FTP: Remove CRC32 from protocol.

Extra crc not needed because mavlink already has crc16.

src/modules/mavlink/mavlink_ftp.cpp

@@ -34,7 +34,6 @@
 /// @file mavlink_ftp.cpp
 ///	@author px4dev, Don Gagne <don@thegagnes.com>
 
-#include <crc32.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <fcntl.h>
@@ -161,13 +160,6 @@ MavlinkFTP::_process_request(Request *req)
 		goto out;
 	}
 
-	// check request CRC to make sure this is one of ours
-	if (_payload_crc32(payload) != payload->crc32) {
-		errorCode = kErrCrc;
-		goto out;
-		warnx("ftp: bad crc");
-	}
-
 #ifdef MAVLINK_FTP_DEBUG
 	printf("ftp: channel %u opc %u size %u offset %u\n", req->serverChannel, payload->opcode, payload->size, payload->offset);
 #endif
@@ -255,8 +247,9 @@ MavlinkFTP::_reply(Request *req)
 	PayloadHeader *payload = reinterpret_cast<PayloadHeader *>(&req->message.payload[0]);
 	
 	payload->seqNumber = payload->seqNumber + 1;
-
-	payload->crc32 = _payload_crc32(payload);
+	payload->reserved[0] = 0;
+	payload->reserved[1] = 0;
+	payload->reserved[2] = 0;
 
 	mavlink_message_t msg;
 	msg.checksum = 0;
@@ -647,17 +640,3 @@ MavlinkFTP::_return_request(Request *req)
 	_unlock_request_queue();
 }
 
-/// @brief Returns the 32 bit CRC for the payload, crc32 and padding members are set to 0 for calculation.
-uint32_t
-MavlinkFTP::_payload_crc32(PayloadHeader *payload)
-{
-	// We calculate CRC with crc and padding set to 0.
-	uint32_t saveCRC = payload->crc32;
-	payload->crc32 = 0;
-	payload->padding[0] = 0;
-	payload->padding[1] = 0;
-	uint32_t retCRC = crc32((const uint8_t*)payload, payload->size + sizeof(PayloadHeader));
-	payload->crc32 = saveCRC;
-		
-	return retCRC;
-}

src/modules/mavlink/mavlink_ftp.h

@@ -77,8 +77,7 @@ public:
 		uint8_t		opcode;		///< Command opcode
 		uint8_t		size;		///< Size of data
 		uint8_t		req_opcode;	///< Request opcode returned in kRspAck, kRspNak message
-		uint8_t		padding[2];	///< 32 bit aligment padding
-		uint32_t	crc32;		///< CRC for entire Request structure, with crc32 and padding set to 0
+		uint16_t	reserved[3];	///< reserved area
 		uint32_t	offset;		///< Offsets for List and Read commands
 		uint8_t		data[];		///< command data, varies by Opcode
         };
@@ -112,8 +111,7 @@ public:
 		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
-		kErrCrc				///< CRC on Payload is incorrect
+		kErrUnknownCommand		///< Unknown command opcode
         };
 	
 private:
@@ -135,8 +133,6 @@ private:
 	void		_lock_request_queue(void);
 	void		_unlock_request_queue(void);
 	
-	uint32_t	_payload_crc32(PayloadHeader *hdr);
-	
 	char		*_data_as_cstring(PayloadHeader* payload);
 	
 	static void	_worker_trampoline(void *arg);