https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=4504
Summary: IEEE 802.15.4 Frame Check Sequence in Chipcon Mode
incorrectly displayed
Product: Wireshark
Version: 1.2.5
Platform: x86
OS/Version: Windows Vista
Status: NEW
Severity: Trivial
Priority: Low
Component: Wireshark
AssignedTo: wireshark-bugs@xxxxxxxxxxxxx
ReportedBy: honarbacht@xxxxxxxxx
Created an attachment (id=4303)
--> (https://bugs.wireshark.org/bugzilla/attachment.cgi?id=4303)
A Wireshark capture file that makes the problem obvious
Build Information:
Version 1.2.5 (SVN Rev 31296)
Copyright 1998-2009 Gerald Combs <gerald@xxxxxxxxxxxxx> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Compiled with GTK+ 2.16.2, with GLib 2.20.3, with WinPcap (version unknown),
with libz 1.2.3, without POSIX capabilities, with libpcre 7.0, with SMI 0.4.8,
with c-ares 1.6.0, with Lua 5.1, with GnuTLS 2.8.1, with Gcrypt 1.4.4, with MIT
Kerberos, with GeoIP, with PortAudio V19-devel (built Dec 17 2009), with
AirPcap.
Running on 32-bit Windows Vista Service Pack 2, build 6002, with WinPcap
version
4.1.1 (packet.dll version 4.1.0.1753), based on libpcap version 1.0 branch
1_0_rel0b (20091008), GnuTLS 2.8.1, Gcrypt 1.4.4, without AirPcap.
Built using Microsoft Visual C++ 9.0 build 30729
Wireshark is Open Source Software released under the GNU General Public
License.
Check the man page and http://www.wireshark.org for more information.
--
There are two issues with the frame check sequence (FCS) field in IEEE 802.15.4
frames, when displayed in "Chipcon Mode". In this mode, the original 16-bit CRC
is replaced by an "FCS valid" bit, a received signal strength indicator (RSSI)
and a correlation value.
1) The RSSI Value is a signed value, but Wireshark treats it as unsigned,
yielding incorrect values, e.g. 249dBm instead of -7dBm, which would have been
the correct value. Please refer to the CC2420 data sheet for details (Texas
Instruments document no. SWRS041B).
2) The byte order does not match the original CC2420 byte order for the FCS.
The FCS bytes need to be swapped (little-endian, big-endian issue). Notice that
in the attached capture, this swapping has been done in the capture hardware to
accommodate to the present situation.
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