Route traffic only for the domain I own

[summersab]

I have a publicly available website, and I would like to give users the option of connecting to my site over a VPN for enhanced security. However, since my site provides a free service, I don't want to route all user traffic through my VPN - only requests to my domain. To make it easy for users, the VPN would not need any authentication. My site already requires authentication, so bad actors wouldn't be able to do much if they connected to my VPN.

By way of example, say I was the owner of https://foo.com. I have other subdomains such as accounts.foo.com, email.foo.com, and forums.foo.com. All of them are behind a reverse proxy, and all systems are on a 192.168.0.0/24 network. I want external users to be able to connect to my VPN and have all traffic for *.foo.com routed over my VPN while all other traffic will be sent over their own internet connection.

Is this possible with OpenVPN? I have a feeling I would need to set up a DNS server or use the `push dhcp-option` directive.

Thank you!