https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=3432
Summary: GSM SMS UDH fill bits incorrect
Product: Wireshark
Version: 1.0.7
Platform: Other
OS/Version: Windows XP
Status: NEW
Severity: Normal
Priority: Medium
Component: Wireshark
AssignedTo: wireshark-bugs@xxxxxxxxxxxxx
ReportedBy: ames.lai@xxxxxxxxx
Build Information:
Version 1.0.7 (SVN Rev 28014)
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+ 2.12.8, with GLib 2.14.6, with WinPcap (version unknown),
with libz 1.2.3, without POSIX capabilities, with libpcre 7.0, with SMI 0.4.8,
with ADNS, with Lua 5.1, with GnuTLS 2.6.3, with Gcrypt 1.4.3, with MIT
Kerberos, with PortAudio V19-devel, with AirPcap.
Running on Windows XP Service Pack 3, build 2600, with WinPcap version 4.0.2
(packet.dll version 4.0.0.1040), based on libpcap version 0.9.5, without
AirPcap.
Built using Microsoft Visual C++ 6.0 build 8804
Wireshark is Open Source Software released under the GNU General Public
License.
Check the man page and http://www.wireshark.org for more information.
--
Hello,
I've noticed that there is an extra bit in the message considered as fill bit.
Looking at the Wireshark code, we see that when fill_bits = 2, the
fill_bits_mask is at 0xe0, which translates into 3 bits of fill bits displayed
on Wireshark.
The following is the code in question taken from
http://anonsvn.wireshark.org/viewvc/releases/wireshark-1.0.7/epan/dissectors/packet-gsm_sms.c?revision=28024&view=markup
Regards,
Ames
#define NUM_FILL_BITS_MASKS 6
...
static guint8 fill_bits_mask[NUM_FILL_BITS_MASKS] =
{ 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc };
...
if (seven_bit)
{
/* step over fill bits ? */
fill_bits = 7 - (((oct + 1) * 8) % 7);
if (fill_bits < NUM_FILL_BITS_MASKS)
{
oct = tvb_get_guint8(tvb, offset);
other_decode_bitfield_value(bigbuf, oct,
fill_bits_mask[fill_bits], 8);
proto_tree_add_text(udh_subtree,
tvb, offset, 1,
"%s : Fill bits",
bigbuf);
}
}
--
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