On 04/11/2018 06:49 PM, Michael S. Tsirkin wrote:
> 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 <vyasevic@xxxxxxxxxx>
>> ---
>> 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.
I suppose this is HOST checksum, since it behaves like VIRTIO_NET_F_CSUM only for
SCTP. I couldn't find the use for the GUEST side flag, since there technically
isn't any validations and there is no additional mappings from VIRTIO flag to a
NETIF flag.
If the feature is negotiated, the guest ends up generating partially check-summed
packets, and the host turns on appropriate flags on it's side. The host will
also make sure the checksum if fixed up if the guest doesn't support it.
So 1 flag is currently all that is needed.
-vlad
>
>
>> @@ -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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