[PATCH RFC net-next v5 07/14] virtio/vsock: add common datagram send path

[Bobby Eshleman]

This commit implements the common function
virtio_transport_dgram_enqueue for enqueueing datagrams. It does not add
usage in either vhost or virtio yet.

Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
---
 net/vmw_vsock/virtio_transport_common.c | 76 ++++++++++++++++++++++++++++++++-
 1 file changed, 75 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index ffcbdd77feaa..3bfaff758433 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -819,7 +819,81 @@ virtio_transport_dgram_enqueue(struct vsock_sock *vsk,
 			       struct msghdr *msg,
 			       size_t dgram_len)
 {
-	return -EOPNOTSUPP;
+	/* Here we are only using the info struct to retain style uniformity
+	 * and to ease future refactoring and merging.
+	 */
+	struct virtio_vsock_pkt_info info_stack = {
+		.op = VIRTIO_VSOCK_OP_RW,
+		.msg = msg,
+		.vsk = vsk,
+		.type = VIRTIO_VSOCK_TYPE_DGRAM,
+	};
+	const struct virtio_transport *t_ops;
+	struct virtio_vsock_pkt_info *info;
+	struct sock *sk = sk_vsock(vsk);
+	struct virtio_vsock_hdr *hdr;
+	u32 src_cid, src_port;
+	struct sk_buff *skb;
+	void *payload;
+	int noblock;
+	int err;
+
+	info = &info_stack;
+
+	if (dgram_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
+		return -EMSGSIZE;
+
+	t_ops = virtio_transport_get_ops(vsk);
+	if (unlikely(!t_ops))
+		return -EFAULT;
+
+	/* Unlike some of our other sending functions, this function is not
+	 * intended for use without a msghdr.
+	 */
+	if (WARN_ONCE(!msg, "vsock dgram bug: no msghdr found for dgram enqueue\n"))
+		return -EFAULT;
+
+	noblock = msg->msg_flags & MSG_DONTWAIT;
+
+	/* Use sock_alloc_send_skb to throttle by sk_sndbuf. This helps avoid
+	 * triggering the OOM.
+	 */
+	skb = sock_alloc_send_skb(sk, dgram_len + VIRTIO_VSOCK_SKB_HEADROOM,
+				  noblock, &err);
+	if (!skb)
+		return err;
+
+	skb_reserve(skb, VIRTIO_VSOCK_SKB_HEADROOM);
+
+	src_cid = t_ops->transport.get_local_cid();
+	src_port = vsk->local_addr.svm_port;
+
+	hdr = virtio_vsock_hdr(skb);
+	hdr->type	= cpu_to_le16(info->type);
+	hdr->op		= cpu_to_le16(info->op);
+	hdr->src_cid	= cpu_to_le64(src_cid);
+	hdr->dst_cid	= cpu_to_le64(remote_addr->svm_cid);
+	hdr->src_port	= cpu_to_le32(src_port);
+	hdr->dst_port	= cpu_to_le32(remote_addr->svm_port);
+	hdr->flags	= cpu_to_le32(info->flags);
+	hdr->len	= cpu_to_le32(dgram_len);
+
+	skb_set_owner_w(skb, sk);
+
+	payload = skb_put(skb, dgram_len);
+	err = memcpy_from_msg(payload, msg, dgram_len);
+	if (err)
+		return err;
+
+	trace_virtio_transport_alloc_pkt(src_cid, src_port,
+					 remote_addr->svm_cid,
+					 remote_addr->svm_port,
+					 dgram_len,
+					 info->type,
+					 info->op,
+					 0);
+
+	return t_ops->send_pkt(skb);
 }
 EXPORT_SYMBOL_GPL(virtio_transport_dgram_enqueue);
 

-- 
2.30.2