Add shortcut for tether offload

Fix #41.

README.md

@@ -98,8 +98,6 @@ Search the [issue tracker](https://github.com/Mygod/VPNHotspot/issues) for more.
 
 ### [What changes exactly can this app do to my system? (and how to revert them)](https://github.com/Mygod/VPNHotspot/issues/8#issuecomment-448529512)
 
-### [Unable to find "Tethering hardware acceleration" in Developer options?](https://github.com/Mygod/VPNHotspot/issues/41#issuecomment-425732001)
-
 ### [No root?](https://github.com/Mygod/VPNHotspot/issues/62)
 
 ### Failed to create group due to internal error/repeater shuts down after a while?

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

@@ -10,6 +10,7 @@ import androidx.preference.PreferenceFragmentCompat
 import androidx.preference.SwitchPreference
 import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.net.Routing.Companion.IPTABLES
+import be.mygod.vpnhotspot.net.TetherOffloadManager
 import be.mygod.vpnhotspot.net.monitor.IpMonitor
 import be.mygod.vpnhotspot.net.monitor.UpstreamMonitor
 import be.mygod.vpnhotspot.net.wifi.WifiDoubleLock
@@ -17,6 +18,7 @@ import be.mygod.vpnhotspot.preference.AlwaysAutoCompleteEditTextPreferenceDialog
 import be.mygod.vpnhotspot.preference.SharedPreferenceDataStore
 import be.mygod.vpnhotspot.util.RootSession
 import be.mygod.vpnhotspot.util.launchUrl
+import be.mygod.vpnhotspot.widget.SmartSnackbar
 import com.google.android.material.snackbar.Snackbar
 import timber.log.Timber
 import java.io.File
@@ -32,6 +34,21 @@ class SettingsPreferenceFragment : PreferenceFragmentCompat() {
         preferenceManager.preferenceDataStore = SharedPreferenceDataStore(app.pref)
         RoutingManager.masqueradeMode = RoutingManager.masqueradeMode   // flush default value
         addPreferencesFromResource(R.xml.pref_settings)
+        findPreference<SwitchPreference>("system.enableTetherOffload")!!.apply {
+            if (Build.VERSION.SDK_INT >= 27) {
+                isChecked = TetherOffloadManager.enabled
+                setOnPreferenceChangeListener { _, newValue ->
+                    try {
+                        TetherOffloadManager.enabled = newValue as Boolean
+                        TetherOffloadManager.enabled == newValue
+                    } catch (e: Exception) {
+                        Timber.d(e)
+                        SmartSnackbar.make(e).show()
+                        false
+                    }
+                }
+            } else parent!!.removePreference(this)
+        }
         val boot = findPreference<SwitchPreference>("service.repeater.startOnBoot")!!
         if (RepeaterService.supported) {
             boot.setOnPreferenceChangeListener { _, value ->

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

@@ -3,14 +3,13 @@ package be.mygod.vpnhotspot.manage
 import android.content.Context
 import android.content.Intent
 import android.os.Build
-import android.provider.Settings
 import android.view.View
 import androidx.core.os.bundleOf
 import androidx.databinding.BaseObservable
 import androidx.recyclerview.widget.RecyclerView
-import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.DebugHelper
 import be.mygod.vpnhotspot.databinding.ListitemManageBinding
+import be.mygod.vpnhotspot.net.TetherOffloadManager
 
 object ManageBar : Manager() {
     private const val TAG = "ManageBar"
@@ -19,16 +18,7 @@ object ManageBar : Manager() {
     private const val SETTINGS_2 = "com.android.settings.TetherSettings"
 
     object Data : BaseObservable() {
-        /**
+        val offloadEnabled get() = Build.VERSION.SDK_INT >= 27 && TetherOffloadManager.enabled
-         * 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 {

mobile/src/main/java/be/mygod/vpnhotspot/net/TetherOffloadManager.kt

@@ -0,0 +1,27 @@
+package be.mygod.vpnhotspot.net
+
+import android.provider.Settings
+import androidx.annotation.RequiresApi
+import be.mygod.vpnhotspot.App.Companion.app
+import be.mygod.vpnhotspot.util.RootSession
+
+/**
+ * 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
+ */
+@RequiresApi(27)
+object TetherOffloadManager {
+    private const val TETHER_OFFLOAD_DISABLED = "tether_offload_disabled"
+    @JvmStatic
+    var enabled: Boolean
+        get() = Settings.Global.getInt(app.contentResolver, TETHER_OFFLOAD_DISABLED, 0) == 0
+        set(value) {
+            RootSession.use {
+                it.exec("settings put global $TETHER_OFFLOAD_DISABLED ${if (value) 0 else 1}")
+            }
+        }
+}

mobile/src/main/res/drawable/ic_device_battery_charging_full.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0"
+        android:tint="?attr/colorControlNormal">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M15.67,4H14V2h-4v2H8.33C7.6,4 7,4.6 7,5.33v15.33C7,21.4 7.6,22 8.33,22h7.33c0.74,0 1.34,-0.6 1.34,-1.33V5.33C17,4.6 16.4,4 15.67,4zM11,20v-5.5H9L13,7v5.5h2L11,20z"/>
+</vector>

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

@@ -103,6 +103,8 @@
     <string name="settings_service_clean_summary">将修改的设置应用到当前启用的服务上。也可用于修复偶尔会发生的竞态条件。</string>
     <string name="settings_service_dhcp_workaround">尝试修复 DHCP</string>
     <string name="settings_service_dhcp_workaround_summary">如果设备无法获取 IP 地址，尝试打开这个选项。</string>
+    <string name="settings_system_tether_offload">网络共享硬件加速</string>
+    <string name="settings_system_tether_offload_summary">系统“开发者选项”的快捷方式</string>
     <string name="settings_misc">杂项</string>
     <string name="settings_help">帮助</string>
     <string name="settings_misc_logcat">导出调试信息</string>

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

@@ -109,6 +109,8 @@
     <string name="settings_service_clean">Clean/reapply routing rules</string>
     <string name="settings_service_clean_summary">Update changed settings to current active services. Can also fix rare
         race conditions.</string>
+    <string name="settings_system_tether_offload">Tethering hardware acceleration</string>
+    <string name="settings_system_tether_offload_summary">Shortcut to system developer options</string>
     <string name="settings_misc">Misc</string>
     <string name="settings_help">Help</string>
     <string name="settings_misc_logcat">Export debug information</string>

mobile/src/main/res/xml/pref_settings.xml

@@ -28,6 +28,12 @@
             app:title="@string/settings_service_disable_ipv6"
             app:summary="@string/settings_service_disable_ipv6_summary"
             app:defaultValue="true"/>
+        <SwitchPreference
+            app:key="system.enableTetherOffload"
+            app:persistent="false"
+            app:icon="@drawable/ic_device_battery_charging_full"
+            app:title="@string/settings_system_tether_offload"
+            app:summary="@string/settings_system_tether_offload_summary"/>
         <SwitchPreference
             app:key="service.dhcpWorkaround"
             app:icon="@drawable/ic_action_build"