Ethereal-dev: Re: [Ethereal-dev] Patch for decoding errors in packet-gsm_a.c

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From: Jaap Keuter <jaap.keuter@xxxxxxxxx>
Date: Fri, 13 Jan 2006 16:22:15 +0100 (CET)
Checked in with minor change.
Made absolutely sure that the loop ends.

Thanx,
Jaap

On Fri, 13 Jan 2006, Patrik Olsson wrote:

>
> Dear Ethereal-developers,
>
> Attached is a patch that fixes several decoding problem is the gsm_a
> dissector. The bugs are also submitted to bugzilla id #684 and #687.
>
> The problems are
>
> 1. Incorrect decoding of several fields in the Mobile Station Classmark 2 IE
> in packet-gsm.c
>
> I have found incorrect decoding of several fields in the Mobile Classmark 2
> IE in GSM_A due to wrong bit masks being used
>
> "ES IND" shares one bit with "Revision Level"
>
> "A5/1 support" is bit 4, not bit 5.
>
> "CM3" is bit 8 in octet three, not bit 1 in octet two.
>
> "LCS VA" is bit 6, not bit 8.
>
>
> The fields for "A5/2" and "A5/3" support has their values swapped around.
> "0" means "not supported" and "1" means supported.
>
>
> 2. Incorrect decoding of Additional Access Technologies in IE MS Radio
> Access Capability in packet-gsm_a.c
>
> If the field "Additional Access Technologies" contains multiple additional
> access technologies, the decoding is incorrect. There is a presence flag
> missing in the decoding.
>
> Log showing the incorrect decoding
>
>     MS Radio Access Capability
>         Length: 11
>         MS RA capability 1
>             Access Technology Type: (1) GSM E --note that GSM E covers GSM P
>             Length: 0x2a bits (42)
>             RF Power Capability, GMSK Power Class: (4) 2 W (33 dBm)
>             A5 Bits: (1) A5 bits follows
>             A5/1: (1) encryption algorithm available
>
> <... not required information removed ...>
>
>             CDMA 2000 Radio Access Technology Capability: (0) CDMA 2000 not
> supported
>         MS RA capability 2
>             Access Technology Type: (15) Indicates the presence of a list of
> Additional access technologies
>             Length: 0x15 bits (21)
>             Access Technology Type: (11) unknown
>             RF Power Capability, GMSK Power Class: (6) Not specified??
>             8PSK Power Class: (0) 8PSK modulation not supported for uplink
>
>
>
>
> with the supplied patch the decoding is successful
>
>
>     MS Radio Access Capability
>         Length: 11
>         MS RA capability 1
>             Access Technology Type: (1) GSM E --note that GSM E covers GSM P
>             Length: 0x2a bits (42)
>             RF Power Capability, GMSK Power Class: (4) 2 W (33 dBm)
>             A5 Bits: (1) A5 bits follows
>             A5/1: (1) encryption algorithm available
>
> <... not required information removed ...>
>
>             CDMA 2000 Radio Access Technology Capability: (0) CDMA 2000 not
> supported
>         MS RA capability 2
>             Access Technology Type: (15) Indicates the presence of a list of
> Additional access technologies
>             Length: 0x15 bits (21)
>             Presence: (1) Present
>             Access Technology Type: (7) GSM 850
>             RF Power Capability, GMSK Power Class: (4) 2 W (33 dBm)
>             8PSK Power Class: (0) 8PSK modulation not supported for uplink
>             Presence: (1) Present
>             Access Technology Type: (3) GSM 1800
>             RF Power Capability, GMSK Power Class: (1) 1 W (30 dBm)
>             8PSK Power Class: (0) 8PSK modulation not supported for uplink
>             Presence: (0) Not Present
>
>
>
> Regards,
>
> Patrik
>
>
> --
> Patrik Olsson
> TTPCom Ltd
>