From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941485AbcJZV34 (ORCPT ); Wed, 26 Oct 2016 17:29:56 -0400 Received: from shards.monkeyblade.net ([184.105.139.130]:42268 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S941309AbcJZV3w (ORCPT ); Wed, 26 Oct 2016 17:29:52 -0400 Date: Wed, 26 Oct 2016 17:29:15 -0400 (EDT) Message-Id: <20161026.172915.2201926740859755129.davem@davemloft.net> To: stefanr@s5r6.in-berlin.de Cc: netdev@vger.kernel.org, linux1394-devel@lists.sourceforge.net, jarod@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next 2/2] firewire: net: set initial MTU = 1500 unconditionally, fix IPv6 on some CardBus cards From: David Miller In-Reply-To: <20161023163056.6bc38610@kant> References: <20161023011824.GE32569@redhat.com> <20161023162903.4166a35d@kant> <20161023163056.6bc38610@kant> X-Mailer: Mew version 6.7 on Emacs 25.1 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 26 Oct 2016 14:29:16 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Stefan Richter Date: Sun, 23 Oct 2016 16:30:56 +0200 > firewire-net, like the older eth1394 driver, reduced the initial MTU to > less than 1500 octets if the local link layer controller's asynchronous > packet reception limit was lower. > > This is bogus, since this reception limit does not have anything to do > with the transmission limit. Neither did this reduction affect the TX > path positively, nor could it prevent link fragmentation at the RX path. > > Many FireWire CardBus cards have a max_rec of 9, causing an initial MTU > of 1024 - 16 = 1008. RFC 2734 and RFC 3146 allow a minimum max_rec = 8, > which would result in an initial MTU of 512 - 16 = 496. On such cards, > IPv6 could only be employed if the MTU was manually increased to 1280 or > more, i.e. IPv6 would not work without intervention from userland. > > We now always initialize the MTU to 1500, which is the default according > to RFC 2734 and RFC 3146. > > On a VIA VT6316 based CardBus card which was affected by this, changing > the MTU from 1008 to 1500 also increases TX bandwidth by 6 %. > RX remains unaffected. > > CC: netdev@vger.kernel.org > CC: linux1394-devel@lists.sourceforge.net > CC: Jarod Wilson > Signed-off-by: Stefan Richter Applied. From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next 2/2] firewire: net: set initial MTU = 1500 unconditionally, fix IPv6 on some CardBus cards Date: Wed, 26 Oct 2016 17:29:15 -0400 (EDT) Message-ID: <20161026.172915.2201926740859755129.davem@davemloft.net> References: <20161023011824.GE32569@redhat.com> <20161023162903.4166a35d@kant> <20161023163056.6bc38610@kant> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux1394-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, jarod@redhat.com To: stefanr@s5r6.in-berlin.de Return-path: In-Reply-To: <20161023163056.6bc38610@kant> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux1394-devel-bounces@lists.sourceforge.net List-Id: netdev.vger.kernel.org From: Stefan Richter Date: Sun, 23 Oct 2016 16:30:56 +0200 > firewire-net, like the older eth1394 driver, reduced the initial MTU to > less than 1500 octets if the local link layer controller's asynchronous > packet reception limit was lower. > > This is bogus, since this reception limit does not have anything to do > with the transmission limit. Neither did this reduction affect the TX > path positively, nor could it prevent link fragmentation at the RX path. > > Many FireWire CardBus cards have a max_rec of 9, causing an initial MTU > of 1024 - 16 = 1008. RFC 2734 and RFC 3146 allow a minimum max_rec = 8, > which would result in an initial MTU of 512 - 16 = 496. On such cards, > IPv6 could only be employed if the MTU was manually increased to 1280 or > more, i.e. IPv6 would not work without intervention from userland. > > We now always initialize the MTU to 1500, which is the default according > to RFC 2734 and RFC 3146. > > On a VIA VT6316 based CardBus card which was affected by this, changing > the MTU from 1008 to 1500 also increases TX bandwidth by 6 %. > RX remains unaffected. > > CC: netdev@vger.kernel.org > CC: linux1394-devel@lists.sourceforge.net > CC: Jarod Wilson > Signed-off-by: Stefan Richter Applied. ------------------------------------------------------------------------------ The Command Line: Reinvented for Modern Developers Did the resurgence of CLI tooling catch you by surprise? Reconnect with the command line and become more productive. Learn the new .NET and ASP.NET CLI. Get your free copy! http://sdm.link/telerik