[pptp-server] Relay for PPTP server?

[tmk]

> -IP client connects from ISP to the pseudo-PPTP server, the relay.
> -Relay then forwards traffic to PPTP server to inside the firewall (relay
> knows the private route
>  to get to the real PPTP server
> -PPTP authenticates the client, looking like the client is the relay
> -The relay handles the connectivity to the real clients, yadda yadda yadda
> 
> This way, I can allow all traffic between the PPTP server and the relay.
> 
> So, I need a relay machine which can forward GRE (not so easy) and TCP
> (easy)

There IS a pptp proxy/masq module for the kernel, but i'm not sure if that
would suit your needs.. From a few logs i've seen, gre uses TCP protocol
47, and port 65535 (or 0? could be irrelevant)

Kevin