problems with dissecting

Ivan Kluchnikov Ivan.Kluchnikov at fairwaves.ru
Thu Feb 28 23:02:51 UTC 2013


hi, andreas and steve!

I fixed this problem, now decoding should work, you can check the last
commit of master branch.
There were problems with decoding and encoding of CSN_RECURSIVE_TARRAY,
CSN_RECURSIVE_TARRAY_1, CSN_RECURSIVE_TARRAY_2.


2013/2/19 jolly <andreas at eversberg.eu>:
> hi,
>
> steve and me experienced a problem with dissecting a "packet resource
> request" at pcu. the patch i attached will show the following output:
>
> $ make && src/osmo-pcu
>
> PayloadType = 1 | spare = 0 | R = 0 | MESSAGE_TYPE = 5 | Exist_ACCESS_TYPE =
> 1 | ACCESS_TYPE = 3 |  : ID | Choice PacketResourceRequestID = 1 | u.TLLI =
> 0x7ee0e8fd | : End ID | Exist_MS_Radio_Access_capability = 1 |  :
> MS_Radio_Access_capability | MS_RA_capability_value { | Choice
> MS_RA_capability_value_Choice = 1 | u.Content length = 34 |
> RF_Power_Capability = 4 | Exist_A5_bits = 1 | A5_bits = 96 | ES_IND = 1 | PS
> = 0 | VGCS = 0 | VBS = 0 | Exist_Multislot_capability = 1 |  :
> Multislot_capability | Exist_HSCSD_multislot_class = 0 |
> Exist_GPRS_multislot_class = 1 | GPRS_multislot_class = 10 ....
>
> this is all correct, but then i patched the get_ms_class_by_capability()
> function at grps_rlcmac_data.c:
>
> ...
> printf("we have = %d\n", cap->Count_MS_RA_capability_value);
>         for (i = 0; i < cap->Count_MS_RA_capability_value; i++) {
> printf("index=%d\n", cap->MS_RA_capability_value[i].IndexOfAccTech);
> printf("exists multislot capability %d\n",
> cap->MS_RA_capability_value[i].u.Content.Exist_Multislot_capability);
> printf("exists class %d\n",
> cap->MS_RA_capability_value[i].u.Content.Multislot_capability.Exist_GPRS_multislot_class);
> printf("class %d\n",
> cap->MS_RA_capability_value[i].u.Content.Multislot_capability.GPRS_multislot_class);
> ...
>
> the output continues as this:
>
> we have = 2
> index=2
> exists multislot capability 0
> exists class 1
> class 10
> index=0
> exists multislot capability 0
> exists class 0
> class 0
>
> the "class 10" is correct, also it is correct that the class only exists in
> the first entry of the capability array. the output of the dissector states
> that multislot capability exists (Exist_Multislot_capability = 1), but if i
> look at the structure, this field is not set.
>
> i looked at the dissector code, but don't really understand why
> CSN_NEXT_EXIST works for some elements and not for others.
>
> any ideas?
>
> regards,
>
> andreas
>



-- 
Regards,
Ivan Kluchnikov.
http://fairwaves.ru




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