Cisco cards and rfmon oddities on FreeBSD.

Some months ago I looked at FreeBSD's an driver and saw that it (and
bpf, ancontrol etc.) supported rfmon mode. I don't use FreeBSD but I
pulled the relevant code and added similar functionality to OpenBSD.

This mostly identical code works well for me on OpenBSD, but I'm also
trying to support FreeBSD users on the Kismet lists/forums and it seems
FreeBSD's rfmon mode doesn't work at all well for them. I'm a little
mystified by the problems they are seeing.

Looking at the FreeBSD generated packet dumps that I've been sent two
things seem to be happening:

1) Most frames appear malformed according to ethereal. It looks like
they are either truncated or have extra bytes inserted/appended.

2) Many frames are ghosts, i.e. maybe the bssid or ssid are slightly
different. To Kismet this looks like a new network, and there are a lot
of frames like this. One network can show up as 30 or more ghost
networks due to this.

Does anyone use Cisco 802.11 cards in rfmon mode on FreeBSD, and if so,
are you seeing any problems? What might be the cause of these FreeBSD
oddities, does anyone have any ideas?

-pedro



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