OpenSocEthernetDecoder.java

package com.opensoc.pcap;

import java.util.BitSet;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArraySet;

import org.krakenapps.pcap.decoder.ethernet.EthernetDecoder;
import org.krakenapps.pcap.decoder.ethernet.EthernetFrame;
import org.krakenapps.pcap.decoder.ethernet.EthernetProcessor;
import org.krakenapps.pcap.decoder.ethernet.MacAddress;
import org.krakenapps.pcap.packet.PcapPacket;
import org.krakenapps.pcap.util.Buffer;

public class OpenSocEthernetDecoder extends EthernetDecoder {

  private Set<EthernetProcessor> callbacks;
  private Map<Integer, Set<EthernetProcessor>> typeCallbacks;

  public OpenSocEthernetDecoder() {
    callbacks = new CopyOnWriteArraySet<EthernetProcessor>();
    typeCallbacks = new ConcurrentHashMap<Integer, Set<EthernetProcessor>>();
  }

  public void register(EthernetProcessor processor) {
    this.callbacks.add(processor);
  }

  public void register(int type, EthernetProcessor processor) {
    Set<EthernetProcessor> processors = typeCallbacks.get(type);
    if (processors == null) {
      processors = new HashSet<EthernetProcessor>();
      typeCallbacks.put(type, processors);
    }

    processors.add(processor);
  }

  public void unregister(EthernetProcessor processor) {
    this.callbacks.remove(processor);
  }

  public void unregister(int type, EthernetProcessor processor) {
    Set<EthernetProcessor> processors = typeCallbacks.get(type);
    if (processors == null)
      return;

    processors.remove(processor);
  }

  public void decode(PcapPacket packet) {
    // do not reorder following codes (parse sequence)
    MacAddress destination = getMacAddress(packet.getPacketData());
    MacAddress source = getMacAddress(packet.getPacketData());
    int type = getEtherType(packet.getPacketData());

    if (type == 0x8100) {
      // It is 802.1Q VLAN tag
      IEEE_802_1Q iee802_1qTag = get802_1qTag(packet.getPacketData());
      // Now get the type
      type = getEtherType(packet.getPacketData());
    }

    Buffer buffer = packet.getPacketData();
    buffer.discardReadBytes();

    EthernetFrame frame = new EthernetFrame(source, destination, type, buffer);
    frame.setPcapPacket(packet);
    dispatch(frame);
  }

  private MacAddress getMacAddress(Buffer data) {
    byte[] mac = new byte[6];
    data.gets(mac, 0, 6);
    return new MacAddress(mac);
  }

  private int getEtherType(Buffer data) {
    return ((int) data.getShort()) & 0x0000FFFF;
  }

  private IEEE_802_1Q get802_1qTag(Buffer data) {

    // reference http://en.wikipedia.org/wiki/EtherType &
    // http://en.wikipedia.org/wiki/IEEE_802.1Q
    byte[] b802_1qTag = new byte[2];
    data.gets(b802_1qTag, 0, 2);
    BitSet bits = BitSet.valueOf(b802_1qTag);
    int pcp = convertBitToInt(bits.get(0, 3));
    int dei = convertBitToInt(bits.get(3, 4));
    int vid = convertBitToInt(bits.get(4, 16));

    return new IEEE_802_1Q(pcp, dei, vid);
  }

  public static int convertBitToInt(BitSet bits) {
    int value = 0;
    for (int i = 0; i < bits.length(); ++i) {
      value += bits.get(i) ? (1 << i) : 0;
    }
    return value;
  }

  private void dispatch(EthernetFrame frame) {
    for (EthernetProcessor processor : callbacks)
      processor.process(frame);

    Set<EthernetProcessor> processors = typeCallbacks.get(frame.getType());
    if (processors == null)
      return;

    for (EthernetProcessor processor : processors)
      processor.process(frame.dup());
  }
}