rrep.java

DSr project for the java applications

package dsr;


import java.lang.*;
import java.io.*;
import java.util.*;
import java.net.*;

//this class implements the generation and reception of a RREP packet
public class RREP {
  //this function takes care of receiving an RREP packet. It first gets the RREP packet
  //from the datagram packet and decodes it. It then updates the routing table (if needed)
  //with the information in the RREP packet. And then if it is not the intended destination
  //it forwards the packet towards the source
  public static void recvRREP(EventQueueEntry workingEvent) {
    RREPPacket rrep = new RREPPacket();
    rrep = rrep.decode(workingEvent.packet);      //decodes the datagram packet
    System.out.println("inside recvRREP");
    //increase the hopCount.
    rrep.hopCount++;
    //check to see if it has a valid route to the destination that is mentioned in the
    //RREP packet.
    RouteTable.PrintRouteTable();
    int pos = RouteTable.FindRouteTableEntry(rrep.dstIPAddr);
    RouteTableEntry tmpRoute =
          new RouteTableEntry(rrep.dstIPAddr, workingEvent.srcIP, rrep.hopCount, (byte)0);
    if (pos == -1) { //does not have an entry to that destination
      //should update its own routing table with that info.
      RouteTable.AddRouteTableEntry(tmpRoute);
    }
    else {
      RouteTableEntry entry = new RouteTableEntry(RouteTable.getThisEntry(pos));
      //checks to see if the new information provides a better route to destination
      if (entry.hopCount > rrep.hopCount) {
        RouteTable.DeleteRouteTableEntry(pos);
        RouteTable.AddRouteTableEntry(tmpRoute);
      }
    }

    //update the route table for the node from where the RREP was received
    pos = RouteTable.FindRouteTableEntry(workingEvent.srcIP);
    if (pos == -1) {
      RouteTable.AddRouteTableEntry(new RouteTableEntry(workingEvent.srcIP,
          workingEvent.srcIP, (byte)1, (byte)0));
    }

    //need to check first if this packet was meant for me or not....
    //if it is meant for me.. do nothing.. we have already taken care of that.
    //InterfaceList.findInterface();
    if (!InterfaceList.checkIfInterfacePresent(rrep.orgIPAddr)) {
      //it then gets the next hop for the destination and forwards the packet to the source that
      //needs the RREP packet.
      pos = RouteTable.FindRouteTableEntry(rrep.orgIPAddr);
      tmpRoute = RouteTable.getThisEntry(pos);
      send(rrep, tmpRoute.nextHop);
    }
    RouteTable.PrintRouteTable();
  }

  //this function handles the generation of a RREP packet. So first if i was the one who is the
  //destination required by the RREQ packet then i go ahead generate an RREP and send it to the
  //next hop towards the source. if i am not destination but have a route to the destination then
  //i send the RREP packet to the source and also send that to the destination so that the
  //destination also has the reverse route to the source.
  public static void genRREP(RREQPacket rreq, InetAddress recvAddr) {
    //get the src and destination address from the RREQ
    InetAddress src = rreq.srcIPAddr;
    InetAddress dst = rreq.dstIPAddr;

    //if i am the destination then i generate an RREP and send it to the next hop
    RREPPacket outRREP = new RREPPacket(Const.RREP_TYPE, (byte)0, 0, dst, src);
    int pos = RouteTable.FindRouteTableEntry(dst);
    if (pos != -1){
      RouteTableEntry tmpRoute = new RouteTableEntry(RouteTable.getThisEntry(pos));
      if(tmpRoute.selfRoute == (byte)0) {
        //i am the destination for that RREQ just send back the packet
        System.out.println("it is the destination os it just sends the RREP to ");
        send(outRREP, recvAddr);
        System.out.println(recvAddr);
      }
      else {
        //i am not the destination but there is a route through me
        System.out.println("it is not the destination, so it sends the RREP both ways");
        send(outRREP, recvAddr);
        System.out.println(recvAddr);
        send(outRREP, tmpRoute.nextHop);
        System.out.println(tmpRoute.nextHop);
      }
    }
  }

  //sends the packet to the next hop
  public static void send(RREPPacket r, InetAddress dst) {
    byte[] bytesToSend = r.encode(r);
    DatagramPacket sendPacket = new DatagramPacket(bytesToSend, bytesToSend.length,
          dst, Const.DSRPORT);
    //send it to that particular socket.

    InetAddress localAddress =
        ((InterfaceListEntry)InterfaceList.interfaceList.lastElement()).ipAddress;
    try{
      DatagramSocket sock = new DatagramSocket(0, localAddress);
      try {
        sock.send(sendPacket);
      }catch (IOException e) {}
    } catch (SocketException e) {}
  }
}