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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 72162C432C0 for ; Sun, 24 Nov 2019 22:48:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B24C207DD for ; Sun, 24 Nov 2019 22:48:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="W4P/kQPP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726962AbfKXWsb (ORCPT ); Sun, 24 Nov 2019 17:48:31 -0500 Received: from vps0.lunn.ch ([185.16.172.187]:54526 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726855AbfKXWsb (ORCPT ); Sun, 24 Nov 2019 17:48:31 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=wRUHE6GhEtEFZO0D62uFVoZL+soMx8piOGtC/s36Npo=; b=W4P/kQPPqmJuSMJJFgx70nRhCt ZB537MbE1GSmke8nk/+jHNKKMef+XmTiOQ0PAOQJ1MJU3VnvCWspofc3yGWuprVVMxINtLhUOopLR jLQX5ypChMY/OJ3dWPPX0yIH390Qilj7G2H7lB9JHr67R5cDAzeYj1scyBkAUfqcw1Xk=; Received: from andrew by vps0.lunn.ch with local (Exim 4.92.2) (envelope-from ) id 1iZ0g7-0005Ea-T8; Sun, 24 Nov 2019 23:48:27 +0100 Date: Sun, 24 Nov 2019 23:48:27 +0100 From: Andrew Lunn To: Vladimir Oltean Cc: f.fainelli@gmail.com, vivien.didelot@gmail.com, davem@davemloft.net, jakub.kicinski@netronome.com, netdev@vger.kernel.org Subject: Re: [PATCH net-next 1/3] net: dsa: Configure the MTU for switch ports Message-ID: <20191124224827.GD6009@lunn.ch> References: <20191123194844.9508-1-olteanv@gmail.com> <20191123194844.9508-2-olteanv@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191123194844.9508-2-olteanv@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > The CPU port is called with an MTU equal to the largest configured MTU > of the slave ports. The assumption is that the user might want to > sustain a bidirectional conversation with a partner over any switch > port. There is an assumption here that the MTU is enforced before the DSA header is applied on the egress patch. And MRU is also applied once the header is removed on ingress. I've no idea if this is true for all the switches we support in DSA. We should clearly document that if the switch need the header to be included, the function to set the MTU needs to add it. Andrew