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Date: Wed, 09 Dec 2009 13:39:21 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [PATCH, try 2] qemu/tap: add -net tap,dev= option
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To: Arnd Bergmann <arnd@arndb.de>
Cc: qemu-devel@nongnu.org

Arnd Bergmann wrote:
> In order to support macvtap, we need a way to select the actual
> tap endpoint. While it would be nice to pass it by network interface
> name, passing the character device is more flexible, and we can
> easily do both in the long run.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>   

This isn't really a generic thing and I dislike pretending it is.  This 
is specifically for macvtap.

If we were going to do this, I'd rather introduce a -net macvtap that 
actually allocated the interfaces (similar to how tap works).  The 
problem with this interface is that it's a two stage process.  You have 
to create an interface, then hand the name to qemu.  It would be just as 
easy to hand qemu an fd with a helper.

What's nice about -net tap is that with a little bit of setup 
(/etc/qemu-ifup), it Just Works.  -net tap,dev= does not share this 
property.

I think this is a good place where an exec helper would be a natural fit.

Regards,

Anthony Liguori