if_gettransmitfn
if (if_gettransmitfn(ifp) != ieee80211_vap_transmit ||
na->if_transmit = if_gettransmitfn(ifp);
na->if_transmit = if_gettransmitfn(ifp);
if_transmit_fn_t if_gettransmitfn(if_t ifp);