Ask to disable tethering hardware acceleration on Android 8.1+

mobile/src/main/java/be/mygod/vpnhotspot/manage/ManageBar.kt

@@ -3,14 +3,32 @@ package be.mygod.vpnhotspot.manage
 import android.content.ActivityNotFoundException
 import android.content.Context
 import android.content.Intent
+import android.os.Build
+import android.provider.Settings
 import android.view.View
+import androidx.databinding.BaseObservable
 import androidx.recyclerview.widget.RecyclerView
+import be.mygod.vpnhotspot.App.Companion.app
+import be.mygod.vpnhotspot.databinding.ListitemManageBinding
 import com.crashlytics.android.Crashlytics
 
 object ManageBar : Manager() {
-    class ViewHolder(view: View) : RecyclerView.ViewHolder(view), View.OnClickListener {
+    object Data : BaseObservable() {
+        /**
+         * It's hard to change tethering rules with Tethering hardware acceleration enabled for now.
+         *
+         * See also:
+         *   android.provider.Settings.Global.TETHER_OFFLOAD_DISABLED
+         *   https://android.googlesource.com/platform/frameworks/base/+/android-8.1.0_r1/services/core/java/com/android/server/connectivity/tethering/OffloadHardwareInterface.java#45
+         *   https://android.googlesource.com/platform/hardware/qcom/data/ipacfg-mgr/+/master/msm8998/ipacm/src/IPACM_OffloadManager.cpp
+         */
+        val offloadEnabled get() = Build.VERSION.SDK_INT >= 27 && Settings.Global.getInt(app.contentResolver,
+                "tether_offload_disabled", 0) == 0
+    }
+    class ViewHolder(binding: ListitemManageBinding) : RecyclerView.ViewHolder(binding.root), View.OnClickListener {
         init {
-            view.setOnClickListener(this)
+            binding.data = Data
+            binding.root.setOnClickListener(this)
         }
 
         override fun onClick(v: View?) = start(itemView.context)