Wireshark-dev: [Wireshark-dev] ICMP and endian-ness issue
From: "Maynard, Chris" <[email protected]>
Date: Fri, 18 Sep 2009 16:07:30 -0400
I am capturing ICMP traffic from both a Linux PC and a Windows PC using
a customized version of Wireshark with the changes to the ICMP dissector
from this bug report
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=4014.

While doing this, I noticed that ICMP sequence #'s from a Linux PC
increase sequentially, as one would expect.  For example, 1, 2, 3, ...
The ICMP sequence #'s from a Windows PC is a different matter though.
As an example, Wireshark shows the following sequence in one of my
capture files: 7682 (0x1e02), 7938 (0x1f02), 8194 (0x2002), 8450
(0x2102), 8706 (0x2202), 8962 (0x2302).   The problem is obviously one
of endian-ness.  Quite surprisingly to me, it seems that Windows sends
ICMP echo request packets with multi-byte fields in little-endian
format.  This makes it a little difficult to track sequence #'s and
visually tell if a request and/or response is missing, out-of-order.

I guess it's impossible or nearly so to heuristically figure out if the
format is big or little endian.  Would adding a preference to specify
the endian-ness be a reasonable solution, with big-endian being the
obvious default?

Anyone else surprised to see little-endian sequence #'s in Windows ICMP
request packets?
- Chris

CONFIDENTIALITY NOTICE: The contents of this email are confidential
and for the exclusive use of the intended recipient. If you receive this
email in error, please delete it from your system immediately and 
notify us either by email, telephone or fax. You should not copy,
forward, or otherwise disclose the content of the email.