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=-4.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,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 965EDC4320A for ; Fri, 13 Aug 2021 11:08:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7461160F11 for ; Fri, 13 Aug 2021 11:08:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240251AbhHMLJB (ORCPT ); Fri, 13 Aug 2021 07:09:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47186 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229597AbhHMLJB (ORCPT ); Fri, 13 Aug 2021 07:09:01 -0400 Received: from mail-pl1-x62d.google.com (mail-pl1-x62d.google.com [IPv6:2607:f8b0:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 637AEC061756; Fri, 13 Aug 2021 04:08:34 -0700 (PDT) Received: by mail-pl1-x62d.google.com with SMTP id a20so11502970plm.0; Fri, 13 Aug 2021 04:08:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=+MEtveFkdOd+h/+N1vdHSRea+1UGQzxyyqVSqe8XsTI=; b=TnR5VAgs+WjVCuR/ln4UwTjYImgIev0hseQb/dL/xkKv+3HhdB19WXo8XqAB80miYf a93Nk2wFJWgirNymllqYDCKzND1IHsES1zVrJmdPjYI1nxalJjd3AMDZ1dqZ1ewOe8zg dlRDYhNL7TEsf19rlYGyao6p+tni487AVru69OhhU6Qgls/zYWpM2lrkUR05rSuDs2mk gIvr/kHic2M5FhmBS9R2s1FNjgBNx27wIHyXY1G6iTVmOTg1Ke5Rq+RJE0M6br9XjejN Piy9NXtpo9ZytPx2rfxcN6wn+QHIOhWQ/tLnF4F9/gWjri74qCrxhzH9F83+Rb54yZnB xGkQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+MEtveFkdOd+h/+N1vdHSRea+1UGQzxyyqVSqe8XsTI=; b=SmBYEkUwNE27xl8HN3tzO53McekVi+qmEzloEhwpTPQRuq7f3uxmuOii1KsEVSu4IT 2UUrqf2FZp4Da636R4bNkNDTDqlkbCv7JI7Ach+c3TEbERZRl3QVgdZPFEgswxcuIhZP b4eRIaVOvbvZxKot8Q/kBvpaom98173ko47T3VnTlHk18eCHARDVvUMO7bR9RyvOFGZZ ALoJ/M3DtAdkuwqaaKZV0IhAYGvqh9Rk4E8/5JepkbszVSddNiK/OGoz6LxmHG1Mm1S5 9KfiEF2sIE7d7WmI0s1GATfrGmzRldX+/gQCKrt7DOgqEWR+lN8dow7+1AkBWzKFjpE/ W7tQ== X-Gm-Message-State: AOAM530Y/ebHgIT9jFutRJGpTINMIZBYm1CEVGMzciVUKms92IQmMWGN dl6GfEO8qk2mgpV41RXot/s= X-Google-Smtp-Source: ABdhPJwDu1mMWjdXxr4u1Iw6jOPGjz0PDjJS6gkHk0nxjEQ/DP+CKE8YP+jW0mpe5JVOSWYzZd6X7w== X-Received: by 2002:a17:90b:1c8c:: with SMTP id oo12mr2137167pjb.170.1628852913856; Fri, 13 Aug 2021 04:08:33 -0700 (PDT) Received: from [192.168.0.109] ([123.20.118.31]) by smtp.gmail.com with ESMTPSA id y13sm1618552pjn.34.2021.08.13.04.08.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Aug 2021 04:08:33 -0700 (PDT) Subject: Re: [PATCH v2 1/2] udp: UDP socket send queue repair To: Eric Dumazet , linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, yoshfuji@linux-ipv6.org, dsahern@kernel.org, willemb@google.com, pabeni@redhat.com, avagin@gmail.com, alexander@mihalicyn.com, lesedorucalin01@gmail.com References: <20210811154557.6935-1-minhquangbui99@gmail.com> <721a2e32-c930-ad6b-5055-631b502ed11b@gmail.com> <7f3ecbaf-7759-88ae-53d3-2cc5b1623aff@gmail.com> <489f0200-b030-97de-cf3a-2d715b07dfa4@gmail.com> From: Bui Quang Minh Message-ID: <3f861c1d-bd33-f074-8ef3-eede9bff73c1@gmail.com> Date: Fri, 13 Aug 2021 18:08:28 +0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <489f0200-b030-97de-cf3a-2d715b07dfa4@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/12/2021 10:51 PM, Eric Dumazet wrote: > > > On 8/12/21 3:46 PM, Bui Quang Minh wrote: >> >> >> On 8/11/2021 11:14 PM, Eric Dumazet wrote: >>> >>> >>> On 8/11/21 5:45 PM, Bui Quang Minh wrote: >>>> In this patch, I implement UDP_REPAIR sockoption and a new path in >>>> udp_recvmsg for dumping the corked packet in UDP socket's send queue. >>>> >>>> A userspace program can use recvmsg syscall to get the packet's data and >>>> the msg_name information of the packet. Currently, other related >>>> information in inet_cork that are set in cmsg are not dumped. >>>> >>>> While working on this, I was aware of Lese Doru Calin's patch and got some >>>> ideas from it. >>> >>> >>> What is the use case for this feature, adding a test in UDP fast path ? >> >> This feature is used to help CRIU to dump CORKed UDP packet in send queue. I'm sorry for being not aware of the performance perspective here. > > UDP is not reliable. > > I find a bit strange we add so many lines of code > for a feature trying very hard to to drop _one_ packet. > > I think a much better changelog would be welcomed. The reason we want to dump the packet in send queue is to make to state of the application consistent. The scenario is that when an application sends UDP packets via UDP_CORK socket or with MSG_MORE, CRIU comes and checkpoints the application. If we drop the data in send queue, when application restores, it sends some more data then turns off the cork and actually sends a packet. The receiving side may get that packet but it's unusual that the first part of that packet is missing because we drop it. So we try to solve this problem with some help from the Linux kernel. Thanks, Quang Minh.