/* 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();
}
/* 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 */
}
}
}
internal void JoinIncomingConnection(UInt32 localIPAddress, UInt16 localIPPort, UInt32 destinationIPAddress, UInt16 destinationIPPort, UInt32 sequenceNumber, UInt16 windowSize)
{
if (_sourceIpAddressAndPortAssigned)
throw Utility.NewSocketException(SocketError.SocketError); /* is this correct; should we throw an exception if we already have an IP address/port assigned? */
_sourceIpAddressAndPortAssigned = true;
_srcIPAddress = localIPAddress;
_srcIPPort = localIPPort;
_destIPAddress = destinationIPAddress;
_destIPPort = destinationIPPort;
_receiveWindowLeftEdge = sequenceNumber + 1;
_receiveWindowRightEdge = (UInt32)(_receiveWindowLeftEdge + _receiveBuffer.Length);
//_transmitWindowLeftEdge = acknowledgementNumber;
//_transmitWindowRightEdge = _transmitWindowLeftEdge + windowSize;
_tcpStateMachine_CurrentState = TcpStateMachineState.OPENING;
_connectionState = ConnectionStateFlags.ConnectedFromDestination;
_tcpStateMachine_SendAckRequired = true;
_tcpStateMachine_ActionRequiredEvent.Set();
}