From: Antony Stone <Antony@Soft-Solutions.co.uk>
To: netfilter@lists.netfilter.org
Subject: Re: Checksumming Issues
Date: Fri, 21 Nov 2003 20:27:21 +0000 [thread overview]
Message-ID: <200311212027.hALKRQj29614@agate.rockstone.co.uk> (raw)
In-Reply-To: <Pine.SOL.4.20.0311211514050.16319-100000@csa.bu.edu>
On Friday 21 November 2003 8:15 pm, Leonid Veytser wrote:
> A general question about checksumming. If I change the destination address
> in the IP header, then of course I need to recalculate the IP header
> checksum.
"You" the user (or system administrator) do not need to recalculate any
checksums - the SNAT or DNAT code does this for you.
> But do I have to recalculate the checksum of the next protocol
> header (ie TCP, UDP, etc)?
No. Everything is handled for you in the background. Anyway, if you only
change the IP address (source and/or destination), the TCP or UDP checksum
remains valid.
Antony.
--
Feeling bad at breakfast because you don't have a hangover is evidence of a
complex emotional life it can take many years to perfect.
- Pete McCarthy, The Road to McCarthy
Please reply to the list;
please don't CC me.
next prev parent reply other threads:[~2003-11-21 20:27 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-11 19:13 NF_STOLEN effect on TCP A K A
2003-11-11 21:59 ` Problem with FORWARD hook Leonid Veytser
2003-11-11 22:06 ` Stuart J. Browne
2003-11-11 22:12 ` 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 [this message]
2003-11-12 0:40 ` Problem with FORWARD hook Leonid Veytser
-- strict thread matches above, loose matches on Subject: below --
2003-11-21 20:42 Checksumming Issues Hildebrand, Brian
2003-11-21 20:47 ` Antony Stone
2003-11-21 20:56 ` Leonid Veytser
2003-11-21 21:00 Hildebrand, Brian
2003-11-21 21:13 ` Antony Stone
2003-11-21 21:31 Hildebrand, Brian
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