Code/Projects/SmartPlugDetector/src/main/java/edu/uci/iotproject/detection/Layer2SequenceMatcher.java

   1 package edu.uci.iotproject.detection;
   2
   3 import edu.uci.iotproject.analysis.TriggerTrafficExtractor;
   4 import org.pcap4j.core.PcapPacket;
   5
   6 import java.util.ArrayList;
   7 import java.util.List;
   8
   9 /**
  10  * TODO add class documentation.
  11  *
  12  * @author Janus Varmarken
  13  */
  14 public class Layer2SequenceMatcher {
  15
  16     /**
  17      * The sequence this {@link Layer2SequenceMatcher} is searching for.
  18      */
  19     private final List<PcapPacket> mSequence;
  20
  21     /**
  22      * Buffer of actual packets seen so far that match the searched sequence (i.e., constitutes a subsequence of the
  23      * searched sequence).
  24      */
  25     private final List<PcapPacket> mMatchedPackets = new ArrayList<>();
  26
  27     public Layer2SequenceMatcher(List<PcapPacket> sequence) {
  28         mSequence = sequence;
  29     }
  30
  31     public boolean matchPacket(PcapPacket packet) {
  32         // The packet we want to match next.
  33         PcapPacket expected = mSequence.get(mMatchedPackets.size());
  34         // First verify if the received packet has the length we're looking for.
  35         if (packet.getOriginalLength() == expected.getOriginalLength()) {
  36             // Next apply timing constraints:
  37             // - to be a match, the packet must have a later timestamp than any other packet currently matched
  38             // - does adding the packet cause the max allowed time between first packet and last packet to be exceeded?
  39             if (mMatchedPackets.size() > 0 &&
  40                     !packet.getTimestamp().isAfter(mMatchedPackets.get(mMatchedPackets.size()-1).getTimestamp())) {
  41                 return false;
  42             }
  43             if (mMatchedPackets.size() > 0 &&
  44                     packet.getTimestamp().
  45                             isAfter(mMatchedPackets.get(0).getTimestamp().
  46                                     plusMillis(TriggerTrafficExtractor.INCLUSION_WINDOW_MILLIS))) {
  47                 // Packet too
  48                 return false;
  49             }
  50             // TODO (how to) check directions?
  51             // This packet has a length matching next packet of searched sequence, so we store it and advance.
  52             mMatchedPackets.add(packet);
  53             if (mMatchedPackets.size() == mSequence.size()) {
  54                 // TODO report (to observers?) that we are done.
  55             }
  56             return true;
  57         }
  58         return false;
  59     }
  60
  61     public int getMatchedPacketsCount() {
  62         return mMatchedPackets.size();
  63     }
  64
  65     public int getTargetSequencePacketCount() {
  66         return mSequence.size();
  67     }
  68
  69     public List<PcapPacket> getTargetSequence() {
  70         return mSequence;
  71     }
  72
  73     public List<PcapPacket> getMatchedPackets() {
  74         return mMatchedPackets;
  75     }
  76 }