Re: How to perform a Wireless Scan?

[Jean Tourrilhes <jt@bougret.hpl.hp.com>]

On Wed, Nov 24, 2004 at 08:27:13PM +0100, Matthias-Christian Ott wrote:
> Jean Tourrilhes wrote:
> 
> >Matthias-Christian Ott wrote :
> > 
> >
> >>I'm currently developing the the wireless functions for the rtl8180
> >>chipset.
> >>There's only one problem:
> >>I don't know how to perform a wireless scan.
> >>How does it work?
> >>Is there an algorithm or a GPL based driver which does this well?
> >>   
> >>
> >
> >	Most modern wireless drivers support the scan function (airo,
> >hostap, orinoco v15, prism54, atmel_cs, wl3501, madwifi, ipw2x00,
> >acx100, poldhu, at76c503, adm8211... - check my Howto).
> >	Unfortunately, the implementation is highly dependant on the
> >hardware itself, and each hardware has it's own way. Chipset which are
> >"softer" require more work. A good example of harder MAC is
> >airo/orinoco, for softer MAC check madwifi.
> >	Good luck...
> >
> >	Jean
> >
> >-
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> > 
> >
> Hi Jean!
> Let me understand scan algorithm:
> The card looks on different frequencies and channels for packages and 
> extracts the mac of the access point?
> Or am I wrong?

	Some card do the scan automatically in firmware. You just need
to say "perform the scan", and after a while it will return some
results. Other card don't have support for it, so you need to go on
each frequency, send a probe request and look at the beacons.
	A helpful hint : scanning is done for the initial association
of the card to the BSSID. If the card perform all the association by
itself (just give an ESSID), it usually has an interface to perform
scanning. If you have to write the code to perform all the association
in the driver, then you can reuse that code to implement scanning.

> Thanks
> Matthias-Christian Ott

	Good luck...

	Jean