Re: [Qemu-devel] [PATCH 0/4] net-bridge: rootless bridge support for qemu

[Anthony Liguori <aliguori@us.ibm.com>]

Arnd Bergmann wrote:
> On Thursday 05 November 2009, Anthony Liguori wrote:
>   
>>> It'd still install the default helper you've provided and use it by
>>> default, of course.
>>>   
>>>       
>> That's already how it behaves.  You can say -net 
>> bridge,helper=/usr/local/bin/my-helper
>>
>>     
>
> How about abstracting it further and not making the helper depend on
> bridge code. If we put the helper into netcf, we could make that
> a more generic '-net netcf,helper=/usr/bin/netcf-helper' target,
>   

Your suggestion on irc of doing -net tap,helper="/usr/bin/netcf-helper 
--name=foo" would also do the trick.  For qemu-bridge-helper, it would 
be -net tap,helper="/usr/libexec/qemu-bridge-helper --bridge=qemubr0".

I'd still want to have -net bridge syntax but it's just a syntatic 
wrapper (like -hda).  It's not something that would be used by libvirt, 
for instance.

Whether qemu-bridge-helper should live in qemu is another point to think 
about.   I think I would like to start with it being in qemu but then 
hope someone else pulls it into a separate project along with tunctl.

I think one can really make the argument that qemu should never allocate 
tap devices directly.  It should either get a file descriptor or call 
out to a helper to allocate a tap device and configure however is 
needed.  Both cases allow an unprivileged qemu whereas qemu creating a 
device directly clearly doesn't.

Maybe we could even eventually get rid of all of the tap code and 
replace it with a generic helper.

-- 
Regards,

Anthony Liguori