Re: Port Forwarding Over a Site To Site VPN Tunnel.
It's not a port forwarding problem but a routing one. The Port forwarding itself has nothing different from the server located at Site B. But if those server accessing sources are anywhere on the internet, you have to have the default route at Site A into the tunnel to get back to Site B, which affect to all other devices Site A.
If the source IPs are limited and known, you can set specific routes back into the tunnel for those without changing the default route at Site A.