[dpdk-dev] [PATCH 1/6] net/tap: use correct tap name

[Pascal Mazon]

On 01/31/2017 02:06 PM, Ferruh Yigit wrote:> On 1/31/2017 9:42 AM, 
Pascal Mazon wrote:
>> dev->data->name contains "net_tap", the device driver name.
>
> I see what patch does, just as a note to commit log:
>
> AFAIK, "dev->data->name" is device name, and for this case it is
> "net_tap#", like "net_tap0", "net_tap1" ...
>
> "dev->data_drv_name" is the driver name which is "net_tap"

Indeed, dev->data->name is the device name, looking like "net_tap#",
with number increasing for each vdev.
I'll put the following commit log line if that's ok:

     dev->data->name contains the device name, e.g. "net_tap0".

>
>> dev->data->dev_private->name contains the actual iface name,
>> e.g. "dtap0".
>
> Right, I agree this is correct comparing "dev->data->name"
>
> But the problem is pmd->name is per eth_dev.
>
> If I read code correct, for multiple queue support, each queue pair will
> create a tap device, so each needs a different name.
>
> So can't just use pmd->name. Need to create a name per queue pair, it
> can be combination of pmd->name + "_" + queue_id? Or can keep a name per
> queue pair, instead of eth_dev.
>
> What do you think?

Actually that's not exactly how it goes.
Adding a queue to a netdevice requires to open("/dev/net/tun") and setting
TUNSETIFF (through ioctl) on the resulting fd.
That's the important part: queues for a given tap device must set TUNSETIFF
with a common ifreq.ifr_name (in our case, pmd->name).

This is best explained in the kernel doc, there:

[1] 
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/tuntap.txt#n108

>
>>
>> In tun_alloc() especially, we want to use the latter. Otherwise the
>> netdevice would be wrongly named "net_tap". Furthermore, creating
>> several tap vdev would point to the same netdevice.
>>
>> In any case, it must to be consistent with the tun_alloc() call in
>> eth_dev_tap_create().
>>
>> Signed-off-by: Pascal Mazon <pascal.mazon at 6wind.com>
> <...>
>


--
Pascal Mazon
www.6wind.com