sc_tx_th
sc->sc_tx_th.wt_tsf = htole64(tsf);
sc->sc_tx_th.wt_flags = sc->sc_hwmap[txrate].txflags;
sc->sc_tx_th.wt_flags |= IEEE80211_RADIOTAP_F_WEP;
sc->sc_tx_th.wt_flags |= IEEE80211_RADIOTAP_F_FRAG;
sc->sc_tx_th.wt_rate = sc->sc_hwmap[txrate].ieeerate;
sc->sc_tx_th.wt_txpower = ni->ni_txpower;
sc->sc_tx_th.wt_antenna = sc->sc_txantenna;
bpf_mtap2(sc->sc_drvbpf, &sc->sc_tx_th, sc->sc_tx_th_len, m0,
sc->sc_tx_th.wt_chan_freq = sc->sc_rx_th.wr_chan_freq =
sc->sc_tx_th.wt_chan_flags = sc->sc_rx_th.wr_chan_flags =
sizeof(struct ieee80211_frame) + sizeof(sc->sc_tx_th),
sc->sc_tx_th_len = roundup(sizeof(sc->sc_tx_th), sizeof(u_int32_t));
sc->sc_tx_th.wt_ihdr.it_len = htole16(sc->sc_tx_th_len);
sc->sc_tx_th.wt_ihdr.it_present = htole32(ATH_TX_RADIOTAP_PRESENT);