1、DNS劫持检测
iptables -L -t nat|grep domain
2、手工开启DNS劫持
iptables -t nat -I PSW -p udp --dport 53 -j REDIRECT --to-ports 53
iptables -t nat -I PSW -p tcp --dport 53 -j REDIRECT --to-ports 53
iptables -t nat -A PREROUTING -p udp --dport 53 -j REDIRECT --to-ports 53
iptables -t nat -A PREROUTING -p tcp --dport 53 -j REDIRECT --to-ports 53