From: Guy Harris <guy-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org>
To: radiotap-eZodSLrBbDpBDgjK7y7TUQ@public.gmane.org
Subject: Re: BPF code generation for radiotap
Date: Fri, 11 May 2007 16:49:56 -0700 [thread overview]
Message-ID: <46450124.1010809@alum.mit.edu> (raw)
In-Reply-To: <20070511231511.GB20770-eZ+MEZF6i8Dc+919tysfdA@public.gmane.org>
David Young wrote:
> Can I help someone with BPF know-how to write a radiotap code generator?
> It would be great if we could use BPF to filter out packets with, say,
> an RSSI below a certain threshold.
That will be possible only if the RSSI can be found without a loop, or
if you're willing to have all the filtering done in userland. The
kernel BPF interpreter doesn't support backwards branches; the userland
one does, to support chasing IPv6 protocol headers, but backward
branches completely screw up the optimizer (so it gets turned off).
next prev parent reply other threads:[~2007-05-11 23:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-11 23:15 BPF code generation for radiotap David Young
[not found] ` <20070511231511.GB20770-eZ+MEZF6i8Dc+919tysfdA@public.gmane.org>
2007-05-11 23:49 ` Guy Harris [this message]
[not found] ` <46450124.1010809-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org>
2007-05-11 23:52 ` David Young
[not found] ` <20070511235204.GC20770-eZ+MEZF6i8Dc+919tysfdA@public.gmane.org>
2007-05-12 1:50 ` Guy Harris
[not found] ` <46451D83.2070003-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org>
2007-05-12 1:53 ` David Young
2007-08-13 6:34 ` Johannes Berg
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