From: Albert Cahalan <albert@users.sf.net>
To: Josan Kadett <corporate@superonline.com>
Cc: linux-kernel mailing list <linux-kernel@vger.kernel.org>
Subject: RE: Cursed Checksums
Date: 22 Aug 2004 16:14:00 -0400 [thread overview]
Message-ID: <1093205640.5759.3246.camel@cube> (raw)
In-Reply-To: <E1Bz02y-00052n-3Z@sc8-sf-mx2.sourceforge.net>
On Sun, 2004-08-22 at 18:38, Josan Kadett wrote:
> In normal conditions, when NAT translates an IP header, it should do correct
> checksumming. However; when the source IP address of a packet is
> manipulated, Iptables still seems to use the "original" IP address and
> calculate the checksum accordingly. This way even if I use 3 three boxes;
>
> Original Packet --> NAT 1 --> NAT 2 --> NAT3 --> Still incorrect checksum
Sure. That's why I think this is a job for ebtables.
Note: EBtables, not IPtables. This is lower level,
dealing with raw Ethernet packets. It should be able
to mangle anything in the packet.
Just as iptables lets you change any 32-bit value in
an IP packet, ebtables should let you change any 32-bit
value in an Ethernet packet. Unlike iptables, it could
operate prior to the IP checksum verification.
Sadly, it looks like u32 mangle rules are missing.
next parent reply other threads:[~2004-08-22 22:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <E1Bz02y-00052n-3Z@sc8-sf-mx2.sourceforge.net>
2004-08-22 20:14 ` Albert Cahalan [this message]
2004-08-22 18:55 Cursed Checksums Albert Cahalan
2004-08-22 22:38 ` Josan Kadett
-- strict thread matches above, loose matches on Subject: below --
2004-08-21 2:37 Josan Kadett
2004-08-22 11:40 ` Alan Cox
2004-08-22 19:39 ` Josan Kadett
2004-08-22 21:03 ` Josan Kadett
2004-08-22 20:36 ` Alan Cox
2004-08-22 22:58 ` Olivier Galibert
2004-08-23 0:05 ` Josan Kadett
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