iptables -t mangle -A PREROUTING -s xxx -j ACCEPT
iptables -t mangle -A PREROUTING -s yyy -j ACCEPT
iptables -t mangle -P PREROUTING DROP
iptables -F -t mangle
the stupid steps make myself and all visitors lockout from fvnbox which hosts feuvan.net and some services.
Apologies to http://chaoswar.feuvan.net / zzxy.feuvan.net users!