IPv6

IPv6 adresses are used more and more often. It would be great if this plugin could deal with them. For now, the plugin gives warnings with IPv6 on both backend and frontend.

To validate if you are facing with IPv4, you could use :
filter_var($this->get_user_ip(), FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)

Also, there are tips (see StackOverflow) to convert IPv6 to IPv4.