BSD Packet Filter (BPF) lies in the kernel of BSD Unix, it is independent of the TCP/IP stack, and gives user mode processes a raw interface to access data link layer, it has been widely used in network monitors and other softwares, such as tcpdump.

• BSD包过滤器(BSD Packet Filter，简称BPF)位于BSD Unix的内核中，它独立于TCP/IP协议栈，为应用程序访问数据链路层提供了一个原始接口，被广泛地运用在网络监控及其它软件中，如tcpdump。