tproxy

Some random code that demonstrates how to properly use Netfilters tproxy target together with IP_FREEBIND, IP_TRANSPARENT and IP_ORIGDSTADDR in Linux.

Usage

1. Set your LAN subnet to 10.22.22.0/24
2. Run the iptables command present in server.php
3. Run php server.php as root

Limitations

• Currently only supports TCP. Unfortunately, UDP support cannot be added in PHP because we cannot obtain the C struct containing both the source/destination IPs and ports. This is a limitation of PHP and not Netfilter, an implementation written in C (or perhaps other languages) would be able to also implement UDP support.
• Socket lookup after each socket_select() is currently O(N^2), so don't expect great performance for thousands of simultaneous connections.