android: Log retries to the same log file

It's cleared when a new connection is started or there is a manual
retry.

src/frontends/android/app/src/main/java/org/strongswan/android/logic/CharonVpnService.java

@@ -79,6 +79,7 @@ public class CharonVpnService extends VpnService implements Runnable, VpnStateSe
 	public static final String DISCONNECT_ACTION = "org.strongswan.android.CharonVpnService.DISCONNECT";
 	private static final String NOTIFICATION_CHANNEL = "org.strongswan.android.CharonVpnService.VPN_STATE_NOTIFICATION";
 	public static final String LOG_FILE = "charon.log";
+	public static final String KEY_IS_RETRY = "retry";
 	public static final int VPN_STATE_NOTIFICATION_ID = 1;
 
 	private String mLogFile;
@@ -137,6 +138,7 @@ public class CharonVpnService extends VpnService implements Runnable, VpnStateSe
 		if (intent != null)
 		{
 			VpnProfile profile = null;
+			boolean retry = false;
 
 			if (VPN_SERVICE_ACTION.equals(intent.getAction()))
 			{	/* triggered when Always-on VPN is activated */
@@ -159,12 +161,18 @@ public class CharonVpnService extends VpnService implements Runnable, VpnStateSe
 						String password = bundle.getString(VpnProfileDataSource.KEY_PASSWORD);
 						profile.setPassword(password);
 
+						retry = bundle.getBoolean(CharonVpnService.KEY_IS_RETRY, false);
+
 						SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);
 						pref.edit().putString(Constants.PREF_MRU_VPN_PROFILE, profile.getUUID().toString())
 							.apply();
 					}
 				}
 			}
+			if (profile != null && !retry)
+			{	/* delete the log file if this is not an automatic retry */
+				deleteFile(LOG_FILE);
+			}
 			setNextProfile(profile);
 		}
 		return START_NOT_STICKY;

src/frontends/android/app/src/main/java/org/strongswan/android/logic/VpnStateService.java

@@ -295,6 +295,10 @@ public class VpnStateService extends Service
 			/* reset if this is a manual retry or a new connection */
 			mTimeoutProvider.reset();
 		}
+		else
+		{	/* mark this as an automatic retry */
+			profileInfo.putBoolean(CharonVpnService.KEY_IS_RETRY, true);
+		}
 		intent.putExtras(profileInfo);
 		context.startService(intent);
 	}

src/frontends/android/app/src/main/jni/libandroidbridge/charonservice.c

@@ -469,7 +469,7 @@ static void set_options(char *logfile)
 	lib->settings->set_str(lib->settings,
 					"charon.filelog.%s.time_format", "%b %e %T", logfile);
 	lib->settings->set_bool(lib->settings,
-					"charon.filelog.%s.append", FALSE, logfile);
+					"charon.filelog.%s.append", TRUE, logfile);
 	lib->settings->set_bool(lib->settings,
 					"charon.filelog.%s.flush_line", TRUE, logfile);
 	lib->settings->set_int(lib->settings,