From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9EFF0C433E0 for ; Wed, 3 Feb 2021 22:21:38 +0000 (UTC) Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A52E661477 for ; Wed, 3 Feb 2021 22:21:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A52E661477 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=michaelblizek.twilightparadox.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.94) (envelope-from ) id 1l7QWW-0002GS-7R; Wed, 03 Feb 2021 17:21:20 -0500 Received: from michaelblizek.twilightparadox.com ([193.238.157.55]) by shelob.surriel.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1l7QWV-0002GM-7i for kernelnewbies@kernelnewbies.org; Wed, 03 Feb 2021 17:21:19 -0500 Received: from localhost ([127.0.0.1] helo=grml) by michaelblizek.twilightparadox.com with esmtp (Exim 4.92) (envelope-from ) id 1l7QWH-0001my-Rb; Wed, 03 Feb 2021 23:21:06 +0100 Date: Wed, 3 Feb 2021 23:21:10 +0100 From: michi1@michaelblizek.twilightparadox.com To: kernelnewbies@kernelnewbies.org, netdev@vger.kernel.org, kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, jakub@cloudflare.com, pabeni@redhat.com Subject: Re: UDP implementation and the MSG_MORE flag Message-ID: <20210203222054.6zhq47o7rzjstpdq@grml> References: <20210126141248.GA27281@optiplex> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210126141248.GA27281@optiplex> User-Agent: NeoMutt/20170113 (1.7.2) X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kernelnewbies-bounces@kernelnewbies.org Hi! On 15:12 Tue 26 Jan , Oliver Graute wrote: > Some UDP packets send via the loopback interface are dropped in the > kernel on the receive side when using sendto with the MSG_MORE flag. > Every drop increases the InCsumErrors in /proc/self/net/snmp. Some > example code to reproduce it is appended below. > > In the code we tracked it down to this code section. ( Even a little > further but its unclear to me wy the csum() is wrong in the bad case) I think it is unlikely that the error is on the receiving side. I recommend to capture the data that is being sent with a sniffer and see if there is anything wrong. You may also want to try disabling hardware acceleration on your network devices, because the checksum is sometimes done in hardware. -Michi -- programing a layer 3+4 network protocol for mesh networks see http://michaelblizek.twilightparadox.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies