Setting DNS by OpenVPN Client

I'd like to be able to set DNS on a per OpenVPN Client basis. For example, Private Internet Access has it's own DNS servers, that I only want to use when PIA is active.

I know I can go to LAN DHCP-Options and advertise them using 6,x.x.x.x,x.x.x.x, but I'm looking for something that will change them and change them back based on whether a particular OpenVPN Client is running.

OpenVPN has a client config parameter "dhcp-option dns x.x.x.x" that would be perfect, but it doesn't seem to be implemented in LEDE. Interestingly that option is available on the OpenVPN server side as a "push", but I've had reports it only works for the last DNS server you push it there's more than one.

Have you solved this issue?

No. It could probably be done using OpenVPN "up" and "down" scripts -- but I haven't pursued it any further.

The "up" script would need to set DHCP-Options 6,x.x.x.x,x.x.x.x as desired for that OpenVPN client and the "down" script would need to set it back to the original DNS servers. Untested theory at this point though!