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

[Corey Bryant <coreyb@linux.vnet.ibm.com>]

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