This adds
1) SEQPACKET ops for virtio transport and 'seqpacket_allow()' callback.
2) Handling of SEQPACKET bit: guest tries to negotiate it with vhost.

Signed-off-by: Arseny Krasnov <redacted>
---
v8 -> v9:
1) Move 'seqpacket_allow' to 'struct virtio_vsock'.

net/vmw_vsock/virtio_transport.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 2700a63ab095..f714c16af65d 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c

@@ -62,6 +62,7 @@ struct virtio_vsock {

	struct virtio_vsock_event event_list[8];

	u32 guest_cid;
+	bool seqpacket_allow;
};

static u32 virtio_transport_get_local_cid(void)

@@ -443,6 +444,8 @@ static void virtio_vsock_rx_done(struct virtqueue *vq)

	queue_work(virtio_vsock_workqueue, &vsock->rx_work);
}

+static bool virtio_transport_seqpacket_allow(u32 remote_cid);
+
static struct virtio_transport virtio_transport = {
	.transport = {
		.module                   = THIS_MODULE,

@@ -469,6 +472,10 @@ static struct virtio_transport virtio_transport = {

		.stream_is_active         = virtio_transport_stream_is_active,
		.stream_allow             = virtio_transport_stream_allow,

+		.seqpacket_dequeue        = virtio_transport_seqpacket_dequeue,
+		.seqpacket_enqueue        = virtio_transport_seqpacket_enqueue,
+		.seqpacket_allow          = virtio_transport_seqpacket_allow,
+
		.notify_poll_in           = virtio_transport_notify_poll_in,
		.notify_poll_out          = virtio_transport_notify_poll_out,
		.notify_recv_init         = virtio_transport_notify_recv_init,

@@ -485,6 +492,19 @@ static struct virtio_transport virtio_transport = {

	.send_pkt = virtio_transport_send_pkt,
};

+static bool virtio_transport_seqpacket_allow(u32 remote_cid)
+{
+	struct virtio_vsock *vsock;
+	bool seqpacket_allow;
+
+	rcu_read_lock();
+	vsock = rcu_dereference(the_virtio_vsock);
+	seqpacket_allow = vsock->seqpacket_allow;
+	rcu_read_unlock();
+
+	return seqpacket_allow;
+}
+
static void virtio_transport_rx_work(struct work_struct *work)
{
	struct virtio_vsock *vsock =

@@ -612,6 +632,10 @@ static int virtio_vsock_probe(struct virtio_device *vdev)

	rcu_assign_pointer(the_virtio_vsock, vsock);

	mutex_unlock(&the_virtio_vsock_mutex);
+
+	if (vdev->features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))