Linux Virtualization - May 2021 - [PATCH 0/4] Add host USO support to TUN device

This series adds support for UDP segmentation offload feature
in TUN device according to the VIRTIO specification

Yuri Benditovich (4):
  virtio-net: add definitions for host USO feature
  virtio-net: add support of UDP segmentation (USO) on the host
  tun: define feature bit for USO support
  tun: indicate support for USO feature

 drivers/net/tun.c               | 2 +-
 include/linux/virtio_net.h      | 5 +++++
 include/uapi/linux/if_tun.h     | 1 +
 include/uapi/linux/virtio_net.h | 2 ++
 4 files changed, 9 insertions(+), 1 deletion(-)

-- 
2.26.3

Define feature bit and GSO type according to the VIRTIO
specification.

Signed-off-by: Yuri Benditovich <yuri.benditovich at daynix.com>
---
 include/uapi/linux/virtio_net.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index 3f55a4215f11..a556ac735d7f 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -57,6 +57,7 @@
 					 * Steering */
 #define VIRTIO_NET_F_CTRL_MAC_ADDR 23	/* Set MAC address */
 
+#define VIRTIO_NET_F_HOST_USO     56	/* Host can handle USO packets */
 #define VIRTIO_NET_F_HASH_REPORT  57	/* Supports hash report */
 #define VIRTIO_NET_F_RSS	  60	/* Supports RSS RX steering */
 #define VIRTIO_NET_F_RSC_EXT	  61	/* extended coalescing info */
@@ -130,6 +131,7 @@ struct virtio_net_hdr_v1 {
 #define VIRTIO_NET_HDR_GSO_TCPV4	1	/* GSO frame, IPv4 TCP (TSO) */
 #define VIRTIO_NET_HDR_GSO_UDP		3	/* GSO frame, IPv4 UDP (UFO) */
 #define VIRTIO_NET_HDR_GSO_TCPV6	4	/* GSO frame, IPv6 TCP */
+#define VIRTIO_NET_HDR_GSO_UDP_L4	5	/* GSO frame, IPv4 UDP (USO) */
 #define VIRTIO_NET_HDR_GSO_ECN		0x80	/* TCP has ECN set */
 	__u8 gso_type;
 	__virtio16 hdr_len;	/* Ethernet + IP + tcp/udp hdrs */
-- 
2.26.3

Large UDP packet provided by the guest with GSO type set to
VIRTIO_NET_HDR_GSO_UDP_L4 will be divided to several UDP
packets according to the gso_size field.

Signed-off-by: Yuri Benditovich <yuri.benditovich at daynix.com>
---
 include/linux/virtio_net.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index b465f8f3e554..4ecf9a1ca912 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -51,6 +51,11 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
 			ip_proto = IPPROTO_UDP;
 			thlen = sizeof(struct udphdr);
 			break;
+		case VIRTIO_NET_HDR_GSO_UDP_L4:
+			gso_type = SKB_GSO_UDP_L4;
+			ip_proto = IPPROTO_UDP;
+			thlen = sizeof(struct udphdr);
+			break;
 		default:
 			return -EINVAL;
 		}
-- 
2.26.3

User mode software can probe this bit to check whether the
USO feature is supported by TUN/TAP device.

Signed-off-by: Yuri Benditovich <yuri.benditovich at daynix.com>
---
 include/uapi/linux/if_tun.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h
index 454ae31b93c7..24f246920dd5 100644
--- a/include/uapi/linux/if_tun.h
+++ b/include/uapi/linux/if_tun.h
@@ -88,6 +88,7 @@
 #define TUN_F_TSO6	0x04	/* I can handle TSO for IPv6 packets */
 #define TUN_F_TSO_ECN	0x08	/* I can handle TSO with ECN bits. */
 #define TUN_F_UFO	0x10	/* I can handle UFO packets */
+#define TUN_F_USO	0x20	/* I can handle USO packets */
 
 /* Protocol info prepended to the packets (when IFF_NO_PI is not set) */
 #define TUN_PKT_STRIP	0x0001
-- 
2.26.3

Signed-off-by: Yuri Benditovich <yuri.benditovich at daynix.com>
---
 drivers/net/tun.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 84f832806313..a35054f9d941 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2812,7 +2812,7 @@ static int set_offload(struct tun_struct *tun, unsigned
long arg)
 			arg &= ~(TUN_F_TSO4|TUN_F_TSO6);
 		}
 
-		arg &= ~TUN_F_UFO;
+		arg &= ~(TUN_F_UFO|TUN_F_USO);
 	}
 
 	/* This gives the user a way to test for new features in future by
-- 
2.26.3