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

[Anthony Liguori <anthony@codemonkey.ws>]

On 12/20/2011 11:13 AM, Corey Bryant wrote:
>
>
> 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.

I don't know what you mean by "ignore or reject".  Just take whatever the helper 
string is, concat " --vnet-hdr --fd=" as appropriate, and execute it via /bin/sh.

Regards,

Anthony Liguori

>