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=-5.6 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 9A30DC4363D for ; Fri, 25 Sep 2020 15:15:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4452320878 for ; Fri, 25 Sep 2020 15:15:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DdSHe4i1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728907AbgIYPP1 (ORCPT ); Fri, 25 Sep 2020 11:15:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728858AbgIYPP1 (ORCPT ); Fri, 25 Sep 2020 11:15:27 -0400 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2E3FC0613CE; Fri, 25 Sep 2020 08:15:26 -0700 (PDT) Received: by mail-wr1-x442.google.com with SMTP id c18so3972749wrm.9; Fri, 25 Sep 2020 08:15:26 -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=JVxu4r2WfZ7y1LJf1lPXgUWmvqhhajFSJ/ifVaATdHo=; b=DdSHe4i1OVUn7d80PT6kX2GPcvaa0zGrPv9fqjlAXJQ45zybYqzYVBdnPI+V2eq7Yn gj1fsEJuUyC6HEXsj8DH6rjm5k8bUD+rZfS6jr1ki8d25N0Z41x8Cjf09/CnDT/bvgPq UOwl9+GnCLzuyHMkgPhpyJa2avgRJVheKfUqueeEvK8DX4jKCQ6saat6IznEOKSxfhwo OVuzDjhTlLqCluB5qNOTbW6XRiT8N7TGyfiLNavImH5upmbSQtRFwCztmAz2JtoDPBAa him6IHWzexRUyClABTEKywmEka62PNAWOqA63ebNwZelgVRoj3dGZrpd1KZLaXCbn8b0 zCkA== 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=JVxu4r2WfZ7y1LJf1lPXgUWmvqhhajFSJ/ifVaATdHo=; b=t5uVDo3buMR0ge20H5xvmu06PDTBM85Y+X2McBcBNCctJ0sQs6z7YD6FWZ9ypTTXdy acJyz5N0IhoJE9kULOvIY6VGfjsOAqtEZ65VAVjMkAjkpIe9OiZWwLnru/9Q9GQif1RC C98oanxB/r0PEO3NCwDII7dGqv46qCeW7W1KqponfVza/uEzHshN/8y8tmB0TsHQudpJ gev4WFaboc8jfyqNj4FAVwELpjnBnelS2aGzYzxVPYFiE7BiM3+vHT/MtleUsXnPXBR/ /74WSqtkOmtS07JAKGOXO1UA14+sU6jd/Jm8IjhXMozH0RVmDm7IlEYbzHrI1DHeaQsC b9lw== X-Gm-Message-State: AOAM530fKHdNSUtTLmgutmu5MXheNtQck/b3ynSqv+sbur+ySjU4lTl0 ys4hVgSUNNNlnWWP1+FGws+TKH+ay2Q= X-Google-Smtp-Source: ABdhPJxpDkuiyFrjZGYvg4PEXQxV5HKOA8Mnu7I3KFbeTGgh2b8LDngftD3yoNpNKnMPjYnegx560g== X-Received: by 2002:adf:eb04:: with SMTP id s4mr5412634wrn.81.1601046925503; Fri, 25 Sep 2020 08:15:25 -0700 (PDT) Received: from [192.168.8.147] ([37.173.173.126]) by smtp.gmail.com with ESMTPSA id h186sm3258995wmf.24.2020.09.25.08.15.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Sep 2020 08:15:24 -0700 (PDT) Subject: Re: [PATCH bpf-next 2/6] bpf, net: rework cookie generator as per-cpu one To: Jakub Kicinski , Daniel Borkmann Cc: Eric Dumazet , ast@kernel.org, john.fastabend@gmail.com, netdev@vger.kernel.org, bpf@vger.kernel.org References: <20200925080020.013165a0@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> From: Eric Dumazet Message-ID: Date: Fri, 25 Sep 2020 17:15:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200925080020.013165a0@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 9/25/20 5:00 PM, Jakub Kicinski wrote: unlikely((val & (COOKIE_LOCAL_BATCH - 1)) == 0)) { > > Can we reasonably assume we won't have more than 4k CPUs and just > statically divide this space by encoding CPU id in top bits? This might give some food to side channel attacks, since this would give an indication of cpu that allocated the id. Also, I hear that some distros enabled 8K cpus.