code: package cic.cs.unb.ca.jnetpcap;
  
  import org.jnetpcap.Pcap;
  import org.jnetpcap.PcapClosedException;
  import org.jnetpcap.PcapHeader;
  import org.jnetpcap.nio.JBuffer;
  import org.jnetpcap.nio.JMemory;
  import org.jnetpcap.packet.JHeader;
  import org.jnetpcap.packet.JHeaderPool;
  import org.jnetpcap.packet.PcapPacket;
  import org.jnetpcap.protocol.lan.Ethernet;
  import org.jnetpcap.protocol.network.Ip4;
  import org.jnetpcap.protocol.network.Ip6;
  import org.jnetpcap.protocol.tcpip.Tcp;
  import org.jnetpcap.protocol.tcpip.Udp;
  import org.jnetpcap.protocol.vpn.L2TP;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class PacketReader {
  
  	private static final Logger logger = LoggerFactory.getLogger(PacketReader.class);
  	private IdGenerator  generator = new IdGenerator();
  	private Pcap pcapReader;
  	
  	private long firstPacket;
  	private long lastPacket;
  	
  	private Tcp  tcp;
  	private Udp  udp;
  	private Ip4  ipv4;
  	private Ip6  ipv6;
  	private L2TP l2tp;
  	private PcapHeader hdr;
  	private JBuffer buf;
  	
  	private boolean readIP6;
  	private boolean readIP4;
  	private String file;
  	
  	public PacketReader(String filename) {
  		super();	
  		this.readIP4 = true;
  		this.readIP6 = false;		
  		this.config(filename);
  	}
  	
  	public PacketReader(String filename, boolean readip4, boolean readip6) {
  		super();	
  		this.readIP4 = readip4;
  		this.readIP6 = readip6;
  		this.config(filename);
  	}	
  	
  	private void config(String filename){
          file = filename;
  		StringBuilder errbuf = new StringBuilder(); // For any error msgs
  		pcapReader = Pcap.openOffline(filename, errbuf);
  		
  		this.firstPacket = 0L;
  		this.lastPacket = 0L;
  
  		if (pcapReader == null) {
  			logger.error("Error while opening file for capture: "+errbuf.toString());
  			System.exit(-1);
  		}else{
  			this.tcp = new Tcp();
  			this.udp = new Udp();
  			this.ipv4 = new Ip4();
  			this.ipv6 = new Ip6();
  			this.l2tp = new L2TP();
  			hdr = new PcapHeader(JMemory.POINTER);
  			buf = new JBuffer(JMemory.POINTER);		
  		}		
  	}
  	
  	public BasicPacketInfo nextPacket(){
  		 PcapPacket      packet;
  		 BasicPacketInfo packetInfo = null;
  		 try{
  			 if(pcapReader.nextEx(hdr,buf) == Pcap.NEXT_EX_OK){
  				 packet = new PcapPacket(hdr, buf);
  				 packet.scan(Ethernet.ID);				 
  				 
  				 if(this.readIP4){					 
  					 packetInfo = getIpv4Info(packet);
  					 if (packetInfo == null && this.readIP6){
  					 	packetInfo = getIpv6Info(packet);				 	
  					 }					 
  				 }else if(this.readIP6){
  					 packetInfo = getIpv6Info(packet);
  					 if (packetInfo == null && this.readIP4){
  					 	packetInfo = getIpv4Info(packet);
  					 }
  				 }
  				 
  				 if (packetInfo == null){
  					 packetInfo = getVPNInfo(packet);
  				 }					 
  
  			 }else{
  				 throw new PcapClosedException();
  			 }
  		 }catch(PcapClosedException e){
  			 logger.debug("Read All packets on {}",file);
  			 throw e;
  		 }catch(Exception ex){
  			 logger.debug(ex.getMessage());
  		 }
  		 return packetInfo;
  	}
  	
  	private BasicPacketInfo getIpv4Info(PcapPacket packet){
  		BasicPacketInfo packetInfo = null;		
  		try {
  						
  			if (packet.hasHeader(ipv4)){
  				packetInfo = new BasicPacketInfo(this.generator);
  				packetInfo.setSrc(this.ipv4.source());
  				packetInfo.setDst(this.ipv4.destination());
  				//packetInfo.setTimeStamp(packet.getCaptureHeader().timestampInMillis());
  				packetInfo.setTimeStamp(packet.getCaptureHeader().timestampInMicros());
  				
  				if(this.firstPacket == 0L)
  					this.firstPacket = packet.getCaptureHeader().timestampInMillis();
  				this.lastPacket = packet.getCaptureHeader().timestampInMillis();
  
  				if(packet.hasHeader(this.tcp)){
  					packetInfo.setTCPWindow(tcp.window());
  					packetInfo.setSrcPort(tcp.source());
  					packetInfo.setDstPort(tcp.destination());
  					packetInfo.setProtocol(6);
  					packetInfo.setFlagFIN(tcp.flags_FIN());
  					packetInfo.setFlagPSH(tcp.flags_PSH());
  					packetInfo.setFlagURG(tcp.flags_URG());
  					packetInfo.setFlagSYN(tcp.flags_SYN());
  					packetInfo.setFlagACK(tcp.flags_ACK());
  					packetInfo.setFlagECE(tcp.flags_ECE());
  					packetInfo.setFlagCWR(tcp.flags_CWR());
  					packetInfo.setFlagRST(tcp.flags_RST());
  					packetInfo.setPayloadBytes(tcp.getPayloadLength());
  					packetInfo.setHeaderBytes(tcp.getHeaderLength());
  				}else if(packet.hasHeader(this.udp)){
  					packetInfo.setSrcPort(udp.source());
  					packetInfo.setDstPort(udp.destination());
  					packetInfo.setPayloadBytes(udp.getPayloadLength());
  					packetInfo.setHeaderBytes(udp.getHeaderLength());
  					packetInfo.setProtocol(17);			
  				}else {
  					/*logger.debug("other packet Ethernet -> {}"+  packet.hasHeader(new Ethernet()));
  					logger.debug("other packet Html     -> {}"+  packet.hasHeader(new Html()));
  					logger.debug("other packet Http     -> {}"+  packet.hasHeader(new Http()));
  					logger.debug("other packet SLL      -> {}"+  packet.hasHeader(new SLL()));
  					logger.debug("other packet L2TP     -> {}"+  packet.hasHeader(new L2TP()));
  					logger.debug("other packet Sctp     -> {}"+  packet.hasHeader(new Sctp()));
  					logger.debug("other packet PPP      -> {}"+  packet.hasHeader(new PPP()));*/
  
  					int headerCount = packet.getHeaderCount();
  					for(int i=0;i<headerCount;i++) {
  						JHeader header = JHeaderPool.getDefault().getHeader(i);
  						//JHeader hh = packet.getHeaderByIndex(i, header);
  						//logger.debug("getIpv4Info: {} --description: {} ",header.getName(),header.getDescription());
  					}
  				}
  			}
  		} catch (Exception e) {
  			//e.printStackTrace();
  			packet.scan(ipv4.getId());
  			String errormsg = "";
  			errormsg+=e.getMessage()+"\n";
  			//errormsg+=packet.getHeader(new Ip4())+"\n";
  			errormsg+="********************************************************************************"+"\n";
  			errormsg+=packet.toHexdump()+"\n";
  			
  			//System.out.println(errormsg);
  			logger.debug(errormsg);
  			//System.exit(-1);
  			return null;
  		}
  		
  		return packetInfo;
  	}
  	
  	private BasicPacketInfo getIpv6Info(PcapPacket packet){
  		BasicPacketInfo packetInfo = null;
  		try{
  			if(packet.hasHeader(ipv6)){
  				packetInfo = new BasicPacketInfo(this.generator);
  				packetInfo.setSrc(this.ipv6.source());
  				packetInfo.setDst(this.ipv6.destination());
  				packetInfo.setTimeStamp(packet.getCaptureHeader().timestampInMillis());			
  				
  				if(packet.hasHeader(this.tcp)){						
  					packetInfo.setSrcPort(tcp.source());
  					packetInfo.setDstPort(tcp.destination());
  					packetInfo.setPayloadBytes(tcp.getPayloadLength());
  					packetInfo.setHeaderBytes(tcp.getHeaderLength());
  					packetInfo.setProtocol(6);
  				}else if(packet.hasHeader(this.udp)){
  					packetInfo.setSrcPort(udp.source());
  					packetInfo.setDstPort(udp.destination());
  					packetInfo.setPayloadBytes(udp.getPayloadLength());
  					packetInfo.setHeaderBytes(tcp.getHeaderLength());
  					packetInfo.setProtocol(17);								
  				}		
  			}
  		}catch(Exception e){
  			logger.debug(e.getMessage());
  			packet.scan(ipv6.getId());
  			String errormsg = "";
  			errormsg+=e.getMessage()+"\n";
  			//errormsg+=packet.getHeader(new Ip6())+"\n";
  			errormsg+="********************************************************************************"+"\n";
  			errormsg+=packet.toHexdump()+"\n";
  			
  			//System.out.println(errormsg);
  			logger.debug(errormsg);
  			//System.exit(-1);
  			return null;			
  		}
  				
  		return packetInfo;
  	}
  	
  	private BasicPacketInfo getVPNInfo(PcapPacket packet){		
  		BasicPacketInfo packetInfo = null;		
  		try {
  			packet.scan(L2TP.ID);
  			
  			if (packet.hasHeader(l2tp)){				
  		    	if(this.readIP4){		
  		    		packet.scan(ipv4.getId());
  		    		packetInfo = getIpv4Info(packet);
  		    		if (packetInfo == null && this.readIP6){
  		    			packet.scan(ipv6.getId());
  		    			packetInfo = getIpv6Info(packet);				 	
  		    		}					 
  		    	}else if(this.readIP6){
  		    		packet.scan(ipv6.getId());
  		    		packetInfo = getIpv6Info(packet);
  		    		if (packetInfo == null && this.readIP4){
  		    			packet.scan(ipv4.getId());
  		    			packetInfo = getIpv4Info(packet);
  		    		}
  		    	}				
  
  			}
  		} catch (Exception e) {
  			logger.debug(e.getMessage());
  			packet.scan(l2tp.getId());
  			String errormsg = "";
  			errormsg+=e.getMessage()+"\n";
  			//errormsg+=packet.getHeader(new L2TP())+"\n";
  			errormsg+="********************************************************************************"+"\n";
  			errormsg+=packet.toHexdump()+"\n";
  			
  			//System.out.println(errormsg);
  			logger.debug(errormsg);
  			//System.exit(-1);
  			return null;
  		}
  		
  		return packetInfo;
  	}	
  
  	public long getFirstPacket() {
  		return firstPacket;
  	}
  
  	public void setFirstPacket(long firstPacket) {
  		this.firstPacket = firstPacket;
  	}
  
  	public long getLastPacket() {
  		return lastPacket;
  	}
  
  	public void setLastPacket(long lastPacket) {
  		this.lastPacket = lastPacket;
  	}	
  
  	/*
  	 * So far,The value of the field BasicPacketInfo.id is not used
  	 * It doesn't matter just using a static IdGenerator for realtime PcapPacket reading
  	 */
  	private static IdGenerator idGen = new IdGenerator();
  	public static BasicPacketInfo getBasicPacketInfo(PcapPacket packet,boolean readIP4, boolean readIP6) {
  		BasicPacketInfo packetInfo = null;
  		
  		
  		Protocol protocol = new Protocol();
  		
  		if(readIP4){					 
  			packetInfo = getIpv4Info(packet,protocol);
  			if (packetInfo == null && readIP6){
  				packetInfo = getIpv6Info(packet,protocol);				 	
  			}					 
  		}else if(readIP6){
  			packetInfo = getIpv6Info(packet,protocol);
  			if (packetInfo == null && readIP4){
  				packetInfo = getIpv4Info(packet,protocol);
  			}
  		}
  		
  		if (packetInfo == null){
  			packetInfo = getVPNInfo(packet,protocol,readIP4,readIP6);
  		}
  		
  		return packetInfo;
  	}
  
  	private static BasicPacketInfo getVPNInfo(PcapPacket packet,Protocol protocol,boolean readIP4, boolean readIP6) {		
  		BasicPacketInfo packetInfo = null;
  		try {
  			packet.scan(L2TP.ID);
  			
  			if (packet.hasHeader(protocol.getL2tp())){
  		    	if(readIP4){		
  		    		packet.scan(protocol.getIpv4().getId());
  		    		packetInfo = getIpv4Info(packet,protocol);
  		    		if (packetInfo == null && readIP6){
  		    			packet.scan(protocol.getIpv6().getId());
  		    			packetInfo = getIpv6Info(packet,protocol);				 	
  		    		}					 
  		    	}else if(readIP6){
  		    		packet.scan(protocol.getIpv6().getId());
  		    		packetInfo = getIpv6Info(packet,protocol);
  		    		if (packetInfo == null && readIP4){
  		    			packet.scan(protocol.getIpv4().getId());
  		    			packetInfo = getIpv4Info(packet,protocol);
  		    		}
  		    	}				
  
  			}
  		} catch (Exception e) {
  			/*
  			 * BufferUnderflowException while decoding header
  			 * havn't fixed, so do not e.printStackTrace() 
  			 */
  			//e.printStackTrace();
  			/*packet.scan(protocol.l2tp.getId());
  			String errormsg = "";
  			errormsg+=e.getMessage()+"\n";
  			//errormsg+=packet.getHeader(new L2TP())+"\n";
  			errormsg+="********************************************************************************"+"\n";
  			errormsg+=packet.toHexdump()+"\n";
  			logger.error(errormsg);*/
  			return null;
  		}
  		
  		return packetInfo;
  	}
  
  	private static BasicPacketInfo getIpv6Info(PcapPacket packet,Protocol protocol) {
  		BasicPacketInfo packetInfo = null;
  		try{
  			if(packet.hasHeader(protocol.getIpv6())){
  				packetInfo = new BasicPacketInfo(idGen);
  				packetInfo.setSrc(protocol.getIpv6().source());
  				packetInfo.setDst(protocol.getIpv6().destination());
  				packetInfo.setTimeStamp(packet.getCaptureHeader().timestampInMillis());			
  				
  				if(packet.hasHeader(protocol.getTcp())){
  					packetInfo.setSrcPort(protocol.getTcp().source());
  					packetInfo.setDstPort(protocol.getTcp().destination());
  					packetInfo.setPayloadBytes(protocol.getTcp().getPayloadLength());
  					packetInfo.setHeaderBytes(protocol.getTcp().getHeaderLength());
  					packetInfo.setProtocol(6);
  				}else if(packet.hasHeader(protocol.getUdp())){
  					packetInfo.setSrcPort(protocol.getUdp().source());
  					packetInfo.setDstPort(protocol.getUdp().destination());
  					packetInfo.setPayloadBytes(protocol.getUdp().getPayloadLength());
  					packetInfo.setHeaderBytes(protocol.getUdp().getHeaderLength());
  					packetInfo.setProtocol(17);								
  				}		
  			}
  		}catch(Exception e){
  			/*
  			 * BufferUnderflowException while decoding header
  			 * havn't fixed, so do not e.printStackTrace()
  			 */
  			//e.printStackTrace();
  			/*packet.scan(protocol.ipv6.getId());
  			String errormsg = "";
  			errormsg+=e.getMessage()+"\n";
  			//errormsg+=packet.getHeader(new Ip6())+"\n";
  			errormsg+="********************************************************************************"+"\n";
  			errormsg+=packet.toHexdump()+"\n";
  			logger.error(errormsg);
  			//System.exit(-1);*/
  			return null;			
  		}
  				
  		return packetInfo;
  	}
  
  	private static BasicPacketInfo getIpv4Info(PcapPacket packet,Protocol protocol) {
  		BasicPacketInfo packetInfo = null;		
  		try {
  						
  			if (packet.hasHeader(protocol.getIpv4())){
  				packetInfo = new BasicPacketInfo(idGen);
  				packetInfo.setSrc(protocol.getIpv4().source());
  				packetInfo.setDst(protocol.getIpv4().destination());
  				//packetInfo.setTimeStamp(packet.getCaptureHeader().timestampInMillis());
  				packetInfo.setTimeStamp(packet.getCaptureHeader().timestampInMicros());
  				
  				/*if(this.firstPacket == 0L)
  					this.firstPacket = packet.getCaptureHeader().timestampInMillis();
  				this.lastPacket = packet.getCaptureHeader().timestampInMillis();*/
  
  				if(packet.hasHeader(protocol.getTcp())){
  					packetInfo.setTCPWindow(protocol.getTcp().window());
  					packetInfo.setSrcPort(protocol.getTcp().source());
  					packetInfo.setDstPort(protocol.getTcp().destination());
  					packetInfo.setProtocol(6);
  					packetInfo.setFlagFIN(protocol.getTcp().flags_FIN());
  					packetInfo.setFlagPSH(protocol.getTcp().flags_PSH());
  					packetInfo.setFlagURG(protocol.getTcp().flags_URG());
  					packetInfo.setFlagSYN(protocol.getTcp().flags_SYN());
  					packetInfo.setFlagACK(protocol.getTcp().flags_ACK());
  					packetInfo.setFlagECE(protocol.getTcp().flags_ECE());
  					packetInfo.setFlagCWR(protocol.getTcp().flags_CWR());
  					packetInfo.setFlagRST(protocol.getTcp().flags_RST());
  					packetInfo.setPayloadBytes(protocol.getTcp().getPayloadLength());
  					packetInfo.setHeaderBytes(protocol.getTcp().getHeaderLength());
  				}else if(packet.hasHeader(protocol.getUdp())){
  					packetInfo.setSrcPort(protocol.getUdp().source());
  					packetInfo.setDstPort(protocol.getUdp().destination());
  					packetInfo.setPayloadBytes(protocol.getUdp().getPayloadLength());
  					packetInfo.setHeaderBytes(protocol.getUdp().getHeaderLength());
  					packetInfo.setProtocol(17);			
  				} else {
  					int headerCount = packet.getHeaderCount();
  					for(int i=0;i<headerCount;i++) {
  						JHeader header = JHeaderPool.getDefault().getHeader(i);
  						//JHeader hh = packet.getHeaderByIndex(i, header);
  						//logger.debug("getIpv4Info: {} --description: {} ",header.getName(),header.getDescription());
  					}
  				}
  			}
  		} catch (Exception e) {
  			/*
  			 * BufferUnderflowException while decoding header
  			 * havn't fixed, so do not e.printStackTrace()
  			 */
  			//e.printStackTrace();
  			/*packet.scan(protocol.ipv4.getId());
  			String errormsg = "";
  			errormsg+=e.getMessage()+"\n";
  			//errormsg+=packet.getHeader(new Ip4())+"\n";
  			errormsg+="********************************************************************************"+"\n";
  			errormsg+=packet.toHexdump()+"\n";
  			logger.error(errormsg);
  			return null;*/
  		}
  		
  		return packetInfo;
  	}
  }
  