How can I combine my customize module with Omnet++INET's simple module

Question

As all the simple modules' behavior like 80211 mac layer has been defined in the INET module. If I want to add a customize layer between mac layer and network layer to handle network coding. How can I combine the customize module and INET's simple module ?

Answer 1

To add a new module between network layer and MAC layer I suggest creating a modified host in a new project. For OMNeT++ 4.6 and INET 3.2.4 do the following:

1. Create a new OMNeT++ empty project with src and simulation directories.
2. In the new project open Properties | Project References and select inet.
3. Right click on src and select New | Simple module. Call it DummyLayer.ned.

4. Open DummyLayer.ned and add:

   @namespace(inet);
   import inet.linklayer.contract.INic;
   
   simple DummyLayer like INic {
   parameters:
       @display("i=block/buffer");
       // here you can add others parameter
   gates:
       input ifIn;
       output ifOut;
       input upperLayerIn;
       output upperLayerOut;
   }
   

5. Modify DummyLayer.h and DummyLayer.cc (this module just passes every message from up and down, as well as increments counters):

   // DummyLayer.h
   #include <omnetpp.h>
   namespace inet {
   class DummyLayer: public cSimpleModule {
   protected:
       virtual void initialize();
       virtual void handleMessage(cMessage *msg);
   private:
       int upNumber;
       int downNumber;
   };
   } //namespace
   
   //----------------------------------------------
   // DummyLayer.cc
   #include "DummyLayer.h"
   namespace inet {
   Define_Module(DummyLayer);
   
   void DummyLayer::initialize() {
      upNumber = 0;
      downNumber = 0;
   }
   
   void DummyLayer::handleMessage(cMessage *msg) {
     if (msg->arrivedOn("upperLayerIn")) {
         send(msg, "ifOut");
         downNumber++;
     } else if (msg->arrivedOn("ifIn")) {
         send(msg, "upperLayerOut");
         upNumber++;
     } else {
         error("Incorrect gate");
     }
     char buf[128];
     sprintf(buf, "up: %d, down: %d", upNumber, downNumber);
     getDisplayString().setTagArg("t", 0, buf);
     }
   } //namespace
   

6. Create a new compound module for own host, call it WirelessHostEx.ned:

   import inet.common.lifecycle.NodeStatus;
   import inet.linklayer.contract.IWiredNic;
   import inet.linklayer.contract.IWirelessNic;
   import inet.linklayer.loopback.LoopbackInterface;
   import inet.mobility.contract.IMobility;
   import inet.networklayer.contract.IRoutingTable;
   import inet.networklayer.common.InterfaceTable;
   import inet.networklayer.contract.INetworkLayer;
   import inet.power.contract.IEnergyStorage;
   import inet.power.contract.IEnergyGenerator;
   import inet.applications.contract.IPingApp;
   import inet.applications.contract.ISCTPApp;
   import inet.applications.contract.ITCPApp;
   import inet.applications.contract.IUDPApp;
   import inet.transportlayer.contract.ISCTP;
   import inet.transportlayer.contract.ITCP;
   import inet.transportlayer.contract.IUDP;
   import inet.node.inet.INetworkNode;
   
   module WirelessHostEx like INetworkNode
   {
       parameters:
           @networkNode;
           @display("i=device/wifilaptop");
           @labels(wireless-node);
           bool hasStatus = default(false);
           int numExtInterfaces = default(0);
           int numRadios = 1;
           int numTunInterfaces = default(0);
           string mobilityType = default(numRadios > 0 ? "StationaryMobility" : "");
           string networkLayerType = default("IPv4NetworkLayer");
           string routingTableType = default("IPv4RoutingTable");
           bool forwarding = default(true);
           bool multicastForwarding = default(false);
           string energyStorageType = default("");
           string energyGeneratorType = default("");
           routingTable.forwarding = forwarding;
           routingTable.multicastForwarding = multicastForwarding;  
           *.interfaceTableModule = default(absPath(".interfaceTable"));
           *.routingTableModule = default(routingTableType != "" ? absPath(".routingTable") : "");
           *.energySourceModule = default(energyStorageType != "" ? absPath(".energyStorage") : "");
           *.mobilityModule = default(mobilityType != "" ? absPath(".mobility") : "");
           int numTcpApps = default(0);
           int numUdpApps = default(0); 
           int numPingApps = default(0); 
           bool hasTcp = default(numTcpApps > 0);
           bool hasUdp = default(numUdpApps > 0);
           string tcpType = default(firstAvailableOrEmpty("TCP", "TCP_lwIP", "TCP_NSC"));  // tcp implementation (e.g. ~TCP, ~TCP_lwIP, ~TCP_NSC) or ~TCPSpoof
           string udpType = default(firstAvailableOrEmpty("UDP"));
           forwarding = default(false);  // disable routing by default
           networkLayer.proxyARP = default(false);
       gates:
           input radioIn[numRadios] @directIn;
           inout pppg[] @labels(PPPFrame-conn);
           inout ethg[] @labels(EtherFrame-conn);
       submodules:
           status: NodeStatus if hasStatus {
               @display("p=50,50");
           }
           energyStorage: <energyStorageType> like IEnergyStorage if energyStorageType != "" {
               parameters:
                   @display("p=50,100;i=block/plug;is=s");
           }
           energyGenerator: <energyGeneratorType> like IEnergyGenerator if energyGeneratorType != "" {
               parameters:
                   @display("p=50,150;i=block/plug;is=s");
           }
           mobility: <mobilityType> like IMobility if mobilityType != "" {
               parameters:
                   @display("p=53,200");
           }
           networkLayer: <networkLayerType> like INetworkLayer {
               parameters:
                   @display("p=329,287;q=queue");
           }
           routingTable: <routingTableType> like IRoutingTable if routingTableType != "" {
               parameters:
                   @display("p=53,250;is=s");
           }
           interfaceTable: InterfaceTable {
               parameters:
                   @display("p=53,300;is=s");
           }
           lo0: LoopbackInterface {
               @display("p=78,406");
           }
           wlan[numRadios]: <default("Ieee80211Nic")> like IWirelessNic {
               parameters:
                   @display("p=216,406,row,60;q=queue");
           }
           eth[sizeof(ethg)]: <default("EthernetInterface")> like IWiredNic {
               parameters:
                   @display("p=368,406,row,60;q=txQueue");
           }
           ppp[sizeof(pppg)]: <default("PPPInterface")> like IWiredNic {
               parameters:
                   @display("p=558,406,row,60;q=txQueue");
           }
           tcpApp[numTcpApps]: <> like ITCPApp {
               parameters:
                   @display("p=147,54,row,60");
           }
           tcp: <tcpType> like ITCP if hasTcp {
               parameters:
                   @display("p=147,141");
           }
           udpApp[numUdpApps]: <> like IUDPApp {
               parameters:
                   @display("p=329,54,row,60");
           }
           udp: <udpType> like IUDP if hasUdp {
               parameters:
                   @display("p=329,141");
           }
           pingApp[numPingApps]: <default("PingApp")> like IPingApp {
               parameters:
                   @display("p=635,141,row,60");
           }
           dummy: DummyLayer {
               @display("p=273,350");
           }
       connections allowunconnected:
           radioIn[0] --> { @display("m=s"); } --> wlan[0].radioIn;
           // the order of connections is important here
           wlan[0].upperLayerOut --> dummy.ifIn;
           dummy.upperLayerOut --> networkLayer.ifIn++;
           wlan[0].upperLayerIn <-- dummy.ifOut;
           dummy.upperLayerIn <-- networkLayer.ifOut++;
           networkLayer.ifOut++ --> lo0.upperLayerIn;
           lo0.upperLayerOut --> networkLayer.ifIn++;
           for i=0..sizeof(ethg)-1 {
               ethg[i] <--> { @display("m=s"); } <--> eth[i].phys;
               eth[i].upperLayerOut --> networkLayer.ifIn++;
               eth[i].upperLayerIn <-- networkLayer.ifOut++;
           }
           for i=0..sizeof(pppg)-1 {
               pppg[i] <--> { @display("m=s"); } <--> ppp[i].phys;
               ppp[i].upperLayerOut --> networkLayer.ifIn++;
               ppp[i].upperLayerIn <-- networkLayer.ifOut++;
           }
           for i=0..numTcpApps-1 {
               tcpApp[i].tcpOut --> tcp.appIn++;
               tcpApp[i].tcpIn <-- tcp.appOut++;
           }
           tcp.ipOut --> networkLayer.transportIn++ if hasTcp;
           tcp.ipIn <-- networkLayer.transportOut++ if hasTcp;
           for i=0..numUdpApps-1 {
               udpApp[i].udpOut --> udp.appIn++;
               udpApp[i].udpIn <-- udp.appOut++;
           }
           udp.ipOut --> networkLayer.transportIn++ if hasUdp;
           udp.ipIn <-- networkLayer.transportOut++ if hasUdp;
           for i=0..numPingApps-1 {
               networkLayer.pingOut++ --> pingApp[i].pingIn;
               networkLayer.pingIn++ <-- pingApp[i].pingOut;
           }
   }
   

An own host module is necessary because StandardHost from INET creates connection between MAC and network layer automatically and it is not possible to add own module between these layers.

7. Create a network (for test):

   import inet.networklayer.configurator.ipv4.IPv4NetworkConfigurator;
   import inet.physicallayer.ieee80211.packetlevel.Ieee80211ScalarRadioMedium;
   import inet.node.wireless.AccessPoint;
   
   network WirelessNetwork {
       submodules:
           configurator: IPv4NetworkConfigurator {
               @display("p=33,81");
           }
           radioMedium: Ieee80211ScalarRadioMedium {
               @display("p=33,30");
           }
           node0: WirelessHostEx {
               @display("p=128,121");
           }
           node1: WirelessHostEx {
               @display("p=384,115");
           }
           ap: AccessPoint {
               @display("p=273,54");
           }
   }
   

8. Modify omnetpp.ini:

   [General]
   network = WirelessNetwork
   
   // node0 will send ping to node1
   **.node0.numPingApps = 1
   **.node0.pingApp[0].destAddr = "node1" // using IP address here is allowed too
   

After starting the simulation one can see that in each host dummyLayer send messages forward.