Re: [Qemu-devel] [PATCH v6 4/4] Add support for net bridge

[Corey Bryant]

On 12/19/2011 06:15 PM, Anthony Liguori wrote:
> On 12/19/2011 04:55 PM, Corey Bryant wrote:
> > > > diff --git a/net.c b/net.c
> > > > index f7bebf8..9296224 100644
> > > > --- a/net.c
> > > > +++ b/net.c
> > > > @@ -952,6 +952,14 @@ static const struct {
> > > > .type = QEMU_OPT_STRING,
> > > > .help = "script to shut down the interface",
> > > > }, {
> > > > + .name = "br",
> > > > + .type = QEMU_OPT_STRING,
> > > > + .help = "bridge name",
> > > > + }, {
> > >
> > > I don't think passing br= makes a whole of sense for -net tap. I think
> > > it would make more sense to make sure that helper could take a shell
> > > string so you could do:
> > >
> > > -netdev tap,helper="/usr/libexec/qemu-bridge-helper --br=br0"
> > >
> > > Regards,
> > >
> > > Anthony Liguori
> >
> > Ok but do you think the -net bridge options should remain as-is? It
> > seems like
> > execution of the helper should be consistent. Here are the current
> > options for
> > -net bridge:
> >
> > -net bridge,helper=/usr/local/libexec/qemu-bridge-helper,br=br0
>
> Yes. -net bridge is syntactic sugar for -net tap with specific knowledge
> of the qemu-bridge-helper.
>
> If someone wrote a 'qemu-openvswitch-helper' then you could imagine a
> '-net openvswitch' option that passed a bunch of openvswitch specific
> arguments.
>
> Regards,
>
> Anthony Liguori
>
> >

It seems like the helper should accept the following arguments:

--vnet-hdr --br=<bridge name> --fd=<unix fd>

(It already accept these, but the --br= and --fd= syntax aren't required 
at the moment.)

Then QEMU would only allow the following to be specified for -netdev tap:

-netdev tap,helper="/usr/libexec/qemu-bridge-helper"
or
-netdev tap,helper="/usr/libexec/qemu-bridge-helper --br=bridge"

and would ignore or reject --vnet-hdr and --fd=.  --vnet-hdr and --fd= 
would always be specified internally when the helper is exec'd.

--
Regards,
Corey