Wireshark · Wireshark-commits: [Wireshark-commits] master e78430f: GSMTAP: implement dissecting of PTCCH/D messages

[Wireshark code review <code-review-do-not-reply@xxxxxxxxxxxxx>]

URL: https://code.wireshark.org/review/gitweb?p=wireshark.git;a=commit;h=e78430f059e43088df2a4f19aa2454c9ba8cfb6d
Submitter: "Anders Broman <a.broman58@xxxxxxxxx>"
Changed: branch: master
Repository: wireshark

Commits:

e78430f by Vadim Yanitskiy (axilirator@xxxxxxxxx):

    GSMTAP: implement dissecting of PTCCH/D messages
    
    According to 3GPP TS 45.002, section 3.3.4.2, PTCCH (Packet Timing
    advance control channel) is a packet dedicated channel, that is
    used for continuous Timing Advance control in (E)GPRS.
    
    There are two sub-types of that logical channel:
    
      - PTCCH/U (Uplink): used to transmit random Access Bursts
        to allow estimation of the Timing Advance for one MS in
        packet transfer mode.
    
      - PTCCH/D (Downlink): used by the network to transmit
        Timing Advance updates for several MS.
    
    As per 3GPP TS 45.003, section 5.2, the coding scheme used for
    PTCCH/U is the same as for PRACH as specified in subclause 5.3,
    while the coding scheme used for PTCCH/D is the same as for
    CS-1 as specified in subclause 5.1.1.
    
    The format of PTCCH/D messages can be described as follows:
    
      +--------------+--------------+-----+---------------+------------------+
      |    Octet 1   |    Octet 2   |     |    Octet 16   |  Octet 17 .. 23  |
      +---+----------+---+----------+-----+---+-----------+------------------+
      | 0 | TA TAI=0 | 0 | TA TAI=1 | ... | 0 | TA TAI=15 | Padding 00101011 |
      +---+----------+---+----------+-----+---+-----------+------------------+
    
    what gives us 16 Timing Advance values (7 bit each) for 16 different
    mobile stations identified by TAI (0..15). The remaining space is
    padding and shall be filled with constant value 0x2B.
    
    Bug: 16096
    Change-Id: I0ce81d922a8a8c3981da2486baa3e1efcff46539
    Reviewed-on: https://code.wireshark.org/review/34660
    Reviewed-by: Pau Espin Pedrol <pespin@xxxxxxxxxxx>
    Petri-Dish: Anders Broman <a.broman58@xxxxxxxxx>
    Tested-by: Petri Dish Buildbot
    Reviewed-by: Anders Broman <a.broman58@xxxxxxxxx>
    

Actions performed:

    from  157dc2f   GSM RLC/MAC: fix: account MAC header as a part of rlcmac_tree
     add  e78430f   GSMTAP: implement dissecting of PTCCH/D messages


Summary of changes:
 epan/dissectors/packet-gsmtap.c | 62 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)