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, 21 insertions, 5 deletions

diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index 22b608805a91..1c9e65d7d94d 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -165,6 +165,8 @@ 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);
@@ -367,6 +369,18 @@ 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 {
@@ -430,9 +444,6 @@ static void hvs_open_connection(struct vmbus_channel *chan)
 		new->sk_state = TCP_ESTABLISHED;
 		sk_acceptq_added(sk);
 
-		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;
 
@@ -880,6 +891,11 @@ 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)
 {
@@ -928,7 +944,7 @@ static int __init hvs_init(void)
 	if (ret != 0)
 		return ret;
 
-	ret = vsock_core_init(&hvs_transport);
+	ret = vsock_core_register(&hvs_transport, VSOCK_TRANSPORT_F_G2H);
 	if (ret) {
 		vmbus_driver_unregister(&hvs_drv);
 		return ret;
@@ -939,7 +955,7 @@ 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);
 }