Bug 136618 – Ethereal reports wrong checksum on outgoing UDP packets

Bug 136618 - Ethereal reports wrong checksum on outgoing UDP packets

Summary:	Ethereal reports wrong checksum on outgoing UDP packets

Status:	CLOSED DUPLICATE of bug 129823

Aliases:	None

Product:	Fedora
Classification:	Fedora
Component:	tcpdump (Show other bugs)
Sub Component:
Version:	rawhide
Hardware:	i386 Linux

Priority	medium Severity medium
Target Milestone:	---
Target Release:	---
Assigned To:	Harald Hoyer
QA Contact:
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Depends On:
Blocks:
	Show dependency tree / graph

Reported:	2004-10-21 04:25 EDT by Tomas Mraz
Modified:	2007-11-30 17:10 EST (History)
CC List:	1 user (show)

See Also:
Fixed In Version:
Doc Type:	Bug Fix
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Last Closed:	2006-02-21 14:06:31 EST
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Attachments	(Terms of Use)
A very simple program to send UDP packets (761 bytes, text/plain) 2004-10-21 04:39 EDT, Tomas Mraz	no flags	Details
Add an attachment (proposed patch, testcase, etc.)

Groups: None (edit)

Description Tomas Mraz 2004-10-21 04:25:16 EDT

Description of problem:
When Ethereal captures outgoing UDP packets it reports a wrong
checksum on them however when I use it to capture the packets on the
receiving side the checksum is OK.

Version-Release number of selected component (if applicable):
0.10.5 from current devel

How reproducible:
Run a program which sends out UDP packets and capture them using Ethereal.

Steps to Reproduce:
1.
2.
3.
  
Actual results:
The captured packets have incorrect checksum but in fact they haven't
as verified on receiving side.

Expected results:
The captured packets have correct checksum.

Additional info:
tcpdump seems to capture the packets with right checksum.

Comment 1 Tomas Mraz 2004-10-21 04:38:12 EDT

Sorry for the last info: tcpdump actually captures the packets with
WRONG checksums too. So the problem lies probably in libpcap?

Comment 2 Tomas Mraz 2004-10-21 04:39:30 EDT

Created attachment 105578 [details]
A very simple program to send UDP packets

Change IP address to host you want to send the packets to.

Comment 3 Harald Hoyer 2004-10-21 04:44:01 EDT

which NIC?

Comment 4 Tomas Mraz 2004-10-21 04:50:33 EDT

02:0c.0 Ethernet controller: Intel Corp. 82540EM Gigabit Ethernet
Controller (rev 02)
        Subsystem: Dell Computer Corporation: Unknown device 0151
        Flags: bus master, 66Mhz, medium devsel, latency 64, IRQ 9
        Memory at fcfe0000 (32-bit, non-prefetchable)
        I/O ports at df40 [size=64]
        Capabilities: [dc] Power Management version 2
        Capabilities: [e4] PCI-X non-bridge device.
        Capabilities: [f0] Message Signalled Interrupts: 64bit+
Queue=0/0 Enable-

libpcap version 0.8.3, kernel 2.6.8-1.610

Comment 5 Harald Hoyer 2004-10-21 04:53:22 EDT

some network cards compute the checksum on their own..
maybe a dup of bug #129823

Comment 6 Harald Hoyer 2004-10-21 04:54:37 EDT

Oh, same NIC... 

*** This bug has been marked as a duplicate of 129823 ***

Comment 7 Radek Vokal 2004-10-22 03:30:38 EDT

This is described by ethereal developers -
http://www.ethereal.com/faq#q5.14

Comment 8 Red Hat Bugzilla 2006-02-21 14:06:31 EST

Changed to 'CLOSED' state since 'RESOLVED' has been deprecated.

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