Automatic Proxy Howto

For business laptops, moving from home to the office - proxy settings can be a pain. You can use browser plugins like "foxy proxy" - but the best solution - bar none - is automatic proxy configuration.

To get automatic proxy configuration working (at the office where proxy is required), you need a webserver (eg. apache2), a name server (eg. bind9), and a DHCP server (eg. dhcp3).

Apache2 config
* Put javascript into setProxy.pac in you webserver root directory (change it for your domains/proxy)

function FindProxyForURL(url, host)

{

if (isPlainHostName(host) ||

dnsDomainIs(host, ".yourdomain1.ca") ||

dnsDomainIs(host, ".yourdomain2.ca"))

return "DIRECT";

else return "PROXY yourproxy.yourdomain.ca:8080; DIRECT";

}

* Link wpad.dat to it (ln -s setProxy.pac wpad.dat)
* add the following to apache mime.types file (on ubuntu just /etc/mime.types):

 application/x-ns-proxy-autoconfig dat

 application/x-javascript-config pac

* restart apache  (/etc/init.d/apache2 restart)

Bind9 config
* add the following to /var/cache/bind/db.yourdomain.ca

wpad IN CNAME apachehost.yourdomain.ca.

* restart named (don't forget to change serial number) - /etc/init.d/bind9 restart

In other words, "wpad" has to resolve to your apache server... so client can "ping wpad"

DHCP config
* add the following to /etc/dhcp3/dhcpd.conf:

 option wpad code 252 = text;

 option wpad "http://apachehost.yourdomain.ca/setProxy.pac ";

 (last space is MANDATORY - IE strips last char)

* restart dhcp


That should do it!

This works with KDE 4 - w/ Google Chrome (set in KDE network settings).  And with Firefox 3.0.14 with "Automatic proxy" option selected.