public class ip extends packet {
        
        final int offset_type[] =               // Anfagsoffset des Datagramms
                {4,14,-1,-1,-1,-1,22,-1,16,4,21,8,0,24,24};

	int dlt = 0;                            // Datalink-Type
	int payloadOffset;                      // Payload-Zeiger

	int version = 0;	                // Headerversion
	int headerLength = 0;		        // Headerlänge in Byte
	int tos = 0;                            // Type of Service
	int length = 0;			        // gesamte Paketlänge in Byte
	int id = 0;                             // Paketnummer
        boolean dontFragment = false;           // Fragmentierungsflags
        boolean moreFragments = false;
	int fragmentOffset = 0;                 // Offset des Paketfragments
	int ttl = 0;			        // Time to Live
	int protocol = 0;		        // Protokoll des Payloads
	int checksum = 0;                       // Header-Checksumme

        int source1 = 0;                        // Quelladresse
        int source2 = 0;
        int source3 = 0;
        int source4 = 0;
        int dest1 = 0;                          // Zieladresse
        int dest2 = 0;
        int dest3 = 0;
        int dest4 = 0;
	

	public ip(byte b[],int dataLinkType) {
		
		int position = offset_type[dataLinkType];
		dlt = dataLinkType;

		// Parsing entsprechend RFC 791, siehe [3]

		version = ( getByte(position,b) & 0xF0 ) >> 4;
		headerLength = ( getByte(position,b) & 0x0F ) * 4;
		payloadOffset = position + headerLength;
		tos = getByte(++position,b);
		length = getWord(++position,b);
			
		position+=2;	
		id = getWord(position,b);
		
		position+=2;	
	       	dontFragment = (getByte(position,b) & 0x40) == 0x40 ? true : false;
	       	moreFragments = (getByte(position,b) & 0x20) == 0x20 ? true : false;
	       	fragmentOffset = getWord(position,b) & 0x1FFF;
	
		position+=2;	
		ttl = getByte(position,b);
		protocol = getByte(++position,b);
		checksum = getWord(++position,b);
		
		position+=2;	
		source1 = getByte(position,b);
		source2 = getByte(++position,b);
		source3 = getByte(++position,b);
		source4 = getByte(++position,b);

		dest1 = getByte(++position,b);
		dest2 = getByte(++position,b);
		dest3 = getByte(++position,b);
		dest4 = getByte(++position,b);
        }

        public String headerString() {
                String packetString = new String("Version: "+version+"\nHeader Length: "+headerLength);
                packetString += "\nDatagram Length: "+length+"\nDatagram ID: "+id;
                packetString += "\nDontFragment: "+dontFragment+"\nMoreFragments: "+moreFragments;
                packetString += "\nFragmentOffset: "+fragmentOffset+"\nTime to Live: "+ttl;
                packetString += "\nProtocol: "+protocol;
                packetString += "\nSource: "+source1+"."+source2+"."+source3+"."+source4;
                packetString += "\nDestination: "+dest1+"."+dest2+"."+dest3+"."+dest4;
		return packetString;
        }

        public int getPayloadOffset() {
                return payloadOffset;
        }

        public int getLength() {
                return length;
        }
}