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Subject: Re: [virtio-dev] Re: [PATCH V2 net-next 1/6] virtio: Add support for SCTP checksum offloading
On 05/01/2018 11:16 PM, Michael S. Tsirkin wrote:
> On Tue, May 01, 2018 at 10:07:34PM -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 HOST feature bit signifies offloading support for transmit and
>> enables device offload features.
>> The GUEST feature bit signifies offloading support of recieve and
>> is currently only used by the driver in case of xdp.
>>
>> That patch also adds an addition virtio_net header flag which
>> mirrors the skb->csum_not_inet flag. This flags is used to indicate
>> that is this an SCTP packet that needs its checksum computed by the
>> lower layer. In this case, the lower layer is the host hypervisor or
>> possibly HW nic that supporst CRC32c offload.
>>
>> In the case that GUEST feature bit is flag, it will be possible to
>> receive a virtio_net header with this bit set, which will set the
>> corresponding skb bit. SCTP protocol will be updated to correctly
>> deal with it.
>>
>> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
>> ---
>> drivers/net/virtio_net.c | 14 +++++++++++++-
>> include/linux/virtio_net.h | 6 ++++++
>> include/uapi/linux/virtio_net.h | 5 +++++
>> 3 files changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 7b187ec..34af280 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -2148,6 +2148,8 @@ static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
>>
>> if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
>> offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
>> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
>> + offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
>>
>> return virtnet_set_guest_offloads(vi, offloads);
>> }
>> @@ -2160,6 +2162,8 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
>> return 0;
>> if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
>> offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
>> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_SCTP_CSUM))
>> + offloads |= 1ULL << VIRTIO_NET_F_GUEST_SCTP_CSUM;
>>
>> return virtnet_set_guest_offloads(vi, offloads);
>> }
>> @@ -2724,6 +2728,7 @@ 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;
>> if (csum)
>> dev->features |= NETIF_F_HW_CSUM | NETIF_F_SG;
>> @@ -2746,9 +2751,15 @@ static int virtnet_probe(struct virtio_device *vdev)
>> dev->features |= dev->hw_features & NETIF_F_ALL_TSO;
>> /* (!csum && gso) case will be fixed by register_netdev() */
>> }
>> +
>> if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
>> dev->features |= NETIF_F_RXCSUM;
>>
>> + if (virtio_has_feature(vdev, VIRTIO_NET_F_HOST_SCTP_CSUM)) {
>> + dev->hw_features |= NETIF_F_SCTP_CRC;
>> + dev->features |= NETIF_F_SCTP_CRC;
>> + }
>> +
>> dev->vlan_features = dev->features;
>>
>> /* MTU range: 68 - 65535 */
>> @@ -2962,7 +2973,8 @@ static struct virtio_device_id id_table[] = {
>> VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
>> VIRTIO_NET_F_CTRL_MAC_ADDR, \
>> VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
>> - VIRTIO_NET_F_SPEED_DUPLEX
>> + VIRTIO_NET_F_SPEED_DUPLEX, \
>> + VIRTIO_NET_F_HOST_SCTP_CSUM, VIRTIO_NET_F_GUEST_SCTP_CSUM
>>
>> static unsigned int features[] = {
>> VIRTNET_FEATURES,
>> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
>> index f144216..28fffdc 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) {
>> @@ -91,6 +94,9 @@ 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);
>> +
>> + if (skb->csum_not_inet)
>> + hdr->flags |= VIRTIO_NET_HDR_F_CSUM_NOT_INET;
>> } else if (has_data_valid &&
>> skb->ip_summed == CHECKSUM_UNNECESSARY) {
>> hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
>> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
>> index 5de6ed3..9dfca1a 100644
>> --- a/include/uapi/linux/virtio_net.h
>> +++ b/include/uapi/linux/virtio_net.h
>> @@ -57,6 +57,10 @@
>> * Steering */
>> #define VIRTIO_NET_F_CTRL_MAC_ADDR 23 /* Set MAC address */
>>
>> +#define VIRTIO_NET_F_GUEST_SCTP_CSUM 61 /* Guest handles SCTP pks w/ partial
>> + * csum */
>> +#define VIRTIO_NET_F_HOST_SCTP_CSUM 62 /* HOST handles SCTP pkts w/ partial
>> + * csum */
>> #define VIRTIO_NET_F_SPEED_DUPLEX 63 /* Device set linkspeed and duplex */
>>
>> #ifndef VIRTIO_NET_NO_LEGACY
>> @@ -101,6 +105,7 @@ 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 */
>
> Both comment and name are not very informative.
> How about just saying CRC32c ?
It mirrors what's in the kernel, and I think the goal there was to make
it a bit more generic. However, we can probably be specific here and add
another flag in the future if a different type of checksum would ever be used.
-vlad
>
>> __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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