Wireshark-bugs: [Wireshark-bugs] [Bug 6774] New: Bug: out-of-order packets tagged as "ACKed lost
Date Index · Thread Index · Other Months · All Mailing Lists
Date Prev · Date Next · Thread Prev · Thread Next
From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Fri, 27 Jan 2012 06:36:14 -0800 (PST)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6774

           Summary: Bug: out-of-order packets tagged as "ACKed lost
                    segment"
           Product: Wireshark
           Version: 1.6.5
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: Low
         Component: Wireshark
        AssignedTo: bugzilla-admin@xxxxxxxxxxxxx
        ReportedBy: elof@xxxxxxxxxxxxxx


Build Information:
Version 1.6.5 (SVN Rev 40429 from /trunk-1.6)

Copyright 1998-2012 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 (32-bit) with GTK+ 2.22.1, with GLib 2.26.1, with WinPcap (version
unknown), with libz 1.2.5, without POSIX capabilities, without libpcre, with
SMI
0.4.8, with c-ares 1.7.1, with Lua 5.1, without Python, with GnuTLS 2.10.3,
with
Gcrypt 1.4.6, with MIT Kerberos, with GeoIP, with PortAudio V19-devel (built
Jan
10 2012), with AirPcap.

Running on Windows XP Service Pack 3, build 2600, with WinPcap version 4.1.2
(packet.dll version 4.1.0.2001), based on libpcap version 1.0 branch 1_0_rel0b
(20091008), GnuTLS 2.10.3, Gcrypt 1.4.6, without AirPcap.

Built using Microsoft Visual C++ 9.0 build 21022

Wireshark is Open Source Software released under the GNU General Public
License.

Check the man page and http://www.wireshark.org for more information.
--
I think there is a bug in Wireshark regarding the TCP Out of Order tag.

If the last packets at the end of a TCP connection (the FINACK, FINACK or ACK)
are received out-of-order, they are not tagged as "Out-of-order segment", but
incorrectly as "ACKed lost segment".

This is misleading! There are no dropped packets, they are just received in the
wrong order.

Example:
Real traffic:
1 -> SYN
2 <- SYN ACK
3 -> ACK
4 -> GET /
5 <- HTTP/1.1 200 OK
6 -> ACK
7 -> FIN ACK
8 <- FIN ACK
9 -> ACK

For some reason, packets 7 and 8 were received by Wireshark out of order:
1 -> SYN
2 <- SYN ACK
3 -> ACK
4 -> GET /
5 <- HTTP/1.1 200 OK
6 -> ACK (ack of #5)
7 <- FIN ACK (ack of #8, a future packet)
8 -> FIN ACK
9 -> ACK (ack of #7)

In the Wireshark GUI (and in the Expert Info), packet #7 is tagged [TCP ACKed
lost segment] even though all 9 packets were received.


So either the out-of-order detection in Wireshark fail, or the "ACKed lost
segment" detection outrank the out-of-order detection. In any case, the
resulting tag is misleading.

/Elof

-- 
Configure bugmail: https://bugs.wireshark.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching all bug changes.