Re: [Qemu-devel] [PATCH] Make SLIRP Ethernet packets size to 64 bytes minimum

[Fabien Chouteau <chouteau@adacore.com>]

On 27/06/2011 17:39, Stefan Hajnoczi wrote:
> On Mon, Jun 27, 2011 at 3:23 PM, Fabien Chouteau <chouteau@adacore.com> wrote:
>> On 27/06/2011 15:50, Stefan Hajnoczi wrote:
>>> On Mon, Jun 27, 2011 at 1:41 PM, Fabien Chouteau <chouteau@adacore.com> wrote:
>>>>
>>>> Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
>>>> ---
>>>>  slirp/slirp.c |    4 ++--
>>>>  1 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> Any particular bug that this fixes?
>>>
>>> There have been 64 byte minimum padding patches to several emulated
>>> NICs.  There has also been discussion about where the best place to do
>>> this is.  Why is this patch necessary?
>>>
>>
>> This patch is necessary because some NICs are configured to drop short frames,
>> therefore the OS will not receive some of the packets generated by Qemu.
>>
>> There's a first patch to fix this issue:
>> http://git.savannah.gnu.org/cgit/qemu.git/commit/?id=dbf3c4b4baceb91eb64d09f787cbe92d65188813
>>
>> My patch fixes two other sources of short frames.
> 
> Thanks for the explanation.  I stepped back from the discussion on
> where the right place to fix this is last time around.  Now I'm
> wondering why do anything in slirp when the other sources (tap, ...)
> aren't padding to 64 bytes?

I think that packets generated by Qemu must follow RFC. For other sources, qemu
should keep original size when possible and put padding otherwise.

-- 
Fabien Chouteau