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[20051206] Patch: an(4) radiotap for NetBSD 3.0 (Update #1)
Eric Auge has privided a patch against the an(4) driver for Aironet 4500/4800 and Cisco 340/350 series wireless network drivers in the upcoming NetBSD 3.0 release (available today on the netbsd-3 branch ans via some release candidates), allowing it to capture tcpdump(8) packets including their IEEE 802.11 headers. The patch also includes support for newer firmwares. See his mail for more information and a link to his patch.

Update #1: Eric has updated me that ``radiotap gives informations about the state of the card at the time the packet was received, the best example for that is using radiotap headers to have signal/noise informations without each time asking the card (using ioctl()).

With radiotap header the signal informations for this packet are embedded in those headers, same for channel informations, malformed packet flags, other flags or infos the card can provide directly within the driver (usually not accessible from userland) etc..''

For more data, see the ieee80211_radiotap(9) manpage (on -current, maybe 3.0 - I'm happy with 2.1 on my laptop!)

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