TCPConnection.cpp

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/*
 * TCPConnection.cpp
 *
 * Copyright (C) 2011 IBR, TU Braunschweig
 *
 * Written-by: Johannes Morgenroth <morgenroth@ibr.cs.tu-bs.de>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include "config.h"
#include "Configuration.h"
#include "core/BundleCore.h"
#include "core/BundleEvent.h"
#include "storage/BundleStorage.h"
#include "core/FragmentManager.h"

#include "net/TCPConvergenceLayer.h"
#include "net/BundleReceivedEvent.h"
#include "net/ConnectionEvent.h"
#include "net/TransferAbortedEvent.h"

#include <ibrcommon/net/socket.h>
#include <ibrcommon/TimeMeasurement.h>
#include <ibrcommon/net/vinterface.h>
#include <ibrcommon/thread/Conditional.h>
#include <ibrcommon/Logger.h>

#include <iostream>
#include <iomanip>
#include <memory>

#ifdef WITH_TLS
#include "security/SecurityCertificateManager.h"
#include <openssl/x509.h>
#include <ibrcommon/TLSExceptions.h>
#include <ibrcommon/ssl/TLSStream.h>
#endif

#ifdef WITH_BUNDLE_SECURITY
#include "security/SecurityManager.h"
#endif

namespace dtn
{
        namespace net
        {
                const std::string TCPConnection::TAG = "TCPConnection";

                /*
                 * class TCPConnection
                 */
                TCPConnection::TCPConnection(TCPConvergenceLayer &tcpsrv, const dtn::core::Node &node, ibrcommon::clientsocket *sock, const size_t timeout)
                 : _peer(), _node(node), _socket(sock), _socket_stream(NULL), _sec_stream(NULL), _protocol_stream(NULL), _sender(*this),
                   _keepalive_sender(*this, _keepalive_timeout), _timeout(timeout), _lastack(0), _resume_offset(0), _keepalive_timeout(0),
                   _callback(tcpsrv), _flags(0), _aborted(false)
                {
                }

                TCPConnection::~TCPConnection()
                {
                        // join the keepalive sender thread
                        _keepalive_sender.join();

                        // wait until the sender thread is finished
                        _sender.join();

                        // clean-up
                        {
                                ibrcommon::RWLock l(_protocol_stream_mutex, ibrcommon::RWMutex::LOCK_READWRITE);
                                delete _protocol_stream;
                                _protocol_stream = NULL;
                        }

                        if (_sec_stream != NULL) {
                                delete _sec_stream;
                        }

                        if ((_socket != NULL) && (_socket_stream == NULL)) {
                                delete _socket;
                        } else if (_socket_stream != NULL) {
                                delete _socket_stream;
                        }
                }

                void TCPConnection::queue(const dtn::net::BundleTransfer &job)
                {
                        _sender.push(job);
                }

                const dtn::streams::StreamContactHeader& TCPConnection::getHeader() const
                {
                        return _peer;
                }

                const dtn::core::Node& TCPConnection::getNode() const
                {
                        return _node;
                }

                void TCPConnection::rejectTransmission()
                {
                        (*getProtocolStream()).reject();
                }

                void TCPConnection::eventShutdown(dtn::streams::StreamConnection::ConnectionShutdownCases) throw ()
                {
                }

                void TCPConnection::eventTimeout() throw ()
                {
                        // event
                        ConnectionEvent::raise(ConnectionEvent::CONNECTION_TIMEOUT, _node);

                        try {
                                // stop the receiver thread
                                this->stop();
                        } catch (const ibrcommon::ThreadException &ex) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, error) << ex.what() << IBRCOMMON_LOGGER_ENDL;
                        }
                }

                void TCPConnection::eventError() throw ()
                {
                }

                void TCPConnection::initiateExtendedHandshake() throw (ibrcommon::Exception)
                {
#ifdef WITH_TLS
                        /* if both nodes support TLS, activate it */
                        if (_peer._flags.getBit(dtn::streams::StreamContactHeader::REQUEST_TLS)
                                        && _flags.getBit(dtn::streams::StreamContactHeader::REQUEST_TLS))
                        {
                                try{
                                        ibrcommon::TLSStream &tls = dynamic_cast<ibrcommon::TLSStream&>(*_sec_stream);
                                        X509 *peer_cert = tls.activate();

                                        // check the full EID first
                                        const std::string cn = _peer.getEID().getString();

                                        try {
                                                try {
                                                        dtn::security::SecurityCertificateManager::validateSubject(peer_cert, cn);
                                                } catch (const dtn::security::SecurityCertificateException &ex) {
                                                        // check using the hostname
                                                        std::string weak_cn = _peer.getEID().getHost();

                                                        // strip leading "//"
                                                        if (weak_cn.find_first_of("//") == 0) {
                                                                weak_cn = weak_cn.substr(2, weak_cn.length() - 2);
                                                        }

                                                        try {
                                                                dtn::security::SecurityCertificateManager::validateSubject(peer_cert, weak_cn);
                                                        } catch (const dtn::security::SecurityCertificateException &ex_weak) {
                                                                throw ex;
                                                        }
                                                }
                                        } catch (const dtn::security::SecurityCertificateException &ex) {
                                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, warning) << ex.what() << IBRCOMMON_LOGGER_ENDL;
                                                throw ibrcommon::TLSCertificateVerificationException(ex.what());
                                        }
                                } catch (const std::exception&) {
                                        if (dtn::daemon::Configuration::getInstance().getSecurity().TLSRequired()){
                                                /* close the connection */
                                                IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 20) << "TLS failed, closing the connection." << IBRCOMMON_LOGGER_ENDL;
                                                throw;
                                        } else {
                                                IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 20) << "TLS failed, continuing unauthenticated." << IBRCOMMON_LOGGER_ENDL;
                                        }
                                }
                        } else {
                                /* TLS not supported by both Nodes, check if its required */
                                if (dtn::daemon::Configuration::getInstance().getSecurity().TLSRequired()){
                                        /* close the connection */
                                        throw ibrcommon::TLSException("TLS not supported by peer.");
                                } else if(_flags & dtn::streams::StreamContactHeader::REQUEST_TLS){
                                        IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, notice) << "TLS not supported by peer. Continuing without TLS." << IBRCOMMON_LOGGER_ENDL;
                                }
                                /* else: this node does not support TLS, should have already printed a warning */
                        }
#endif
                }

                void TCPConnection::eventConnectionUp(const dtn::streams::StreamContactHeader &header) throw ()
                {
                        _peer = header;

                        // copy old attributes and urls to the new node object
                        Node n_old = _node;
                        _node = Node(header._localeid);
                        _node += n_old;

                        // check if the peer has the same EID
                        if (_node.getEID() == dtn::core::BundleCore::getInstance().local)
                        {
                                // abort the connection
                                shutdown();

                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, warning) << "connection to local endpoint rejected" << IBRCOMMON_LOGGER_ENDL;
                                return;
                        }

                        _keepalive_timeout = header._keepalive * 1000;

                        try {
                                // initiate extended handshake (e.g. TLS)
                                initiateExtendedHandshake();
                        } catch (const ibrcommon::Exception &ex) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, warning) << ex.what() << IBRCOMMON_LOGGER_ENDL;

                                // abort the connection
                                shutdown();
                                return;
                        }

                        // set the incoming timer if set (> 0)
                        if (_peer._keepalive > 0)
                        {
                                // set the timer
                                timeval timeout;
                                timerclear(&timeout);
                                timeout.tv_sec = header._keepalive * 2;
                                _socket_stream->setTimeout(timeout);
                        }

                        try {
                                // enable idle timeout
                                size_t _idle_timeout = dtn::daemon::Configuration::getInstance().getNetwork().getTCPIdleTimeout();
                                if (_idle_timeout > 0)
                                {
                                        (*getProtocolStream()).enableIdleTimeout(_idle_timeout);
                                }
                        } catch (const ibrcommon::Exception&) {};

                        // raise up event
                        ConnectionEvent::raise(ConnectionEvent::CONNECTION_UP, _node);
                }

                void TCPConnection::eventConnectionDown() throw ()
                {
                        IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 40) << "eventConnectionDown()" << IBRCOMMON_LOGGER_ENDL;

                        try {
                                // shutdown the keepalive sender thread
                                _keepalive_sender.stop();

                                // stop the sender
                                _sender.stop();
                        } catch (const ibrcommon::ThreadException &ex) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, error) << ex.what() << IBRCOMMON_LOGGER_ENDL;
                        }

                        if (_peer._localeid != dtn::data::EID())
                        {
                                // event
                                ConnectionEvent::raise(ConnectionEvent::CONNECTION_DOWN, _node);
                        }
                }

                void TCPConnection::eventBundleRefused() throw ()
                {
                        ibrcommon::Queue<dtn::net::BundleTransfer>::Locked l = _sentqueue.exclusive();

                        // stop here if the queue is already empty
                        if (l.empty()) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, error) << "transfer refused without a bundle in queue" << IBRCOMMON_LOGGER_ENDL;
                                return;
                        }

                        // get the job on top of the sent queue
                        dtn::net::BundleTransfer &job = l.front();

                        // abort the transmission
                        job.abort(dtn::net::TransferAbortedEvent::REASON_REFUSED);

                        // set ACK to zero
                        _lastack = 0;

                        // release the job
                        l.pop();
                }

                void TCPConnection::eventBundleForwarded() throw ()
                {
                        ibrcommon::Queue<dtn::net::BundleTransfer>::Locked l = _sentqueue.exclusive();

                        // stop here if the queue is already empty
                        if (l.empty()) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, error) << "transfer completed without a bundle in queue" << IBRCOMMON_LOGGER_ENDL;
                                return;
                        }

                        // get the job on top of the sent queue
                        dtn::net::BundleTransfer &job = l.front();

                        // mark job as complete
                        job.complete();

                        // set ACK to zero
                        _lastack = 0;

                        // release the job
                        l.pop();
                }

                void TCPConnection::eventBundleAck(const dtn::data::Length &ack) throw ()
                {
                        _lastack = ack;
                }

                void TCPConnection::addTrafficIn(size_t amount) throw ()
                {
                        _callback.addTrafficIn(amount);
                }

                void TCPConnection::addTrafficOut(size_t amount) throw ()
                {
                        _callback.addTrafficOut(amount);
                }

                void TCPConnection::initialize() throw ()
                {
                        // start the receiver for incoming bundles + handshake
                        try {
                                start();
                        } catch (const ibrcommon::ThreadException &ex) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, error) << ex.what() << IBRCOMMON_LOGGER_ENDL;
                        }
                }

                void TCPConnection::shutdown() throw ()
                {
                        try {
                                // shutdown
                                (*getProtocolStream()).shutdown(dtn::streams::StreamConnection::CONNECTION_SHUTDOWN_ERROR);
                        } catch (const ibrcommon::Exception&) {};

                        try {
                                // abort the connection thread
                                ibrcommon::DetachedThread::stop();
                        } catch (const ibrcommon::ThreadException &ex) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, error) << "shutdown failed (" << ex.what() << ")" << IBRCOMMON_LOGGER_ENDL;
                        }
                }

                void TCPConnection::__cancellation() throw ()
                {
                        // mark the connection as aborted
                        _aborted = true;

                        // close the stream
                        if (_socket_stream != NULL) _socket_stream->close();
                }

                void TCPConnection::finally() throw ()
                {
                        IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 60) << "TCPConnection down" << IBRCOMMON_LOGGER_ENDL;

                        try {
                                // shutdown the keepalive sender thread
                                _keepalive_sender.stop();

                                // shutdown the sender thread
                                _sender.stop();
                        } catch (const std::exception&) { };

                        // close the tcpstream
                        if (_socket_stream != NULL) _socket_stream->close();

                        try {
                                _callback.connectionDown(this);
                        } catch (const ibrcommon::MutexException&) { };

                        // clear the queue
                        clearQueue();
                }

                void TCPConnection::setup() throw ()
                {
                        _flags |= dtn::streams::StreamContactHeader::REQUEST_ACKNOWLEDGMENTS;
                        _flags |= dtn::streams::StreamContactHeader::REQUEST_NEGATIVE_ACKNOWLEDGMENTS;

                        if (dtn::daemon::Configuration::getInstance().getNetwork().doFragmentation())
                        {
                                _flags |= dtn::streams::StreamContactHeader::REQUEST_FRAGMENTATION;
                        }
                }

                void TCPConnection::__setup_socket(ibrcommon::clientsocket *sock, bool server)
                {
                        if ( dtn::daemon::Configuration::getInstance().getNetwork().getTCPOptionNoDelay() )
                        {
                                sock->set(ibrcommon::clientsocket::NO_DELAY, true);
                        }

                        _socket_stream = new ibrcommon::socketstream(sock);

#ifdef WITH_TLS
                        // initialize security layer if available
                        _sec_stream = new ibrcommon::TLSStream(_socket_stream);
                        if (server) dynamic_cast<ibrcommon::TLSStream&>(*_sec_stream).setServer(true);
                        else dynamic_cast<ibrcommon::TLSStream&>(*_sec_stream).setServer(false);
#endif

                        // create a new stream connection
                        dtn::data::Length chunksize = dtn::daemon::Configuration::getInstance().getNetwork().getTCPChunkSize();

                        ibrcommon::RWLock l(_protocol_stream_mutex, ibrcommon::RWMutex::LOCK_READWRITE);
                        if (_protocol_stream != NULL) delete _protocol_stream;
                        _protocol_stream = new dtn::streams::StreamConnection(*this, (_sec_stream == NULL) ? *_socket_stream : *_sec_stream, chunksize);
                        _protocol_stream->exceptions(std::ios::badbit | std::ios::eofbit);
                }

                void TCPConnection::connect()
                {
                        // do not connect to other hosts if we are in server
                        if (_socket != NULL) return;

                        // do not connect to anyone if we are already connected
                        if (_socket_stream != NULL) return;

                        // variables for address and port
                        std::string address = "0.0.0.0";
                        unsigned int port = 0;

                        // try to connect to the other side
                        try {
                                const std::list<dtn::core::Node::URI> uri_list = _node.get(dtn::core::Node::CONN_TCPIP);

                                for (std::list<dtn::core::Node::URI>::const_iterator iter = uri_list.begin(); iter != uri_list.end(); ++iter)
                                {
                                        // break-out if the connection has been aborted
                                        if (_aborted) throw ibrcommon::socket_exception("connection has been aborted");

                                        try {
                                                // decode address and port
                                                const dtn::core::Node::URI &uri = (*iter);
                                                uri.decode(address, port);

                                                // create a virtual address to connect to
                                                ibrcommon::vaddress addr(address, port);

                                                IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 15) << "Initiate TCP connection to " << address << ":" << port << IBRCOMMON_LOGGER_ENDL;

                                                // create a new tcpsocket
                                                timeval tv;
                                                timerclear(&tv);
                                                tv.tv_sec = _timeout;

                                                // create a new tcp connection via the tcpsocket object
                                                ibrcommon::tcpsocket *client = new ibrcommon::tcpsocket(addr, &tv);

                                                try {
                                                        // connect to the node
                                                        client->up();

                                                        // setup a new tcp connection
                                                        __setup_socket(client, false);

                                                        // add TCP connection descriptor to the node object
                                                        _node.clear();
                                                        _node.add( dtn::core::Node::URI(Node::NODE_CONNECTED, Node::CONN_TCPIP, uri.value, 0, 30) );

                                                        // connection successful
                                                        return;
                                                } catch (const ibrcommon::socket_exception&) {
                                                        delete client;
                                                }
                                        } catch (const ibrcommon::socket_exception&) { };
                                }

                                // no connection has been established
                                throw ibrcommon::socket_exception("no address available to connect");

                        } catch (const ibrcommon::socket_exception&) {
                                // error on open, requeue all bundles in the queue
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, warning) << "connection to " << _node.toString() << " failed" << IBRCOMMON_LOGGER_ENDL;
                                try {
                                        (*getProtocolStream()).shutdown(dtn::streams::StreamConnection::CONNECTION_SHUTDOWN_ERROR);
                                } catch (const ibrcommon::Exception&) {};
                                throw;
                        } catch (const bad_cast&) { };
                }

                void TCPConnection::run() throw ()
                {
                        try {
                                if (_socket == NULL) {
                                        // connect to the peer
                                        connect();
                                } else {
                                        // accept remote connection as server
                                        __setup_socket(_socket, true);
                                }

                                TCPConnection::safe_streamconnection sc = getProtocolStream();
                                std::iostream &stream = (*sc);

                                // do the handshake
                                (*sc).handshake(dtn::core::BundleCore::local, _timeout, _flags);

                                // start the sender
                                _sender.start();

                                // start keepalive sender
                                _keepalive_sender.start();

                                // create a deserializer for next bundle
                                dtn::data::DefaultDeserializer deserializer(stream, dtn::core::BundleCore::getInstance());

                                while (!(*sc).eof())
                                {
                                        try {
                                                // create a new empty bundle
                                                dtn::data::Bundle bundle;

                                                // check if the stream is still good
                                                if (!stream.good()) throw ibrcommon::IOException("stream went bad");

                                                // enable/disable fragmentation support according to the contact header.
                                                deserializer.setFragmentationSupport(_peer._flags.getBit(dtn::streams::StreamContactHeader::REQUEST_FRAGMENTATION));

                                                // read the bundle (or the fragment if fragmentation is enabled)
                                                deserializer >> bundle;

                                                // check the bundle
                                                if ( ( bundle.destination == EID() ) || ( bundle.source == EID() ) )
                                                {
                                                        // invalid bundle!
                                                        throw dtn::data::Validator::RejectedException("destination or source EID is null");
                                                }

                                                // raise default bundle received event
                                                dtn::net::BundleReceivedEvent::raise(_peer._localeid, bundle, false);
                                        }
                                        catch (const dtn::data::Validator::RejectedException &ex)
                                        {
                                                // bundle rejected
                                                rejectTransmission();

                                                // display the rejection
                                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, warning) << "bundle has been rejected: " << ex.what() << IBRCOMMON_LOGGER_ENDL;
                                        }
                                        catch (const dtn::InvalidDataException &ex) {
                                                // bundle rejected
                                                rejectTransmission();

                                                // display the rejection
                                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, warning) << "invalid bundle-data received: " << ex.what() << IBRCOMMON_LOGGER_ENDL;
                                        }

                                        yield();
                                }
                        } catch (const ibrcommon::ThreadException &ex) {
                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, error) << "failed to start thread in TCPConnection\n" << ex.what() << IBRCOMMON_LOGGER_ENDL;
                                try {
                                        (*getProtocolStream()).shutdown(dtn::streams::StreamConnection::CONNECTION_SHUTDOWN_ERROR);
                                } catch (const ibrcommon::Exception&) {};
                        } catch (const std::exception &ex) {
                                IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 10) << "run(): std::exception (" << ex.what() << ")" << IBRCOMMON_LOGGER_ENDL;
                                try {
                                        (*getProtocolStream()).shutdown(dtn::streams::StreamConnection::CONNECTION_SHUTDOWN_ERROR);
                                } catch (const ibrcommon::Exception&) {};
                        }
                }

                TCPConnection::safe_streamconnection TCPConnection::getProtocolStream() throw (ibrcommon::Exception)
                {
                        return safe_streamconnection(_protocol_stream, _protocol_stream_mutex);
                }

                TCPConnection::KeepaliveSender::KeepaliveSender(TCPConnection &connection, size_t &keepalive_timeout)
                 : _connection(connection), _keepalive_timeout(keepalive_timeout)
                {

                }

                TCPConnection::KeepaliveSender::~KeepaliveSender()
                {
                }

                void TCPConnection::KeepaliveSender::run() throw ()
                {
                        try {
                                ibrcommon::MutexLock l(_wait);
                                while (true)
                                {
                                        try {
                                                _wait.wait(_keepalive_timeout);
                                        } catch (const ibrcommon::Conditional::ConditionalAbortException &ex) {
                                                if (ex.reason == ibrcommon::Conditional::ConditionalAbortException::COND_TIMEOUT)
                                                {
                                                        // send a keepalive
                                                        _connection.keepalive();
                                                }
                                                else
                                                {
                                                        throw;
                                                }
                                        }
                                }
                        } catch (const std::exception&) { };
                }

                void TCPConnection::KeepaliveSender::__cancellation() throw ()
                {
                        ibrcommon::MutexLock l(_wait);
                        _wait.abort();
                }

                TCPConnection::Sender::Sender(TCPConnection &connection)
                 : _connection(connection)
                {
                }

                TCPConnection::Sender::~Sender()
                {
                }

                void TCPConnection::Sender::__cancellation() throw ()
                {
                        // cancel the main thread in here
                        ibrcommon::Queue<dtn::net::BundleTransfer>::abort();
                }

                void TCPConnection::Sender::run() throw ()
                {
                        try {
                                dtn::storage::BundleStorage &storage = dtn::core::BundleCore::getInstance().getStorage();

                                TCPConnection::safe_streamconnection sc = _connection.getProtocolStream();
                                std::iostream &stream = (*sc);

                                // create a serializer
                                dtn::data::DefaultSerializer serializer(stream);

                                while (stream.good())
                                {
                                        dtn::net::BundleTransfer transfer = ibrcommon::Queue<dtn::net::BundleTransfer>::getnpop(true);

                                        // check if the transfer is directed to the connected neighbor
                                        if (transfer.getNeighbor() != _connection.getNode().getEID()) continue;

                                        try {
                                                // read the bundle out of the storage
                                                dtn::data::Bundle bundle = storage.get(transfer.getBundle());

#ifdef WITH_BUNDLE_SECURITY
                                                const int seclevel = dtn::daemon::Configuration::getInstance().getSecurity().getLevel();

                                                if (seclevel & dtn::daemon::Configuration::Security::SECURITY_LEVEL_AUTHENTICATED)
                                                {
                                                        try {
                                                                dtn::security::SecurityManager::getInstance().auth(bundle);
                                                        } catch (const dtn::security::SecurityManager::KeyMissingException&) {
                                                                // sign requested, but no key is available
                                                                IBRCOMMON_LOGGER_TAG(TCPConnection::TAG, warning) << "No key available for sign process." << IBRCOMMON_LOGGER_ENDL;
                                                        }
                                                }
#endif

                                                // send bundle
                                                // get the offset, if this bundle has been reactively fragmented before
                                                if (dtn::daemon::Configuration::getInstance().getNetwork().doFragmentation()
                                                                && !bundle.get(dtn::data::PrimaryBlock::DONT_FRAGMENT))
                                                {
                                                        _connection._resume_offset = dtn::core::FragmentManager::getOffset(_connection.getNode().getEID(), bundle);
                                                }
                                                else
                                                {
                                                        _connection._resume_offset = 0;
                                                }

                                                // put the bundle into the sentqueue
                                                _connection._sentqueue.push(transfer);

                                                try {
                                                        // activate exceptions for this method
                                                        if (!stream.good()) throw ibrcommon::IOException("stream went bad");

                                                        if (_connection._resume_offset > 0)
                                                        {
                                                                IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 4) << "Resume transfer of bundle " << bundle.toString() << " to " << _connection.getNode().getEID().getString() << ", offset: " << _connection._resume_offset << IBRCOMMON_LOGGER_ENDL;

                                                                // transmit the fragment
                                                                serializer << dtn::data::BundleFragment(bundle, _connection._resume_offset, -1);
                                                        }
                                                        else
                                                        {
                                                                // transmit the bundle
                                                                serializer << bundle;
                                                        }

                                                        // flush the stream
                                                        stream << std::flush;
                                                } catch (const ibrcommon::Exception &ex) {
                                                        // the connection not available
                                                        IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 10) << "connection error: " << ex.what() << IBRCOMMON_LOGGER_ENDL;

                                                        // forward exception
                                                        throw;
                                                }
                                        } catch (const dtn::storage::NoBundleFoundException&) {
                                                // send transfer aborted event
                                                transfer.abort(dtn::net::TransferAbortedEvent::REASON_BUNDLE_DELETED);
                                        }

                                        // idle a little bit
                                        yield();
                                }
                        } catch (const ibrcommon::QueueUnblockedException &ex) {
                                IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 50) << "Sender::run(): aborted" << IBRCOMMON_LOGGER_ENDL;
                                return;
                        } catch (const std::exception &ex) {
                                IBRCOMMON_LOGGER_DEBUG_TAG(TCPConnection::TAG, 10) << "Sender terminated by exception: " << ex.what() << IBRCOMMON_LOGGER_ENDL;
                        }

                        _connection.stop();
                }

                void TCPConnection::clearQueue()
                {
                        // requeue all bundles still in transit
                        ibrcommon::Queue<dtn::net::BundleTransfer>::Locked l = _sentqueue.exclusive();

                        while (!l.empty())
                        {
                                // get the job on top of the sent queue
                                const dtn::net::BundleTransfer &job = l.front();

                                if ((_lastack > 0) && (_peer._flags.getBit(dtn::streams::StreamContactHeader::REQUEST_FRAGMENTATION)))
                                {
                                        // some data are already acknowledged
                                        // store this information in the fragment manager
                                        dtn::core::FragmentManager::setOffset(_peer.getEID(), job.getBundle(), _lastack, _resume_offset);
                                }

                                // set last ack to zero
                                _lastack = 0;

                                // release the job
                                l.pop();
                        }
                }

#ifdef WITH_TLS
                void dtn::net::TCPConnection::enableTLS()
                {
                        _flags.setBit(dtn::streams::StreamContactHeader::REQUEST_TLS, true);
                }
#endif

                void TCPConnection::keepalive()
                {
                        (*getProtocolStream()).keepalive();
                }

                bool TCPConnection::good() const
                {
                        return _socket_stream->good();
                }

                void TCPConnection::Sender::finally() throw ()
                {
                }

                bool TCPConnection::match(const dtn::core::Node &n) const
                {
                        return (_node == n);
                }

                bool TCPConnection::match(const dtn::data::EID &destination) const
                {
                        return _node.getEID().sameHost(destination);
                }

                bool TCPConnection::match(const NodeEvent &evt) const
                {
                        const dtn::core::Node &n = evt.getNode();
                        return match(n);
                }
        }
}