ugl_packet
struct ugl_packet *ugl_buf;
if (total_len < offsetof(struct ugl_packet, pkt_data)) {
total_len = offsetof(struct ugl_packet, pkt_data[m->m_pkthdr.len]);
#define UGL_BUFSZ roundup(sizeof(struct ugl_packet), UGL_BULK_PKTLEN)