ncm_dptab16
struct ncm_dptab16 *ptr;
ptr = (struct ncm_dptab16 *)(buf + ndp_index);
offsetof(struct ncm_dptab16, datagram))/sizeof(ptr->datagram[0]);
struct ncm_dptab16 *ptr;
ptr = (struct ncm_dptab16 *)(hdr + 1);