Re: [71attendees] ietf71 wireless problems

Jeffrey Hutzelman <jhutz@cmu.edu> Tue, 11 March 2008 14:54 UTC

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Date: Tue, 11 Mar 2008 10:47:38 -0400
From: Jeffrey Hutzelman <jhutz@cmu.edu>
To: Michael Richardson <mcr@xelerance.com>, 71attendees@ietf.org
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Subject: Re: [71attendees] ietf71 wireless problems
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--On Monday, March 10, 2008 10:56:00 AM -0400 Michael Richardson 
<mcr@xelerance.com> wrote:

> I've never had problems with wireless, and I'm pretty kernel competent,
> and the same cards were last used 2008-03-06.   I'm running debian
> "GNU/Linux" etch with a custom 2.6.20.6 kernel.  I suspect that my cards
> might need firmware upgrades to deal with some new-fangled mechanism, but
> I am ignorant of what that might be.

It is worth noting that the Linux wireless extensions provide for at most 
64K-1 bytes of data in scan results (the length field is a 16-bit integer). 
In the breakfast room around the time you were having this problem, the 
scan data for the number of AP's visible was larger than 32K.  So if you 
have an application which starts with a 4K buffer and then doubles it, as 
NetworkManager does, then it ends up discovering 32K is not big enough, and 
doubling it to.... zero!  A patched NM which instead jumps from 32K to 
64K-1 (the maximum size) is able to collect scan results and connect to the 
network.


Note that this is in addition to other issues which have been discussed on 
this thread, some of which have been resolved since Sunday.

-- Jeff
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