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Date: Thu, 15 Oct 2009 17:48:19 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: [Qemu-devel] Re: Raw vs. tap
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: kvm-devel <kvm@vger.kernel.org>, qemu-devel@nongnu.org, Paul Brook <paul@codesourcery.com>, Jens Osterkamp <jens@linux.vnet.ibm.com>, Sridhar Samudrala <sri@us.ibm.com>

On Thu, Oct 15, 2009 at 10:18:18AM -0500, Anthony Liguori wrote:
> Michael S. Tsirkin wrote:
>> On Thu, Oct 15, 2009 at 08:32:03AM -0500, Anthony Liguori wrote:
>>   
>>> Michael S. Tsirkin wrote:
>>>     
>>>> On Wed, Oct 14, 2009 at 05:53:56PM -0500, Anthony Liguori wrote:
>>>>         
>>>>> I would be much more inclined to consider  taking raw and 
>>>>> improving the performance long term if guest<->host  networking 
>>>>> worked.  This appears to be a fundamental limitation though  and 
>>>>> I think it's something that will forever plague users if we 
>>>>> include  this feature.
>>>>>             
>>>> In fact, I think it's fixable with a raw socket bound to a macvlan.
>>>> Would that be enough?
>>>>         
>>> What setup does that entail on the part of a user?  Wouldn't we be 
>>> back  to square one wrt users having to run archaic networking 
>>> commands in  order to set things up?
>>>     
>>
>> Unlike bridge, qemu could set up macvlan without disrupting
>> host networking. The only issue would be cleanup if qemu
>> is killed.
>>   
>
> But this would require additional features in macvlan, correct?

Not sure: what is the "this" that you are talking about.
It can already be set up without disturbing host networking.

> This also only works if a guest uses the mac address assigned to it,  
> correct?  If a guest was bridging the virtual nic, this would all come  
> apart?

Hmm, you could enable promisc mode, but generally this is true:
if you require bridging, use a bridge.

> Regards,
>
> Anthony Liguori