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From: Jarod Wilson <jarod@redhat.com>
To: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: "David S. Miller" <davem@davemloft.net>,
	netdev@vger.kernel.org, linux1394-devel@lists.sourceforge.net,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 2/2 v2] firewire: net: set initial MTU = 1500 unconditionally, fix IPv6 on some CardBus cards
Date: Mon, 24 Oct 2016 23:05:14 -0400	[thread overview]
Message-ID: <20161025030514.GM42084@redhat.com> (raw)
In-Reply-To: <20161024142613.29145f32@kant>

On Mon, Oct 24, 2016 at 02:26:13PM +0200, Stefan Richter wrote:
> 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 <jarod@redhat.com>
> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
> ---
> v2: use ETH_DATA_LEN, add comment

Acked-by: Jarod Wilson <jarod@redhat.com>

-- 
Jarod Wilson
jarod@redhat.com

  reply	other threads:[~2016-10-25  3:05 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-19  2:33 [PATCH net-next 0/6] net: use core MTU range checking everywhere Jarod Wilson
2016-10-19  2:33 ` [PATCH net-next 1/6] net: use core MTU range checking in USB NIC drivers Jarod Wilson
2016-10-19  2:33 ` [PATCH net-next 2/6] net: use core MTU range checking in wireless drivers Jarod Wilson
2016-10-19  7:38   ` Johannes Berg
2016-10-19 14:27     ` Jarod Wilson
2016-10-19 14:28       ` Johannes Berg
2016-10-19  2:33 ` [PATCH net-next 3/6] net: use core MTU range checking in WAN drivers Jarod Wilson
2016-10-21 12:04   ` Krzysztof Hałasa
2016-10-19  2:33 ` [PATCH net-next 4/6] net: use core MTU range checking in core net infra Jarod Wilson
2016-10-19 12:17   ` Jiri Benc
2016-10-19 14:51     ` Jarod Wilson
2016-10-19 13:55   ` Sabrina Dubroca
2016-10-19 14:40     ` Jarod Wilson
2016-10-19 15:28       ` Sabrina Dubroca
2016-10-19 15:46         ` Jarod Wilson
2016-10-19  2:33 ` [PATCH net-next 5/6] net: use core MTU range checking in virt drivers Jarod Wilson
2016-10-19 13:06   ` Aaron Conole
2016-10-19 13:59   ` Michael S. Tsirkin
2016-10-19 14:03     ` Michael S. Tsirkin
2016-10-19 14:17       ` Jarod Wilson
2016-10-19 14:15     ` Jarod Wilson
2016-10-19 14:07   ` Haiyang Zhang via Virtualization
2016-10-19 14:23     ` Jarod Wilson
2016-10-19 22:21   ` Shrikrishna Khare
2016-10-19  2:33 ` [PATCH net-next 6/6] net: use core MTU range checking in misc drivers Jarod Wilson
2016-10-19 14:37   ` Robin Holt
2016-10-19 16:05   ` Sabrina Dubroca
2016-10-19 22:38     ` Stefan Richter
2016-10-20  3:16       ` Jarod Wilson
     [not found]         ` <20161020031641.GJ18569-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-10-22  9:36           ` Stefan Richter
2016-10-22 18:51             ` Stefan Richter
2016-10-19 19:10 ` [PATCH net-next 0/6] net: use core MTU range checking everywhere David Miller
2016-10-19 19:29   ` Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 0/9] " Jarod Wilson
2016-10-20 17:55   ` [PATCH net-next v2 1/9] ethernet: use net core MTU range checking in more drivers Jarod Wilson
2016-10-20 17:55   ` [PATCH net-next v2 2/9] net: use core MTU range checking in USB NIC drivers Jarod Wilson
2016-10-20 17:55   ` [PATCH net-next v2 3/9] net: use core MTU range checking in wireless drivers Jarod Wilson
2016-10-20 18:22     ` Johannes Berg
2016-10-20 18:38       ` David Miller
2016-10-20 17:55   ` [PATCH net-next v2 4/9] net: use core MTU range checking in WAN drivers Jarod Wilson
2016-10-20 17:55   ` [PATCH net-next v2 5/9] net: use core MTU range checking in core net infra Jarod Wilson
2016-10-20 17:55   ` [PATCH net-next v2 6/9] net: use core MTU range checking in virt drivers Jarod Wilson
2016-10-20 18:05     ` Haiyang Zhang
2016-10-20 20:12       ` Kershner, David A
2016-10-20 20:23     ` Michael S. Tsirkin
2016-10-21  2:37       ` Jarod Wilson
2016-10-21  3:36         ` Michael S. Tsirkin
2016-10-21 13:24           ` Aaron Conole
2016-10-21 10:09     ` Wei Liu
2016-10-20 17:55   ` [PATCH net-next v2 7/9] net: use core MTU range checking in misc drivers Jarod Wilson
2016-10-21  6:52     ` Rémi Denis-Courmont
2016-10-21 16:22     ` Sebastian Reichel
     [not found]     ` <20161020175524.6184-8-jarod-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-10-22  7:17       ` [net-next,v2,7/9] " Sven Eckelmann
2016-10-22 19:16     ` [PATCH net-next v2 7/9] " Stefan Richter
2016-10-22 19:27       ` Stefan Richter
2016-10-23  1:18         ` Jarod Wilson
2016-10-23 14:29           ` [PATCH net-next 1/2] firewire: net: fix maximum possible MTU Stefan Richter
2016-10-23 14:30             ` [PATCH net-next 2/2] firewire: net: set initial MTU = 1500 unconditionally, fix IPv6 on some CardBus cards Stefan Richter
2016-10-24  1:50               ` Jarod Wilson
2016-10-24 12:26                 ` [PATCH net-next 2/2 v2] " Stefan Richter
2016-10-25  3:05                   ` Jarod Wilson [this message]
2016-10-26 21:29               ` [PATCH net-next 2/2] " David Miller
2016-10-29 20:16               ` [PATCH net-next] firewire: net: really fix maximum possible MTU Stefan Richter
2016-10-30  3:01                 ` David Miller
2016-10-24  1:50             ` [PATCH net-next 1/2] firewire: net: " Jarod Wilson
2016-10-26 21:29             ` David Miller
2016-10-20 17:55   ` [PATCH net-next v2 8/9] s390/net: use net core MTU range checking Jarod Wilson
2016-10-20 17:55   ` [PATCH net-next v2 9/9] ipv4/6: use core net " Jarod Wilson
2016-10-20 18:53   ` [PATCH net-next v2 0/9] net: use core MTU range checking everywhere David Miller

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