[PATCH V2 net-next 1/6] virtio: Add support for SCTP checksum offloading

[Vladislav Yasevich <vyasevich@gmail.com>]

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 */
 	__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