ETHERNET_HEADER_SIZE
#define UDP_TOTAL_HEADER_SIZE (ETHERNET_HEADER_SIZE + IP_HEADER_SIZE + UDP_HEADER_SIZE)
#define TCP_TOTAL_HEADER_SIZE (ETHERNET_HEADER_SIZE + IP_HEADER_SIZE + TCP_HEADER_SIZE)
u_char header[ETHERNET_HEADER_SIZE];
u_char header[ETHERNET_HEADER_SIZE];