Wireshark-bugs: [Wireshark-bugs] [Bug 10807] New: Acp 142-A checksum algorithm and time field of
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Thu, 25 Dec 2014 21:16:59 +0000
Bug ID 10807
Summary Acp 142-A checksum algorithm and time field of data pdu
Product Wireshark
Version unspecified
Hardware x86
OS Linux (other)
Status UNCONFIRMED
Severity Enhancement
Priority Low
Component Dissection engine (libwireshark)
Assignee bugzilla-admin@wireshark.org
Reporter r.cristian.ramirez@gmail.com 

Created attachment 13351 [details]
Basic message transfer using Acp142 over IP network

Build Information:
Paste the COMPLETE build information from "Help->About Wireshark", "wireshark
-v", or "tshark -v".
--
Hi,

ACP 142 (PMul) protocol has two versions. The first one [1] was released at
2001 and the second one [2] was released at 2008. The first version suggests to
use 8-bit Fletcher's algorithm, which produces 16 bit checksum. And, an
implementation of this algorithm is provided in the specification. Current PMul
dissector [3] of the Wireshark uses this provided algorithm.

The checksum description in the second version was changed: Provided algorithm
was removed and below statement is given without an algorithm:
"The checksum field is the 16 bit one's complement of the one's complement sum
of all 16 bit words in the header." 

As far as I know, above statement decribes the TCP/IP checksum and an update is
needed for PMul dissector. I used given algorithm here [4] in order calculate
checksum but I added 0x00 at the end of the stream if the stream length is odd.

In addition to the checksum algorithm, data pdus of the new version include a 8
byte time field at the end of the pdu.

There is a capture file attached which contains a message transfer using Acp142
over IP network.

By the way, I am not the owner of the discussed Acp142 implementation. There
may be some other changes in the new version.

Thanks.

[1] jcs.dtic.mil/j6/cceb/acps/acp142/ACP142.pdf
[2] jcs.dtic.mil/j6/cceb/acps/acp142/ACP142A.pdf
[3]
https://code.wireshark.org/review/gitweb?p=wireshark.git;a=blob;f=epan/dissectors/packet-p_mul.c;h=a03e69f10825e6dacb82f3aacb33b465adeb721a;hb=HEAD
[4] http://www.netfor2.com/ipsum.htm

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