Subject: Re: [PATCH net] virtio_net: reject XDP programs using header adjustment

From: John Fastabend <[email-masked]>
Date: Mon, 19 Dec 2016 09:50:57 -0800

On 16-12-19 07:05 AM, Jakub Kicinski wrote:
> commit 17bedab27231 ("bpf: xdp: Allow head adjustment in XDP prog")
> added a new XDP helper to prepend and remove data from a frame.
> Make virtio_net reject programs making use of this helper until
> proper support is added.
> 
> Signed-off-by: Jakub Kicinski <[email-masked]>
> ---
>  drivers/net/virtio_net.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 08327e005ccc..db761f37783e 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1677,6 +1677,11 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog)
>  	u16 xdp_qp = 0, curr_qp;
>  	int i, err;
>  
> +	if (prog && prog->xdp_adjust_head) {
> +		netdev_warn(dev, "Does not support bpf_xdp_adjust_head()\n");
> +		return -EOPNOTSUPP;
> +	}
> +
>  	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
>  	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6)) {
>  		netdev_warn(dev, "can't set XDP while host is implementing LRO, disable LRO first\n");
> 

Acked-by: John Fastabend <[email-masked]>

Thanks patch looks good. Alternatively we could push a "bug fix" to
support the adjust header feature depending on how DaveM and MST feel
about that. I don't have a strong opinion but I have the patch on my
queue it just needs some more testing. The adjust header bits were
merged in between some of the later versions of the patch which is how
this check got missed.

Thanks,
John