CMT: [PATCH 2/3][Yakkety][SRU] virtio: don't set VIRTIO_NET_HDR_F_DATA_VALID on xmit

[Colin Ian King]

On 20/04/17 00:41, Jay Vosburgh wrote:
> From: Rolf Neugebauer <rolf.neugebauer at docker.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1683947
> 
> This patch part reverts fd2a0437dc33 and e858fae2b0b8 which introduced a
> subtle change in how the virtio_net flags are derived from the SKBs
> ip_summed field.
> 
> With the above commits, the flags are set to VIRTIO_NET_HDR_F_DATA_VALID
> when ip_summed == CHECKSUM_UNNECESSARY, thus treating it differently to
> ip_summed == CHECKSUM_NONE, which should be the same.
> 
> Further, the virtio spec 1.0 / CS04 explicitly says that
> VIRTIO_NET_HDR_F_DATA_VALID must not be set by the driver.
> 
> Fixes: fd2a0437dc33 ("virtio_net: introduce virtio_net_hdr_{from,to}_skb")
> Fixes: e858fae2b0b8 (" virtio_net: use common code for virtio_net_hdr and skb GSO conversion")
> Signed-off-by: Rolf Neugebauer <rolf.neugebauer at docker.com>
> Acked-by: Michael S. Tsirkin <mst at redhat.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (cherry picked from 3e9e40e74753346218e8285cf1ecff9ef3a624c6)
> Signed-off-by: Jay Vosburgh <jay.vosburgh at canonical.com>
> ---
>  include/linux/virtio_net.h | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index 1c912f85e041..40914bb396e7 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -91,8 +91,6 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
>  				skb_checksum_start_offset(skb));
>  		hdr->csum_offset = __cpu_to_virtio16(little_endian,
>  				skb->csum_offset);
> -	} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
> -		hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
>  	} /* else everything is zero */
>  
>  	return 0;
> 

This is a cherry pick of 501db511397fd6efff3aa5b4e8de415b55559550 and
not 3e9e40e74753346218e8285cf1ecff9ef3a624c6 as reported in the patch.

Apart from that detail, this fix is an upstream fix that looks OK to me.