android: 2.13.15 - exponential direct-dst cooldown, double-start guard, flap-aware auto-connect

Log-driven fixes from the 10-04 diag/charon analysis:
- direct_tcp: negative-cache window now escalates 45s x2 up to 5 min
  (Telegram was opening ~3000 connects/h to each of two dead hosts,
  waking the radio for every leaked 45s probe); skip the unconditional
  fresh-socket retry on ECONNREFUSED (a refusal is deterministic on the
  network the socket is bound to; roam-time sockets are already aborted
  by reprotect)
- new dead-destination diag line (dst, fail count, cooldown) via JNI
  callback when the window escalates or hits every 100th failure
- VpnStateService: double-start guard - a second connect() for the same
  profile while a healthy attempt is in flight is ignored (four starters
  raced through here within 20 s after the 2.13.14 self-update)
- NetworkMonitor/AutoConnectManager: flap detection (>=2 kind changes in
  5 min stretches the auto-connect delay to 10 s; a Wi-Fi flap produced
  a 7-second-lived session and a wasted IKE handshake)
- hardcode diag TAGs obfuscated by R8 ("a: update: up to date" ->
  "UpdateManager: ..."), same for UpdateInstaller/VpnShortcutManager

src/frontends/android/app/build.gradle

@@ -37,8 +37,8 @@ android {
         minSdkVersion 21
         targetSdkVersion 36
 
-        versionCode 151
-        versionName "2.13.14"
+        versionCode 152
+        versionName "2.13.15"
 
         /* Base URL of the update storage, trailing slash included */
         buildConfigField "String", "UPDATE_BASE_URL", "\"${updateBaseUrl}\""

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

@@ -1450,6 +1450,21 @@ public class CharonVpnService extends VpnService implements Runnable, VpnStateSe
 		}
 	}
 
+	/**
+	 * Called via JNI when a direct destination's failure cooldown escalates
+	 * (the window grew) or crosses a failure milestone: surfaces the dead
+	 * hosts that apps keep hammering directly, with the current penalty.
+	 *
+	 * @param dst       preformatted "ip:port" of the destination
+	 * @param fails     failed connect cycles recorded for this destination
+	 * @param cooldownS current cooldown window in seconds
+	 */
+	public void logDeadDestination(String dst, int fails, int cooldownS)
+	{
+		DiagLog.i(TAG, "direct tcp: dst=" + dst + " dead: " + fails
+			+ " failed connects, cooldown " + cooldownS + "s");
+	}
+
 	/**
 	 * Initialization of charon, provided by libandroidbridge.so
 	 *

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

@@ -88,6 +88,11 @@ public class VpnStateService extends Service
 	private boolean mRetryFrozen;
 	/* timestamp of the last network-change-triggered immediate retry */
 	private long mLastNetworkRetry;
+	/* double-start guard: profile and issue time of the last connect() that
+	 * got through, cleared by disconnect() */
+	private static final long CONNECT_DEDUPE_MS = 10000;
+	private String mLastConnectUuid;
+	private long mLastConnectIssued;
 
 	private static final String TAG = VpnStateService.class.getSimpleName();
 
@@ -330,9 +335,12 @@ public class VpnStateService extends Service
 	 */
 	public void disconnect(boolean autoManaged)
 	{
-		/* reset any potential retry timer and error state */
+		/* reset any potential retry timer and error state, and re-arm the
+		 * double-start guard (a connect after a deliberate disconnect is a
+		 * fresh request and must not be deduped) */
 		resetRetryTimer();
 		setError(ErrorState.NO_ERROR);
+		mLastConnectIssued = 0;
 
 		if (autoManaged)
 		{	/* the auto-connect feature parked the tunnel on a trusted network;
@@ -400,6 +408,26 @@ public class VpnStateService extends Service
 			/* pass the previous password along */
 			profileInfo.putString(VpnProfileDataSource.KEY_PASSWORD, mProfile.getPassword());
 		}
+		String uuid = profileInfo.getString(VpnProfileDataSource.KEY_UUID);
+		if (uuid == null && mProfile != null)
+		{
+			uuid = mProfile.getUUID().toString();
+		}
+		/* double-start guard: while a healthy connect attempt for the same
+		 * profile is in flight (or was just issued and the service has not
+		 * reached startConnection() yet) a second start intent only churns
+		 * the daemon - after an app self-update up to four starters (update
+		 * receiver, process-start auto-connect, watchdog, UI) raced through
+		 * here within 20 seconds.  Deliberate retries during an error backoff
+		 * (mError set) and requests for another profile always pass. */
+		if (uuid != null && uuid.equals(mLastConnectUuid) && mError == ErrorState.NO_ERROR
+			&& (mState == State.CONNECTING
+				|| ((mState == State.DISABLED || mState == State.DISCONNECTING)
+					&& SystemClock.uptimeMillis() - mLastConnectIssued < CONNECT_DEDUPE_MS)))
+		{
+			DiagLog.i(TAG, "connect: same profile already connecting, ignored");
+			return;
+		}
 		if (fromScratch)
 		{
 			/* reset if this is a manual retry or a new connection */
@@ -432,13 +460,10 @@ public class VpnStateService extends Service
 		/* remember that a connection is expected so the watchdog can restore
 		 * it if this process dies (Always-on VPN is restarted by the system
 		 * and bypasses this path anyway) */
-		String uuid = profileInfo.getString(VpnProfileDataSource.KEY_UUID);
-		if (uuid == null && mProfile != null)
-		{
-			uuid = mProfile.getUUID().toString();
-		}
 		if (uuid != null)
 		{
+			mLastConnectUuid = uuid;
+			mLastConnectIssued = SystemClock.uptimeMillis();
 			SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
 			if (!uuid.equals(prefs.getString(Constants.PREF_WATCHDOG_EXPECTED_PROFILE, null)))
 			{

src/frontends/android/app/src/main/java/org/strongswan/android/logic/autoconnect/AutoConnectManager.kt

@@ -286,11 +286,13 @@ class AutoConnectManager private constructor(
 			return
 		}
 		/* Wi-Fi at the edge of range flaps with a ~10-15 s period: a park
-		 * followed by a quick "untrusted" flip must not bounce the tunnel
-		 * through full reconnects.  Right after a park require a longer
-		 * stable-cellular window before starting (the runnable re-evaluates
-		 * and quietly gives up if the trusted Wi-Fi returned in between). */
-		val delay = if (SystemClock.elapsedRealtime() - lastParkAt < RECENT_PARK_WINDOW_MS)
+		 * followed by a quick "untrusted" flip - or a network kind that keeps
+		 * bouncing - must not bounce the tunnel through full reconnects (one
+		 * such flap produced a 7-second-lived session and a wasted IKE
+		 * handshake).  Require a longer stable-untrusted window before
+		 * starting (the runnable re-evaluates and quietly gives up if a
+		 * trusted Wi-Fi returned in between). */
+		val delay = if (SystemClock.elapsedRealtime() - lastParkAt < RECENT_PARK_WINDOW_MS || monitor.isFlapping())
 		{
 			FLAP_CONNECT_DELAY_MS
 		}

src/frontends/android/app/src/main/java/org/strongswan/android/logic/autoconnect/NetworkMonitor.kt

@@ -23,6 +23,7 @@ import android.net.wifi.WifiInfo
 import android.os.Build
 import android.os.Handler
 import android.os.Looper
+import android.os.SystemClock
 import android.util.Log
 import org.strongswan.android.logic.DiagLog
 import java.util.concurrent.ConcurrentHashMap
@@ -51,6 +52,8 @@ class NetworkMonitor(
 	private var registered = false
 	private var lastReported: AutoConnectManager.NetworkKind? = null
 	private var ssidRetries = 0
+	/* rolling log of network-kind change times, for flap detection (main thread only) */
+	private val kindChangeTimes = ArrayDeque<Long>()
 
 	private val events = object
 	{
@@ -134,6 +137,7 @@ class NetworkMonitor(
 		ssids.clear()
 		lastReported = null
 		ssidRetries = 0
+		kindChangeTimes.clear()
 	}
 
 	fun forceEvaluate()
@@ -305,10 +309,42 @@ class NetworkMonitor(
 			Log.i(TAG, "Network kind $lastReported -> $kind")
 			DiagLog.i(TAG, "network kind $lastReported -> $kind")
 			lastReported = kind
+			recordKindChange(SystemClock.elapsedRealtime())
 			onNetworkChanged(kind)
 		}
 	}
 
+	/**
+	 * Remember a kind change for [isFlapping], dropping entries that fell out
+	 * of the flap window (plus a hard cap so a pathological callback storm
+	 * cannot grow the log unbounded).
+	 */
+	private fun recordKindChange(now: Long)
+	{
+		kindChangeTimes.addLast(now)
+		while (kindChangeTimes.size > KIND_CHANGE_LOG_MAX ||
+			(kindChangeTimes.isNotEmpty() && now - kindChangeTimes.first() > FLAP_WINDOW_MS))
+		{
+			kindChangeTimes.removeFirst()
+		}
+	}
+
+	/**
+	 * Whether the network kind is bouncing: at least [FLAP_MIN_CHANGES] kind
+	 * changes (including the latest one) within [FLAP_WINDOW_MS].  Callers
+	 * stretch out auto-connect delays while the underlying network settles
+	 * instead of bouncing the tunnel through short-lived sessions.
+	 */
+	fun isFlapping(): Boolean
+	{
+		val now = SystemClock.elapsedRealtime()
+		while (kindChangeTimes.isNotEmpty() && now - kindChangeTimes.first() > FLAP_WINDOW_MS)
+		{
+			kindChangeTimes.removeFirst()
+		}
+		return kindChangeTimes.size >= FLAP_MIN_CHANGES
+	}
+
 	private val evaluateRunnable = Runnable { evaluateNow() }
 
 	companion object
@@ -317,5 +353,8 @@ class NetworkMonitor(
 		private const val DEBOUNCE_MS = 1500L
 		private const val SSID_RETRY_MS = 400L
 		private const val SSID_RETRY_MAX = 8
+		private const val FLAP_WINDOW_MS = 5 * 60_000L
+		private const val FLAP_MIN_CHANGES = 2
+		private const val KIND_CHANGE_LOG_MAX = 16
 	}
 }

src/frontends/android/app/src/main/java/org/strongswan/android/logic/shortcuts/VpnShortcutManager.kt

@@ -45,7 +45,8 @@ class VpnShortcutManager private constructor(private val context: Context)
 {
 	companion object
 	{
-		private val TAG = VpnShortcutManager::class.java.simpleName
+		/* hardcoded: the runtime class name is obfuscated by R8 in release builds */
+		private const val TAG = "VpnShortcutManager"
 
 		/** slots always occupied by the connect/disconnect/toggle shortcuts */
 		private const val RESERVED_SLOTS = 3

src/frontends/android/app/src/main/java/org/strongswan/android/logic/updates/UpdateInstaller.kt

@@ -31,7 +31,8 @@ import java.io.File
  */
 object UpdateInstaller
 {
-	private val TAG = UpdateInstaller::class.java.simpleName
+	/* hardcoded: the runtime class name is obfuscated by R8 in release builds */
+	private const val TAG = "UpdateInstaller"
 
 	fun install(context: Context, apk: File)
 	{

src/frontends/android/app/src/main/java/org/strongswan/android/logic/updates/UpdateManager.kt

@@ -103,7 +103,9 @@ class UpdateManager private constructor(private val context: Context)
 {
 	companion object
 	{
-		private val TAG = UpdateManager::class.java.simpleName
+		/* hardcoded: the runtime class name is obfuscated by R8 in release
+		 * builds, which turned the diag tag into "a:" */
+		private const val TAG = "UpdateManager"
 
 		private const val UPDATE_DIR = "update"
 		private const val APK_NAME = "update.apk"

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

@@ -393,6 +393,40 @@ failed:
 	androidjni_detach_thread();
 }
 
+/**
+ * Tell Java a direct destination is dead and how long it is being refused
+ * for (diagnostics; the engine calls this when the cooldown window escalates
+ * or a failure milestone is crossed).  Best effort.
+ */
+void charonservice_log_dead_destination(const char *dst, uint32_t fails,
+										uint32_t cooldown_s)
+{
+	private_charonservice_t *this = (private_charonservice_t*)charonservice;
+	JNIEnv *env;
+	jmethodID method_id;
+	jstring jdst;
+
+	if (!this || !dst)
+	{
+		return;
+	}
+
+	androidjni_attach_thread(&env);
+	jdst = (*env)->NewStringUTF(env, dst);
+	method_id = (*env)->GetMethodID(env, android_charonvpnservice_class,
+									"logDeadDestination",
+									"(Ljava/lang/String;II)V");
+	if (!jdst || !method_id)
+	{
+		goto failed;
+	}
+	(*env)->CallVoidMethod(env, this->vpn_service, method_id,
+						   jdst, (jint)fails, (jint)cooldown_s);
+failed:
+	androidjni_exception_occurred(env);
+	androidjni_detach_thread();
+}
+
 /**
  * Converts the given Java array of byte arrays (byte[][]) to a linked list
  * of chunk_t objects.

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

@@ -190,4 +190,12 @@ void charonservice_log_connection_owner(const struct sockaddr *local,
 										const struct sockaddr *remote,
 										const char *dst);
 
+/**
+ * Log (via Java) a direct destination whose failure cooldown escalated (the
+ * window grew) or crossed a failure milestone: surfaces the dead hosts apps
+ * keep hammering.  Best effort.
+ */
+void charonservice_log_dead_destination(const char *dst, uint32_t fails,
+										uint32_t cooldown_s);
+
 #endif /** CHARONSERVICE_H_ @}*/

src/frontends/android/app/src/main/jni/libandroidbridge/routing/direct_tcp.c

@@ -67,15 +67,32 @@
 
 /**
  * Negative cache: after NEG_FAILS consecutive failed connect cycles a
- * destination is refused outright (RST without a socket) for
- * NEG_COOLDOWN_MS, so an app hammering a dead host cannot burn sockets,
- * JNI protect() roundtrips and log lines.  Cleared on success, on a network
- * change (reprotect) and after NEG_EXPIRY_MS without failures.
+ * destination is refused outright (RST without a socket), so an app
+ * hammering a dead host cannot burn sockets, JNI protect() roundtrips and
+ * log lines.  The refusal window starts at NEG_COOLDOWN_MS and doubles per
+ * further failed cycle up to NEG_COOLDOWN_MAX_MS - a chronically dead host
+ * then costs one probe per window instead of a constant 45 s cadence (one
+ * app was observed opening ~3000 connects/hour to each of two dead hosts,
+ * waking the radio for every leaked probe).  Cleared on success, on a
+ * network change (reprotect) and after NEG_EXPIRY_MS without failures.
  */
 #define NEG_FAILS			3
 #define NEG_COOLDOWN_MS		45000
+#define NEG_COOLDOWN_MAX_MS	(5 * 60 * 1000)
 #define NEG_EXPIRY_MS		(10 * 60 * 1000)
 
+/**
+ * Report the dead destination at every NEG_REPORT_FAILS-th failure even
+ * after the window has maxed out, so long-running outages stay visible
+ */
+#define NEG_REPORT_FAILS	100
+
+/**
+ * neg_record_fail() flags
+ */
+#define NEG_ARMED			(1<<0)	/* cooldown (re)armed right now */
+#define NEG_ESCALATED		(1<<1)	/* window grew or milestone crossed */
+
 /**
  * Minimum spacing between failure log lines for the same destination
  */
@@ -92,6 +109,7 @@ typedef struct {
 	bool used;
 	struct sockaddr_storage dest;
 	uint32_t fails;
+	uint32_t cooldown_ms;
 	uint64_t last_fail, cooldown_until, last_log;
 } neg_entry_t;
 
@@ -411,11 +429,14 @@ static bool neg_should_log(private_direct_tcp_t *this, const struct sockaddr_sto
 }
 
 /**
- * Record a failed connect cycle.  Returns TRUE when the destination just
- * entered its cooldown (the caller may log/attribute the owner once here).
+ * Record a failed connect cycle.  Returns NEG_ARMED when the destination
+ * (re)entered its cooldown right now (the caller may log/attribute the owner
+ * once here), plus NEG_ESCALATED when the window grew or a failure milestone
+ * was crossed (worth a dead-destination diag line).  fails/window report the
+ * armed state for that line and may be NULL.
  */
-static bool neg_record_fail(private_direct_tcp_t *this, const struct sockaddr_storage *ss,
-							uint64_t now)
+static int neg_record_fail(private_direct_tcp_t *this, const struct sockaddr_storage *ss,
+						   uint64_t now, uint32_t *fails, uint32_t *window)
 {
 	neg_entry_t *entry = NULL, *oldest = &this->neg[0];
 	size_t i;
@@ -452,15 +473,32 @@ static bool neg_record_fail(private_direct_tcp_t *this, const struct sockaddr_st
 	else if (now - entry->last_fail > NEG_EXPIRY_MS)
 	{	/* silence long enough: start over */
 		entry->fails = 0;
+		entry->cooldown_ms = 0;
 	}
 	entry->fails++;
 	entry->last_fail = now;
 	if (entry->fails >= NEG_FAILS && now >= entry->cooldown_until)
 	{
-		entry->cooldown_until = now + NEG_COOLDOWN_MS;
-		return TRUE;
+		uint32_t prev = entry->cooldown_ms;
+
+		entry->cooldown_ms = entry->cooldown_ms ?
+			min(entry->cooldown_ms * 2, NEG_COOLDOWN_MAX_MS) : NEG_COOLDOWN_MS;
+		entry->cooldown_until = now + entry->cooldown_ms;
+		if (fails)
+		{
+			*fails = entry->fails;
+		}
+		if (window)
+		{
+			*window = entry->cooldown_ms;
+		}
+		if (entry->cooldown_ms > prev || entry->fails % NEG_REPORT_FAILS == 0)
+		{
+			return NEG_ARMED | NEG_ESCALATED;
+		}
+		return NEG_ARMED;
 	}
-	return FALSE;
+	return 0;
 }
 
 /**
@@ -581,7 +619,7 @@ static lwip_err_t on_accept(void *arg, struct tcp_pcb *newpcb, lwip_err_t err)
 	if (fd < 0)
 	{
 		DIRECT_STATS_ADD(this->stats->relay_errors, 1);
-		if (neg_record_fail(this, &ss, now))
+		if (neg_record_fail(this, &ss, now, NULL, NULL) & NEG_ARMED)
 		{
 			charonservice_log_connection_owner((struct sockaddr*)&org,
 											   (struct sockaddr*)&ss, dest);
@@ -955,13 +993,20 @@ METHOD(direct_tcp_t, process_poll, void,
 				}
 				else
 				{
+					uint32_t fails = 0, window = 0;
+					int flags;
+
 					format_dest(&relay->dest, dest, sizeof(dest));
 					do_log = neg_should_log(this, &relay->dest, now);
-					if (!relay->retried)
+					if (!relay->retried && err != ECONNREFUSED)
 					{	/* one retry on a fresh socket: the first attempt may have
 						 * been pinned to a network that vanished mid-roam (its
 						 * EHOSTUNREACH can take over a minute to surface, leaving
-						 * the connection hanging) */
+						 * the connection hanging).  Skipped for ECONNREFUSED -
+						 * the peer actively refused on the network this socket is
+						 * bound to, so a second socket there hits the same
+						 * refusal, and a mid-roam socket is already aborted by
+						 * reprotect() before its error can surface here. */
 						int nfd;
 
 						if (do_log)
@@ -981,7 +1026,8 @@ METHOD(direct_tcp_t, process_poll, void,
 						err = errno;
 					}
 					DIRECT_STATS_ADD(this->stats->relay_errors, 1);
-					if (neg_record_fail(this, &relay->dest, now))
+					flags = neg_record_fail(this, &relay->dest, now, &fails, &window);
+					if (flags & NEG_ARMED)
 					{	/* destination just entered its cooldown: name the app
 						 * that owns the connection while its socket still
 						 * exists (relay_destroy aborts the pcb below) */
@@ -989,6 +1035,12 @@ METHOD(direct_tcp_t, process_poll, void,
 							(struct sockaddr*)&relay->origin,
 							(struct sockaddr*)&relay->dest, dest);
 					}
+					if (flags & NEG_ESCALATED)
+					{	/* the cooldown window just grew (or a milestone was
+						 * crossed): make the dead host visible in diag.log */
+						charonservice_log_dead_destination(dest, fails,
+														   (window + 999) / 1000);
+					}
 					if (do_log)
 					{
 						DBG1(DBG_NET, "direct tcp: connect failed dst=%s: %s",