On Mon, Apr 02, 2018 at 09:40:02AM -0400, Vladislav Yasevich wrote:
> To support SCTP checksum offloading, we need to add a new feature
> to virtio_net, so we can negotiate support between the hypervisor
> and the guest.
> 
> The signalling to the guest that an alternate checksum needs to
> be used is done via a new flag in the virtio_net_hdr.  If the
> flag is set, the host will know to perform an alternate checksum
> calculation, which right now is only CRC32c.
> 
> Signed-off-by: Vladislav Yasevich <vyase...@redhat.com>
> ---
>  drivers/net/virtio_net.c        | 11 ++++++++---
>  include/linux/virtio_net.h      |  6 ++++++
>  include/uapi/linux/virtio_net.h |  2 ++
>  3 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7b187ec..b601294 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2724,9 +2724,14 @@ static int virtnet_probe(struct virtio_device *vdev)
>       /* Do we support "hardware" checksums? */
>       if (virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
>               /* This opens up the world of extra features. */
> -             dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_SG;
> +             netdev_features_t sctp = 0;
> +
> +             if (virtio_has_feature(vdev, VIRTIO_NET_F_SCTP_CSUM))
> +                     sctp |= NETIF_F_SCTP_CRC;
> +
> +             dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_SG | sctp;
>               if (csum)
> -                     dev->features |= NETIF_F_HW_CSUM | NETIF_F_SG;
> +                     dev->features |= NETIF_F_HW_CSUM | NETIF_F_SG | sctp;
>  
>               if (virtio_has_feature(vdev, VIRTIO_NET_F_GSO)) {
>                       dev->hw_features |= NETIF_F_TSO
> @@ -2952,7 +2957,7 @@ static struct virtio_device_id id_table[] = {
>  };
>  
>  #define VIRTNET_FEATURES \
> -     VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM, \
> +     VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM,  VIRTIO_NET_F_SCTP_CSUM, \
>       VIRTIO_NET_F_MAC, \
>       VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6, \
>       VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, 
> VIRTIO_NET_F_GUEST_TSO6, \
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index f144216..2e7a64a 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -39,6 +39,9 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
>  
>               if (!skb_partial_csum_set(skb, start, off))
>                       return -EINVAL;
> +
> +             if (hdr->flags & VIRTIO_NET_HDR_F_CSUM_NOT_INET)
> +                     skb->csum_not_inet = 1;
>       }
>  
>       if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
> @@ -96,6 +99,9 @@ static inline int virtio_net_hdr_from_skb(const struct 
> sk_buff *skb,
>               hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
>       } /* else everything is zero */
>  
> +     if (skb->csum_not_inet)
> +             hdr->flags &= VIRTIO_NET_HDR_F_CSUM_NOT_INET;
> +
>       return 0;
>  }
>  
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index 5de6ed3..3f279c8 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -36,6 +36,7 @@
>  #define VIRTIO_NET_F_GUEST_CSUM      1       /* Guest handles pkts w/ 
> partial csum */
>  #define VIRTIO_NET_F_CTRL_GUEST_OFFLOADS 2 /* Dynamic offload configuration. 
> */
>  #define VIRTIO_NET_F_MTU     3       /* Initial MTU advice */
> +#define VIRTIO_NET_F_SCTP_CSUM  4    /* SCTP checksum offload support */
>  #define VIRTIO_NET_F_MAC     5       /* Host has given MAC address. */
>  #define VIRTIO_NET_F_GUEST_TSO4      7       /* Guest can handle TSOv4 in. */
>  #define VIRTIO_NET_F_GUEST_TSO6      8       /* Guest can handle TSOv6 in. */

Is this a guest or a host checksum? We should differenciate between the
two.


> @@ -101,6 +102,7 @@ struct virtio_net_config {
>  struct virtio_net_hdr_v1 {
>  #define VIRTIO_NET_HDR_F_NEEDS_CSUM  1       /* Use csum_start, csum_offset 
> */
>  #define VIRTIO_NET_HDR_F_DATA_VALID  2       /* Csum is valid */
> +#define VIRTIO_NET_HDR_F_CSUM_NOT_INET  4       /* Checksum is not inet */
>       __u8 flags;
>  #define VIRTIO_NET_HDR_GSO_NONE              0       /* Not a GSO frame */
>  #define VIRTIO_NET_HDR_GSO_TCPV4     1       /* GSO frame, IPv4 TCP (TSO) */
> -- 
> 2.9.5
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