Use the rack controller IP as DNS when relaying DHCP

[David Negreira]

We encountered a situation where a VLAN is being relayed to another VLAN, and instead of the rack controller IPs set as DNS, the IP of the region controller is added as DNS. In a distributed environment, the region controller might not be routed through the VLANs that the rack servers provide IP addresses.

Below an example with the dhcpd.conf generated:

###
Base VLAN (the one being relayed to):

shared-network vlan-5001 {
subnet 10.52.132.0 netmask 255.255.255.0 {
ignore-client-uids true;
next-server 10.52.132.133;
option subnet-mask 255.255.255.0;
option broadcast-address 10.52.132.255;
option domain-name-servers 10.52.132.133;
option domain-name "maas";
option domain-search "maas";
option routers 10.52.132.1;
option ntp-servers 10.52.132.133;
...
filename "http://10.52.132.133:5248/ipxe.cfg";

Other vlans:

shared-network vlan-5002 {
subnet 10.52.140.0 netmask 255.255.255.0 {
ignore-client-uids true;
next-server 10.52.132.133;
option subnet-mask 255.255.255.0;
option broadcast-address 10.52.140.255;
option domain-name-servers 192.168.122.137;
option domain-name "maas";
option domain-search "maas";
option routers 10.52.140.1;
option ntp-servers 10.52.132.133;
...
filename "http://10.52.132.133:5248/ipxe.cfg";

shared-network vlan-5003 {
subnet 10.52.142.0 netmask 255.255.255.0 {
ignore-client-uids true;
next-server 10.52.132.133;
option subnet-mask 255.255.255.0;
option broadcast-address 10.52.142.255;
option domain-name-servers 192.168.122.137;
option domain-name "maas";
option domain-search "maas";
option routers 10.52.142.1;
option ntp-servers 10.52.132.133;
...
filename "http://10.52.132.133:5248/ipxe.cfg";
###

Observe that all options respect the vlan IP Address, except domain-name-servers.

I am working on a patch to resolve this and would like some feedback.

[Alberto Donato (ack)]

Hi, which version of MAAS are you using?

[David Negreira (dnegreira)]

Hi,

I tested this behavior and it happens on 3.1/3.2/3.3, but I believe it also happens on 3.0 and earlier versions.

[Joao Andre Simioni (jasimioni)]

Hi,

since this is affecting a production environment running 3.2.6, I'd like to request the backport of the patch to the 3.2 version.

Thanks