bf_frmlen
bf->bf_frmlen = pktlen;
pktlen = bf_isaggr(bf) ? bf->bf_al : bf->bf_frmlen;
al_delta = ATH_AGGR_DELIM_SZ + bf->bf_frmlen;
arn_compute_num_delims(sc, tid, bf_first, bf->bf_frmlen);