netdev - Re: [PATCH bpf-next] bpf: fix virtio-net's length calc for XDP

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Date:   Mon, 23 Apr 2018 14:33:08 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Nikita V. Shirokov" <tehnerd@...nerd.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "Michael S. Tsirkin" <mst@...hat.com>
Cc:     netdev@...r.kernel.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH bpf-next] bpf: fix virtio-net's length calc for XDP_PASS



On 2018年04月23日 12:16, Nikita V. Shirokov wrote:
> In commit 6870de435b90 ("bpf: make virtio compatible w/
> bpf_xdp_adjust_tail") i didn't account for vi->hdr_len during new
> packet's length calculation after bpf_prog_run in receive_mergeable.
> because of this all packets, if they were passed to the kernel,
> were truncated by 12 bytes.
>
> Fixes:6870de435b90 ("bpf: make virtio compatible w/ bpf_xdp_adjust_tail")
> Reported-by: David Ahern <dsahern@...il.com>
>
> Signed-off-by: Nikita V. Shirokov <tehnerd@...nerd.com>
> ---
>
> Notes:
>      unfortunately it looks like that xdp_tx is still broken because
>      fix by Jason (introduced in "XDP_TX for virtio_net not working in recent kernel?
>      " thread) haven't landed yet)
>
>   drivers/net/virtio_net.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 779a4f798522..08ac2cc986aa 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -761,7 +761,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>   			/* recalculate len if xdp.data or xdp.data_end were
>   			 * adjusted
>   			 */
> -			len = xdp.data_end - xdp.data;
> +			len = xdp.data_end - xdp.data + vi->hdr_len;
>   			/* We can only create skb based on xdp_page. */
>   			if (unlikely(xdp_page != page)) {
>   				rcu_read_unlock();

Acked-by: Jason Wang <jasowang@...hat.com>