If you are running VPN on port 80, because port 80 is commonly crawled for attempts to find public webservers, I would highly recommend and iptables firewall rule only allowing access from the specific IP your VPN client is connecting from.
Routing and Bridging Firewall Solutions
If you are running VPN on port 80, because port 80 is commonly crawled for attempts to find public webservers, I would highly recommend and iptables firewall rule only allowing access from the specific IP your VPN client is connecting from.