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=-2.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham 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 41F24C43381 for ; Tue, 19 Feb 2019 16:18:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD00321773 for ; Tue, 19 Feb 2019 16:18:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="UQOwFl3x" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729010AbfBSQSQ (ORCPT ); Tue, 19 Feb 2019 11:18:16 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:44994 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726110AbfBSQSQ (ORCPT ); Tue, 19 Feb 2019 11:18:16 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: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=mpl5tbOIkt7J6req3bI8EZJzZSmu0RA6k8jPlue9DmA=; b=UQOwFl3xMZJnc+ntAkPGQO6p3 6vm/e4C3ew6kvWWrk49pgahLFQ1bVikuyyBQIj81GygUUyj8YVZ+BEVozU2LDZqWEp1h//X/Rz8uP NW/N1K+qKioXZjtz5i/qFA4u0LhzwtNPywmrV1EjohkDWnCuL54MOIhU8ns3eXVCporVFh1OsocqB dUmS8QWs8eMq7qkd/gzU8WKBvdnmXbloiRtzLJ6Ja1jvOOxZklIVI9DuJgtMa0DNxqr+nn+P5dIuT 9mf02XTdGFW9XMO7Oz335HbTPER2l7LQ2H5+G+P1nYnGogO1gn/BTO07Ymu3XsN+uGQUtC8KCB0wb Q+jofq5AQ==; Received: from shell.armlinux.org.uk ([2002:4e20:1eda:1:5054:ff:fe00:4ec]:36888) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1gw85y-0006eJ-OY; Tue, 19 Feb 2019 16:18:10 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.89) (envelope-from ) id 1gw85w-00088B-Jm; Tue, 19 Feb 2019 16:18:08 +0000 Date: Tue, 19 Feb 2019 16:18:08 +0000 From: Russell King - ARM Linux admin To: Vivien Didelot Cc: Andrew Lunn , Florian Fainelli , Heiner Kallweit , "David S. Miller" , netdev@vger.kernel.org Subject: Re: [PATCH net-next v2 3/3] net: dsa: mv88e6xxx: default to multicast and unicast flooding Message-ID: <20190219161808.6hlfdhb7yibdyg33@shell.armlinux.org.uk> References: <20190217163114.yomawlljyxlqy3ob@shell.armlinux.org.uk> <20190218125345.eq3mhmgsmgm7jmem@shell.armlinux.org.uk> <20190219110537.GD27578@t480s.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190219110537.GD27578@t480s.localdomain> User-Agent: NeoMutt/20170113 (1.7.2) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Feb 19, 2019 at 11:05:37AM -0500, Vivien Didelot wrote: > Hi Russell, > > On Mon, 18 Feb 2019 12:53:45 +0000, Russell King - ARM Linux admin wrote: > > On Sun, Feb 17, 2019 at 04:32:40PM +0000, Russell King wrote: > > > Switches work by learning the MAC address for each attached station by > > > monitoring traffic from each station. When a station sends a packet, > > > the switch records which port the MAC address is connected to. > > > > > > With IPv4 networking, before communication commences with a neighbour, > > > an ARP packet is broadcasted to all stations asking for the MAC address > > > corresponding with the IPv4. The desired station responds with an ARP > > > reply, and the ARP reply causes the switch to learn which port the > > > station is connected to. > > > > > > With IPv6 networking, the situation is rather different. Rather than > > > broadcasting ARP packets, a "neighbour solicitation" is multicasted > > > rather than broadcasted. This multicast needs to reach the intended > > > station in order for the neighbour to be discovered. > > > > > > Once a neighbour has been discovered, and entered into the sending > > > stations neighbour cache, communication can restart at a point later > > > without sending a new neighbour solicitation, even if the entry in > > > the neighbour cache is marked as stale. This can be after the MAC > > > address has expired from the forwarding cache of the DSA switch - > > > when that occurs, there is a long pause in communication. > > Thank you for the very informative message above. > > > > Our DSA implementation for mv88e6xxx switches has defaulted to having > > > multicast and unicast flooding disabled. As per the above description, > > > this is fine for IPv4 networking, since the broadcasted ARP queries > > > will be sent to and received by all stations on the same network. > > > However, this breaks IPv6 very badly - blocking neighbour solicitations > > > and later causing connections to stall. > > > > > > The defaults that the Linux bridge code expect from bridges are that > > > unknown unicast frames and unknown multicast frames are flooded to > > > all stations, which is at odds to the defaults adopted by our DSA > > > implementation for mv88e6xxx switches. > > > > > > This commit enables by default flooding of both unknown unicast and > > > unknown multicast frames. This means that mv88e6xxx DSA switches now > > > behave as per the bridge(8) man page, and IPv6 works flawlessly through > > > such a switch. > > > > Thinking about this a bit more, this approach probably isn't the best. > > If we have a port that goes through this life-cycle: > > > > 1. assigned to a bridge > > 2. configured not to flood > > 3. reassigned to a new bridge > > > > the port will retain its settings from the first bridge, which will be > > at odds with the settings that the Linux bridge code expects and the > > settings visible to the user. > > > > So, how about this, which basically reverts this patch and applies the > > flood settings each time a port joins a bridge, and clears them when > > the port leaves a bridge. > > Isn't the bridge code programming flooding on the port correctly on leave/join, > because the BR_*FLOOD flags have been learned? I would expect that. If you're asking whether the bridge code sends a SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS message on leave/join, it seems that it does not. There is only one place in the bridge code that this message is generated, that is in net/bridge/br_switchdev.c br_switchdev_set_port_flag(). That is called from one place in the bridge code, which is br_set_port_flag() in net/bridge/br_netlink.c, which is in response to a RTM_SETLINK netlink message where the bridge code processes all the various bridge link options. There appears to be no call when adding or removing an interface to/ from a bridge. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up