ATU_TX_HDRLEN
m_copydata(m, 0, m->m_pkthdr.len, c->atu_buf + ATU_TX_HDRLEN);
memset(h, 0, ATU_TX_HDRLEN);
len += ATU_TX_HDRLEN;
#define ATU_TX_BUFSZ (ATU_TX_HDRLEN + \