at least one of them is in the monitor mode. The fix was to define the
ARP_HRD_IEEE80211_RADIOTAP 802.11 radiotap header identifier in the
libdnet-stripped code. Network interfaces that are in this mode are used
by radiotap for 802.11 frame injection and reception. The bug was
reported by Tom Eichstaedt and Henri Doreau.
http://seclists.org/nmap-dev/2012/q2/449http://seclists.org/nmap-dev/2012/q2/478
[Djalal Harouni, Henri Doreau]