Add interceptor for client subscriptions

MQTTnet.Core/Client/MqttClient.cs

@@ -149,36 +149,36 @@ namespace MQTTnet.Core.Client
                 switch (qosGroup.Key)
                 {
                     case MqttQualityOfServiceLevel.AtMostOnce:
-                        {
-                            // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
-                            await _adapter.SendPacketsAsync(_options.CommunicationTimeout, _cancellationTokenSource.Token, qosPackets);
-                            break;
-                        }
+                    {
+                        // No packet identifier is used for QoS 0 [3.3.2.2 Packet Identifier]
+                        await _adapter.SendPacketsAsync(_options.CommunicationTimeout, _cancellationTokenSource.Token, qosPackets);
+                        break;
+                    }
                     case MqttQualityOfServiceLevel.AtLeastOnce:
+                    {
+                        foreach (var publishPacket in qosPackets)
                         {
-                            foreach (var publishPacket in qosPackets)
-                            {
-                                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                                await SendAndReceiveAsync<MqttPubAckPacket>(publishPacket);
-                            }
-
-                            break;
+                            publishPacket.PacketIdentifier = GetNewPacketIdentifier();
+                            await SendAndReceiveAsync<MqttPubAckPacket>(publishPacket);
                         }
+
+                        break;
+                    }
                     case MqttQualityOfServiceLevel.ExactlyOnce:
+                    {
+                        foreach (var publishPacket in qosPackets)
                         {
-                            foreach (var publishPacket in qosPackets)
-                            {
-                                publishPacket.PacketIdentifier = GetNewPacketIdentifier();
-                                var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket).ConfigureAwait(false);
-                                await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>()).ConfigureAwait(false);
-                            }
+                            publishPacket.PacketIdentifier = GetNewPacketIdentifier();
+                            var pubRecPacket = await SendAndReceiveAsync<MqttPubRecPacket>(publishPacket).ConfigureAwait(false);
+                            await SendAndReceiveAsync<MqttPubCompPacket>(pubRecPacket.CreateResponse<MqttPubRelPacket>()).ConfigureAwait(false);
+                        }
 
-                            break;
-                        }
+                        break;
+                    }
                     default:
-                        {
-                            throw new InvalidOperationException();
-                        }
+                    {
+                        throw new InvalidOperationException();
+                    }
                 }
             }
         }
@@ -191,7 +191,7 @@ namespace MQTTnet.Core.Client
                 Username = _options.Credentials?.Username,
                 Password = _options.Credentials?.Password,
                 CleanSession = _options.CleanSession,
-                KeepAlivePeriod = (ushort)_options.KeepAlivePeriod.TotalSeconds,
+                KeepAlivePeriod = (ushort) _options.KeepAlivePeriod.TotalSeconds,
                 WillMessage = willApplicationMessage
             };
 
@@ -324,7 +324,7 @@ namespace MQTTnet.Core.Client
             if (publishPacket.QualityOfServiceLevel == MqttQualityOfServiceLevel.AtLeastOnce)
             {
                 FireApplicationMessageReceivedEvent(publishPacket);
-                await SendAsync(new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                await SendAsync(new MqttPubAckPacket {PacketIdentifier = publishPacket.PacketIdentifier});
                 return;
             }
 
@@ -337,7 +337,7 @@ namespace MQTTnet.Core.Client
                 }
 
                 FireApplicationMessageReceivedEvent(publishPacket);
-                await SendAsync(new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
+                await SendAsync(new MqttPubRecPacket {PacketIdentifier = publishPacket.PacketIdentifier});
                 return;
             }
 
@@ -363,12 +363,12 @@ namespace MQTTnet.Core.Client
         {
             var packetAwaiter = _packetDispatcher.WaitForPacketAsync(requestPacket, typeof(TResponsePacket), _options.CommunicationTimeout);
             await _adapter.SendPacketsAsync(_options.CommunicationTimeout, _cancellationTokenSource.Token, requestPacket).ConfigureAwait(false);
-            return (TResponsePacket)await packetAwaiter.ConfigureAwait(false);
+            return (TResponsePacket) await packetAwaiter.ConfigureAwait(false);
         }
 
         private ushort GetNewPacketIdentifier()
         {
-            return (ushort)Interlocked.Increment(ref _latestPacketIdentifier);
+            return (ushort) Interlocked.Increment(ref _latestPacketIdentifier);
         }
 
         private async Task SendKeepAliveMessagesAsync(CancellationToken cancellationToken)
@@ -465,7 +465,8 @@ namespace MQTTnet.Core.Client
         private void StartSendKeepAliveMessages(CancellationToken cancellationToken)
         {
 #pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
-            Task.Factory.StartNew(() => SendKeepAliveMessagesAsync(cancellationToken), cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Default).ConfigureAwait(false);
+            Task.Factory.StartNew(() => SendKeepAliveMessagesAsync(cancellationToken), cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Default)
+                .ConfigureAwait(false);
 #pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
         }
     }

MQTTnet.Core/Server/MqttApplicationMessageInterceptorContext.cs

@@ -0,0 +1,7 @@
+namespace MQTTnet.Core.Server
+{
+    public class MqttApplicationMessageInterceptorContext
+    {
+        public MqttApplicationMessage ApplicationMessage { get; set; }
+    }
+}

MQTTnet.Core/Server/MqttClientSession.cs

@@ -124,7 +124,7 @@ namespace MQTTnet.Core.Server
                 while (!cancellationToken.IsCancellationRequested)
                 {
                     var packet = await adapter.ReceivePacketAsync(TimeSpan.Zero, cancellationToken).ConfigureAwait(false);
-                    await ProcessReceivedPacketAsync(adapter, packet).ConfigureAwait(false);
+                    await ProcessReceivedPacketAsync(adapter, packet, cancellationToken).ConfigureAwait(false);
                 }
             }
             catch (OperationCanceledException)
@@ -142,28 +142,35 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        private async Task ProcessReceivedPacketAsync(IMqttCommunicationAdapter adapter, MqttBasePacket packet)
+        private async Task ProcessReceivedPacketAsync(IMqttCommunicationAdapter adapter, MqttBasePacket packet, CancellationToken cancellationToken)
         {
             if (packet is MqttSubscribePacket subscribePacket)
             {
-                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, _subscriptionsManager.Subscribe(subscribePacket));
+                var subscribeResult = _subscriptionsManager.Subscribe(subscribePacket);
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, subscribeResult.ResponsePacket);
                 EnqueueRetainedMessages(subscribePacket);
+
+                if (subscribeResult.CloseConnection)
+                {
+                    await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, new MqttDisconnectPacket());
+                    Stop();
+                }
             }
             else if (packet is MqttUnsubscribePacket unsubscribePacket)
             {
-                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, _subscriptionsManager.Unsubscribe(unsubscribePacket));
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, _subscriptionsManager.Unsubscribe(unsubscribePacket));
             }
             else if (packet is MqttPublishPacket publishPacket)
             {
-                await HandleIncomingPublishPacketAsync(adapter, publishPacket);
+                await HandleIncomingPublishPacketAsync(adapter, publishPacket, cancellationToken);
             }
             else if (packet is MqttPubRelPacket pubRelPacket)
             {
-                await HandleIncomingPubRelPacketAsync(adapter, pubRelPacket);
+                await HandleIncomingPubRelPacketAsync(adapter, pubRelPacket, cancellationToken);
             }
             else if (packet is MqttPubRecPacket pubRecPacket)
             {
-                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, pubRecPacket.CreateResponse<MqttPubRelPacket>());
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, pubRecPacket.CreateResponse<MqttPubRelPacket>());
             }
             else if (packet is MqttPubAckPacket || packet is MqttPubCompPacket)
             {
@@ -171,7 +178,7 @@ namespace MQTTnet.Core.Server
             }
             else if (packet is MqttPingReqPacket)
             {
-                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPingRespPacket());
+                await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, new MqttPingRespPacket());
             }
             else if (packet is MqttDisconnectPacket || packet is MqttConnectPacket)
             {
@@ -193,10 +200,17 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        private async Task HandleIncomingPublishPacketAsync(IMqttCommunicationAdapter adapter, MqttPublishPacket publishPacket)
+        private async Task HandleIncomingPublishPacketAsync(IMqttCommunicationAdapter adapter, MqttPublishPacket publishPacket, CancellationToken cancellationToken)
         {
             var applicationMessage = publishPacket.ToApplicationMessage();
-            _options.ApplicationMessageInterceptor?.Invoke(applicationMessage);
+
+            var interceptorContext = new MqttApplicationMessageInterceptorContext
+            {
+                ApplicationMessage = applicationMessage
+            };
+
+            _options.ApplicationMessageInterceptor?.Invoke(interceptorContext);
+            applicationMessage = interceptorContext.ApplicationMessage;
 
             if (applicationMessage.Retain)
             {
@@ -214,7 +228,7 @@ namespace MQTTnet.Core.Server
                     {
                         _sessionsManager.DispatchApplicationMessage(this, applicationMessage);
 
-                        await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token,
+                        await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken,
                             new MqttPubAckPacket { PacketIdentifier = publishPacket.PacketIdentifier });
 
                         return;
@@ -229,7 +243,7 @@ namespace MQTTnet.Core.Server
 
                         _sessionsManager.DispatchApplicationMessage(this, applicationMessage);
 
-                        await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token,
+                        await adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken,
                             new MqttPubRecPacket { PacketIdentifier = publishPacket.PacketIdentifier });
 
                         return;
@@ -239,14 +253,14 @@ namespace MQTTnet.Core.Server
             }
         }
 
-        private Task HandleIncomingPubRelPacketAsync(IMqttCommunicationAdapter adapter, MqttPubRelPacket pubRelPacket)
+        private Task HandleIncomingPubRelPacketAsync(IMqttCommunicationAdapter adapter, MqttPubRelPacket pubRelPacket, CancellationToken cancellationToken)
         {
             lock (_unacknowledgedPublishPackets)
             {
                 _unacknowledgedPublishPackets.Remove(pubRelPacket.PacketIdentifier);
             }
 
-            return adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, _cancellationTokenSource.Token, new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier });
+            return adapter.SendPacketsAsync(_options.DefaultCommunicationTimeout, cancellationToken, new MqttPubCompPacket { PacketIdentifier = pubRelPacket.PacketIdentifier });
         }
     }
 }

MQTTnet.Core/Server/MqttClientSubscribeResult.cs

@@ -0,0 +1,11 @@
+using MQTTnet.Core.Packets;
+
+namespace MQTTnet.Core.Server
+{
+    public class MqttClientSubscribeResult
+    {
+        public MqttSubAckPacket ResponsePacket { get; set; }
+
+        public bool CloseConnection { get; set; }
+    }
+}

MQTTnet.Core/Server/MqttClientSubscriptionsManager.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Microsoft.Extensions.Options;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
 
@@ -8,30 +9,45 @@ namespace MQTTnet.Core.Server
     public sealed class MqttClientSubscriptionsManager
     {
         private readonly Dictionary<string, MqttQualityOfServiceLevel> _subscribedTopics = new Dictionary<string, MqttQualityOfServiceLevel>();
+        private readonly MqttServerOptions _options;
 
-        public MqttClientSubscriptionsManager()
+        public MqttClientSubscriptionsManager(IOptions<MqttServerOptions> options)
         {
-            
+            _options = options?.Value ?? throw new ArgumentNullException(nameof(options));
         }
 
-        public MqttSubAckPacket Subscribe(MqttSubscribePacket subscribePacket)
+        public MqttClientSubscribeResult Subscribe(MqttSubscribePacket subscribePacket)
         {
             if (subscribePacket == null) throw new ArgumentNullException(nameof(subscribePacket));
 
             var responsePacket = subscribePacket.CreateResponse<MqttSubAckPacket>();
+            var closeConnection = false;
 
             lock (_subscribedTopics)
             {
                 foreach (var topicFilter in subscribePacket.TopicFilters)
                 {
+                    var interceptorContext = new MqttSubscriptionInterceptorContext("", topicFilter);
+                    _options.SubscriptionsInterceptor?.Invoke(interceptorContext);
+                    responsePacket.SubscribeReturnCodes.Add(interceptorContext.AcceptSubscription ? MqttSubscribeReturnCode.SuccessMaximumQoS1 : MqttSubscribeReturnCode.Failure);
+                    
+                    if (interceptorContext.CloseConnection)
+                    {
+                        closeConnection = true;
+                    }
 
-
-                    _subscribedTopics[topicFilter.Topic] = topicFilter.QualityOfServiceLevel;
-                    responsePacket.SubscribeReturnCodes.Add(MqttSubscribeReturnCode.SuccessMaximumQoS1); // TODO: Add support for QoS 2.
+                    if (interceptorContext.AcceptSubscription)
+                    {
+                        _subscribedTopics[topicFilter.Topic] = topicFilter.QualityOfServiceLevel;
+                    }
                 }
             }
 
-            return responsePacket;
+            return new MqttClientSubscribeResult
+            {
+                ResponsePacket = responsePacket,
+                CloseConnection = closeConnection
+            };
         }
 
         public MqttUnsubAckPacket Unsubscribe(MqttUnsubscribePacket unsubscribePacket)

MQTTnet.Core/Server/MqttServer.cs

@@ -56,8 +56,14 @@ namespace MQTTnet.Core.Server
 
             foreach (var applicationMessage in applicationMessages)
             {
-                _options.ApplicationMessageInterceptor?.Invoke(applicationMessage);
-                _clientSessionsManager.DispatchApplicationMessage(null, applicationMessage);
+                var interceptorContext = new MqttApplicationMessageInterceptorContext
+                {
+                    ApplicationMessage = applicationMessage
+                };
+
+                _options.ApplicationMessageInterceptor?.Invoke(interceptorContext);
+                
+                _clientSessionsManager.DispatchApplicationMessage(null, interceptorContext.ApplicationMessage);
             }
         }
 

MQTTnet.Core/Server/MqttServerOptions.cs

@@ -16,7 +16,9 @@ namespace MQTTnet.Core.Server
 
         public Func<MqttConnectPacket, MqttConnectReturnCode> ConnectionValidator { get; set; }
 
-        public Func<MqttApplicationMessage, MqttApplicationMessage> ApplicationMessageInterceptor { get; set; }
+        public Action<MqttApplicationMessageInterceptorContext> ApplicationMessageInterceptor { get; set; }
+
+        public Action<MqttSubscriptionInterceptorContext> SubscriptionsInterceptor { get; set; }
 
         public IMqttServerStorage Storage { get; set; }
     }

MQTTnet.Core/Server/MqttSubscriptionInterceptorContext.cs

@@ -0,0 +1,19 @@
+namespace MQTTnet.Core.Server
+{
+    public class MqttSubscriptionInterceptorContext
+    {
+        public MqttSubscriptionInterceptorContext(string clientId, TopicFilter topicFilter)
+        {
+            ClientId = clientId;
+            TopicFilter = topicFilter;
+        }
+
+        public string ClientId { get; }
+
+        public TopicFilter TopicFilter { get; }
+
+        public bool AcceptSubscription { get; set; } = true;
+
+        public bool CloseConnection { get; set; }
+    }
+}

Tests/MQTTnet.Core.Tests/MqttServerTests.cs

@@ -245,10 +245,9 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public async Task MqttServer_InterceptMessage()
         {
-            MqttApplicationMessage Interceptor(MqttApplicationMessage message)
+            void Interceptor(MqttApplicationMessageInterceptorContext context)
             {
-                message.Payload = Encoding.ASCII.GetBytes("extended");
-                return message;
+                context.ApplicationMessage.Payload = Encoding.ASCII.GetBytes("extended");
             }
 
             var serverAdapter = new TestMqttServerAdapter();

Tests/MQTTnet.Core.Tests/MqttSubscriptionsManagerTests.cs

@@ -1,4 +1,5 @@
-using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.Extensions.Options;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Core.Packets;
 using MQTTnet.Core.Protocol;
 using MQTTnet.Core.Server;
@@ -11,7 +12,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void MqttSubscriptionsManager_SubscribeSingleSuccess()
         {
-            var sm = new MqttClientSubscriptionsManager();
+            var sm = new MqttClientSubscriptionsManager(new OptionsWrapper<MqttServerOptions>(new MqttServerOptions()));
 
             var sp = new MqttSubscribePacket();
             sp.TopicFilters.Add(new TopicFilter("A/B/C", MqttQualityOfServiceLevel.AtMostOnce));
@@ -30,7 +31,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void MqttSubscriptionsManager_SubscribeSingleNoSuccess()
         {
-            var sm = new MqttClientSubscriptionsManager();
+            var sm = new MqttClientSubscriptionsManager(new OptionsWrapper<MqttServerOptions>(new MqttServerOptions()));
 
             var sp = new MqttSubscribePacket();
             sp.TopicFilters.Add(new TopicFilter("A/B/C", MqttQualityOfServiceLevel.AtMostOnce));
@@ -49,7 +50,7 @@ namespace MQTTnet.Core.Tests
         [TestMethod]
         public void MqttSubscriptionsManager_SubscribeAndUnsubscribeSingle()
         {
-            var sm = new MqttClientSubscriptionsManager();
+            var sm = new MqttClientSubscriptionsManager(new OptionsWrapper<MqttServerOptions>(new MqttServerOptions()));
 
             var sp = new MqttSubscribePacket();
             sp.TopicFilters.Add(new TopicFilter("A/B/C", MqttQualityOfServiceLevel.AtMostOnce));

Tests/MQTTnet.TestApp.NetCore/ServerTest.cs

@@ -35,16 +35,14 @@ namespace MQTTnet.TestApp.NetCore
 
                     options.Storage = new RetainedMessageHandler();
 
-                    options.ApplicationMessageInterceptor = message =>
+                    options.ApplicationMessageInterceptor = context =>
                     {
-                        if (MqttTopicFilterComparer.IsMatch(message.Topic, "/myTopic/WithTimestamp/#"))
+                        if (MqttTopicFilterComparer.IsMatch(context.ApplicationMessage.Topic, "/myTopic/WithTimestamp/#"))
                         {
                             // Replace the payload with the timestamp. But also extending a JSON 
                             // based payload with the timestamp is a suitable use case.
-                            message.Payload = Encoding.UTF8.GetBytes(DateTime.Now.ToString("O"));
-                        }
-
-                        return message;
+                            context.ApplicationMessage.Payload = Encoding.UTF8.GetBytes(DateTime.Now.ToString("O"));
+                        }                        
                     };
                 });