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=-5.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 5EF38C4360F for ; Tue, 26 Mar 2019 01:23:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 17EDA20863 for ; Tue, 26 Mar 2019 01:23:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553563399; bh=1z5jZLcbsuXG/n/Jogp39/oFMe3gjqNKKx4jP11VJt0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=w+Gnqn6Y8dccdcB6pl1UaVF80jp+HVBm1eYI/lljGcW9H6zU2E45peq1Ny7AT4sZb /YxolqSU8XhnR4+6oxThCBEDTvW0B9gcmhanq1CpD/y76p3yqzxa7ZWCj9l0pzua9e /+C74sL7bmLcGY4Qyi+a0S6i00emqV28TTqjqBPM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730681AbfCZBXS (ORCPT ); Mon, 25 Mar 2019 21:23:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:57272 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727412AbfCZBXQ (ORCPT ); Mon, 25 Mar 2019 21:23:16 -0400 Received: from localhost (li1825-44.members.linode.com [172.104.248.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0FC182084D; Tue, 26 Mar 2019 01:23:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553563396; bh=1z5jZLcbsuXG/n/Jogp39/oFMe3gjqNKKx4jP11VJt0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ntgpt/zT7niUMmUNxxnL2q8j1DMyeQHnq4GKOLbSI0xfZooSGFRZz7FkScFPsgCEI vERXXU0N4BjkAN5WMxcg8iiAK31q5+IhEe4TbxJ0oy+Bdl+it1oCoUOnFPWeQZGMVs KQVPbDpfq0QFjONgODd3duyBOlmUY+GENuoBklM8= Date: Tue, 26 Mar 2019 10:21:09 +0900 From: Greg KH To: Arnd Bergmann Cc: stable@vger.kernel.org, "David S. Miller" , Gerrit Renker , Eric Dumazet , Alexey Kuznetsov , Hideaki YOSHIFUJI , Neal Cardwell , Yuchung Cheng , Wei Wang , Ilya Lesokhin , Priyaranjan Jha , Soheil Hassas Yeganeh , Yafang Shao , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dccp@vger.kernel.org Subject: Re: [BACKPORT 4.4.y 18/25] tcp/dccp: drop SYN packets if accept queue is full Message-ID: <20190326012109.GD29420@kroah.com> References: <20190322154425.3852517-1-arnd@arndb.de> <20190322154425.3852517-19-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190322154425.3852517-19-arnd@arndb.de> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 22, 2019 at 04:44:09PM +0100, Arnd Bergmann wrote: > From: Eric Dumazet > > Per listen(fd, backlog) rules, there is really no point accepting a SYN, > sending a SYNACK, and dropping the following ACK packet if accept queue > is full, because application is not draining accept queue fast enough. > > This behavior is fooling TCP clients that believe they established a > flow, while there is nothing at server side. They might then send about > 10 MSS (if using IW10) that will be dropped anyway while server is under > stress. > > Signed-off-by: Eric Dumazet > Acked-by: Neal Cardwell > Acked-by: Yuchung Cheng > Signed-off-by: David S. Miller > (cherry picked from commit 5ea8ea2cb7f1d0db15762c9b0bb9e7330425a071) Also queued up for 4.9.y