tpacket_auxdata
struct tpacket_auxdata aux;
struct tpacket_auxdata *aux = NULL;
if (cm->cmsg_len != CMSG_LEN(sizeof(struct tpacket_auxdata)))
cm->cmsg_len, CMSG_LEN(sizeof(struct tpacket_auxdata)));
char ctrl[CMSG_SPACE(sizeof(struct tpacket_auxdata))];