src/Vehicle/MAVLinkFTPManager.cc

+/****************************************************************************
+ *
+ *   (c) 2009-2016 QGROUNDCONTROL PROJECT <http://www.qgroundcontrol.org>
+ *
+ * QGroundControl is licensed according to the terms in the file
+ * COPYING.md in the root of the source code directory.
+ *
+ ****************************************************************************/
+
+
+#include "MAVLinkFTPManager.h"
+#include "Vehicle.h"
+#include "QGCApplication.h"
+
+#include <QFile>
+#include <QDir>
+#include <string>
+
+QGC_LOGGING_CATEGORY(MAVLinkFTPManagerLog, "MAVLinkFTPManagerLog")
+
+MAVLinkFTPManager::MAVLinkFTPManager(Vehicle* vehicle)
+    : QObject   (vehicle)
+    , _vehicle  (vehicle)
+{
+    connect(&_ackTimer, &QTimer::timeout, this, &MAVLinkFTPManager::_ackTimeout);
+    
+    _lastOutgoingRequest.hdr.seqNumber = 0;
+
+    _systemIdServer = _vehicle->id();
+    
+    // Make sure we don't have bad structure packing
+    Q_ASSERT(sizeof(RequestHeader) == 12);
+}
+
+/// Respond to the Ack associated with the Open command with the next read command.
+void MAVLinkFTPManager::_openAckResponse(Request* openAck)
+{
+    qCDebug(MAVLinkFTPManagerLog) << QString("_openAckResponse: _currentOperation(%1) _readFileLength(%2)").arg(_currentOperation).arg(openAck->openFileLength);
+    
+	Q_ASSERT(_currentOperation == kCOOpenRead || _currentOperation == kCOOpenBurst);
+	_currentOperation = _currentOperation == kCOOpenRead ? kCORead : kCOBurst;
+    _activeSession = openAck->hdr.session;
+    
+    // File length comes back in data
+    Q_ASSERT(openAck->hdr.size == sizeof(uint32_t));
+    _downloadFileSize = openAck->openFileLength;
+    
+    // Start the sequence of read commands
+
+    _downloadOffset = 0;            // Start reading at beginning of file
+    _readFileAccumulator.clear();   // Start with an empty file
+    _missingDownloadedBytes = 0;
+    _downloadingMissingParts = false;
+    _missingData.clear();
+
+    Request request;
+    request.hdr.session = _activeSession;
+	Q_ASSERT(_currentOperation == kCORead || _currentOperation == kCOBurst);
+	request.hdr.opcode = _currentOperation == kCORead ? kCmdReadFile : kCmdBurstReadFile;
+    request.hdr.offset = _downloadOffset;
+    request.hdr.size = sizeof(request.data);
+
+    _sendRequest(&request);
+}
+
+/// request the next missing part of a (partially) downloaded file
+void MAVLinkFTPManager::_requestMissingData()
+{
+    if (_missingData.empty()) {
+        _downloadingMissingParts = false;
+        _missingDownloadedBytes = 0;
+        // there might be more data missing at the end
+        if ((uint32_t)_readFileAccumulator.length() != _downloadFileSize) {
+            _downloadOffset = _readFileAccumulator.length();
+            qCDebug(MAVLinkFTPManagerLog) << QString("_requestMissingData: missing parts done, downloadOffset(%1) downloadFileSize(%2)")
+                    .arg(_downloadOffset).arg(_downloadFileSize);
+        } else {
+            _closeDownloadSession(true);
+            return;
+        }
+    } else {
+        qCDebug(MAVLinkFTPManagerLog) << QString("_requestMissingData: offset(%1) size(%2)").arg(_missingData.head().offset).arg(_missingData.head().size);
+
+        _downloadOffset = _missingData.head().offset;
+    }
+
+    Request request;
+    _currentOperation = kCORead;
+    request.hdr.session = _activeSession;
+    request.hdr.opcode = kCmdReadFile;
+    request.hdr.offset = _downloadOffset;
+    request.hdr.size = sizeof(request.data);
+
+    _sendRequest(&request);
+}
+
+/// Closes out a download session by writing the file and doing cleanup.
+///     @param success true: successful download completion, false: error during download
+void MAVLinkFTPManager::_closeDownloadSession(bool success)
+{
+    qCDebug(MAVLinkFTPManagerLog) << QString("_closeDownloadSession: success(%1) missingBytes(%2)").arg(success).arg(_missingDownloadedBytes);
+    
+    _currentOperation = kCOIdle;
+    
+    if (success) {
+        if (_missingDownloadedBytes > 0 || (uint32_t)_readFileAccumulator.length() < _downloadFileSize) {
+            // we're not done yet: request the missing parts individually (either we had missing parts or
+            // the last (few) packets right before the EOF got dropped)
+            _downloadingMissingParts = true;
+            _requestMissingData();
+            return;
+        }
+
+        QString downloadFilePath = _readFileDownloadDir.absoluteFilePath(_readFileDownloadFilename);
+
+        QFile file(downloadFilePath);
+        if (!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
+            _emitErrorMessage(tr("Unable to open local file for writing (%1)").arg(downloadFilePath));
+            return;
+        }
+
+        qint64 bytesWritten = file.write((const char *)_readFileAccumulator, _readFileAccumulator.length());
+        if (bytesWritten != _readFileAccumulator.length()) {
+            file.close();
+            _emitErrorMessage(tr("Unable to write data to local file (%1)").arg(downloadFilePath));
+            return;
+        }
+        file.close();
+
+        emit commandComplete();
+    }
+    
+    _readFileAccumulator.clear();
+    
+    // Close the open session
+    _sendResetCommand();
+}
+
+/// Closes out an upload session doing cleanup.
+///     @param success true: successful upload completion, false: error during download
+void MAVLinkFTPManager::_closeUploadSession(bool success)
+{
+    qCDebug(MAVLinkFTPManagerLog) << QString("_closeUploadSession: success(%1)").arg(success);
+    
+    _currentOperation = kCOIdle;
+    _writeFileAccumulator.clear();
+    _writeFileSize = 0;
+    
+    if (success) {
+        emit commandComplete();
+    }
+    
+    // Close the open session
+    _sendResetCommand();
+}
+
+/// Respond to the Ack associated with the Read or Stream commands.
+///		@param readFile: true: read file, false: stream file
+void MAVLinkFTPManager::_downloadAckResponse(Request* readAck, bool readFile)
+{
+    if (readAck->hdr.session != _activeSession) {
+        _closeDownloadSession(false /* failure */);
+        _emitErrorMessage(tr("Download: Incorrect session returned"));
+        return;
+    }
+
+    if (readAck->hdr.offset != _downloadOffset) {
+        if (readFile) {
+            _closeDownloadSession(false /* failure */);
+            _emitErrorMessage(tr("Download: Offset returned (%1) differs from offset requested/expected (%2)").arg(readAck->hdr.offset).arg(_downloadOffset));
+            return;
+        } else { // burst
+            if (readAck->hdr.offset < _downloadOffset) { // old data: ignore it
+                _setupAckTimeout();
+                return;
+            }
+            // keep track of missing data chunks
+            MissingData missingData;
+            missingData.offset = _downloadOffset;
+            missingData.size = readAck->hdr.offset - _downloadOffset;
+            _missingData.push_back(missingData);
+            _missingDownloadedBytes += readAck->hdr.offset - _downloadOffset;
+            qCDebug(MAVLinkFTPManagerLog) << QString("_downloadAckResponse: missing data: offset(%1) size(%2)").arg(missingData.offset).arg(missingData.size);
+            _downloadOffset = readAck->hdr.offset;
+            _readFileAccumulator.resize(_downloadOffset); // placeholder for the missing data
+        }
+    }
+    
+    qCDebug(MAVLinkFTPManagerLog) << QString("_downloadAckResponse: offset(%1) size(%2) burstComplete(%3)").arg(readAck->hdr.offset).arg(readAck->hdr.size).arg(readAck->hdr.burstComplete);
+
+    if (_downloadingMissingParts) {
+        Q_ASSERT(_missingData.head().offset == _downloadOffset);
+        _missingDownloadedBytes -= readAck->hdr.size;
+        _readFileAccumulator.replace(_downloadOffset, readAck->hdr.size, (const char*)readAck->data, readAck->hdr.size);
+        if (_missingData.head().size <= readAck->hdr.size) {
+            _missingData.pop_front();
+        } else {
+            _missingData.head().size -= readAck->hdr.size;
+            _missingData.head().offset += readAck->hdr.size;
+        }
+    } else {
+        _downloadOffset += readAck->hdr.size;
+        _readFileAccumulator.append((const char*)readAck->data, readAck->hdr.size);
+    }
+    
+    if (_downloadFileSize != 0) {
+        emit commandProgress(100 * ((float)(_readFileAccumulator.length() - _missingDownloadedBytes) / (float)_downloadFileSize));
+    }
+
+    if (_downloadingMissingParts) {
+        _requestMissingData();
+    } else if (readFile || readAck->hdr.burstComplete) {
+        // Possibly still more data to read, send next read request
+
+        Request request;
+        request.hdr.session = _activeSession;
+        request.hdr.opcode = readFile ? kCmdReadFile : kCmdBurstReadFile;
+        request.hdr.offset = _downloadOffset;
+        request.hdr.size = 0;
+
+        _sendRequest(&request);
+    } else if (!readFile) {
+        // Streaming, so next ack should come automatically
+        _setupAckTimeout();
+    }
+}
+
+/// @brief Respond to the Ack associated with the List command.
+void MAVLinkFTPManager::_listAckResponse(Request* listAck)
+{
+    if (listAck->hdr.offset != _listOffset) {
+        // this is a real error (directory listing is synchronous), no need to retransmit
+        _currentOperation = kCOIdle;
+        _emitErrorMessage(tr("List: Offset returned (%1) differs from offset requested (%2)").arg(listAck->hdr.offset).arg(_listOffset));
+        return;
+    }
+
+    uint8_t offset = 0;
+    uint8_t cListEntries = 0;
+    uint8_t cBytes = listAck->hdr.size;
+
+    // parse filenames out of the buffer
+    while (offset < cBytes) {
+        const char * ptr = ((const char *)listAck->data) + offset;
+
+        // get the length of the name
+        uint8_t cBytesLeft = cBytes - offset;
+        uint8_t nlen = static_cast<uint8_t>(strnlen(ptr, cBytesLeft));
+        if ((*ptr == 'S' && nlen > 1) || (*ptr != 'S' && nlen < 2)) {
+            _currentOperation = kCOIdle;
+            _emitErrorMessage(tr("Incorrectly formed list entry: '%1'").arg(ptr));
+            return;
+        } else if (nlen == cBytesLeft) {
+            _currentOperation = kCOIdle;
+            _emitErrorMessage(tr("Missing NULL termination in list entry"));
+            return;
+        }
+
+        // Returned names are prepended with D for directory, F for file, S for skip
+        if (*ptr == 'F' || *ptr == 'D') {
+            // put it in the view
+            _emitListEntry(ptr);
+        } else if (*ptr == 'S') {
+            // do nothing
+        } else {
+            qDebug() << "unknown entry" << ptr;
+        }
+
+        // account for the name + NUL
+        offset += nlen + 1;
+
+        cListEntries++;
+    }
+
+    if (listAck->hdr.size == 0 || cListEntries == 0) {
+        // Directory is empty, we're done
+        Q_ASSERT(listAck->hdr.opcode == kRspAck);
+        _currentOperation = kCOIdle;
+        emit commandComplete();
+    } else {
+        // Possibly more entries to come, need to keep trying till we get EOF
+        _currentOperation = kCOList;
+        _listOffset += cListEntries;
+        _sendListCommand();
+    }
+}
+
+/// @brief Respond to the Ack associated with the create command.
+void MAVLinkFTPManager::_createAckResponse(Request* createAck)
+{
+    qCDebug(MAVLinkFTPManagerLog) << "_createAckResponse";
+    
+    _currentOperation = kCOWrite;
+    _activeSession = createAck->hdr.session;
+
+    // Start the sequence of write commands from the beginning of the file
+
+    _writeOffset = 0;
+    _writeSize = 0;
+    
+    _writeFileDatablock();
+}
+
+/// @brief Respond to the Ack associated with the write command.
+void MAVLinkFTPManager::_writeAckResponse(Request* writeAck)
+{
+    if(_writeOffset + _writeSize >= _writeFileSize){
+        _closeUploadSession(true /* success */);
+        return;
+    }
+
+    if (writeAck->hdr.session != _activeSession) {
+        _closeUploadSession(false /* failure */);
+        _emitErrorMessage(tr("Write: Incorrect session returned"));
+        return;
+    }
+
+    if (writeAck->hdr.offset != _writeOffset) {
+        _closeUploadSession(false /* failure */);
+        _emitErrorMessage(tr("Write: Offset returned (%1) differs from offset requested (%2)").arg(writeAck->hdr.offset).arg(_writeOffset));
+        return;
+    }
+
+    if (writeAck->hdr.size != sizeof(uint32_t)) {
+        _closeUploadSession(false /* failure */);
+        _emitErrorMessage(tr("Write: Returned invalid size of write size data"));
+        return;
+    }
+
+
+    if( writeAck->writeFileLength !=_writeSize) {
+        _closeUploadSession(false /* failure */);
+        _emitErrorMessage(tr("Write: Size returned (%1) differs from size requested (%2)").arg(writeAck->writeFileLength).arg(_writeSize));
+        return;
+    }
+
+    _writeFileDatablock();
+}
+
+/// @brief Send next write file data block.
+void MAVLinkFTPManager::_writeFileDatablock(void)
+{
+    if (_writeOffset + _writeSize >= _writeFileSize){
+        _closeUploadSession(true /* success */);
+        return;
+    }
+
+    _writeOffset += _writeSize;
+
+    Request request;
+    request.hdr.session = _activeSession;
+    request.hdr.opcode = kCmdWriteFile;
+    request.hdr.offset = _writeOffset;
+
+    if(_writeFileSize -_writeOffset > sizeof(request.data) )
+        _writeSize = sizeof(request.data);
+    else
+        _writeSize = _writeFileSize - _writeOffset;
+
+    request.hdr.size = _writeSize;
+
+    memcpy(request.data, &_writeFileAccumulator.data()[_writeOffset], _writeSize);
+
+    _sendRequest(&request);
+}
+
+void MAVLinkFTPManager::receiveMessage(mavlink_message_t message)
+{
+    // receiveMessage is signalled will all mavlink messages so we need to filter everything else out but ours.
+    if (message.msgid != MAVLINK_MSG_ID_FILE_TRANSFER_PROTOCOL) {
+        return;
+    }
+
+    mavlink_file_transfer_protocol_t data;
+    mavlink_msg_file_transfer_protocol_decode(&message, &data);
+	
+    // Make sure we are the target system
+    if (data.target_system != _systemIdQGC) {
+        qDebug() << "Received MAVLINK_MSG_ID_FILE_TRANSFER_PROTOCOL with incorrect target_system:" <<  data.target_system << "expected:" << _systemIdQGC;
+        return;
+    }
+    
+    Request* request = (Request*)&data.payload[0];
+
+    uint16_t incomingSeqNumber = request->hdr.seqNumber;
+    
+    // Make sure we have a good sequence number
+    uint16_t expectedSeqNumber = _lastOutgoingRequest.hdr.seqNumber + 1;
+
+    // ignore old/reordered packets (handle wrap-around properly)
+    if ((uint16_t)((expectedSeqNumber - 1) - incomingSeqNumber) < (std::numeric_limits<uint16_t>::max()/2)) {
+        qDebug() << "Received old packet: expected seq:" << expectedSeqNumber << "got:" << incomingSeqNumber;
+        return;
+    }
+
+    _clearAckTimeout();
+    
+    qCDebug(MAVLinkFTPManagerLog) << "receiveMessage" << request->hdr.opcode;
+	
+    if (incomingSeqNumber != expectedSeqNumber) {
+        bool doAbort = true;
+        switch (_currentOperation) {
+            case kCOBurst: // burst download drops are handled in _downloadAckResponse()
+                doAbort = false;
+                break;
+            case kCORead:
+                _closeDownloadSession(false /* failure */);
+                break;
+            
+            case kCOWrite:
+                _closeUploadSession(false /* failure */);
+                break;
+                
+            case kCOOpenRead:
+            case kCOOpenBurst:
+            case kCOCreate:
+                // We could have an open session hanging around
+                _currentOperation = kCOIdle;
+                _sendResetCommand();
+                break;
+                
+            default:
+                // Don't need to do anything special
+                _currentOperation = kCOIdle;
+                break;
+        }
+        
+        if (doAbort) {
+            _emitErrorMessage(tr("Bad sequence number on received message: expected(%1) received(%2)").arg(expectedSeqNumber).arg(incomingSeqNumber));
+            return;
+        }
+    }
+    
+    // Move past the incoming sequence number for next request
+    _lastOutgoingRequest.hdr.seqNumber = incomingSeqNumber;
+
+    if (request->hdr.opcode == kRspAck) {
+        switch (request->hdr.req_opcode) {
+			case kCmdListDirectory:
+				_listAckResponse(request);
+				break;
+				
+			case kCmdOpenFileRO:
+            case kCmdOpenFileWO:
+				_openAckResponse(request);
+				break;
+				
+			case kCmdReadFile:
+				_downloadAckResponse(request, true /* read file */);
+				break;
+				
+			case kCmdBurstReadFile:
+				_downloadAckResponse(request, false /* stream file */);
+				break;
+				
+            case kCmdCreateFile:
+                _createAckResponse(request);
+                break;
+                
+            case kCmdWriteFile:
+                _writeAckResponse(request);
+                break;
+                
+			default:
+				// Ack back from operation which does not require additional work
+				_currentOperation = kCOIdle;
+				break;
+		}
+    } else if (request->hdr.opcode == kRspNak) {
+        uint8_t errorCode = request->data[0];
+
+        // Nak's normally have 1 byte of data for error code, except for kErrFailErrno which has additional byte for errno
+        Q_ASSERT((errorCode == kErrFailErrno && request->hdr.size == 2) || request->hdr.size == 1);
+        
+        _currentOperation = kCOIdle;
+
+        if (request->hdr.req_opcode == kCmdListDirectory && errorCode == kErrEOF) {
+            // This is not an error, just the end of the list loop
+            emit commandComplete();
+            return;
+        } else if ((request->hdr.req_opcode == kCmdReadFile || request->hdr.req_opcode == kCmdBurstReadFile) && errorCode == kErrEOF) {
+            // This is not an error, just the end of the download loop
+            _closeDownloadSession(true /* success */);
+            return;
+        } else if (request->hdr.req_opcode == kCmdCreateFile) {
+            _emitErrorMessage(tr("Nak received creating file, error: %1").arg(errorString(request->data[0])));
+            return;
+        } else if (request->hdr.req_opcode == kCmdCreateDirectory) {
+            _emitErrorMessage(tr("Nak received creating directory, error: %1").arg(errorString(request->data[0])));
+            return;
+        } else {
+            // Generic Nak handling
+            if (request->hdr.req_opcode == kCmdReadFile || request->hdr.req_opcode == kCmdBurstReadFile) {
+                // Nak error during download loop, download failed
+                _closeDownloadSession(false /* failure */);
+            } else if (request->hdr.req_opcode == kCmdWriteFile) {
+                // Nak error during upload loop, upload failed
+                _closeUploadSession(false /* failure */);
+            }
+            _emitErrorMessage(tr("Nak received, error: %1").arg(errorString(request->data[0])));
+        }
+    } else {
+        // Note that we don't change our operation state. If something goes wrong beyond this, the operation
+        // will time out.
+        _emitErrorMessage(tr("Unknown opcode returned from server: %1").arg(request->hdr.opcode));
+    }
+}
+
+void MAVLinkFTPManager::listDirectory(const QString& dirPath)
+{
+    if (_currentOperation != kCOIdle) {
+        _emitErrorMessage(tr("Command not sent. Waiting for previous command to complete."));
+        return;
+    }
+
+    _dedicatedLink = _vehicle->priorityLink();
+    if (!_dedicatedLink) {
+        _emitErrorMessage(tr("Command not sent. No Vehicle links."));
+        return;
+    }
+
+    // initialise the lister
+    _listPath = dirPath;
+    _listOffset = 0;
+    _currentOperation = kCOList;
+
+    // and send the initial request
+    _sendListCommand();
+}
+
+void MAVLinkFTPManager::_fillRequestWithString(Request* request, const QString& str)
+{
+    strncpy((char *)&request->data[0], str.toStdString().c_str(), sizeof(request->data));
+    request->hdr.size = static_cast<uint8_t>(strnlen((const char *)&request->data[0], sizeof(request->data)));
+}
+
+void MAVLinkFTPManager::_sendListCommand(void)
+{
+    Request request;
+
+    request.hdr.session = 0;
+    request.hdr.opcode = kCmdListDirectory;
+    request.hdr.offset = _listOffset;
+    request.hdr.size = 0;
+
+    _fillRequestWithString(&request, _listPath);
+
+    qCDebug(MAVLinkFTPManagerLog) << "listDirectory: path:" << _listPath << "offset:" <<  _listOffset;
+    
+    _sendRequest(&request);
+}
+
+void MAVLinkFTPManager::downloadPath(const QString& vehicleFilePath, const QDir& downloadDir)
+{
+    if (_currentOperation != kCOIdle) {
+        _emitErrorMessage(tr("Command not sent. Waiting for previous command to complete."));
+        return;
+    }
+
+    _dedicatedLink = _vehicle->priorityLink();
+    if (!_dedicatedLink) {
+        _emitErrorMessage(tr("Command not sent. No Vehicle links."));
+        return;
+    }
+    
+    qCDebug(MAVLinkFTPManagerLog) << "downloadPath vehicleFilePath:" << vehicleFilePath << "to:" << downloadDir;
+    _downloadWorker(vehicleFilePath, downloadDir, true /* read file */);
+}
+
+void MAVLinkFTPManager::streamPath(const QString& from, const QDir& downloadDir)
+{
+    if (_currentOperation != kCOIdle) {
+        _emitErrorMessage(tr("Command not sent. Waiting for previous command to complete."));
+        return;
+    }
+
+    _dedicatedLink = _vehicle->priorityLink();
+    if (!_dedicatedLink) {
+        _emitErrorMessage(tr("Command not sent. No Vehicle links."));
+        return;
+    }
+    
+    qCDebug(MAVLinkFTPManagerLog) << "streamPath from:" << from << "to:" << downloadDir;
+	_downloadWorker(from, downloadDir, false /* stream file */);
+}
+
+void MAVLinkFTPManager::_downloadWorker(const QString& vehicleFilePath, const QDir& downloadDir, bool readFile)
+{
+    if (vehicleFilePath.isEmpty()) {
+		return;
+	}
+	
+	_readFileDownloadDir.setPath(downloadDir.absolutePath());
+	
+	// We need to strip off the file name from the fully qualified path. We can't use the usual QDir
+	// routines because this path does not exist locally.
+	int i;
+    for (i=vehicleFilePath.size()-1; i>=0; i--) {
+        if (vehicleFilePath[i] == '/') {
+			break;
+		}
+	}
+	i++; // move past slash
+    _readFileDownloadFilename = vehicleFilePath.right(vehicleFilePath.size() - i);
+	
+	_currentOperation = readFile ? kCOOpenRead : kCOOpenBurst;
+	
+	Request request;
+	request.hdr.session = 0;
+	request.hdr.opcode = kCmdOpenFileRO;
+	request.hdr.offset = 0;
+	request.hdr.size = 0;
+    _fillRequestWithString(&request, vehicleFilePath);
+	_sendRequest(&request);
+}
+
+/// @brief Uploads the specified file.
+///     @param toPath File in UAS to upload to, fully qualified path
+///     @param uploadFile Local file to upload from
+void MAVLinkFTPManager::uploadPath(const QString& toPath, const QFileInfo& uploadFile)
+{
+    if(_currentOperation != kCOIdle){
+        _emitErrorMessage(tr("UAS File manager busy. Try again later"));
+        return;
+    }
+
+    _dedicatedLink = _vehicle->priorityLink();
+    if (!_dedicatedLink) {
+        _emitErrorMessage(tr("Command not sent. No Vehicle links."));
+        return;
+    }
+
+    if (toPath.isEmpty()) {
+        return;
+    }
+
+    if (!uploadFile.isReadable()){
+        _emitErrorMessage(tr("File (%1) is not readable for upload").arg(uploadFile.path()));
+        return;
+    }
+
+    QFile file(uploadFile.absoluteFilePath());
+    if (!file.open(QIODevice::ReadOnly)) {
+            _emitErrorMessage(tr("Unable to open local file for upload (%1)").arg(uploadFile.absoluteFilePath()));
+            return;
+        }
+
+    _writeFileAccumulator = file.readAll();
+    _writeFileSize = _writeFileAccumulator.size();
+
+    file.close();
+
+    if (_writeFileAccumulator.size() == 0) {
+        _emitErrorMessage(tr("Unable to read data from local file (%1)").arg(uploadFile.absoluteFilePath()));
+        return;
+    }
+
+    _currentOperation = kCOCreate;
+
+    Request request;
+    request.hdr.session = 0;
+    request.hdr.opcode = kCmdCreateFile;
+    request.hdr.offset = 0;
+    request.hdr.size = 0;
+    _fillRequestWithString(&request, toPath + "/" + uploadFile.fileName());
+    _sendRequest(&request);
+}
+
+void MAVLinkFTPManager::createDirectory(const QString& directory)
+{
+    if(_currentOperation != kCOIdle){
+        _emitErrorMessage(tr("UAS File manager busy. Try again later"));
+        return;
+    }
+
+    _currentOperation = kCOCreateDir;
+
+    Request request;
+    request.hdr.session = 0;
+    request.hdr.opcode = kCmdCreateDirectory;
+    request.hdr.offset = 0;
+    request.hdr.size = 0;
+    _fillRequestWithString(&request, directory);
+    _sendRequest(&request);
+}
+
+QString MAVLinkFTPManager::errorString(uint8_t errorCode)
+{
+    switch(errorCode) {
+        case kErrNone:
+            return QString("no error");
+        case kErrFail:
+            return QString("unknown error");
+        case kErrEOF:
+            return QString("read beyond end of file");
+        case kErrUnknownCommand:
+            return QString("unknown command");
+        case kErrFailErrno:
+            return QString("command failed");
+        case kErrInvalidDataSize:
+            return QString("invalid data size");
+        case kErrInvalidSession:
+            return QString("invalid session");
+        case kErrNoSessionsAvailable:
+            return QString("no sessions available");
+        case kErrFailFileExists:
+            return QString("File already exists on target");
+        case kErrFailFileProtected:
+            return QString("File is write protected");
+        default:
+            return QString("unknown error code");
+    }
+}
+
+/// @brief Sends a command which only requires an opcode and no additional data
+///     @param opcode Opcode to send
+///     @param newOpState State to put state machine into
+/// @return TRUE: command sent, FALSE: command not sent, waiting for previous command to finish
+bool MAVLinkFTPManager::_sendOpcodeOnlyCmd(uint8_t opcode, OperationState newOpState)
+{
+    if (_currentOperation != kCOIdle) {
+        // Can't have multiple commands in play at the same time
+        return false;
+    }
+
+    Request request;
+    request.hdr.session = 0;
+    request.hdr.opcode = opcode;
+    request.hdr.offset = 0;
+    request.hdr.size = 0;
+
+    _currentOperation = newOpState;
+
+    _sendRequest(&request);
+
+    return true;
+}
+
+/// @brief Starts the ack timeout timer
+void MAVLinkFTPManager::_setupAckTimeout(void)
+{
+    qCDebug(MAVLinkFTPManagerLog) << "_setupAckTimeout";
+
+    Q_ASSERT(!_ackTimer.isActive());
+
+    _ackNumTries = 0;
+    _ackTimer.setSingleShot(false);
+    _ackTimer.start(ackTimerTimeoutMsecs);
+}
+
+/// @brief Clears the ack timeout timer
+void MAVLinkFTPManager::_clearAckTimeout(void)
+{
+    qCDebug(MAVLinkFTPManagerLog) << "_clearAckTimeout";
+    _ackTimer.stop();
+}
+
+/// @brief Called when ack timeout timer fires
+void MAVLinkFTPManager::_ackTimeout(void)
+{
+    qCDebug(MAVLinkFTPManagerLog) << "_ackTimeout";
+    
+    if (++_ackNumTries <= ackTimerMaxRetries) {
+        qCDebug(MAVLinkFTPManagerLog) << "ack timeout - retrying";
+        if (_currentOperation == kCOBurst) {
+            // for burst downloads try to initiate a new burst
+            Request request;
+            request.hdr.session = _activeSession;
+            request.hdr.opcode = kCmdBurstReadFile;
+            request.hdr.offset = _downloadOffset;
+            request.hdr.size = 0;
+            request.hdr.seqNumber = ++_lastOutgoingRequest.hdr.seqNumber;
+
+            _sendRequestNoAck(&request);
+        } else {
+            _sendRequestNoAck(&_lastOutgoingRequest);
+        }
+        return;
+    }
+
+    _clearAckTimeout();
+
+    // Make sure to set _currentOperation state before emitting error message. Code may respond
+    // to error message signal by sending another command, which will fail if state is not back
+    // to idle. FileView UI works this way with the List command.
+
+    switch (_currentOperation) {
+        case kCORead:
+        case kCOBurst:
+            _closeDownloadSession(false /* failure */);
+            _emitErrorMessage(tr("Timeout waiting for ack: Download failed"));
+            break;
+            
+        case kCOOpenRead:
+        case kCOOpenBurst:
+            _currentOperation = kCOIdle;
+            _emitErrorMessage(tr("Timeout waiting for ack: Download failed"));
+            _sendResetCommand();
+            break;
+            
+        case kCOCreate:
+            _currentOperation = kCOIdle;
+            _emitErrorMessage(tr("Timeout waiting for ack: Upload failed"));
+            _sendResetCommand();
+            break;
+            
+        case kCOWrite:
+            _closeUploadSession(false /* failure */);
+            _emitErrorMessage(tr("Timeout waiting for ack: Upload failed"));
+            break;
+			
+        default:
+        {
+            OperationState currentOperation = _currentOperation;
+            _currentOperation = kCOIdle;
+            _emitErrorMessage(QString("Timeout waiting for ack: Command failed (%1)").arg(currentOperation));
+        }
+            break;
+    }
+}
+
+void MAVLinkFTPManager::_sendResetCommand(void)
+{
+    Request request;
+    request.hdr.opcode = kCmdResetSessions;
+    request.hdr.size = 0;
+    _sendRequest(&request);
+}
+
+void MAVLinkFTPManager::_emitErrorMessage(const QString& msg)
+{
+    qCDebug(MAVLinkFTPManagerLog) << "Error:" << msg;
+    emit commandError(msg);
+}
+
+void MAVLinkFTPManager::_emitListEntry(const QString& entry)
+{
+    qCDebug(MAVLinkFTPManagerLog) << "_emitListEntry" << entry;
+    emit listEntry(entry);
+}
+
+/// @brief Sends the specified Request out to the UAS.
+void MAVLinkFTPManager::_sendRequest(Request* request)
+{
+
+    _setupAckTimeout();
+    
+    request->hdr.seqNumber = ++_lastOutgoingRequest.hdr.seqNumber;
+    // store the current request
+    if (request->hdr.size <= sizeof(request->data)) {
+        memcpy(&_lastOutgoingRequest, request, sizeof(RequestHeader) + request->hdr.size);
+    } else {
+        qCCritical(MAVLinkFTPManagerLog) << "request length too long:" << request->hdr.size;
+    }
+    
+    qCDebug(MAVLinkFTPManagerLog) << "_sendRequest opcode:" << request->hdr.opcode << "seqNumber:" << request->hdr.seqNumber;
+    
+    if (_systemIdQGC == 0) {
+        _systemIdQGC = qgcApp()->toolbox()->mavlinkProtocol()->getSystemId();
+    }
+    _sendRequestNoAck(request);
+}
+
+/// @brief Sends the specified Request out to the UAS, without ack timeout handling
+void MAVLinkFTPManager::_sendRequestNoAck(Request* request)
+{
+    mavlink_message_t message;
+
+    // Unit testing code can end up here without _dedicateLink set since it tests inidividual commands.
+    LinkInterface* link;
+    if (_dedicatedLink) {
+        link = _dedicatedLink;
+    } else {
+        link = _vehicle->priorityLink();
+    }
+    
+    mavlink_msg_file_transfer_protocol_pack_chan(_systemIdQGC,       // QGC System ID
+                                                 0,                  // QGC Component ID
+                                                 link->mavlinkChannel(),
+                                                 &message,           // Mavlink Message to pack into
+                                                 0,                  // Target network
+                                                 _systemIdServer,    // Target system
+                                                 0,                  // Target component
+                                                 (uint8_t*)request); // Payload
+    
+    _vehicle->sendMessageOnLinkThreadSafe(link, message);
+}

src/Vehicle/MAVLinkFTPManager.h

+/****************************************************************************
+ *
+ *   (c) 2009-2018 QGROUNDCONTROL PROJECT <http://www.qgroundcontrol.org>
+ *
+ * QGroundControl is licensed according to the terms in the file
+ * COPYING.md in the root of the source code directory.
+ *
+ ****************************************************************************/
+
+
+#pragma once
+
+#include <QObject>
+#include <QDir>
+#include <QTimer>
+#include <QQueue>
+
+#include "UASInterface.h"
+#include "QGCLoggingCategory.h"
+
+#ifdef __GNUC__
+#define PACKED_STRUCT( __Declaration__ ) __Declaration__ __attribute__((packed))
+#else
+#define PACKED_STRUCT( __Declaration__ ) __pragma( pack(push, 1) ) __Declaration__ __pragma( pack(pop) )
+#endif
+
+
+Q_DECLARE_LOGGING_CATEGORY(MAVLinkFTPManagerLog)
+
+class Vehicle;
+
+class MAVLinkFTPManager : public QObject
+{
+    Q_OBJECT
+
+public:
+    MAVLinkFTPManager(Vehicle* vehicle);
+
+    /// These methods are only used for testing purposes.
+    bool _sendCmdTestAck(void) { return _sendOpcodeOnlyCmd(kCmdNone, kCOAck); };
+    bool _sendCmdTestNoAck(void) { return _sendOpcodeOnlyCmd(kCmdTestNoAck, kCOAck); };
+
+    /// Timeout in msecs to wait for an Ack time come back. This is public so we can write unit tests which wait long enough
+    /// for the MAVLinkFTPManager to timeout.
+    static const int ackTimerTimeoutMsecs = 50;
+
+    static const int ackTimerMaxRetries = 6;
+
+    /// Downloads the specified file.
+    ///     @param vehicleFilePath File to download from UAS, fully qualified path
+    ///     @param downloadDir Local directory to download file to
+    void downloadPath(const QString& vehicleFilePath, const QDir& downloadDir);
+
+    /// Stream downloads the specified file.
+    ///     @param from File to download from UAS, fully qualified path
+    ///     @param downloadDir Local directory to download file to
+    void streamPath(const QString& from, const QDir& downloadDir);
+
+    /// Lists the specified directory. Emits listEntry signal for each entry, followed by listComplete signal.
+    ///		@param dirPath Fully qualified path to list
+    void listDirectory(const QString& dirPath);
+
+    /// Upload the specified file to the specified location
+    void uploadPath(const QString& toPath, const QFileInfo& uploadFile);
+
+    /// Create a remote directory
+    void createDirectory(const QString& directory);
+
+signals:
+    // Signals associated with the listDirectory method
+
+    /// Signalled to indicate a new directory entry was received.
+    void listEntry(const QString& entry);
+
+    // Signals associated with all commands
+
+    /// Signalled after a command has completed
+    void commandComplete(void);
+
+    /// Signalled when an error occurs during a command. In this case a commandComplete signal will
+    /// not be sent.
+    void commandError(const QString& msg);
+
+    /// Signalled during a lengthy command to show progress
+    ///     @param value Amount of progress: 0.0 = none, 1.0 = complete
+    void commandProgress(int value);
+
+public slots:
+    void receiveMessage(mavlink_message_t message);
+
+private slots:
+    void _ackTimeout(void);
+
+private:
+    /// @brief This is the fixed length portion of the protocol data.
+    /// This needs to be packed, because it's typecasted from mavlink_file_transfer_protocol_t.payload, which starts
+    /// at a 3 byte offset, causing an unaligned access to seq_number and offset
+    PACKED_STRUCT(
+            typedef struct _RequestHeader
+    {
+                uint16_t    seqNumber;      ///< sequence number for message
+                uint8_t     session;        ///< Session id for read and write commands
+                uint8_t     opcode;         ///< Command opcode
+                uint8_t     size;           ///< Size of data
+                uint8_t     req_opcode;     ///< Request opcode returned in kRspAck, kRspNak message
+                uint8_t     burstComplete;  ///< Only used if req_opcode=kCmdBurstReadFile - 1: set of burst packets complete, 0: More burst packets coming.
+                uint8_t     padding;        ///< 32 bit aligment padding
+                uint32_t    offset;         ///< Offsets for List and Read commands
+            }) RequestHeader;
+
+    PACKED_STRUCT(
+            typedef struct _Request
+    {
+                RequestHeader hdr;
+
+                // We use a union here instead of just casting (uint32_t)&payload[0] to not break strict aliasing rules
+                union {
+                    // The entire Request must fit into the payload member of the mavlink_file_transfer_protocol_t structure. We use as many leftover bytes
+                    // after we use up space for the RequestHeader for the data portion of the Request.
+                    uint8_t data[sizeof(((mavlink_file_transfer_protocol_t*)0)->payload) - sizeof(RequestHeader)];
+
+                    // File length returned by Open command
+                    uint32_t openFileLength;
+
+                    // Length of file chunk written by write command
+                    uint32_t writeFileLength;
+                };
+            }) Request;
+
+    enum Opcode
+    {
+        kCmdNone,				///< ignored, always acked
+        kCmdTerminateSession,	///< Terminates open Read session
+        kCmdResetSessions,		///< Terminates all open Read sessions
+        kCmdListDirectory,		///< List files in <path> from <offset>
+        kCmdOpenFileRO,			///< Opens file at <path> for reading, returns <session>
+        kCmdReadFile,			///< Reads <size> bytes from <offset> in <session>
+        kCmdCreateFile,			///< Creates file at <path> for writing, returns <session>
+        kCmdWriteFile,			///< Writes <size> bytes to <offset> in <session>
+        kCmdRemoveFile,			///< Remove file at <path>
+        kCmdCreateDirectory,	///< Creates directory at <path>
+        kCmdRemoveDirectory,	///< Removes Directory at <path>, must be empty
+        kCmdOpenFileWO,			///< Opens file at <path> for writing, returns <session>
+        kCmdTruncateFile,		///< Truncate file at <path> to <offset> length
+        kCmdRename,				///< Rename <path1> to <path2>
+        kCmdCalcFileCRC32,		///< Calculate CRC32 for file at <path>
+        kCmdBurstReadFile,      ///< Burst download session file
+
+        kRspAck = 128,          ///< Ack response
+        kRspNak,                ///< Nak response
+
+        // Used for testing only, not part of protocol
+        kCmdTestNoAck,          ///< ignored, ack not sent back, should timeout waiting for ack
+    };
+
+    /// @brief Error codes returned in Nak response PayloadHeader.data[0].
+    enum ErrorCode
+    {
+        kErrNone,
+        kErrFail,                   ///< Unknown failure
+        kErrFailErrno,              ///< errno sent back in PayloadHeader.data[1]
+        kErrInvalidDataSize,		///< PayloadHeader.size is invalid
+        kErrInvalidSession,         ///< Session is not currently open
+        kErrNoSessionsAvailable,	///< All available Sessions in use
+        kErrEOF,                    ///< Offset past end of file for List and Read commands
+        kErrUnknownCommand,          ///< Unknown command opcode
+        kErrFailFileExists,         ///< File exists already
+        kErrFailFileProtected       ///< File is write protected
+    };
+
+    enum OperationState
+    {
+        kCOIdle,		// not doing anything
+        kCOAck,			// waiting for an Ack
+        kCOList,		// waiting for List response
+        kCOOpenRead,    // waiting for Open response followed by Read download
+        kCOOpenBurst,   // waiting for Open response, followed by Burst download
+        kCORead,		// waiting for Read response
+        kCOBurst,		// waiting for Burst response
+        kCOWrite,       // waiting for Write response
+        kCOCreate,      // waiting for Create response
+        kCOCreateDir,   // waiting for Create Directory response
+    };
+
+    bool _sendOpcodeOnlyCmd(uint8_t opcode, OperationState newOpState);
+    void _setupAckTimeout(void);
+    void _clearAckTimeout(void);
+    void _emitErrorMessage(const QString& msg);
+    void _emitListEntry(const QString& entry);
+    void _sendRequest(Request* request);
+    void _sendRequestNoAck(Request* request);
+    void _fillRequestWithString(Request* request, const QString& str);
+    void _openAckResponse(Request* openAck);
+    void _downloadAckResponse(Request* readAck, bool readFile);
+    void _listAckResponse(Request* listAck);
+    void _createAckResponse(Request* createAck);
+    void _writeAckResponse(Request* writeAck);
+    void _writeFileDatablock(void);
+    void _sendListCommand(void);
+    void _sendResetCommand(void);
+    void _closeDownloadSession(bool success);
+    void _closeUploadSession(bool success);
+    void _downloadWorker(const QString& vehicleFilePath, const QDir& downloadDir, bool readFile);
+    void _requestMissingData();
+
+    static QString errorString(uint8_t errorCode);
+
+    OperationState  _currentOperation = kCOIdle;              ///< Current operation of state machine
+    QTimer          _ackTimer;                      ///< Used to signal a timeout waiting for an ack
+    int             _ackNumTries = 0;                   ///< current number of tries
+
+    Vehicle*        _vehicle = nullptr;
+    LinkInterface*  _dedicatedLink = nullptr; ///< Link to use for communication
+
+    Request  _lastOutgoingRequest; ///< contains the last outgoing packet
+
+    unsigned    _listOffset;    ///< offset for the current List operation
+    QString     _listPath;      ///< path for the current List operation
+
+    uint8_t     _activeSession = 0;             ///< currently active session, 0 for none
+
+    uint32_t    _readOffset;                ///< current read offset
+
+    uint32_t    _writeOffset;               ///< current write offset
+    uint32_t    _writeSize;                 ///< current write data size
+    uint32_t    _writeFileSize;             ///< Size of file being uploaded
+    QByteArray  _writeFileAccumulator;      ///< Holds file being uploaded
+
+    struct MissingData {
+        uint32_t offset;
+        uint32_t size;
+    };
+    uint32_t    _downloadOffset;            ///< current download offset
+    uint32_t    _missingDownloadedBytes = 0;    ///< number of missing bytes for burst download
+    QQueue<MissingData> _missingData;       ///< missing chunks of downloaded file (for burst downloads)
+    bool        _downloadingMissingParts = false;   ///< true if we are currently downloading missing parts
+    QByteArray  _readFileAccumulator;       ///< Holds file being downloaded
+    QDir        _readFileDownloadDir;       ///< Directory to download file to
+    QString     _readFileDownloadFilename;  ///< Filename (no path) for download file
+    uint32_t    _downloadFileSize;          ///< Size of file being downloaded
+
+    uint8_t     _systemIdQGC = 0;               ///< System ID for QGC
+    uint8_t     _systemIdServer = 0;            ///< System ID for server
+
+    // We give MockLinkFileServer friend access so that it can use the data structures and opcodes
+    // to build a mock mavlink file server for testing.
+    friend class MockLinkFileServer;
+};
+