From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <dev-bounces@dpdk.org>
Received: from dpdk.org (dpdk.org [92.243.14.124])
	by dpdk.space (Postfix) with ESMTP id 538E5A0679
	for <public@inbox.dpdk.org>; Mon,  1 Apr 2019 17:29:54 +0200 (CEST)
Received: from [92.243.14.124] (localhost [127.0.0.1])
	by dpdk.org (Postfix) with ESMTP id 27800378E;
	Mon,  1 Apr 2019 17:29:54 +0200 (CEST)
Received: from hqmgw2.hq.eso.org (hqmgw2.hq.eso.org [134.171.42.202])
 by dpdk.org (Postfix) with ESMTP id BC7C32B99
 for <dev@dpdk.org>; Mon,  1 Apr 2019 17:29:52 +0200 (CEST)
X-IronPort-AV: E=Sophos;i="5.60,297,1549926000"; d="scan'208";a="47267616"
Received: from mxroute02.hq.eso.org ([134.171.15.34])
 by hqmgw2.hq.eso.org with ESMTP; 01 Apr 2019 17:29:51 +0200
Received: from mxadauth03.hq.eso.org (mxadauth03.hq.eso.org [134.171.42.80])
 by mxroute02.hq.eso.org (Postfix) with ESMTP id DB30F120002;
 Mon,  1 Apr 2019 17:29:51 +0200 (CEST)
Received: from [127.0.0.1] (hq-000-kemp01.hq.eso.org [134.171.42.9])
 (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits))
 (No client certificate requested) (Authenticated sender: nbenes)
 by mxadauth03.hq.eso.org (Postfix) with ESMTPSA id D55D320B52;
 Mon,  1 Apr 2019 17:29:51 +0200 (CEST)
To: dev <dev@dpdk.org>
From: "N. Benes" <nbenes@eso.org>
Message-ID: <65744706-bc88-f144-f85e-1b0292402cff@eso.org>
Date: Mon, 01 Apr 2019 15:29:00 +0000
MIME-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Subject: [dpdk-dev] Bug in IPv4 header checksum computation?
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>
Message-ID: <20190401152900.wTtLiTYj7qhFgiR_HYwQH9R2XY0x8bExBtL2jX-5H5k@z>

Hi,

I wrote to the users list a bit more a week ago concerning the IPv4
Header Checksum computation and received no comments on it yet:

https://mails.dpdk.org/archives/users/2019-March/004021.html
https://mails.dpdk.org/archives/users/2019-March/004022.html

I have the impression that the current implementation wrongly does a
conditional final inversion of the computed sum. This is correct for
e.g. UDP, but I think it is not for an IPv4 Header (header checksum is
not optional).

If it is a bug, this could result in a surprisingly high number of
invalid/dropped IPv4 packets, when the checksum is calculated manually
via the DPDK API (not NIC-offloaded) and the IPv4 header has an
appropriate combination of values e.g. the IP Identification field.

Cheers!