[PATCH v2] virtio_net: Introduce extended RSC feature

[Yuri Benditovich]

VIRTIO_NET_F_RSC_EXT feature bit indicates that the device
is able to provide extended RSC information. When the feature
is active and 'gso_type' field in received packet is not GSO_NONE,
the device reports number of coalesced packets in 'csum_start'
field and number of duplicated acks in 'csum_offset' field
and sets VIRTIO_NET_HDR_F_RSC_INFO in 'flags' field.

Signed-off-by: Yuri Benditovich <yuri.benditovich@xxxxxxxxxx>
---
 include/uapi/linux/virtio_net.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index a3715a3224c1..23e73d666fc2 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -56,7 +56,7 @@
 #define VIRTIO_NET_F_MQ	22	/* Device supports Receive Flow
 					 * Steering */
 #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
-
+#define VIRTIO_NET_F_RSC_EXT	  61	/* Provides extended RSC info */
 #define VIRTIO_NET_F_STANDBY	  62	/* Act as standby for another device
 					 * with the same MAC.
 					 */
@@ -104,6 +104,7 @@ 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_RSC_INFO	4   /* rsc_ext data in csum_ fields */
 	__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) */
@@ -118,6 +119,15 @@ struct virtio_net_hdr_v1 {
 	__virtio16 num_buffers;	/* Number of merged rx buffers */
 };
 
+/* if VIRTIO_NET_HDR_F_RSC_INFO is set, the csum_start
+ * field contains number of coalesced segments
+ */
+#define virtio_net_rsc_ext_num_packets csum_start
+/* if VIRTIO_NET_HDR_F_RSC_INFO is set, the csum_offset
+ * field contains number of duplicated acks
+ */
+#define virtio_net_rsc_ext_num_dupacks csum_offset
+
 #ifndef VIRTIO_NET_NO_LEGACY
 /* This header comes first in the scatter-gather list.
  * For legacy virtio, if VIRTIO_F_ANY_LAYOUT is not negotiated, it must
-- 
2.17.1