- Make connectionQueue(), latestTransmissionOutcomes() and latestTransmissionSuccessful() methods static in order to match the underlying data storage.

- Make it possible to transfer elements directly between connectionQueues.

- Add defaultBSSID value.

- Fix bug where encrypted Espnow-connections expired 1 ms too late.

- Add MutexTracker::captureBan() functionality and use it in the espnowReceiveCallbackWrapper method to ensure a consistent mutex environment there.

- Rename acceptRequest to acceptRequests since several requests can be accepted, not just one.

- Reorganize EspnowMeshBackend.cpp.

- Split sendEspnowResponses() method into sendEspnowResponses() and sendPeerRequestConfirmations().

- Add sendStoredEspnowMessages() method to provide the same functionality as the previous version of sendEspnowResponses().

- Add logic for handling peerRequestConfirmations received at the same time as a peer request is being made, to avoid lockups when there are simultaneous cyclic peer requests.

- Add logic for handling simultaneous reciprocal peer requests.

- Include MAC addresses in HMAC calculations for peer requests and use HMAC for all unencrypted peer request messages, to make sure we receive valid MAC combinations.

- Add asserts to ensure ESP-NOW encryption integrity during code changes.

- Add estimatedMaxDuration argument to performEspnowMaintainance and related methods.

- Add methods to EncryptedConnectionData for setting peer MAC.

- Remove createEncryptionRequestMessage function from JsonTranslator since it is not used, to increase clarity.

- Add encryptedConnectionsSoftLimit() and related functionality.

- Add mutex to protect connectionQueue usage during attemptTransmission.

- Add _ongoingPeerRequestMac variable.

- Add reservedEncryptedConnections() method.

- Add TransmissionOutcomesUpdateHook() callback.

- Add constConnectionQueue() method to allow connectionQueue usage while connectionQueue mutex is active.

- Rearrange attemptAutoEncryptingTransmission argument order to increase efficiency.

- Add functionality for serializing the unencrypted ESP-NOW connection.

- Add some constness.

- Improve comments.

- Improve documentation.

- Update keywords.txt.

libraries/ESP8266WiFiMesh/src/TcpIpMeshBackend.cpp

@@ -30,6 +30,7 @@
 const IPAddress TcpIpMeshBackend::emptyIP = IPAddress();
 
 bool TcpIpMeshBackend::_tcpIpTransmissionMutex = false;
+bool TcpIpMeshBackend::_tcpIpConnectionQueueMutex = false;
 
 String TcpIpMeshBackend::lastSSID = "";
 bool TcpIpMeshBackend::staticIPActivated = false;
@@ -58,6 +59,17 @@ TcpIpMeshBackend::TcpIpMeshBackend(requestHandlerType requestHandler, responseHa
 
 std::vector<TcpIpNetworkInfo> & TcpIpMeshBackend::connectionQueue()
 {
+  MutexTracker connectionQueueMutexTracker(_tcpIpConnectionQueueMutex);
+  if(!connectionQueueMutexTracker.mutexCaptured())
+  {
+    assert(false && "ERROR! connectionQueue locked. Don't call connectionQueue() from callbacks other than NetworkFilter as this may corrupt program state!"); 
+  }
+  
+  return _connectionQueue;
+}
+
+const std::vector<TcpIpNetworkInfo> & TcpIpMeshBackend::constConnectionQueue()
+{  
   return _connectionQueue;
 }
 
@@ -66,6 +78,11 @@ std::vector<TransmissionOutcome> & TcpIpMeshBackend::latestTransmissionOutcomes(
   return _latestTransmissionOutcomes;
 }
 
+bool TcpIpMeshBackend::latestTransmissionSuccessful()
+{
+  return latestTransmissionSuccessfulBase(latestTransmissionOutcomes());
+}
+
 void TcpIpMeshBackend::begin()
 {
   if(!TcpIpMeshBackend::getAPController()) // If there is no active AP controller
@@ -433,7 +450,7 @@ void TcpIpMeshBackend::attemptTransmission(const String &message, bool scan, boo
   if(WiFi.status() == WL_CONNECTED)
   {
     transmission_status_t transmissionResult = attemptDataTransfer();
-    latestTransmissionOutcomes().push_back(TransmissionOutcome(connectionQueue().back(), transmissionResult));
+    latestTransmissionOutcomes().push_back(TransmissionOutcome(constConnectionQueue().back(), transmissionResult));
   }
   else
   {
@@ -443,11 +460,22 @@ void TcpIpMeshBackend::attemptTransmission(const String &message, bool scan, boo
       scanForNetworks(scanAllWiFiChannels);
     }
 
-    for(TcpIpNetworkInfo &currentNetwork : connectionQueue())
+    MutexTracker connectionQueueMutexTracker(_tcpIpConnectionQueueMutex);
+    if(!connectionQueueMutexTracker.mutexCaptured())
     {
-      transmission_status_t transmissionResult = initiateTransmission(currentNetwork);
-            
-      latestTransmissionOutcomes().push_back(TransmissionOutcome{.origin = currentNetwork, .transmissionStatus = transmissionResult});
+      assert(false && "ERROR! connectionQueue locked. Don't call attemptTransmission from callbacks as this may corrupt program state! Aborting."); 
+    }
+    else
+    {
+      for(const TcpIpNetworkInfo &currentNetwork : constConnectionQueue())
+      {
+        transmission_status_t transmissionResult = initiateTransmission(currentNetwork);
+              
+        latestTransmissionOutcomes().push_back(TransmissionOutcome{.origin = currentNetwork, .transmissionStatus = transmissionResult});
+
+        if(!getTransmissionOutcomesUpdateHook()(*this))
+          break;
+      }
     }
   }
   
@@ -492,12 +520,12 @@ transmission_status_t TcpIpMeshBackend::attemptTransmission(const String &messag
   return transmissionResult;
 }
 
-void TcpIpMeshBackend::acceptRequest()
+void TcpIpMeshBackend::acceptRequests()
 {
   MutexTracker mutexTracker(_tcpIpTransmissionMutex);
   if(!mutexTracker.mutexCaptured())
   {
-    assert(false && "ERROR! TCP/IP transmission in progress. Don't call acceptRequest from TCP/IP callbacks as this may corrupt program state! Aborting."); 
+    assert(false && "ERROR! TCP/IP transmission in progress. Don't call acceptRequests from callbacks as this may corrupt program state! Aborting."); 
     return;
   }