When connecting to a VPN, It would be nice to have the option of de-activating the current DNS providers and use only those either pushed by the VPN server or set in the VPN client config.


Eg:
I am connected to an untrusted WiFi and get a DHCP DNS of 192.168.0.1.
I then connect to my VPN server which specifies DNS server 8.8.8.8.

At this point my resolv.conf has the following entries:
nameserver 8.8.8.8
nameserver 192.168.0.1

The current behaviour is to add add nameservers to the beginning of the list in the resolv.conf file.

This means that while on a VPN, DNS queries may be made to a local DNS server, and lead to a leaky DNS.

I suggest to add an option to the VPN configuration where a user can opt to purge local DNS settings when connected to the VPN.

This would work as:

On connect:
if use_VPN_DNS then
  save local DNS
  clear DNS settings
  add VPN specific DNS (either configured by the client VPN dialogue or the server)
end if

On Disconnect
if use_VPN_DNS then
  clear DNS settings
  reload DNS from saved value
  remove saved DNS
end if