Wireshark-commits: [Wireshark-commits] master b4284772: GSM RR: properly handle CSN.1 Null breakpoi
URL: https://code.wireshark.org/review/gitweb?p=wireshark.git;a=commit;h=b4284772b360bc105f79da49b2b0461526b2e594
Submitter: "Anders Broman <a.broman58@xxxxxxxxx>"
Changed: branch: master
Repository: wireshark
Commits:
b4284772 by Vadim Yanitskiy (vyanitskiy@xxxxxxxxxxx):
GSM RR: properly handle CSN.1 Null breakpoints in IA Rest Octets
In CSN.1, the message may be safely cropped at specific parts
of its definition called Null breakpoints or rather "message
escape" labels (see 3GPP TS 44.060, section 11.1.3.3).
These labels usually preceed the optional protocol extensions,
added in newer releases of 3GPP specifications. The following
IA Rest Octets (see 3GPP TS 44.018, section 10.5.2.16) sample
illustrates that:
IA Rest Octets
H... .... = First Discriminator Bit: High
.H.. .... = Second Discriminator Bit: High
..0. .... = Discriminator Bit: Packet Assignment
...1 .... = Discriminator Bit: Packet Downlink Assignment
Packet Downlink Assignment
.... 0000 0000 0000 0000 0000 0000 0000 0001 .... = TLLI: 0x00000001
.... 1... = TFI Assignment (etc): Present
.... .000 00.. .... = TFI_Assignment: 0
..0. .... = RLC_Mode: RLC acknowledged mode
...0 .... = Alpha: Not Present
.... 0000 0... .... = Gamma: 0 dB (0)
.0.. .... = Polling: no action is required from MS
..0. .... = TA_Valid: the timing advance value is not valid
...0 .... = Timing Advance Index: Not Present
.... 0... = TBF Starting Time: Not Present
.... .0.. = P0: Not Present
.... ..L. = Additions in R99: Not Present
.... ...L = Additions in Rel-6: Not Present
[Malformed Packet: GSM CCCH]
[Expert Info (Error/Malformed): Malformed Packet (Exception occurred)]
[Malformed Packet (Exception occurred)]
[Severity level: Error]
[Group: Malformed]
In GSM, the maximum length of a MAC block (on xCCH channels) is
limited to 23 bytes, so the message was cut in the middle, and
the Rel-7, Rel-10, and Rel-13 additions did not fit. Although,
the message is still correct according to the specifications,
so we should not consider it as "Malformed".
Change-Id: I6920c87d3a3247f4342fea69a8bb40c28316f422
Reviewed-on: https://code.wireshark.org/review/37912
Reviewed-by: Harald Welte <laforge@xxxxxxxxxxxx>
Reviewed-by: Pau Espin Pedrol <pespin@xxxxxxxxxxx>
Petri-Dish: Alexis La Goutte <alexis.lagoutte@xxxxxxxxx>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@xxxxxxxxx>
Actions performed:
from 6b4fae1 Windows: Switch from the WpdPack SDK to vcpkg's libpcap.
add b4284772 GSM RR: properly handle CSN.1 Null breakpoints in IA Rest Octets
Summary of changes:
epan/dissectors/packet-gsm_a_rr.c | 10 ++++++++++
1 file changed, 10 insertions(+)
