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#include "peerwireclient.h"

#include <QHostAddress>

#include <QTimerEvent>

static const int PendingRequestTimeout = 60 * 1000;

static const int ClientTimeout = 120 * 1000;

static const int ConnectTimeout = 60 * 1000;

static const int KeepAliveInterval = 30 * 1000;

static const int RateControlTimerDelay = 2000;

static const int MinimalHeaderSize = 48;

static const int FullHeaderSize = 68;

static const char ProtocolId[] = "BitTorrent protocol";

static const char ProtocolIdSize = 19;

// Reads a 32bit unsigned int from data in network order.

static inline quint32 fromNetworkData(const char *data)

{

    const unsigned char *udata = (const unsigned char *)data;

    return (quint32(udata[0]) << 24)

        | (quint32(udata[1]) << 16)

        | (quint32(udata[2]) << 8)

        | (quint32(udata[3]));

}

// Writes a 32bit unsigned int from num to data in network order.

static inline void toNetworkData(quint32 num, char *data)

{

    unsigned char *udata = (unsigned char *)data;

    udata[3] = (num & 0xff);

    udata[2] = (num & 0xff00) >> 8;

    udata[1] = (num & 0xff0000) >> 16;

    udata[0] = (num & 0xff000000) >> 24;

}

// Constructs an unconnected PeerWire client and starts the connect timer.

PeerWireClient::PeerWireClient(const QByteArray &peerId, QObject *parent)

    : QTcpSocket(parent), pendingBlockSizes(0),

      pwState(ChokingPeer | ChokedByPeer), receivedHandShake(false), gotPeerId(false),

      sentHandShake(false), nextPacketLength(-1), pendingRequestTimer(0), invalidateTimeout(false),

      keepAliveTimer(0), torrentPeer(0)

{

    memset(uploadSpeedData, 0, sizeof(uploadSpeedData));

    memset(downloadSpeedData, 0, sizeof(downloadSpeedData));

    transferSpeedTimer = startTimer(RateControlTimerDelay);

    timeoutTimer = startTimer(ConnectTimeout);

    peerIdString = peerId;

    connect(this, SIGNAL(readyRead()), this, SIGNAL(readyToTransfer()));

    connect(this, SIGNAL(connected()), this, SIGNAL(readyToTransfer()));

    connect(&socket, SIGNAL(connected()),

            this, SIGNAL(connected()));

    connect(&socket, SIGNAL(readyRead()),

            this, SIGNAL(readyRead()));

    connect(&socket, SIGNAL(disconnected()),

            this, SIGNAL(disconnected()));

    connect(&socket, SIGNAL(error(QAbstractSocket::SocketError)),

            this, SIGNAL(error(QAbstractSocket::SocketError)));

    connect(&socket, SIGNAL(bytesWritten(qint64)),

            this, SIGNAL(bytesWritten(qint64)));

    connect(&socket, SIGNAL(stateChanged(QAbstractSocket::SocketState)),

            this, SLOT(socketStateChanged(QAbstractSocket::SocketState)));

}

// Registers the peer ID and SHA1 sum of the torrent, and initiates

// the handshake.

void PeerWireClient::initialize(const QByteArray &infoHash, int pieceCount)

{

    this->infoHash = infoHash;

    peerPieces.resize(pieceCount);

    if (!sentHandShake)

        sendHandShake();

}

void PeerWireClient::setPeer(TorrentPeer *peer)

{

    torrentPeer = peer;

}

TorrentPeer *PeerWireClient::peer() const

{

    return torrentPeer;

}

QBitArray PeerWireClient::availablePieces() const

{

    return peerPieces;

}

QList<TorrentBlock> PeerWireClient::incomingBlocks() const

{

    return incoming;

}

// Sends a "choke" message, asking the peer to stop requesting blocks.

void PeerWireClient::chokePeer()

{

    const char message[] = {0, 0, 0, 1, 0};

    write(message, sizeof(message));

    pwState |= ChokingPeer;

    // After receiving a choke message, the peer will assume all

    // pending requests are lost.

    pendingBlocks.clear();

    pendingBlockSizes = 0;

}

// Sends an "unchoke" message, allowing the peer to start/resume

// requesting blocks.

void PeerWireClient::unchokePeer()

{

    const char message[] = {0, 0, 0, 1, 1};

    write(message, sizeof(message));

    pwState &= ~ChokingPeer;

    if (pendingRequestTimer)

        killTimer(pendingRequestTimer);

}

// Sends a "keep-alive" message to prevent the peer from closing

// the connection when there's no activity

void PeerWireClient::sendKeepAlive()

{

    const char message[] = {0, 0, 0, 0};

    write(message, sizeof(message));

}

// Sends an "interested" message, informing the peer that it has got

// pieces that we'd like to download.

void PeerWireClient::sendInterested()

{

    const char message[] = {0, 0, 0, 1, 2};

    write(message, sizeof(message));

    pwState |= InterestedInPeer;

    // After telling the peer that we're interested, we expect to get

    // unchoked within a certain timeframe; otherwise we'll drop the

    // connection.

    if (pendingRequestTimer)

        killTimer(pendingRequestTimer);

    pendingRequestTimer = startTimer(PendingRequestTimeout);

}

// Sends a "not interested" message, informing the peer that it does

// not have any pieces that we'd like to download.

void PeerWireClient::sendNotInterested()

{

    const char message[] = {0, 0, 0, 1, 3};

    write(message, sizeof(message));

    pwState &= ~InterestedInPeer;

}

// Sends a piece notification / a "have" message, informing the peer

// that we have just downloaded a new piece.

void PeerWireClient::sendPieceNotification(int piece)

{

    if (!sentHandShake)

        sendHandShake();

    char message[] = {0, 0, 0, 5, 4, 0, 0, 0, 0};

    toNetworkData(piece, &message[5]);

    write(message, sizeof(message));

}

// Sends the complete list of pieces that we have downloaded.

void PeerWireClient::sendPieceList(const QBitArray &bitField)

{

    // The bitfield message may only be sent immediately after the

    // handshaking sequence is completed, and before any other

    // messages are sent.

    if (!sentHandShake)

        sendHandShake();

    // Don't send the bitfield if it's all zeros.

    if (bitField.count(true) == 0)

	return;

    int bitFieldSize = bitField.size();

    int size = (bitFieldSize + 7) / 8;

    QByteArray bits(size, '\0');

    for (int i = 0; i < bitFieldSize; ++i) {

        if (bitField.testBit(i)) {

            quint32 byte = quint32(i) / 8;

            quint32 bit = quint32(i) % 8;

            bits[byte] = uchar(bits.at(byte)) | (1 << (7 - bit));

        }

    }

    char message[] = {0, 0, 0, 1, 5};

    toNetworkData(bits.size() + 1, &message[0]);

    write(message, sizeof(message));

    write(bits);

}

// Sends a request for a block.

void PeerWireClient::requestBlock(int piece, int offset, int length)

{

    char message[] = {0, 0, 0, 1, 6};

    toNetworkData(13, &message[0]);

    write(message, sizeof(message));

    char numbers[4 * 3];

    toNetworkData(piece, &numbers[0]);

    toNetworkData(offset, &numbers[4]);

    toNetworkData(length, &numbers[8]);

    write(numbers, sizeof(numbers));

    incoming << TorrentBlock(piece, offset, length);

    // After requesting a block, we expect the block to be sent by the

    // other peer within a certain number of seconds. Otherwise, we

    // drop the connection.

    if (pendingRequestTimer)

        killTimer(pendingRequestTimer);

    pendingRequestTimer = startTimer(PendingRequestTimeout);

}

// Cancels a request for a block.

void PeerWireClient::cancelRequest(int piece, int offset, int length)

{

    char message[] = {0, 0, 0, 1, 8};

    toNetworkData(13, &message[0]);

    write(message, sizeof(message));

    char numbers[4 * 3];

    toNetworkData(piece, &numbers[0]);

    toNetworkData(offset, &numbers[4]);

    toNetworkData(length, &numbers[8]);

    write(numbers, sizeof(numbers));

    incoming.removeAll(TorrentBlock(piece, offset, length));

}

// Sends a block to the peer.

void PeerWireClient::sendBlock(int piece, int offset, const QByteArray &data)

{

    QByteArray block;

    char message[] = {0, 0, 0, 1, 7};

    toNetworkData(9 + data.size(), &message[0]);

    block += QByteArray(message, sizeof(message));

    char numbers[4 * 2];

    toNetworkData(piece, &numbers[0]);

    toNetworkData(offset, &numbers[4]);

    block += QByteArray(numbers, sizeof(numbers));

    block += data;

    BlockInfo blockInfo;

    blockInfo.pieceIndex = piece;

    blockInfo.offset = offset;

    blockInfo.length = data.size();

    blockInfo.block = block;

    pendingBlocks << blockInfo;

    pendingBlockSizes += block.size();

    if (pendingBlockSizes > 32 * 16384) {

        chokePeer();

        unchokePeer();

        return;

    }

    emit readyToTransfer();

}

// Attempts to write 'bytes' bytes to the socket from the buffer.

// This is used by RateController, which precisely controls how much

// each client can write.

qint64 PeerWireClient::writeToSocket(qint64 bytes)

{

    qint64 totalWritten = 0;

    do {

        if (outgoingBuffer.isEmpty() && !pendingBlocks.isEmpty()) {

            BlockInfo block = pendingBlocks.takeFirst();

            pendingBlockSizes -= block.length;

            outgoingBuffer += block.block;

        }

        qint64 written = socket.write(outgoingBuffer.constData(),

                                      qMin<qint64>(bytes - totalWritten, outgoingBuffer.size()));

        if (written <= 0)

            return totalWritten ? totalWritten : written;

        totalWritten += written;

        uploadSpeedData[0] += written;

        outgoingBuffer.remove(0, written);

    } while (totalWritten < bytes && (!outgoingBuffer.isEmpty() || !pendingBlocks.isEmpty()));

    return totalWritten;

}

// Attempts to read at most 'bytes' bytes from the socket.

qint64 PeerWireClient::readFromSocket(qint64 bytes)

{

    char buffer[1024];

    qint64 totalRead = 0;

    do {

        qint64 bytesRead = socket.read(buffer, qMin<qint64>(sizeof(buffer), bytes - totalRead));

        if (bytesRead <= 0)

            break;

        qint64 oldSize = incomingBuffer.size();

        incomingBuffer.resize(oldSize + bytesRead);

        memcpy(incomingBuffer.data() + oldSize, buffer, bytesRead);

        totalRead += bytesRead;

    } while (totalRead < bytes);

    if (totalRead > 0) {

        downloadSpeedData[0] += totalRead;

        emit bytesReceived(totalRead);

        processIncomingData();

    }

    return totalRead;

}

// Returns the average number of bytes per second this client is

// downloading.

qint64 PeerWireClient::downloadSpeed() const

{

    qint64 sum = 0;

    for (unsigned int i = 0; i < sizeof(downloadSpeedData) / sizeof(qint64); ++i)

        sum += downloadSpeedData[i];

    return sum / (8 * 2);

}

// Returns the average number of bytes per second this client is

// uploading.

qint64 PeerWireClient::uploadSpeed() const

{

    qint64 sum = 0;

    for (unsigned int i = 0; i < sizeof(uploadSpeedData) / sizeof(qint64); ++i)

        sum += uploadSpeedData[i];

    return sum / (8 * 2);

}

void PeerWireClient::setReadBufferSize(int size)

{

    socket.setReadBufferSize(size);

}

bool PeerWireClient::canTransferMore() const

{

    return bytesAvailable() > 0 || socket.bytesAvailable() > 0

        || !outgoingBuffer.isEmpty() || !pendingBlocks.isEmpty();

}

void PeerWireClient::connectToHostImplementation(const QString &hostName,

                                                 quint16 port, OpenMode openMode)

{

    setOpenMode(openMode);

    socket.connectToHost(hostName, port, openMode);

}

void PeerWireClient::diconnectFromHostImplementation()

{

    socket.disconnectFromHost();

}

void PeerWireClient::timerEvent(QTimerEvent *event)

{

    if (event->timerId() == transferSpeedTimer) {

        // Rotate the upload / download records.

        for (int i = 6; i >= 0; --i) {

            uploadSpeedData[i + 1] = uploadSpeedData[i];

            downloadSpeedData[i + 1] = downloadSpeedData[i];

        }

        uploadSpeedData[0] = 0;

        downloadSpeedData[0] = 0;

    } else if (event->timerId() == timeoutTimer) {

        // Disconnect if we timed out; otherwise the timeout is

        // restarted.

        if (invalidateTimeout) {

            invalidateTimeout = false;

        } else {

            abort();

            emit infoHashReceived(QByteArray());

        }

    } else if (event->timerId() == pendingRequestTimer) {

        abort();

    } else if (event->timerId() == keepAliveTimer) {

        sendKeepAlive();

    }

    QTcpSocket::timerEvent(event);

}

// Sends the handshake to the peer.

void PeerWireClient::sendHandShake()

{

    sentHandShake = true;

    // Restart the timeout

    if (timeoutTimer)

        killTimer(timeoutTimer);

    timeoutTimer = startTimer(ClientTimeout);

    // Write the 68 byte PeerWire handshake.

    write(&ProtocolIdSize, 1);

    write(ProtocolId, ProtocolIdSize);

    write(QByteArray(8, '\0'));

    write(infoHash);

    write(peerIdString);

}

void PeerWireClient::processIncomingData()

{

    invalidateTimeout = true;

    if (!receivedHandShake) {

        // Check that we received enough data

        if (bytesAvailable() < MinimalHeaderSize)

            return;

        // Sanity check the protocol ID

        QByteArray id = read(ProtocolIdSize + 1);

        if (id.at(0) != ProtocolIdSize || !id.mid(1).startsWith(ProtocolId)) {

            abort();

            return;

        }

        // Discard 8 reserved bytes, then read the info hash and peer ID

        (void) read(8);

        // Read infoHash

        QByteArray peerInfoHash = read(20);

        if (!infoHash.isEmpty() && peerInfoHash != infoHash) {

            abort();

            return;

        }

        emit infoHashReceived(peerInfoHash);

        if (infoHash.isEmpty()) {

            abort();

            return;

        }

        // Send handshake

        if (!sentHandShake)

            sendHandShake();

        receivedHandShake = true;

    }

    // Handle delayed peer id arrival

    if (!gotPeerId) {

        if (bytesAvailable() < 20)

            return;

        gotPeerId = true;

        if (read(20) == peerIdString) {

            // We connected to ourself

            abort();

            return;

        }

    }

    // Initialize keep-alive timer

    if (!keepAliveTimer)

        keepAliveTimer = startTimer(KeepAliveInterval);

    do {

        // Find the packet length

        if (nextPacketLength == -1) {

            if (bytesAvailable() < 4)

                return;

            char tmp[4];

            read(tmp, sizeof(tmp));

            nextPacketLength = fromNetworkData(tmp);

            if (nextPacketLength < 0 || nextPacketLength > 200000) {

                // Prevent DoS

                abort();

                return;

            }

        }

        // KeepAlive

        if (nextPacketLength == 0) {

            nextPacketLength = -1;

            continue;

        }

        // Wait with parsing until the whole packet has been received

        if (bytesAvailable() < nextPacketLength)

            return;

        // Read the packet