private final int mServerPort;
/**
- * The list of packets pertaining to this conversation.
+ * The list of packets (with payload) pertaining to this conversation.
*/
private final List<PcapPacket> mPackets;
/**
- * Contains the sequence numbers seen so far for this {@code Conversation}.
+ * Contains the sequence numbers used thus far by the host that is considered the <em>client</em> in this
+ * {@code Conversation}.
* Used for filtering out retransmissions.
*/
- private final Set<Integer> mSeqNumbers;
+ private final Set<Integer> mSeqNumbersClient;
+
+ /**
+ * Contains the sequence numbers used thus far by the host that is considered the <em>server</em> in this
+ * {@code Conversation}.
+ * Used for filtering out retransmissions.
+ */
+ private final Set<Integer> mSeqNumbersSrv;
+
+ /**
+ * List of SYN packets pertaining to this conversation.
+ */
+ private List<PcapPacket> mSynPackets;
/**
* List of pairs FINs and their corresponding ACKs associated with this conversation.
private List<FinAckPair> mFinPackets;
/* End instance properties */
+ /**
+ * Factory method for creating a {@code Conversation} from a {@link PcapPacket}.
+ * @param pcapPacket The {@code PcapPacket} that wraps a TCP segment for which a {@code Conversation} is to be initiated.
+ * @param clientIsSrc If {@code true}, the source address and source port found in the IP datagram and TCP segment
+ * wrapped in the {@code PcapPacket} are regarded as pertaining to the client, and the destination
+ * address and destination port are regarded as pertaining to the server---and vice versa if set
+ * to {@code false}.
+ * @return A {@code Conversation} initiated with ip:port for client and server according to the direction of the packet.
+ */
+ public static Conversation fromPcapPacket(PcapPacket pcapPacket, boolean clientIsSrc) {
+ IpV4Packet ipPacket = pcapPacket.get(IpV4Packet.class);
+ TcpPacket tcpPacket = pcapPacket.get(TcpPacket.class);
+ String clientIp = clientIsSrc ? ipPacket.getHeader().getSrcAddr().getHostAddress() :
+ ipPacket.getHeader().getDstAddr().getHostAddress();
+ String srvIp = clientIsSrc ? ipPacket.getHeader().getDstAddr().getHostAddress() :
+ ipPacket.getHeader().getSrcAddr().getHostAddress();
+ int clientPort = clientIsSrc ? tcpPacket.getHeader().getSrcPort().valueAsInt() :
+ tcpPacket.getHeader().getDstPort().valueAsInt();
+ int srvPort = clientIsSrc ? tcpPacket.getHeader().getDstPort().valueAsInt() :
+ tcpPacket.getHeader().getSrcPort().valueAsInt();
+ return new Conversation(clientIp, clientPort, srvIp, srvPort);
+ }
+
/**
* Constructs a new {@code Conversation}.
* @param clientIp The IP of the host that is considered the client (i.e. the host that initiates the conversation)
this.mServerIp = serverIp;
this.mServerPort = serverPort;
this.mPackets = new ArrayList<>();
- this.mSeqNumbers = new HashSet<>();
+ this.mSeqNumbersClient = new HashSet<>();
+ this.mSeqNumbersSrv = new HashSet<>();
+ this.mSynPackets = new ArrayList<>();
this.mFinPackets = new ArrayList<>();
}
public void addPacket(PcapPacket packet, boolean ignoreRetransmissions) {
// Precondition: verify that packet does indeed pertain to conversation.
onAddPrecondition(packet);
- // For now we only support TCP flows.
- TcpPacket tcpPacket = Objects.requireNonNull(packet.get(TcpPacket.class));
- int seqNo = tcpPacket.getHeader().getSequenceNumber();
- if (ignoreRetransmissions && mSeqNumbers.contains(seqNo)) {
+ if (ignoreRetransmissions && isRetransmission(packet)) {
// Packet is a retransmission. Ignore it.
return;
}
- // Update set of sequence numbers seen so far with sequence number of new packet.
- mSeqNumbers.add(seqNo);
+ // Select direction-dependent set of sequence numbers seen so far and update it with sequence number of new packet.
+ addSeqNumber(packet);
// Finally add packet to list of packets pertaining to this conversation.
mPackets.add(packet);
+ // Preserve order of packets in list: sort according to timestamp.
+ if (mPackets.size() > 1 &&
+ mPackets.get(mPackets.size()-1).getTimestamp().isBefore(mPackets.get(mPackets.size()-2).getTimestamp())) {
+ Collections.sort(mPackets, (o1, o2) -> {
+ if (o1.getTimestamp().isBefore(o2.getTimestamp())) { return -1; }
+ else if (o2.getTimestamp().isBefore(o1.getTimestamp())) { return 1; }
+ else { return 0; }
+ });
+ }
}
/**
return Collections.unmodifiableList(mPackets);
}
+ /**
+ * Records a TCP SYN packet as pertaining to this conversation (adds it to the the internal list).
+ * Attempts to add duplicate SYN packets will be ignored, and the caller is made aware of the attempt to add a
+ * duplicate by the return value being {@code false}.
+ *
+ * @param synPacket A {@link PcapPacket} wrapping a TCP SYN packet.
+ * @return {@code true} if the packet was successfully added to this {@code Conversation}, {@code false} otherwise.
+ */
+ public boolean addSynPacket(PcapPacket synPacket) {
+ onAddPrecondition(synPacket);
+ final IpV4Packet synPacketIpSection = synPacket.get(IpV4Packet.class);
+ final TcpPacket synPacketTcpSection = synPacket.get(TcpPacket.class);
+ if (synPacketTcpSection == null || !synPacketTcpSection.getHeader().getSyn()) {
+ throw new IllegalArgumentException("Not a SYN packet.");
+ }
+ // We are only interested in recording one copy of the two SYN packets (one SYN packet in each direction), i.e.,
+ // we want to discard retransmitted SYN packets.
+ if (mSynPackets.size() >= 2) {
+ return false;
+ }
+ // Check the set of recorded SYN packets to see if we have already recorded a SYN packet going in the same
+ // direction as the packet given in the argument.
+ boolean matchingPrevSyn = mSynPackets.stream().anyMatch(p -> {
+ IpV4Packet pIp = p.get(IpV4Packet.class);
+ TcpPacket pTcp = p.get(TcpPacket.class);
+ boolean srcAddrMatch = synPacketIpSection.getHeader().getSrcAddr().getHostAddress().
+ equals(pIp.getHeader().getSrcAddr().getHostAddress());
+ boolean dstAddrMatch = synPacketIpSection.getHeader().getDstAddr().getHostAddress().
+ equals(pIp.getHeader().getDstAddr().getHostAddress());
+ boolean srcPortMatch = synPacketTcpSection.getHeader().getSrcPort().valueAsInt() ==
+ pTcp.getHeader().getSrcPort().valueAsInt();
+ boolean dstPortMatch = synPacketTcpSection.getHeader().getDstPort().valueAsInt() ==
+ pTcp.getHeader().getDstPort().valueAsInt();
+ return srcAddrMatch && dstAddrMatch && srcPortMatch && dstPortMatch;
+ });
+ if (matchingPrevSyn) {
+ return false;
+ }
+ // Update direction-dependent set of sequence numbers and record/log packet.
+ addSeqNumber(synPacket);
+ return mSynPackets.add(synPacket);
+
+ /*
+ mSynPackets.stream().anyMatch(p -> {
+ IpV4Packet pIp = p.get(IpV4Packet.class);
+ TcpPacket pTcp = p.get(TcpPacket.class);
+ boolean srcAddrMatch = synPacketIpSection.getHeader().getSrcAddr().getHostAddress().
+ equals(pIp.getHeader().getSrcAddr().getHostAddress());
+ boolean dstAddrMatch = synPacketIpSection.getHeader().getDstAddr().getHostAddress().
+ equals(pIp.getHeader().getDstAddr().getHostAddress());
+ boolean srcPortMatch = synPacketTcpSection.getHeader().getSrcPort().valueAsInt() ==
+ pTcp.getHeader().getSrcPort().valueAsInt();
+ boolean dstPortMatch = synPacketTcpSection.getHeader().getDstPort().value() ==
+ pTcp.getHeader().getDstPort().value();
+
+ boolean fourTupleMatch = srcAddrMatch && dstAddrMatch && srcPortMatch && dstPortMatch;
+
+ boolean seqNoMatch = synPacketTcpSection.getHeader().getSequenceNumber() ==
+ pTcp.getHeader().getSequenceNumber();
+
+ if (fourTupleMatch && !seqNoMatch) {
+ // If the four tuple that identifies the conversation matches, but the sequence number is different,
+ // it means that this SYN packet is, in fact, an attempt to establish a **new** connection, and hence
+ // the given packet is NOT part of this conversation, even though the ip:port combinations are (by
+ // chance) selected such that they match this conversation.
+ throw new IllegalArgumentException("Attempt to add SYN packet that belongs to a different conversation " +
+ "(which is identified by the same four tuple as this conversation)");
+ }
+ return fourTupleMatch && seqNoMatch;
+ });
+ */
+ }
+
+ /**
+ * Get a list of SYN packets pertaining to this {@code Conversation}.
+ * The returned list is a read-only list.
+ * @return the list of SYN packets pertaining to this {@code Conversation}.
+ */
+ public List<PcapPacket> getSynPackets() {
+ return Collections.unmodifiableList(mSynPackets);
+ }
+
/**
* Adds a TCP FIN packet to the list of TCP FIN packets associated with this conversation.
* @param finPacket The TCP FIN packet that is to be added to (associated with) this conversation.
public void addFinPacket(PcapPacket finPacket) {
// Precondition: verify that packet does indeed pertain to conversation.
onAddPrecondition(finPacket);
+ // TODO: should call addSeqNumber here?
+ addSeqNumber(finPacket);
mFinPackets.add(new FinAckPair(finPacket));
}
// Precondition: verify that the packet pertains to this conversation.
onAddPrecondition(ackPacket);
// Mark unack'ed FIN(s) that this ACK matches as ACK'ed (there might be more than one in case of retransmissions..?)
- mFinPackets.replaceAll(finAckPair -> (!finAckPair.isAcknowledged() && finAckPair.isCorrespondingAckPacket(ackPacket)) ? new FinAckPair(finAckPair.getFinPacket(), ackPacket) : finAckPair);
+ mFinPackets.replaceAll(finAckPair -> !finAckPair.isAcknowledged() && finAckPair.isCorrespondingAckPacket(ackPacket) ? new FinAckPair(finAckPair.getFinPacket(), ackPacket) : finAckPair);
+ }
+
+ /**
+ * Retrieves an unmodifiable view of the list of {@link FinAckPair}s associated with this {@code Conversation}.
+ * @return an unmodifiable view of the list of {@link FinAckPair}s associated with this {@code Conversation}.
+ */
+ public List<FinAckPair> getFinAckPairs() {
+ return Collections.unmodifiableList(mFinPackets);
}
/**
}
}
+ /**
+ * <p>
+ * Determines if the TCP packet contained in {@code packet} is a retransmission of a previously seen (logged)
+ * packet.
+ * </p>
+ *
+ * <b>
+ * TODO:
+ * the current implementation, which uses a set of previously seen sequence numbers, will consider a segment
+ * with a reused sequence number---occurring as a result of sequence number wrap around for a very long-lived
+ * connection---as a retransmission (and may therefore end up discarding it even though it is in fact NOT a
+ * retransmission). Ideas?
+ * </b>
+ *
+ * @param packet The packet.
+ * @return {@code true} if {@code packet} was determined to be a retransmission, {@code false} otherwise.
+ */
+ public boolean isRetransmission(PcapPacket packet) {
+ // Extract sequence number.
+ int seqNo = packet.get(TcpPacket.class).getHeader().getSequenceNumber();
+ switch (getDirection(packet)) {
+ case CLIENT_TO_SERVER:
+ return mSeqNumbersClient.contains(seqNo);
+ case SERVER_TO_CLIENT:
+ return mSeqNumbersSrv.contains(seqNo);
+ default:
+ throw new RuntimeException(String.format("Unexpected value of enum '%s'",
+ Direction.class.getSimpleName()));
+ }
+ }
+
+ /**
+ * Extracts the TCP sequence number from {@code packet} and adds it to the proper set of sequence numbers by
+ * analyzing the direction of the packet.
+ * @param packet A TCP packet (wrapped in a {@code PcapPacket}) that was added to this conversation and whose
+ * sequence number is to be recorded as seen.
+ */
+ private void addSeqNumber(PcapPacket packet) {
+ // Note: below check is redundant if client code is correct as the call to check the precondition should already
+ // have been made by the addXPacket method that invokes this method. As such, the call below may be removed in
+ // favor of speed, but the improvement will be minor, hence the added safety may be worth it.
+ onAddPrecondition(packet);
+ // Extract sequence number.
+ int seqNo = packet.get(TcpPacket.class).getHeader().getSequenceNumber();
+ // Determine direction of packet and add packet's sequence number to corresponding set of sequence numbers.
+ switch (getDirection(packet)) {
+ case CLIENT_TO_SERVER:
+ // Client to server packet.
+ mSeqNumbersClient.add(seqNo);
+ break;
+ case SERVER_TO_CLIENT:
+ // Server to client packet.
+ mSeqNumbersSrv.add(seqNo);
+ break;
+ default:
+ throw new RuntimeException(String.format("Unexpected value of enum '%s'",
+ Direction.class.getSimpleName()));
+ }
+ }
+
+ /**
+ * Determine the direction of {@code packet}.
+ * @param packet The packet whose direction is to be determined.
+ * @return A {@link Direction} indicating the direction of the packet.
+ */
+ private Direction getDirection(PcapPacket packet) {
+ IpV4Packet ipPacket = packet.get(IpV4Packet.class);
+ String ipSrc = ipPacket.getHeader().getSrcAddr().getHostAddress();
+ String ipDst = ipPacket.getHeader().getDstAddr().getHostAddress();
+ // Determine direction of packet.
+ if (ipSrc.equals(mClientIp) && ipDst.equals(mServerIp)) {
+ // Client to server packet.
+ return Direction.CLIENT_TO_SERVER;
+ } else if (ipSrc.equals(mServerIp) && ipDst.equals(mClientIp)) {
+ // Server to client packet.
+ return Direction.SERVER_TO_CLIENT;
+ } else {
+ throw new IllegalArgumentException("getDirection: packet not related to " + getClass().getSimpleName());
+ }
+ }
+
+ /**
+ * Utility enum for expressing the direction of a packet pertaining to this {@code Conversation}.
+ */
+ private enum Direction {
+ CLIENT_TO_SERVER, SERVER_TO_CLIENT
+ }
+
}
\ No newline at end of file
projects / pingpong.git / blobdiff