Re: [Qemu-devel] [PATCH v3 2/2] virtio-net: introduce a new control to set macaddr

[Stefan Hajnoczi]

On Thu, Jan 17, 2013 at 06:40:12PM +0800, address@hidden wrote:
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 395ab4f..837c978 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -802,14 +802,32 @@ static int virtnet_set_mac_address(struct net_device 
> *dev, void *p)
>       struct virtnet_info *vi = netdev_priv(dev);
>       struct virtio_device *vdev = vi->vdev;
>       int ret;
> +     struct scatterlist sg;
> +     char save_addr[ETH_ALEN];
> +     unsigned char save_aatype;
> +
> +     memcpy(save_addr, dev->dev_addr, ETH_ALEN);
> +     save_aatype = dev->addr_assign_type;
>  
>       ret = eth_mac_addr(dev, p);
>       if (ret)
>               return ret;
>  
> -     if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
> +     if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
> +             sg_init_one(&sg, dev->dev_addr, dev->addr_len);
> +             if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
> +                                       VIRTIO_NET_CTRL_MAC_ADDR_SET,
> +                                       &sg, 1, 0)) {
> +                     dev_warn(&vdev->dev,
> +                              "Failed to set mac address by vq command.\n");
> +                     memcpy(dev->dev_addr, save_addr, ETH_ALEN);
> +                     dev->addr_assign_type = save_aatype;
> +                     return -EINVAL;
> +             }

eth_mac_addr() doesn't allow callers to implement error handling nicely.
Although you didn't duplicate it's code directly, this patch still leaks
internals of eth_mac_addr().

How about splitting eth_mac_addr() in a separate patch:

int eth_prepare_mac_addr_change(struct net_device *dev, void *p)
{
        struct sockaddr *addr = p;
        if (!(dev->priv_flags & IFF_LIVE_ADDR_CHANGE) && netif_running(dev))
                return -EBUSY;
        if (!is_valid_ether_addr(addr->sa_data))
                return -EADDRNOTAVAIL;
        return 0;
}

void eth_commit_mac_addr_change(struct net_device *dev, void *p)
{
        struct sockaddr *addr = p;
        memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
        /* if device marked as NET_ADDR_RANDOM, reset it */
        dev->addr_assign_type &= ~NET_ADDR_RANDOM;
}

/* Default implementation of MAC address changing */
int eth_mac_addr(struct net_device *dev, void *p)
{
        int ret;
        ret = eth_prepare_mac_addr_change(dev, p);
        if (ret < 0)
                return ret;
        eth_commit_mac_addr_change(dev, p);
        return 0;
}

Now virtio_net.c does:

ret = eth_prepare_mac_addr_change(dev, p);
if (ret < 0)
        return ret;

if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
        sg_init_one(&sg, dev->dev_addr, dev->addr_len);
        if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
                                  VIRTIO_NET_CTRL_MAC_ADDR_SET,
                                  &sg, 1, 0)) {
                dev_warn(&vdev->dev,
                         "Failed to set mac address by vq command.\n");
                return -EINVAL;
        }
} ...

eth_commit_mac_addr_change(dev, p);
return 0;

Stefan