bluetooth: add soft rfkill unblock, wait for adapter to become available

instead of forfeiting subscription

fixes #2922
fixes #1537

core/internal/server/bluez/manager.go

@@ -43,10 +43,10 @@ func NewManager() (*Manager, error) {
 	broker := NewSubscriptionBroker(m.broadcastPairingPrompt)
 	m.promptBroker = broker
 
-	adapter, err := m.findAdapter()
+	adapter, err := findAdapter(conn)
 	if err != nil {
 		conn.Close()
-		return nil, fmt.Errorf("no bluetooth adapter found: %w", err)
+		return nil, err
 	}
 	m.adapterPath = adapter
 
@@ -74,12 +74,12 @@ func NewManager() (*Manager, error) {
 	return m, nil
 }
 
-func (m *Manager) findAdapter() (dbus.ObjectPath, error) {
-	obj := m.dbusConn.Object(bluezService, dbus.ObjectPath("/"))
+func findAdapter(conn *dbus.Conn) (dbus.ObjectPath, error) {
+	obj := conn.Object(bluezService, dbus.ObjectPath("/"))
 	var objects map[dbus.ObjectPath]map[string]map[string]dbus.Variant
 
 	if err := obj.Call(objectMgrIface+".GetManagedObjects", 0).Store(&objects); err != nil {
-		return "", err
+		return "", fmt.Errorf("%w: %v", ErrNoAdapter, err)
 	}
 
 	for path, interfaces := range objects {
@@ -89,7 +89,7 @@ func (m *Manager) findAdapter() (dbus.ObjectPath, error) {
 		}
 	}
 
-	return "", fmt.Errorf("no adapter found")
+	return "", ErrNoAdapter
 }
 
 func (m *Manager) initialize() error {
@@ -487,6 +487,11 @@ func (m *Manager) StopDiscovery() error {
 }
 
 func (m *Manager) SetPowered(powered bool) error {
+	if powered {
+		if err := rfkillUnblockBluetooth(); err != nil {
+			log.Debugf("[BluezManager] rfkill unblock failed: %v", err)
+		}
+	}
 	obj := m.dbusConn.Object(bluezService, m.adapterPath)
 	return obj.Call(propertiesIface+".Set", 0, adapter1Iface, "Powered", dbus.MakeVariant(powered)).Err
 }

core/internal/server/bluez/rfkill_freebsd.go

@@ -0,0 +1,5 @@
+package bluez
+
+func rfkillUnblockBluetooth() error {
+	return nil
+}

core/internal/server/bluez/rfkill_linux.go

@@ -0,0 +1,19 @@
+package bluez
+
+import "os"
+
+// linux/rfkill.h: struct rfkill_event { __u32 idx; __u8 type; __u8 op; __u8 soft; __u8 hard; },
+// RFKILL_TYPE_BLUETOOTH=2, RFKILL_OP_CHANGE_ALL=3
+func rfkillUnblockBluetooth() error {
+	f, err := os.OpenFile("/dev/rfkill", os.O_WRONLY, 0)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	var event [8]byte
+	event[4] = 2
+	event[5] = 3
+	_, err = f.Write(event[:])
+	return err
+}

core/internal/server/bluez/watcher.go

@@ -0,0 +1,46 @@
+package bluez
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/godbus/dbus/v5"
+)
+
+var ErrNoAdapter = errors.New("no bluetooth adapter found")
+
+func WaitForAdapter() error {
+	conn, err := dbus.ConnectSystemBus()
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	if err := conn.AddMatchSignal(
+		dbus.WithMatchInterface(objectMgrIface),
+		dbus.WithMatchMember("InterfacesAdded"),
+	); err != nil {
+		return err
+	}
+
+	signals := make(chan *dbus.Signal, 64)
+	conn.Signal(signals)
+
+	if _, err := findAdapter(conn); err == nil {
+		return nil
+	}
+
+	for sig := range signals {
+		if sig == nil || sig.Name != objectMgrIface+".InterfacesAdded" || len(sig.Body) < 2 {
+			continue
+		}
+		ifaces, ok := sig.Body[1].(map[string]map[string]dbus.Variant)
+		if !ok {
+			continue
+		}
+		if _, ok := ifaces[adapter1Iface]; ok {
+			return nil
+		}
+	}
+	return fmt.Errorf("dbus signal stream closed")
+}

core/internal/server/server.go

@@ -1668,10 +1668,21 @@ func (s *Server) Serve(printDocs bool) error {
 	}()
 
 	go func() {
-		if err := InitializeBluezManager(); err != nil {
+		for {
+			err := InitializeBluezManager()
+			if err == nil {
+				notifyCapabilityChange()
+				return
+			}
 			log.Warnf("Bluez manager unavailable: %v", err)
-		} else {
-			notifyCapabilityChange()
+			if !errors.Is(err, bluez.ErrNoAdapter) {
+				return
+			}
+			if err := bluez.WaitForAdapter(); err != nil {
+				log.Warnf("Bluetooth adapter watch failed: %v", err)
+				return
+			}
+			log.Info("Bluetooth adapter appeared, initializing bluez manager")
 		}
 	}()