ZLKMedia/srt/SrtTransport.cpp

#include "Util/onceToken.h"
#include "Util/mini.h"

#include <iterator>
#include <stdlib.h>

#include "Ack.hpp"
#include "Packet.hpp"
#include "SrtTransport.hpp"

namespace SRT {
#define SRT_FIELD "srt."
// srt 超时时间
const std::string kTimeOutSec = SRT_FIELD "timeoutSec";
// srt 单端口udp服务器
const std::string kPort = SRT_FIELD "port";
const std::string kLatencyMul = SRT_FIELD "latencyMul";
const std::string kPktBufSize = SRT_FIELD "pktBufSize";

static onceToken token([]() {
    mINI::Instance()[kTimeOutSec] = 5;
    mINI::Instance()[kPort] = 9000;
    mINI::Instance()[kLatencyMul] = 4;
    mINI::Instance()[kPktBufSize] = 8192;
});

static std::atomic<uint32_t> s_srt_socket_id_generate { 125 };
////////////  SrtTransport //////////////////////////
SrtTransport::SrtTransport(const EventPoller::Ptr &poller)
    : _poller(poller) {
    _start_timestamp = SteadyClock::now();
    _socket_id = s_srt_socket_id_generate.fetch_add(1);
    _pkt_recv_rate_context = std::make_shared<PacketRecvRateContext>(_start_timestamp);
    //_recv_rate_context = std::make_shared<RecvRateContext>(_start_timestamp);
    _estimated_link_capacity_context = std::make_shared<EstimatedLinkCapacityContext>(_start_timestamp);
}

SrtTransport::~SrtTransport() {
    TraceL << " ";
}

const EventPoller::Ptr &SrtTransport::getPoller() const {
    return _poller;
}

void SrtTransport::setSession(Session::Ptr session) {
    _history_sessions.emplace(session.get(), session);
    if (_selected_session) {
        InfoL << "srt network changed: " << _selected_session->get_peer_ip() << ":"
              << _selected_session->get_peer_port() << " -> " << session->get_peer_ip() << ":"
              << session->get_peer_port() << ", id:" << _selected_session->getIdentifier();
    }
    _selected_session = session;
}

const Session::Ptr &SrtTransport::getSession() const {
    return _selected_session;
}

void SrtTransport::switchToOtherTransport(uint8_t *buf, int len, uint32_t socketid, struct sockaddr_storage *addr) {
    BufferRaw::Ptr tmp = BufferRaw::create();
    struct sockaddr_storage tmp_addr = *addr;
    tmp->assign((char *)buf, len);
    auto trans = SrtTransportManager::Instance().getItem(std::to_string(socketid));
    if (trans) {
        trans->getPoller()->async([tmp, tmp_addr, trans] {
            trans->inputSockData((uint8_t *)tmp->data(), tmp->size(), (struct sockaddr_storage *)&tmp_addr);
        });
    }
}

void SrtTransport::createTimerForCheckAlive(){
    std::weak_ptr<SrtTransport> weak_self = std::static_pointer_cast<SrtTransport>(shared_from_this());
    auto timeoutSec = getTimeOutSec();
    _timer = std::make_shared<Timer>(
         timeoutSec/ 2,
        [weak_self,timeoutSec]() {
            auto strong_self = weak_self.lock();
            if (!strong_self) {
                return false;
            }
            if (strong_self->_alive_ticker.elapsedTime() > timeoutSec * 1000) {
                strong_self->onShutdown(SockException(Err_timeout, "接收srt数据超时"));
            }
            return true;
        },
        getPoller());
}

void SrtTransport::inputSockData(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    _alive_ticker.resetTime();
    if(!_timer){
        createTimerForCheckAlive();
    }
    using srt_control_handler = void (SrtTransport::*)(uint8_t * buf, int len, struct sockaddr_storage *addr);
    static std::unordered_map<uint16_t, srt_control_handler> s_control_functions;
    static onceToken token([]() {
        s_control_functions.emplace(ControlPacket::HANDSHAKE, &SrtTransport::handleHandshake);
        s_control_functions.emplace(ControlPacket::KEEPALIVE, &SrtTransport::handleKeeplive);
        s_control_functions.emplace(ControlPacket::ACK, &SrtTransport::handleACK);
        s_control_functions.emplace(ControlPacket::NAK, &SrtTransport::handleNAK);
        s_control_functions.emplace(ControlPacket::CONGESTIONWARNING, &SrtTransport::handleCongestionWarning);
        s_control_functions.emplace(ControlPacket::SHUTDOWN, &SrtTransport::handleShutDown);
        s_control_functions.emplace(ControlPacket::ACKACK, &SrtTransport::handleACKACK);
        s_control_functions.emplace(ControlPacket::DROPREQ, &SrtTransport::handleDropReq);
        s_control_functions.emplace(ControlPacket::PEERERROR, &SrtTransport::handlePeerError);
        s_control_functions.emplace(ControlPacket::USERDEFINEDTYPE, &SrtTransport::handleUserDefinedType);
    });
    _now = SteadyClock::now();
    // 处理srt数据
    if (DataPacket::isDataPacket(buf, len)) {
        uint32_t socketId = DataPacket::getSocketID(buf, len);
        if (socketId == _socket_id) {
            if(_handleshake_timer){
                _handleshake_timer.reset();
            }
            _pkt_recv_rate_context->inputPacket(_now,len+UDP_HDR_SIZE);
            //_recv_rate_context->inputPacket(_now, len);

            handleDataPacket(buf, len, addr);
            checkAndSendAckNak();
        } else {
            WarnL<<"DataPacket switch to other transport: "<<socketId;
            switchToOtherTransport(buf, len, socketId, addr);
        }
    } else {
        if (ControlPacket::isControlPacket(buf, len)) {
            uint32_t socketId = ControlPacket::getSocketID(buf, len);
            uint16_t type = ControlPacket::getControlType(buf, len);
            if (type != ControlPacket::HANDSHAKE && socketId != _socket_id && _socket_id != 0) {
                // socket id not same
                WarnL<<"ControlPacket: "<< (int)type <<" switch to other transport: "<<socketId;
                switchToOtherTransport(buf, len, socketId, addr);
                return;
            }
            
            //_pkt_recv_rate_context->inputPacket(_now,len);
            //_estimated_link_capacity_context->inputPacket(_now);
            //_recv_rate_context->inputPacket(_now, len);

            auto it = s_control_functions.find(type);
            if (it == s_control_functions.end()) {
                WarnL << " not support type ignore" << ControlPacket::getControlType(buf, len);
                return;
            } else {
                (this->*(it->second))(buf, len, addr);
            }
            if(_is_handleshake_finished && isPusher()){
                checkAndSendAckNak();
            }
        } else {
            // not reach
            WarnL << "not reach this";
        }
    }
}

void SrtTransport::handleHandshakeInduction(HandshakePacket &pkt, struct sockaddr_storage *addr) {
    // Induction Phase
    if (_handleshake_res) {
        if(_handleshake_res->handshake_type == HandshakePacket::HS_TYPE_INDUCTION){
            if(pkt.srt_socket_id == _handleshake_res->dst_socket_id){
                TraceL << getIdentifier() <<" Induction repeate "<<SockUtil::inet_ntoa((struct sockaddr *)addr) << ":" << SockUtil::inet_port((struct sockaddr *)addr);
                sendControlPacket(_handleshake_res, true);
            }else{
                TraceL << getIdentifier() <<" new connection fron client "<<SockUtil::inet_ntoa((struct sockaddr *)addr) << ":" << SockUtil::inet_port((struct sockaddr *)addr);
                onShutdown(SockException(Err_other, "client new connection"));
            }
            return;
        }else if(_handleshake_res->handshake_type == HandshakePacket::HS_TYPE_CONCLUSION){
            if(_handleshake_res->dst_socket_id != pkt.srt_socket_id){
                TraceL << getIdentifier() <<" new connection fron client "<<SockUtil::inet_ntoa((struct sockaddr *)addr) << ":" << SockUtil::inet_port((struct sockaddr *)addr);
                onShutdown(SockException(Err_other, "client new connection"));
            }
            return;
        }else{
            WarnL<<"not reach this";
        }
        return;
    }else{
         TraceL << getIdentifier() <<" Induction from "<<SockUtil::inet_ntoa((struct sockaddr *)addr) << ":" << SockUtil::inet_port((struct sockaddr *)addr);
    }
    _induction_ts = _now;
    _start_timestamp = _now;
    _init_seq_number = pkt.initial_packet_sequence_number;
    _max_window_size = pkt.max_flow_window_size;
    _mtu = pkt.mtu;

    _last_pkt_seq = _init_seq_number - 1;
    _estimated_link_capacity_context->setLastSeq(_last_pkt_seq);

    _peer_socket_id = pkt.srt_socket_id;
    HandshakePacket::Ptr res = std::make_shared<HandshakePacket>();
    res->dst_socket_id = _peer_socket_id;
    res->timestamp = DurationCountMicroseconds(_start_timestamp.time_since_epoch());
    res->mtu = _mtu;
    res->max_flow_window_size = _max_window_size;
    res->initial_packet_sequence_number = _init_seq_number;
    res->version = 5;
    res->encryption_field = HandshakePacket::NO_ENCRYPTION;
    res->extension_field = 0x4A17;
    res->handshake_type = HandshakePacket::HS_TYPE_INDUCTION;
    res->srt_socket_id = _peer_socket_id;
    res->syn_cookie = HandshakePacket::generateSynCookie(addr, _start_timestamp);
    _sync_cookie = res->syn_cookie;
    memcpy(res->peer_ip_addr, pkt.peer_ip_addr, sizeof(pkt.peer_ip_addr) * sizeof(pkt.peer_ip_addr[0]));
    _handleshake_res = res;
    res->storeToData();

    registerSelfHandshake();
    sendControlPacket(res, true);
    _handleshake_timer = std::make_shared<Timer>(0.2,[this]()->bool{
        sendControlPacket(_handleshake_res, true);
        return true;
    },getPoller());
}

void SrtTransport::handleHandshakeConclusion(HandshakePacket &pkt, struct sockaddr_storage *addr) {
    if (!_handleshake_res) {
        ErrorL << "must Induction Phase for handleshake ";
        return;
    }

    if (_handleshake_res->handshake_type == HandshakePacket::HS_TYPE_INDUCTION) {
        // first
        HSExtMessage::Ptr req;
        HSExtStreamID::Ptr sid;
        uint32_t srt_flag = 0xbf;
        uint16_t delay = DurationCountMicroseconds(_now - _induction_ts) * getLatencyMul() / 1000;
        if (delay <= 120) {
            delay = 120;
        }
        for (auto& ext : pkt.ext_list) {
            // TraceL << getIdentifier() << " ext " << ext->dump();
            if (!req) {
                req = std::dynamic_pointer_cast<HSExtMessage>(ext);
            }
            if (!sid) {
                sid = std::dynamic_pointer_cast<HSExtStreamID>(ext);
            }
        }
        if (sid) {
            _stream_id = sid->streamid;
        }
        if (req) {
            if (req->srt_flag != srt_flag) {
                WarnL << "  flag " << req->srt_flag;
            }
            srt_flag = req->srt_flag;
            delay = delay <= req->recv_tsbpd_delay ? req->recv_tsbpd_delay : delay;
        }
        TraceL << getIdentifier() << " CONCLUSION Phase from"<<SockUtil::inet_ntoa((struct sockaddr *)addr) << ":" << SockUtil::inet_port((struct sockaddr *)addr);;
        HandshakePacket::Ptr res = std::make_shared<HandshakePacket>();
        res->dst_socket_id = _peer_socket_id;
        res->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
        res->mtu = _mtu;
        res->max_flow_window_size = _max_window_size;
        res->initial_packet_sequence_number = _init_seq_number;
        res->version = 5;
        res->encryption_field = HandshakePacket::NO_ENCRYPTION;
        res->extension_field = HandshakePacket::HS_EXT_FILED_HSREQ;
        res->handshake_type = HandshakePacket::HS_TYPE_CONCLUSION;
        res->srt_socket_id = _socket_id;
        res->syn_cookie = 0;
        res->assignPeerIP(addr);
        HSExtMessage::Ptr ext = std::make_shared<HSExtMessage>();
        ext->extension_type = HSExt::SRT_CMD_HSRSP;
        ext->srt_version = srtVersion(1, 5, 0);
        ext->srt_flag = srt_flag;
        ext->recv_tsbpd_delay = ext->send_tsbpd_delay = delay;
        res->ext_list.push_back(std::move(ext));
        res->storeToData();
        _handleshake_res = res;
        unregisterSelfHandshake();
        registerSelf();
        sendControlPacket(res, true);
        TraceL << " buf size = " << res->max_flow_window_size << " init seq =" << _init_seq_number
               << " latency=" << delay;
        _recv_buf = std::make_shared<PacketRecvQueue>(getPktBufSize(), _init_seq_number, delay * 1e3,srt_flag);
        _send_buf = std::make_shared<PacketSendQueue>(getPktBufSize(), delay * 1e3,srt_flag);
        _send_packet_seq_number = _init_seq_number;
        _buf_delay = delay;
        onHandShakeFinished(_stream_id, addr);

        if(!isPusher()){
            _handleshake_timer.reset();
        }
    } else {
        if(_handleshake_res->handshake_type == HandshakePacket::HS_TYPE_CONCLUSION){
            if(_handleshake_res->dst_socket_id != pkt.srt_socket_id){
                TraceL << getIdentifier() <<" new connection fron client "<<SockUtil::inet_ntoa((struct sockaddr *)addr) << ":" << SockUtil::inet_port((struct sockaddr *)addr);
                onShutdown(SockException(Err_other, "client new connection"));
            }else{
                TraceL << getIdentifier() <<" CONCLUSION repeate "<<SockUtil::inet_ntoa((struct sockaddr *)addr) << ":" << SockUtil::inet_port((struct sockaddr *)addr);
                sendControlPacket(_handleshake_res, true);
            }

        }else{
            WarnL<<"not reach this";
        }
        return;
        
    }
    _last_ack_pkt_seq = _init_seq_number;
}

void SrtTransport::handleHandshake(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    HandshakePacket pkt;
    if(!pkt.loadFromData(buf, len)){
        WarnL<<"is not vaild HandshakePacket";
        return;
    }

    if (pkt.handshake_type == HandshakePacket::HS_TYPE_INDUCTION) {
        handleHandshakeInduction(pkt, addr);
    } else if (pkt.handshake_type == HandshakePacket::HS_TYPE_CONCLUSION) {
        handleHandshakeConclusion(pkt, addr);
    } else {
        WarnL << " not support handshake type = " << pkt.handshake_type;
        WarnL <<pkt.dump();
    }
    _ack_ticker.resetTime(_now);
    _nak_ticker.resetTime(_now);
}

void SrtTransport::handleKeeplive(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    // TraceL;
    sendKeepLivePacket();
}

void SrtTransport::sendKeepLivePacket() {
    KeepLivePacket::Ptr pkt = std::make_shared<KeepLivePacket>();
    pkt->dst_socket_id = _peer_socket_id;
    pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
    pkt->storeToData();
    sendControlPacket(pkt, true);
}

void SrtTransport::handleACK(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    // TraceL;
    ACKPacket ack;
    if (!ack.loadFromData(buf, len)) {
        return;
    }

    ACKACKPacket::Ptr pkt = std::make_shared<ACKACKPacket>();
    pkt->dst_socket_id = _peer_socket_id;
    pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
    pkt->ack_number = ack.ack_number;
    pkt->storeToData();
    _send_buf->drop(ack.last_ack_pkt_seq_number);
    sendControlPacket(pkt, true);
    // TraceL<<"ack number "<<ack.ack_number;
}

void SrtTransport::sendMsgDropReq(uint32_t first, uint32_t last) {
    MsgDropReqPacket::Ptr pkt = std::make_shared<MsgDropReqPacket>();
    pkt->dst_socket_id = _peer_socket_id;
    pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
    pkt->first_pkt_seq_num = first;
    pkt->last_pkt_seq_num = last;
    pkt->storeToData();
    sendControlPacket(pkt, true);
}

void SrtTransport::handleNAK(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    // TraceL;
    NAKPacket pkt;
    pkt.loadFromData(buf, len);
    bool empty = false;
    bool flush = false;

    for (auto& it : pkt.lost_list) {
        if (pkt.lost_list.back() == it) {
            flush = true;
        }
        empty = true;
        auto re_list = _send_buf->findPacketBySeq(it.first, it.second - 1);
        for (auto& pkt : re_list) {
            pkt->R = 1;
            pkt->storeToHeader();
            sendPacket(pkt, flush);
            empty = false;
        }
        if (empty) {
            sendMsgDropReq(it.first, it.second - 1);
        }
    }
}

void SrtTransport::handleCongestionWarning(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    TraceL;
}

void SrtTransport::handleShutDown(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    TraceL;
    onShutdown(SockException(Err_shutdown, "peer close connection"));
}

void SrtTransport::handleDropReq(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    MsgDropReqPacket pkt;
    pkt.loadFromData(buf, len);
    std::list<DataPacket::Ptr> list;
    // TraceL<<"drop "<<pkt.first_pkt_seq_num<<" last "<<pkt.last_pkt_seq_num;
    _recv_buf->drop(pkt.first_pkt_seq_num, pkt.last_pkt_seq_num, list);
    //checkAndSendAckNak();
    if (list.empty()) {
        return;
    }
    // uint32_t max_seq = 0;
    for (auto& data : list) {
        // max_seq = data->packet_seq_number;
        if (_last_pkt_seq + 1 != data->packet_seq_number) {
            TraceL << "pkt lost " << _last_pkt_seq + 1 << "->" << data->packet_seq_number;
        }
        _last_pkt_seq = data->packet_seq_number;
        onSRTData(std::move(data));
    }
    /*
    _recv_nack.drop(max_seq);

    auto lost = _recv_buf->getLostSeq();
    _recv_nack.update(_now, lost);
    lost.clear();
    _recv_nack.getLostList(_now, _rtt, _rtt_variance, lost);
    if (!lost.empty()) {
        sendNAKPacket(lost);
        // TraceL << "check lost send nack";
    }
    */
}
void SrtTransport::checkAndSendAckNak(){
    auto nak_interval = (_rtt + _rtt_variance * 4) / 2;
    if (nak_interval <= 20 * 1000) {
        nak_interval = 20 * 1000;
    }
    if (_nak_ticker.elapsedTime(_now) > nak_interval) {
        auto lost = _recv_buf->getLostSeq();
        if (!lost.empty()) {
            sendNAKPacket(lost);
        }
        _nak_ticker.resetTime(_now);
    }

    if (_ack_ticker.elapsedTime(_now) > 10 * 1000) {
        _light_ack_pkt_count = 0;
        _ack_ticker.resetTime(_now);
        // send a ack per 10 ms for receiver
        if(_last_ack_pkt_seq != _recv_buf->getExpectedSeq()){
            //TraceL<<"send a ack packet";
            sendACKPacket();
        }else{
            //TraceL<<" ignore repeate ack packet";
        }
        
    } else {
        if (_light_ack_pkt_count >= 64) {
            // for high bitrate stream send light ack
            // TODO
            sendLightACKPacket();
            TraceL << "send light ack";
        }
        _light_ack_pkt_count = 0;
    }
    _light_ack_pkt_count++;
}
void SrtTransport::handleUserDefinedType(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    TraceL;
}

void SrtTransport::handleACKACK(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    // TraceL;
    ACKACKPacket::Ptr pkt = std::make_shared<ACKACKPacket>();
    pkt->loadFromData(buf, len);

    if(_ack_send_timestamp.find(pkt->ack_number)!=_ack_send_timestamp.end()){
        uint32_t rtt = DurationCountMicroseconds(_now - _ack_send_timestamp[pkt->ack_number]);
        _rtt_variance = (3 * _rtt_variance + abs((long)_rtt - (long)rtt)) / 4;
        _rtt = (7 * rtt + _rtt) / 8;
        // TraceL<<" rtt:"<<_rtt<<" rtt variance:"<<_rtt_variance;
        _ack_send_timestamp.erase(pkt->ack_number);

        if(_last_recv_ackack_seq_num < pkt->ack_number){
            _last_recv_ackack_seq_num = pkt->ack_number;
        }else{
            if((_last_recv_ackack_seq_num-pkt->ack_number)>(MAX_TS>>1)){
                _last_recv_ackack_seq_num = pkt->ack_number;
            }
        }

        if(_ack_send_timestamp.size()>1000){
            // clear data
            for(auto it = _ack_send_timestamp.begin(); it != _ack_send_timestamp.end();){
                if(DurationCountMicroseconds(_now-it->second)>5e6){
                    // 超过五秒没有ackack 丢弃
                    it = _ack_send_timestamp.erase(it);
                }else{
                    it++;
                }
            }
        }

    }
}

void SrtTransport::handlePeerError(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    TraceL;
}

void SrtTransport::sendACKPacket() {
    uint32_t recv_rate = 0;

    ACKPacket::Ptr pkt = std::make_shared<ACKPacket>();
    pkt->dst_socket_id = _peer_socket_id;
    pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
    pkt->ack_number = ++_ack_number_count;
    pkt->last_ack_pkt_seq_number = _recv_buf->getExpectedSeq();
    pkt->rtt = _rtt;
    pkt->rtt_variance = _rtt_variance;
    pkt->available_buf_size = _recv_buf->getAvailableBufferSize();
    pkt->pkt_recv_rate = _pkt_recv_rate_context->getPacketRecvRate(recv_rate);
    pkt->estimated_link_capacity = _estimated_link_capacity_context->getEstimatedLinkCapacity();
    pkt->recv_rate = recv_rate;
    if(0){
        TraceL<<pkt->pkt_recv_rate<<" pkt/s "<<recv_rate<<" byte/s "<<pkt->estimated_link_capacity<<" pkt/s (cap) "<<pkt->available_buf_size<<" available buf";
        //TraceL<<_pkt_recv_rate_context->dump();
        //TraceL<<"recv estimated:";
        //TraceL<< _pkt_recv_rate_context->dump();
        //TraceL<<"recv queue:";
        //TraceL<<_recv_buf->dump();
    }
    if(pkt->available_buf_size<2){
        pkt->available_buf_size = 2;
    }
    pkt->storeToData();
    _ack_send_timestamp[pkt->ack_number] = _now;
    _last_ack_pkt_seq = pkt->last_ack_pkt_seq_number;
    sendControlPacket(pkt, true);
    // TraceL<<"send  ack "<<pkt->dump();
    // TraceL<<_recv_buf->dump();
}

void SrtTransport::sendLightACKPacket() {
    ACKPacket::Ptr pkt = std::make_shared<ACKPacket>();

    pkt->dst_socket_id = _peer_socket_id;
    pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
    pkt->ack_number = 0;
    pkt->last_ack_pkt_seq_number = _recv_buf->getExpectedSeq();
    pkt->rtt = 0;
    pkt->rtt_variance = 0;
    pkt->available_buf_size = 0;
    pkt->pkt_recv_rate = 0;
    pkt->estimated_link_capacity = 0;
    pkt->recv_rate = 0;
    pkt->storeToData();
    _last_ack_pkt_seq = pkt->last_ack_pkt_seq_number;
    sendControlPacket(pkt, true);
    TraceL << "send  ack " << pkt->dump();
}

void SrtTransport::sendNAKPacket(std::list<PacketQueue::LostPair> &lost_list) {
    NAKPacket::Ptr pkt = std::make_shared<NAKPacket>();
    std::list<PacketQueue::LostPair> tmp;
    auto size = NAKPacket::getCIFSize(lost_list);
    size_t paylaod_size = getPayloadSize();
    if (size > paylaod_size) {
        WarnL << "loss report cif size " << size;
        size_t num = paylaod_size / 8;

        size_t msgNum = (lost_list.size() + num - 1) / num;
        decltype(lost_list.begin()) cur, next;
        for (size_t i = 0; i < msgNum; ++i) {
            cur = lost_list.begin();
            std::advance(cur, i * num);

            if (i == msgNum - 1) {
                next = lost_list.end();
            } else {
                next = lost_list.begin();
                std::advance(next, (i + 1) * num);
            }
            tmp.assign(cur, next);
            pkt->dst_socket_id = _peer_socket_id;
            pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
            pkt->lost_list = tmp;
            pkt->storeToData();
            sendControlPacket(pkt, true);
        }

    } else {
        pkt->dst_socket_id = _peer_socket_id;
        pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
        pkt->lost_list = lost_list;
        pkt->storeToData();
        sendControlPacket(pkt, true);
    }

    // TraceL<<"send NAK "<<pkt->dump();
}

void SrtTransport::sendShutDown() {
    ShutDownPacket::Ptr pkt = std::make_shared<ShutDownPacket>();
    pkt->dst_socket_id = _peer_socket_id;
    pkt->timestamp = DurationCountMicroseconds(_now - _start_timestamp);
    pkt->storeToData();
    sendControlPacket(pkt, true);
}

void SrtTransport::handleDataPacket(uint8_t *buf, int len, struct sockaddr_storage *addr) {
    DataPacket::Ptr pkt = std::make_shared<DataPacket>();
    pkt->loadFromData(buf, len);

    _estimated_link_capacity_context->inputPacket(_now,pkt);

    std::list<DataPacket::Ptr> list;
    //TraceL<<" seq="<< pkt->packet_seq_number<<" ts="<<pkt->timestamp<<" size="<<pkt->payloadSize()<<\
    //" PP="<<(int)pkt->PP<<" O="<<(int)pkt->O<<" kK="<<(int)pkt->KK<<" R="<<(int)pkt->R;
    _recv_buf->inputPacket(pkt, list);
    if (list.empty()) {
        // when no data ok send nack to sender immediately
    } else {
        // uint32_t last_seq;
        for (auto& data : list) {
            // last_seq = data->packet_seq_number;
            if (_last_pkt_seq + 1 != data->packet_seq_number) {
                TraceL << "pkt lost " << _last_pkt_seq + 1 << "->" << data->packet_seq_number;
            }
            _last_pkt_seq = data->packet_seq_number;
            onSRTData(std::move(data));
        }

        //_recv_nack.drop(last_seq);
    }
    /*
    auto lost = _recv_buf->getLostSeq();
    _recv_nack.update(_now, lost);
    lost.clear();
    _recv_nack.getLostList(_now, _rtt, _rtt_variance, lost);
    if (!lost.empty()) {
        // TraceL << "check lost send nack immediately";
        sendNAKPacket(lost);
    }
    */
   /*
    auto nak_interval = (_rtt + _rtt_variance * 4) / 2;
    if (nak_interval <= 20 * 1000) {
        nak_interval = 20 * 1000;
    }

    if (_nak_ticker.elapsedTime(_now) > nak_interval) {
        // Periodic NAK reports
        auto lost = _recv_buf->getLostSeq();
        if (!lost.empty()) {
            sendNAKPacket(lost);
            // TraceL<<"send NAK";
        } else {
            // TraceL<<"lost is empty";
        }
        _nak_ticker.resetTime(_now);
    }

    if (_ack_ticker.elapsedTime(_now) > 10 * 1000) {
        _light_ack_pkt_count = 0;
        _ack_ticker.resetTime(_now);
        // send a ack per 10 ms for receiver
        sendACKPacket();
    } else {
        if (_light_ack_pkt_count >= 64) {
            // for high bitrate stream send light ack
            // TODO
            sendLightACKPacket();
            TraceL << "send light ack";
        }
        _light_ack_pkt_count = 0;
    }
    _light_ack_pkt_count++;
    */
    // bufCheckInterval();
}

void SrtTransport::sendDataPacket(DataPacket::Ptr pkt, char *buf, int len, bool flush) {
    pkt->storeToData((uint8_t *)buf, len);
    sendPacket(pkt, flush);
    _send_buf->inputPacket(pkt);
}

void SrtTransport::sendControlPacket(ControlPacket::Ptr pkt, bool flush) {
    sendPacket(pkt, flush);
}

void SrtTransport::sendPacket(Buffer::Ptr pkt, bool flush) {
    if (_selected_session) {
        auto tmp = _packet_pool.obtain2();
        tmp->assign(pkt->data(), pkt->size());
        _selected_session->setSendFlushFlag(flush);
        _selected_session->send(std::move(tmp));
    } else {
        WarnL << "not reach this";
    }
}

std::string SrtTransport::getIdentifier() {
    return _selected_session ? _selected_session->getIdentifier() : "";
}

void SrtTransport::registerSelfHandshake() {
    SrtTransportManager::Instance().addHandshakeItem(std::to_string(_sync_cookie), shared_from_this());
}

void SrtTransport::unregisterSelfHandshake() {
    if (_sync_cookie == 0) {
        return;
    }
    SrtTransportManager::Instance().removeHandshakeItem(std::to_string(_sync_cookie));
}

void SrtTransport::registerSelf() {
    if (_socket_id == 0) {
        return;
    }
    SrtTransportManager::Instance().addItem(std::to_string(_socket_id), shared_from_this());
}

void SrtTransport::unregisterSelf() {
    SrtTransportManager::Instance().removeItem(std::to_string(_socket_id));
}

void SrtTransport::onShutdown(const SockException &ex) {
    sendShutDown();
    WarnL << ex.what();
    unregisterSelfHandshake();
    unregisterSelf();
    for (auto &pr : _history_sessions) {
        auto session = pr.second.lock();
        if (session) {
            session->shutdown(ex);
        }
    }
}

size_t SrtTransport::getPayloadSize() {
    size_t ret = (_mtu - 28 - 16) / 188 * 188;
    return ret;
}

void SrtTransport::onSendTSData(const Buffer::Ptr &buffer, bool flush) {
    // TraceL;
    DataPacket::Ptr pkt;
    size_t payloadSize = getPayloadSize();
    size_t size = buffer->size();
    char *ptr = buffer->data();
    char *end = buffer->data() + size;

    while (ptr < end && size >= payloadSize) {
        pkt = std::make_shared<DataPacket>();
        pkt->f = 0;
        pkt->packet_seq_number = _send_packet_seq_number & 0x7fffffff;
        _send_packet_seq_number = (_send_packet_seq_number + 1) & 0x7fffffff;
        pkt->PP = 3;
        pkt->O = 0;
        pkt->KK = 0;
        pkt->R = 0;
        pkt->msg_number = _send_msg_number++;
        pkt->dst_socket_id = _peer_socket_id;
        pkt->timestamp = DurationCountMicroseconds(SteadyClock::now() - _start_timestamp);
        sendDataPacket(pkt, ptr, (int)payloadSize, flush);
        ptr += payloadSize;
        size -= payloadSize;
    }

    if (size > 0 && ptr < end) {
        pkt = std::make_shared<DataPacket>();
        pkt->f = 0;
        pkt->packet_seq_number = _send_packet_seq_number & 0x7fffffff;
        _send_packet_seq_number = (_send_packet_seq_number + 1) & 0x7fffffff;
        pkt->PP = 3;
        pkt->O = 0;
        pkt->KK = 0;
        pkt->R = 0;
        pkt->msg_number = _send_msg_number++;
        pkt->dst_socket_id = _peer_socket_id;
        pkt->timestamp = DurationCountMicroseconds(SteadyClock::now() - _start_timestamp);
        sendDataPacket(pkt, ptr, (int)size, flush);
    }
}

////////////  SrtTransportManager //////////////////////////

SrtTransportManager &SrtTransportManager::Instance() {
    static SrtTransportManager s_instance;
    return s_instance;
}

void SrtTransportManager::addItem(const std::string &key, const SrtTransport::Ptr &ptr) {
    std::lock_guard<std::mutex> lck(_mtx);
    _map[key] = ptr;
}

SrtTransport::Ptr SrtTransportManager::getItem(const std::string &key) {
    if (key.empty()) {
        return nullptr;
    }
    std::lock_guard<std::mutex> lck(_mtx);
    auto it = _map.find(key);
    if (it == _map.end()) {
        return nullptr;
    }
    return it->second.lock();
}

void SrtTransportManager::removeItem(const std::string &key) {
    std::lock_guard<std::mutex> lck(_mtx);
    _map.erase(key);
}

void SrtTransportManager::addHandshakeItem(const std::string &key, const SrtTransport::Ptr &ptr) {
    std::lock_guard<std::mutex> lck(_handshake_mtx);
    _handshake_map[key] = ptr;
}

void SrtTransportManager::removeHandshakeItem(const std::string &key) {
    std::lock_guard<std::mutex> lck(_handshake_mtx);
    _handshake_map.erase(key);
}

SrtTransport::Ptr SrtTransportManager::getHandshakeItem(const std::string &key) {
    if (key.empty()) {
        return nullptr;
    }
    std::lock_guard<std::mutex> lck(_handshake_mtx);
    auto it = _handshake_map.find(key);
    if (it == _handshake_map.end()) {
        return nullptr;
    }
    return it->second.lock();
}

} // namespace SRT