Re: [Qemu-devel] [PATCH] configure: add an option to disable vlans

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jun 08, 2010 at 08:03:33AM -0500, Anthony Liguori wrote:
> On 06/08/2010 07:13 AM, Michael S. Tsirkin wrote:
>> On Mon, Jun 07, 2010 at 04:57:09PM -0500, Anthony Liguori wrote:
>>    
>>> On 06/07/2010 04:37 PM, Anthony Liguori wrote:
>>>      
>>>> On 06/07/2010 03:58 PM, Michael S. Tsirkin wrote:
>>>>        
>>>>> On Mon, Jun 07, 2010 at 03:40:57PM -0500, Anthony Liguori wrote:
>>>>>          
>>>>>> On 06/07/2010 02:21 PM, Michael S. Tsirkin wrote:
>>>>>>            
>>>>>>> So I see two ways to go forward: switch default value in my patch,
>>>>>>> or disable vlans unconditionally.
>>>>>>>
>>>>>>>              
>>>>>> The problem with disabling vlans unconditionally is that you break -net
>>>>>> socket and -net dump.
>>>>>>
>>>>>> If we can come up with an alternative way to do these things, I'm all
>>>>>> for removing it.
>>>>>>            
>>>>> Hmm, I'll try to look at supporting -net socket in netdev.
>>>>> Does -net dump do anything that can't be done with tap+tcpdump?
>>>>>          
>>>> tap+tcpdump requires root privileges (even if you have a tap helper).
>>>>
>>>> Plus tcpdump doesn't help with slirp and -net dump is very useful for
>>>> debugging slirp.
>>>>        
>> Developer's need for root access for debugging seems a reasonable price to
>> pay to prevent user confusion and complexity that we have now.
>>    
>
> Removing vlans has the potential to break existing deployments.  That's  
> something we need to do very cautiously.

You mean you want to support both peer to peer and broadcast
indefinitely?

> What do we gain from removing vlan support today?
>
> Regards,
>
> Anthony Liguori

This would address the following issues:
- people configure vlans and get bad performance
- people run --help and see info on vlans instead of peer
- migration issues betwen vlan/non-vlan
- hotplug is broken for vlan nics


>>> Of course, you could add this functionality to netdev.  It's arguably
>>> better there too because then you can debug virtio-net+tap with full
>>> offload enabled (which you cannot do today).
>>>
>>> Regards,
>>>
>>> Anthony Liguori
>>>      
>> Care taking on it? I never even heard about -net dump before today.
>>
>>