Re: [PATCH net-next 1/5] virtio: Add support for SCTP checksum offloading

[Jason Wang <jasowang@redhat.com>]

On 2018年04月02日 21:40, 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 <vyasevic@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, \

It looks to me _F_SCTP_CSUM implies the ability of both device and 
driver. Do we still need the flexibility like csum to differ guest/host 
ability like e.g _F_GUEST_SCTP_CSUM?

Thanks

>   	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. */
> @@ -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) */