Peter M. Groen / FlashMQ

#include "client.h"

#include <cstring>
#include <sstream>
#include <iostream>
#include <cassert>

#include "logger.h"

Client::Client(int fd, ThreadData_p threadData, SSL *ssl, bool websocket, std::shared_ptr<Settings> settings, bool fuzzMode) :
    fd(fd),
    fuzzMode(fuzzMode),
    initialBufferSize(settings->clientInitialBufferSize), // The client is constructed in the main thread, so we need to use its settings copy
    maxPacketSize(settings->maxPacketSize), // Same as initialBufferSize comment.
    ioWrapper(ssl, websocket, initialBufferSize, this),
    readbuf(initialBufferSize),
    writebuf(initialBufferSize),
    threadData(threadData)
{
    int flags = fcntl(fd, F_GETFL);
    fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}

Client::~Client()
{
    // Will payload can be empty, apparently.
    if (!will_topic.empty())
    {
        std::shared_ptr<SubscriptionStore> &store = getThreadData()->getSubscriptionStore();

        Publish will(will_topic, will_payload, will_qos);
        will.retain = will_retain;
        const MqttPacket willPacket(will);

        store->queuePacketAtSubscribers(will_topic, willPacket);
    }

    if (disconnectReason.empty())
        disconnectReason = "not specified";

    logger->logf(LOG_NOTICE, "Removing client '%s'. Reason(s): %s", repr().c_str(), disconnectReason.c_str());
    if (epoll_ctl(threadData->epollfd, EPOLL_CTL_DEL, fd, NULL) != 0)
        logger->logf(LOG_ERR, "Removing fd %d of client '%s' from epoll produced error: %s", fd, repr().c_str(), strerror(errno));
    close(fd);
}

bool Client::isSslAccepted() const
{
    return ioWrapper.isSslAccepted();
}

bool Client::isSsl() const
{
    return ioWrapper.isSsl();
}

bool Client::getSslReadWantsWrite() const
{
    return ioWrapper.getSslReadWantsWrite();
}

bool Client::getSslWriteWantsRead() const
{
    return ioWrapper.getSslWriteWantsRead();
}

void Client::startOrContinueSslAccept()
{
    ioWrapper.startOrContinueSslAccept();
}

// Causes future activity on the client to cause a disconnect.
void Client::markAsDisconnecting()
{
    if (disconnecting)
        return;

    disconnecting = true;
}

// false means any kind of error we want to get rid of the client for.
bool Client::readFdIntoBuffer()
{
    if (disconnecting)
        return false;

    IoWrapResult error = IoWrapResult::Success;
    int n = 0;
    while (readbuf.freeSpace() > 0 && (n = ioWrapper.readWebsocketAndOrSsl(fd, readbuf.headPtr(), readbuf.maxWriteSize(), &error)) != 0)
    {
        if (n > 0)
        {
            readbuf.advanceHead(n);
        }

        if (error == IoWrapResult::Interrupted)
            continue;
        if (error == IoWrapResult::Wouldblock)
            break;

        // Make sure we either always have enough space for a next call of this method, or stop reading the fd.
        if (readbuf.freeSpace() == 0)
        {
            if (readbuf.getSize() * 2 < maxPacketSize)
            {
                readbuf.doubleSize();
            }
            else
            {
                setReadyForReading(false);
                break;
            }
        }
    }

    if (error == IoWrapResult::Disconnected)
    {
        return false;
    }

    lastActivity = time(NULL);
    if (session)
        session->touch(lastActivity);

    return true;
}

void Client::writeText(const std::string &text)
{
    assert(ioWrapper.isWebsocket());
    assert(ioWrapper.getWebsocketState() == WebsocketState::NotUpgraded);

    // Not necessary, because at this point, no other threads write to this client, but including for clarity.
    std::lock_guard<std::mutex> locker(writeBufMutex);

    writebuf.ensureFreeSpace(text.size());
    writebuf.write(text.c_str(), text.length());

    setReadyForWriting(true);
}

void Client::writeMqttPacket(const MqttPacket &packet)
{
    std::lock_guard<std::mutex> locker(writeBufMutex);

    // We have to allow big packets, yet don't allow a slow loris subscriber to grow huge write buffers. This
    // could be enhanced a lot, but it's a start.
    const uint32_t growBufMaxTo = std::min<int>(packet.getSizeIncludingNonPresentHeader() * 1000, maxPacketSize);

    // Grow as far as we can. We have to make room for one MQTT packet.
    writebuf.ensureFreeSpace(packet.getSizeIncludingNonPresentHeader(), growBufMaxTo);

    // And drop a publish when it doesn't fit, even after resizing. This means we do allow pings. And
    // QoS packet are queued and limited elsewhere.
    if (packet.packetType == PacketType::PUBLISH && packet.getQos() == 0 && packet.getSizeIncludingNonPresentHeader() > writebuf.freeSpace())
    {
        return;
    }

    if (!packet.containsFixedHeader())
    {
        writebuf.headPtr()[0] = packet.getFirstByte();
        writebuf.advanceHead(1);
        RemainingLength r = packet.getRemainingLength();
        writebuf.write(r.bytes, r.len);
    }

    writebuf.write(packet.getBites().data(), packet.getBites().size());

    if (packet.packetType == PacketType::DISCONNECT)
        setReadyForDisconnect();

    setReadyForWriting(true);
}

// Helper method to avoid the exception ending up at the sender of messages, which would then get disconnected.
void Client::writeMqttPacketAndBlameThisClient(const MqttPacket &packet)
{
    try
    {
        this->writeMqttPacket(packet);
    }
    catch (std::exception &ex)
    {
        threadData->removeClient(fd);
    }
}

// Ping responses are always the same, so hardcoding it for optimization.
void Client::writePingResp()
{
    std::lock_guard<std::mutex> locker(writeBufMutex);

    writebuf.ensureFreeSpace(2);

    writebuf.headPtr()[0] = 0b11010000;
    writebuf.advanceHead(1);
    writebuf.headPtr()[0] = 0;
    writebuf.advanceHead(1);

    setReadyForWriting(true);
}

bool Client::writeBufIntoFd()
{
    std::unique_lock<std::mutex> lock(writeBufMutex, std::try_to_lock);
    if (!lock.owns_lock())
        return true;

    // We can abort the write; the client is about to be removed anyway.
    if (disconnecting)
        return false;

    IoWrapResult error = IoWrapResult::Success;
    int n;
    while (writebuf.usedBytes() > 0 || ioWrapper.hasPendingWrite())
    {
        n = ioWrapper.writeWebsocketAndOrSsl(fd, writebuf.tailPtr(), writebuf.maxReadSize(), &error);

        if (n > 0)
            writebuf.advanceTail(n);

        if (error == IoWrapResult::Interrupted)
            continue;
        if (error == IoWrapResult::Wouldblock)
            break;
    }

    const bool bufferHasData = writebuf.usedBytes() > 0;
    setReadyForWriting(bufferHasData || error == IoWrapResult::Wouldblock);

    return true;
}

std::string Client::repr()
{
    std::ostringstream a;
    a << "[Client=" << clientid << ", user=" << username << ", fd=" << fd << "]";
    a.flush();
    return a.str();
}

bool Client::keepAliveExpired()
{
    if (!authenticated)
        return lastActivity + 20 < time(NULL);

    bool result = (lastActivity + (keepalive*10/5)) < time(NULL);
    return result;
}

std::string Client::getKeepAliveInfoString() const
{
    std::string s = "authenticated: " + std::to_string(authenticated) + ", keep-alive: " + std::to_string(keepalive) + "s, last activity "
            + std::to_string(time(NULL) - lastActivity) + " seconds ago.";
    return s;
}

void Client::resetBuffersIfEligible()
{
    readbuf.resetSizeIfEligable(initialBufferSize);
    writebuf.resetSizeIfEligable(initialBufferSize);
}

#ifndef NDEBUG
/**
 * @brief IoWrapper::setFakeUpgraded().
 */
void Client::setFakeUpgraded()
{
    ioWrapper.setFakeUpgraded();
}
#endif

// Call this from a place you know the writeBufMutex is locked, or we're still only doing SSL accept.
void Client::setReadyForWriting(bool val)
{
#ifndef NDEBUG
    if (fuzzMode)
        return;
#endif

    if (disconnecting)
        return;

    if (ioWrapper.getSslReadWantsWrite())
        val = true;

    if (val == this->readyForWriting)
        return;

    readyForWriting = val;
    struct epoll_event ev;
    memset(&ev, 0, sizeof (struct epoll_event));
    ev.data.fd = fd;
    if (readyForReading)
        ev.events |= EPOLLIN;
    if (readyForWriting)
        ev.events |= EPOLLOUT;
    check<std::runtime_error>(epoll_ctl(threadData->epollfd, EPOLL_CTL_MOD, fd, &ev));
}

void Client::setReadyForReading(bool val)
{
#ifndef NDEBUG
    if (fuzzMode)
        return;
#endif

    if (disconnecting)
        return;

    if (val == this->readyForReading)
        return;

    readyForReading = val;
    struct epoll_event ev;
    memset(&ev, 0, sizeof (struct epoll_event));
    ev.data.fd = fd;
    if (readyForReading)
        ev.events |= EPOLLIN;
    if (readyForWriting)
        ev.events |= EPOLLOUT;
    check<std::runtime_error>(epoll_ctl(threadData->epollfd, EPOLL_CTL_MOD, fd, &ev));
}

bool Client::bufferToMqttPackets(std::vector<MqttPacket> &packetQueueIn, Client_p &sender)
{
    while (readbuf.usedBytes() >= MQTT_HEADER_LENGH)
    {
        // Determine the packet length by decoding the variable length
        int remaining_length_i = 1; // index of 'remaining length' field is one after start.
        uint fixed_header_length = 1;
        size_t multiplier = 1;
        size_t packet_length = 0;
        unsigned char encodedByte = 0;
        do
        {
            fixed_header_length++;

            if (fixed_header_length > 5)
                throw ProtocolError("Packet signifies more than 5 bytes in variable length header. Invalid.");

            // This happens when you only don't have all the bytes that specify the remaining length.
            if (fixed_header_length > readbuf.usedBytes())
                return false;

            encodedByte = readbuf.peakAhead(remaining_length_i++);
            packet_length += (encodedByte & 127) * multiplier;
            multiplier *= 128;
            if (multiplier > 128*128*128*128)
                throw ProtocolError("Malformed Remaining Length.");
        }
        while ((encodedByte & 128) != 0);
        packet_length += fixed_header_length;

        if (!authenticated && packet_length >= 1024*1024)
        {
            throw ProtocolError("An unauthenticated client sends a packet of 1 MB or bigger? Probably it's just random bytes.");
        }

        if (packet_length > ABSOLUTE_MAX_PACKET_SIZE)
        {
            throw ProtocolError("A client sends a packet claiming to be bigger than the maximum MQTT allows.");
        }

        if (packet_length <= readbuf.usedBytes())
        {
            MqttPacket packet(readbuf, packet_length, fixed_header_length, sender);
            packetQueueIn.push_back(std::move(packet));
        }
        else
            break;
    }

    setReadyForReading(readbuf.freeSpace() > 0);

    return true;
}

void Client::setClientProperties(ProtocolVersion protocolVersion, const std::string &clientId, const std::string username, bool connectPacketSeen, uint16_t keepalive, bool cleanSession)
{
    this->protocolVersion = protocolVersion;
    this->clientid = clientId;
    this->username = username;
    this->connectPacketSeen = connectPacketSeen;
    this->keepalive = keepalive;
    this->cleanSession = cleanSession;
}

void Client::setWill(const std::string &topic, const std::string &payload, bool retain, char qos)
{
    this->will_topic = topic;
    this->will_payload = payload;
    this->will_retain = retain;
    this->will_qos = qos;
}

void Client::assignSession(std::shared_ptr<Session> &session)
{
    this->session = session;
}

std::shared_ptr<Session> Client::getSession()
{
    return this->session;
}

void Client::setDisconnectReason(const std::string &reason)
{
    if (!this->disconnectReason.empty())
        this->disconnectReason += ", ";
    this->disconnectReason.append(reason);
}

void Client::clearWill()
{
    will_topic.clear();
    will_payload.clear();
    will_retain = false;
    will_qos = 0;
}