tcpdump to filter wlan frame type/subtype
Following patch makes tcpdump filter 802.11 frames based on
type/subtype. You can now:
tcpdump -ni wlan_iface wlan subtype assoc-req
to grab association requests, instead of searching them in piles of
beacons. The patched tcpdump man page will show you more details
about the type/subtype syntax.
Please review it. If no objection comes, I will commit it one week later.