lkml.org 
[lkml]   [2016]   [Oct]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH net-next 2/2] firewire: net: set initial MTU = 1500 unconditionally, fix IPv6 on some CardBus cards
From
From: Stefan Richter <stefanr@s5r6.in-berlin.de>
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 <jarod@redhat.com>
> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

Applied.

\
 
 \ /
  Last update: 2016-10-26 23:30    [W:0.327 / U:0.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site