packetCapturer

Class Capturer

java.lang.Object

packetCapturer.Capturer

All Implemented Interfaces:

java.lang.Runnable

public class Capturer
extends java.lang.Object
implements java.lang.Runnable

The class Capturer captures all the packets from a given network interface. These packets are then queued up for the FlowGenerator. A filter removes local subnet traffic based on the subnet address.

It is intended to run in its own thread.
The library used to capture packets from the network is jNetPcap: http://jnetpcap.com.
Both version 1.3 and 1.4 contains some bugs, which were fixed in trunk. Therefore I used Linux and Windows native binaries from the version 1.4, and the Java code from SVN trunk. It will be better to compile native libraries from trunk as well, but I did not have time to do this.
Link to the trunk repository: http://jnetpcap.svn.sourceforge.net/viewvc/jnetpcap/jnetpcap/trunk/src//a>.

Author:

Tomasz Bujlow (tbu@es.aau.dk)

Field Summary

Fields

Modifier and Type	Field and Description
private java.lang.Thread	capturerThread Thread used by the class.
private org.jnetpcap.PcapIf	device Network interface on which we run the capture.
private java.util.ArrayList<byte[]>	IPAddresses List of IP addresses assigned to the interface used for capture.
private boolean	isStarted Used to dermine if the thread is already started.
private static org.apache.log4j.Logger	log Used to log different events.
private CapturedPacketsQueue	myPacketQueue Queue of captured packets.
private org.jnetpcap.Pcap	pcap Logical capturing device.
private boolean	stateOK Used to dermine if the capturer crashed.

Constructor Summary

Constructors

Constructor and Description
Capturer(org.jnetpcap.PcapIf device, CapturedPacketsQueue myPacketQueue) Constructs the class.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.String	getChosenInterface() Gets string identifier of the chosen interface.
boolean	isAlive() Checks if Capturer is alive.
private boolean	isLocalIP(byte[] source) Checks if the provided IP address is assigned to the local network interface.
boolean	isOK() Tells if the capturer is operating properly.
void	run() Runs the thread.
void	start() Starts the thread.
void	stop() Stops the thread.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

log

private static org.apache.log4j.Logger log

Used to log different events.

capturerThread

private java.lang.Thread capturerThread

Thread used by the class.

device

private org.jnetpcap.PcapIf device

Network interface on which we run the capture.

pcap

private org.jnetpcap.Pcap pcap

Logical capturing device.

IPAddresses

private java.util.ArrayList<byte[]> IPAddresses

List of IP addresses assigned to the interface used for capture.

myPacketQueue

private CapturedPacketsQueue myPacketQueue

Queue of captured packets.

isStarted

private boolean isStarted

Used to dermine if the thread is already started.

stateOK

private boolean stateOK

Used to dermine if the capturer crashed. If yes, the VBS client needs to be restarted.

Constructor Detail

Capturer

public Capturer(org.jnetpcap.PcapIf device,
        CapturedPacketsQueue myPacketQueue)

Constructs the class.

Parameters:

device - network interface on which we run the capture

myPacketQueue - queue of captured packets

Method Detail

start

public void start()

Starts the thread.

stop

public void stop()

Stops the thread. Breakloop breaks the capturing loop after the next packet is captured from the interface. If the interface is down, no new packets can be captured. It is why we have the second method to force the thread to close.

isAlive

public boolean isAlive()

Checks if Capturer is alive. It means that:
- the thread must exists
- the thread must be fully started and running (isStarted equals true). This condition is used to check if the thread is fully started or if it needs more time to start.

Returns:

true if the thread is fully started and operational, false otherwise

run

public void run()

Runs the thread. Captures all the packets from the interface except packets belonging to the local subnet. Sometimes the external capturing process can fail. Then the stateOK flag is set to false, what causes the VBS client to restart. Such situation can take place after the computer is suspended or hibernated.

Specified by:

run in interface java.lang.Runnable

isOK

public boolean isOK()

Tells if the capturer is operating properly.

Returns:

true if the capturer is operating properly, false if it crashed

getChosenInterface

public java.lang.String getChosenInterface()

Gets string identifier of the chosen interface.

Returns:

string identifier of the chosen interface

isLocalIP

private boolean isLocalIP(byte[] source)

Checks if the provided IP address is assigned to the local network interface.

Parameters:

source - the IP address to be checked

Returns:

true if this is a local IP address, false otherwise