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=-4.3 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 62B32C433E0 for ; Sat, 23 Jan 2021 05:18:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C52923AF8 for ; Sat, 23 Jan 2021 05:18:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726708AbhAWFRt (ORCPT ); Sat, 23 Jan 2021 00:17:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45646 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726426AbhAWFRY (ORCPT ); Sat, 23 Jan 2021 00:17:24 -0500 Received: from mail-oo1-xc29.google.com (mail-oo1-xc29.google.com [IPv6:2607:f8b0:4864:20::c29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94C01C061786; Fri, 22 Jan 2021 21:16:44 -0800 (PST) Received: by mail-oo1-xc29.google.com with SMTP id u7so1345916ooq.0; Fri, 22 Jan 2021 21:16:44 -0800 (PST) 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=zxNG662Tpnsoz8s5rDmsMzt/BLhFhjnXV6eLd4EYb9o=; b=OCm+4WEKTHVXtK6/TX7smrp79P/GGOR+w/7KiDo+8jeq/ksAy3rxssV1CuJv6tuYRl p/AO5XsNXHgW2UOv1LjNUy9jyWYbacgs8146zP5RAQMwQaqZUA1i9cG4embLRK4R0loy wmYN/xM2gMJOdX1ZsfjMYVohVMn6dGF3t1mDM/MU+TyX1a41Z8Asv1xFhaPkiztuxYOJ uiHI7g1FFfKkgDaqzWQXf0NpL1tBARdtCv8A6VMZjiVCLg1OAmzEeOzXpuwqMUuJOWVO E750pIbTaJ2CZXUxdY8Ex3g0JqKMUYhbBGDr4sMLnHictC8UXeMGtGB5K+dp7Z/v3w+5 g9Ag== 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=zxNG662Tpnsoz8s5rDmsMzt/BLhFhjnXV6eLd4EYb9o=; b=nkaObXN27mjp4XvW7kYn6qaaoqJgDqe6da9FrA02OH7RWCS71j8OlIncnSr/NJinWz 6EUwr6jhcNkpajh3DFFifp2kvskU8f5aG7mZvJvy5CfoVYORtH2JEBqiZnud1EMEs7CL RcaIcOJUtdnK/DGJt4Ivcka24/zJ2NDdv4X105Co1oJ6bGEdmUgcaL+/J98k0biGTOTT 39BiQL4QyLmckJ/C+Jrv1OVXKzd7l30EBalHzIquKstXkeTMy8zGjan27SdN998M/Fq2 c7bqslauz4Iy9wTx1TEBp/ydV3ovALTJR5MXayT0VCpGqLrh02x1QlxeFVOzsIOwSY+u Y13Q== X-Gm-Message-State: AOAM533hA5ovcNIg1U7fPGrIeJXLLEfU7JUNaSrGvojjQxA3iZ3/Bk2M KuP/9PBb+MXYakKaGIe+Rww= X-Google-Smtp-Source: ABdhPJxA+4+j4HTMeDWLI8zan6VNkVXWGoDLVeWMHezRa95zOtEuJmLY0QZf0uyYNHswa/3PTASX8w== X-Received: by 2002:a4a:52d1:: with SMTP id d200mr813555oob.64.1611379003994; Fri, 22 Jan 2021 21:16:43 -0800 (PST) Received: from Davids-MacBook-Pro.local ([8.48.134.50]) by smtp.googlemail.com with ESMTPSA id e14sm2628oou.19.2021.01.22.21.16.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Jan 2021 21:16:43 -0800 (PST) Subject: Re: [PATCH v3 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement. To: =?UTF-8?Q?Maciej_=c5=bbenczykowski?= Cc: Praveen Chaudhary , David Miller , Jakub Kicinski , corbet@lwn.net, Alexey Kuznetsov , Hideaki Yoshifuji , Linux NetDev , linux-doc@vger.kernel.org, Linux Kernel Mailing List , Zhenggen Xu References: <20210119212959.25917-1-pchaudhary@linkedin.com> <1cc9e887-a984-c14a-451c-60a202c4cf20@gmail.com> From: David Ahern Message-ID: Date: Fri, 22 Jan 2021 22:16:41 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/22/21 9:02 PM, Maciej Żenczykowski wrote: > Why can't we get rid of the special case for 0 and simply make 1024 the > default value? That would work too. > > As for making it an RA option: it's not clear how that would work, the > use case I see for this is for example two connections to the internet, > of which one is clearly better (higher throughput, lower latency, lower > packet loss, etc) then the other. > > The upstream routers would have to somehow coordinate with each other > the metric values... that seems impossible to achieve in practice - > unless they do something like report expected down/up > bandwidth, latency, etc...  While some sort of policy on the machine > itself seems much more feasible (for example wired interface > wireless > interface > cell interface or something like that) I was thinking the admin of the network controls the RAs and knows which paths are preferred over the admin of the node receiving the RA (not practical for a mobile setup with cell vs wifi, but is for a DC which is the driving use case). But it takes an extension to IPv6/ndisc to add metric as an RA option, so not realistic in a reasonable time frame.