source: source/ariba/overlay/BaseOverlay.cpp @ 5274

// [License]
// The Ariba-Underlay Copyright
//
// Copyright (c) 2008-2009, Institute of Telematics, UniversitÀt Karlsruhe (TH)
//
// Institute of Telematics
// UniversitÀt Karlsruhe (TH)
// Zirkel 2, 76128 Karlsruhe
// Germany
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE INSTITUTE OF TELEMATICS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ARIBA PROJECT OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// The views and conclusions contained in the software and documentation
// are those of the authors and should not be interpreted as representing
// official policies, either expressed or implied, of the Institute of
// Telematics.
// [License]

#include "BaseOverlay.h"

#include <sstream>
#include <iostream>
#include <string>
#include <boost/foreach.hpp>

#include "ariba/NodeListener.h"
#include "ariba/CommunicationListener.h"
#include "ariba/SideportListener.h"

#include "ariba/overlay/LinkDescriptor.h"
#include "ariba/overlay/messages/OverlayMsg.h"
#include "ariba/overlay/messages/JoinRequest.h"
#include "ariba/overlay/messages/JoinReply.h"
#include "ariba/overlay/messages/LinkRequest.h"
#include "ariba/overlay/messages/RelayMessage.h"

#include "ariba/utility/misc/OvlVis.h"

namespace ariba {
namespace overlay {

#define logging_force(x) std::cout << x << std::endl;
#define logging_force1(x) std::cout << x << std::endl;

LinkDescriptor* BaseOverlay::getDescriptor( const LinkID& link, bool communication ) {
        BOOST_FOREACH( LinkDescriptor* lp, links )
                if ((communication ? lp->communicationId : lp->overlayId) == link)
                        return lp;
        return NULL;
}

const LinkDescriptor* BaseOverlay::getDescriptor( const LinkID& link, bool communication ) const {
        BOOST_FOREACH( const LinkDescriptor* lp, links )
                if ((communication ? lp->communicationId : lp->overlayId) == link)
                        return lp;
        return NULL;
}

LinkDescriptor* BaseOverlay::getAutoDescriptor( const NodeID& node, const ServiceID& service ) {
        BOOST_FOREACH( LinkDescriptor* lp, links )
                if (lp->autolink && lp->remoteNode == node && lp->service == service)
                        return lp;
        return NULL;
}

void BaseOverlay::eraseDescriptor( const LinkID& link, bool communication ) {
        for ( vector<LinkDescriptor*>::iterator i = links.begin(); i!= links.end(); i++) {
                LinkDescriptor* ld = *i;
                if ((communication ? ld->communicationId : ld->overlayId) == link) {
                        delete ld;
                        links.erase(i);
                        break;
                }
        }
}

LinkDescriptor* BaseOverlay::addDescriptor( const LinkID& link ) {
        LinkDescriptor* desc = getDescriptor( link );
        if ( desc == NULL ) {
                desc = new LinkDescriptor();
                desc->overlayId = link;
                links.push_back(desc);
        }
        return desc;
}

/// returns a direct link relay descriptor to the given relay node
LinkDescriptor* BaseOverlay::getRelayDescriptor( const NodeID& relayNode ) {
        BOOST_FOREACH( LinkDescriptor* lp, links )
                if (lp->remoteNode == relayNode &&
                    lp->service == OverlayInterface::OVERLAY_SERVICE_ID &&
                    lp->relay == false &&
                    lp->up)
                        return lp;
        return NULL;
}

/// find a proper relay node
const NodeID BaseOverlay::findRelayNode( const NodeID& id ) {
        LinkDescriptor* rld = NULL;
        NodeID relayNode = NodeID::UNSPECIFIED;

        // get used next hop towards node
        LinkID rlid = overlayInterface->getNextLinkId(id);
        while ( relayNode.isUnspecified() && !rlid.isUnspecified() && rld == NULL ) {

                // get descriptor of first hop
                rld = getDescriptor(rlid);
                logging_force1( rld );

                // is first hop a relay path? yes-> try to find real link!
                if ( rld->relay )
                        relayNode = getRelayDescriptor(rld->localRelay)->remoteNode;

                // no-> a proper relay node has been found
                else relayNode = rld->remoteNode;
        }
        logging_force1( "Potential relay node " << relayNode.toString() );
        // do not return myself or use the node as relay node
        if (relayNode == nodeId)
                return NodeID::UNSPECIFIED;
        else {
                logging_force1( "Returning relay node " << relayNode.toString() );
                return relayNode;
        }
}

/// forwards a message over relays/overlay/directly using link descriptor
seqnum_t BaseOverlay::sendMessage( Message* message, const LinkDescriptor* ld ) {

        // directly send message
        if ( !ld->communicationId.isUnspecified() && ld->communicationUp ) {
                logging_debug("sendMessage: Sending message via Base Communication");
                return bc->sendMessage( ld->communicationId, message );
        }

        // relay message
        else if ( ld->relay ) {
                logging_debug("sendMessage: Relaying message to node "
                        << ld->remoteNode.toString()
                        << " using relay " << ld->localRelay
                );

                // get local relay link descriptor and mark as used for relaying
                LinkDescriptor* rld = getRelayDescriptor(ld->localRelay);
                if (rld==NULL) {
                        logging_error("sendMessage: Relay descriptor for relay " <<
                                ld->localRelay.toString() << " unknown.");
                        return -1;
                }
                rld->markAsRelay();

                // create a information relay message to inform the relay about
                OverlayMsg overlay_msg( OverlayMsg::typeRelay, ld->service, nodeId );
                RelayMessage relayMsg( RelayMessage::typeInform, ld->remoteRelay, ld->remoteNode, ld->remoteLinkId );
                relayMsg.encapsulate( message );
                overlay_msg.encapsulate( &relayMsg );

                // route message to relay node in order to inform it!
                logging_debug("sendMessage: Sending message over relayed link with" << ld );
                overlayInterface->routeMessage(rld->remoteNode, rld->overlayId, &overlay_msg);
                return 0;
        }

        // route message using overlay
        else {
                logging_error("Could not send message");
                logging_debug( "sendMessage: Routing message to node " << ld->remoteNode.toString() );
                overlayInterface->routeMessage( ld->remoteNode, message );
                return 0;
        }

        return -1;
}

/// creates a link descriptor, apply relay semantics if possible
LinkDescriptor* BaseOverlay::createLinkDescriptor(
        const NodeID& remoteNode, const ServiceID& service, const LinkID& link_id ) {

        // find listener
        if( !communicationListeners.contains( service ) ) {
                logging_error( "No listener found for service " << service.toString() );
                return NULL;
        }
        CommunicationListener* listener = communicationListeners.get( service );
        assert( listener != NULL );

        // copy link id
        LinkID linkid = link_id;

        // create link id if necessary
        if ( linkid.isUnspecified() )
                linkid = LinkID::create();

        // create relay link descriptor
        NodeID relayNode = findRelayNode(remoteNode);

        // add descriptor
        LinkDescriptor* ld = addDescriptor( linkid );
        ld->overlayId  = linkid;
        ld->service    = service;
        ld->listener   = listener;
        ld->remoteNode = remoteNode;

        // set relay node if available
        ld->relay      = !relayNode.isUnspecified();
        ld->localRelay = relayNode;

        if (!ld->relay)
                logging_error("No relay found!");

        // debug output
        logging_debug( "Created link descriptor: " << ld );

        return ld;
}


// ----------------------------------------------------------------------------

use_logging_cpp(BaseOverlay);

// ----------------------------------------------------------------------------

BaseOverlay::BaseOverlay() :
        bc(NULL), overlayInterface(NULL), nodeId(NodeID::UNSPECIFIED),
        spovnetId(SpoVNetID::UNSPECIFIED), initiatorLink(LinkID::UNSPECIFIED),
        state(BaseOverlayStateInvalid), sideport(&SideportListener::DEFAULT) {
}

BaseOverlay::~BaseOverlay() {
}

// ----------------------------------------------------------------------------

void BaseOverlay::start( BaseCommunication& _basecomm, const NodeID& _nodeid ) {
        logging_info("Starting...");

        // set parameters
        bc = &_basecomm;
        nodeId = _nodeid;

        // register at base communication
        bc->registerMessageReceiver( this );
        bc->registerEventListener( this );

        // timer for auto link management
        Timer::setInterval( 500 );
        Timer::start();
}

void BaseOverlay::stop() {
        logging_info("Stopping...");

        // stop timer
        Timer::stop();

        // delete oberlay interface
        if(overlayInterface != NULL) {
                delete overlayInterface;
                overlayInterface = NULL;
        }

        // unregister at base communication
        bc->unregisterMessageReceiver( this );
        bc->unregisterEventListener( this );
}

// ----------------------------------------------------------------------------

void BaseOverlay::joinSpoVNet(const SpoVNetID& id,
                const EndpointDescriptor& bootstrapEp) {

        ovl.visShowNodeBubble ( ovlId, nodeId, "joining..." );
        logging_info( "Starting to join spovnet " << id.toString() <<
                        " with nodeid " << nodeId.toString());

        // contact the spovnet initiator and request to join. if the join is granted we will
        // receive further information on the structure of the overlay that is used in the spovnet
        // but first, we have to establish a link to the initiator...
        spovnetId = id;
        state = BaseOverlayStateJoinInitiated;

        initiatorLink = bc->establishLink( bootstrapEp );
        logging_info("join process initiated for " << id.toString() << "...");
}

void BaseOverlay::leaveSpoVNet() {

        logging_info( "Leaving spovnet " << spovnetId );
        bool ret = ( state != this->BaseOverlayStateInvalid );

        logging_debug( "Dropping all auto-links" );

        // gather all service links
        vector<LinkID> servicelinks;
        BOOST_FOREACH( LinkDescriptor* ld, links ) {
                if( ld->service != OverlayInterface::OVERLAY_SERVICE_ID )
                servicelinks.push_back( ld->overlayId );
        }

        // drop all service links
        BOOST_FOREACH( LinkID lnk, servicelinks )
                dropLink( lnk );

        // let the node leave the spovnet overlay interface
        logging_debug( "Leaving overlay" );
        if( overlayInterface != NULL )
                overlayInterface->leaveOverlay();

        // leave spovnet
        if( state != BaseOverlayStateInitiator ) {
                // then, leave the spovnet baseoverlay
                OverlayMsg overMsg( OverlayMsg::typeBye, nodeId );
                bc->sendMessage( initiatorLink, &overMsg );

                // drop the link and set to correct state
                bc->dropLink( initiatorLink );
                initiatorLink = LinkID::UNSPECIFIED;
        }

        // change to inalid state
        state = BaseOverlayStateInvalid;
        ovl.visShutdown( ovlId, nodeId, string("") );

        // inform all registered services of the event
        BOOST_FOREACH( NodeListener* i, nodeListeners ) {
                if( ret ) i->onLeaveCompleted( spovnetId );
                else i->onLeaveFailed( spovnetId );
        }
}

void BaseOverlay::createSpoVNet(const SpoVNetID& id,
                const OverlayParameterSet& param,
                const SecurityParameterSet& sec,
                const QoSParameterSet& qos) {

        // set the state that we are an initiator, this way incoming messages are
        // handled correctly
        logging_info( "creating spovnet " + id.toString() <<
                        " with nodeid " << nodeId.toString() );

        spovnetId = id;
        state = BaseOverlayStateInitiator;

        overlayInterface = OverlayFactory::create( *this, param, nodeId, this );
        if( overlayInterface == NULL ) {
                logging_fatal( "overlay structure not supported" );
                state = BaseOverlayStateInvalid;
                return;
        }

        // bootstrap against ourselfs
        overlayInterface->joinOverlay();
        BOOST_FOREACH( NodeListener* i, nodeListeners )
                i->onJoinCompleted( spovnetId );

        ovl.visChangeNodeIcon ( ovlId, nodeId, OvlVis::ICON_ID_CAMERA );
        ovl.visChangeNodeColor( ovlId, nodeId, OvlVis::NODE_COLORS_GREEN );
}

// ----------------------------------------------------------------------------

const LinkID BaseOverlay::establishLink(
        const EndpointDescriptor& ep, const NodeID& nodeid,
        const ServiceID& service, const LinkID& linkid ) {

        LinkID link_id = linkid;

        // establish link via overlay
        if (!nodeid.isUnspecified())
                link_id = establishLink( nodeid, service, link_id );

        // establish link directly if only ep is known
        if (nodeid.isUnspecified())
                establishLink( ep, service, link_id );

        return link_id;
}

/// call base communication's establish link and add link mapping
const LinkID BaseOverlay::establishLink( const EndpointDescriptor& ep,
                const ServiceID& service, const LinkID& linkid ) {

        // create a new link id if necessary
        LinkID link_id = linkid;
        if (link_id.isUnspecified()) link_id = LinkID::create();

        /// find a service listener
        if( !communicationListeners.contains( service ) ) {
                logging_error( "No listener registered for service id=" << service.toString() );
                return LinkID::UNSPECIFIED;
        }
        CommunicationListener* listener = communicationListeners.get( service );
        assert( listener != NULL );

        /// establish link and add mapping
        logging_info("Establishing direct link " << link_id.toString()
                << " using " << ep.toString());

        // create descriptor
        LinkDescriptor* ld = addDescriptor( link_id );
        ld->overlayId = link_id;
        ld->communicationId = link_id;
        ld->listener = listener;
        ld->service = service;
        bc->establishLink( ep, link_id );

        return link_id;
}

/// establishes a link between two arbitrary nodes
const LinkID BaseOverlay::establishLink( const NodeID& node,
                const ServiceID& service, const LinkID& link_id ) {

        // do not establish a link to myself!
        if (node == nodeId) return LinkID::UNSPECIFIED;

        // create a link descriptor
        LinkDescriptor* ld = createLinkDescriptor( node, service, link_id );

        // create link request message with own link id
        uint32_t nonce = (uint32_t)(rand() ^ (rand() << 16) ^ time(NULL));
        LinkRequest link_request_msg(
                nonce, &bc->getEndpointDescriptor(), false,
                ld->overlayId, ld->localRelay );
        OverlayMsg overlay_msg( OverlayMsg::typeLinkRequest, service, nodeId );
        overlay_msg.encapsulate( &link_request_msg );
        pendingLinks.insert( make_pair(nonce, ld->overlayId) );

        // debug message
        logging_debug(
                "Sending link request with"
                << " link id="        << ld->overlayId
                << " node id="        << ld->remoteNode.toString()
                << " service id="     << ld->service.toString()
                << " local relay id=" << ld->localRelay.toString()
                << " nonce= "         << nonce
        );

        // sending message through new link
        sendMessage( &overlay_msg, ld );

        return ld->overlayId;
}

/// drops an established link
void BaseOverlay::dropLink(const LinkID& link) {
        logging_debug( "Dropping link (initiated locally):" << link.toString() );

        // find the link item to drop
        LinkDescriptor* ld = getDescriptor(link);
        if( ld == NULL ) {
                logging_warn( "Can't drop link, link is unknown!");
                return;
        }

        // delete all queued messages
        if( ld->messageQueue.size() > 0 ) {
                logging_warn( "Dropping link " << ld->overlayId.toString() << " that has "
                                << ld->messageQueue.size() << " waiting messages" );
                ld->flushQueue();
        }

        // inform sideport and listener
        ld->listener->onLinkDown( ld->overlayId, ld->remoteNode );
        sideport->onLinkDown(ld->overlayId, this->nodeId, ld->remoteNode, this->spovnetId );

        // do not drop relay links
        if (!ld->usedAsRelay) {
                // drop the link in base communication
                if (ld->communicationUp) bc->dropLink( ld->communicationId );

                // erase descriptor
                eraseDescriptor( ld->overlayId );
        } else
                ld->dropWhenRelaysLeft = true;
}

// ----------------------------------------------------------------------------

/// internal send message, always use this functions to send messages over links
seqnum_t BaseOverlay::sendMessage( const Message* message, const LinkID& link ) {
        logging_debug( "Sending data message on link " << link.toString() );

        // get the mapping for this link
        LinkDescriptor* ld = getDescriptor(link);
        if( ld == NULL ) {
                logging_error("Could not send message. "
                        << "Link not found id=" << link.toString());
                return -1;
        }

        // check if the link is up yet, if its an auto link queue message
        if( !ld->up ) {
                ld->markAsUsed();
                if( ld->autolink ) {
                        logging_info("Auto-link " << link.toString() << " not up, queue message");
                        Data data = data_serialize( message );
                        const_cast<Message*>(message)->dropPayload();
                        ld->messageQueue.push_back( new Message(data) );
                } else {
                        logging_error("Link " << link.toString() << " not up, drop message");
                }
                return -1;
        }

        // compile overlay message (has service and node id)
        OverlayMsg overmsg( OverlayMsg::typeData, ld->service, nodeId );
        overmsg.encapsulate( const_cast<Message*>(message) );

        // send message over relay/direct/overlay
        return sendMessage( &overmsg, ld );
}

seqnum_t BaseOverlay::sendMessage(const Message* message,
        const NodeID& node, const ServiceID& service) {

        // find link for node and service
        LinkDescriptor* ld = getAutoDescriptor( node, service );

        // if we found no link, create an auto link
        if( ld == NULL ) {

                // debug output
                logging_info( "No link to send message to node "
                        << node.toString() << " found for service "
                        << service.toString() << ". Creating auto link ..."
                );

                // this will call onlinkup on us, if everything worked we now have a mapping
                LinkID link = LinkID::create();

                // call base overlay to create a link
                link = establishLink( node, service, link );
                ld = getDescriptor( link );
                if( ld == NULL ) {
                        logging_error( "Failed to establish auto-link.");
                        return -1;
                }
                ld->autolink = true;

                logging_debug( "Auto-link establishment in progress to node "
                                << node.toString() << " with link id=" << link.toString() );
        }
        assert(ld != NULL);

        // mark the link as used, as we now send a message through it
        ld->markAsUsed();

        // send / queue message
        return sendMessage( message, ld->overlayId );
}

// ----------------------------------------------------------------------------

const EndpointDescriptor& BaseOverlay::getEndpointDescriptor(
                const LinkID& link) const {

        // return own end-point descriptor
        if( link == LinkID::UNSPECIFIED )
                return bc->getEndpointDescriptor();

        // find link descriptor. not found -> return unspecified
        const LinkDescriptor* ld = getDescriptor(link);
        if (ld==NULL) return EndpointDescriptor::UNSPECIFIED;

        // return endpoint-descriptor from base communication
        return bc->getEndpointDescriptor( ld->communicationId );
}

const EndpointDescriptor& BaseOverlay::getEndpointDescriptor(
                const NodeID& node) const {

        // return own end-point descriptor
        if( node == nodeId || node == NodeID::UNSPECIFIED )
                return bc->getEndpointDescriptor();

        // no joined and request remote descriptor? -> fail!
        if( overlayInterface == NULL ) {
                logging_error( "overlay interface not set, cannot resolve endpoint" );
                return EndpointDescriptor::UNSPECIFIED;
        }

        // resolve end-point descriptor from the base-overlay routing table
        return overlayInterface->resolveNode( node );
}

// ----------------------------------------------------------------------------

bool BaseOverlay::registerSidePort(SideportListener* _sideport) {
        sideport = _sideport;
        _sideport->configure( this );
}

bool BaseOverlay::unregisterSidePort(SideportListener* _sideport) {
        sideport = &SideportListener::DEFAULT;
}

// ----------------------------------------------------------------------------

bool BaseOverlay::bind(CommunicationListener* listener, const ServiceID& sid) {
        logging_debug( "binding communication listener " << listener
                        << " on serviceid " << sid.toString() );

        if( communicationListeners.contains( sid ) ) {
                logging_error( "some listener already registered for service id "
                                << sid.toString() );
                return false;
        }

        communicationListeners.registerItem( listener, sid );
        return true;
}


bool BaseOverlay::unbind(CommunicationListener* listener, const ServiceID& sid) {
        logging_debug( "unbinding listener " << listener << " from serviceid " << sid.toString() );

        if( !communicationListeners.contains( sid ) ) {
                logging_warn( "cannot unbind listener. no listener registered on service id " << sid.toString() );
                return false;
        }

        if( communicationListeners.get(sid) != listener ) {
                logging_warn( "listener bound to service id " << sid.toString()
                                << " is different than listener trying to unbind" );
                return false;
        }

        communicationListeners.unregisterItem( sid );
        return true;
}

// ----------------------------------------------------------------------------

bool BaseOverlay::bind(NodeListener* listener) {
        logging_debug( "Binding node listener " << listener );

        // already bound? yes-> warning
        NodeListenerVector::iterator i =
                find( nodeListeners.begin(), nodeListeners.end(), listener );
        if( i != nodeListeners.end() ) {
                logging_warn("Node listener " << listener << " is already bound!" );
                return false;
        }

        // no-> add
        nodeListeners.push_back( listener );
        return true;
}

bool BaseOverlay::unbind(NodeListener* listener) {
        logging_debug( "Unbinding node listener " << listener );

        // already unbound? yes-> warning
        NodeListenerVector::iterator i = find( nodeListeners.begin(), nodeListeners.end(), listener );
        if( i == nodeListeners.end() ) {
                logging_warn( "Node listener " << listener << " is not bound!" );
                return false;
        }

        // no-> remove
        nodeListeners.erase( i );
        return true;
}

// ----------------------------------------------------------------------------

void BaseOverlay::onLinkUp(const LinkID& id,
        const NetworkLocator* local, const NetworkLocator* remote) {
        logging_debug( "Link up with base communication link id=" << id );

        // get descriptor for link
        LinkDescriptor* ld = getDescriptor(id, true);

        // handle initiator link
        if(state == BaseOverlayStateJoinInitiated && id == initiatorLink) {
                logging_info(
                        "Join has been initiated by me and the link is now up. " <<
                        "Sending out join request for SpoVNet " << spovnetId.toString()
                );

                // send join request message
                OverlayMsg overlayMsg( OverlayMsg::typeJoinRequest, nodeId );
                JoinRequest joinRequest( spovnetId, nodeId );
                overlayMsg.encapsulate( &joinRequest );
                bc->sendMessage( id, &overlayMsg );
                return;
        }

        // no link found? -> link establishment from remote, add one!
        if (ld == NULL) {
                ld = addDescriptor( id );
                logging_debug( "onLinkUp (remote request) descriptor: " << ld );

                // update descriptor
                ld->fromRemote = true;
                ld->communicationId = id;
                ld->communicationUp = true;
                ld->markAsUsed();

                // in this case, do not inform listener, since service it unknown
                // -> wait for update message!

        // link mapping found? -> send update message with node-id and service id
        } else {
                logging_debug( "onLinkUp descriptor (initiated locally):" << ld );

                // note: necessary to validate the link on the remote side!
                logging_debug( "Sending out update" <<
                        " for service " << ld->service.toString() <<
                        " with local node id " << nodeId.toString() <<
                        " on link " << ld->overlayId.toString() );

                // update descriptor
                ld->markAsUsed();
                ld->communicationUp = true;

                // if link is a relayed link ->convert to direct link
                if (ld->relay) {
                        ld->up = true;
                        ld->relay = false;
                        ld->localRelay = NodeID::UNSPECIFIED;
                        OverlayMsg overMsg( OverlayMsg::typeDirectLink, ld->service, nodeId );
                        overMsg.setRelayLink( ld->remoteLinkId );
                        bc->sendMessage( ld->communicationId, &overMsg );
                }

                // compile and send update message
                OverlayMsg overlayMsg( OverlayMsg::typeUpdate, ld->service, nodeId );
                overlayMsg.setAutoLink( ld->autolink );
                bc->sendMessage( ld->communicationId, &overlayMsg );
        }
}

void BaseOverlay::onLinkDown(const LinkID& id,
        const NetworkLocator* local, const NetworkLocator* remote) {

        // get descriptor for link
        LinkDescriptor* ld = getDescriptor(id, true);
        if ( ld == NULL ) return; // not found? ->ignore!
        logging_force( "onLinkDown descriptor: " << ld );

        // inform listeners about link down
        ld->communicationUp = false;
        ld->listener->onLinkDown( ld->overlayId, ld->remoteNode );
        sideport->onLinkDown( id, this->nodeId, ld->remoteNode, this->spovnetId );

        // delete all queued messages (auto links)
        if( ld->messageQueue.size() > 0 ) {
                logging_warn( "Dropping link " << id.toString() << " that has "
                                << ld->messageQueue.size() << " waiting messages" );
                ld->flushQueue();
        }

        // erase mapping
        eraseDescriptor(ld->overlayId);
}

void BaseOverlay::onLinkChanged(const LinkID& id,
        const NetworkLocator* oldlocal, const NetworkLocator* newlocal,
        const NetworkLocator* oldremote, const NetworkLocator* newremote) {

        // get descriptor for link
        LinkDescriptor* ld = getDescriptor(id, true);
        if ( ld == NULL ) return; // not found? ->ignore!
        logging_debug( "onLinkChanged descriptor: " << ld );

        // inform listeners
        ld->listener->onLinkChanged( ld->overlayId, ld->remoteNode );
        sideport->onLinkChanged( id, this->nodeId, ld->remoteNode, this->spovnetId );

        // autolinks: refresh timestamp
        ld->markAsUsed();
}

void BaseOverlay::onLinkFail(const LinkID& id,
        const NetworkLocator* local, const NetworkLocator* remote) {
        logging_debug( "Link fail with base communication link id=" << id );

        // get descriptor for link
        LinkDescriptor* ld = getDescriptor(id, true);
        if ( ld == NULL ) return; // not found? ->ignore!
        logging_debug( "Link failed id=" << ld->overlayId.toString() );

        // inform listeners
        ld->listener->onLinkFail( ld->overlayId, ld->remoteNode );
        sideport->onLinkFail( id, this->nodeId, ld->remoteNode, this->spovnetId );

        // autolinks: refresh timestamp
        ld->markAsUsed();
}

void BaseOverlay::onLinkQoSChanged(const LinkID& id, const NetworkLocator* local,
        const NetworkLocator* remote, const QoSParameterSet& qos) {
        logging_debug( "Link quality changed with base communication link id=" << id );

        // get descriptor for link
        LinkDescriptor* ld = getDescriptor(id, true);
        if ( ld == NULL ) return; // not found? ->ignore!
        logging_debug( "Link quality changed id=" << ld->overlayId.toString() );

        // autolinks: refresh timestamp
        ld->markAsUsed();
}

bool BaseOverlay::onLinkRequest( const LinkID& id, const NetworkLocator* local,
        const NetworkLocator* remote ) {
        logging_debug("Accepting link request from " << remote->toString() );
        return true;
}

/// handles a message from base communication
bool BaseOverlay::receiveMessage(const Message* message,
                const LinkID& link, const NodeID& ) {
        // get descriptor for link
        LinkDescriptor* ld = getDescriptor( link, true );

        // link known?
        if (ld == NULL) { // no-> handle with unspecified params
                logging_debug("Received message from base communication, link descriptor unknown" );
                return handleMessage( message, LinkID::UNSPECIFIED, link, NodeID::UNSPECIFIED );
        } else { // yes -> handle with overlay link id
                logging_debug("Received message from base communication, link id=" << ld->overlayId.toString() );
                return handleMessage( message, ld->overlayId, link, NodeID::UNSPECIFIED );
        }
}

// ----------------------------------------------------------------------------

/// handles a message from an overlay
void BaseOverlay::incomingRouteMessage( Message* msg, const LinkID& link, const NodeID& source ) {
        logging_debug("Received message from overlay -- "
                << " link id=" << link.toString()
                << " node id=" << source.toString() );
        handleMessage( msg, link, LinkID::UNSPECIFIED, source );
}

// ----------------------------------------------------------------------------

/// handles an incoming message
bool BaseOverlay::handleMessage( const Message* message,
        const LinkID& boLink, const LinkID& bcLink, const NodeID& remoteNode ) {
        logging_debug( "Handling message: " << message->toString());

        // decapsulate overlay message
        OverlayMsg* overlayMsg =
                const_cast<Message*>(message)->decapsulate<OverlayMsg>();
        if( overlayMsg == NULL ) return false;

        // mark the link as in action
        LinkDescriptor* ld = getDescriptor(boLink);
        if (ld == NULL) ld = getDescriptor(bcLink, true);
        if (ld != NULL) {
                ld->markAsUsed();
                ld->markAlive();
        }

        switch ( overlayMsg->getType() ) {
                // ---------------------------------------------------------------------
                // Handle spovnet instance join requests
                // ---------------------------------------------------------------------
                case OverlayMsg::typeJoinRequest: {

                        // decapsulate message
                        JoinRequest* joinReq = overlayMsg->decapsulate<JoinRequest>();
                        logging_info( "Received join request for spovnet " <<
                                        joinReq->getSpoVNetID().toString() );

                        // check spovnet id
                        if( joinReq->getSpoVNetID() != spovnetId ) {
                                logging_error(
                                        "Received join request for spovnet we don't handle " <<
                                        joinReq->getSpoVNetID().toString() );
                                return false;
                        }

                        // TODO: here you can implement mechanisms to deny joining of a node
                        bool allow = true;
                        logging_info( "Sending join reply for spovnet " <<
                                        spovnetId.toString() << " to node " <<
                                        overlayMsg->getSourceNode().toString() <<
                                        ". Result: " << (allow ? "allowed" : "denied") );
                        joiningNodes.push_back( overlayMsg->getSourceNode() );

                        // return overlay parameters
                        assert( overlayInterface != NULL );
                        logging_debug( "Using bootstrap end-point "
                                << getEndpointDescriptor().toString() )
                        OverlayParameterSet parameters = overlayInterface->getParameters();
                        OverlayMsg retmsg( OverlayMsg::typeJoinReply, nodeId );
                        JoinReply replyMsg( spovnetId, parameters,
                                        allow, getEndpointDescriptor() );
                        retmsg.encapsulate(&replyMsg);
                        bc->sendMessage( bcLink, &retmsg );
                        return true;
                }

                // ---------------------------------------------------------------------
                // handle replies to spovnet instance join requests
                // ---------------------------------------------------------------------
                case OverlayMsg::typeJoinReply: {

                        // decapsulate message
                        logging_debug("received join reply message");
                        JoinReply* replyMsg = overlayMsg->decapsulate<JoinReply>();
                        assert(state == BaseOverlayStateJoinInitiated);

                        // correct spovnet?
                        if( replyMsg->getSpoVNetID() != spovnetId ) { // no-> fail
                                logging_error( "Received SpoVNet join reply for " <<
                                                replyMsg->getSpoVNetID().toString() <<
                                                " != " << spovnetId.toString() );
                                return false;
                        }

                        // access granted? no -> fail
                        if( !replyMsg->getJoinAllowed() ) {
                                logging_error( "Our join request has been denied" );

                                // drop initiator link
                                bc->dropLink( initiatorLink );
                                initiatorLink = LinkID::UNSPECIFIED;
                                state = BaseOverlayStateInvalid;

                                // inform all registered services of the event
                                BOOST_FOREACH( NodeListener* i, nodeListeners )
                                        i->onJoinFailed( spovnetId );
                                return true;
                        }

                        // access has been granted -> continue!
                        logging_info("Join request has been accepted for spovnet " <<
                                        spovnetId.toString() );

                        // create overlay structure from spovnet parameter set
                        overlayInterface = OverlayFactory::create(
                                *this, replyMsg->getParam(), nodeId, this );

                        // overlay structure supported? no-> fail!
                        if( overlayInterface == NULL ) {
                                logging_error( "overlay structure not supported" );

                                bc->dropLink( initiatorLink );
                                initiatorLink = LinkID::UNSPECIFIED;
                                state = BaseOverlayStateInvalid;

                                // inform all registered services of the event
                                BOOST_FOREACH( NodeListener* i, nodeListeners )
                                i->onJoinFailed( spovnetId );

                                return true;
                        }

                        // everything ok-> join the overlay!
                        state = BaseOverlayStateCompleted;
                        overlayInterface->createOverlay();
                        logging_debug( "Using bootstrap end-point "
                                << replyMsg->getBootstrapEndpoint().toString() );
                        overlayInterface->joinOverlay( replyMsg->getBootstrapEndpoint() );

                        // update ovlvis
                        ovl.visChangeNodeColor( ovlId, nodeId, OvlVis::NODE_COLORS_GREEN);

                        // inform all registered services of the event
                        BOOST_FOREACH( NodeListener* i, nodeListeners )
                                i->onJoinCompleted( spovnetId );

                        return true;
                }

                // ---------------------------------------------------------------------
                // handle data forward messages
                // ---------------------------------------------------------------------
                case OverlayMsg::typeData: {

                        // get service
                        const ServiceID& service = overlayMsg->getService();
                        logging_debug( "received data for service " << service.toString() );

                        // find listener
                        CommunicationListener* listener =
                                communicationListeners.get( service );
                        if( listener == NULL ) return true;

                        // delegate data message
                        listener->onMessage( overlayMsg,
                                overlayMsg->getSourceNode(), ld->overlayId );

                        return true;
                }

                // ---------------------------------------------------------------------
                // handle update messages for link establishment
                // ---------------------------------------------------------------------
                case OverlayMsg::typeUpdate: {
                        logging_debug("Received type update message on link " << ld );

                        // get info
                        const NodeID& sourcenode = overlayMsg->getSourceNode();
                        const ServiceID& service = overlayMsg->getService();

                        // no link descriptor available -> error!
                        if( ld == NULL ) {
                                logging_warn( "received overlay update message for link " <<
                                                ld->overlayId.toString() << " for which we have no mapping" );
                                return false;
                        }

                        // update our link mapping information for this link
                        bool changed =
                                ( ld->remoteNode != sourcenode ) || ( ld->service != service );
                        ld->remoteNode = sourcenode;
                        ld->service = service;
                        ld->autolink = overlayMsg->isAutoLink();

                        // if our link information changed, we send out an update, too
                        if( changed ) {
                                OverlayMsg overMsg( OverlayMsg::typeUpdate, ld->service, nodeId );
                                overMsg.setAutoLink(ld->autolink);
                                bc->sendMessage( ld->communicationId, &overMsg );
                        }

                        // service registered? no-> error!
                        if( !communicationListeners.contains( service ) ) {
                                logging_warn( "Link up: event listener has not been registered" );
                                return false;
                        }

                        // default or no service registered?
                        CommunicationListener* listener = communicationListeners.get( service );
                        if( listener == NULL || listener == &CommunicationListener::DEFAULT ) {
                                logging_warn("Link up: event listener is default or null!" );
                                return true;
                        }

                        // update descriptor
                        ld->listener = listener;
                        ld->markAsUsed();
                        ld->markAlive();

                        // ask the service whether it wants to accept this link
                        if( !listener->onLinkRequest(sourcenode) ) {

                                logging_debug("Link id=" << ld->overlayId.toString() <<
                                        " has been denied by service " << service.toString() << ", dropping link");

                                // prevent onLinkDown calls to the service
                                ld->listener = &CommunicationListener::DEFAULT;

                                // drop the link
                                dropLink( ld->overlayId );
                                return true;
                        }

                        // set link up
                        ld->up = true;
                        logging_debug(
                                   "Link " << ld->overlayId.toString()
                                << " has been accepted by service " << service.toString()
                                << " and is now up"
                        );

                        // auto links: link has been accepted -> send queued messages
                        if( ld->messageQueue.size() > 0 ) {
                                logging_info( "sending out queued messages on link " <<
                                        ld->overlayId.toString() );
                                BOOST_FOREACH( Message* msg, ld->messageQueue ) {
                                        sendMessage( msg, ld->overlayId );
                                        delete msg;
                                }
                                ld->messageQueue.clear();
                        }

                        // call the notification functions
                        listener->onLinkUp( ld->overlayId, sourcenode );
                        sideport->onLinkUp( ld->overlayId, nodeId, sourcenode, this->spovnetId );

                        return true;
                }

                // ---------------------------------------------------------------------
                // handle bye messages
                // ---------------------------------------------------------------------
                case OverlayMsg::typeBye: {
                        logging_debug( "received bye message from " <<
                                        overlayMsg->getSourceNode().toString() );

                        /* if we are the initiator and receive a bye from a node
                         * the node just left. if we are a node and receive a bye
                         * from the initiator, we have to close, too.
                         */
                        if( overlayMsg->getSourceNode() == spovnetInitiator ) {

                                bc->dropLink( initiatorLink );
                                initiatorLink = LinkID::UNSPECIFIED;
                                state = BaseOverlayStateInvalid;

                                logging_fatal( "initiator ended spovnet" );

                                // inform all registered services of the event
                                BOOST_FOREACH( NodeListener* i, nodeListeners )
                                        i->onLeaveFailed( spovnetId );

                        } else {
                                // a node that said goodbye and we are the initiator don't have to
                                // do much here, as the node also will go out of the overlay
                                // structure
                                logging_info( "node left " << overlayMsg->getSourceNode() );
                        }

                        return true;

                }

                // ---------------------------------------------------------------------
                // handle link request forwarded through the overlay
                // ---------------------------------------------------------------------
                case OverlayMsg::typeLinkRequest: {

                        // decapsulate message
                        LinkRequest* linkReq = overlayMsg->decapsulate<LinkRequest>();
                        const ServiceID& service = overlayMsg->getService();

                        // is request reply?
                        if ( linkReq->isReply() ) {

                                // find link
                                PendingLinkMap::iterator i = pendingLinks.find( linkReq->getNonce() );
                                if ( i == pendingLinks.end() ) {
                                        logging_error( "Nonce not found in link request" );
                                        return true;
                                }

                                // debug message
                                logging_debug( "Link request reply received. Establishing link "
                                        << i->second << " to " << (linkReq->getEndpoint()->toString())
                                        << " for service " << service.toString()
                                        << " with nonce "  << linkReq->getNonce()
                                        << " using relay " << linkReq->getRelay().toString()
                                        << " and remote link id=" << linkReq->getRemoteLinkId()
                                );

                                // get descriptor
                                LinkDescriptor* ldn = getDescriptor(i->second);

                                // check if link request reply has a relay node ...
                                if (!linkReq->getRelay().isUnspecified()) { // yes->
                                        ldn->up = true;
                                        ldn->relay = true;
                                        if (ldn->localRelay.isUnspecified())  {
                                                logging_error("On LinkRequest reply: local relay is unspecifed on link " << ldn );
                                                showLinkState();
                                        }
                                        ldn->remoteRelay  = linkReq->getRelay();
                                        ldn->remoteLinkId = linkReq->getRemoteLinkId();
                                        ldn->remoteNode   = overlayMsg->getSourceNode();

                                        ldn->markAlive();

                                        // compile and send update message
                                        OverlayMsg _overlayMsg( OverlayMsg::typeUpdate, ldn->service, nodeId );
                                        _overlayMsg.setAutoLink(ldn->autolink);
                                        sendMessage( &_overlayMsg, ldn );

                                        // auto links: link has been accepted -> send queued messages
                                        if( ldn->messageQueue.size() > 0 ) {
                                                logging_info( "Sending out queued messages on link " <<
                                                        ldn->overlayId.toString() );
                                                BOOST_FOREACH( Message* msg, ldn->messageQueue ) {
                                                        sendMessage( msg, ldn->overlayId );
                                                        delete msg;
                                                }
                                                ldn->messageQueue.clear();
                                        }

                                        ldn->listener->onLinkUp( ldn->overlayId, ldn->remoteNode );

                                        // try to establish a direct link
                                        ldn->communicationId =
                                                bc->establishLink( *linkReq->getEndpoint(), i->second );
                                }

                                // no relay node-> use overlay routing
                                else {
                                        ldn->up = true;

                                        // establish direct link
                                        ldn->communicationId =
                                                        bc->establishLink( *linkReq->getEndpoint(), i->second );
                                }
                        } else {
                                logging_debug( "Link request received from node id="
                                                << overlayMsg->getSourceNode() );

                                // create link descriptor
                                LinkDescriptor* ldn =
                                        createLinkDescriptor(overlayMsg->getSourceNode(),
                                                        overlayMsg->getService(), LinkID::UNSPECIFIED );
                                assert(!ldn->overlayId.isUnspecified());

                                // create reply message
                                OverlayMsg overlay_msg( OverlayMsg::typeLinkRequest, service, nodeId );
                                LinkRequest link_request_msg(
                                        linkReq->getNonce(),
                                        &bc->getEndpointDescriptor(),
                                        true, ldn->overlayId, ldn->localRelay
                                );
                                overlay_msg.encapsulate( &link_request_msg );

                                // debug message
                                logging_debug( "Sending LinkRequest reply for link with nonce " <<
                                                linkReq->getNonce() );

                                // if this is a relay link-> update information & inform listeners
                                if (!linkReq->getRelay().isUnspecified()) {
                                        // set flags
                                        ldn->up = true;
                                        ldn->relay = true;
                                        if (ldn->localRelay.isUnspecified()) {
                                                logging_error("On LinkRequest request: local relay is unspecifed on link " << ldn );
                                                showLinkState();
                                        }
                                        ldn->remoteRelay  = linkReq->getRelay();
                                        ldn->remoteNode   = overlayMsg->getSourceNode();
                                        ldn->remoteLinkId = linkReq->getRemoteLinkId();
                                        ldn->listener->onLinkUp( ldn->overlayId, ldn->remoteNode );
                                }

                                // route message back over overlay
                                sendMessage( &overlay_msg, ldn );
                        }
                        return true;
                }

                // ---------------------------------------------------------------------
                // handle relay message to forward messages
                // ---------------------------------------------------------------------
                case OverlayMsg::typeRelay: {

                        // decapsulate message
                        RelayMessage* relayMsg = overlayMsg->decapsulate<RelayMessage>();

                        // is relay message informative?
                        switch (relayMsg->getType()) {

                                // handle relay notification
                                case RelayMessage::typeInform: {
                                        logging_info("Received relay information message with"
                                                        << " relay " << relayMsg->getRelayNode()
                                                        << " destination " << relayMsg->getDestNode() );

                                        // mark incoming link as relay
                                        if (ld!=NULL) ld->markAsRelay();

                                        // am I the destination of this message? yes->
                                        if (relayMsg->getDestNode() == nodeId ) {
                                                // deliver relay message locally!
                                                logging_debug("Relay message reached destination. Handling the message.");
                                                handleMessage( relayMsg, relayMsg->getDestLink(), LinkID::UNSPECIFIED, remoteNode );
                                                return true;
                                        }

                                        // create route message
                                        OverlayMsg _overMsg( *overlayMsg );
                                        RelayMessage _relayMsg( *relayMsg );
                                        _relayMsg.setType( RelayMessage::typeRoute );
                                        _overMsg.encapsulate( &_relayMsg );

                                        // forward message
                                        if (relayMsg->getRelayNode() == nodeId || relayMsg->getRelayNode().isUnspecified()) {
                                                logging_info("Routing relay message to " << relayMsg->getDestNode().toString() );
                                                overlayInterface->routeMessage(relayMsg->getDestNode(), &_overMsg );
                                        } else {
                                                logging_info("Routing relay message to " << relayMsg->getRelayNode().toString() );
                                                overlayInterface->routeMessage(relayMsg->getRelayNode(), &_overMsg );
                                        }
                                        return true;
                                }

                                // handle relay routing
                                case RelayMessage::typeRoute: {
                                        logging_info("Received relay route message with"
                                                        << " relay " << relayMsg->getRelayNode()
                                                        << " destination " << relayMsg->getDestNode() );

                                        // mark incoming link as relay
                                        if (ld!=NULL) ld->markAsRelay();

                                        // am I the destination of this message? yes->
                                        if (relayMsg->getDestNode() == nodeId ) {
                                                // deliver relay message locally!
                                                logging_debug("Relay message reached destination. Handling the message.");
                                                handleMessage( relayMsg, relayMsg->getDestLink(), LinkID::UNSPECIFIED, remoteNode );
                                                return true;
                                        }

                                        // am I the relay for this message? yes->
                                        if (relayMsg->getRelayNode() == nodeId ) {
                                                logging_debug("I'm the relay for this message. Sending to destination.");
                                                OverlayMsg _overMsg( *overlayMsg );
                                                RelayMessage _relayMsg( *relayMsg );
                                                _overMsg.encapsulate(&_relayMsg);

                                                /// this must be handled by using relay link!
                                                overlayInterface->routeMessage(relayMsg->getDestNode(), &_overMsg );
                                                return true;
                                        }

                                        // error: I'm not a relay or destination!
                                        logging_error("This node is neither relay nor destination. Dropping Message!");
                                        return true;
                                }
                                default: {
                                        logging_error("RelayMessage Unknown!");
                                        return true;
                                }
                        }

                        break;
                }

                // ---------------------------------------------------------------------
                // handle keep-alive messages
                // ---------------------------------------------------------------------
                case OverlayMsg::typeKeepAlive: {
                        if ( ld != NULL ) {
                                //logging_force("Keep-Alive for "<< ld->overlayId);
                                ld->markAlive();
                        }
                        break;
                }

                // ---------------------------------------------------------------------
                // handle direct link replacement messages
                // ---------------------------------------------------------------------
                case OverlayMsg::typeDirectLink: {
                        LinkDescriptor* rld = getDescriptor( overlayMsg->getRelayLink() );
                        rld->communicationId = ld->communicationId;
                        rld->communicationUp = true;
                        rld->relay = false;
                        rld->localRelay = NodeID::UNSPECIFIED;
                        rld->remoteRelay = NodeID::UNSPECIFIED;
                        eraseDescriptor(ld->overlayId);
                        break;
                }

                // ---------------------------------------------------------------------
                // handle unknown message type
                // ---------------------------------------------------------------------
                default: {
                        logging_error( "received message in invalid state! don't know " <<
                                        "what to do with this message of type " <<
                                        overlayMsg->getType() );
                        return false;
                }

        } /* switch */
        return false;
}

// ----------------------------------------------------------------------------

void BaseOverlay::broadcastMessage(Message* message, const ServiceID& service) {

        logging_debug( "broadcasting message to all known nodes " <<
                        "in the overlay from service " + service.toString() );

        OverlayInterface::NodeList nodes = overlayInterface->getKnownNodes();
        OverlayInterface::NodeList::iterator i = nodes.begin();
        for(; i != nodes.end(); i++ ) {
                if( *i == nodeId) continue; // don't send to ourselfs
                sendMessage( message, *i, service );
        }
}

vector<NodeID> BaseOverlay::getOverlayNeighbors() const {
        // the known nodes _can_ also include our node, so we remove ourself
        vector<NodeID> nodes = overlayInterface->getKnownNodes();
        vector<NodeID>::iterator i = find( nodes.begin(), nodes.end(), this->nodeId );
        if( i != nodes.end() ) nodes.erase( i );
        return nodes;
}

const NodeID& BaseOverlay::getNodeID(const LinkID& lid) const {
        if( lid == LinkID::UNSPECIFIED ) return nodeId;
        const LinkDescriptor* ld = getDescriptor(lid);
        if( ld == NULL ) return NodeID::UNSPECIFIED;
        else return ld->remoteNode;
}

vector<LinkID> BaseOverlay::getLinkIDs( const NodeID& nid ) const {
        vector<LinkID> linkvector;
        BOOST_FOREACH( LinkDescriptor* ld, links ) {
                if( ld->remoteNode == nid || nid == NodeID::UNSPECIFIED ) {
                        linkvector.push_back( ld->overlayId );
                }
        }
        return linkvector;
}


void BaseOverlay::onNodeJoin(const NodeID& node) {
        JoiningNodes::iterator i = std::find( joiningNodes.begin(), joiningNodes.end(), node );
        if( i == joiningNodes.end() ) return;

        logging_info( "node has successfully joined baseoverlay and overlay structure "
                        << node.toString() );

        joiningNodes.erase( i );
}

void BaseOverlay::eventFunction() {

        // send keep-alive messages over established links
        BOOST_FOREACH( LinkDescriptor* ld, links ) {
                if (!ld->up) continue;
                OverlayMsg overMsg( OverlayMsg::typeKeepAlive,
                        OverlayInterface::OVERLAY_SERVICE_ID, nodeId );
                sendMessage( &overMsg, ld );
        }

        // iterate over all links and check for time boundaries
        vector<LinkDescriptor*> oldlinks;
        time_t now = time(NULL);
        BOOST_FOREACH( LinkDescriptor* ld, links ) {
                // remote used as relay flag
                if ( ld->usedAsRelay && difftime( now, ld->timeUsedAsRelay ) > 10)
                        ld->usedAsRelay = false;

                // keep alives missed? yes->
                if ( !ld->up && difftime( now, ld->keepAliveTime ) > 2 ) {

                        // increase counter
                        ld->keepAliveMissed++;

                        // missed more than four keep-alive messages (4 sec)? -> drop link
                        if (ld->keepAliveMissed > 10) {
                                logging_force( "Link connection request is stale, closing: " << ld );
                                oldlinks.push_back( ld );
                        }
                }

                if (!ld->up) continue;

                // drop links that are dropped and not used as relay
                if (ld->dropWhenRelaysLeft && !ld->usedAsRelay && !ld->autolink)
                        oldlinks.push_back( ld );
                else

                // auto-link time exceeded?
                if ( ld->autolink && difftime( now, ld->lastuse ) > 30 )
                        oldlinks.push_back( ld );

                else

                // keep alives missed? yes->
                if ( !ld->autolink && difftime( now, ld->keepAliveTime ) > 2 ) {

                        // increase counter
                        ld->keepAliveMissed++;

                        // missed more than four keep-alive messages (4 sec)? -> drop link
                        if (ld->keepAliveMissed >= 8) {
                                logging_force( "Link is stale, closing: " << ld );
                                oldlinks.push_back( ld );
                        }
                }
        }

        // show link state
        counter++;
        if (counter>=4) showLinkState();
        if (counter>=4 || counter<0) counter = 0;

        // drop links
        BOOST_FOREACH( const LinkDescriptor* ld, oldlinks ) {
                if (!ld->communicationId.isUnspecified() && ld->communicationId == initiatorLink) {
                        logging_force( "Not dropping initiator link: " << ld );
                        continue;
                }
                logging_force( "Link timed out. Dropping " << ld );
                dropLink( ld->overlayId );
        }
}

void BaseOverlay::showLinkState() {
        int i=0;
        logging_force("--- link state -------------------------------");
        BOOST_FOREACH( LinkDescriptor* ld, links ) {
                logging_force("link " << i << ": " << ld);
                i++;
        }
        logging_force("----------------------------------------------");
}

}} // namespace ariba, overlay