Use poll as default monitor method

This should improve compatibility on very broken devices.

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

@@ -14,6 +14,7 @@ import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.net.Routing
 import be.mygod.vpnhotspot.net.Routing.Companion.IPTABLES
 import be.mygod.vpnhotspot.net.monitor.FallbackUpstreamMonitor
+import be.mygod.vpnhotspot.net.monitor.IpMonitor
 import be.mygod.vpnhotspot.net.monitor.UpstreamMonitor
 import be.mygod.vpnhotspot.preference.AlwaysAutoCompleteEditTextPreferenceDialogFragmentCompat
 import be.mygod.vpnhotspot.preference.SharedPreferenceDataStore
@@ -52,6 +53,10 @@ class SettingsPreferenceFragment : PreferenceFragmentCompat() {
             if (cleaned) app.onRoutingsCleaned()
             true
         }
+        findPreference(IpMonitor.KEY).setOnPreferenceChangeListener { _, _ ->
+            SmartSnackbar.make(R.string.settings_restart_required).show()
+            true
+        }
         findPreference("misc.logcat").setOnPreferenceClickListener {
             val context = requireContext()
             val logDir = File(context.cacheDir, "log")

mobile/src/main/java/be/mygod/vpnhotspot/net/monitor/IpMonitor.kt

@@ -1,5 +1,6 @@
 package be.mygod.vpnhotspot.net.monitor
 
+import be.mygod.vpnhotspot.App.Companion.app
 import be.mygod.vpnhotspot.R
 import be.mygod.vpnhotspot.debugLog
 import be.mygod.vpnhotspot.util.thread
@@ -12,6 +13,14 @@ import java.util.concurrent.ScheduledExecutorService
 import java.util.concurrent.TimeUnit
 
 abstract class IpMonitor : Runnable {
+    companion object {
+        const val KEY = "service.ipMonitor"
+    }
+
+    enum class Mode {
+        Monitor, MonitorRoot, Poll
+    }
+
     private class MonitorFailure : RuntimeException()
     private class FlushFailure : RuntimeException()
     protected abstract val monitoredObject: String
@@ -50,13 +59,18 @@ abstract class IpMonitor : Runnable {
 
     init {
         thread("${javaClass.simpleName}-input") {
-            // monitor may get rejected by SELinux
+            val mode = Mode.valueOf(app.pref.getString(KEY, Mode.Monitor.toString()) ?: "")
+            if (mode != Mode.Poll) {
+                if (mode != Mode.MonitorRoot) {
+                    // monitor may get rejected by SELinux enforcing
                     handleProcess(ProcessBuilder("ip", "monitor", monitoredObject))
                     if (destroyed) return@thread
+                }
                 handleProcess(ProcessBuilder("su", "-c", "exec ip monitor $monitoredObject"))
                 if (destroyed) return@thread
                 Timber.w("Failed to set up monitor, switching to polling")
                 Timber.i(MonitorFailure())
+            }
             val pool = Executors.newScheduledThreadPool(1)
             pool.scheduleAtFixedRate(this, 1, 1, TimeUnit.SECONDS)
             this.pool = pool

mobile/src/main/res/drawable/ic_hardware_device_hub.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="M17,16l-4,-4V8.82C14.16,8.4 15,7.3 15,6c0,-1.66 -1.34,-3 -3,-3S9,4.34 9,6c0,1.3 0.84,2.4 2,2.82V12l-4,4H3v5h5v-3.05l4,-4.2 4,4.2V21h5v-5h-4z"/>
+</vector>

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

@@ -88,6 +88,10 @@
     <string name="settings_service_wifi_lock_none">系统默认</string>
     <string name="settings_service_wifi_lock_full">开（防止服务自动关闭）</string>
     <string name="settings_service_wifi_lock_high_perf">高性能模式（更快消耗电池）</string>
+    <string name="settings_service_ip_monitor">网络状态监听模式</string>
+    <string name="settings_service_ip_monitor_monitor">Netlink 监听</string>
+    <string name="settings_service_ip_monitor_monitor_root">Netlink 监听 (root)</string>
+    <string name="settings_service_ip_monitor_poll">轮询</string>
     <string name="settings_service_dns">备用 DNS 服务器[:端口]</string>
     <string name="settings_service_upstream">上游网络接口</string>
     <string name="settings_service_upstream_auto">自动检测系统 VPN</string>
@@ -105,6 +109,7 @@
     <string name="settings_misc_donate">捐款</string>
     <string name="settings_misc_donate_summary">请给我钱</string>
     <string name="settings_misc_donate_more">PayPal, Flattr 等其他方式…</string>
+    <string name="settings_restart_required">重启应用以应用新的设置。</string>
 
     <string name="notification_tethering_title">VPN 共享已启用</string>
     <string name="notification_channel_tethering">VPN 共享服务</string>

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

@@ -10,4 +10,14 @@
         <item>Full</item>
         <item>HighPerf</item>
     </string-array>
+    <string-array name="settings_service_ip_monitor">
+        <item>@string/settings_service_ip_monitor_monitor</item>
+        <item>@string/settings_service_ip_monitor_monitor_root</item>
+        <item>@string/settings_service_ip_monitor_poll</item>
+    </string-array>
+    <string-array name="settings_service_ip_monitor_values">
+        <item>Monitor</item>
+        <item>MonitorRoot</item>
+        <item>Poll</item>
+    </string-array>
 </resources>

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

@@ -96,6 +96,10 @@
     <string name="settings_service_wifi_lock_none">System default</string>
     <string name="settings_service_wifi_lock_full">On (prevents service auto-shutdowns)</string>
     <string name="settings_service_wifi_lock_high_perf">High Performance Mode (consumes more power)</string>
+    <string name="settings_service_ip_monitor">Network status monitor mode</string>
+    <string name="settings_service_ip_monitor_monitor">Netlink monitor</string>
+    <string name="settings_service_ip_monitor_monitor_root">Netlink monitor with root</string>
+    <string name="settings_service_ip_monitor_poll">Poll</string>
     <string name="settings_service_dns">Fallback DNS server[:port]</string>
     <string name="settings_service_upstream">Upstream network interface</string>
     <string name="settings_service_upstream_auto">Auto detect system VPN</string>
@@ -114,6 +118,7 @@
     <string name="settings_misc_donate">Donate</string>
     <string name="settings_misc_donate_summary">I love money</string>
     <string name="settings_misc_donate_more">PayPal, Flattr, more…</string>
+    <string name="settings_restart_required">Restart this app to apply this setting.</string>
 
     <string name="notification_tethering_title">VPN tethering active</string>
     <string name="notification_channel_tethering">VPN Tethering Service</string>

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

@@ -61,6 +61,14 @@
             android:key="service.repeater.startOnBoot"
             android:icon="@drawable/ic_action_autorenew"
             android:title="@string/settings_service_repeater_start_on_boot"/>
+        <SimpleMenuPreference
+            android:key="service.ipMonitor"
+            android:icon="@drawable/ic_hardware_device_hub"
+            android:entries="@array/settings_service_ip_monitor"
+            android:entryValues="@array/settings_service_ip_monitor_values"
+            android:defaultValue="Poll"
+            android:summary="%s"
+            android:title="@string/settings_service_ip_monitor"/>
         <Preference
             android:key="misc.logcat"
             android:icon="@drawable/ic_action_bug_report"