From: Antony Stone <Antony@Soft-Solutions.co.uk>
To: netfilter@lists.netfilter.org
Subject: Re: Checksumming Issues
Date: Fri, 21 Nov 2003 20:47:40 +0000 [thread overview]
Message-ID: <200311212047.hALKljj29632@agate.rockstone.co.uk> (raw)
In-Reply-To: <D8FBABA1EF6F2E4DBCC88903F60691F3021BD92B@houxchsvr.ucscorp.ucs.pvt>
On Friday 21 November 2003 8:42 pm, Hildebrand, Brian wrote:
> I had to check my packet generator source code, because I thought the TCP
> header was calculated the same way you do. But when I checked the source
> you have to feed both the TCP and IP headers into the calculation to get a
> correct checksum. It uses some information from the IP header in the
> calculation (source and destination IP for example). So you don't actually
> use the entire IP header, just a part of it.
It is not possible that the TCP checksum depends on IP information.
TCP is layer 4 of the OSI model; IP is layer 3. The IP checksum includes
the TCP contents, but not the other way around.
Antony.
--
There's no such thing as bad weather - only the wrong clothes.
- Billy Connolly
Please reply to the list;
please don't CC me.
next prev parent reply other threads:[~2003-11-21 20:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-21 20:42 Checksumming Issues Hildebrand, Brian
2003-11-21 20:47 ` Antony Stone [this message]
2003-11-21 20:56 ` Leonid Veytser
-- strict thread matches above, loose matches on Subject: below --
2003-11-21 21:31 Hildebrand, Brian
2003-11-21 21:00 Hildebrand, Brian
2003-11-21 21:13 ` Antony Stone
2003-11-11 22:55 NF_QUEUE target and ip_queue.c Leonid Veytser
2003-11-21 20:15 ` Checksumming Issues Leonid Veytser
2003-11-21 20:27 ` Antony Stone
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