E Miller _ Note : Virtual State of Jefferson Tech

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Virtual State of Jefferson Tech

Apr 20 2010, 10:55PM

My collaboration with Ethan Ham, Virtual State of Jefferson will be going up in Ashland at the Schneider Museum of Art next month. I wanted to describe a little about the tech work involved because I had fun, and it might be useful to others. The piece is a router running dd-wrt with an iptables rule that sends all traffic through a proxy. The proxy server is running squid, as well as nginx. Squid is configured with a redirect_program that does the following for each request:

Skip resources that are likely not text based (images, videos, etc)
For text-based resources, grab the source and do a quick regex search for 'california', 'ca' or 'oregon'
For resources that have one of the previous, do a full regex search/replace for cities in northern California, or southern Oregon that appear next to their state name/abbreviation (resulting in "Ashland, Jefferson" instead of "Ashland, Oregon", for example)
Save the modified file on the nginx path, and transparently redirect the request to that file

The whole setup was heavily influenced by the upside-down-ternet, but since I prefer to work in Python, I used this script as my starting point. The toughest part was probably figuring out the right iptable rule to stick on the router, here is the script I ended up with:


#!/bin/sh

PROXY_IP=[proxy-ip]
PROXY_PORT=3128
LAN_IP=`nvram get lan_ipaddr`
LAN_NET=$LAN_IP/`nvram get lan_netmask`

if [ "$1" = "delete" ]; then
        ACTION=D
else
        ACTION=A
fi

cmd="iptables -t nat -$ACTION PREROUTING -s $LAN_NET -p tcp -m tcp --dport 80 -j DNAT --to-destination $PROXY_IP:$PROXY_PORT"
echo $cmd
$cmd

It's fun using sys-admin skills for an art project :D

Tags : networking nginx proxy regex

Ethan Miller

Virtual State of Jefferson Tech