qemu/qmp: add function for hotplug network by fds

Implement function to hotplug a network device to QEMU by fds.
Macvtap can only be hotplug by this way.

Signed-off-by: Ruidong Cao <caoruidong@huawei.com>

qemu/qmp.go

@@ -29,6 +29,7 @@ import (
 	"time"
 
 	"context"
+	"strings"
 )
 
 // QMPLog is a logging interface used by the qemu package to log various
@@ -755,6 +756,23 @@ func (q *QMP) ExecuteNetdevAdd(ctx context.Context, netdevType, netdevID, ifname
 	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.
+func (q *QMP) ExecuteNetdevAddByFds(ctx context.Context, netdevType, netdevID string, fdNames, vhostFdNames []string) error {
+	fdNameStr := strings.Join(fdNames, ":")
+	vhostFdNameStr := strings.Join(vhostFdNames, ":")
+	args := map[string]interface{}{
+		"type":     netdevType,
+		"id":       netdevID,
+		"fds":      fdNameStr,
+		"vhost":    "on",
+		"vhostfds": vhostFdNameStr,
+	}
+
+	return q.executeCommand(ctx, "netdev_add", args, nil)
+}
+
 // ExecuteNetdevDel deletes a Net device from a QEMU instance
 // using the netdev_del command. netdevID is the id of the device to delete.
 func (q *QMP) ExecuteNetdevDel(ctx context.Context, netdevID string) error {

qemu/qmp_test.go

@@ -387,6 +387,28 @@ func TestQMPNetdevAdd(t *testing.T) {
 	<-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.
+//
+// The netdev_add command with fds should be correctly sent and the QMP loop should
+// exit gracefully.
+func TestQMPNetdevAddByFds(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.ExecuteNetdevAddByFds(context.Background(), "tap", "br0", nil, nil)
+	if err != nil {
+		t.Fatalf("Unexpected error %v", err)
+	}
+	q.Shutdown()
+	<-disconnectedCh
+}
+
 // Checks that the netdev_del command is correctly sent.
 //
 // We start a QMPLoop, send the netdev_del command and stop the loop.