vsock: add multi-transports support

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 regardless of the transports
- vsock_core_init() and vsock_core_exit() are renamed to
  vsock_core_register() and vsock_core_unregister()
- vsock_core_register() has a feature parameter (H2G, G2H, DGRAM)
  to identify which directions the transport can handle and if it's
  support DGRAM (only vmci)
- 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 guest->host transport;
  - remote CID == local_cid (guest->host transport) will use guest->host
    transport for loopback (host->guest transports don't support loopback);
  - remote CID > VMADDR_CID_HOST will use host->guest 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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 3 deletions

diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
index b6c8c9cc8d72..86030ecb53dd 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;
@@ -1017,6 +1018,16 @@ 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)) {
+		vmci_transport_send_reset(sk, pkt);
+		sock_put(pending);
+		return err;
+	}
+
 	/* If the proposed size fits within our min/max, accept it. Otherwise
 	 * propose our own size.
 	 */
@@ -2008,7 +2019,7 @@ 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 = {
 	.init = vmci_transport_socket_init,
 	.destruct = vmci_transport_destruct,
 	.release = vmci_transport_release,
@@ -2038,10 +2049,25 @@ 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 features = VSOCK_TRANSPORT_F_DGRAM | VSOCK_TRANSPORT_F_H2G;
+	int cid;
 	int err;
 
+	cid = vmci_get_context_id();
+
+	if (cid == VMCI_INVALID_ID)
+		return -EINVAL;
+
+	if (cid != VMCI_HOST_CONTEXT_ID)
+		features |= VSOCK_TRANSPORT_F_G2H;
+
 	/* Create the datagram handle that we will use to send and receive all
 	 * VSocket control messages for this context.
 	 */
@@ -2065,7 +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, features);
 	if (err < 0)
 		goto err_unsubscribe;
 
@@ -2096,7 +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);