[RFC,10/13] vsock: add multi-transports support
diff mbox series

Message ID 20190927112703.17745-11-sgarzare@redhat.com
State RFC
Delegated to: David Miller
Headers show
Series
  • vsock: add multi-transports support
Related show

Commit Message

Stefano Garzarella Sept. 27, 2019, 11:27 a.m. UTC
This patch adds the support of multiple transports in the
VSOCK core.

With the multi-transports support, we can use vsock with nested VMs
(using also different hypervisors) loading both guest->host and
host->guest transports at the same time.

Major changes:
- vsock core module can be loaded interdependently of the transports
- each 'struct virtio_transport' has a new feature fields
  (H2G, G2H, DGRAM) to identify which directions the transport can
  handle and if it's support DGRAM (only vmci)
- vsock_core_init() and vsock_core_exit() are renamed to
  vsock_core_register() and vsock_core_unregister()
- each stream socket is assigned to a transport when the remote CID
  is set (during the connect() or when we receive a connection request
  on a listener socket).
  The remote CID is used to decide which transport to use:
  - remote CID > VMADDR_CID_HOST will use host->guest transport
  - remote CID <= VMADDR_CID_HOST will use guest->host transport
- listener sockets are not bound to any transports since no transport
  operations are done on it. In this way we can create a listener
  socket, also if the transports are not loaded or with VMADDR_CID_ANY
  to listen on all transports.
- DGRAM sockets are handled as before, since only the vmci_transport
  provides this feature.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
RFC:
- I'd like to move MODULE_ALIAS_NETPROTO(PF_VSOCK) to af_vsock.c.
  @Jorgen could this break the VMware products?
- DGRAM sockets are handled as before, I don't know if make sense work
  on it now, or when another transport will support DGRAM. The big
  issues here is that we cannot link 1-1 a socket to transport as
  for stream sockets since DGRAM is not connection-oriented.
---
 drivers/vhost/vsock.c                   |   6 +-
 include/net/af_vsock.h                  |  15 +-
 net/vmw_vsock/af_vsock.c                | 240 ++++++++++++++++++------
 net/vmw_vsock/hyperv_transport.c        |  28 ++-
 net/vmw_vsock/virtio_transport.c        |   8 +-
 net/vmw_vsock/virtio_transport_common.c |  28 ++-
 net/vmw_vsock/vmci_transport.c          |  31 ++-
 7 files changed, 275 insertions(+), 81 deletions(-)

Comments

Stefan Hajnoczi Oct. 9, 2019, 1:11 p.m. UTC | #1
On Fri, Sep 27, 2019 at 01:27:00PM +0200, Stefano Garzarella wrote:
> RFC:
> - I'd like to move MODULE_ALIAS_NETPROTO(PF_VSOCK) to af_vsock.c.
>   @Jorgen could this break the VMware products?

What will cause the vmw_vsock_vmci_transport.ko module to be loaded
after you remove MODULE_ALIAS_NETPROTO(PF_VSOCK)?  Perhaps
drivers/misc/vmw_vmci/vmci_guest.c:vmci_guest_probe_device() could do
something when the guest driver loads.  There would need to be something
equivalent for the host side too.

This will solve another issue too.  Today the VMCI transport can be
loaded if an application creates an AF_VSOCK socket during early boot
before the virtio transport has been probed.  This happens because the
VMCI transport uses MODULE_ALIAS_NETPROTO(PF_VSOCK) *and* it does not
probe whether this system is actually a VMware guest.

If we instead load the core af_vsock.ko module and transports are only
loaded based on hardware feature probing (e.g. the presence of VMware
guest mode, a virtio PCI adapter, etc) then transports will be
well-behaved.

> - DGRAM sockets are handled as before, I don't know if make sense work
>   on it now, or when another transport will support DGRAM. The big
>   issues here is that we cannot link 1-1 a socket to transport as
>   for stream sockets since DGRAM is not connection-oriented.

Let's ignore DGRAM for now since only VMCI supports it and we therefore
do not require multi-transport support.

> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index 86f8f463e01a..2a081d19e20d 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -94,7 +94,13 @@ struct vsock_transport_send_notify_data {
>  	u64 data2; /* Transport-defined. */
>  };
>  
> +#define VSOCK_TRANSPORT_F_H2G		0x00000001
> +#define VSOCK_TRANSPORT_F_G2H		0x00000002
> +#define VSOCK_TRANSPORT_F_DGRAM		0x00000004

Documentation comments, please.

> +void vsock_core_unregister(const struct vsock_transport *t)
> +{
> +	mutex_lock(&vsock_register_mutex);
> +
> +	/* RFC-TODO: maybe we should check if there are open sockets
> +	 * assigned to that transport and avoid the unregistration
> +	 */

If unregister() is only called from module_exit() functions then holding
a reference to the transport module would be enough to prevent this
case.  The transport could only be removed once all sockets have been
destroyed (and dropped their transport module reference).
Stefano Garzarella Oct. 10, 2019, 12:55 p.m. UTC | #2
On Wed, Oct 09, 2019 at 02:11:23PM +0100, Stefan Hajnoczi wrote:
> On Fri, Sep 27, 2019 at 01:27:00PM +0200, Stefano Garzarella wrote:
> > RFC:
> > - I'd like to move MODULE_ALIAS_NETPROTO(PF_VSOCK) to af_vsock.c.
> >   @Jorgen could this break the VMware products?
> 
> What will cause the vmw_vsock_vmci_transport.ko module to be loaded
> after you remove MODULE_ALIAS_NETPROTO(PF_VSOCK)?  Perhaps
> drivers/misc/vmw_vmci/vmci_guest.c:vmci_guest_probe_device() could do
> something when the guest driver loads.

Good idea, maybe we can call some function provided by vmci_transport
to register it as a guest (I'll remove the type from the transport
and I add it as a parameter of vsock_core_register())

>                                         There would need to be something
> equivalent for the host side too.

Maybe in the vmci_host_do_init_context().

> 
> This will solve another issue too.  Today the VMCI transport can be
> loaded if an application creates an AF_VSOCK socket during early boot
> before the virtio transport has been probed.  This happens because the
> VMCI transport uses MODULE_ALIAS_NETPROTO(PF_VSOCK) *and* it does not
> probe whether this system is actually a VMware guest.
> 
> If we instead load the core af_vsock.ko module and transports are only
> loaded based on hardware feature probing (e.g. the presence of VMware
> guest mode, a virtio PCI adapter, etc) then transports will be
> well-behaved.

Yes, I completely agree with you. I'll try to follow your suggestion,

> 
> > - DGRAM sockets are handled as before, I don't know if make sense work
> >   on it now, or when another transport will support DGRAM. The big
> >   issues here is that we cannot link 1-1 a socket to transport as
> >   for stream sockets since DGRAM is not connection-oriented.
> 
> Let's ignore DGRAM for now since only VMCI supports it and we therefore
> do not require multi-transpor) support.

Okay :)

> 
> > diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> > index 86f8f463e01a..2a081d19e20d 100644
> > --- a/include/net/af_vsock.h
> > +++ b/include/net/af_vsock.h
> > @@ -94,7 +94,13 @@ struct vsock_transport_send_notify_data {
> >  	u64 data2; /* Transport-defined. */
> >  };
> >  
> > +#define VSOCK_TRANSPORT_F_H2G		0x00000001
> > +#define VSOCK_TRANSPORT_F_G2H		0x00000002
> > +#define VSOCK_TRANSPORT_F_DGRAM		0x00000004
> 
> Documentation comments, please.

I'll fix!

> 
> > +void vsock_core_unregister(const struct vsock_transport *t)
> > +{
> > +	mutex_lock(&vsock_register_mutex);
> > +
> > +	/* RFC-TODO: maybe we should check if there are open sockets
> > +	 * assigned to that transport and avoid the unregistration
> > +	 */
> 
> If unregister() is only called from module_exit() functions then holding
> a reference to the transport module would be enough to prevent this
> case.  The transport could only be removed once all sockets have been
> destroyed (and dropped their transport module reference).

Yes. I did this in
"[RFC PATCH 12/13] vsock: prevent transport modules unloading".

Maybe I can merge it in this patch...

Thanks,
Stefano

Patch
diff mbox series

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 6d7e4f022748..375af01a5b64 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -386,6 +386,8 @@  static bool vhost_vsock_more_replies(struct vhost_vsock *vsock)
 
 static struct virtio_transport vhost_transport = {
 	.transport = {
+		.features                 = VSOCK_TRANSPORT_F_H2G,
+
 		.get_local_cid            = vhost_transport_get_local_cid,
 
 		.init                     = virtio_transport_do_socket_init,
@@ -831,7 +833,7 @@  static int __init vhost_vsock_init(void)
 {
 	int ret;
 
-	ret = vsock_core_init(&vhost_transport.transport);
+	ret = vsock_core_register(&vhost_transport.transport);
 	if (ret < 0)
 		return ret;
 	return misc_register(&vhost_vsock_misc);
@@ -840,7 +842,7 @@  static int __init vhost_vsock_init(void)
 static void __exit vhost_vsock_exit(void)
 {
 	misc_deregister(&vhost_vsock_misc);
-	vsock_core_exit();
+	vsock_core_unregister(&vhost_transport.transport);
 };
 
 module_init(vhost_vsock_init);
diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 86f8f463e01a..2a081d19e20d 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -94,7 +94,13 @@  struct vsock_transport_send_notify_data {
 	u64 data2; /* Transport-defined. */
 };
 
+#define VSOCK_TRANSPORT_F_H2G		0x00000001
+#define VSOCK_TRANSPORT_F_G2H		0x00000002
+#define VSOCK_TRANSPORT_F_DGRAM		0x00000004
+
 struct vsock_transport {
+	uint64_t features;
+
 	/* Initialize/tear-down socket. */
 	int (*init)(struct vsock_sock *, struct vsock_sock *);
 	void (*destruct)(struct vsock_sock *);
@@ -156,12 +162,8 @@  struct vsock_transport {
 
 /**** CORE ****/
 
-int __vsock_core_init(const struct vsock_transport *t, struct module *owner);
-static inline int vsock_core_init(const struct vsock_transport *t)
-{
-	return __vsock_core_init(t, THIS_MODULE);
-}
-void vsock_core_exit(void);
+int vsock_core_register(const struct vsock_transport *t);
+void vsock_core_unregister(const struct vsock_transport *t);
 
 /* The transport may downcast this to access transport-specific functions */
 const struct vsock_transport *vsock_core_get_transport(struct vsock_sock *vsk);
@@ -192,6 +194,7 @@  struct sock *vsock_find_connected_socket(struct sockaddr_vm *src,
 					 struct sockaddr_vm *dst);
 void vsock_remove_sock(struct vsock_sock *vsk);
 void vsock_for_each_connected_socket(void (*fn)(struct sock *sk));
+int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk);
 
 /**** TAP ****/
 
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 95e6db21e7e1..c52203fe52c4 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -130,7 +130,12 @@  static struct proto vsock_proto = {
 #define VSOCK_DEFAULT_BUFFER_MAX_SIZE (1024 * 256)
 #define VSOCK_DEFAULT_BUFFER_MIN_SIZE 128
 
-static const struct vsock_transport *transport_single;
+/* Transport used for host->guest communication */
+static const struct vsock_transport *transport_h2g;
+/* Transport used for guest->host communication */
+static const struct vsock_transport *transport_g2h;
+/* Transport used for DGRAM communication */
+static const struct vsock_transport *transport_dgram;
 static DEFINE_MUTEX(vsock_register_mutex);
 
 /**** UTILS ****/
@@ -182,7 +187,7 @@  static int vsock_auto_bind(struct vsock_sock *vsk)
 	return __vsock_bind(sk, &local_addr);
 }
 
-static int __init vsock_init_tables(void)
+static void vsock_init_tables(void)
 {
 	int i;
 
@@ -191,7 +196,6 @@  static int __init vsock_init_tables(void)
 
 	for (i = 0; i < ARRAY_SIZE(vsock_connected_table); i++)
 		INIT_LIST_HEAD(&vsock_connected_table[i]);
-	return 0;
 }
 
 static void __vsock_insert_bound(struct list_head *list,
@@ -376,6 +380,55 @@  void vsock_enqueue_accept(struct sock *listener, struct sock *connected)
 }
 EXPORT_SYMBOL_GPL(vsock_enqueue_accept);
 
+/* Assign a transport to a socket and call the .init transport callback.
+ *
+ * Note: for stream socket this must be called when vsk->remote_addr is set
+ * (e.g. during the connect() or when a connection request on a listener
+ * socket is received).
+ * The vsk->remote_addr is used to decide which transport to use:
+ *  - remote CID > VMADDR_CID_HOST will use host->guest transport
+ *  - remote CID <= VMADDR_CID_HOST will use guest->host transport
+ */
+int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
+{
+	struct sock *sk = sk_vsock(vsk);
+	/* RFC-TODO: should vsk->transport be already assigned?
+	 * How to handle?
+	 */
+	WARN_ON(vsk->transport);
+
+	switch (sk->sk_type) {
+	case SOCK_DGRAM:
+		vsk->transport = transport_dgram;
+		break;
+	case SOCK_STREAM:
+		if (vsk->remote_addr.svm_cid > VMADDR_CID_HOST)
+			vsk->transport = transport_h2g;
+		else
+			vsk->transport = transport_g2h;
+		break;
+	default:
+		return -ESOCKTNOSUPPORT;
+	}
+
+	if (!vsk->transport)
+		return -ENODEV;
+
+	return vsk->transport->init(vsk, psk);
+}
+EXPORT_SYMBOL_GPL(vsock_assign_transport);
+
+static bool vsock_find_cid(unsigned int cid)
+{
+	if (transport_g2h && cid == transport_g2h->get_local_cid())
+		return true;
+
+	if (transport_h2g && cid == VMADDR_CID_HOST)
+		return true;
+
+	return false;
+}
+
 static struct sock *vsock_dequeue_accept(struct sock *listener)
 {
 	struct vsock_sock *vlistener;
@@ -414,6 +467,9 @@  static int vsock_send_shutdown(struct sock *sk, int mode)
 {
 	struct vsock_sock *vsk = vsock_sk(sk);
 
+	if (!vsk->transport)
+		return -ENODEV;
+
 	return vsk->transport->shutdown(vsk, mode);
 }
 
@@ -530,7 +586,6 @@  static int __vsock_bind_dgram(struct vsock_sock *vsk,
 static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr)
 {
 	struct vsock_sock *vsk = vsock_sk(sk);
-	u32 cid;
 	int retval;
 
 	/* First ensure this socket isn't already bound. */
@@ -540,10 +595,9 @@  static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr)
 	/* Now bind to the provided address or select appropriate values if
 	 * none are provided (VMADDR_CID_ANY and VMADDR_PORT_ANY).  Note that
 	 * like AF_INET prevents binding to a non-local IP address (in most
-	 * cases), we only allow binding to the local CID.
+	 * cases), we only allow binding to a local CID.
 	 */
-	cid = vsk->transport->get_local_cid();
-	if (addr->svm_cid != cid && addr->svm_cid != VMADDR_CID_ANY)
+	if (addr->svm_cid != VMADDR_CID_ANY && !vsock_find_cid(addr->svm_cid))
 		return -EADDRNOTAVAIL;
 
 	switch (sk->sk_socket->type) {
@@ -592,7 +646,6 @@  struct sock *__vsock_create(struct net *net,
 		sk->sk_type = type;
 
 	vsk = vsock_sk(sk);
-	vsk->transport = transport_single;
 	vsock_addr_init(&vsk->local_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
 	vsock_addr_init(&vsk->remote_addr, VMADDR_CID_ANY, VMADDR_PORT_ANY);
 
@@ -629,11 +682,6 @@  struct sock *__vsock_create(struct net *net,
 		vsk->buffer_max_size = VSOCK_DEFAULT_BUFFER_MAX_SIZE;
 	}
 
-	if (vsk->transport->init(vsk, psk) < 0) {
-		sk_free(sk);
-		return NULL;
-	}
-
 	return sk;
 }
 EXPORT_SYMBOL_GPL(__vsock_create);
@@ -648,7 +696,10 @@  static void __vsock_release(struct sock *sk)
 		vsk = vsock_sk(sk);
 		pending = NULL;	/* Compiler warning. */
 
-		vsk->transport->release(vsk);
+		if (vsk->transport)
+			vsk->transport->release(vsk);
+		else if (sk->sk_type == SOCK_STREAM)
+			vsock_remove_sock(vsk);
 
 		lock_sock(sk);
 		sock_orphan(sk);
@@ -672,7 +723,8 @@  static void vsock_sk_destruct(struct sock *sk)
 {
 	struct vsock_sock *vsk = vsock_sk(sk);
 
-	vsk->transport->destruct(vsk);
+	if (vsk->transport)
+		vsk->transport->destruct(vsk);
 
 	/* When clearing these addresses, there's no need to set the family and
 	 * possibly register the address family with the kernel.
@@ -882,7 +934,7 @@  static __poll_t vsock_poll(struct file *file, struct socket *sock,
 			mask |= EPOLLIN | EPOLLRDNORM;
 
 		/* If there is something in the queue then we can read. */
-		if (transport->stream_is_active(vsk) &&
+		if (transport && transport->stream_is_active(vsk) &&
 		    !(sk->sk_shutdown & RCV_SHUTDOWN)) {
 			bool data_ready_now = false;
 			int ret = transport->notify_poll_in(
@@ -1132,7 +1184,6 @@  static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr,
 	err = 0;
 	sk = sock->sk;
 	vsk = vsock_sk(sk);
-	transport = vsk->transport;
 
 	lock_sock(sk);
 
@@ -1160,19 +1211,26 @@  static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr,
 			goto out;
 		}
 
+		/* Set the remote address that we are connecting to. */
+		memcpy(&vsk->remote_addr, remote_addr,
+		       sizeof(vsk->remote_addr));
+
+		err = vsock_assign_transport(vsk, NULL);
+		if (err)
+			goto out;
+
+		transport = vsk->transport;
+
 		/* The hypervisor and well-known contexts do not have socket
 		 * endpoints.
 		 */
-		if (!transport->stream_allow(remote_addr->svm_cid,
+		if (!transport ||
+		    !transport->stream_allow(remote_addr->svm_cid,
 					     remote_addr->svm_port)) {
 			err = -ENETUNREACH;
 			goto out;
 		}
 
-		/* Set the remote address that we are connecting to. */
-		memcpy(&vsk->remote_addr, remote_addr,
-		       sizeof(vsk->remote_addr));
-
 		err = vsock_auto_bind(vsk);
 		if (err)
 			goto out;
@@ -1572,7 +1630,7 @@  static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 		goto out;
 	}
 
-	if (sk->sk_state != TCP_ESTABLISHED ||
+	if (!transport || sk->sk_state != TCP_ESTABLISHED ||
 	    !vsock_addr_bound(&vsk->local_addr)) {
 		err = -ENOTCONN;
 		goto out;
@@ -1698,7 +1756,7 @@  vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 
 	lock_sock(sk);
 
-	if (sk->sk_state != TCP_ESTABLISHED) {
+	if (!transport || sk->sk_state != TCP_ESTABLISHED) {
 		/* Recvmsg is supposed to return 0 if a peer performs an
 		 * orderly shutdown. Differentiate between that case and when a
 		 * peer has not connected or a local shutdown occured with the
@@ -1872,7 +1930,9 @@  static const struct proto_ops vsock_stream_ops = {
 static int vsock_create(struct net *net, struct socket *sock,
 			int protocol, int kern)
 {
+	struct vsock_sock *vsk;
 	struct sock *sk;
+	int ret;
 
 	if (!sock)
 		return -EINVAL;
@@ -1897,7 +1957,20 @@  static int vsock_create(struct net *net, struct socket *sock,
 	if (!sk)
 		return -ENOMEM;
 
-	vsock_insert_unbound(vsock_sk(sk));
+	vsk = vsock_sk(sk);
+
+	/* RFC-TODO: for dgram we still support only one transport, and
+	 * we assign it during the sock creation.
+	 */
+	if (sock->type == SOCK_DGRAM) {
+		ret = vsock_assign_transport(vsk, NULL);
+		if (ret < 0) {
+			sock_put(sk);
+			return ret;
+		}
+	}
+
+	vsock_insert_unbound(vsk);
 
 	return 0;
 }
@@ -1912,11 +1985,20 @@  static long vsock_dev_do_ioctl(struct file *filp,
 			       unsigned int cmd, void __user *ptr)
 {
 	u32 __user *p = ptr;
+	u32 cid = VMADDR_CID_ANY;
 	int retval = 0;
 
 	switch (cmd) {
 	case IOCTL_VM_SOCKETS_GET_LOCAL_CID:
-		if (put_user(transport_single->get_local_cid(), p) != 0)
+		/* To be compatible with the VMCI behavior, we prioritize the
+		 * guest CID instead of well-know host CID (VMADDR_CID_HOST).
+		 */
+		if (transport_g2h)
+			cid = transport_g2h->get_local_cid();
+		else if (transport_h2g)
+			cid = transport_h2g->get_local_cid();
+
+		if (put_user(cid, p) != 0)
 			retval = -EFAULT;
 		break;
 
@@ -1956,24 +2038,13 @@  static struct miscdevice vsock_device = {
 	.fops		= &vsock_device_ops,
 };
 
-int __vsock_core_init(const struct vsock_transport *t, struct module *owner)
+static int __init vsock_init(void)
 {
-	int err = mutex_lock_interruptible(&vsock_register_mutex);
+	int err = 0;
 
-	if (err)
-		return err;
-
-	if (transport_single) {
-		err = -EBUSY;
-		goto err_busy;
-	}
-
-	/* Transport must be the owner of the protocol so that it can't
-	 * unload while there are open sockets.
-	 */
-	vsock_proto.owner = owner;
-	transport_single = t;
+	vsock_init_tables();
 
+	vsock_proto.owner = THIS_MODULE;
 	vsock_device.minor = MISC_DYNAMIC_MINOR;
 	err = misc_register(&vsock_device);
 	if (err) {
@@ -1994,7 +2065,6 @@  int __vsock_core_init(const struct vsock_transport *t, struct module *owner)
 		goto err_unregister_proto;
 	}
 
-	mutex_unlock(&vsock_register_mutex);
 	return 0;
 
 err_unregister_proto:
@@ -2002,28 +2072,15 @@  int __vsock_core_init(const struct vsock_transport *t, struct module *owner)
 err_deregister_misc:
 	misc_deregister(&vsock_device);
 err_reset_transport:
-	transport_single = NULL;
-err_busy:
-	mutex_unlock(&vsock_register_mutex);
 	return err;
 }
-EXPORT_SYMBOL_GPL(__vsock_core_init);
 
-void vsock_core_exit(void)
+static void __exit vsock_exit(void)
 {
-	mutex_lock(&vsock_register_mutex);
-
 	misc_deregister(&vsock_device);
 	sock_unregister(AF_VSOCK);
 	proto_unregister(&vsock_proto);
-
-	/* We do not want the assignment below re-ordered. */
-	mb();
-	transport_single = NULL;
-
-	mutex_unlock(&vsock_register_mutex);
 }
-EXPORT_SYMBOL_GPL(vsock_core_exit);
 
 const struct vsock_transport *vsock_core_get_transport(struct vsock_sock *vsk)
 {
@@ -2034,12 +2091,77 @@  const struct vsock_transport *vsock_core_get_transport(struct vsock_sock *vsk)
 }
 EXPORT_SYMBOL_GPL(vsock_core_get_transport);
 
-static void __exit vsock_exit(void)
+int vsock_core_register(const struct vsock_transport *t)
 {
-	/* Do nothing.  This function makes this module removable. */
+	const struct vsock_transport *t_h2g, *t_g2h, *t_dgram;
+	int err = mutex_lock_interruptible(&vsock_register_mutex);
+
+	if (err)
+		return err;
+
+	t_h2g = transport_h2g;
+	t_g2h = transport_g2h;
+	t_dgram = transport_dgram;
+
+	/* RFC-TODO: vmci transport offer both H2G and G2H features in the
+	 * same transport. We are able to set the G2H feature only if we are
+	 * in a VMware guest, but we are not able to do the same for the host.
+	 */
+	if (t->features & VSOCK_TRANSPORT_F_H2G) {
+		if (t_h2g) {
+			err = -EBUSY;
+			goto err_busy;
+		}
+		t_h2g = t;
+	}
+
+	if (t->features & VSOCK_TRANSPORT_F_G2H) {
+		if (t_g2h) {
+			err = -EBUSY;
+			goto err_busy;
+		}
+		t_g2h = t;
+	}
+
+	if (t->features & VSOCK_TRANSPORT_F_DGRAM) {
+		if (t_dgram) {
+			err = -EBUSY;
+			goto err_busy;
+		}
+		t_dgram = t;
+	}
+
+	transport_h2g = t_h2g;
+	transport_g2h = t_g2h;
+	transport_dgram = t_dgram;
+
+err_busy:
+	mutex_unlock(&vsock_register_mutex);
+	return err;
+}
+EXPORT_SYMBOL_GPL(vsock_core_register);
+
+void vsock_core_unregister(const struct vsock_transport *t)
+{
+	mutex_lock(&vsock_register_mutex);
+
+	/* RFC-TODO: maybe we should check if there are open sockets
+	 * assigned to that transport and avoid the unregistration
+	 */
+	if (transport_h2g == t)
+		transport_h2g = NULL;
+
+	if (transport_g2h == t)
+		transport_g2h = NULL;
+
+	if (transport_dgram == t)
+		transport_dgram = NULL;
+
+	mutex_unlock(&vsock_register_mutex);
 }
+EXPORT_SYMBOL_GPL(vsock_core_unregister);
 
-module_init(vsock_init_tables);
+module_init(vsock_init);
 module_exit(vsock_exit);
 
 MODULE_AUTHOR("VMware, Inc.");
diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index 306310794522..94e6fc905a77 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -163,6 +163,8 @@  static const guid_t srv_id_template =
 	GUID_INIT(0x00000000, 0xfacb, 0x11e6, 0xbd, 0x58,
 		  0x64, 0x00, 0x6a, 0x79, 0x86, 0xd3);
 
+static bool hvs_check_transport(struct vsock_sock *vsk);
+
 static bool is_valid_srv_id(const guid_t *id)
 {
 	return !memcmp(&id->b[4], &srv_id_template.b[4], sizeof(guid_t) - 4);
@@ -366,6 +368,18 @@  static void hvs_open_connection(struct vmbus_channel *chan)
 
 		new->sk_state = TCP_SYN_SENT;
 		vnew = vsock_sk(new);
+
+		hvs_addr_init(&vnew->local_addr, if_type);
+		hvs_remote_addr_init(&vnew->remote_addr, &vnew->local_addr);
+
+		ret = vsock_assign_transport(vnew, vsock_sk(sk));
+		/* Transport assigned (looking at remote_addr) must be the
+		 * same where we received the request.
+		 */
+		if (ret || !hvs_check_transport(vnew)) {
+			sock_put(new);
+			goto out;
+		}
 		hvs_new = vnew->trans;
 		hvs_new->chan = chan;
 	} else {
@@ -429,9 +443,6 @@  static void hvs_open_connection(struct vmbus_channel *chan)
 		new->sk_state = TCP_ESTABLISHED;
 		sk->sk_ack_backlog++;
 
-		hvs_addr_init(&vnew->local_addr, if_type);
-		hvs_remote_addr_init(&vnew->remote_addr, &vnew->local_addr);
-
 		hvs_new->vm_srv_id = *if_type;
 		hvs_new->host_srv_id = *if_instance;
 
@@ -845,6 +856,8 @@  int hvs_notify_send_post_enqueue(struct vsock_sock *vsk, ssize_t written,
 }
 
 static struct vsock_transport hvs_transport = {
+	.features                 = VSOCK_TRANSPORT_F_G2H,
+
 	.get_local_cid            = hvs_get_local_cid,
 
 	.init                     = hvs_sock_init,
@@ -879,6 +892,11 @@  static struct vsock_transport hvs_transport = {
 
 };
 
+static bool hvs_check_transport(struct vsock_sock *vsk)
+{
+	return vsk->transport == &hvs_transport;
+}
+
 static int hvs_probe(struct hv_device *hdev,
 		     const struct hv_vmbus_device_id *dev_id)
 {
@@ -927,7 +945,7 @@  static int __init hvs_init(void)
 	if (ret != 0)
 		return ret;
 
-	ret = vsock_core_init(&hvs_transport);
+	ret = vsock_core_register(&hvs_transport);
 	if (ret) {
 		vmbus_driver_unregister(&hvs_drv);
 		return ret;
@@ -938,7 +956,7 @@  static int __init hvs_init(void)
 
 static void __exit hvs_exit(void)
 {
-	vsock_core_exit();
+	vsock_core_unregister(&hvs_transport);
 	vmbus_driver_unregister(&hvs_drv);
 }
 
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index fb1fc7760e8c..0ff037ef7f8e 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -462,6 +462,8 @@  static void virtio_vsock_rx_done(struct virtqueue *vq)
 
 static struct virtio_transport virtio_transport = {
 	.transport = {
+		.features                 = VSOCK_TRANSPORT_F_G2H,
+
 		.get_local_cid            = virtio_transport_get_local_cid,
 
 		.init                     = virtio_transport_do_socket_init,
@@ -770,7 +772,7 @@  static int __init virtio_vsock_init(void)
 	if (!virtio_vsock_workqueue)
 		return -ENOMEM;
 
-	ret = vsock_core_init(&virtio_transport.transport);
+	ret = vsock_core_register(&virtio_transport.transport);
 	if (ret)
 		goto out_wq;
 
@@ -781,7 +783,7 @@  static int __init virtio_vsock_init(void)
 	return 0;
 
 out_vci:
-	vsock_core_exit();
+	vsock_core_unregister(&virtio_transport.transport);
 out_wq:
 	destroy_workqueue(virtio_vsock_workqueue);
 	return ret;
@@ -790,7 +792,7 @@  static int __init virtio_vsock_init(void)
 static void __exit virtio_vsock_exit(void)
 {
 	unregister_virtio_driver(&virtio_vsock_driver);
-	vsock_core_exit();
+	vsock_core_unregister(&virtio_transport.transport);
 	destroy_workqueue(virtio_vsock_workqueue);
 }
 
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index bac9e7430a2e..ebb4701310a4 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -400,7 +400,7 @@  int virtio_transport_do_socket_init(struct vsock_sock *vsk,
 
 	vsk->trans = vvs;
 	vvs->vsk = vsk;
-	if (psk) {
+	if (psk && psk->trans) {
 		struct virtio_vsock_sock *ptrans = psk->trans;
 
 		vvs->peer_buf_alloc = ptrans->peer_buf_alloc;
@@ -927,11 +927,13 @@  virtio_transport_send_response(struct vsock_sock *vsk,
 
 /* Handle server socket */
 static int
-virtio_transport_recv_listen(struct sock *sk, struct virtio_vsock_pkt *pkt)
+virtio_transport_recv_listen(struct sock *sk, struct virtio_vsock_pkt *pkt,
+			     struct virtio_transport *t)
 {
 	struct vsock_sock *vsk = vsock_sk(sk);
 	struct vsock_sock *vchild;
 	struct sock *child;
+	int ret;
 
 	if (le16_to_cpu(pkt->hdr.op) != VIRTIO_VSOCK_OP_REQUEST) {
 		virtio_transport_reset(vsk, pkt);
@@ -962,6 +964,17 @@  virtio_transport_recv_listen(struct sock *sk, struct virtio_vsock_pkt *pkt)
 	vsock_addr_init(&vchild->remote_addr, le64_to_cpu(pkt->hdr.src_cid),
 			le32_to_cpu(pkt->hdr.src_port));
 
+	ret = vsock_assign_transport(vchild, vsk);
+	/* Transport assigned (looking at remote_addr) must be the same
+	 * where we received the request.
+	 */
+	if (ret || vchild->transport != &t->transport) {
+		release_sock(child);
+		virtio_transport_reset(vsk, pkt);
+		sock_put(child);
+		return ret;
+	}
+
 	vsock_insert_connected(vchild);
 	vsock_enqueue_accept(sk, child);
 	virtio_transport_send_response(vchild, pkt);
@@ -979,6 +992,14 @@  static bool virtio_transport_space_update(struct sock *sk,
 	struct virtio_vsock_sock *vvs = vsk->trans;
 	bool space_available;
 
+	/* Listener sockets are not associated with any transport, so we are
+	 * not able to take the state to see if there is space available in the
+	 * remote peer, but since they are only used to receive requests, we
+	 * can assume that there is always space available in the other peer.
+	 */
+	if (!vvs)
+		return true;
+
 	/* buf_alloc and fwd_cnt is always included in the hdr */
 	spin_lock_bh(&vvs->tx_lock);
 	vvs->peer_buf_alloc = le32_to_cpu(pkt->hdr.buf_alloc);
@@ -1044,7 +1065,7 @@  void virtio_transport_recv_pkt(struct virtio_transport *t,
 
 	switch (sk->sk_state) {
 	case TCP_LISTEN:
-		virtio_transport_recv_listen(sk, pkt);
+		virtio_transport_recv_listen(sk, pkt, t);
 		virtio_transport_free_pkt(pkt);
 		break;
 	case TCP_SYN_SENT:
@@ -1062,6 +1083,7 @@  void virtio_transport_recv_pkt(struct virtio_transport *t,
 		virtio_transport_free_pkt(pkt);
 		break;
 	}
+
 	release_sock(sk);
 
 	/* Release refcnt obtained when we fetched this socket out of the
diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
index 8290d37b6587..52e63952d0d4 100644
--- a/net/vmw_vsock/vmci_transport.c
+++ b/net/vmw_vsock/vmci_transport.c
@@ -57,6 +57,7 @@  static bool vmci_transport_old_proto_override(bool *old_pkt_proto);
 static u16 vmci_transport_new_proto_supported_versions(void);
 static bool vmci_transport_proto_to_notify_struct(struct sock *sk, u16 *proto,
 						  bool old_pkt_proto);
+static bool vmci_check_transport(struct vsock_sock *vsk);
 
 struct vmci_transport_recv_pkt_info {
 	struct work_struct work;
@@ -1018,6 +1019,15 @@  static int vmci_transport_recv_listen(struct sock *sk,
 	vsock_addr_init(&vpending->remote_addr, pkt->dg.src.context,
 			pkt->src_port);
 
+	err = vsock_assign_transport(vpending, vsock_sk(sk));
+	/* Transport assigned (looking at remote_addr) must be the same
+	 * where we received the request.
+	 */
+	if (err || !vmci_check_transport(vpending)) {
+		sock_put(pending);
+		return err;
+	}
+
 	/* If the proposed size fits within our min/max, accept it. Otherwise
 	 * propose our own size.
 	 */
@@ -2009,7 +2019,8 @@  static u32 vmci_transport_get_local_cid(void)
 	return vmci_get_context_id();
 }
 
-static const struct vsock_transport vmci_transport = {
+static struct vsock_transport vmci_transport = {
+	.features = VSOCK_TRANSPORT_F_DGRAM | VSOCK_TRANSPORT_F_H2G,
 	.init = vmci_transport_socket_init,
 	.destruct = vmci_transport_destruct,
 	.release = vmci_transport_release,
@@ -2039,10 +2050,24 @@  static const struct vsock_transport vmci_transport = {
 	.get_local_cid = vmci_transport_get_local_cid,
 };
 
+static bool vmci_check_transport(struct vsock_sock *vsk)
+{
+	return vsk->transport == &vmci_transport;
+}
+
 static int __init vmci_transport_init(void)
 {
+	int cid;
 	int err;
 
+	cid = vmci_get_context_id();
+
+	if (cid == VMCI_INVALID_ID)
+		return -EINVAL;
+
+	if (cid != VMCI_HOST_CONTEXT_ID)
+		vmci_transport.features |= VSOCK_TRANSPORT_F_G2H;
+
 	/* Create the datagram handle that we will use to send and receive all
 	 * VSocket control messages for this context.
 	 */
@@ -2066,7 +2091,7 @@  static int __init vmci_transport_init(void)
 		goto err_destroy_stream_handle;
 	}
 
-	err = vsock_core_init(&vmci_transport);
+	err = vsock_core_register(&vmci_transport);
 	if (err < 0)
 		goto err_unsubscribe;
 
@@ -2097,7 +2122,7 @@  static void __exit vmci_transport_exit(void)
 		vmci_transport_qp_resumed_sub_id = VMCI_INVALID_ID;
 	}
 
-	vsock_core_exit();
+	vsock_core_unregister(&vmci_transport);
 }
 module_exit(vmci_transport_exit);