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Date: Tue, 08 Jun 2010 16:25:49 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] configure: add an option to disable vlans
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org, Paul Brook <paul@codesourcery.com>, "Michael S. Tsirkin" <mst@redhat.com>

On 06/08/10 15:02, Anthony Liguori wrote:
> On 06/08/2010 06:09 AM, 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.
>> -netdev socket seems to be supported. No?
>
> Sure, but it's of limited utility in the absence of vlans. A typical
> thing to do with -net socket would be to launch one instance of qemu
> with -net user, -net socket, and -net nic. Another qemu would be
> launched with -net socket and -net nic connected to the previous
> instance. Now you've got a working virtual network with external access.
>
> -netdev socket alone won't get you this.

I see three possible options to handle this.

   (1) Write a hub (or morph the current vlan code into this).  Then
       you can do something like:

             qemu -netdev socket,id=p1 \
                  -netdev user,id=p2   \
                  -netdev dump,id=p3 \
                  -switch peer=p1,peer=p2,monitor=p3,port=p4 \
                  -device $nic,netdev=p4

   (2) Implement the same as external daemon which can be combined with
       -netdev socket.

   (3) Just point people who need this to the various virtual switch
       projects (vde, ...) they can use and drop vlan.

cheers,
   Gerd