-formencode python-lxml python-netaddr python-netifaces python-pocket-lint python-psycopg2 python-simplejson python-tempita python-twisted python-yaml socat syslinux-common tgt ubuntu-cloudimage-keyring wget xvfb
Reading package lists...
Building dependency tree...
Reading state information...
apache2 is already the newest version (2.4.18-2ubuntu3).
archdetect-deb is already the newest version (1.117ubuntu2).
authbind is already the newest version (2.1.1+nmu1).
build-essential is already the newest version (12.1ubuntu2).
curl is already the newest version (7.47.0-1ubuntu2).
debhelper is already the newest version (9.20160115ubuntu3).
distro-info is already the newest version (0.14build1).
freeipmi-tools is already the newest version (1.4.11-1ubuntu1).
git is already the newest version (1:2.7.4-0ubuntu1).
isc-dhcp-common is already the newest version (4.3.3-5ubuntu12).
libjs-angularjs is already the newest version (1.2.28-1ubuntu2).
libjs-jquery is already the newest version (1.11.3+dfsg-4).
libjs-yui3-full is already the newest version (3.5.1-1ubuntu3).
libjs-yui3-min is already the newest version (3.5.1-1u...

[MAAS Lander (maas-lander)]

The attempt to merge lp:~mpontillo/maas/subnet-dns-override-maas-dns-for-default-gw--bug-1576116 into lp:maas failed. Below is the output from the failed tests.

Hit:1 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial InRelease
Get:2 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-updates InRelease [95.7 kB]
Get:3 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]
Hit:4 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu xenial-backports InRelease
Fetched 190 kB in 0s (409 kB/s)
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
    --no-install-recommends install apache2 archdetect-deb authbind bash bind9 bind9utils build-essential bzr bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools git gjs ipython isc-dhcp-common libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm postgresql pxelinux python3-all python3-apt python3-bson python3-convoy python3-crochet python3-cssselect python3-curtin python3-dev python3-distro-info python3-django python3-django-nose python3-django-piston3 python3-dnspython python3-docutils python3-formencode python3-hivex python3-httplib2 python3-jinja2 python3-jsonschema python3-lxml python3-netaddr python3-netifaces python3-novaclient python3-oauth python3-oauthlib python3-openssl python3-paramiko python3-petname python3-pexpect python3-psycopg2 python3-pyinotify python3-pyparsing python3-pyvmomi python3-requests python3-seamicroclient python3-setuptools python3-simplestreams python3-sphinx python3-tempita python3-twisted python3-txtftp python3-tz python3-yaml python3-zope.interface python-bson python-crochet python-django python-django-piston python-djorm-ext-pgarray python-formencode python-lxml python-netaddr python-netifaces python-pocket-lint python-psycopg2 python-simplejson python-tempita python-twisted python-yaml socat syslinux-common tgt ubuntu-cloudimage-keyring wget xvfb
Reading package lists...
Building dependency tree...
Reading state information...
apache2 is already the newest version (2.4.18-2ubuntu3).
archdetect-deb is already the newest version (1.117ubuntu2).
authbind is already the newest version (2.1.1+nmu1).
build-essential is already the newest version (12.1ubuntu2).
curl is already the newest version (7.47.0-1ubuntu2).
debhelper is already the newest version (9.20160115ubuntu3).
distro-info is already the newest version (0.14build1).
freeipmi-tools is already the newest version (1.4.11-1ubuntu1).
git is already the newest version (1:2.7.4-0ubuntu1).
isc-dhcp-common is already the newest version (4.3.3-5ubuntu12).
libjs-angularjs is already the newest version (1.2.28-1ubuntu2).
libjs-jquery is already the newest version (1.11.3+dfsg-4).
libjs-yui3-full is already the newest version (3.5.1-1ubuntu3).
libjs-yui3-min is already the newest version (3.5.1-1ubuntu3).
make is already the newest version (4.1-6).
postgresql is already the newest version (9.5+173).
pxelinux is already the newest version (3:6.03+dfsg-11ubuntu1).
python-django is already the newest version (1.8.7-...

[Mike Pontillo (mpontillo)]

Strange error. Trying again...

https://paste.ubuntu.com/19438855/

=== modified file 'src/maasserver/models/node.py'
--- src/maasserver/models/node.py	2016-07-06 17:22:11 +0000
+++ src/maasserver/models/node.py	2016-07-15 00:08:33 +0000
@@ -215,8 +215,23 @@
 
 # Return type from `get_effective_power_info`.
 PowerInfo = namedtuple("PowerInfo", (
-    "can_be_started", "can_be_stopped", "can_be_queried", "power_type",
-    "power_parameters"))
+    "can_be_started",
+    "can_be_stopped",
+    "can_be_queried",
+    "power_type",
+    "power_parameters",
+))
+
+DefaultGateways = namedtuple("DefaultGateways", (
+    "ipv4",
+    "ipv6",
+))
+
+GatewayDefinition = namedtuple("GatewayDefinition", (
+    "interface_id",
+    "subnet_id",
+    "gateway_ip",
+))
 
 
 def generate_node_system_id():
@@ -2691,7 +2706,7 @@
                 interface.id
             """, (self.id,))
         return [
-            (found[0], found[1], found[2])
+            GatewayDefinition._make((found[0], found[1], found[2]))
             for found in cursor.fetchall()
         ]
 
@@ -2743,7 +2758,7 @@
 
         # Early out if we already have both gateways.
         if gateway_ipv4 and gateway_ipv6:
-            return (gateway_ipv4, gateway_ipv6)
+            return DefaultGateways._make((gateway_ipv4, gateway_ipv6))
 
         # Get the best guesses for the missing IP families.
         found_gateways = self.get_best_guess_for_default_gateways()
@@ -2753,7 +2768,47 @@
         if not gateway_ipv6:
             gateway_ipv6 = self._get_gateway_tuple_by_family(
                 found_gateways, IPADDRESS_FAMILY.IPv6)
-        return (gateway_ipv4, gateway_ipv6)
+        return DefaultGateways._make((gateway_ipv4, gateway_ipv6))
+
+    def get_default_dns_servers(self):
+        """Return the default DNS servers for this node."""
+        # Circular imports.
+        from maasserver.dns.zonegenerator import get_dns_server_address
+
+        gateways = self.get_default_gateways()
+
+        # Try first to use DNS servers from default gateway subnets.
+        if gateways.ipv4 is not None:
+            subnet = Subnet.objects.get(id=gateways.ipv4.subnet_id)
+            if subnet.dns_servers is not None and len(subnet.dns_servers) > 0:
+                # An IPv4 subnet is hosting the default gateway and has DNS
+                # servers defined. IPv4 DNS servers take first-priority.
+                return subnet.dns_servers
+        if gateways.ipv6 is not None:
+            subnet = Subnet.objects.get(id=gateways.ipv6.subnet_id)
+            if subnet.dns_servers is not None and len(subnet.dns_servers) > 0:
+                # An IPv6 subnet is hosting the default gateway and has DNS
+                # servers defined. IPv6 DNS servers take second-priority.
+                return subnet.dns_servers
+
+        # No default gateway subnet has specific DNS servers defined, so
+        # use MAAS for the default DNS server.
+        if gateways.ipv4 is None and gateways.ipv6 is None:
+            # If there are no default gateways, the default is the MAAS
+            # region IP address.
+            maas_dns_server = get_dns_server_address(
+                rack_controller=self.get_boot_rack_controller())
+        else:
+            # Choose an address consistent with the primary address-family
+            # in use, as indicated by the presence (or not) of a gateway.
+            # Note that this path is only taken if the MAAS URL is set to
+            # a hostname, and the hostname resolves to both an IPv4 and an
+            # IPv6 address.
+            maas_dns_server = get_dns_server_address(
+                rack_controller=self.get_boot_rack_controller(),
+                ipv4=(gateways.ipv4 is not None),
+                ipv6=(gateways.ipv6 is not None))
+        return [maas_dns_server]
 
     def get_boot_purpose(self):
         """

=== modified file 'src/maasserver/models/tests/test_node.py'
--- src/maasserver/models/tests/test_node.py	2016-06-30 17:03:46 +0000
+++ src/maasserver/models/tests/test_node.py	2016-07-15 00:08:33 +0000
@@ -36,6 +36,7 @@
 from maasserver.enum import (
     FILESYSTEM_GROUP_TYPE,
     FILESYSTEM_TYPE,
+    INTERFACE_LINK_TYPE,
     INTERFACE_TYPE,
     IPADDRESS_TYPE,
     NODE_PERMISSION,
@@ -93,6 +94,7 @@
     NODE_TRANSITIONS,
 )
 from maasserver.rpc.testing.fixtures import MockLiveRegionToClusterRPCFixture
+import maasserver.server_address as server_address_module
 from maasserver.storage_layouts import (
     StorageLayoutError,
     StorageLayoutMissingBootDiskError,
@@ -136,6 +138,7 @@
     commissioning,
     disk_erasing,
 )
+from netaddr import IPAddress
 from provisioningserver.events import (
     EVENT_DETAILS,
     EVENT_TYPES,
@@ -4303,6 +4306,158 @@
             ), node.get_default_gateways())
 
 
+class TestGetDefaultDNSServers(MAASServerTestCase):
+    """Tests for `Node.get_default_dns_servers`."""
+
+    def make_Node_with_RackController(
+            self, ipv4=True, ipv6=True, ipv4_gateway=True, ipv6_gateway=True,
+            ipv4_subnet_dns=None, ipv6_subnet_dns=None):
+        ipv4_subnet_dns = [] if ipv4_subnet_dns is None else ipv4_subnet_dns
+        ipv6_subnet_dns = [] if ipv6_subnet_dns is None else ipv6_subnet_dns
+        rack_v4 = None
+        rack_v6 = None
+        fabric = factory.make_Fabric()
+        vlan = fabric.get_default_vlan()
+        if ipv4:
+            gateway_ip = None if ipv4_gateway else ""
+            v4_subnet = factory.make_Subnet(
+                version=4, vlan=vlan, dns_servers=ipv4_subnet_dns,
+                gateway_ip=gateway_ip)
+        if ipv6:
+            gateway_ip = None if ipv6_gateway else ""
+            v6_subnet = factory.make_Subnet(
+                version=6, vlan=vlan, dns_servers=ipv6_subnet_dns,
+                gateway_ip=gateway_ip)
+        rack = factory.make_RegionRackController()
+        vlan.primary_rack = rack
+        vlan.dhcp_on = True
+        vlan.save()
+        # In order to determine the correct IP address per-address-family,
+        # a name lookup is performed on the hostname part of the URL.
+        # We need to mock that so we can return whatever IP addresses it
+        # resolves to.
+        rack.url = "http://region:5240/MAAS/"
+        if ipv4:
+            rack_v4 = factory.pick_ip_in_Subnet(v4_subnet)
+        if ipv6:
+            rack_v6 = factory.pick_ip_in_Subnet(v6_subnet)
+
+        def get_address(hostname, ip_version=4):
+            """Mock function to return the IP address of the rack based on the
+            given address family.
+            """
+            if ip_version == 4:
+                return {IPAddress(rack_v4)} if rack_v4 else set()
+            elif ip_version == 6:
+                return {IPAddress(rack_v6)} if rack_v6 else set()
+
+        resolve_hostname = self.patch(
+            server_address_module, 'resolve_hostname')
+        resolve_hostname.side_effect = get_address
+        rack.interface_set.all().delete()
+        rackif = factory.make_Interface(vlan=vlan, node=rack)
+        if ipv4:
+            rackif.link_subnet(INTERFACE_LINK_TYPE.STATIC, v4_subnet, rack_v4)
+        if ipv6:
+            rackif.link_subnet(INTERFACE_LINK_TYPE.STATIC, v6_subnet, rack_v6)
+        rack.boot_interface = rackif
+        rack.save()
+        node = factory.make_Node(status=NODE_STATUS.READY, disable_ipv4=False)
+        nodeif = factory.make_Interface(vlan=vlan, node=node)
+        if ipv4:
+            nodeif.link_subnet(INTERFACE_LINK_TYPE.AUTO, v4_subnet)
+        if ipv6:
+            nodeif.link_subnet(INTERFACE_LINK_TYPE.AUTO, v6_subnet)
+        node.boot_interface = nodeif
+        node.save()
+        return rack_v4, rack_v6, node
+
+    def test__uses_rack_ipv4_if_ipv4_only_with_no_gateway(self):
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=False, ipv6=False, ipv6_gateway=False)
+        self.assertThat(node.get_default_dns_servers(), Equals([rack_v4]))
+
+    def test__uses_rack_ipv4_if_ipv4_only_with_no_gateway_v4_dns(self):
+        ipv4_subnet_dns = factory.make_ip_address(ipv6=False)
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=False, ipv6=False, ipv6_gateway=False,
+            ipv4_subnet_dns=[ipv4_subnet_dns])
+        self.assertThat(
+            node.get_default_dns_servers(), Equals([rack_v4]))
+
+    def test__uses_rack_ipv6_if_ipv6_only_with_no_gateway_v6_dns(self):
+        ipv6_subnet_dns = factory.make_ip_address(ipv6=True)
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=False, ipv4_gateway=False, ipv6=True, ipv6_gateway=False,
+            ipv6_subnet_dns=[ipv6_subnet_dns])
+        self.assertThat(node.get_default_dns_servers(), Equals([rack_v6]))
+
+    def test__uses_rack_ipv4_if_dual_stack_with_no_gateway(self):
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=False, ipv6=True, ipv6_gateway=False)
+        self.assertThat(node.get_default_dns_servers(), Equals([rack_v4]))
+
+    def test__uses_rack_ipv4_if_dual_stack_with_ipv4_gateway(self):
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=True, ipv6=True, ipv6_gateway=False)
+        self.assertThat(node.get_default_dns_servers(), Equals([rack_v4]))
+
+    def test__uses_subnet_ipv4_if_dual_stack_with_ipv4_gateway_with_dns(self):
+        ipv4_subnet_dns = factory.make_ip_address(ipv6=False)
+        ipv6_subnet_dns = factory.make_ip_address(ipv6=True)
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=True, ipv6=True, ipv6_gateway=False,
+            ipv4_subnet_dns=[ipv4_subnet_dns],
+            ipv6_subnet_dns=[ipv6_subnet_dns])
+        self.assertThat(
+            node.get_default_dns_servers(), Equals([ipv4_subnet_dns]))
+
+    def test__uses_rack_ipv6_if_dual_stack_with_ipv6_gateway(self):
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=False, ipv6=True, ipv6_gateway=True)
+        self.assertThat(node.get_default_dns_servers(), Equals([rack_v6]))
+
+    def test__uses_subnet_ipv6_if_dual_stack_with_ipv6_gateway(self):
+        ipv4_subnet_dns = factory.make_ip_address(ipv6=False)
+        ipv6_subnet_dns = factory.make_ip_address(ipv6=True)
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=False, ipv6=True, ipv6_gateway=True,
+            ipv4_subnet_dns=[ipv4_subnet_dns],
+            ipv6_subnet_dns=[ipv6_subnet_dns])
+        self.assertThat(
+            node.get_default_dns_servers(), Equals([ipv6_subnet_dns]))
+
+    def test__uses_rack_ipv4_if_ipv4_with_ipv4_gateway(self):
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=True, ipv6=False, ipv6_gateway=False)
+        self.assertThat(node.get_default_dns_servers(), Equals([rack_v4]))
+
+    def test__uses_subnet_ipv4_if_ipv4_stack_with_ipv4_gateway_and_dns(self):
+        ipv4_subnet_dns = factory.make_ip_address(ipv6=False)
+        ipv6_subnet_dns = factory.make_ip_address(ipv6=True)
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=True, ipv4_gateway=True, ipv6=False, ipv6_gateway=False,
+            ipv4_subnet_dns=[ipv4_subnet_dns],
+            ipv6_subnet_dns=[ipv6_subnet_dns])
+        self.assertThat(
+            node.get_default_dns_servers(), Equals([ipv4_subnet_dns]))
+
+    def test__uses_rack_ipv6_if_ipv6_with_ipv6_gateway(self):
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=False, ipv4_gateway=False, ipv6=True, ipv6_gateway=True)
+        self.assertThat(node.get_default_dns_servers(), Equals([rack_v6]))
+
+    def test__uses_subnet_ipv6_if_ipv6_with_ipv6_gateway_and_dns(self):
+        ipv4_subnet_dns = factory.make_ip_address(ipv6=False)
+        ipv6_subnet_dns = factory.make_ip_address(ipv6=True)
+        rack_v4, rack_v6, node = self.make_Node_with_RackController(
+            ipv4=False, ipv4_gateway=False, ipv6=True, ipv6_gateway=True,
+            ipv4_subnet_dns=[ipv4_subnet_dns],
+            ipv6_subnet_dns=[ipv6_subnet_dns])
+        self.assertThat(
+            node.get_default_dns_servers(), Equals([ipv6_subnet_dns]))
+
+
 class TestNode_Start(MAASServerTestCase):
     """Tests for Node.start()."""
 

=== modified file 'src/maasserver/preseed_network.py'
--- src/maasserver/preseed_network.py	2016-03-28 13:54:47 +0000
+++ src/maasserver/preseed_network.py	2016-07-15 00:08:33 +0000
@@ -6,10 +6,7 @@
 __all__ = [
     ]
 
-from maasserver.dns.zonegenerator import (
-    get_dns_search_paths,
-    get_dns_server_address,
-)
+from maasserver.dns.zonegenerator import get_dns_search_paths
 from maasserver.enum import (
     INTERFACE_TYPE,
     IPADDRESS_FAMILY,
@@ -24,6 +21,7 @@
     def __init__(self, node):
         self.node = node
         self.gateways = node.get_default_gateways()
+        self.dns_servers = node.get_default_dns_servers()
         self.gateway_ipv4_set = False
         self.gateway_ipv6_set = False
         self.operations = {
@@ -51,8 +49,7 @@
 
         self.network_config.append({
             "type": "nameserver",
-            "address": get_dns_server_address(
-                rack_controller=self.node.get_boot_rack_controller()),
+            "address": self.dns_servers,
             "search": sorted(get_dns_search_paths()),
         })
 

=== modified file 'src/maasserver/tests/test_preseed_network.py'
--- src/maasserver/tests/test_preseed_network.py	2016-04-15 23:38:27 +0000
+++ src/maasserver/tests/test_preseed_network.py	2016-07-15 00:08:33 +0000
@@ -8,10 +8,7 @@
 import random
 from textwrap import dedent
 
-from maasserver.dns.zonegenerator import (
-    get_dns_search_paths,
-    get_dns_server_address,
-)
+from maasserver.dns.zonegenerator import get_dns_search_paths
 from maasserver.enum import (
     INTERFACE_TYPE,
     IPADDRESS_FAMILY,
@@ -203,8 +200,7 @@
 
     def collectDNSConfig(self, node):
         config = "- type: nameserver\n  address: %s\n  search:\n" % (
-            get_dns_server_address(
-                rack_controller=node.get_boot_primary_rack_controller()))
+            repr(node.get_default_dns_servers()))
         dns_searches = sorted(get_dns_search_paths())
         for dns_name in dns_searches:
             config += "   - %s\n" % dns_name