802.11 monitor mode changes coming
sam at errno.com
Mon May 18 18:16:57 UTC 2009
The patch here:
has significant changes to monitor mode operation. Most importantly it
replaces DLT_IEEE802_11 support in net80211 by DLT_IEEE802_11_RADIO and
removes the latter from the underlying device. The upshot is that you
can no longer do:
tcpdump -i ath0
instead you will now need a wlanX ifnet; e.g.
ifconfig wlan create wlandev ath0 wlanmode monitor channel 6 up
tcpdump -i wlan0 -y IEEE802_11_RADIO
This addresses the longstanding issue that applications like kismet that
want radiotap data needed to open two ifnets, one to receive data and
one to do channel changes. My main concern is whether losing
DLT_IEEE802_11 support will affect any apps. Those that depend on it
should be easy to change; you just request a different DLT and strip the
radiotap header from tap'd frames (or similar).
In sweeping the drivers to do these changes I've made radiotap support
more consistent and improved some drivers. Drivers not tested so far:
malo, ipw, wpi, and upgt. I tested iwi and it appears broken in that no
frames are rx'd but I'm not sure I'll look at it before 8.0.
I plan to commit these changes by the end of the week.
More information about the freebsd-current