From 8a8f8142112c91cc4c22f58fc135c96037691283 Mon Sep 17 00:00:00 2001
From: Mikael Magnusson <mikma@users.sourceforge.net>
Date: Fri, 9 Jun 2023 00:13:54 +0200
Subject: WIP: AlarmManager

---
 .../com/wireguard/android/backend/GoBackend.java   | 34 ++++++++++++++++++----
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java b/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
index 6695c81e..11928d46 100644
--- a/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
+++ b/tunnel/src/main/java/com/wireguard/android/backend/GoBackend.java
@@ -5,6 +5,7 @@
 
 package com.wireguard.android.backend;
 
+import android.app.AlarmManager;
 import android.content.Context;
 import android.content.Intent;
 import android.content.pm.PackageManager;
@@ -23,6 +24,7 @@ import android.os.HandlerThread;
 import android.os.Message;
 import android.os.ParcelFileDescriptor;
 import android.os.Process;
+import android.os.SystemClock;
 import android.system.OsConstants;
 import android.util.Log;
 
@@ -404,6 +406,10 @@ public final class GoBackend implements Backend {
     }
 
     private void Dhcp(VpnService service) throws Exception{
+        if (currentConfig == null || currentTunnel == null || currentTunnelHandle < 0) {
+            return;
+        }
+
         obtainDhcpLease = false;
 
         // Heuristics: Use first ULA address as client address
@@ -462,15 +468,17 @@ public final class GoBackend implements Backend {
         service.protect(wgGetSocketV6(currentTunnelHandle));
         Log.i(TAG, "Dhcp done");
 
-        Message msg = Message.obtain(handler, MSG_DHCP_EXPIRE);
-
         // TODO fetch expiration time from Dhcp leases
-        long delayMillis = 1000 * 3600 * 12 * 3 / 4; // Renew 3/4 * 12h
+        long delayMillis = 1000 * 3600 * 12; // Renew 3/4 * 12h
         //long delayMillis = lease.getValidLifetime().getSeconds() * 1000 + lease.getValidLifetime().getNanos() / 1000;
-        handler.sendMessageDelayed(msg, delayMillis);
 
-        bgp = new Bgp(this, channel, currentTunnel, currentTunnelHandle);
-        bgp.startServer();
+        AlarmManager am = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
+        am.setWindow(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + delayMillis * 3 / 4, delayMillis / 4, null, alarmListener, handler);
+
+        if (bgp != null) {
+            bgp = new Bgp(this, channel, currentTunnel, currentTunnelHandle);
+            bgp.startServer();
+        }
 
         currentTunnel.onDhcpChange(dhcp);
     }
@@ -759,6 +767,9 @@ public final class GoBackend implements Backend {
             currentTunnel = null;
             currentTunnelHandle = -1;
             currentConfig = null;
+
+            AlarmManager am = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
+            am.cancel(alarmListener);
             if (thread != null) {
                 handler = null;
                 thread.quit();
@@ -843,6 +854,8 @@ public final class GoBackend implements Backend {
                     owner.bgp.stopServer();
                     owner.bgp = null;
                 }
+                AlarmManager am = (AlarmManager)owner.context.getSystemService(Context.ALARM_SERVICE);
+                am.cancel(owner.alarmListener);
                 if (owner.thread != null) {
                     owner.handler = null;
                     owner.thread.quit();
@@ -936,4 +949,13 @@ public final class GoBackend implements Backend {
             }
         }
     }
+
+    private AlarmManager.OnAlarmListener alarmListener = new AlarmManager.OnAlarmListener() {
+            @Override
+            public void onAlarm() {
+                if (handler != null) {
+                    handler.sendEmptyMessage(MSG_DHCP_EXPIRE);
+                }
+            }
+        };
 }
-- 
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