# Re: \[PATCH net-next v2 20/33\] vhost\_net: also populate XDP frame size

- From: Michael S. Tsirkin \<mst@redhat.com\>
- Date: 2020-05-06 20:33:39 
- List: netdev
- Page: https://ratatoskr.run/netdev/2020/05/7733597
- Thread: https://ratatoskr.run/netdev/2020/04/7732341/t.md

```text
On Thu, Apr 30, 2020 at 01:22:03PM +0200, Jesper Dangaard Brouer wrote:
> In vhost_net_build_xdp() the 'buf' that gets queued via an xdp_buff
> have embedded a struct tun_xdp_hdr (located at xdp->data_hard_start)
> which contains the buffer length 'buflen' (with tailroom for
> skb_shared_info). Also storing this buflen in xdp->frame_sz, does not
> obsolete struct tun_xdp_hdr, as it also contains a struct
> virtio_net_hdr with other information.
> 
> Cc: Jason Wang <redacted>
> Signed-off-by: Jesper Dangaard Brouer <redacted>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  drivers/vhost/net.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 2927f02cc7e1..516519dcc8ff 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -747,6 +747,7 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
>  	xdp->data = buf + pad;
>  	xdp->data_end = xdp->data + len;
>  	hdr->buflen = buflen;
> +	xdp->frame_sz = buflen;
>  
>  	--net->refcnt_bias;
>  	alloc_frag->offset += buflen;
> 
> 

```