MDL-Error in case of OsmocomBB+OpenBTS

Pavel Baturko pabftk at
Tue Jan 8 13:02:18 UTC 2013

Thanks for explanations and fast fix! It seems that now all works as should


On Tue, Jan 8, 2013 at 12:58 PM, Sylvain Munaut <246tnt at> wrote:

> The fix Andreas just pushed is what I suspected: A missing 'return'
> that made the "ignore" casei, not really ignored.
> What seems to happen is:
>  - We respond to the assignement a bit fast it seems and OpenBTS
> doesn't see the first SABM at all (not in the OpenBTS trace at all)
>  - When OpenBTS sees the SABM, it responds with the UA frame
>  - OpenBTS doesn't send a new frame until quite a bit later, which
> means the UA frame is resent several times by OpenBTS transceiver
> application using it's filling table (which is why we see only 1 UA
> frame in OpenBTS trace but multiple of them in the OsmocomBB trace)
>  - OsmocomBB had a bug where it was supposed to ignore the extraneous
> UA frame but instead was dropping the connection because of a missing
> "return" inside the switch statement.
> Cheers,
>     Sylvain
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