linux-kernel - Re: [PATCH bpf-next v6 1/2] virtio_net: keep vnet header zeroed if XDP is loaded for small buffer

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Message-ID: <1b3045d0-edc0-3f6f-5442-06f6f927ff94@redhat.com>
Date:   Tue, 25 Feb 2020 13:44:53 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yuya Kusakabe <yuya.kusakabe@...il.com>
Cc:     andriin@...com, ast@...nel.org, bpf@...r.kernel.org,
        daniel@...earbox.net, davem@...emloft.net, hawk@...nel.org,
        john.fastabend@...il.com, kafai@...com, kuba@...nel.org,
        linux-kernel@...r.kernel.org, mst@...hat.com,
        netdev@...r.kernel.org, songliubraving@...com, yhs@...com
Subject: Re: [PATCH bpf-next v6 1/2] virtio_net: keep vnet header zeroed if
 XDP is loaded for small buffer


On 2020/2/25 上午11:32, Yuya Kusakabe wrote:
> We do not want to care about the vnet header in receive_small() if XDP
> is loaded, since we can not know whether or not the packet is modified
> by XDP.
>
> Fixes: f6b10209b90d ("virtio-net: switch to use build_skb() for small buffer")
> Signed-off-by: Yuya Kusakabe <yuya.kusakabe@...il.com>
> ---
>   drivers/net/virtio_net.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 2fe7a3188282..f39d0218bdaa 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -735,10 +735,10 @@ static struct sk_buff *receive_small(struct net_device *dev,
>   	}
>   	skb_reserve(skb, headroom - delta);
>   	skb_put(skb, len);
> -	if (!delta) {
> +	if (!xdp_prog) {
>   		buf += header_offset;
>   		memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
> -	} /* keep zeroed vnet hdr since packet was changed by bpf */
> +	} /* keep zeroed vnet hdr since XDP is loaded */
>   
>   err:
>   	return skb;


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