Subject: Re: issues with 802.11 radiotap
To: Matthias Drochner <>
From: David Young <>
List: tech-net
Date: 07/12/2005 16:26:49
On Tue, Jul 12, 2005 at 09:38:14PM +0200, Matthias Drochner wrote:
> said:
> > As I say, there are rules.  On any given radio, there are only two
> > structs, one for tx, one for rx. 
> Actually, the structs for ral/ural were broken, the 16-bit
> "channel" stuff was misaligned.
> > If ethereal really counts bytes, w/o considering alignment, then they
> > seriously botched their implementation, and you should file a PR against
> > ethereal.
> I'm currently testing a patch which fixes the alignment
> problems.
> There is still the FCS problem, and the dissector displays
> nonsense for other fields (eg "preamble" and "channel type"),
> but at least it can distinguish the header fields now.
> > I am going to check in some changes to the manual page shortly
> Imho it is still not obvious that each element of the radiotap
> header needs to be aligned at its individual natural boundary.
> And if you explicitely recommend to use "packed" structures you
> should state that padding bytes need to be inserted manually.

I will update the manual page to use suitably strong language about
natural alignment.  I will also send a PR to ethereal, because they
really *do* have it wrong.


David Young             OJC Technologies      Urbana, IL * (217) 278-3933