Ethereal-users: Re: [Ethereal-users] Found Ethernet headers in a wireless NIC card.

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From: Guy Harris <gharris@xxxxxxxxx>
Date: Wed, 30 Mar 2005 23:17:31 -0800
Mahesh Krishnan wrote:


But when I used ethereal to sniff the card It was actually reporting Ethernet
headers and not 802.11 headers. One can understand if there was neither 802.11
or ethernet headers because the card is not in monitor mode.
Eh? If the card's not in monitor mode, at least on Linux one should, in general, expect Ethernet headers, not "neither 802.11 nor Ethernet headers" - 802.11 adapters and drivers tend to pretend (except on {Free,Net}BSD) that they're Ethernet adapters, and tend to supply Ethernet headers, unless you're in monitor mode. (On newer FreeBSD and NetBSD, a driver can specify more than one link-layer header type that it can supply, and an application can specify which one of those it wants; newer versions of libpcap have APIs to get the list of link-layer header types and select a header type, and Ethereal uses that - you select the header type from the option menu in the "Capture Options" dialog box. Perhaps Linux should consider adopting this model....) 


Is this a bug in ethereal.


No.  It's a characteristic of Linux 802.11 drivers.