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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 6FABFC433E0 for ; Mon, 25 May 2020 10:26:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 512D720787 for ; Mon, 25 May 2020 10:26:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=cumulusnetworks.com header.i=@cumulusnetworks.com header.b="TdT/jOYp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389766AbgEYK0t (ORCPT ); Mon, 25 May 2020 06:26:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36376 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389356AbgEYK0t (ORCPT ); Mon, 25 May 2020 06:26:49 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8507C061A0E for ; Mon, 25 May 2020 03:26:48 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id u12so11402637wmd.3 for ; Mon, 25 May 2020 03:26:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cumulusnetworks.com; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=nMuvRSUb4ALiiBXH2s5u47j7uY/+82nlefji0PdsqHk=; b=TdT/jOYp5cN158dXnRfMmu0WeMjAVZzB0VoCOeLtiiOKgMwNFvOyrj3bPucpXG9i98 DcQSmeXYpvdIUQ76QpOXEwjDIwVeBS2G5+anjM5hPsmCuDZia2pPpFQGsSLLTL/YzInG Umt6R9YimmRT5xGGQR6fRUGYY91nr/bSkGomQ= 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=nMuvRSUb4ALiiBXH2s5u47j7uY/+82nlefji0PdsqHk=; b=EybcvuzqU8TeCVuNvlnTA/U1XC2jPTvUgEn6pwPulJFIOJa0VAFUPms6lLRbQoltE8 7Wyr0o9vUpt/1+UCs2kE+XMgmiehMfHkx02P8XQ4IDB6alPDA9yaRGSx0X32PPDRkei3 ErOrEGZAJAtZa28fokd4A5X2dwT3kwx+EkZqxaRRvxgVA9gxk0V5Dzc/svy5nPgKghd9 9D5rXGw8JQbz0STVTrsoy+5RVEnfPD06BB93LusCbAP6jSHgSbYnXez5E5pMDdYa/jqz x9DznrqTaUFzwfC2EKM8Ff2ypUCgkyNZfkgLxyS2i0dZFx3V9ZaU/YOgedU+Tjzh4BIF z5wg== X-Gm-Message-State: AOAM5332umkdZ+XRRDhuIvAhS/+4gyQv+fjGB94Z4E2UsNxt9d1WXj70 muOFGMICBhafu+XZuOGMpY/CJw== X-Google-Smtp-Source: ABdhPJxXgGSlKW88yPOhBKqcx/KenoNx/MiflMYVJdNcY2yiQq7fFumKEeTy32ISIjvc3rahbZnVuw== X-Received: by 2002:a7b:c253:: with SMTP id b19mr25701091wmj.110.1590402407376; Mon, 25 May 2020 03:26:47 -0700 (PDT) Received: from [192.168.0.109] (84-238-136-197.ip.btc-net.bg. [84.238.136.197]) by smtp.gmail.com with ESMTPSA id 40sm17155504wrc.15.2020.05.25.03.26.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 May 2020 03:26:46 -0700 (PDT) Subject: Re: MRP netlink interface To: Michal Kubecek , netdev@vger.kernel.org Cc: Horatiu Vultur , roopa@cumulusnetworks.com, davem@davemloft.net, kuba@kernel.org, andrew@lunn.ch, UNGLinuxDriver@microchip.com, bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20200525112827.t4nf4lamz6g4g2c5@soft-dev3.localdomain> <20200525100322.sjlfxhz2ztrfjia7@lion.mk-sys.cz> From: Nikolay Aleksandrov Message-ID: <88bc4a98-c0c8-32df-142e-d4738fe0065a@cumulusnetworks.com> Date: Mon, 25 May 2020 13:26:45 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200525100322.sjlfxhz2ztrfjia7@lion.mk-sys.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 25/05/2020 13:03, Michal Kubecek wrote: > On Mon, May 25, 2020 at 11:28:27AM +0000, Horatiu Vultur wrote: > [...] >> My first approach was to extend the 'struct br_mrp_instance' with a field that >> contains the priority of the node. But this breaks the backwards compatibility, >> and then every time when I need to change something, I will break the backwards >> compatibility. Is this a way to go forward? > > No, I would rather say it's an example showing why passing data > structures as binary data via netlink is a bad idea. I definitely > wouldn't advice this approach for any new interface. One of the > strengths of netlink is the ability to use structured and extensible > messages. > >> Another approach is to restructure MRP netlink interface. What I was thinking to >> keep the current attributes (IFLA_BRIDGE_MRP_INSTANCE, >> IFLA_BRIDGE_MRP_PORT_STATE,...) but they will be nested attributes and each of >> this attribute to contain the fields of the structures they represents. >> For example: >> [IFLA_AF_SPEC] = { >> [IFLA_BRIDGE_FLAGS] >> [IFLA_BRIDGE_MRP] >> [IFLA_BRIDGE_MRP_INSTANCE] >> [IFLA_BRIDGE_MRP_INSTANCE_RING_ID] >> [IFLA_BRIDGE_MRP_INSTANCE_P_IFINDEX] >> [IFLA_BRIDGE_MRP_INSTANCE_S_IFINDEX] >> [IFLA_BRIDGE_MRP_RING_ROLE] >> [IFLA_BRIDGE_MRP_RING_ROLE_RING_ID] >> [IFLA_BRIDGE_MRP_RING_ROLE_ROLE] >> ... >> } >> And then I can parse each field separately and then fill up the structure >> (br_mrp_instance, br_mrp_port_role, ...) which will be used forward. >> Then when this needs to be extended with the priority it would have the >> following format: >> [IFLA_AF_SPEC] = { >> [IFLA_BRIDGE_FLAGS] >> [IFLA_BRIDGE_MRP] >> [IFLA_BRIDGE_MRP_INSTANCE] >> [IFLA_BRIDGE_MRP_INSTANCE_RING_ID] >> [IFLA_BRIDGE_MRP_INSTANCE_P_IFINDEX] >> [IFLA_BRIDGE_MRP_INSTANCE_S_IFINDEX] >> [IFLA_BRIDGE_MRP_INSTANCE_PRIO] >> [IFLA_BRIDGE_MRP_RING_ROLE] >> [IFLA_BRIDGE_MRP_RING_ROLE_RING_ID] >> [IFLA_BRIDGE_MRP_RING_ROLE_ROLE] >> ... >> } >> And also the br_mrp_instance will have a field called prio. >> So now, if the userspace is not updated to have support for setting the prio >> then the kernel will use a default value. Then if the userspace contains a field >> that the kernel doesn't know about, then it would just ignore it. >> So in this way every time when the netlink interface will be extended it would >> be backwards compatible. > > Silently ignoring unrecognized attributes in userspace requests is what > most kernel netlink based interfaces have been doing traditionally but > it's not really a good idea. Essentially it ties your hands so that you > can only add new attributes which can be silently ignored without doing > any harm, otherwise you risk that kernel will do something different > than userspace asked and userspace does not even have a way to find out > if the feature is supported or not. (IIRC there are even some places > where ignoring an attribute changes the nature of the request but it is > still ignored by older kernels.) > > That's why there have been an effort, mostly by Johannes Berg, to > introduce and promote strict checking for new netlink interfaces and new > attributes in existing netlink attributes. If you don't have strict > checking for unknown attributes enabled yet, there isn't much that can > be done for already released kernels but I would suggest to enable it as > soon as possible. > > Michal > +1, we don't have strict checking for the bridge main af spec attributes, but you could add that for new nested interfaces that need to be parsed like the above