drop duplicate announces based on TTL (#558)

app/src/main/java/com/bitchat/android/mesh/SecurityManager.kt

@@ -56,18 +56,24 @@ class SecurityManager(private val encryptionService: EncryptionService, private
 
         // Duplicate detection
         val messageID = generateMessageID(packet, peerID)
-        if (messageType != MessageType.ANNOUNCE) {
+        
-            if (processedMessages.contains(messageID)) {
+        if (processedMessages.contains(messageID)) {
+            // Check for ANNOUNCE exception: allow if it looks like a direct neighbor (max TTL)
+            // This ensures we catch the "first announce" on a new connection for binding,
+            // while still dropping looped/relayed duplicates.
+            val isFreshAnnounce = messageType == MessageType.ANNOUNCE &&
+                    packet.ttl >= com.bitchat.android.util.AppConstants.MESSAGE_TTL_HOPS
+
+            if (!isFreshAnnounce) {
                 Log.d(TAG, "Dropping duplicate packet: $messageID")
                 return false
             }
-            // Add to processed messages
+            Log.d(TAG, "Allowing duplicate ANNOUNCE from direct neighbor: $messageID")
-            processedMessages.add(messageID)
-            messageTimestamps[messageID] = currentTime
-        } else {
-            // Do not deduplicate ANNOUNCE at the security layer.
-            // They are signed/idempotent and we need to ensure first-announce per-connection can bind.
         }
+
+        // Add to processed messages
+        processedMessages.add(messageID)
+        messageTimestamps[messageID] = currentTime
         
         // Enforce mandatory signature verification
         if (!verifyPacketSignature(packet, peerID)) {

app/src/test/kotlin/com/bitchat/android/mesh/SecurityManagerTest.kt

@@ -239,6 +239,37 @@ class SecurityManagerTest {
         assertFalse("Duplicate packet should be rejected", result2)
     }
 
+    @Test
+    fun `validatePacket - handles ANNOUNCE duplicates correctly`() {
+        val announcement = IdentityAnnouncement(
+            nickname = "New User",
+            noisePublicKey = otherNoiseKey,
+            signingPublicKey = otherSigningKey
+        )
+        val payload = announcement.encode()!!
+        
+        // 1. Initial Announce (Fresh)
+        val packet1 = BitchatPacket(
+            type = MessageType.ANNOUNCE.value,
+            ttl = com.bitchat.android.util.AppConstants.MESSAGE_TTL_HOPS, // 7u
+            senderID = unknownPeerID,
+            payload = payload
+        )
+        packet1.signature = validSignature
+        
+        whenever(mockDelegate.getPeerInfo(unknownPeerID)).thenReturn(null)
+
+        assertTrue("First ANNOUNCE should be accepted", securityManager.validatePacket(packet1, unknownPeerID))
+        
+        // 2. Relayed Duplicate (Lower TTL)
+        val packet2 = packet1.copy(ttl = (com.bitchat.android.util.AppConstants.MESSAGE_TTL_HOPS - 1u).toUByte())
+        assertFalse("Relayed duplicate ANNOUNCE should be rejected", securityManager.validatePacket(packet2, unknownPeerID))
+        
+        // 3. Direct Duplicate (Max TTL)
+        val packet3 = packet1.copy(ttl = com.bitchat.android.util.AppConstants.MESSAGE_TTL_HOPS)
+        assertTrue("Fresh duplicate ANNOUNCE should be accepted", securityManager.validatePacket(packet3, unknownPeerID))
+    }
+
     private fun setupKnownPeer(peerID: String, signingKey: ByteArray) {
         val info = PeerInfo(
             id = peerID,