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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 831F3C48BCD for ; Tue, 8 Jun 2021 17:49:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6866A610E5 for ; Tue, 8 Jun 2021 17:49:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233927AbhFHRvl (ORCPT ); Tue, 8 Jun 2021 13:51:41 -0400 Received: from mail-wr1-f48.google.com ([209.85.221.48]:33739 "EHLO mail-wr1-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233082AbhFHRvi (ORCPT ); Tue, 8 Jun 2021 13:51:38 -0400 Received: by mail-wr1-f48.google.com with SMTP id a20so22575190wrc.0 for ; Tue, 08 Jun 2021 10:49:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8VUcUNHL3JuSqy+zkLCk7TZMD9OSteZxhISOtRNVDjQ=; b=Rkv4RbY/1E+9cYKHD1E0VCGCJJ8FeA4zTISQEe7eaDnASxEiHmqhKpYX5ore5xvmKd qBsqhYwcgBZuOaSUmcYb6o+iTCOoctKY3yLPFLrhzgdmC677GwT+2xpcuZ2AX5O8CbID Y5P7LPwa9L91pKhqsZkACt7cyWinpUyu1bGFL9FzzXC614RQEmuKnXIVookASJs7cULS S+jMjIljXL4R0vm/AFwuAplXCJfVclcAyqnWssZ/JNSZhqqDwqcTXOKMWM9t5UvsyUxG nbqy7PGOt0CvMIsE3F0Gr2CHVRxXqW4NtHwW4Zf4fzby0tyM27MqfcYBtFFjU3Tj9l+P NBHQ== 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=8VUcUNHL3JuSqy+zkLCk7TZMD9OSteZxhISOtRNVDjQ=; b=Vg2lXAqNdx/+Omd18pfGSee/ddn5voQBSWYq70JRkKD7xKsfFTVwSeJUlX1YRINO16 4hNTrzMx3yBRsfc9etDLnn2oO2M2Py/jiNs5x/MWauiwVRiGyIJ3iUj4L7fCkbb5Y0x7 Bx5MGHVM/+Thhqt+XlM1MxTyg9lVlbh8oH1+TIzcITVLecOKpaXzn8eEvP47I3oqMYxn 3903RXCWhigQsOCUHm8taSENHbGfr2tILmqg3b7NOgQtXO2cel9UdKWqrcGbRCHqk+RN F6j/4KgJAkvJNbAPrs66Izb6fYrEmqdEKg9Pn2X16+KuNHp4Q3K4BHQ3jGxPYDZQ/x8A AxoA== X-Gm-Message-State: AOAM533Pei8yYD9bpQOmsM6EcxiFsck00v93Sh8QHkUn6SQ+W6sq/Fux iO/XZnkpT4XCarT2eg425K2AWNs4b0fvE6iHJb0XaA== X-Google-Smtp-Source: ABdhPJw3AXWRQHvemXMm9mHm72Hk/moNbFy9rPAbavS5t8/FbQE/HUYxi+rspRDnbpqKEpaBgYhgnMBG3s6lyQMDBxY= X-Received: by 2002:a5d:694b:: with SMTP id r11mr17324336wrw.168.1623174524512; Tue, 08 Jun 2021 10:48:44 -0700 (PDT) MIME-Version: 1.0 References: <20210521182104.18273-1-kuniyu@amazon.co.jp> In-Reply-To: From: Yuchung Cheng Date: Tue, 8 Jun 2021 10:48:06 -0700 Message-ID: Subject: Re: [PATCH v7 bpf-next 00/11] Socket migration for SO_REUSEPORT. To: Daniel Borkmann Cc: Kuniyuki Iwashima , "David S . Miller" , Jakub Kicinski , Eric Dumazet , Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Benjamin Herrenschmidt , Kuniyuki Iwashima , bpf@vger.kernel.org, netdev , LKML , Neal Cardwell 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. This looks to be a useful feature. What happens to migrating a passively fast-opened socket in the old listener but it has not yet been accepted (TFO is both a mini-socket and a full-socket)? It gets tricky when the old and new listener have different TFO key > > > > 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. > > Thanks, > Daniel