Allow disabling of packet fragmentation (#1709)

* Add compatibility option for AWS

* Fix UWP build

* Fix comment in MqttClientOptions (#1706)

* Refactor naming

* Fix wrong option value

---------

Co-authored-by: Michi <michael@volz.dev>

Source/MQTTnet/Adapter/MqttChannelAdapter.cs

@@ -27,18 +27,15 @@ namespace MQTTnet.Adapter
         readonly byte[] _fixedHeaderBuffer = new byte[2];
         readonly MqttNetSourceLogger _logger;
 
-        readonly MqttPacketInspector _packetInspector;
-
         readonly byte[] _singleByteBuffer = new byte[1];
 
         readonly AsyncLock _syncRoot = new AsyncLock();
 
-        Statistics _statistics;     // mutable struct, don't make readonly!
+        Statistics _statistics; // mutable struct, don't make readonly!
 
-        public MqttChannelAdapter(IMqttChannel channel, MqttPacketFormatterAdapter packetFormatterAdapter, MqttPacketInspector packetInspector, IMqttNetLogger logger)
+        public MqttChannelAdapter(IMqttChannel channel, MqttPacketFormatterAdapter packetFormatterAdapter, IMqttNetLogger logger)
         {
             _channel = channel ?? throw new ArgumentNullException(nameof(channel));
-            _packetInspector = packetInspector;
 
             PacketFormatterAdapter = packetFormatterAdapter ?? throw new ArgumentNullException(nameof(packetFormatterAdapter));
 
@@ -64,6 +61,10 @@ namespace MQTTnet.Adapter
 
         public MqttPacketFormatterAdapter PacketFormatterAdapter { get; }
 
+        public MqttPacketInspector PacketInspector { get; set; }
+
+        public bool AllowPacketFragmentation { get; set; } = true;
+
         public async Task ConnectAsync(CancellationToken cancellationToken)
         {
             cancellationToken.ThrowIfCancellationRequested();
@@ -126,7 +127,7 @@ namespace MQTTnet.Adapter
 
             try
             {
-                _packetInspector?.BeginReceivePacket();
+                PacketInspector?.BeginReceivePacket();
 
                 ReceivedMqttPacket receivedPacket;
                 var receivedPacketTask = ReceiveAsync(cancellationToken);
@@ -144,7 +145,7 @@ namespace MQTTnet.Adapter
                     return null;
                 }
 
-                _packetInspector?.EndReceivePacket();
+                PacketInspector?.EndReceivePacket();
 
                 Interlocked.Add(ref _statistics._bytesSent, receivedPacket.TotalLength);
 
@@ -180,7 +181,10 @@ namespace MQTTnet.Adapter
             return null;
         }
 
-        public void ResetStatistics() => _statistics.Reset();
+        public void ResetStatistics()
+        {
+            _statistics.Reset();
+        }
 
         public async Task SendPacketAsync(MqttPacket packet, CancellationToken cancellationToken)
         {
@@ -197,18 +201,18 @@ namespace MQTTnet.Adapter
                 try
                 {
                     var packetBuffer = PacketFormatterAdapter.Encode(packet);
-                    _packetInspector?.BeginSendPacket(packetBuffer);
+                    PacketInspector?.BeginSendPacket(packetBuffer);
 
                     _logger.Verbose("TX ({0} bytes) >>> {1}", packetBuffer.Length, packet);
-
-                    if (packetBuffer.Payload.Count > 0)
+                    
+                    if (packetBuffer.Payload.Count == 0 || !AllowPacketFragmentation)
                     {
-                        await _channel.WriteAsync(packetBuffer.Packet, false, cancellationToken).ConfigureAwait(false);
-                        await _channel.WriteAsync(packetBuffer.Payload, true, cancellationToken).ConfigureAwait(false);
+                        await _channel.WriteAsync(packetBuffer.Join(), true, cancellationToken).ConfigureAwait(false);
                     }
                     else
                     {
-                        await _channel.WriteAsync(packetBuffer.Packet, true, cancellationToken).ConfigureAwait(false);
+                        await _channel.WriteAsync(packetBuffer.Packet, false, cancellationToken).ConfigureAwait(false);
+                        await _channel.WriteAsync(packetBuffer.Payload, true, cancellationToken).ConfigureAwait(false);
                     }
 
                     Interlocked.Add(ref _statistics._bytesReceived, packetBuffer.Length);
@@ -270,7 +274,7 @@ namespace MQTTnet.Adapter
                     return 0;
                 }
 
-                _packetInspector?.FillReceiveBuffer(_singleByteBuffer);
+                PacketInspector?.FillReceiveBuffer(_singleByteBuffer);
 
                 encodedByte = _singleByteBuffer[0];
 
@@ -309,7 +313,7 @@ namespace MQTTnet.Adapter
                 {
                     return ReadFixedHeaderResult.ConnectionClosed;
                 }
-               
+
                 if (cancellationToken.IsCancellationRequested)
                 {
                     return ReadFixedHeaderResult.Canceled;
@@ -323,7 +327,7 @@ namespace MQTTnet.Adapter
                 totalBytesRead += bytesRead;
             }
 
-            _packetInspector?.FillReceiveBuffer(buffer);
+            PacketInspector?.FillReceiveBuffer(buffer);
 
             var hasRemainingLength = buffer[1] != 0;
             if (!hasRemainingLength)
@@ -407,7 +411,7 @@ namespace MQTTnet.Adapter
                     bodyOffset += readBytes;
                 } while (bodyOffset < bodyLength);
 
-                _packetInspector?.FillReceiveBuffer(body);
+                PacketInspector?.FillReceiveBuffer(body);
 
                 var bodySegment = new ArraySegment<byte>(body, 0, bodyLength);
                 return new ReceivedMqttPacket(fixedHeader.Flags, bodySegment, fixedHeader.TotalLength);
@@ -455,7 +459,7 @@ namespace MQTTnet.Adapter
             throw new MqttCommunicationException(exception);
         }
 
-        private struct Statistics
+        struct Statistics
         {
             public long _bytesReceived;
             public long _bytesSent;

Source/MQTTnet/Client/Options/MqttClientOptions.cs

@@ -24,6 +24,14 @@ namespace MQTTnet.Client
         /// </summary>
         public string AuthenticationMethod { get; set; }
 
+        /// <summary>
+        ///     Usually the MQTT packets can be send partially. This is done by using multiple TCP packets
+        ///     or WebSocket frames etc. Unfortunately not all brokers (like Amazon Web Services (AWS)) do support this feature and
+        ///     will close the connection when receiving such packets. If such a service is used this flag must
+        ///     be set to _false_.
+        /// </summary>
+        public bool AllowPacketFragmentation { get; set; } = true;
+
         public IMqttClientChannelOptions ChannelOptions { get; set; }
 
         /// <summary>
@@ -214,4 +222,4 @@ namespace MQTTnet.Client
         /// </summary>
         public int WriterBufferSizeMax { get; set; } = 65535;
     }
-}
+}

Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs

@@ -75,10 +75,22 @@ namespace MQTTnet.Client
             _options.ChannelOptions = (IMqttClientChannelOptions)_tcpOptions ?? _webSocketOptions;
 
             MqttClientOptionsValidator.ThrowIfNotSupported(_options);
-            
+
             return _options;
         }
 
+        /// <summary>
+        ///     Usually the MQTT packets can be send partially. This is done by using multiple TCP packets
+        ///     or WebSocket frames etc. Unfortunately not all brokers (like Amazon Web Services (AWS)) do support this feature and
+        ///     will close the connection when receiving such packets. If such a service is used this flag must
+        ///     be set to _true_.
+        /// </summary>
+        public MqttClientOptionsBuilder WithoutPacketFragmentation()
+        {
+            _options.AllowPacketFragmentation = false;
+            return this;
+        }
+
         public MqttClientOptionsBuilder WithAuthentication(string method, byte[] data)
         {
             _options.AuthenticationMethod = method;
@@ -266,7 +278,7 @@ namespace MQTTnet.Client
 
             return this;
         }
-        
+
         public MqttClientOptionsBuilder WithTcpServer(Action<MqttClientTcpOptions> optionsBuilder)
         {
             if (optionsBuilder == null)
@@ -373,6 +385,18 @@ namespace MQTTnet.Client
             return this;
         }
 
+        public MqttClientOptionsBuilder WithWillContentType(string willContentType)
+        {
+            _options.WillContentType = willContentType;
+            return this;
+        }
+
+        public MqttClientOptionsBuilder WithWillCorrelationData(byte[] willCorrelationData)
+        {
+            _options.WillCorrelationData = willCorrelationData;
+            return this;
+        }
+
         public MqttClientOptionsBuilder WithWillDelayInterval(uint willDelayInterval)
         {
             _options.WillDelayInterval = willDelayInterval;
@@ -384,27 +408,33 @@ namespace MQTTnet.Client
             _options.WillPayload = willPayload;
             return this;
         }
-        
+
         public MqttClientOptionsBuilder WithWillPayload(string willPayload)
         {
             if (string.IsNullOrEmpty(willPayload))
             {
                 return WithWillPayload((byte[])null);
             }
-            
+
             _options.WillPayload = Encoding.UTF8.GetBytes(willPayload);
             return this;
         }
 
+        public MqttClientOptionsBuilder WithWillPayloadFormatIndicator(MqttPayloadFormatIndicator willPayloadFormatIndicator)
+        {
+            _options.WillPayloadFormatIndicator = willPayloadFormatIndicator;
+            return this;
+        }
+
         public MqttClientOptionsBuilder WithWillQualityOfServiceLevel(MqttQualityOfServiceLevel willQualityOfServiceLevel)
         {
             _options.WillQualityOfServiceLevel = willQualityOfServiceLevel;
             return this;
         }
 
-        public MqttClientOptionsBuilder WithWillTopic(string willTopic)
+        public MqttClientOptionsBuilder WithWillResponseTopic(string willResponseTopic)
         {
-            _options.WillTopic = willTopic;
+            _options.WillResponseTopic = willResponseTopic;
             return this;
         }
 
@@ -413,38 +443,20 @@ namespace MQTTnet.Client
             _options.WillRetain = willRetain;
             return this;
         }
-        
-        public MqttClientOptionsBuilder WithWillContentType(string willContentType)
+
+        public MqttClientOptionsBuilder WithWillTopic(string willTopic)
         {
-            _options.WillContentType = willContentType;
+            _options.WillTopic = willTopic;
             return this;
         }
-        
-        public MqttClientOptionsBuilder WithWillCorrelationData(byte[] willCorrelationData)
-        {
-            _options.WillCorrelationData = willCorrelationData;
-            return this;
-        }
-        
-        public MqttClientOptionsBuilder WithWillResponseTopic(string willResponseTopic)
-        {
-            _options.WillResponseTopic = willResponseTopic;
-            return this;
-        }
-        
-        public MqttClientOptionsBuilder WithWillPayloadFormatIndicator(MqttPayloadFormatIndicator willPayloadFormatIndicator)
-        {
-            _options.WillPayloadFormatIndicator = willPayloadFormatIndicator;
-            return this;
-        }
-        
+
         public MqttClientOptionsBuilder WithWillUserProperty(string name, string value)
         {
             if (_options.WillUserProperties == null)
             {
                 _options.WillUserProperties = new List<MqttUserProperty>();
             }
-            
+
             _options.WillUserProperties.Add(new MqttUserProperty(name, value));
             return this;
         }

Source/MQTTnet/Implementations/MqttClientAdapterFactory.cs

@@ -40,7 +40,12 @@ namespace MQTTnet.Implementations
 
             var bufferWriter = new MqttBufferWriter(options.WriterBufferSize, options.WriterBufferSizeMax);
             var packetFormatterAdapter = new MqttPacketFormatterAdapter(options.ProtocolVersion, bufferWriter);
-            return new MqttChannelAdapter(channel, packetFormatterAdapter, packetInspector, logger);
+
+            return new MqttChannelAdapter(channel, packetFormatterAdapter, logger)
+            {
+                AllowPacketFragmentation = options.AllowPacketFragmentation,
+                PacketInspector = packetInspector
+            };
         }
     }
 }

Source/MQTTnet/Implementations/MqttTcpServerAdapter.Uwp.cs

@@ -95,7 +95,7 @@ namespace MQTTnet.Implementations
                     var packetFormatterAdapter = new MqttPacketFormatterAdapter(bufferWriter);
                     var tcpChannel = new MqttTcpChannel(args.Socket, clientCertificate, _options);
 
-                    using (var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, null, _rootLogger))
+                    using (var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, _rootLogger))
                     {
                         await clientHandler(clientAdapter).ConfigureAwait(false);
                     }

Source/MQTTnet/Implementations/MqttTcpServerListener.cs

@@ -229,7 +229,7 @@ namespace MQTTnet.Implementations
                     var bufferWriter = new MqttBufferWriter(_serverOptions.WriterBufferSize, _serverOptions.WriterBufferSizeMax);
                     var packetFormatterAdapter = new MqttPacketFormatterAdapter(bufferWriter);
                     
-                    using (var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, null, _rootLogger))
+                    using (var clientAdapter = new MqttChannelAdapter(tcpChannel, packetFormatterAdapter, _rootLogger))
                     {
                         await clientHandler(clientAdapter).ConfigureAwait(false);
                     }