Implements the shared coaxial cable in classic Ethernet. More...

#include <EtherBus.h>

Inheritance diagram for inet::EtherBus:

Classes
struct	BusTap
	Implements the physical locations on the bus where each network entity is connected to on the bus. More...

Public Member Functions
	EtherBus ()

virtual	~EtherBus ()

Protected Member Functions
virtual void	initialize () override

virtual void	handleMessage (cMessage *msg) override

virtual void	finish () override

virtual void	receiveSignal (cComponent source, simsignal_t signalID, cObject obj, cObject *details) override

virtual void	checkConnections (bool errorWhenAsymmetric)

Protected Attributes
double	propagationSpeed = NaN

BusTap *	tap = nullptr

int	numTaps = -1

int	inputGateBaseId = -1

int	outputGateBaseId = -1

bool	dataratesDiffer = false

long	numMessages = 0

Detailed Description

Implements the shared coaxial cable in classic Ethernet.

See the NED file for more description.

Constructor & Destructor Documentation

inet::EtherBus::EtherBus ( )

32 {

33 }

inet::EtherBus::~EtherBus ( )

virtual

 {
     delete[] tap;
 }

Member Function Documentation

void inet::EtherBus::checkConnections ( bool errorWhenAsymmetric )

protectedvirtual

Referenced by handleMessage(), initialize(), and receiveSignal().

 {
     int numActiveTaps = 0;
 
     double datarate = 0.0;
 
     for (int i = 0; i < numTaps; i++) {
         cGate *igate = gate(inputGateBaseId + i);
         cGate *ogate = gate(outputGateBaseId + i);
         if (!igate->isConnected() && !ogate->isConnected())
             continue;
 
         if (!igate->isConnected() || !ogate->isConnected()) {
             // half connected gate
             if (errorWhenAsymmetric)
                 throw cRuntimeError("The input or output gate not connected at tap %i", i);
             dataratesDiffer = true;
             EV << "The input or output gate not connected at tap " << i << ".\n";
             continue;
         }
 
         numActiveTaps++;
         double drate = igate->getIncomingTransmissionChannel()->getNominalDatarate();
 
         if (numActiveTaps == 1)
             datarate = drate;
         else if (datarate != drate) {
             if (errorWhenAsymmetric)
                 throw cRuntimeError("The input datarate at tap %i differs from datarates of previous taps", i);
             dataratesDiffer = true;
             EV << "The input datarate at tap " << i << " differs from datarates of previous taps.\n";
         }
 
         cChannel *outTrChannel = ogate->getTransmissionChannel();
         drate = outTrChannel->getNominalDatarate();
 
         if (datarate != drate) {
             if (errorWhenAsymmetric)
                 throw cRuntimeError("The output datarate at tap %i differs from datarates of previous taps", i);
             dataratesDiffer = true;
             EV << "The output datarate at tap " << i << " differs from datarates of previous taps.\n";
         }
 
         if (!outTrChannel->isSubscribed(POST_MODEL_CHANGE, this))
             outTrChannel->subscribe(POST_MODEL_CHANGE, this);
     }
 }

void inet::EtherBus::finish ( )

overrideprotectedvirtual

 {
     simtime_t t = simTime();
     recordScalar("simulated time", t);
     recordScalar("messages handled", numMessages);
 
     if (t > 0)
         recordScalar("messages/sec", numMessages / t);
 }

void inet::EtherBus::handleMessage ( cMessage * msg )

overrideprotectedvirtual

 {
     if (dataratesDiffer)
         checkConnections(true);
 
     if (!msg->isSelfMessage()) {
         // Handle frame sent down from the network entity
         int tapPoint = msg->getArrivalGate()->getIndex();
         EV << "Frame " << msg << " arrived on tap " << tapPoint << endl;
 
         // create upstream and downstream events
         if (tapPoint > 0) {
             // start UPSTREAM travel
             // if goes downstream too, we need to make a copy
             cMessage *msg2 = (tapPoint < numTaps - 1) ? msg->dup() : msg;
             msg2->setKind(UPSTREAM);
             msg2->setContextPointer(&tap[tapPoint - 1]);
             scheduleAt(simTime() + tap[tapPoint].propagationDelay[UPSTREAM], msg2);
         }
 
         if (tapPoint < numTaps - 1) {
             // start DOWNSTREAM travel
             msg->setKind(DOWNSTREAM);
             msg->setContextPointer(&tap[tapPoint + 1]);
             scheduleAt(simTime() + tap[tapPoint].propagationDelay[DOWNSTREAM], msg);
         }
 
         if (numTaps == 1) {
             // if there's only one tap, there's nothing to do
             delete msg;
         }
     }
     else {
         // handle upstream and downstream events
         int direction = msg->getKind();
         BusTap *thistap = (BusTap *)msg->getContextPointer();
         int tapPoint = thistap->id;
 
         EV << "Event " << msg << " on tap " << tapPoint << ", sending out frame\n";
 
         // send out on gate
         bool isLast = (direction == UPSTREAM) ? (tapPoint == 0) : (tapPoint == numTaps - 1);
         cGate *ogate = gate(outputGateBaseId + tapPoint);
         if (ogate->isConnected()) {
             // send out on gate
             cMessage *msg2 = isLast ? msg : msg->dup();
 
             // stop current transmission
             ogate->getTransmissionChannel()->forceTransmissionFinishTime(SIMTIME_ZERO);
             send(msg2, ogate);
         }
         else {
             // skip gate
             if (isLast)
                 delete msg;
         }
 
         // if not end of the bus, schedule for next tap
         if (isLast) {
             EV << "End of bus reached\n";
         }
         else {
             EV << "Scheduling for next tap\n";
             int nextTap = (direction == UPSTREAM) ? (tapPoint - 1) : (tapPoint + 1);
             msg->setContextPointer(&tap[nextTap]);
             scheduleAt(simTime() + tap[tapPoint].propagationDelay[direction], msg);
         }
     }
 }

void inet::EtherBus::initialize ( )

overrideprotectedvirtual

 {
     numMessages = 0;
     WATCH(numMessages);
 
     propagationSpeed = par("propagationSpeed").doubleValue();
 
     // initialize the positions where the hosts connects to the bus
     numTaps = gateSize("ethg");
     inputGateBaseId = gateBaseId("ethg$i");
     outputGateBaseId = gateBaseId("ethg$o");
 
     // read positions and check if positions are defined in order (we're lazy to sort...)
     std::vector<double> pos = cStringTokenizer(par("positions").stringValue()).asDoubleVector();
     int numPos = pos.size();
 
     if (numPos > numTaps)
         EV << "Note: `positions' parameter contains more values (" << numPos << ") than "
                                                                                 "the number of taps (" << numTaps << "), ignoring excess values.\n";
     else if (numPos < numTaps && numPos >= 2)
         EV << "Note: `positions' parameter contains less values (" << numPos << ") than "
                                                                                 "the number of taps (" << numTaps << "), repeating distance between last 2 positions.\n";
     else if (numPos < numTaps && numPos < 2)
         EV << "Note: `positions' parameter contains too few values, using 5m distances.\n";
 
     tap = new BusTap[numTaps];
 
     int i;
     double distance = numPos >= 2 ? pos[numPos - 1] - pos[numPos - 2] : 5;
 
     for (i = 0; i < numTaps; i++) {
         tap[i].id = i;
         tap[i].position = i < numPos ? pos[i] : i == 0 ? 5 : tap[i - 1].position + distance;
     }
 
     for (i = 0; i < numTaps - 1; i++) {
         if (tap[i].position > tap[i + 1].position)
             throw cRuntimeError("Tap positions must be ordered in ascending fashion, modify 'positions' parameter and rerun\n");
     }
 
     // Prints out data of parameters for parameter checking...
     EV << "Parameters of (" << getClassName() << ") " << getFullPath() << "\n";
     EV << "propagationSpeed: " << propagationSpeed << "\n";
 
     // Calculate propagation of delays between tap points on the bus
     for (i = 0; i < numTaps; i++) {
         // Propagation delay between adjacent tap points
         tap[i].propagationDelay[UPSTREAM] = (i > 0) ? tap[i - 1].propagationDelay[DOWNSTREAM] : 0;
         tap[i].propagationDelay[DOWNSTREAM] = (i + 1 < numTaps) ? (tap[i + 1].position - tap[i].position) / propagationSpeed : 0;
         EV << "tap[" << i << "] pos: " << tap[i].position
            << "  upstream delay: " << tap[i].propagationDelay[UPSTREAM]
            << "  downstream delay: " << tap[i].propagationDelay[DOWNSTREAM] << endl;
     }
     EV << "\n";
 
     // ensure we receive frames when their first bits arrive
     for (int i = 0; i < numTaps; i++)
         gate(inputGateBaseId + i)->setDeliverOnReceptionStart(true);
     subscribe(POST_MODEL_CHANGE, this);    // we'll need to do the same for dynamically added gates as well
 
     checkConnections(true);
 }

void inet::EtherBus::receiveSignal	(	cComponent *	source,
		simsignal_t	signalID,
		cObject *	obj,
		cObject *	details
	)

overrideprotectedvirtual

 {
     Enter_Method_Silent();
 
     ASSERT(signalID == POST_MODEL_CHANGE);
 
     // throw error if new gates have been added
     cPostGateVectorResizeNotification *notif = dynamic_cast<cPostGateVectorResizeNotification *>(obj);
     if (notif) {
         if (strcmp(notif->gateName, "ethg") == 0)
             throw cRuntimeError("EtherBus does not allow adding/removing links dynamically");
     }
 
     cPostPathCreateNotification *connNotif = dynamic_cast<cPostPathCreateNotification *>(obj);
     if (connNotif) {
         if ((this == connNotif->pathStartGate->getOwnerModule()) || (this == connNotif->pathEndGate->getOwnerModule()))
             checkConnections(false);
         return;
     }
 
     cPostPathCutNotification *cutNotif = dynamic_cast<cPostPathCutNotification *>(obj);
     if (cutNotif) {
         if ((this == cutNotif->pathStartGate->getOwnerModule()) || (this == cutNotif->pathEndGate->getOwnerModule()))
             checkConnections(false);
         return;
     }
 
     // note: we are subscribed to the channel object too
     cPostParameterChangeNotification *parNotif = dynamic_cast<cPostParameterChangeNotification *>(obj);
     if (parNotif) {
         cChannel *channel = dynamic_cast<cDatarateChannel *>(parNotif->par->getOwner());
         if (channel) {
             cGate *gate = channel->getSourceGate();
             if (gate->pathContains(this))
                 checkConnections(false);
         }
         return;
     }
 }