#!/bin/sh

# TCP Proxy using IPTables

 

IPTABLES=/sbin/iptables

 

echo 1 > /proc/sys/net/ipv4/ip_forward

 

# Flush nat table

$IPTABLES -t nat -F

 

# tcpproxy LOCAL_IP LOCAL_PORT REMOTE_IP REMOTE_PORT

function tcpproxy {

$IPTABLES -t nat -A PREROUTING --dst $1 -p tcp --dport $2 -j DNAT --to-destination $3:$4

$IPTABLES -t nat -A POSTROUTING --dst $3 -p tcp --dport $4 -j SNAT --to-source $1

$IPTABLES -t nat -A OUTPUT --dst $1 -p tcp --dport $2 -j DNAT --to-destination $3:$4

}