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=-2.7 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,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 EC1C5C47095 for ; Tue, 8 Jun 2021 03:14:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2CE660240 for ; Tue, 8 Jun 2021 03:14:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230444AbhFHDQD (ORCPT ); Mon, 7 Jun 2021 23:16:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230237AbhFHDQB (ORCPT ); Mon, 7 Jun 2021 23:16:01 -0400 Received: from mail-lf1-x129.google.com (mail-lf1-x129.google.com [IPv6:2a00:1450:4864:20::129]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95BBAC061574; Mon, 7 Jun 2021 20:13:54 -0700 (PDT) Received: by mail-lf1-x129.google.com with SMTP id m21so13990437lfg.13; Mon, 07 Jun 2021 20:13:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=b71LtaSQOEalI7Wb6oIYULiHeLXln/VVhWK4vkhKUmc=; b=fT/nwBiGE67zpjQxpY9UxGqZT9b+/lWmhFrMT2AqKDfY/qLlTS89yISQUnLyMASJeA IZf4K0h0H9num9H0Z7yWthhJ/MlusWb8yOZDWpWkWM47jSRBnqbz+GWBM/SqP1Ii2g9I XMr2k1CiodjH0GzVzh6+KdKoFIQXhvQBfijxkN6EIxgY3REQWUwDQxyouf4PBjGQSr20 CG49Iv2+EwypG3GRuvVPbb/ywzTCnu9pgJ/eqluqRA3h1Fd5LmJa/gLsUyltxv2o3MYt bn0EexDXcWFanzbiIctSfpAXdj9jILw265jSGLtMPjusMvzuvOy6icxJxkRfu5hCuHef 8Tng== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=b71LtaSQOEalI7Wb6oIYULiHeLXln/VVhWK4vkhKUmc=; b=V5rK63IQ0RCDNCtJx9BKXZC4hC+tip7ssUQisy4J8QUt4Nggthz9bGxRz6NIeO9e2e He/9Ob/882+SykbbX7arJCFXsxPuxkQzjIEjG9ufterorav/TgX4qr6yFMPHfnS+cP0V o+f5ufyBYUbwsqVe2x7FMOvQvSqyG3xQEHh5HtFhSjVgkAWCjpttogSZKrtjpqwI/0Gt H+BCz5DGEHJFI2Bh/dPZd65ISeKMGUvhY/ugcvlHQJQOJb8ZrJ8PRePoUtDuVd4ZpEBS dXeK7ngCW/nWa0KUOvSwdr97oiQmFgICVFrDGzB8xaagBplvZI2SK6fUr+jtaX+scZRQ ecGQ== X-Gm-Message-State: AOAM530uzIvkdQ0aSIBjvtzDdp5iJGXioBVUDg74//GnX1mlRu5ZKO42 iiVwaChjI41hBHaGjNGps9tJgQP5R3i9WwdO9Hk= X-Google-Smtp-Source: ABdhPJxBFASWnHLu4/DydbhtQFlH0qnVY3yYAKNLdfEArnLeowEF3WxjaeKW25A/4KAob5s02n/n9XA9VwTJL8OpIOs= X-Received: by 2002:a05:6512:2010:: with SMTP id a16mr11344288lfb.38.1623122032820; Mon, 07 Jun 2021 20:13:52 -0700 (PDT) MIME-Version: 1.0 References: <20210521182104.18273-1-kuniyu@amazon.co.jp> In-Reply-To: From: Alexei Starovoitov Date: Mon, 7 Jun 2021 20:13:41 -0700 Message-ID: Subject: Re: [PATCH v7 bpf-next 00/11] Socket migration for SO_REUSEPORT. To: Daniel Borkmann , Eric Dumazet Cc: Kuniyuki Iwashima , "David S . Miller" , Jakub Kicinski , Eric Dumazet , Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Benjamin Herrenschmidt , Kuniyuki Iwashima , bpf , Network Development , LKML , neal Cardwell , Yuchung Cheng Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 25, 2021 at 11:42 PM Daniel Borkmann wrote: > > On 5/21/21 8:20 PM, Kuniyuki Iwashima wrote: > > The SO_REUSEPORT option allows sockets to listen on the same port and to > > accept connections evenly. However, there is a defect in the current > > implementation [1]. When a SYN packet is received, the connection is tied > > to a listening socket. Accordingly, when the listener is closed, in-flight > > requests during the three-way handshake and child sockets in the accept > > queue are dropped even if other listeners on the same port could accept > > such connections. > > > > This situation can happen when various server management tools restart > > server (such as nginx) processes. For instance, when we change nginx > > configurations and restart it, it spins up new workers that respect the new > > configuration and closes all listeners on the old workers, resulting in the > > in-flight ACK of 3WHS is responded by RST. > > > > To avoid such a situation, users have to know deeply how the kernel handles > > SYN packets and implement connection draining by eBPF [2]: > > > > 1. Stop routing SYN packets to the listener by eBPF. > > 2. Wait for all timers to expire to complete requests > > 3. Accept connections until EAGAIN, then close the listener. > > > > or > > > > 1. Start counting SYN packets and accept syscalls using the eBPF map. > > 2. Stop routing SYN packets. > > 3. Accept connections up to the count, then close the listener. > > > > In either way, we cannot close a listener immediately. However, ideally, > > the application need not drain the not yet accepted sockets because 3WHS > > and tying a connection to a listener are just the kernel behaviour. The > > root cause is within the kernel, so the issue should be addressed in kernel > > space and should not be visible to user space. This patchset fixes it so > > that users need not take care of kernel implementation and connection > > draining. With this patchset, the kernel redistributes requests and > > connections from a listener to the others in the same reuseport group > > at/after close or shutdown syscalls. > > > > Although some software does connection draining, there are still merits in > > migration. For some security reasons, such as replacing TLS certificates, > > we may want to apply new settings as soon as possible and/or we may not be > > able to wait for connection draining. The sockets in the accept queue have > > not started application sessions yet. So, if we do not drain such sockets, > > they can be handled by the newer listeners and could have a longer > > lifetime. It is difficult to drain all connections in every case, but we > > can decrease such aborted connections by migration. In that sense, > > migration is always better than draining. > > > > Moreover, auto-migration simplifies user space logic and also works well in > > a case where we cannot modify and build a server program to implement the > > workaround. > > > > Note that the source and destination listeners MUST have the same settings > > at the socket API level; otherwise, applications may face inconsistency and > > cause errors. In such a case, we have to use the eBPF program to select a > > specific listener or to cancel migration. > > > > Special thanks to Martin KaFai Lau for bouncing ideas and exchanging code > > snippets along the way. > > > > > > Link: > > [1] The SO_REUSEPORT socket option > > https://lwn.net/Articles/542629/ > > > > [2] Re: [PATCH 1/1] net: Add SO_REUSEPORT_LISTEN_OFF socket option as drain mode > > https://lore.kernel.org/netdev/1458828813.10868.65.camel@edumazet-glaptop3.roam.corp.google.com/ > > This series needs review/ACKs from TCP maintainers. Eric/Neal/Yuchung please take > a look again. Eric, I've looked through bpf and tcp changes and they don't look scary at all. I think the feature is useful and a bit of extra complexity is worth it. So please review tcp bits to make sure we didn't miss anything. Thanks!