qemu/qmp: Add netdev_add with chardev support

In order to be able to hotplug network devices such as vhost user
net, we need to be able to define a previously declared chardev as
a parameter of this new network device.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

qemu/qmp.go

@@ -764,6 +764,22 @@ func (q *QMP) ExecuteNetdevAdd(ctx context.Context, netdevType, netdevID, ifname
 	return q.executeCommand(ctx, "netdev_add", args, nil)
 }
 
+// ExecuteNetdevChardevAdd adds a Net device to a QEMU instance
+// using the netdev_add command. netdevID is the id of the device to add.
+// Must be valid QMP identifier.
+func (q *QMP) ExecuteNetdevChardevAdd(ctx context.Context, netdevType, netdevID, chardev string, queues int) error {
+	args := map[string]interface{}{
+		"type":    netdevType,
+		"id":      netdevID,
+		"chardev": chardev,
+	}
+	if queues > 1 {
+		args["queues"] = queues
+	}
+
+	return q.executeCommand(ctx, "netdev_add", args, nil)
+}
+
 // ExecuteNetdevAddByFds adds a Net device to a QEMU instance
 // using the netdev_add command by fds and vhostfds. netdevID is the id of the device to add.
 // Must be valid QMP identifier.

qemu/qmp_test.go

@@ -425,6 +425,28 @@ func TestQMPNetdevAdd(t *testing.T) {
 	<-disconnectedCh
 }
 
+// Checks that the netdev_add command is correctly sent.
+//
+// We start a QMPLoop, send the netdev_add command and stop the loop.
+//
+// The netdev_add command should be correctly sent and the QMP loop should
+// exit gracefully.
+func TestQMPNetdevChardevAdd(t *testing.T) {
+	connectedCh := make(chan *QMPVersion)
+	disconnectedCh := make(chan struct{})
+	buf := newQMPTestCommandBuffer(t)
+	buf.AddCommand("netdev_add", nil, "return", nil)
+	cfg := QMPConfig{Logger: qmpTestLogger{}}
+	q := startQMPLoop(buf, cfg, connectedCh, disconnectedCh)
+	q.version = checkVersion(t, connectedCh)
+	err := q.ExecuteNetdevChardevAdd(context.Background(), "tap", "br0", "chr0", 8)
+	if err != nil {
+		t.Fatalf("Unexpected error %v", err)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}
+
 // Checks that the netdev_add command with fds is correctly sent.
 //
 // We start a QMPLoop, send the netdev_add command with fds and stop the loop.