Fix VPN connections change handlers

mobile/src/main/java/be/mygod/vpnhotspot/RepeaterService.kt

@@ -160,7 +160,7 @@ class RepeaterService : Service(), WifiP2pManager.ChannelListener, VpnListener.C
             }
             Status.ACTIVE -> {
                 val routing = routing
-                assert(!routing!!.started)
+                check(!routing!!.started)
                 initRouting(ifname, routing.downstream, routing.hostAddress)
             }
             else -> throw RuntimeException("RepeaterService is in unexpected state when receiving onAvailable")
@@ -248,13 +248,13 @@ class RepeaterService : Service(), WifiP2pManager.ChannelListener, VpnListener.C
         })
     }
     private fun unregisterReceiver() {
-        VpnListener.unregisterCallback(this)
         if (receiverRegistered) {
             unregisterReceiver(receiver)
             receiverRegistered = false
         }
     }
     private fun clean() {
+        VpnListener.unregisterCallback(this)
         unregisterReceiver()
         if (routing?.stop() == false)
             Toast.makeText(this, "Something went wrong, please check logcat.", Toast.LENGTH_SHORT).show()

mobile/src/main/java/be/mygod/vpnhotspot/Routing.kt

@@ -41,7 +41,8 @@ class Routing(private val upstream: String, val downstream: String, ownerAddress
      */
     fun rule(): Routing {
         startScript.add("ip rule add from all iif $downstream lookup $upstream priority 17900")
-        stopScript.addFirst("ip rule del from all iif $downstream lookup $upstream priority 17900")
+        // by the time stopScript is called, table entry for upstream may already get removed
+        stopScript.addFirst("ip rule del from all iif $downstream priority 17900")
         return this
     }
 

mobile/src/main/java/be/mygod/vpnhotspot/TetheringService.kt

@@ -59,7 +59,7 @@ class TetheringService : Service(), VpnListener.Callback {
     }
 
     override fun onAvailable(ifname: String) {
-        assert(upstream == null || upstream == ifname)
+        check(upstream == null || upstream == ifname)
         upstream = ifname
         for ((downstream, value) in routings) if (value == null) {
             val routing = Routing(ifname, downstream).rule().forward().dnsRedirect(app.dns)
@@ -68,7 +68,7 @@ class TetheringService : Service(), VpnListener.Callback {
     }
 
     override fun onLost(ifname: String) {
-        assert(upstream == null || upstream == ifname)
+        check(upstream == null || upstream == ifname)
         upstream = null
         for ((iface, routing) in routings) {
             routing?.stop()

mobile/src/main/java/be/mygod/vpnhotspot/VpnListener.kt

@@ -31,7 +31,7 @@ object VpnListener : ConnectivityManager.NetworkCallback() {
     private val available = HashMap<Network, String>()
     override fun onAvailable(network: Network) {
         val ifname = connectivityManager.getLinkProperties(network)?.interfaceName ?: return
-        available.put(network, ifname)
+        if (available.put(network, ifname) != null) return
         debugLog(TAG, "onAvailable: $ifname")
         callbacks.forEach { it.onAvailable(ifname) }
     }