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Revision as of 02:15, 9 February 2006

You are here: Main Page/DD-WRT Docu (EN)/Squid Transparent Proxy

Introduction

Running a transparent proxy server on your network can be used for more advanced content filtering of web pages for environments such as a school or library (where in some locales, filtering is required by law) or as a way to protect children in the household.

This guide will help you enable a transparent proxy server on your network by having your WRT54G router forward all traffic to the proxy server automatically

Desktop Setup

First install Squid on your unix box after that you have to set up squid to do transparent proxying with these settings

httpd_accel_host virtual
httpd_accel_port 80

httpd_accel_with_proxy on

httpd_accel_uses_host_header on

Router Setup

You will need to use iptables to tell your router how to forward traffic. If you don't have a good grasp on iptables yet, someone has already done the work and written a shellscript to do the work for you. Be sure to edit the variables at the top.

The script can be found at: http://forum.bsr-clan.de/viewtopic.php?p=10177#10177

#!/bin/sh
INTERNAL_NETWORK="192.168.0.0/24"
ROUTER_IP="192.168.0.1"
PROXY_SERVER="192.168.0.10"
PROXY_PORT="3128"
if [ -z $TRANSPARENT_PROXY ]; then
  /usr/sbin/iptables -t nat -A PREROUTING -i br0 -s $INTERNAL_NETWORK \
    -d $INTERNAL_NETWORK -p tcp --dport 80 -j ACCEPT
  /usr/sbin/iptables -t nat -A PREROUTING -i br0 -s ! $PROXY_SERVER -p tcp --dport 80 \
    -j DNAT --to $PROXY_SERVER:$PROXY_PORT
  /usr/sbin/iptables -t nat -A POSTROUTING -o br0 -s $INTERNAL_NETWORK -p tcp -d \
    $PROXY_SERVER -j SNAT --to $ROUTER_IP
  /usr/sbin/iptables -t filter -I FORWARD -s $INTERNAL_NETWORK -d $PROXY_SERVER -i br0 \
    -o br0 -p tcp --dport $PROXY_PORT -j ACCEPT
  export TRANSPARENT_PROXY="1"
else
  echo "This script has already run!"
  echo "If it hasn't, unset \$TRANSPARENT_PROXY manually via the shell."
fi

You'll need to have the script run every time the router boots. An easy way to do is to set as in the rc_firewall variable. From either Telnet/SSH_and_the_Command_Line

# nvram set rc_firewall="
PASTE
EDITED 
SCRIPT
HERE
"

You can confirm that the changes were made by executing

1. nvram get rc_firewall

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