Citrix has such a thing as Mac based forwarding. This is when the packet from the backend does not go along the route, but to the interface from which the request came. I am looking for the same solution.
Situation: there is a default route to the provider and there is openvpn. From openvpn, I do not accept its route and policy based routing is configured. Everything is fine, the router is accessible from the outside. But the devices for which forwarding inside the local network is configured respond and .. according to the PBR, the packets go into the tunnel. And it would be desirable to answer in the external interface.
Is there any solution? IPtables, package labeling?