From f3d7dd53e03292d73cbc195a13359a74b73f8bc9 Mon Sep 17 00:00:00 2001
From: Victor Tapia <victor.tapia@canonical.com>
Date: Thu, 4 Jun 2020 12:37:15 +0200
Subject: [PATCH] Use rack and not region IP addresses for DNS when possible


diff --git a/src/maasserver/dhcp.py b/src/maasserver/dhcp.py
index d9b9299b0..f73d47736 100644
--- a/src/maasserver/dhcp.py
+++ b/src/maasserver/dhcp.py
@@ -571,14 +571,9 @@ def get_default_dns_servers(rack_controller, subnet, use_rack_proxy=True):
         dns_servers = None
 
     if use_rack_proxy:
-        # Add the IP address for the rack controllers on the subnet before the
-        # region DNS servers.
+        # Add the IP address for the rack controllers on the subnet if possible
         rack_ips = get_dns_server_addresses_for_rack(rack_controller, subnet)
-        if dns_servers:
-            dns_servers = rack_ips + [
-                server for server in dns_servers if server not in rack_ips
-            ]
-        elif rack_ips:
+        if rack_ips:
             dns_servers = rack_ips
 
     return dns_servers
diff --git a/src/maasserver/preseed_network.py b/src/maasserver/preseed_network.py
index fedabded5..a7e170d30 100644
--- a/src/maasserver/preseed_network.py
+++ b/src/maasserver/preseed_network.py
@@ -29,6 +29,7 @@ from provisioningserver.utils.netplan import (
     get_netplan_bridge_parameters,
 )
 from provisioningserver.utils.network import get_source_address
+from maasserver.dhcp import get_dns_server_addresses_for_rack
 
 
 def _is_link_up(addresses):
@@ -354,12 +355,17 @@ class InterfaceConfiguration:
                         }:
                             if rack is None:
                                 continue
-                            for ip in get_dns_server_addresses(
+                            dns_servers = get_dns_server_addresses(
                                 rack_controller=rack,
                                 ipv4=(subnet.get_ip_version() == 4),
                                 ipv6=(subnet.get_ip_version() == 6),
                                 include_alternates=True,
-                            ):
+                            )
+                            rack_ips = get_dns_server_addresses_for_rack(rack, subnet)
+                            if rack_ips:
+                                # Prefer rack IPs for DNS if possible
+                                dns_servers = rack_ips
+                            for ip in dns_servers:
                                 if ip.is_loopback():
                                     continue
                                 ip_str = str(ip)
-- 
2.17.1