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=-8.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 00F74C43381 for ; Sun, 17 Feb 2019 14:27:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C6AFE217F5 for ; Sun, 17 Feb 2019 14:27:26 +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="HK97tG1t" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727489AbfBQO1Z (ORCPT ); Sun, 17 Feb 2019 09:27:25 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:38288 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725795AbfBQO1Z (ORCPT ); Sun, 17 Feb 2019 09:27:25 -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=6GdFsh3hF4P27bgVf6jeJacGVF0Qwa8aiSUM/j//CEc=; b=HK97tG1tQpYgmmWTQ76aWxCCL mG2Fr2HKhGbl4moLGiEdT5sDShV2NIhZcs6yRk2uYR+lLbAL8OZoa0XJVJZpB+FHbYfKfolByMddj NWT6Kptv4n2ueZkJeMQe+c4muLRa+e47I/wzEppmxOxgK0iM28vh+V9ihiR6fyzU8hheAIssQ3g4e qjU7CgmGMT52XtDuXNIRBOJBqFT0Admnh3vGGGYZHAK40zFjGzwj79dLqEt/lqdL7nD+l14wGIbQR PUmivmLpZsiZB+lEoZ3OxUNRxXycWK5lKX+mgxUv5L8Uxduu6H3F2fj6fioEkLVrCe2Mskn3/Wiut Gh3s4EPfA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:51176) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1gvNPa-0000fL-C6; Sun, 17 Feb 2019 14:27:18 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.89) (envelope-from ) id 1gvNPY-0006Li-7M; Sun, 17 Feb 2019 14:27:16 +0000 Date: Sun, 17 Feb 2019 14:27:16 +0000 From: Russell King - ARM Linux admin To: Andrew Lunn , Florian Fainelli , Vivien Didelot Cc: "David S. Miller" , netdev@vger.kernel.org Subject: Re: [PATCH net-next 3/3] net: dsa: mv88e6xxx: defautl to multicast and unicast flooding Message-ID: <20190217142716.gsrq5k2gnw3hsnhu@shell.armlinux.org.uk> References: <20190217142414.cjtmpi5y2l5rtdlb@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Sun, Feb 17, 2019 at 02:25:17PM +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. > > 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. Note that there is the open question whether this affects the case where each port is used as a separate network interface: that case has not yet been tested. > > Signed-off-by: Russell King > --- > drivers/net/dsa/mv88e6xxx/chip.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c > index b75a865a293d..eb5e3d88374f 100644 > --- a/drivers/net/dsa/mv88e6xxx/chip.c > +++ b/drivers/net/dsa/mv88e6xxx/chip.c > @@ -2144,13 +2144,14 @@ static int mv88e6xxx_setup_message_port(struct mv88e6xxx_chip *chip, int port) > static int mv88e6xxx_setup_egress_floods(struct mv88e6xxx_chip *chip, int port) > { > struct dsa_switch *ds = chip->ds; > - bool flood; > > - /* Upstream ports flood frames with unknown unicast or multicast DA */ > - flood = dsa_is_cpu_port(ds, port) || dsa_is_dsa_port(ds, port); > + /* Linux bridges are expected to flood unknown multicast and > + * unicast frames to all ports - as per the defaults specified > + * in the iproute2 bridge(8) man page. Not doing this causes > + * stalls and failures with IPv6 over Marvell bridges. */ > if (chip->info->ops->port_set_egress_floods) > return chip->info->ops->port_set_egress_floods(chip, port, > - flood, flood); > + true, true); > > return 0; > } > -- > 2.7.4 > > -- 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