GSMTAP / layer23 / wireshark updates

Harald Welte laforge at
Thu Mar 4 14:52:55 UTC 2010


I've improved the layer23 gsmtap support to add support for
* uplink frames, sent by layer23 to L1
* properly support dedicated channels with LAPDm
* allow the user to specify the GSMTAP destination IP address

In order to use the new features, you need to 
1) use the new gsmtap.patch for wireshark
2) use the '-i dstip' option of layer23, as the default is now to NOT
   generate GSMTAP UDP Packets

I'm attaching a screen-shot showing the wireshark decode of the LOC UPD REQ
generated by layer23.  As you can see from the packet list, the BTS responds
with the UA packet containing the same LOC UPD REQ as part of the contention
resolution in LAPDm, just as expected.

- Harald Welte <laforge at> 
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)
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