an_write_bap
static int an_write_bap(struct an_softc *, int, int, void *, int);
error = an_write_bap(sc, rid, 0, &len, sizeof(len));
error = an_write_bap(sc, rid, sizeof(len), buf, buflen);
if (an_write_bap(sc, fid, 0, &frmhdr, sizeof(frmhdr)) != 0)
an_write_bap(sc, fid, -1, &frmhdr, AN_TXGAP_802_11);