Re: [Qemu-devel] jumbo frames: needing some help

[Anthony Liguori <anthony@codemonkey.ws>]

Martin Rauh wrote:
> Anthony Liguori wrote:
>> martin.rauh@uni-ulm.de wrote:
>>> Hello, everyone!
>>>
>>> Sorry for the inconvenience, but as a part of my diploma thesis, I 
>>> am creating a virtual NIC for QEMU, in order to support a new 
>>> cluster OS of the university. (Saving the overhead caused by 
>>> emulating real hardware, it is not emulating an existing NIC.) 
>>> Anyway, now it seems to be working correctly, except for handling 
>>> jumbo frames, which I have to make available.
>>
>> You would have to post your patch.  We seem to be able to handle 
>> jumbo frames nicely with virtio-net.
>>
>> BTW, are you aware of virtio-net?  It has all of the properties that 
>> you are describing and it already exists for Linux and Windows.
>>
> No, I didn't know about virtio-net. Presumably it would be better to 
> support this virtio-net in our OS, but I think there's not enough time 
> left to develop a new driver now. I will recommend this for further 
> proceeding, thank you for this hint!
>
> http://home.vrweb.de/mrauh/testnic.c
> Here is the source file of my virtual NIC, which I modelled on then 
> NE2000.c, but it is probably not very nice to read. I used 
> qemu_send_packet for sending and registered my testnic_receive 
> function via qemu_new_vlan_client. Do you agree in principle to this 
> approach, in terms of proceeding jumbo frames?

Well if you don't have a patch to vl.c, that's probably your problem.  
There are a number of spots in the VLAN send functions that use buffers 
of 4096.  You won't be able to receive a packet larger than that.

Regards,

Anthony Liguori

> Thanks!
>
> Martin Rauh.
>
>