Subject: Re: [PATCH 1/2] 8139too: Allow setting MTU larger than 1500

From: Alban <[email-masked]>
Date: Fri, 21 Nov 2014 14:58:53 +0100

On Fri, 21 Nov 2014 00:34:34 +0000
Ben Hutchings <[email-masked]> wrote:

> On Sat, 2014-11-08 at 12:48 +0100, Alban Bedel wrote:
> > Replace the default ndo_change_mtu callback with one that allow
> > setting MTU that the driver can handle.
> > 
> > Signed-off-by: Alban Bedel <[email-masked]>
> > ---
> >  drivers/net/ethernet/realtek/8139too.c | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/realtek/8139too.c
> > b/drivers/net/ethernet/realtek/8139too.c index 007b38c..8387de9
> > 100644 --- a/drivers/net/ethernet/realtek/8139too.c
> > +++ b/drivers/net/ethernet/realtek/8139too.c
> > @@ -185,6 +185,9 @@ static int debug = -1;
> >  /* max supported ethernet frame size -- must be at least
> > (dev->mtu+14+4).*/ #define MAX_ETH_FRAME_SIZE	1536
> >  
> > +/* max supported payload size */
> > +#define MAX_ETH_DATA_SIZE	(MAX_ETH_FRAME_SIZE - ETH_HLEN -
> > ETH_FCS_LEN)
> [...]
> 
> Does this maximum still allow for VLAN tags, or should it use
> VLAN_ETH_HLEN instead of ETH_HLEN?

That might well be as the VLAN code seems to assume that the physical
device can handle frames of MTU + VLAN_HLEN bytes. I can fix it, but to
me it seems like the VLAN code should be fixed to respect the physical
device MTU.

Alban