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Wireshark-bugs: [Wireshark-bugs] [Bug 2971] Add new Bssap dissectors for the Lb interface

Date: Wed, 19 Nov 2008 15:22:11 -0800 (PST)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=2971


Johnny Mitrevski <mitrevj@xxxxxxxxxxx> changed:

           What    |Removed                     |Added
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   Attachment #2503|                            |review_for_checkin?
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--- Comment #28 from Johnny Mitrevski <mitrevj@xxxxxxxxxxx>  2008-11-19 15:22:10 PDT ---
Created an attachment (id=2503)
 --> (https://bugs.wireshark.org/bugzilla/attachment.cgi?id=2503)
Addition of BSSMAP LE dissector

This file adds BSSMAP LE dissector to wireshark.

Anders,

Just a few notes to explain what I have done:

1) I added a selection switch to the BSSAP preferences that allows the user to
determine whether the file is using the GSM-A or Lb interface. This is because
I could not use the value of the SSN as a determining factor. For a lot of
messages the SSN is not present i.e. (SCCP DT1). 
I noticed that when SSN is not available the BSSAP is selected based on the
decision made by the method packet-bssap.dissect_bssap_heur(). The logic in
here looks at the first two bytes of the BSSAP message and informs the
framework it is appropriate dissector to use. As there is no further
distinguishing feature between BSSMAP and BSSMAP_LE I thought that a switch in
the BSSAP preferences would work best. Let me know if you have any other
thoughts.

2) I declared some element dissectors in common.h so I can call them from
multiple classes.

3) The information element IDs of IMSI, IMEI, GANSS Location Type, GANSS
Assistance Data, and GANSS Positioning Data are different between the BSSMAP
and BSSMAP_LE dissectors. In the example file I provided you will see that a
decoded IMSI for Lb will appear as extraneous data for GSM-A

Regards,
Johnny


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