接收4个IOCTL设备控制代码，作用分别是开始过滤、停止过滤、添加过滤规则和清除过滤规则。其中每一个过滤规则由一个自定义的CIPFilter结构描述，指定了如何对待特定的IP封包。过滤钩子处理封包时，要比较每个用户添加的规则，然后采取相应的行动。-4 receive IOCTL device control code, the role is the beginning of filtration, filtering to stop, add the filter rules and clear the filtering rules. Each of these filtering rules defined by a self-described CIPFilter structure, specify how to treat a particular IP packet. Hook to deal with packet filtering, it is necessary to compare the rules for each user, and then act accordingly.