ftp.cpp

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/*
 * Copyright 2014,2016 Vladimir Ermakov.
 *
 * This file is part of the mavros package and subject to the license terms
 * in the top-level LICENSE file of the mavros repository.
 * https://github.com/mavlink/mavros/tree/master/LICENSE.md
 */

#include <chrono>
#include <cerrno>
#include <condition_variable>
#include <mavros/mavros_plugin.h>

#include <std_srvs/Empty.h>
#include <mavros_msgs/FileEntry.h>
#include <mavros_msgs/FileList.h>
#include <mavros_msgs/FileOpen.h>
#include <mavros_msgs/FileClose.h>
#include <mavros_msgs/FileRead.h>
#include <mavros_msgs/FileWrite.h>
#include <mavros_msgs/FileRemove.h>
#include <mavros_msgs/FileMakeDir.h>
#include <mavros_msgs/FileRemoveDir.h>
#include <mavros_msgs/FileTruncate.h>
#include <mavros_msgs/FileRename.h>
#include <mavros_msgs/FileChecksum.h>

// enable debugging messages
//#define FTP_LL_DEBUG

namespace mavros {
namespace std_plugins {
using utils::enum_value;

class FTPRequest : public mavlink::common::msg::FILE_TRANSFER_PROTOCOL {
public:
        struct PayloadHeader {
                uint16_t        seqNumber;      
                uint8_t         session;        
                uint8_t         opcode;         
                uint8_t         size;           
                uint8_t         req_opcode;     
                uint8_t         padding[2];     
                uint32_t        offset;         
                uint8_t         data[];         
        };

        enum Opcode : uint8_t {
                kCmdNone,               
                kCmdTerminateSession,   
                kCmdResetSessions,      
                kCmdListDirectory,      
                kCmdOpenFileRO,         
                kCmdReadFile,           
                kCmdCreateFile,         
                kCmdWriteFile,          
                kCmdRemoveFile,         
                kCmdCreateDirectory,    
                kCmdRemoveDirectory,    
                kCmdOpenFileWO,         
                kCmdTruncateFile,       
                kCmdRename,             
                kCmdCalcFileCRC32,      
                kCmdBurstReadFile,      

                kRspAck = 128,          
                kRspNak                 
        };

        enum ErrorCode : uint8_t {
                kErrNone,
                kErrFail,                       
                kErrFailErrno,                  
                kErrInvalidDataSize,            
                kErrInvalidSession,             
                kErrNoSessionsAvailable,        
                kErrEOF,                        
                kErrUnknownCommand,             
                kErrFailFileExists,             
                kErrFailFileProtected           
        };

        static const char       DIRENT_FILE = 'F';
        static const char       DIRENT_DIR = 'D';
        static const char       DIRENT_SKIP = 'S';
        static const uint8_t    DATA_MAXSZ = 251 - sizeof(PayloadHeader);

        uint8_t *raw_payload() {
                return payload.data();
        }

        inline PayloadHeader *header() {
                return reinterpret_cast<PayloadHeader *>(payload.data());
        }

        uint8_t *data() {
                return header()->data;
        }

        char *data_c() {
                return reinterpret_cast<char *>(header()->data);
        }

        uint32_t *data_u32() {
                return reinterpret_cast<uint32_t *>(header()->data);
        }

        void set_data_string(std::string &s)
        {
                size_t sz = (s.size() < DATA_MAXSZ - 1) ? s.size() : DATA_MAXSZ - 1;

                memcpy(data_c(), s.c_str(), sz);
                data_c()[sz] = '\0';
                header()->size = sz;
        }

        uint8_t get_target_system_id() {
                return target_system;
        }

        bool decode_valid(UAS *uas)
        {
#ifdef FTP_LL_DEBUG
                auto hdr = header();
                ROS_DEBUG_NAMED("ftp", "FTP:rm: SEQ(%u) SESS(%u) OPCODE(%u) RQOP(%u) SZ(%u) OFF(%u)",
                                hdr->seqNumber, hdr->session, hdr->opcode, hdr->req_opcode, hdr->size, hdr->offset);
#endif

                return UAS_FCU(uas)->get_system_id() == target_system;
        }

        void send(UAS *uas, uint16_t seqNumber)
        {
                target_network = 0;
                target_system = uas->get_tgt_system();
                target_component = uas->get_tgt_component();

                auto hdr = header();
                hdr->seqNumber = seqNumber;
                hdr->req_opcode = kCmdNone;

#ifdef FTP_LL_DEBUG
                ROS_DEBUG_NAMED("ftp", "FTP:sm: SEQ(%u) SESS(%u) OPCODE(%u) SZ(%u) OFF(%u)",
                                hdr->seqNumber, hdr->session, hdr->opcode, hdr->size, hdr->offset);
#endif

                UAS_FCU(uas)->send_message_ignore_drop(*this);
        }

        FTPRequest() :
                mavlink::common::msg::FILE_TRANSFER_PROTOCOL{}
        { }

        explicit FTPRequest(Opcode op, uint8_t session = 0) :
                mavlink::common::msg::FILE_TRANSFER_PROTOCOL{}
        {
                header()->session = session;
                header()->opcode = op;
        }
};


class FTPPlugin : public plugin::PluginBase {
public:
        FTPPlugin() : PluginBase(),
                ftp_nh("~ftp"),
                op_state(OP::IDLE),
                last_send_seqnr(0),
                active_session(0),
                is_error(false),
                r_errno(0),
                list_offset(0),
                read_offset(0),
                write_offset(0),
                open_size(0),
                read_size(0),
                read_buffer {},
                checksum_crc32(0)
        { }

        void initialize(UAS &uas_) override
        {
                PluginBase::initialize(uas_);

                // since C++ generator do not produce field length defs make check explicit.
                FTPRequest r;
                ROS_ASSERT(r.payload.size() - sizeof(FTPRequest::PayloadHeader) == r.DATA_MAXSZ);

                list_srv = ftp_nh.advertiseService("list", &FTPPlugin::list_cb, this);
                open_srv = ftp_nh.advertiseService("open", &FTPPlugin::open_cb, this);
                close_srv = ftp_nh.advertiseService("close", &FTPPlugin::close_cb, this);
                read_srv = ftp_nh.advertiseService("read", &FTPPlugin::read_cb, this);
                write_srv = ftp_nh.advertiseService("write", &FTPPlugin::write_cb, this);
                mkdir_srv = ftp_nh.advertiseService("mkdir", &FTPPlugin::mkdir_cb, this);
                rmdir_srv = ftp_nh.advertiseService("rmdir", &FTPPlugin::rmdir_cb, this);
                remove_srv = ftp_nh.advertiseService("remove", &FTPPlugin::remove_cb, this);
                truncate_srv = ftp_nh.advertiseService("truncate", &FTPPlugin::truncate_cb, this);
                reset_srv = ftp_nh.advertiseService("reset", &FTPPlugin::reset_cb, this);
                rename_srv = ftp_nh.advertiseService("rename", &FTPPlugin::rename_cb, this);
                checksum_srv = ftp_nh.advertiseService("checksum", &FTPPlugin::checksum_cb, this);
        }

        Subscriptions get_subscriptions() override
        {
                return {
                        make_handler(&FTPPlugin::handle_file_transfer_protocol),
                };
        }

private:
        ros::NodeHandle ftp_nh;
        ros::ServiceServer list_srv;
        ros::ServiceServer open_srv;
        ros::ServiceServer close_srv;
        ros::ServiceServer read_srv;
        ros::ServiceServer write_srv;
        ros::ServiceServer mkdir_srv;
        ros::ServiceServer rmdir_srv;
        ros::ServiceServer remove_srv;
        ros::ServiceServer rename_srv;
        ros::ServiceServer truncate_srv;
        ros::ServiceServer reset_srv;
        ros::ServiceServer checksum_srv;

        typedef std::vector<uint8_t> V_FileData;

        enum class OP {
                IDLE,
                ACK,
                LIST,
                OPEN,
                READ,
                WRITE,
                CHECKSUM
        };

        OP op_state;
        uint16_t last_send_seqnr;       
        uint32_t active_session;        

        std::mutex cond_mutex;
        std::condition_variable cond;   
        bool is_error;                  
        int r_errno;                    

        // FTP:List
        uint32_t list_offset;
        std::string list_path;
        std::vector<mavros_msgs::FileEntry> list_entries;

        // FTP:Open / FTP:Close
        std::string open_path;
        size_t open_size;
        std::map<std::string, uint32_t> session_file_map;

        // FTP:Read
        size_t read_size;
        uint32_t read_offset;
        V_FileData read_buffer;

        // FTP:Write
        uint32_t write_offset;
        V_FileData write_buffer;
        V_FileData::iterator write_it;

        // FTP:CalcCRC32
        uint32_t checksum_crc32;

        // Timeouts,
        // computed as x4 time that needed for transmission of
        // one message at 57600 baud rate
        static constexpr int LIST_TIMEOUT_MS = 5000;
        static constexpr int OPEN_TIMEOUT_MS = 200;
        static constexpr int CHUNK_TIMEOUT_MS = 200;

        static constexpr size_t MAX_RESERVE_DIFF = 0x10000;


        /* -*- message handler -*- */

        void handle_file_transfer_protocol(const mavlink::mavlink_message_t *msg, FTPRequest &req)
        {
                if (!req.decode_valid(m_uas)) {
                        ROS_DEBUG_NAMED("ftp", "FTP: Wrong System Id, MY %u, TGT %u",
                                        UAS_FCU(m_uas)->get_system_id(), req.get_target_system_id());
                        return;
                }

                const uint16_t incoming_seqnr = req.header()->seqNumber;
                const uint16_t expected_seqnr = last_send_seqnr + 1;
                if (incoming_seqnr != expected_seqnr) {
                        ROS_WARN_NAMED("ftp", "FTP: Lost sync! seqnr: %u != %u",
                                        incoming_seqnr, expected_seqnr);
                        go_idle(true, EILSEQ);
                        return;
                }

                last_send_seqnr = incoming_seqnr;

                // logic from QGCUASFileManager.cc
                if (req.header()->opcode == FTPRequest::kRspAck)
                        handle_req_ack(req);
                else if (req.header()->opcode == FTPRequest::kRspNak)
                        handle_req_nack(req);
                else {
                        ROS_ERROR_NAMED("ftp", "FTP: Unknown request response: %u", req.header()->opcode);
                        go_idle(true, EBADRQC);
                }
        }

        void handle_req_ack(FTPRequest &req)
        {
                switch (op_state) {
                case OP::IDLE:          send_reset();                   break;
                case OP::ACK:           go_idle(false);                 break;
                case OP::LIST:          handle_ack_list(req);           break;
                case OP::OPEN:          handle_ack_open(req);           break;
                case OP::READ:          handle_ack_read(req);           break;
                case OP::WRITE:         handle_ack_write(req);          break;
                case OP::CHECKSUM:      handle_ack_checksum(req);       break;
                default:
                        ROS_ERROR_NAMED("ftp", "FTP: wrong op_state");
                        go_idle(true, EBADRQC);
                }
        }

        void handle_req_nack(FTPRequest &req)
        {
                auto hdr = req.header();
                auto error_code = static_cast<FTPRequest::ErrorCode>(req.data()[0]);
                auto prev_op = op_state;

                ROS_ASSERT(hdr->size == 1 || (error_code == FTPRequest::kErrFailErrno && hdr->size == 2));

                op_state = OP::IDLE;
                if (error_code == FTPRequest::kErrFailErrno)
                        r_errno = req.data()[1];
                // translate other protocol errors to errno
                else if (error_code == FTPRequest::kErrFail)
                        r_errno = EFAULT;
                else if (error_code == FTPRequest::kErrInvalidDataSize)
                        r_errno = EMSGSIZE;
                else if (error_code == FTPRequest::kErrInvalidSession)
                        r_errno = EBADFD;
                else if (error_code == FTPRequest::kErrNoSessionsAvailable)
                        r_errno = EMFILE;
                else if (error_code == FTPRequest::kErrUnknownCommand)
                        r_errno = ENOSYS;

                if (prev_op == OP::LIST && error_code == FTPRequest::kErrEOF) {
                        /* dir list done */
                        list_directory_end();
                        return;
                }
                else if (prev_op == OP::READ && error_code == FTPRequest::kErrEOF) {
                        /* read done */
                        read_file_end();
                        return;
                }

                ROS_ERROR_NAMED("ftp", "FTP: NAK: %u Opcode: %u State: %u Errno: %d (%s)",
                                error_code, hdr->req_opcode, enum_value(prev_op), r_errno, strerror(r_errno));
                go_idle(true);
        }

        void handle_ack_list(FTPRequest &req)
        {
                auto hdr = req.header();

                ROS_DEBUG_NAMED("ftp", "FTP:m: ACK List SZ(%u) OFF(%u)", hdr->size, hdr->offset);
                if (hdr->offset != list_offset) {
                        ROS_ERROR_NAMED("ftp", "FTP: Wrong list offset, req %u, ret %u",
                                        list_offset, hdr->offset);
                        go_idle(true, EBADE);
                        return;
                }

                uint8_t off = 0;
                uint32_t n_list_entries = 0;

                while (off < hdr->size) {
                        const char *ptr = req.data_c() + off;
                        const size_t bytes_left = hdr->size - off;

                        size_t slen = strnlen(ptr, bytes_left);
                        if ((ptr[0] == FTPRequest::DIRENT_SKIP && slen > 1) ||
                                        (ptr[0] != FTPRequest::DIRENT_SKIP && slen < 2)) {
                                ROS_ERROR_NAMED("ftp", "FTP: Incorrect list entry: %s", ptr);
                                go_idle(true, ERANGE);
                                return;
                        }
                        else if (slen == bytes_left) {
                                ROS_ERROR_NAMED("ftp", "FTP: Missing NULL termination in list entry");
                                go_idle(true, EOVERFLOW);
                                return;
                        }

                        if (ptr[0] == FTPRequest::DIRENT_FILE ||
                                        ptr[0] == FTPRequest::DIRENT_DIR) {
                                add_dirent(ptr, slen);
                        }
                        else if (ptr[0] == FTPRequest::DIRENT_SKIP) {
                                // do nothing
                        }
                        else {
                                ROS_WARN_NAMED("ftp", "FTP: Unknown list entry: %s", ptr);
                        }

                        off += slen + 1;
                        n_list_entries++;
                }

                if (hdr->size == 0) {
                        // dir empty, we are done
                        list_directory_end();
                }
                else {
                        ROS_ASSERT_MSG(n_list_entries > 0, "FTP:List don't parse entries");
                        // Possibly more to come, try get more
                        list_offset += n_list_entries;
                        send_list_command();
                }
        }

        void handle_ack_open(FTPRequest &req)
        {
                auto hdr = req.header();

                ROS_DEBUG_NAMED("ftp", "FTP:m: ACK Open OPCODE(%u)", hdr->req_opcode);
                ROS_ASSERT(hdr->size == sizeof(uint32_t));
                open_size = *req.data_u32();

                ROS_INFO_NAMED("ftp", "FTP:Open %s: success, session %u, size %zu",
                                open_path.c_str(), hdr->session, open_size);
                session_file_map.insert(std::make_pair(open_path, hdr->session));
                go_idle(false);
        }

        void handle_ack_read(FTPRequest &req)
        {
                auto hdr = req.header();

                ROS_DEBUG_NAMED("ftp", "FTP:m: ACK Read SZ(%u)", hdr->size);
                if (hdr->session != active_session) {
                        ROS_ERROR_NAMED("ftp", "FTP:Read unexpected session");
                        go_idle(true, EBADSLT);
                        return;
                }

                if (hdr->offset != read_offset) {
                        ROS_ERROR_NAMED("ftp", "FTP:Read different offset");
                        go_idle(true, EBADE);
                        return;
                }

                // kCmdReadFile return cunks of DATA_MAXSZ or smaller (last chunk)
                // We requested specific amount of data, that can be smaller,
                // but not larger.
                const size_t bytes_left = read_size - read_buffer.size();
                const size_t bytes_to_copy = std::min<size_t>(bytes_left, hdr->size);

                read_buffer.insert(read_buffer.end(), req.data(), req.data() + bytes_to_copy);

                if (bytes_to_copy == FTPRequest::DATA_MAXSZ) {
                        // Possibly more data
                        read_offset += bytes_to_copy;
                        send_read_command();
                }
                else
                        read_file_end();
        }

        void handle_ack_write(FTPRequest &req)
        {
                auto hdr = req.header();

                ROS_DEBUG_NAMED("ftp", "FTP:m: ACK Write SZ(%u)", hdr->size);
                if (hdr->session != active_session) {
                        ROS_ERROR_NAMED("ftp", "FTP:Write unexpected session");
                        go_idle(true, EBADSLT);
                        return;
                }

                if (hdr->offset != write_offset) {
                        ROS_ERROR_NAMED("ftp", "FTP:Write different offset");
                        go_idle(true, EBADE);
                        return;
                }

                ROS_ASSERT(hdr->size == sizeof(uint32_t));
                const size_t bytes_written = *req.data_u32();

                // check that reported size not out of range
                const size_t bytes_left_before_advance = std::distance(write_it, write_buffer.end());
                ROS_ASSERT_MSG(bytes_written <= bytes_left_before_advance, "Bad write size");
                ROS_ASSERT(bytes_written != 0);

                // move iterator to written size
                std::advance(write_it, bytes_written);

                const size_t bytes_to_copy = write_bytes_to_copy();
                if (bytes_to_copy > 0) {
                        // More data to write
                        write_offset += bytes_written;
                        send_write_command(bytes_to_copy);
                }
                else
                        write_file_end();
        }

        void handle_ack_checksum(FTPRequest &req)
        {
                auto hdr = req.header();

                ROS_DEBUG_NAMED("ftp", "FTP:m: ACK CalcFileCRC32 OPCODE(%u)", hdr->req_opcode);
                ROS_ASSERT(hdr->size == sizeof(uint32_t));
                checksum_crc32 = *req.data_u32();

                ROS_DEBUG_NAMED("ftp", "FTP:Checksum: success, crc32: 0x%08x", checksum_crc32);
                go_idle(false);
        }

        /* -*- send helpers -*- */

        void go_idle(bool is_error_, int r_errno_ = 0)
        {
                op_state = OP::IDLE;
                is_error = is_error_;
                if (is_error && r_errno_ != 0) r_errno = r_errno_;
                else if (!is_error) r_errno = 0;
                cond.notify_all();
        }

        void send_reset()
        {
                ROS_DEBUG_NAMED("ftp", "FTP:m: kCmdResetSessions");
                if (!session_file_map.empty()) {
                        ROS_WARN_NAMED("ftp", "FTP: Reset closes %zu sessons",
                                        session_file_map.size());
                        session_file_map.clear();
                }

                op_state = OP::ACK;
                FTPRequest req(FTPRequest::kCmdResetSessions);
                req.send(m_uas, last_send_seqnr);
        }

        inline void send_any_path_command(FTPRequest::Opcode op, const std::string &debug_msg, std::string &path, uint32_t offset)
        {
                ROS_DEBUG_STREAM_NAMED("ftp", "FTP:m: " << debug_msg << path << " off: " << offset);
                FTPRequest req(op);
                req.header()->offset = offset;
                req.set_data_string(path);
                req.send(m_uas, last_send_seqnr);
        }

        void send_list_command() {
                send_any_path_command(FTPRequest::kCmdListDirectory, "kCmdListDirectory: ", list_path, list_offset);
        }

        void send_open_ro_command() {
                send_any_path_command(FTPRequest::kCmdOpenFileRO, "kCmdOpenFileRO: ", open_path, 0);
        }

        void send_open_wo_command() {
                send_any_path_command(FTPRequest::kCmdOpenFileWO, "kCmdOpenFileWO: ", open_path, 0);
        }

        void send_create_command() {
                send_any_path_command(FTPRequest::kCmdCreateFile, "kCmdCreateFile: ", open_path, 0);
        }

        void send_terminate_command(uint32_t session)
        {
                ROS_DEBUG_STREAM_NAMED("ftp", "FTP:m: kCmdTerminateSession: " << session);
                FTPRequest req(FTPRequest::kCmdTerminateSession, session);
                req.header()->offset = 0;
                req.header()->size = 0;
                req.send(m_uas, last_send_seqnr);
        }

        void send_read_command()
        {
                // read operation always try read DATA_MAXSZ block (hdr->size ignored)
                ROS_DEBUG_STREAM_NAMED("ftp", "FTP:m: kCmdReadFile: " << active_session << " off: " << read_offset);
                FTPRequest req(FTPRequest::kCmdReadFile, active_session);
                req.header()->offset = read_offset;
                req.header()->size = 0 /* FTPRequest::DATA_MAXSZ */;
                req.send(m_uas, last_send_seqnr);
        }

        void send_write_command(const size_t bytes_to_copy)
        {
                // write chunk from write_buffer [write_it..bytes_to_copy]
                ROS_DEBUG_STREAM_NAMED("ftp", "FTP:m: kCmdWriteFile: " << active_session << " off: " << write_offset << " sz: " << bytes_to_copy);
                FTPRequest req(FTPRequest::kCmdWriteFile, active_session);
                req.header()->offset = write_offset;
                req.header()->size = bytes_to_copy;
                std::copy(write_it, write_it + bytes_to_copy, req.data());
                req.send(m_uas, last_send_seqnr);
        }

        void send_remove_command(std::string &path) {
                send_any_path_command(FTPRequest::kCmdRemoveFile, "kCmdRemoveFile: ", path, 0);
        }

        bool send_rename_command(std::string &old_path, std::string &new_path)
        {
                std::ostringstream os;
                os << old_path;
                os << '\0';
                os << new_path;

                std::string paths = os.str();
                if (paths.size() >= FTPRequest::DATA_MAXSZ) {
                        ROS_ERROR_NAMED("ftp", "FTP: rename file paths is too long: %zu", paths.size());
                        r_errno = ENAMETOOLONG;
                        return false;
                }

                send_any_path_command(FTPRequest::kCmdRename, "kCmdRename: ", paths, 0);
                return true;
        }

        void send_truncate_command(std::string &path, size_t length) {
                send_any_path_command(FTPRequest::kCmdTruncateFile, "kCmdTruncateFile: ", path, length);
        }

        void send_create_dir_command(std::string &path) {
                send_any_path_command(FTPRequest::kCmdCreateDirectory, "kCmdCreateDirectory: ", path, 0);
        }

        void send_remove_dir_command(std::string &path) {
                send_any_path_command(FTPRequest::kCmdRemoveDirectory, "kCmdRemoveDirectory: ", path, 0);
        }

        void send_calc_file_crc32_command(std::string &path) {
                send_any_path_command(FTPRequest::kCmdCalcFileCRC32, "kCmdCalcFileCRC32: ", path, 0);
        }

        /* -*- helpers -*- */

        void add_dirent(const char *ptr, size_t slen)
        {
                mavros_msgs::FileEntry ent;
                ent.size = 0;

                if (ptr[0] == FTPRequest::DIRENT_DIR) {
                        ent.name.assign(ptr + 1, slen - 1);
                        ent.type = mavros_msgs::FileEntry::TYPE_DIRECTORY;

                        ROS_DEBUG_STREAM_NAMED("ftp", "FTP:List Dir: " << ent.name);
                }
                else {
                        // ptr[0] == FTPRequest::DIRENT_FILE
                        std::string name_size(ptr + 1, slen - 1);

                        auto sep_it = std::find(name_size.begin(), name_size.end(), '\t');
                        ent.name.assign(name_size.begin(), sep_it);
                        ent.type = mavros_msgs::FileEntry::TYPE_FILE;

                        if (sep_it != name_size.end()) {
                                name_size.erase(name_size.begin(), sep_it + 1);
                                if (name_size.size() != 0)
                                        ent.size = std::stoi(name_size);
                        }

                        ROS_DEBUG_STREAM_NAMED("ftp", "FTP:List File: " << ent.name << " SZ: " << ent.size);
                }

                list_entries.push_back(ent);
        }

        void list_directory_end() {
                ROS_DEBUG_NAMED("ftp", "FTP:List done");
                go_idle(false);
        }

        void list_directory(std::string &path)
        {
                list_offset = 0;
                list_path = path;
                list_entries.clear();
                op_state = OP::LIST;

                send_list_command();
        }

        bool open_file(std::string &path, int mode)
        {
                open_path = path;
                open_size = 0;
                op_state = OP::OPEN;

                if (mode == mavros_msgs::FileOpenRequest::MODE_READ)
                        send_open_ro_command();
                else if (mode == mavros_msgs::FileOpenRequest::MODE_WRITE)
                        send_open_wo_command();
                else if (mode == mavros_msgs::FileOpenRequest::MODE_CREATE)
                        send_create_command();
                else {
                        ROS_ERROR_NAMED("ftp", "FTP: Unsupported open mode: %d", mode);
                        op_state = OP::IDLE;
                        r_errno = EINVAL;
                        return false;
                }

                return true;
        }

        bool close_file(std::string &path)
        {
                auto it = session_file_map.find(path);
                if (it == session_file_map.end()) {
                        ROS_ERROR_NAMED("ftp", "FTP:Close %s: not opened", path.c_str());
                        r_errno = EBADF;
                        return false;
                }

                op_state = OP::ACK;
                send_terminate_command(it->second);
                session_file_map.erase(it);
                return true;
        }

        void read_file_end() {
                ROS_DEBUG_NAMED("ftp", "FTP:Read done");
                go_idle(false);
        }

        bool read_file(std::string &path, size_t off, size_t len)
        {
                auto it = session_file_map.find(path);
                if (it == session_file_map.end()) {
                        ROS_ERROR_NAMED("ftp", "FTP:Read %s: not opened", path.c_str());
                        r_errno = EBADF;
                        return false;
                }

                op_state = OP::READ;
                active_session = it->second;
                read_size = len;
                read_offset = off;
                read_buffer.clear();
                if (read_buffer.capacity() < len ||
                                read_buffer.capacity() > len + MAX_RESERVE_DIFF) {
                        // reserve memory
                        read_buffer.reserve(len);
                }

                send_read_command();
                return true;
        }

        void write_file_end() {
                ROS_DEBUG_NAMED("ftp", "FTP:Write done");
                go_idle(false);
        }

        bool write_file(std::string &path, size_t off, V_FileData &data)
        {
                auto it = session_file_map.find(path);
                if (it == session_file_map.end()) {
                        ROS_ERROR_NAMED("ftp", "FTP:Write %s: not opened", path.c_str());
                        r_errno = EBADF;
                        return false;
                }

                op_state = OP::WRITE;
                active_session = it->second;
                write_offset = off;
                write_buffer = std::move(data);
                write_it = write_buffer.begin();

                send_write_command(write_bytes_to_copy());
                return true;
        }

        void remove_file(std::string &path) {
                op_state = OP::ACK;
                send_remove_command(path);
        }

        bool rename_(std::string &old_path, std::string &new_path) {
                op_state = OP::ACK;
                return send_rename_command(old_path, new_path);
        }

        void truncate_file(std::string &path, size_t length) {
                op_state = OP::ACK;
                send_truncate_command(path, length);
        }

        void create_directory(std::string &path) {
                op_state = OP::ACK;
                send_create_dir_command(path);
        }

        void remove_directory(std::string &path) {
                op_state = OP::ACK;
                send_remove_dir_command(path);
        }

        void checksum_crc32_file(std::string &path) {
                op_state = OP::CHECKSUM;
                checksum_crc32 = 0;
                send_calc_file_crc32_command(path);
        }

        static constexpr int compute_rw_timeout(size_t len) {
                return CHUNK_TIMEOUT_MS * (len / FTPRequest::DATA_MAXSZ + 1);
        }

        size_t write_bytes_to_copy() {
                return std::min<size_t>(std::distance(write_it, write_buffer.end()),
                                FTPRequest::DATA_MAXSZ);
        }

        bool wait_completion(const int msecs)
        {
                std::unique_lock<std::mutex> lock(cond_mutex);

                bool is_timedout = cond.wait_for(lock, std::chrono::milliseconds(msecs))
                                == std::cv_status::timeout;

                if (is_timedout) {
                        // If timeout occurs don't forget to reset state
                        op_state = OP::IDLE;
                        r_errno = ETIMEDOUT;
                        return false;
                }
                else
                        // if go_idle() occurs before timeout
                        return !is_error;
        }

        /* -*- service callbacks -*- */

#define SERVICE_IDLE_CHECK()                            \
        if (op_state != OP::IDLE) {                     \
                ROS_ERROR_NAMED("ftp", "FTP: Busy");    \
                return false;                           \
        }

        bool list_cb(mavros_msgs::FileList::Request &req,
                        mavros_msgs::FileList::Response &res)
        {
                SERVICE_IDLE_CHECK();

                list_directory(req.dir_path);
                res.success = wait_completion(LIST_TIMEOUT_MS);
                res.r_errno = r_errno;
                if (res.success) {
                        res.list = std::move(list_entries);
                        list_entries.clear();   // not shure that it's needed
                }

                return true;
        }

        bool open_cb(mavros_msgs::FileOpen::Request &req,
                        mavros_msgs::FileOpen::Response &res)
        {
                SERVICE_IDLE_CHECK();

                // only one session per file
                auto it = session_file_map.find(req.file_path);
                if (it != session_file_map.end()) {
                        ROS_ERROR_NAMED("ftp", "FTP: File %s: already opened",
                                        req.file_path.c_str());
                        return false;
                }

                res.success = open_file(req.file_path, req.mode);
                if (res.success) {
                        res.success = wait_completion(OPEN_TIMEOUT_MS);
                        res.size = open_size;
                }
                res.r_errno = r_errno;

                return true;
        }

        bool close_cb(mavros_msgs::FileClose::Request &req,
                        mavros_msgs::FileClose::Response &res)
        {
                SERVICE_IDLE_CHECK();

                res.success = close_file(req.file_path);
                if (res.success) {
                        res.success = wait_completion(OPEN_TIMEOUT_MS);
                }
                res.r_errno = r_errno;

                return true;
        }

        bool read_cb(mavros_msgs::FileRead::Request &req,
                        mavros_msgs::FileRead::Response &res)
        {
                SERVICE_IDLE_CHECK();

                res.success = read_file(req.file_path, req.offset, req.size);
                if (res.success)
                        res.success = wait_completion(compute_rw_timeout(req.size));
                if (res.success) {
                        res.data = std::move(read_buffer);
                        read_buffer.clear();    // same as for list_entries
                }
                res.r_errno = r_errno;

                return true;
        }

        bool write_cb(mavros_msgs::FileWrite::Request &req,
                        mavros_msgs::FileWrite::Response &res)
        {
                SERVICE_IDLE_CHECK();

                const size_t data_size = req.data.size();
                res.success = write_file(req.file_path, req.offset, req.data);
                if (res.success) {
                        res.success = wait_completion(compute_rw_timeout(data_size));
                }
                write_buffer.clear();
                res.r_errno = r_errno;

                return true;
        }

        bool remove_cb(mavros_msgs::FileRemove::Request &req,
                        mavros_msgs::FileRemove::Response &res)
        {
                SERVICE_IDLE_CHECK();

                remove_file(req.file_path);
                res.success = wait_completion(OPEN_TIMEOUT_MS);
                res.r_errno = r_errno;

                return true;
        }

        bool rename_cb(mavros_msgs::FileRename::Request &req,
                        mavros_msgs::FileRename::Response &res)
        {
                SERVICE_IDLE_CHECK();

                res.success = rename_(req.old_path, req.new_path);
                if (res.success) {
                        res.success = wait_completion(OPEN_TIMEOUT_MS);
                }
                res.r_errno = r_errno;

                return true;
        }


        bool truncate_cb(mavros_msgs::FileTruncate::Request &req,
                        mavros_msgs::FileTruncate::Response &res)
        {
                SERVICE_IDLE_CHECK();

                // Note: emulated truncate() can take a while
                truncate_file(req.file_path, req.length);
                res.success = wait_completion(LIST_TIMEOUT_MS * 5);
                res.r_errno = r_errno;

                return true;
        }

        bool mkdir_cb(mavros_msgs::FileMakeDir::Request &req,
                        mavros_msgs::FileMakeDir::Response &res)
        {
                SERVICE_IDLE_CHECK();

                create_directory(req.dir_path);
                res.success = wait_completion(OPEN_TIMEOUT_MS);
                res.r_errno = r_errno;

                return true;
        }

        bool rmdir_cb(mavros_msgs::FileRemoveDir::Request &req,
                        mavros_msgs::FileRemoveDir::Response &res)
        {
                SERVICE_IDLE_CHECK();

                remove_directory(req.dir_path);
                res.success = wait_completion(OPEN_TIMEOUT_MS);
                res.r_errno = r_errno;

                return true;
        }

        bool checksum_cb(mavros_msgs::FileChecksum::Request &req,
                        mavros_msgs::FileChecksum::Response &res)
        {
                SERVICE_IDLE_CHECK();

                checksum_crc32_file(req.file_path);
                res.success = wait_completion(LIST_TIMEOUT_MS);
                res.crc32 = checksum_crc32;
                res.r_errno = r_errno;

                return true;
        }

#undef SERVICE_IDLE_CHECK

        bool reset_cb(std_srvs::Empty::Request &req,
                        std_srvs::Empty::Response &res)
        {
                send_reset();
                return true;
        }
};
}       // namespace std_plugins
}       // namespace mavros

#include <pluginlib/class_list_macros.h>
PLUGINLIB_EXPORT_CLASS(mavros::std_plugins::FTPPlugin, mavros::plugin::PluginBase)