Example #1
0
        /* NOTE: this function processes incoming frames and stores flags/data; the TcpStateMachine function processes stored flags, advances the state machine as necessary, and sends out responses */
        internal override void OnPacketReceived(UInt32 sourceIPAddress, UInt32 destinationIPAddress, byte[] buffer, Int32 index, Int32 count)
        {
            if (_isDisposed)
                return;

            bool triggerStateMachine = false; /* we set this to true if the state machine needs to process our data */

            UInt32 sequenceNumber =
                ((UInt32)buffer[index + 4] << 24) +
                ((UInt32)buffer[index + 5] << 16) +
                ((UInt32)buffer[index + 6] << 8) +
                (UInt32)buffer[index + 7];

            UInt32 acknowledgmentNumber =
                ((UInt32)buffer[index + 8] << 24) +
                ((UInt32)buffer[index + 9] << 16) +
                ((UInt32)buffer[index + 10] << 8) +
                (UInt32)buffer[index + 11];

            Int32 headerLength = (((Int32)buffer[index + 12]) >> 4) * 4;

            bool flagFin = ((buffer[index + 13] & (1 << 0)) > 0);
            bool flagSyn = ((buffer[index + 13] & (1 << 1)) > 0);
            bool flagRst = ((buffer[index + 13] & (1 << 2)) > 0);
            bool flagPsh = ((buffer[index + 13] & (1 << 3)) > 0);
            bool flagAck = ((buffer[index + 13] & (1 << 4)) > 0);
            bool flagUrg = ((buffer[index + 13] & (1 << 5)) > 0);

            UInt16 windowSize = (UInt16)(
                (((UInt16)buffer[index + 14]) << 8) +
                ((UInt16)buffer[index + 15]));

            /* TODO: process header options */
            if (headerLength > TcpHandler.TCP_HEADER_MIN_LENGTH)
            {
                bool endOfListProcessed = false;
                byte optionLength = 0;

                int headerBufferPos = TcpHandler.TCP_HEADER_MIN_LENGTH;
                while (!endOfListProcessed && (headerBufferPos < headerLength))
                {
                    byte optionKind;
                    optionKind = buffer[headerBufferPos];

                    if (optionKind == 0 /* EOL = end of option list */)
                    {
                        endOfListProcessed = true;
                        optionLength = 1;
                    }
                    else if (optionKind == 1 /* NOP = no operation; used for padding */)
                    {
                        optionLength = 1;
                    }
                    else
                    {
                        if (headerBufferPos < headerLength - 1)
                            optionLength = (byte)(buffer[headerBufferPos + 1]);
                        else
                            optionLength = 1; /* backup in case other option length/list is corrupted */

                        /* interpret known TCP options */
                        switch (buffer[headerBufferPos])
                        {
                            case 2: /* MSS = Maximum Segment Size */
                                {
                                    if (optionLength == 4)
                                    {
                                        _transmitWindowMaximumSegmentSize = (UInt16)(
                                            (((UInt16)buffer[headerBufferPos + 2]) << 8) +
                                            buffer[headerBufferPos + 3]
                                            );
                                    }
                                }
                                break;
                            default:
                                break;
                        }
                    }

                    headerBufferPos += optionLength;
                }
            }

            /* recalculate transmit window size */
            /* NOTE: in edge cases, the transmit window could actually shrink.  if that happens, we need to pull in our "sent but not acknowledged" marker as well */
            if (_transmitWindowSentButNotAcknowledgedMarker > _transmitWindowLeftEdge + windowSize)
                _transmitWindowSentButNotAcknowledgedMarker = _transmitWindowLeftEdge + windowSize;
            _transmitWindowRightEdge = _transmitWindowLeftEdge + windowSize;

            /* if we receive a reset frame, close down our socket */
            if (flagRst && (acknowledgmentNumber >= _transmitWindowLeftEdge) && (acknowledgmentNumber <= (_transmitWindowRightEdge + 1)))
            {
                // close down our socket
                _connectionState = ConnectionStateFlags.None;
                if (_tcpStateMachine_CurrentState != TcpStateMachineState.CLOSING)
                {
                    /* TODO: clear our transmit buffers, notify user, etc. */
                    if (_receiveBufferSpaceFilledEvent != null) _receiveBufferSpaceFilledEvent.Set();
                }
                if (_outgoingConnectionClosedEvent != null) _outgoingConnectionClosedEvent.Set();
                _tcpStateMachine_CurrentState = TcpStateMachineState.CLOSED;
                triggerStateMachine = true;
            }

            // if we received a SYN and are in a valid state, store it and the corresponding sequence number now.
            if (flagSyn)
            {
                switch (_tcpStateMachine_CurrentState)
                {
                    case TcpStateMachineState.OPENING: /* special case of simultaneous connection request from both sides */
                    case TcpStateMachineState.SYN_SENT:
                        {
                            _receiveWindowLeftEdge = sequenceNumber + 1;
                            _receiveWindowRightEdge = (UInt32)(_receiveWindowLeftEdge + _receiveBuffer.Length);
                            _connectionState |= ConnectionStateFlags.ConnectedFromDestination;
                            _tcpStateMachine_SendAckRequired = true;
                            triggerStateMachine = true;
                        }
                        break;
                    case TcpStateMachineState.LISTEN:
                        {
                            try
                            {
                                if (_incomingConnectionBacklog + 1 > _incomingConnectionSockets.Count)
                                {
                                    Int32 newIncomingSocketHandle = _tcpHandler.IPv4Layer.CreateSocket(IPv4Layer.ProtocolType.Tcp, Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks, false);
                                    TcpSocket newIncomingSocket = (TcpSocket)_tcpHandler.IPv4Layer.GetSocket(newIncomingSocketHandle);
                                    UInt16 sourceIPPort = (UInt16)((((UInt16)buffer[index + 0]) << 8) + buffer[index + 1]);
                                    newIncomingSocket.ConnectionComplete += _incomingConnectionSockets_ConnectionComplete;
                                    newIncomingSocket.ConnectionAborted += _incomingConnectionSockets_ConnectionAborted;
                                    newIncomingSocket.JoinIncomingConnection(_srcIPAddress, _srcIPPort, sourceIPAddress, sourceIPPort, sequenceNumber, windowSize);

                                    _incomingConnectionSockets.Add(newIncomingSocket);
                                    _incomingConnectionBacklog++;
                                }
                                else
                                {
                                    // if our backlog is already full, discard the frame
                                    return;
                                }
                            }
                            catch
                            {
                                // if we could not create the incoming socket, discard the frame.
                                return;
                            }
                        }
                        break;
                    case TcpStateMachineState.ESTABLISHED:
                        {
                            // we will drop this packet to avoid connection takeover attacks, but we will still ACK the message in case the destination host's original SYN packet was lost.
                            /* TODO: ideally, we would only send an ACK in the scenario that we have not received any TCP stream data yet */
                            _tcpStateMachine_SendAckRequired = true;
                            triggerStateMachine = true;
                        }
                        break;
                    default:
                        // we are not in a valid state for an incoming connection request: drop this packet.
                        return;
                }
            }

            Int32 payloadLength = count - headerLength;

            /* if some of our data has been acknowledged, process the ACK and move the transmit window forward */
            if (flagAck && (acknowledgmentNumber > _transmitWindowLeftEdge) && (acknowledgmentNumber <= _transmitWindowSentButNotAcknowledgedMarker))
            {
                if (_currentOutgoingTransmission.TransmissionType == TransmissionType.SYN)
                {
                    _transmitWindowLeftEdge++;
                    _currentOutgoingTransmission = new TransmissionDetails(TransmissionType.None);
                    triggerStateMachine = true;
                }
                else
                {
                    // move our transmit buffer pointer forward
                    UInt32 bytesAcknowledged = (UInt32)((((UInt64)(acknowledgmentNumber - _transmitWindowLeftEdge)) + UInt32.MaxValue) % UInt32.MaxValue);
                    _transmitBufferFirstBytePos = (UInt32)((((UInt64)_transmitBufferFirstBytePos) + bytesAcknowledged) % UInt32.MaxValue);

                    // move our transmit window left edge forward
                    _transmitWindowLeftEdge = acknowledgmentNumber;
                    if (_transmitWindowLeftEdge == _transmitWindowSentButNotAcknowledgedMarker)
                    {
                        // all transmitted has been ACK'd, so abort our retry timer and send more data
                        _currentOutgoingTransmission = new TransmissionDetails(TransmissionType.None);
                    }
                    _transmitBufferSpaceFreedEvent.Set();
                    triggerStateMachine = true;
                }
                _tcpStateMachine_SendAckRequired = true;
            }

            if (_currentOutgoingTransmission.TransmissionType == TransmissionType.FIN)
            {
                if (acknowledgmentNumber == _transmitWindowLeftEdge + 1)
                {
                    _transmitWindowLeftEdge++;
                    _currentOutgoingTransmission = new TransmissionDetails(TransmissionType.None);
                    _connectionState &= ~ConnectionStateFlags.ConnectedToDestination;
                    triggerStateMachine = true;
                }
            }
                 
            Int32 receiveBufferBytesAvailable = GetReceiveBufferBytesFree();
            if (
                ((_tcpStateMachine_CurrentState == TcpStateMachineState.ESTABLISHED) || (_tcpStateMachine_CurrentState == TcpStateMachineState.CLOSING) || (_tcpStateMachine_CurrentState == TcpStateMachineState.TIME_WAIT))
                && (payloadLength > 0) && (receiveBufferBytesAvailable >= payloadLength))
            {
                if ((_connectionState & ConnectionStateFlags.ConnectedFromDestination) != 0)
                {
                    if (_receiveWindowLeftEdge == sequenceNumber)
                    {
                        // we have received data; store it as long as we have room for it.
                        lock (_receiveBufferLockObject)
                        {
                            Int32 numBytesStoredBeforeWrap = System.Math.Min((Int32)(_receiveBufferSize - _receiveBufferNextBytePos), (Int32)payloadLength);
                            Array.Copy(buffer, index + headerLength, _receiveBuffer, (Int32)_receiveBufferNextBytePos, numBytesStoredBeforeWrap);
                            _receiveBufferNextBytePos += (UInt32)numBytesStoredBeforeWrap;
                            if (_receiveBufferNextBytePos == _receiveBufferSize) _receiveBufferNextBytePos = 0; // handle wrap-around

                            // if we wrapped around, store the remaining bytes
                            if (numBytesStoredBeforeWrap < payloadLength)
                            {
                                Array.Copy(buffer, index + headerLength + numBytesStoredBeforeWrap, _receiveBuffer, (Int32)_receiveBufferNextBytePos, payloadLength - numBytesStoredBeforeWrap);
                                _receiveBufferNextBytePos += (UInt32)(payloadLength - numBytesStoredBeforeWrap);
                            }
                        }
                        _receiveWindowLeftEdge = (UInt32)(((UInt64)_receiveWindowLeftEdge + (UInt64)payloadLength) % UInt32.MaxValue); /* TODO: handle _receiveWindowScale here */
                        _receiveBufferSpaceFilledEvent.Set();
                        _tcpStateMachine_SendAckRequired = true;
                        triggerStateMachine = true;
                    }
                    else
                    {
                        // out of order packet; send an ACK so that the destination host knows what segment data we are expecting
                        /* TODO: we should really have an "out of order/duplicate packet counter" here, and only send a dummy ACK when that counter meets its upper threshold */
                        _tcpStateMachine_SendAckRequired = true;
                        triggerStateMachine = true;
                    }
                }
            }

            // if we received a FIN and are in a valid state, store it and the corresponding sequence number now.
            if (flagFin && (acknowledgmentNumber >= _transmitWindowLeftEdge) && (acknowledgmentNumber <= (_transmitWindowRightEdge + 1)))
            {
                switch (_tcpStateMachine_CurrentState)
                {
                    case TcpStateMachineState.ESTABLISHED:
                    case TcpStateMachineState.CLOSING:
                        {
                            _receiveWindowLeftEdge = (UInt32)(sequenceNumber + payloadLength + 1);
                            _receiveWindowRightEdge = _receiveWindowLeftEdge;
                            _connectionState &= ~ConnectionStateFlags.ConnectedFromDestination;
                            _tcpStateMachine_SendAckRequired = true;
                            // if we weren't already closing the connection from our end, make sure that our TCP socket is now in closing state.
                            _tcpStateMachine_CurrentState = TcpStateMachineState.CLOSING;

                            triggerStateMachine = true;
                        }
                        break;
                    default:
                        // we are not in a valid state for an incoming close request: drop this packet.
                        break;
                }
            }

            if (triggerStateMachine)
                _tcpStateMachine_ActionRequiredEvent.Set();
        }
Example #2
0
        /* NOTE: this function advances the state machine as necessary and sends out responses as necessary; the OnPacketReceived function processes incoming frames and stores the flags/data */
        void TcpStateMachine()
        {
            while (true)
            {
                // wait for a change which requires the TCP state machine to change state or process data
                Int32 millisecondsTimeout = System.Math.Max(0, (Int32)(((_currentOutgoingTransmission.TransmissionType == TransmissionType.None) || (_currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks == Int64.MaxValue)) ? Timeout.Infinite : (_currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks - Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks) / TimeSpan.TicksPerMillisecond));
                _tcpStateMachine_ActionRequiredEvent.WaitOne(millisecondsTimeout, false);

                if (_isDisposed)
                    return;

                switch (_tcpStateMachine_CurrentState)
                {
                    case TcpStateMachineState.CLOSED:
                        {
                            /* there is nothing to be done if our socket is CLOSED */
                        }
                        break;
                    case TcpStateMachineState.OPENING:
                        {
                            // if our app has requested an outgoing connection, try connecting now.
                            // set the initial sequence number
                            UInt32 initialSequenceNumber = (UInt32)(_randomGenerator.Next() + _randomGenerator.Next()); /* initial sequence number */
                            _transmitWindowLeftEdge = initialSequenceNumber;
                            _transmitWindowSentButNotAcknowledgedMarker = _transmitWindowLeftEdge + 1;
                            _transmitWindowRightEdge = _transmitWindowLeftEdge + _transmitWindowMaximumSegmentSize;

                            Int64 currentTimeInMachineTicks = Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks;
                            // move the state machine forward to "SYN_SENT" so that it can respond to an incoming SYN + ACK message
                            _tcpStateMachine_CurrentState = TcpStateMachineState.SYN_SENT;

                            lock (_currentOutgoingTransmissionLock)
                            {
                                // set our outstanding transmission type to SYN (which flag occupies a sequence #)
                                _currentOutgoingTransmission = new TransmissionDetails(TransmissionType.SYN);
                                _currentOutgoingTransmission.TransmissionAttemptsCounter = 1;
                                _currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds = SYN_INITIAL_RETRY_TIMEOUT_IN_MS;
                                _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks = currentTimeInMachineTicks + (_currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds * TimeSpan.TicksPerMillisecond);
                                _currentOutgoingTransmission.MaximumTimeoutInMachineTicks = currentTimeInMachineTicks + (SYN_MAX_RETRY_TIMEOUT_IN_MS * TimeSpan.TicksPerMillisecond);
                            }

                            _tcpHandler.SendTcpSegment(_srcIPAddress, _destIPAddress, _srcIPPort, _destIPPort, _transmitWindowLeftEdge, _receiveWindowLeftEdge, GetReceiveBufferBytesFree(), 
                                ((_connectionState & ConnectionStateFlags.ConnectedFromDestination) > 0),
                                false, false, true, false,
                                new TcpHandler.TcpOption[] { new TcpHandler.TcpOption(2 /* Maximum Segment Size */, new byte[] { (byte)((_receiveWindowMaximumSegmentSize >> 8) & 0xFF), (byte)(_receiveWindowMaximumSegmentSize & 0xFF) }) }, 
                                new byte[] { }, 0, 0, Int64.MaxValue); /* TODO: use timeout on sending segment */
                            _tcpStateMachine_SendAckRequired = false;
                        }
                        break;
                    case TcpStateMachineState.SYN_SENT:
                        {
                            if (_currentOutgoingTransmission.TransmissionType == TransmissionType.SYN)
                            {
                                // if we have not yet received an ACK for our SYN and our timeout has expired, resend it now.
                                Int64 currentTimeInMachineTicks = Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks;
                                if (currentTimeInMachineTicks > _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks /* timeout occurred */)
                                {
                                    if (currentTimeInMachineTicks > _currentOutgoingTransmission.MaximumTimeoutInMachineTicks)
                                    {
                                        /* TODO: abort connection attempt */
                                        /* TODO: should we send a RESET segment? */
                                        _connectionState = ConnectionStateFlags.None;
                                        _outgoingConnectionCompleteEvent.Set();
                                        /* raise our connection aborted event; this is used to notify a Listener socket that our connection has been successfully established */
                                        if (ConnectionAborted != null) ConnectionAborted(this);
                                    }
                                    else
                                    {
                                        _currentOutgoingTransmission.TransmissionAttemptsCounter += 1;
                                        _currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds *= 2;
                                        _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks = currentTimeInMachineTicks + (_currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds * TimeSpan.TicksPerMillisecond);
                                        _tcpHandler.SendTcpSegment(_srcIPAddress, _destIPAddress, _srcIPPort, _destIPPort, _transmitWindowLeftEdge, _receiveWindowLeftEdge, GetReceiveBufferBytesFree(),
                                            ((_connectionState & ConnectionStateFlags.ConnectedFromDestination) > 0), 
                                            false, false, true, false,
                                            new TcpHandler.TcpOption[] { new TcpHandler.TcpOption(2 /* Maximum Segment Size */, new byte[] { (byte)((_receiveWindowMaximumSegmentSize >> 8) & 0xFF), (byte)(_receiveWindowMaximumSegmentSize & 0xFF) }) },
                                            new byte[] { }, 0, 0, Int64.MaxValue); /* TODO: enable timeout */
                                    }
                                }

                            }
                            else
                            {
                                // our SYN has been ack'd; make sure we've marked our outgoing connection as valid
                                _connectionState |= ConnectionStateFlags.ConnectedToDestination;
                            }

                            if (((_connectionState & ConnectionStateFlags.ConnectedFromDestination) != 0) &&
                                ((_connectionState & ConnectionStateFlags.ConnectedToDestination) != 0))
                            {
                                _tcpStateMachine_CurrentState = TcpStateMachineState.ESTABLISHED;
                                _outgoingConnectionCompleteEvent.Set();
                                /* raise our connected event; this is used to notify a Listener socket that our connection has been successfully established */
                                if (ConnectionComplete != null) ConnectionComplete(this);
                            }
                        }
                        break;
                    case TcpStateMachineState.ESTABLISHED:
                        {
                            Int32 transmitBufferFilledLength = GetTransmitBufferBytesFilled();
                            if (transmitBufferFilledLength == 0)
                                break;

                            // if we have data to send, first make sure we send the initial attempt.
                            if (_currentOutgoingTransmission.TransmissionType == TransmissionType.None)
                            {
                                Int64 currentTimeInMachineTicks = Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks;

                                lock (_currentOutgoingTransmissionLock)
                                {
                                    // set our outstanding transmission type to data 
                                    _currentOutgoingTransmission = new TransmissionDetails(TransmissionType.Data);
                                    _currentOutgoingTransmission.TransmissionAttemptsCounter = 1;
                                    _currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds = _tcpStateMachine_CalculatedRetryTimeoutInMilliseconds;
                                    _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks = currentTimeInMachineTicks + (_currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds * TimeSpan.TicksPerMillisecond);
                                    _currentOutgoingTransmission.MaximumTimeoutInMachineTicks = currentTimeInMachineTicks + (((_transmitTimeoutInMilliseconds > 0) ? _transmitTimeoutInMilliseconds : DATA_MAX_RETRY_TIMEOUT_IN_MS) * TimeSpan.TicksPerMillisecond);
                                }

                                // calculate the number of bytes to send
                                Int32 transmitWindowWidth = (Int32)((((UInt64)_transmitWindowRightEdge + UInt32.MaxValue) - _transmitWindowLeftEdge) % UInt32.MaxValue);
                                Int32 totalBytesToSend = System.Math.Min(transmitWindowWidth, transmitBufferFilledLength);

                                /* NOTE: this code is copy-and-paste synchronized with the "send data" code in the "re-attempt" section below */
                                // max bytes per segment (_transmitWindowMaximumSegmentSize)
                                UInt32 absoluteWindowOffset = _transmitWindowLeftEdge;
                                Int32 absoluteBufferOffset = (Int32)_transmitBufferFirstBytePos;
                                Int32 relativeOffset = 0;
                                while (relativeOffset < totalBytesToSend)
                                {
                                    Int32 bytesToSendBeforeWrap = (Int32)System.Math.Min(_transmitBuffer.Length - absoluteBufferOffset, totalBytesToSend);
                                    Int32 currentBytesToSend = (Int32)System.Math.Min(bytesToSendBeforeWrap, _transmitWindowMaximumSegmentSize);
                                    _tcpHandler.SendTcpSegment(_srcIPAddress, _destIPAddress, _srcIPPort, _destIPPort, 
                                        (UInt32)absoluteWindowOffset, _receiveWindowLeftEdge, GetReceiveBufferBytesFree(), true, 
                                        (totalBytesToSend - relativeOffset == currentBytesToSend), false, false, false, null, 
                                        _transmitBuffer, absoluteBufferOffset, currentBytesToSend, Int64.MaxValue); /* TODO: use timeout on sending segment */

                                    relativeOffset += currentBytesToSend;
                                    absoluteBufferOffset = (absoluteBufferOffset + currentBytesToSend) % _transmitBuffer.Length;
                                    absoluteWindowOffset = (UInt32)((absoluteWindowOffset + currentBytesToSend) % UInt32.MaxValue);
                                }
                                _transmitWindowSentButNotAcknowledgedMarker = absoluteWindowOffset;

                                _tcpStateMachine_SendAckRequired = false;
                            }
                            else if (_currentOutgoingTransmission.TransmissionType == TransmissionType.Data)
                            {
                                // if timeout has occured, resend all previously-sent segments
                                Int64 currentTimeInMachineTicks = Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks;
                                if (currentTimeInMachineTicks > _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks /* timeout occurred */)
                                {
                                    if (currentTimeInMachineTicks > _currentOutgoingTransmission.MaximumTimeoutInMachineTicks)
                                    {
                                        /* TODO: send RESET to destination host */
                                        /* abort transmission attempt and close socket */
                                        _connectionState = ConnectionStateFlags.None;
                                        _tcpStateMachine_CurrentState = TcpStateMachineState.CLOSED;
                                        if (_receiveBufferSpaceFilledEvent != null) _receiveBufferSpaceFilledEvent.Set(); 
                                        if (_outgoingConnectionClosedEvent != null) _outgoingConnectionClosedEvent.Set();
                                    }
                                    else
                                    {
                                        /* retry transmission attempt */
                                        _currentOutgoingTransmission.TransmissionAttemptsCounter += 1;
                                        _currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds *= 2;
                                        _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks = currentTimeInMachineTicks + (_currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds * TimeSpan.TicksPerMillisecond);

                                        // calculate the number of bytes to send
                                        Int32 transmitWindowUsedWidth = (Int32)((((UInt64)_transmitWindowSentButNotAcknowledgedMarker + UInt32.MaxValue) - _transmitWindowLeftEdge) % UInt32.MaxValue);
                                        Int32 totalBytesToSend = System.Math.Min(transmitWindowUsedWidth, transmitBufferFilledLength);

                                        /* NOTE: this code is copy-and-paste synchronized with the "send data" code in the "initial attempt" section above */
                                        // max bytes per segment (_transmitWindowMaximumSegmentSize)
                                        UInt32 absoluteWindowOffset = _transmitWindowLeftEdge;
                                        Int32 absoluteBufferOffset = (Int32)_transmitBufferFirstBytePos;
                                        Int32 relativeOffset = 0;
                                        while (relativeOffset < totalBytesToSend)
                                        {
                                            Int32 bytesToSendBeforeWrap = (Int32)System.Math.Min(_transmitBuffer.Length - absoluteBufferOffset, totalBytesToSend);
                                            Int32 currentBytesToSend = (Int32)System.Math.Min(bytesToSendBeforeWrap, _transmitWindowMaximumSegmentSize);
                                            _tcpHandler.SendTcpSegment(_srcIPAddress, _destIPAddress, _srcIPPort, _destIPPort,
                                                (UInt32)absoluteWindowOffset, _receiveWindowLeftEdge, GetReceiveBufferBytesFree(), true,
                                                (totalBytesToSend - relativeOffset == currentBytesToSend), false, false, false, null,
                                                _transmitBuffer, absoluteBufferOffset, currentBytesToSend, Int64.MaxValue); /* TODO: use timeout on sending segment */

                                            relativeOffset += currentBytesToSend;
                                            absoluteBufferOffset = (absoluteBufferOffset + currentBytesToSend) % _transmitBuffer.Length;
                                            absoluteWindowOffset = (UInt32)((absoluteWindowOffset + currentBytesToSend) % UInt32.MaxValue);
                                        }
                                        _transmitWindowSentButNotAcknowledgedMarker = absoluteWindowOffset;

                                        _tcpStateMachine_SendAckRequired = false;
                                    }
                                }
                            }
                        }
                        break;
                    case TcpStateMachineState.CLOSING:
                        {
                            /* if we are no longer connected to or from the destination host, move to the CLOSED state. */
                            if (((_connectionState & ConnectionStateFlags.ConnectedToDestination) == 0) &&
                                ((_connectionState & ConnectionStateFlags.ConnectedFromDestination) == 0))
                            {
                                /* TODO: we should move to 2MSL state (blocking this endpoint pair from being used for 2 * MSL) */
                                if (_receiveBufferSpaceFilledEvent != null) _receiveBufferSpaceFilledEvent.Set();
                                if (_outgoingConnectionClosedEvent != null) _outgoingConnectionClosedEvent.Set();
                                break;
                            }

                            /* if we are still connected to the destination, send a FIN packet (or retry sending, if it has already been sent */
                            if ((_connectionState & ConnectionStateFlags.ConnectedToDestination) > 0)
                            {
                                // if we have not yet sent the FIN request, do so now.
                                if (_currentOutgoingTransmission.TransmissionType != TransmissionType.FIN)
                                {
                                    /* purge outgoing buffers */
                                    _transmitWindowSentButNotAcknowledgedMarker = _transmitWindowLeftEdge;
                                    _transmitWindowRightEdge = _transmitWindowLeftEdge;
                                    /* TODO: notify any pending Send(...) calls that their transmission is being aborted. */

                                    Int64 currentTimeInMachineTicks = Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks;

                                    lock (_currentOutgoingTransmissionLock)
                                    {
                                        // set our outstanding transmission type to FIN (which flag occupies a sequence #)
                                        _currentOutgoingTransmission = new TransmissionDetails(TransmissionType.FIN);
                                        _currentOutgoingTransmission.TransmissionAttemptsCounter = 1;
                                        _currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds = SYN_INITIAL_RETRY_TIMEOUT_IN_MS;
                                        _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks = currentTimeInMachineTicks + (_currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds * TimeSpan.TicksPerMillisecond);
                                        _currentOutgoingTransmission.MaximumTimeoutInMachineTicks = currentTimeInMachineTicks + (SYN_MAX_RETRY_TIMEOUT_IN_MS * TimeSpan.TicksPerMillisecond);
                                    }

                                    _tcpHandler.SendTcpSegment(_srcIPAddress, _destIPAddress, _srcIPPort, _destIPPort, _transmitWindowLeftEdge, _receiveWindowLeftEdge, GetReceiveBufferBytesFree(),
                                        true, false, false, false, true, null, new byte[] { }, 0, 0, Int64.MaxValue); /* TODO: use timeout on sending segment */
                                    _tcpStateMachine_SendAckRequired = false;
                                }
                                else
                                {
                                    // otherwise, if we have not received an ACK for our FIN and our timeout has expired, resend it now.
                                    Int64 currentTimeInMachineTicks = Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks;
                                    if (currentTimeInMachineTicks > _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks /* timeout occurred */)
                                    {
                                        if (currentTimeInMachineTicks > _currentOutgoingTransmission.MaximumTimeoutInMachineTicks)
                                        {
                                            /* abort close attempt */
                                            _connectionState = ConnectionStateFlags.None;
                                            _tcpStateMachine_CurrentState = TcpStateMachineState.CLOSED;
                                            if (_receiveBufferSpaceFilledEvent != null) _receiveBufferSpaceFilledEvent.Set();
                                            if (_outgoingConnectionClosedEvent != null) _outgoingConnectionClosedEvent.Set();
                                        }
                                        else
                                        {
                                            /* retry close attempt */
                                            _currentOutgoingTransmission.TransmissionAttemptsCounter += 1;
                                            _currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds *= 2;
                                            _currentOutgoingTransmission.CurrentRetryTimeoutInMachineTicks = currentTimeInMachineTicks + (_currentOutgoingTransmission.CurrentRetryTimeoutInMilliseconds * TimeSpan.TicksPerMillisecond);
                                            _tcpHandler.SendTcpSegment(_srcIPAddress, _destIPAddress, _srcIPPort, _destIPPort, _transmitWindowLeftEdge, _receiveWindowLeftEdge, GetReceiveBufferBytesFree(),
                                                true, false, false, false, true, null, new byte[] { }, 0, 0, Int64.MaxValue); /* TODO: enable timeout */
                                        }
                                    }
                                }
                            }

                            /* we ignore the destination host's request to stay connected to us after we initiate a FIN; once our FIN transmission timeout occurs we move to CLOSED or 2MSL state */
                            //if ((_connectionState & ConnectionStateFlags.ConnectedFromDestination) > 0)
                            //{
                            //}
                        }
                        break;
                    default:
                        break;
                }

                /* send any outgoing data along with any required ACKs */
                if (_tcpStateMachine_SendAckRequired)
                {
                    _tcpStateMachine_SendAckRequired = false;
                    _tcpHandler.SendTcpSegment(_srcIPAddress, _destIPAddress, _srcIPPort, _destIPPort, _transmitWindowLeftEdge, _receiveWindowLeftEdge, GetReceiveBufferBytesFree(),
                        true, false, false, (_currentOutgoingTransmission.TransmissionType == TransmissionType.SYN), false, null, new byte[] { }, 0, 0, Int64.MaxValue); /* TODO: enable timeout */
                }
            }
        }
Example #3
0
        public override void Dispose()
        {
            base.Dispose();

            // shut down our state machine thread
            if (_tcpStateMachine_ActionRequiredEvent != null)
            {
                _tcpStateMachine_ActionRequiredEvent.Set();
                _tcpStateMachine_ActionRequiredEvent = null;
            }

            if (_outgoingConnectionCompleteEvent != null)
            {
                _outgoingConnectionCompleteEvent.Set();
                _outgoingConnectionCompleteEvent = null;
            }

            _incomingConnectionSockets = null;

            _currentOutgoingTransmission = new TransmissionDetails(TransmissionType.None);
            _currentOutgoingTransmissionLock = null;

            _receiveBuffer = null;
            _receiveBufferLockObject = null;
            if (_receiveBufferSpaceFilledEvent != null) _receiveBufferSpaceFilledEvent.Set();
            _receiveBufferSpaceFilledEvent = null;

            _transmitBuffer = null;
            _transmitBufferLockObject = null;
            if (_transmitBufferSpaceFreedEvent != null) _transmitBufferSpaceFreedEvent.Set();
            _transmitBufferSpaceFreedEvent = null;

            _randomGenerator = null;

            _tcpHandler = null;
        }