Ask to disable tethering hardware acceleration on Android 8.1+

README.md

@@ -92,6 +92,10 @@ Private system configurations:
 
 Other:
 
+* (since API 27) `android.provider.Settings.Global.TETHER_OFFLOAD_DISABLED` is assumed to be
+  `"tether_offload_disabled"`.
+* (since API 27) `com.android.server.connectivity.tethering.OffloadHardwareInterface.DEFAULT_TETHER_OFFLOAD_DISABLED`
+  is assumed to be 0.
 * Activity `com.android.settings/.Settings$TetherSettingsActivity` is assumed to be exported;
 * Several constants in `ConnectivityManager` is assumed to be defined as in `TetheringManager.kt`;
 * `android.net.conn.TETHER_STATE_CHANGED` is assumed to be a sticky broadcast.

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)

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

@@ -5,8 +5,8 @@ import android.view.LayoutInflater
 import android.view.ViewGroup
 import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.RecyclerView
-import be.mygod.vpnhotspot.R
 import be.mygod.vpnhotspot.databinding.ListitemInterfaceBinding
+import be.mygod.vpnhotspot.databinding.ListitemManageBinding
 import be.mygod.vpnhotspot.databinding.ListitemRepeaterBinding
 
 abstract class Manager {
@@ -26,7 +26,7 @@ abstract class Manager {
         fun createViewHolder(inflater: LayoutInflater, parent: ViewGroup, type: Int) = when (type) {
             VIEW_TYPE_INTERFACE ->
                 InterfaceManager.ViewHolder(ListitemInterfaceBinding.inflate(inflater, parent, false))
-            VIEW_TYPE_MANAGE -> ManageBar.ViewHolder(inflater.inflate(R.layout.listitem_manage, parent, false))
+            VIEW_TYPE_MANAGE -> ManageBar.ViewHolder(ListitemManageBinding.inflate(inflater, parent, false))
             VIEW_TYPE_WIFI, VIEW_TYPE_USB, VIEW_TYPE_BLUETOOTH, VIEW_TYPE_WIFI_LEGACY ->
                 TetherManager.ViewHolder(ListitemInterfaceBinding.inflate(inflater, parent, false))
             VIEW_TYPE_LOCAL_ONLY_HOTSPOT -> @TargetApi(26) {

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

@@ -104,6 +104,11 @@ class TetheringFragment : Fragment(), ServiceConnection {
         return binding.root
     }
 
+    override fun onResume() {
+        super.onResume()
+        if (Build.VERSION.SDK_INT >= 27) ManageBar.Data.notifyChange()
+    }
+
     override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
         if (requestCode == START_LOCAL_ONLY_HOTSPOT) @TargetApi(26) {
             if (grantResults.firstOrNull() == PackageManager.PERMISSION_GRANTED) {

mobile/src/main/res/layout/listitem_manage.xml

@@ -1,6 +1,13 @@
 <?xml version="1.0" encoding="utf-8"?>
+<layout
+    xmlns:android="http://schemas.android.com/apk/res/android">
+    <data>
+        <import type="android.view.View"/>
+        <variable
+            name="data"
+            type="be.mygod.vpnhotspot.manage.ManageBar.Data"/>
+    </data>
     <LinearLayout
-    xmlns:android="http://schemas.android.com/apk/res/android"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:focusable="true"
@@ -18,12 +25,26 @@
             android:layout_width="16dp"
             android:layout_height="0dp"/>
 
-    <TextView
+        <LinearLayout
             android:layout_width="0dp"
             android:layout_height="wrap_content"
             android:layout_weight="1"
             android:layout_gravity="center_vertical"
+            android:orientation="vertical">
+
+            <TextView
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
                 android:textAppearance="@style/TextAppearance.AppCompat.Subhead"
                 android:text="@string/tethering_manage"/>
 
+            <TextView
+                android:id="@+id/offloadEnabled"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:visibility="@{data.offloadEnabled ? View.VISIBLE : View.GONE}"
+                android:text="@string/tethering_manage_offload_enabled"/>
         </LinearLayout>
+
+    </LinearLayout>
+</layout>

mobile/src/main/res/values-zh-rCN/strings.xml

@@ -38,6 +38,7 @@
     <string name="tethering_temp_hotspot_failure_tethering_disallowed">共享被禁用</string>
 
     <string name="tethering_manage">管理系统共享…</string>
+    <string name="tethering_manage_offload_enabled">若 VPN 共享无法使用，请尝试禁用“开发者选项”中的“网络共享硬件加速”。</string>
     <!--
      Values copied from:
         * https://android.googlesource.com/platform/packages/apps/Settings/+/7686ef8/res/xml/tether_prefs.xml

mobile/src/main/res/values/strings.xml

@@ -49,6 +49,8 @@
     <string name="tethering_temp_hotspot_failure_tethering_disallowed">tethering disallowed</string>
 
     <string name="tethering_manage">Manage system tethering…</string>
+    <string name="tethering_manage_offload_enabled">Please disable Tethering hardware acceleration in Developer options
+        if VPN tethering does not work.</string>
     <string name="tethering_manage_usb">USB tethering</string>
     <string name="tethering_manage_wifi">Wi\u2011Fi hotspot</string>
     <string name="tethering_manage_wifi_legacy">Wi\u2011Fi hotspot (legacy)</string>