Prevent calling callback in synchronized

mobile/src/main/java/be/mygod/vpnhotspot/net/monitor/DefaultNetworkMonitor.kt

@@ -85,7 +85,7 @@ object DefaultNetworkMonitor : UpstreamMonitor() {
             } catch (e: SecurityException) {
                 // SecurityException would be thrown in requestNetwork on Android 6.0 thanks to Google's stupid bug
                 if (Build.VERSION.SDK_INT != 23) throw e
-                callback.onFallback()
+                GlobalScope.launch { callback.onFallback() }
                 return
             }
             registered = true

mobile/src/main/java/be/mygod/vpnhotspot/net/monitor/InterfaceMonitor.kt

@@ -9,8 +9,11 @@ class InterfaceMonitor(val iface: String) : UpstreamMonitor() {
         val old = currentIface != null
         if (present == old) return
         currentIface = if (present) iface else null
-        if (present) {
-            val lp = currentLinkProperties ?: return@synchronized
+        if (present) Pair(iface, currentLinkProperties) else null
+    }.let { pair ->
+        if (pair != null) {
+            val (iface, lp) = pair
+            lp ?: return
             callbacks.forEach { it.onAvailable(iface, lp) }
         } else callbacks.forEach { it.onLost() }
     }

mobile/src/main/java/be/mygod/vpnhotspot/net/monitor/IpNeighbourMonitor.kt

@@ -15,14 +15,15 @@ class IpNeighbourMonitor private constructor() : IpMonitor() {
         var instance: IpNeighbourMonitor? = null
 
         fun registerCallback(callback: Callback) = synchronized(callbacks) {
-            if (!callbacks.add(callback)) return@synchronized
+            if (!callbacks.add(callback)) return@synchronized null
             var monitor = instance
             if (monitor == null) {
                 monitor = IpNeighbourMonitor()
                 instance = monitor
                 monitor.flush()
-            } else callback.onIpNeighbourAvailable(monitor.neighbours.values)
-        }
+                null
+            } else monitor.neighbours.values
+        }?.let { callback.onIpNeighbourAvailable(it) }
         fun unregisterCallback(callback: Callback) = synchronized(callbacks) {
             if (!callbacks.remove(callback) || callbacks.isNotEmpty()) return@synchronized
             instance?.destroy()