From: Stefan Richter <stef...@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: net...@vger.kernel.org > CC: linux1394-de...@lists.sourceforge.net > CC: Jarod Wilson <ja...@redhat.com> > Signed-off-by: Stefan Richter <stef...@s5r6.in-berlin.de> Applied.
