Enable Web Proxy Auto-discovery on OpenWrt with Dnsmasq

Recently, I set up shaodowsocks and polipo on an OpenWrt router. I'd like every client connected be able to bypass the Great Fire Wall of China automatically. This can be done by pushing an proxy auto-config to the client. And there exists a protocol called Web Proxy Autodiscovery (WPAD).

Dnsmasq is capable of WPAD. Just add this line in /etc/config/dhcp.conf under config dhcp lan section

list dhcp_option '252,http://192.168.10.1:8000/proxy.pac'

the HTTP URL should be replaced adequately. There should be no spaces between the comma and URL. You can convert GFWlist to a PAC file with gfwlist2pac.

A note for iPad users:

iPad do not enable WPAD by default (because WPAD can redirect a client's HTTP connection without informing the user). The user can enable it in the configuration for wireless access points.