Merged master

8 files changed, 831 insertions, 103 deletions

diff --git a/src/modules/mavlink/mavlink_ftp.cpp b/src/modules/mavlink/mavlink_ftp.cpp
new file mode 100644
index 000000000..f1436efb8
--- /dev/null
+++ b/src/modules/mavlink/mavlink_ftp.cpp
@@ -0,0 +1,415 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2014 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include <crc32.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <fcntl.h>
+
+#include "mavlink_ftp.h"
+
+MavlinkFTP *MavlinkFTP::_server;
+
+MavlinkFTP *
+MavlinkFTP::getServer()
+{
+	// XXX this really cries out for some locking...
+	if (_server == nullptr) {
+		_server = new MavlinkFTP;
+	}
+	return _server;
+}
+
+MavlinkFTP::MavlinkFTP()
+{
+	// initialise the request freelist
+	dq_init(&_workFree);
+	sem_init(&_lock, 0, 1);
+    
+    // initialize session list
+    for (size_t i=0; i<kMaxSession; i++) {
+        _session_fds[i] = -1;
+    }
+
+	// drop work entries onto the free list
+	for (unsigned i = 0; i < kRequestQueueSize; i++) {
+		_qFree(&_workBufs[i]);
+	}
+
+}
+
+void
+MavlinkFTP::handle_message(Mavlink* mavlink, mavlink_message_t *msg)
+{
+	// get a free request
+	auto req = _dqFree();
+
+	// if we couldn't get a request slot, just drop it
+	if (req != nullptr) {
+
+		// decode the request
+		if (req->decode(mavlink, msg)) {
+
+			// and queue it for the worker
+			work_queue(LPWORK, &req->work, &MavlinkFTP::_workerTrampoline, req, 0);
+		} else {
+			_qFree(req);
+		}
+	}
+}
+
+void
+MavlinkFTP::_workerTrampoline(void *arg)
+{
+	auto req = reinterpret_cast<Request *>(arg);
+	auto server = MavlinkFTP::getServer();
+
+	// call the server worker with the work item
+	server->_worker(req);
+}
+
+void
+MavlinkFTP::_worker(Request *req)
+{
+	auto hdr = req->header();
+	ErrorCode errorCode = kErrNone;
+	uint32_t messageCRC;
+
+	// basic sanity checks; must validate length before use
+	if ((hdr->magic != kProtocolMagic) || (hdr->size > kMaxDataLength)) {
+		errorCode = kErrNoRequest;
+		goto out;
+	}
+
+	// check request CRC to make sure this is one of ours
+	messageCRC = hdr->crc32;
+	hdr->crc32 = 0;
+	if (crc32(req->rawData(), req->dataSize()) != messageCRC) {
+		errorCode = kErrNoRequest;
+		goto out;
+		printf("ftp: bad crc\n");
+	}
+
+	printf("ftp: channel %u opc %u size %u offset %u\n", req->channel(), hdr->opcode, hdr->size, hdr->offset);
+
+	switch (hdr->opcode) {
+	case kCmdNone:
+		break;
+
+	case kCmdTerminate:
+        errorCode = _workTerminate(req);
+		break;
+
+	case kCmdReset:
+		errorCode = _workReset();
+		break;
+
+	case kCmdList:
+		errorCode = _workList(req);
+		break;
+
+	case kCmdOpen:
+		errorCode = _workOpen(req, false);
+		break;
+
+	case kCmdCreate:
+		errorCode = _workOpen(req, true);
+		break;
+
+	case kCmdRead:
+		errorCode = _workRead(req);
+		break;
+
+	case kCmdWrite:
+		errorCode = _workWrite(req);
+		break;
+
+	case kCmdRemove:
+		errorCode = _workRemove(req);
+		break;
+
+	default:
+		errorCode = kErrNoRequest;
+		break;	
+	}
+
+out:
+	// handle success vs. error
+	if (errorCode == kErrNone) {
+		hdr->opcode = kRspAck;
+		printf("FTP: ack\n");
+	} else {
+		printf("FTP: nak %u\n", errorCode);
+		hdr->opcode = kRspNak;
+		hdr->size = 1;
+		hdr->data[0] = errorCode;
+	}
+
+	// respond to the request
+	_reply(req);
+
+	// free the request buffer back to the freelist
+	_qFree(req);
+}
+
+void
+MavlinkFTP::_reply(Request *req)
+{
+	auto hdr = req->header();
+
+	// message is assumed to be already constructed in the request buffer, so generate the CRC
+	hdr->crc32 = 0;
+	hdr->crc32 = crc32(req->rawData(), req->dataSize());
+
+	// then pack and send the reply back to the request source
+	req->reply();
+}
+
+MavlinkFTP::ErrorCode
+MavlinkFTP::_workList(Request *req)
+{
+	auto hdr = req->header();
+	DIR *dp = opendir(req->dataAsCString());
+
+	if (dp == nullptr) {
+		printf("FTP: can't open path '%s'\n", req->dataAsCString());
+		return kErrNotDir;
+	}
+
+	ErrorCode errorCode = kErrNone;
+	struct dirent entry, *result = nullptr;
+	unsigned offset = 0;
+
+	// move to the requested offset
+	seekdir(dp, hdr->offset);
+
+	for (;;) {
+		// read the directory entry
+		if (readdir_r(dp, &entry, &result)) {
+			errorCode = kErrIO;
+			break;
+		}
+
+		// no more entries?
+		if (result == nullptr) {
+            if (hdr->offset != 0 && offset == 0) {
+                // User is requesting subsequent dir entries but there were none. This means the user asked
+                // to seek past EOF.
+                errorCode = kErrEOF;
+            }
+            // Otherwise we are just at the last directory entry, so we leave the errorCode at kErrorNone to signal that
+			break;
+		}
+
+		// name too big to fit?
+		if ((strlen(entry.d_name) + offset + 2) > kMaxDataLength) {
+			break;
+		}
+
+		// store the type marker
+		switch (entry.d_type) {
+		case DTYPE_FILE:
+			hdr->data[offset++] = kDirentFile;
+			break;
+		case DTYPE_DIRECTORY:
+			hdr->data[offset++] = kDirentDir;
+			break;
+		default:
+			hdr->data[offset++] = kDirentUnknown;
+			break;
+		}
+
+		// copy the name, which we know will fit
+		strcpy((char *)&hdr->data[offset], entry.d_name);
+		offset += strlen(entry.d_name) + 1;
+		printf("FTP: list %s\n", entry.d_name);
+	}
+
+	closedir(dp);
+	hdr->size = offset;
+
+	return errorCode;
+}
+
+MavlinkFTP::ErrorCode
+MavlinkFTP::_workOpen(Request *req, bool create)
+{
+	auto hdr = req->header();
+    
+    int session_index = _findUnusedSession();
+	if (session_index < 0) {
+		return kErrNoSession;
+	}
+
+	int oflag = create ? (O_CREAT | O_EXCL | O_APPEND) : O_RDONLY;
+    
+    int fd = ::open(req->dataAsCString(), oflag);
+	if (fd < 0) {
+		return create ? kErrPerm : kErrNotFile;
+	}
+    _session_fds[session_index] = fd;
+
+	hdr->session = session_index;
+	hdr->size = 0;
+
+	return kErrNone;
+}
+
+MavlinkFTP::ErrorCode
+MavlinkFTP::_workRead(Request *req)
+{
+	auto hdr = req->header();
+
+    int session_index = hdr->session;
+    
+    if (!_validSession(session_index)) {
+		return kErrNoSession;
+    }
+    
+    // Seek to the specified position
+    printf("Seek %d\n", hdr->offset);
+	if (lseek(_session_fds[session_index], hdr->offset, SEEK_SET) < 0) {
+        // Unable to see to the specified location
+		return kErrEOF;
+	}
+    
+	int bytes_read = ::read(_session_fds[session_index], &hdr->data[0], kMaxDataLength);
+	if (bytes_read < 0) {
+        // Negative return indicates error other than eof
+		return kErrIO;
+	}
+    
+    printf("Read success %d\n", bytes_read);
+	hdr->size = bytes_read;
+    
+	return kErrNone;
+}
+
+MavlinkFTP::ErrorCode
+MavlinkFTP::_workWrite(Request *req)
+{
+#if 0
+    // NYI: Coming soon
+	auto hdr = req->header();
+
+	// look up session
+	auto session = getSession(hdr->session);
+	if (session == nullptr) {
+		return kErrNoSession;
+	}
+
+	// append to file
+	int result = session->append(hdr->offset, &hdr->data[0], hdr->size);
+
+	if (result < 0) {
+		// XXX might also be no space, I/O, etc.
+		return kErrNotAppend;
+	}
+
+	hdr->size = result;
+	return kErrNone;
+#else
+	return kErrPerm;
+#endif
+}
+
+MavlinkFTP::ErrorCode
+MavlinkFTP::_workRemove(Request *req)
+{
+	auto hdr = req->header();
+
+	// for now, send error reply
+	return kErrPerm;
+}
+
+MavlinkFTP::ErrorCode
+MavlinkFTP::_workTerminate(Request *req)
+{
+	auto hdr = req->header();
+    
+    if (!_validSession(hdr->session)) {
+		return kErrNoSession;
+    }
+    
+    ::close(_session_fds[hdr->session]);
+
+    return kErrNone;
+}
+
+MavlinkFTP::ErrorCode
+MavlinkFTP::_workReset(void)
+{
+    for (size_t i=0; i<kMaxSession; i++) {
+        if (_session_fds[i] != -1) {
+            ::close(_session_fds[i]);
+            _session_fds[i] = -1;
+        }
+    }
+    
+    return kErrNone;
+}
+
+bool
+MavlinkFTP::_validSession(unsigned index)
+{
+	if ((index >= kMaxSession) || (_session_fds[index] < 0)) {
+		return false;
+	}
+	return true;
+}
+
+int
+MavlinkFTP::_findUnusedSession(void)
+{
+    for (size_t i=0; i<kMaxSession; i++) {
+        if (_session_fds[i] == -1) {
+            return i;
+        }
+    }
+    
+    return -1;
+}
+
+char *
+MavlinkFTP::Request::dataAsCString()
+{
+	// guarantee nul termination
+	if (header()->size < kMaxDataLength) {
+		requestData()[header()->size] = '\0';
+	} else {
+		requestData()[kMaxDataLength - 1] = '\0';
+	}
+
+	// and return data
+	return (char *)&(header()->data[0]);
+}
diff --git a/src/modules/mavlink/mavlink_ftp.h b/src/modules/mavlink/mavlink_ftp.h
new file mode 100644
index 000000000..8a1b3fbaa
--- /dev/null
+++ b/src/modules/mavlink/mavlink_ftp.h
@@ -0,0 +1,226 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2014 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+/**
+ * @file mavlink_ftp.h
+ *
+ * MAVLink remote file server.
+ *
+ * Messages are wrapped in ENCAPSULATED_DATA messages. Every message includes
+ * a session ID and sequence number.
+ *
+ * A limited number of requests (currently 2) may be outstanding at a time.
+ * Additional messages will be discarded.
+ *
+ * Messages consist of a fixed header, followed by a data area.
+ *
+ */
+ 
+#include <dirent.h>
+#include <queue.h>
+
+#include <nuttx/wqueue.h>
+#include <systemlib/err.h>
+
+#include "mavlink_messages.h"
+
+class MavlinkFTP
+{
+public:
+	MavlinkFTP();
+
+	static MavlinkFTP	*getServer();
+
+	// static interface
+	void			handle_message(Mavlink* mavlink,
+					mavlink_message_t *msg);
+
+private:
+
+	static const unsigned	kRequestQueueSize = 2;
+
+	static MavlinkFTP	*_server;
+
+	struct RequestHeader
+	{
+		uint8_t		magic;
+		uint8_t		session;
+		uint8_t		opcode;
+		uint8_t		size;
+		uint32_t	crc32;
+		uint32_t	offset;
+		uint8_t		data[];
+	};
+
+	enum Opcode : uint8_t
+	{
+		kCmdNone,	// ignored, always acked
+		kCmdTerminate,	// releases sessionID, closes file
+		kCmdReset,	// terminates all sessions
+		kCmdList,	// list files in <path> from <offset>
+		kCmdOpen,	// opens <path> for reading, returns <session>
+		kCmdRead,	// reads <size> bytes from <offset> in <session>
+		kCmdCreate,	// creates <path> for writing, returns <session>
+		kCmdWrite,	// appends <size> bytes at <offset> in <session>
+		kCmdRemove,	// remove file (only if created by server?)
+
+		kRspAck,
+		kRspNak
+	};
+
+	enum ErrorCode : uint8_t
+	{
+		kErrNone,
+		kErrNoRequest,
+		kErrNoSession,
+		kErrSequence,
+		kErrNotDir,
+		kErrNotFile,
+		kErrEOF,
+		kErrNotAppend,
+		kErrTooBig,
+		kErrIO,
+		kErrPerm
+	};
+
+    int _findUnusedSession(void);
+    bool _validSession(unsigned index);
+
+    static const unsigned kMaxSession = 2;
+    int	_session_fds[kMaxSession];
+
+	class Request
+	{
+	public:
+		union {
+			dq_entry_t	entry;
+			work_s		work;
+		};
+
+		bool		decode(Mavlink *mavlink, mavlink_message_t *fromMessage) {
+			if (fromMessage->msgid == MAVLINK_MSG_ID_ENCAPSULATED_DATA) {
+				_mavlink = mavlink;
+				mavlink_msg_encapsulated_data_decode(fromMessage, &_message);
+				return true;
+			}
+			return false;
+		}
+
+		void		reply() {
+
+			// XXX the proper way would be an IOCTL / uORB call, rather than exploiting the
+			// flat memory architecture, as we're operating between threads here.
+			mavlink_message_t msg;
+			msg.checksum = 0;
+			unsigned len = mavlink_msg_encapsulated_data_pack_chan(_mavlink->get_system_id(), _mavlink->get_component_id(),
+				_mavlink->get_channel(), &msg, sequence(), rawData());
+
+            _mavlink->lockMessageBufferMutex();
+            bool fError = _mavlink->message_buffer_write(&msg, len);
+            _mavlink->unlockMessageBufferMutex();
+            
+            if (!fError) {
+				warnx("FTP TX ERR");
+			} else {
+				warnx("wrote: sys: %d, comp: %d, chan: %d, len: %d, checksum: %d",
+					_mavlink->get_system_id(),
+					_mavlink->get_component_id(),
+					_mavlink->get_channel(),
+					len,
+					msg.checksum);
+			}
+		}
+
+		uint8_t		*rawData() { return &_message.data[0]; }
+		RequestHeader 	*header()  { return reinterpret_cast<RequestHeader *>(&_message.data[0]); }
+		uint8_t         *requestData() { return &(header()->data[0]); }
+		unsigned	dataSize() { return header()->size + sizeof(RequestHeader); }
+		uint16_t	sequence() const { return _message.seqnr; }
+		mavlink_channel_t channel() { return _mavlink->get_channel(); }
+
+		char		*dataAsCString();
+
+	private:
+		Mavlink			*_mavlink;
+		mavlink_encapsulated_data_t _message;
+
+	};
+
+	static const uint8_t	kProtocolMagic = 'f';
+	static const char	kDirentFile = 'F';
+	static const char	kDirentDir = 'D';
+	static const char	kDirentUnknown = 'U';
+	static const uint8_t	kMaxDataLength = MAVLINK_MSG_ENCAPSULATED_DATA_FIELD_DATA_LEN - sizeof(RequestHeader);
+
+	/// Request worker; runs on the low-priority work queue to service
+	/// remote requests.
+	///
+	static void		_workerTrampoline(void *arg);
+	void			_worker(Request *req);
+
+	/// Reply to a request (XXX should be a Request method)
+	///
+	void			_reply(Request *req);
+
+	ErrorCode		_workList(Request *req);
+	ErrorCode		_workOpen(Request *req, bool create);
+	ErrorCode		_workRead(Request *req);
+	ErrorCode		_workWrite(Request *req);
+	ErrorCode		_workRemove(Request *req);
+    ErrorCode       _workTerminate(Request *req);
+    ErrorCode       _workReset();
+
+	// work freelist
+	Request			_workBufs[kRequestQueueSize];
+	dq_queue_t		_workFree;
+	sem_t			_lock;
+
+	void			_qLock() { do {} while (sem_wait(&_lock) != 0); }
+	void			_qUnlock() { sem_post(&_lock); }
+
+	void			_qFree(Request *req) {
+		_qLock();
+		dq_addlast(&req->entry, &_workFree);
+		_qUnlock();
+	}
+
+	Request			*_dqFree() {
+		_qLock();
+		auto req = reinterpret_cast<Request *>(dq_remfirst(&_workFree));
+		_qUnlock();
+		return req;
+	}
+    
+};
diff --git a/src/modules/mavlink/mavlink_main.cpp b/src/modules/mavlink/mavlink_main.cpp
index ee5e7aa3a..9a5e31ef4 100644
--- a/src/modules/mavlink/mavlink_main.cpp
+++ b/src/modules/mavlink/mavlink_main.cpp
@@ -83,6 +83,10 @@
 #include "mavlink_rate_limiter.h"
 #include "mavlink_commands.h"
 
+#ifndef MAVLINK_CRC_EXTRA
+ #error MAVLINK_CRC_EXTRA has to be defined on PX4 systems
+#endif
+
 /* oddly, ERROR is not defined for c++ */
 #ifdef ERROR
 # undef ERROR
@@ -114,6 +118,7 @@ static uint64_t last_write_try_times[6] = {0};
 void
 mavlink_send_uart_bytes(mavlink_channel_t channel, const uint8_t *ch, int length)
 {
+
 	Mavlink *instance;
 
 	switch (channel) {
@@ -231,6 +236,7 @@ Mavlink::Mavlink() :
 	_verbose(false),
 	_forwarding_on(false),
 	_passing_on(false),
+	_ftp_on(false),
 	_uart_fd(-1),
 	_mavlink_param_queue_index(0),
 	_subscribe_to_stream(nullptr),
@@ -468,7 +474,7 @@ Mavlink::get_instance_id()
 	return _instance_id;
 }
 
-mavlink_channel_t
+const mavlink_channel_t
 Mavlink::get_channel()
 {
 	return _channel;
@@ -546,6 +552,16 @@ void Mavlink::mavlink_update_system(void)
 	_use_hil_gps = (bool)use_hil_gps;
 }
 
+int Mavlink::get_system_id()
+{
+	return mavlink_system.sysid;
+}
+
+int Mavlink::get_component_id()
+{
+	return mavlink_system.compid;
+}
+
 int Mavlink::mavlink_open_uart(int baud, const char *uart_name, struct termios *uart_config_original, bool *is_usb)
 {
 	/* process baud rate */
@@ -1640,11 +1656,21 @@ Mavlink::configure_stream_threadsafe(const char *stream_name, const float rate)
 int
 Mavlink::message_buffer_init(int size)
 {
+
 	_message_buffer.size = size;
 	_message_buffer.write_ptr = 0;
 	_message_buffer.read_ptr = 0;
 	_message_buffer.data = (char*)malloc(_message_buffer.size);
-	return (_message_buffer.data == 0) ? ERROR : OK;
+
+	int ret;
+	if (_message_buffer.data == 0) {
+		ret = ERROR;
+		_message_buffer.size = 0;
+	} else {
+		ret = OK;
+	}
+
+	return ret;
 }
 
 void
@@ -1772,7 +1798,7 @@ Mavlink::task_main(int argc, char *argv[])
 	 * set error flag instead */
 	bool err_flag = false;
 
-	while ((ch = getopt(argc, argv, "b:r:d:m:fpvw")) != EOF) {
+	while ((ch = getopt(argc, argv, "b:r:d:m:fpvwx")) != EOF) {
 		switch (ch) {
 		case 'b':
 			_baudrate = strtoul(optarg, NULL, 10);
@@ -1828,6 +1854,10 @@ Mavlink::task_main(int argc, char *argv[])
 			_wait_to_transmit = true;
 			break;
 
+		case 'x':
+			_ftp_on = true;
+			break;
+
 		default:
 			err_flag = true;
 			break;
@@ -1893,9 +1923,12 @@ Mavlink::task_main(int argc, char *argv[])
 	mavlink_logbuffer_init(&_logbuffer, 5);
 
 	/* if we are passing on mavlink messages, we need to prepare a buffer for this instance */
-	if (_passing_on) {
-		/* initialize message buffer if multiplexing is on */
-		if (OK != message_buffer_init(300)) {
+	if (_passing_on || _ftp_on) {
+		/* initialize message buffer if multiplexing is on or its needed for FTP.
+		 * make space for two messages plus off-by-one space as we use the empty element
+		 * marker ring buffer approach.
+		 */
+		if (OK != message_buffer_init(2 * MAVLINK_MAX_PACKET_LEN + 2)) {
 			errx(1, "can't allocate message buffer, exiting");
 		}
 
@@ -2058,32 +2091,50 @@ Mavlink::task_main(int argc, char *argv[])
 			}
 		}
 
-		/* pass messages from other UARTs */
-		if (_passing_on) {
+		/* pass messages from other UARTs or FTP worker */
+		if (_passing_on || _ftp_on) {
 
 			bool is_part;
-			void *read_ptr;
+			uint8_t *read_ptr;
+            uint8_t *write_ptr;
 
-			/* guard get ptr by mutex */
 			pthread_mutex_lock(&_message_buffer_mutex);
-			int available = message_buffer_get_ptr(&read_ptr, &is_part);
+			int available = message_buffer_get_ptr((void**)&read_ptr, &is_part);
 			pthread_mutex_unlock(&_message_buffer_mutex);
 
 			if (available > 0) {
-				/* write first part of buffer */
-				_mavlink_resend_uart(_channel, (const mavlink_message_t*)read_ptr);
-				message_buffer_mark_read(available);
+                // Reconstruct message from buffer
+
+				mavlink_message_t msg;
+                write_ptr = (uint8_t*)&msg;
+
+                // Pull a single message from the buffer
+                int read_count = available;
+                if (read_count > sizeof(mavlink_message_t)) {
+                    read_count = sizeof(mavlink_message_t);
+                }
+                
+                memcpy(write_ptr, read_ptr, read_count);
+                
+                // We hold the mutex until after we complete the second part of the buffer. If we don't
+                // we may end up breaking the empty slot overflow detection semantics when we mark the
+                // possibly partial read below.
+                pthread_mutex_lock(&_message_buffer_mutex);
+                
+				message_buffer_mark_read(read_count);
 
 				/* write second part of buffer if there is some */
-				if (is_part) {
-					/* guard get ptr by mutex */
-					pthread_mutex_lock(&_message_buffer_mutex);
-					available = message_buffer_get_ptr(&read_ptr, &is_part);
-					pthread_mutex_unlock(&_message_buffer_mutex);
-
-					_mavlink_resend_uart(_channel, (const mavlink_message_t*)read_ptr);
+				if (is_part && read_count < sizeof(mavlink_message_t)) {
+                    write_ptr += read_count;
+					available = message_buffer_get_ptr((void**)&read_ptr, &is_part);
+                    read_count = sizeof(mavlink_message_t) - read_count;
+                    memcpy(write_ptr, read_ptr, read_count);
 					message_buffer_mark_read(available);
 				}
+                
+                pthread_mutex_unlock(&_message_buffer_mutex);
+
+                _mavlink_resend_uart(_channel, &msg);
 			}
 		}
 
@@ -2133,7 +2184,7 @@ Mavlink::task_main(int argc, char *argv[])
 	/* close mavlink logging device */
 	close(_mavlink_fd);
 
-	if (_passing_on) {
+	if (_passing_on || _ftp_on) {
 		message_buffer_destroy();
 		pthread_mutex_destroy(&_message_buffer_mutex);
 	}
@@ -2284,7 +2335,7 @@ Mavlink::stream(int argc, char *argv[])
 
 static void usage()
 {
-	warnx("usage: mavlink {start|stop-all|stream} [-d device] [-b baudrate] [-r rate] [-m mode] [-s stream] [-f] [-p] [-v] [-w]");
+	warnx("usage: mavlink {start|stop-all|stream} [-d device] [-b baudrate]\n\t[-r rate][-m mode] [-s stream] [-f] [-p] [-v] [-w] [-x]");
 }
 
 int mavlink_main(int argc, char *argv[])
diff --git a/src/modules/mavlink/mavlink_main.h b/src/modules/mavlink/mavlink_main.h
index f74b7daa7..6777d56c3 100644
--- a/src/modules/mavlink/mavlink_main.h
+++ b/src/modules/mavlink/mavlink_main.h
@@ -123,27 +123,41 @@ public:
 	/**
 	 * Display the mavlink status.
 	 */
-	void		status();
+	void			status();
 
-	static int stream(int argc, char *argv[]);
+	static int		stream(int argc, char *argv[]);
 
-	static int	instance_count();
+	static int		instance_count();
 
-	static Mavlink *new_instance();
+	static Mavlink		*new_instance();
 
-	static Mavlink *get_instance(unsigned instance);
+	static Mavlink		*get_instance(unsigned instance);
 
-	static Mavlink *get_instance_for_device(const char *device_name);
+	static Mavlink		*get_instance_for_device(const char *device_name);
 
-	static int	destroy_all_instances();
+	static int		destroy_all_instances();
 
-	static bool	instance_exists(const char *device_name, Mavlink *self);
+	static bool		instance_exists(const char *device_name, Mavlink *self);
 
-	static void	forward_message(mavlink_message_t *msg, Mavlink *self);
+	static void		forward_message(mavlink_message_t *msg, Mavlink *self);
 
-	static int get_uart_fd(unsigned index);
+	static int		get_uart_fd(unsigned index);
 
-	int get_uart_fd();
+	int			get_uart_fd();
+
+	/**
+	 * Get the MAVLink system id.
+	 *
+	 * @return		The system ID of this vehicle
+	 */
+	int			get_system_id();
+
+	/**
+	 * Get the MAVLink component id.
+	 *
+	 * @return		The component ID of this vehicle
+	 */
+	int			get_component_id();
 
 	const char *_device_name;
 
@@ -153,30 +167,30 @@ public:
 		MAVLINK_MODE_CAMERA
 	};
 
-	void		set_mode(enum MAVLINK_MODE);
-	enum MAVLINK_MODE		get_mode() { return _mode; }
+	void			set_mode(enum MAVLINK_MODE);
+	enum MAVLINK_MODE	get_mode() { return _mode; }
 
-	bool		get_hil_enabled() { return _hil_enabled; }
+	bool			get_hil_enabled() { return _hil_enabled; }
 
-	bool		get_use_hil_gps() { return _use_hil_gps; }
+	bool			get_use_hil_gps() { return _use_hil_gps; }
 
-	bool		get_flow_control_enabled() { return _flow_control_enabled; }
+	bool			get_flow_control_enabled() { return _flow_control_enabled; }
 
-	bool		get_forwarding_on() { return _forwarding_on; }
+	bool			get_forwarding_on() { return _forwarding_on; }
 
 	/**
 	 * Handle waypoint related messages.
 	 */
-	void mavlink_wpm_message_handler(const mavlink_message_t *msg);
+	void			mavlink_wpm_message_handler(const mavlink_message_t *msg);
 
-	static int start_helper(int argc, char *argv[]);
+	static int		start_helper(int argc, char *argv[]);
 
 	/**
 	 * Handle parameter related messages.
 	 */
-	void mavlink_pm_message_handler(const mavlink_channel_t chan, const mavlink_message_t *msg);
+	void			mavlink_pm_message_handler(const mavlink_channel_t chan, const mavlink_message_t *msg);
 
-	void get_mavlink_mode_and_state(struct vehicle_status_s *status, struct position_setpoint_triplet_s *pos_sp_triplet, uint8_t *mavlink_state, uint8_t *mavlink_base_mode, uint32_t *mavlink_custom_mode);
+	void			get_mavlink_mode_and_state(struct vehicle_status_s *status, struct position_setpoint_triplet_s *pos_sp_triplet, uint8_t *mavlink_state, uint8_t *mavlink_base_mode, uint32_t *mavlink_custom_mode);
 
 	/**
 	 * Enable / disable Hardware in the Loop simulation mode.
@@ -186,36 +200,41 @@ public:
 	 *			requested change could not be made or was
 	 *			redundant.
 	 */
-	int		set_hil_enabled(bool hil_enabled);
+	int			set_hil_enabled(bool hil_enabled);
 
-	MavlinkOrbSubscription *add_orb_subscription(const orb_id_t topic);
+	MavlinkOrbSubscription	*add_orb_subscription(const orb_id_t topic);
 
-	int get_instance_id();
+	int			get_instance_id();
 
 	/**
 	 * Enable / disable hardware flow control.
 	 *
 	 * @param enabled	True if hardware flow control should be enabled
 	 */
-	int enable_flow_control(bool enabled);
+	int			enable_flow_control(bool enabled);
 
-	mavlink_channel_t get_channel();
+	const mavlink_channel_t	get_channel();
 
 	void configure_stream_threadsafe(const char *stream_name, const float rate);
 
-	bool		_task_should_exit;		/**< if true, mavlink task should exit */
+	bool			_task_should_exit;	/**< if true, mavlink task should exit */
 
-	int get_mavlink_fd() { return _mavlink_fd; }
+	int			get_mavlink_fd() { return _mavlink_fd; }
 
 	MavlinkStream * get_streams() { return _streams; } const
 
 
 	/* Functions for waiting to start transmission until message received. */
-	void set_has_received_messages(bool received_messages) { _received_messages = received_messages; }
-	bool get_has_received_messages() { return _received_messages; }
-	void set_wait_to_transmit(bool wait) { _wait_to_transmit = wait; }
-	bool get_wait_to_transmit() { return _wait_to_transmit; }
-	bool should_transmit() { return (!_wait_to_transmit || (_wait_to_transmit && _received_messages)); }
+	void			set_has_received_messages(bool received_messages) { _received_messages = received_messages; }
+	bool			get_has_received_messages() { return _received_messages; }
+	void			set_wait_to_transmit(bool wait) { _wait_to_transmit = wait; }
+	bool			get_wait_to_transmit() { return _wait_to_transmit; }
+	bool			should_transmit() { return (!_wait_to_transmit || (_wait_to_transmit && _received_messages)); }
+
+	bool			message_buffer_write(void *ptr, int size);
+    
+    void lockMessageBufferMutex(void) { pthread_mutex_lock(&_message_buffer_mutex); }
+    void unlockMessageBufferMutex(void) { pthread_mutex_unlock(&_message_buffer_mutex); }
 
 	/**
 	 * Count a transmision error
@@ -223,62 +242,63 @@ public:
 	void count_txerr();
 
 protected:
-	Mavlink	*next;
+	Mavlink			*next;
 
 private:
-	int _instance_id;
+	int			_instance_id;
 
-	int		_mavlink_fd;
-	bool		_task_running;
+	int			_mavlink_fd;
+	bool			_task_running;
 
 	/* states */
-	bool		_hil_enabled;		/**< Hardware In the Loop mode */
-	bool		_use_hil_gps;		/**< Accept GPS HIL messages (for example from an external motion capturing system to fake indoor gps) */
-	bool		_is_usb_uart;		/**< Port is USB */
-	bool        _wait_to_transmit;  /**< Wait to transmit until received messages. */
-	bool        _received_messages; /**< Whether we've received valid mavlink messages. */
+	bool			_hil_enabled;		/**< Hardware In the Loop mode */
+	bool			_use_hil_gps;		/**< Accept GPS HIL messages (for example from an external motion capturing system to fake indoor gps) */
+	bool			_is_usb_uart;		/**< Port is USB */
+	bool        		_wait_to_transmit;  	/**< Wait to transmit until received messages. */
+	bool        		_received_messages;	/**< Whether we've received valid mavlink messages. */
 
-	unsigned	_main_loop_delay;		/**< mainloop delay, depends on data rate */
+	unsigned		_main_loop_delay;	/**< mainloop delay, depends on data rate */
 
-	MavlinkOrbSubscription *_subscriptions;
-	MavlinkStream *_streams;
+	MavlinkOrbSubscription	*_subscriptions;
+	MavlinkStream		*_streams;
 
-	orb_advert_t	_mission_pub;
-	struct mission_s mission;
-	MAVLINK_MODE _mode;
+	orb_advert_t		_mission_pub;
+	struct mission_s	mission;
+	MAVLINK_MODE		_mode;
 
-	uint8_t _mavlink_wpm_comp_id;
-	mavlink_channel_t _channel;
+	uint8_t			_mavlink_wpm_comp_id;
+	mavlink_channel_t	_channel;
 
 	struct mavlink_logbuffer _logbuffer;
-	unsigned int _total_counter;
+	unsigned int		_total_counter;
 
-	pthread_t _receive_thread;
+	pthread_t		_receive_thread;
 
 	/* Allocate storage space for waypoints */
-	mavlink_wpm_storage _wpm_s;
-	mavlink_wpm_storage *_wpm;
+	mavlink_wpm_storage	_wpm_s;
+	mavlink_wpm_storage	*_wpm;
 
-	bool _verbose;
-	bool _forwarding_on;
-	bool _passing_on;
-	int _uart_fd;
-	int _baudrate;
-	int _datarate;
+	bool			_verbose;
+	bool			_forwarding_on;
+	bool			_passing_on;
+	bool			_ftp_on;
+	int			_uart_fd;
+	int			_baudrate;
+	int			_datarate;
 
 	/**
 	 * If the queue index is not at 0, the queue sending
 	 * logic will send parameters from the current index
 	 * to len - 1, the end of the param list.
 	 */
-	unsigned int _mavlink_param_queue_index;
+	unsigned int		_mavlink_param_queue_index;
 
-	bool mavlink_link_termination_allowed;
+	bool			mavlink_link_termination_allowed;
 
-	char 	*_subscribe_to_stream;
-	float	_subscribe_to_stream_rate;
+	char 			*_subscribe_to_stream;
+	float			_subscribe_to_stream_rate;
 
-	bool		_flow_control_enabled;
+	bool			_flow_control_enabled;
 
 	struct mavlink_message_buffer {
 		int write_ptr;
@@ -286,12 +306,13 @@ private:
 		int size;
 		char *data;
 	};
+
 	mavlink_message_buffer	_message_buffer;
 
 	pthread_mutex_t		_message_buffer_mutex;
 
-	perf_counter_t	_loop_perf;			/**< loop performance counter */
-	perf_counter_t	_txerr_perf;			/**< TX error counter */
+	perf_counter_t		_loop_perf;			/**< loop performance counter */
+	perf_counter_t		_txerr_perf;			/**< TX error counter */
 
 	bool			_param_initialized;
 	param_t			_param_system_id;
@@ -305,7 +326,7 @@ private:
 	 * @param param		The parameter id to send.
 	 * @return		zero on success, nonzero on failure.
 	 */
-	int mavlink_pm_send_param(param_t param);
+	int			mavlink_pm_send_param(param_t param);
 
 	/**
 	 * Send one parameter identified by index.
@@ -313,7 +334,7 @@ private:
 	 * @param index		The index of the parameter to send.
 	 * @return		zero on success, nonzero else.
 	 */
-	int mavlink_pm_send_param_for_index(uint16_t index);
+	int			mavlink_pm_send_param_for_index(uint16_t index);
 
 	/**
 	 * Send one parameter identified by name.
@@ -321,14 +342,14 @@ private:
 	 * @param name		The index of the parameter to send.
 	 * @return		zero on success, nonzero else.
 	 */
-	int mavlink_pm_send_param_for_name(const char *name);
+	int			mavlink_pm_send_param_for_name(const char *name);
 
 	/**
 	 * Send a queue of parameters, one parameter per function call.
 	 *
 	 * @return		zero on success, nonzero on failure
 	 */
-	int mavlink_pm_queued_send(void);
+	int			mavlink_pm_queued_send(void);
 
 	/**
 	 * Start sending the parameter queue.
@@ -338,12 +359,12 @@ private:
 	 * mavlink_pm_queued_send().
 	 * @see 		mavlink_pm_queued_send()
 	 */
-	void mavlink_pm_start_queued_send();
+	void			mavlink_pm_start_queued_send();
 
-	void mavlink_update_system();
+	void			mavlink_update_system();
 
-	void mavlink_waypoint_eventloop(uint64_t now);
-	void mavlink_wpm_send_waypoint_reached(uint16_t seq);
+	void			mavlink_waypoint_eventloop(uint64_t now);
+	void 			mavlink_wpm_send_waypoint_reached(uint16_t seq);
 	void mavlink_wpm_send_waypoint_request(uint8_t sysid, uint8_t compid, uint16_t seq);
 	void mavlink_wpm_send_waypoint(uint8_t sysid, uint8_t compid, uint16_t seq);
 	void mavlink_wpm_send_waypoint_count(uint8_t sysid, uint8_t compid, uint16_t count);
@@ -369,8 +390,6 @@ private:
 
 	int message_buffer_is_empty();
 
-	bool message_buffer_write(void *ptr, int size);
-
 	int message_buffer_get_ptr(void **ptr, bool *is_part);
 
 	void message_buffer_mark_read(int n);
diff --git a/src/modules/mavlink/mavlink_messages.cpp b/src/modules/mavlink/mavlink_messages.cpp
index 2458dd23a..e1ebc16cc 100644
--- a/src/modules/mavlink/mavlink_messages.cpp
+++ b/src/modules/mavlink/mavlink_messages.cpp
@@ -259,8 +259,15 @@ protected:
 		struct position_setpoint_triplet_s pos_sp_triplet;
 
 		/* always send the heartbeat, independent of the update status of the topics */
-		(void)status_sub->update(&status);
-		(void)pos_sp_triplet_sub->update(&pos_sp_triplet);
+		if (!status_sub->update(&status)) {
+			/* if topic update failed fill it with defaults */
+			memset(&status, 0, sizeof(status));
+		}
+
+		if (!pos_sp_triplet_sub->update(&pos_sp_triplet)) {
+			/* if topic update failed fill it with defaults */
+			memset(&pos_sp_triplet, 0, sizeof(pos_sp_triplet));
+		}
 
 		uint8_t mavlink_state = 0;
 		uint8_t mavlink_base_mode = 0;
diff --git a/src/modules/mavlink/mavlink_receiver.cpp b/src/modules/mavlink/mavlink_receiver.cpp
index 425fc79a5..bb977d277 100644
--- a/src/modules/mavlink/mavlink_receiver.cpp
+++ b/src/modules/mavlink/mavlink_receiver.cpp
@@ -114,6 +114,9 @@ MavlinkReceiver::MavlinkReceiver(Mavlink *parent) :
 	_hil_local_alt0(0.0)
 {
 	memset(&hil_local_pos, 0, sizeof(hil_local_pos));
+
+	// make sure the FTP server is started
+	(void)MavlinkFTP::getServer();
 }
 
 MavlinkReceiver::~MavlinkReceiver()
@@ -160,6 +163,10 @@ MavlinkReceiver::handle_message(mavlink_message_t *msg)
 		handle_message_request_data_stream(msg);
 		break;
 
+	case MAVLINK_MSG_ID_ENCAPSULATED_DATA:
+		MavlinkFTP::getServer()->handle_message(_mavlink, msg);
+		break;
+
 	default:
 		break;
 	}
diff --git a/src/modules/mavlink/mavlink_receiver.h b/src/modules/mavlink/mavlink_receiver.h
index af81e8a31..040a07480 100644
--- a/src/modules/mavlink/mavlink_receiver.h
+++ b/src/modules/mavlink/mavlink_receiver.h
@@ -68,6 +68,8 @@
 #include <uORB/topics/airspeed.h>
 #include <uORB/topics/battery_status.h>
 
+#include "mavlink_ftp.h"
+
 class Mavlink;
 
 class MavlinkReceiver
diff --git a/src/modules/mavlink/module.mk b/src/modules/mavlink/module.mk
index f532e26fe..a4d8bfbfb 100644
--- a/src/modules/mavlink/module.mk
+++ b/src/modules/mavlink/module.mk
@@ -43,7 +43,8 @@ SRCS		 += mavlink_main.cpp \
 			mavlink_messages.cpp \
 			mavlink_stream.cpp \
 			mavlink_rate_limiter.cpp \
-			mavlink_commands.cpp
+			mavlink_commands.cpp \
+			mavlink_ftp.cpp
 
 INCLUDE_DIRS	 += $(MAVLINK_SRC)/include/mavlink