vhost: add guest offload setting

Add guest offload setting in vhost lib.

Virtio 1.0 spec (5.1.6.4 Processing of Incoming Packets) says:

    1. If the VIRTIO_NET_F_GUEST_CSUM feature was negotiated, the
       VIRTIO_NET_HDR_F_NEEDS_CSUM bit in flags can be set: if so,
       the packet checksum at offset csum_offset from csum_start
       and any preceding checksums have been validated. The checksum
       on the packet is incomplete and csum_start and csum_offset
       indicate how to calculate it (see Packet Transmission point 1).

    2. If the VIRTIO_NET_F_GUEST_TSO4, TSO6 or UFO options were
       negotiated, then gso_type MAY be something other than
       VIRTIO_NET_HDR_GSO_NONE, and gso_size field indicates the
       desired MSS (see Packet Transmission point 2).

In order to support these features, the following changes are added,

1. Extend 'VHOST_SUPPORTED_FEATURES' macro to add the offload features negotiation.

2. Enqueue these offloads: convert some fields in mbuf to the fields in virtio_net_hdr.

There are more explanations for the implementation.

For VM2VM case, there is no need to do checksum, for we think the
  data should be reliable enough, and setting VIRTIO_NET_HDR_F_NEEDS_CSUM
  at RX side will let the TCP layer to bypass the checksum validation,
  so that the RX side could receive the packet in the end.

In terms of us-vhost, at vhost RX side, the offload information is
  inherited from mbuf, which is in turn inherited from TX side. If we
  can still get those info at RX side, it means the packet is from
  another VM at same host. So, it's safe to set the
  VIRTIO_NET_HDR_F_NEEDS_CSUM, to skip checksum validation.

Signed-off-by: Jijiang Liu <jijiang.liu@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

doc/guides/rel_notes/release_16_04.rst

@@ -41,7 +41,7 @@ This section should contain new features added in this release. Sample format:
 
 * **Supported virtio offload in vhost-user.**
 
-  Add the offload of checksum and TSO between vhost-user and
+  Add the offload and negotiation of checksum and TSO between vhost-user and
   vanilla Linux virtio guest.
 
 

lib/librte_vhost/vhost_rxtx.c

@@ -54,6 +54,44 @@ is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t qp_nb)
 	return (is_tx ^ (idx & 1)) == 0 && idx < qp_nb * VIRTIO_QNUM;
 }
 
+static void
+virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr)
+{
+	memset(net_hdr, 0, sizeof(struct virtio_net_hdr));
+
+	if (m_buf->ol_flags & PKT_TX_L4_MASK) {
+		net_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+		net_hdr->csum_start = m_buf->l2_len + m_buf->l3_len;
+
+		switch (m_buf->ol_flags & PKT_TX_L4_MASK) {
+		case PKT_TX_TCP_CKSUM:
+			net_hdr->csum_offset = (offsetof(struct tcp_hdr,
+						cksum));
+			break;
+		case PKT_TX_UDP_CKSUM:
+			net_hdr->csum_offset = (offsetof(struct udp_hdr,
+						dgram_cksum));
+			break;
+		case PKT_TX_SCTP_CKSUM:
+			net_hdr->csum_offset = (offsetof(struct sctp_hdr,
+						cksum));
+			break;
+		}
+	}
+
+	if (m_buf->ol_flags & PKT_TX_TCP_SEG) {
+		if (m_buf->ol_flags & PKT_TX_IPV4)
+			net_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+		else
+			net_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+		net_hdr->gso_size = m_buf->tso_segsz;
+		net_hdr->hdr_len = m_buf->l2_len + m_buf->l3_len
+					+ m_buf->l4_len;
+	}
+
+	return;
+}
+
 /**
  * This function adds buffers to the virtio devices RX virtqueue. Buffers can
  * be received from the physical port or from another virtio device. A packet
@@ -67,7 +105,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 {
 	struct vhost_virtqueue *vq;
 	struct vring_desc *desc;
-	struct rte_mbuf *buff;
+	struct rte_mbuf *buff, *first_buff;
 	/* The virtio_hdr is initialised to 0. */
 	struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
 	uint64_t buff_addr = 0;
@@ -139,6 +177,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 		desc = &vq->desc[head[packet_success]];
 
 		buff = pkts[packet_success];
+		first_buff = buff;
 
 		/* Convert from gpa to vva (guest physical addr -> vhost virtual addr) */
 		buff_addr = gpa_to_vva(dev, desc->addr);
@@ -222,6 +261,8 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 		if (unlikely(uncompleted_pkt == 1))
 			continue;
 
+		virtio_enqueue_offload(first_buff, &virtio_hdr.hdr);
+
 		rte_memcpy((void *)(uintptr_t)buff_hdr_addr,
 			(const void *)&virtio_hdr, vq->vhost_hlen);
 
@@ -295,6 +336,8 @@ copy_from_mbuf_to_vring(struct virtio_net *dev, uint32_t queue_id,
 	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") RX: Num merge buffers %d\n",
 		dev->device_fh, virtio_hdr.num_buffers);
 
+	virtio_enqueue_offload(pkt, &virtio_hdr.hdr);
+
 	rte_memcpy((void *)(uintptr_t)vb_hdr_addr,
 		(const void *)&virtio_hdr, vq->vhost_hlen);
 

lib/librte_vhost/virtio-net.c

@@ -80,7 +80,10 @@ static struct virtio_net_config_ll *ll_root;
 				(1ULL << VHOST_USER_F_PROTOCOL_FEATURES) | \
 				(1ULL << VIRTIO_NET_F_HOST_TSO4) | \
 				(1ULL << VIRTIO_NET_F_HOST_TSO6) | \
-				(1ULL << VIRTIO_NET_F_CSUM))
+				(1ULL << VIRTIO_NET_F_CSUM)    | \
+				(1ULL << VIRTIO_NET_F_GUEST_CSUM) | \
+				(1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
+				(1ULL << VIRTIO_NET_F_GUEST_TSO6))
 
 static uint64_t VHOST_FEATURES = VHOST_SUPPORTED_FEATURES;