Wireshark · Wireshark-bugs: [Wireshark-bugs] [Bug 12693] New: Small bug in Modbus (mbtcp.c/h) dissector exception information

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Bug ID	12693
Summary	Small bug in Modbus (mbtcp.c/h) dissector exception information
Product	Wireshark
Version	2.3.x (Experimental)
Hardware	x86-64
OS	Windows 7
Status	UNCONFIRMED
Severity	Minor
Priority	Low
Component	Dissection engine (libwireshark)
Assignee	bugzilla-admin@wireshark.org
Reporter	dl.soluz@gmx.net

Created attachment 14780 [details]
simple single pcap showing the wrong function code

Build Information:
Wireshark 2.3.0-128-g98e8b26 (v2.3.0rc0-128-g98e8b26 from master)

Copyright 1998-2016 Gerald Combs <gerald@wireshark.org> and contributors.
License GPLv2+: GNU GPL version 2 or later
<http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
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 (64-bit) with Qt 5.6.1, with WinPcap (4_1_3), with GLib 2.42.0, with
zlib 1.2.8, with SMI 0.4.8, with c-ares 1.11.0, with Lua 5.2, with GnuTLS
3.2.15, with Gcrypt 1.6.2, with MIT Kerberos, with GeoIP, with QtMultimedia,
with AirPcap.

Running on 64-bit Windows 7 Service Pack 1, build 7601, with locale
German_Germany.1252, with WinPcap version 4.1.3 (packet.dll version
4.1.0.2980),
based on libpcap version 1.0 branch 1_0_rel0b (20091008), with GnuTLS 3.2.15,
with Gcrypt 1.6.2, without AirPcap.
Intel(R) Core(TM)2 Quad CPU    Q8300  @ 2.50GHz, with 8190MB of physical
memory.

Built using Microsoft Visual C++ 12.0 build 40629
--
there is a single Modbus exception response in the attached pcap

Modbus/TCP
 Transaction Identifier: 0
 Protocol Identifier: 0
 Length: 3
 Unit Identifier: 0
Function 8:  Diagnostics.  Exception: Illegal function
 Function Code: Unknown (136) <== Wrong, should be also 8
 Exception Code: Illegal function (1)

the execption bit does not get masked for the second Function Code-Output
should be 8 == (136 & 0x7F) - like one line above

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