如何使用libpcap解析以太网数据包？

rc = pcap_next_ex((pcap_t*)handle, &header, (const unsigned char**)packet);

got_packet(u_char *args, const struct pcap_pkthdr *header, const u_char *packet);

*packet

ethernet = (struct sniff_ethernet*)(packet);

ip = (struct sniff_ip*)(packet + SIZE_ETHERNET);