Re: [net-next rfc V3 7/9] macvtap: allow TUNSETIFF to createmultiqueue device

From: Michael S. Tsirkin
Date: Wed Jun 05 2013 - 06:42:40 EST


On Wed, Jun 05, 2013 at 02:36:30PM +0800, Jason Wang wrote:
> Though the queue were in fact created by open(), we still need to add this check
> to be compatible with tuntap which can let mgmt software use a single API to
> manage queues. This patch only validates the device name and moves the TUNSETIFF
> to a helper.
>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

The patch is OK, the description is confusing.
What you mean is simply:

Allow IFF_MULTI_QUEUE in TUNSETIFF for macvtap, to match
tun behaviour.

And if you put it like this, I would say make this
the last patch in the series, so userspace
can use IFF_MULTI_QUEUE to detect new versus old
behaviour.

> ---
> drivers/net/macvtap.c | 51 ++++++++++++++++++++++++++++++++++++++----------
> 1 files changed, 40 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index 5ccba99..14764cc 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -869,6 +869,7 @@ out:
> return ret;
> }
>
> +
> static struct macvlan_dev *macvtap_get_vlan(struct macvtap_queue *q)
> {
> struct macvlan_dev *vlan;

Please don't.

> @@ -887,6 +888,44 @@ static void macvtap_put_vlan(struct macvlan_dev *vlan)
> dev_put(vlan->dev);
> }
>
> +static int macvtap_set_iff(struct file *file, struct ifreq __user *ifr_u)
> +{
> + struct macvtap_queue *q = file->private_data;
> + struct net *net = current->nsproxy->net_ns;
> + struct inode *inode = file_inode(file);
> + struct net_device *dev, *dev2;
> + struct ifreq ifr;
> +
> + if (copy_from_user(&ifr, ifr_u, sizeof(struct ifreq)))
> + return -EFAULT;
> +
> + /* To keep the same behavior of tuntap, validate ifr_name */

So I'm not sure - why is it important to validate ifr_name here?
We ignore the name for all other flags - why is IFF_MULTI_QUEUE
special?

> + if (ifr.ifr_flags & IFF_MULTI_QUEUE) {
> + dev = __dev_get_by_name(net, ifr.ifr_name);
> + if (!dev)
> + return -EINVAL;
> +
> + dev2 = dev_get_by_macvtap_minor(iminor(inode));
> + if (!dev2)
> + return -EINVAL;
> +
> + if (dev != dev2) {
> + dev_put(dev2);
> + return -EINVAL;
> + }
> +
> + dev_put(dev2);
> + }
> +
> + if ((ifr.ifr_flags & ~(IFF_VNET_HDR | IFF_MULTI_QUEUE)) !=
> + (IFF_NO_PI | IFF_TAP))
> + return -EINVAL;
> + else
> + q->flags = ifr.ifr_flags;
> +
> + return 0;
> +}
> +
> /*
> * provide compatibility with generic tun/tap interface
> */
> @@ -905,17 +944,7 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
>
> switch (cmd) {
> case TUNSETIFF:
> - /* ignore the name, just look at flags */

This is actually a useful comment that you've removed.

> - if (get_user(u, &ifr->ifr_flags))
> - return -EFAULT;
> -
> - ret = 0;
> - if ((u & ~IFF_VNET_HDR) != (IFF_NO_PI | IFF_TAP))
> - ret = -EINVAL;
> - else
> - q->flags = u;
> -
> - return ret;
> + return macvtap_set_iff(file, ifr);
>
> case TUNGETIFF:
> vlan = macvtap_get_vlan(q);
> --
> 1.7.1
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