I want to create an openvpn service on a dedicated server I have, for some friends so that they are able to play online games faster.

Is there an easy way to restrict which traffic I allow them with iptables ? It seems iptable is not very easy to maintain and we can easily get kicked out of our own server. Rebooting on a rescue mode every time I would get kicked out because of bad iptable rules would just be a pain.

As far as I understand, the tun interface would be providing the access. Which kind of rule in iptables would I have to implement to restrict their access to only 1 ip ? Also, I don't want this vpn to be the default gateway for all the traffic. I guess I should go with the option of pushing a route to the clients so that they connect to the IP of the game server through the VPN and use their regular routes through their ISP for all the other traffic ?

As a side not, it seems Openvpn AS is not very robust. Is there some other (commercial is ok) product that would give me the same administration options through a web interface ? Is Webmin the only other solution ?

Thanks !