Sniffing GPRS

Sylvain Munaut 246tnt at gmail.com
Fri Feb 17 10:50:25 UTC 2012


Hi,

> I'm still not able to sniff enough data to reconstruct TCP sessions.
> I can get datagrams (even TCP), but they look like "sparse" datagrams. Even
> using 2 sniffing phones I have a slightly better result, but not enough to
> consider it satisfying.
> Are there some other steps that can be done?

Sure ... debug the issue, fix it, submit a patch. You'll probably need
deep knowledge of GPRS RLC/MAC layers to do that properly.

> Is there anyone, other that gprs decoder authors, able to make it completely
> working?

I'm not even sure they do.

The code is more of a "demo" than a complete system, a lot is missing
to properly decode everything (for, it just "guesses" the GPRS channel
from a single assignement and then listen on all timeslot of that,
which mostly a short cut to grab stuff, proving it's possible but not
that much more, unless the cell has only 1 GPRS arfcn).

Also since it only support GPRS and not EDGE you can pretty easily
miss stuff ...

Cheers,

    Sylvain




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