From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266351AbUHVVl0 (ORCPT ); Sun, 22 Aug 2004 17:41:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266469AbUHVVjg (ORCPT ); Sun, 22 Aug 2004 17:39:36 -0400 Received: from qfep05.superonline.com ([212.252.122.162]:62640 "EHLO qfep05.superonline.com") by vger.kernel.org with ESMTP id S266319AbUHVVil (ORCPT ); Sun, 22 Aug 2004 17:38:41 -0400 From: "Josan Kadett" To: "'Albert Cahalan'" Cc: Subject: RE: Cursed Checksums Date: Mon, 23 Aug 2004 00:38:30 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook, Build 11.0.5510 In-Reply-To: <1093200924.5759.3088.camel@cube> Thread-Index: AcSIj3Pv+m1w+YlTTOau+WTjWLCOdwACJfcg X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 Message-Id: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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 The wrong checksum is carried over and over the line. It is really a strange issue and I could not find a reason why still I get the incorrect checksum even after the IP header is translated three times... As I said, the original packet must be corrected before it is transmitted to another place and I think it is just two or three lines of code in the kernel, but the question is "where"... -----Original Message----- From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Albert Cahalan Sent: Sunday, August 22, 2004 8:55 PM To: linux-kernel mailing list Subject: RE: Cursed Checksums I'm surprised to find that there doesn't seem to be an ebtables mangle table. That'd be the place to match on a u32, then either change that or just mark the packet for checksuming. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/