fix a crash on devices without tun.ko

src/main/res/values/strings.xml

@@ -58,6 +58,7 @@
   <string name="service_failed">Please check your network status and try again.</string>
   <string name="stop">Stop the service</string>
   <string name="vpn_status">You can only disable the VPN service through the notification bar.</string>
+  <string name="vpn_error">Unable to start VPN service: "%s". It seems a compatibility issue on your device. Please consider to use ROOT mode instead.</string>
 
   <!-- alert category -->
   <string name="ok_iknow">OK</string>

src/main/scala/com/github/shadowsocks/ShadowVpnService.scala

@@ -79,6 +79,8 @@ class ShadowVpnService extends VpnService {
   val MSG_CONNECT_FAIL: Int = 3
   val MSG_HOST_CHANGE: Int = 4
   val MSG_STOP_SELF: Int = 5
+  val MSG_VPN_ERROR: Int = 6
+
   val VPN_MTU = 1500
 
   val PRIVATE_VLAN_10 = "10.254.254.%d"
@@ -107,6 +109,7 @@ class ShadowVpnService extends VpnService {
       msg.what match {
         case MSG_CONNECT_START =>
           ed.putBoolean("isConnecting", true)
+          ed.remove("vpnError")
         case MSG_CONNECT_FINISH =>
           ed.putBoolean("isConnecting", false)
         case MSG_CONNECT_SUCCESS =>
@@ -115,6 +118,8 @@ class ShadowVpnService extends VpnService {
           ed.putBoolean("isRunning", false)
         case MSG_HOST_CHANGE =>
           ed.putString("appHost", appHost)
+        case MSG_VPN_ERROR =>
+          if (msg.obj != null) ed.putString("vpnError", msg.obj.asInstanceOf[String])
         case MSG_STOP_SELF =>
           destroy()
           stopSelf()
@@ -310,7 +315,19 @@ class ShadowVpnService extends VpnService {
       }
     }
 
-    conn = builder.establish()
+    try {
+      conn = builder.establish()
+    } catch {
+      case ex: IllegalStateException => {
+        val msg = new Message()
+        msg.what = MSG_VPN_ERROR
+        msg.obj = ex.getMessage
+        handler.sendMessage(msg)
+        conn = null
+      }
+      case ex: Exception => conn = null
+    }
+
     if (conn == null) {
       stopSelf()
       return

src/main/scala/com/github/shadowsocks/Shadowsocks.scala

@@ -471,16 +471,24 @@ class Shadowsocks
           switchButton.setChecked(false)
           Crouton.cancelAllCroutons()
         }
+
+        val msg = settings.getString("vpnError", null)
+        if (msg != null) {
+          Crouton.cancelAllCroutons()
+          val style = new Style.Builder()
+            .setBackgroundColorValue(Style.holoRedLight)
+            .setDuration(Style.DURATION_INFINITE)
+            .build()
+          Crouton.makeText(this, getString(R.string.vpn_error).format(msg), style).show()
+        }
       }
     }
     if (key == "isConnecting") {
       if (settings.getBoolean("isConnecting", false)) {
-        Log.d(Shadowsocks.TAG, "Connecting start")
         if (progressDialog == null) {
           progressDialog = ProgressDialog.show(this, "", getString(R.string.connecting), true, true)
         }
       } else {
-        Log.d(Shadowsocks.TAG, "Connecting finish")
         if (progressDialog != null) {
           progressDialog.dismiss()
           progressDialog = null
@@ -661,4 +669,4 @@ class Shadowsocks
     val alert: AlertDialog = builder.create
     alert.show()
   }
-}
+}