An ordinary router can use the firmware of a third party
Today, I just searched DnsMasq and saw an article called
Router DNSMasq replaces hosts and supports Android, iPhone, PC
Found that the router can swipe firmware such as dd-wrt, openwrt, etc.
Dd-wrt support list: http://www.dd-wrt.com/wiki/index.php/Supported_Devices
Openwrt support list: http://wiki.openwrt.org/toh/start
I'll keep it for a while. Next time, there will be an abandoned router to play with.