org.savarese.vserv.tcpip
Class IPPacket

java.lang.Object
  org.savarese.vserv.tcpip.IPPacket

Direct Known Subclasses:

ICMPPacket, TCPPacket, UDPPacket

public class IPPacket
extends java.lang.Object

IPPacket wraps the raw bytes comprising an IPv4 packet and exposes its content via setter and getter methods. After you alter the header of an IP packet you have to recompute the checksum with computeIPChecksum(). The structure of IP packets is described in RFC 760.

Author:

Daniel F. Savarese

Field Summary

protected byte[]	_data_ Raw packet data.
static int	LENGTH_DESTINATION_ADDRESS Number of bytes in destination address.
static int	LENGTH_SOURCE_ADDRESS Number of bytes in source address.
static int	OFFSET_DESTINATION_ADDRESS Offset into byte array of destination address header value.
static int	OFFSET_IP_CHECKSUM Offset into byte array of header checksum header value.
static int	OFFSET_PROTOCOL Offset into byte array of protocol number header value.
static int	OFFSET_SOURCE_ADDRESS Offset into byte array of source address header value.
static int	OFFSET_TOTAL_LENGTH Offset into byte array of total packet length header value.
static int	OFFSET_TTL Offset into byte array of time to live header value.
static int	PROTOCOL_ICMP Protocol constant for ICMP.
static int	PROTOCOL_IP Protocol constant for IPv4.
static int	PROTOCOL_TCP Protocol constant for TCP.
static int	PROTOCOL_UDP Protocol constant for UDP.

Constructor Summary

IPPacket(int size)
Creates a new IPPacket of a given size.

Method Summary

int	computeIPChecksum() Same as computeIPChecksum(true);
int	computeIPChecksum(boolean update) Computes the IP checksum, optionally updating the IP checksum header.
void	copy(IPPacket packet) Copies the contents of an IPPacket to the calling instance.
void	getData(byte[] data) Copies the raw packet data into a byte array.
void	getDestination(byte[] address) Retrieves the destionation IP address into a byte array.
void	getDestination(java.lang.StringBuffer buffer) Retrieves the destination IP address as a string into a StringBuffer.
java.net.InetAddress	getDestinationAsInetAddress()
int	getDestinationAsWord()
int	getIPChecksum()
int	getIPHeaderByteLength()
int	getIPHeaderLength()
int	getIPPacketLength()
int	getProtocol()
void	getSource(byte[] address) Retrieves the source IP address into a byte array.
void	getSource(java.lang.StringBuffer buffer) Retrieves the source IP address as a string into a StringBuffer.
java.net.InetAddress	getSourceAsInetAddress()
int	getSourceAsWord()
int	getTTL()
void	setData(byte[] data) Sets the raw packet byte array.
void	setDestinationAsWord(int dest) Sets the destination IP address using a word representation.
void	setIPHeaderLength(int length) Sets the IP header length field.
void	setIPPacketLength(int length) Sets the IP packet total length header value.
void	setProtocol(int protocol) Sets the protocol number.
void	setSourceAsWord(int src) Sets the source IP address using a word representation.
int	size()

Methods inherited from class java.lang.Object

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

Field Detail

OFFSET_TOTAL_LENGTH

public static final int OFFSET_TOTAL_LENGTH

Offset into byte array of total packet length header value.

See Also:

Constant Field Values

OFFSET_SOURCE_ADDRESS

public static final int OFFSET_SOURCE_ADDRESS

Offset into byte array of source address header value.

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Constant Field Values

LENGTH_SOURCE_ADDRESS

public static final int LENGTH_SOURCE_ADDRESS

Number of bytes in source address.

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Constant Field Values

OFFSET_DESTINATION_ADDRESS

public static final int OFFSET_DESTINATION_ADDRESS

Offset into byte array of destination address header value.

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Constant Field Values

LENGTH_DESTINATION_ADDRESS

public static final int LENGTH_DESTINATION_ADDRESS

Number of bytes in destination address.

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Constant Field Values

OFFSET_TTL

public static final int OFFSET_TTL

Offset into byte array of time to live header value.

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Constant Field Values

OFFSET_PROTOCOL

public static final int OFFSET_PROTOCOL

Offset into byte array of protocol number header value.

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Constant Field Values

OFFSET_IP_CHECKSUM

public static final int OFFSET_IP_CHECKSUM

Offset into byte array of header checksum header value.

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Constant Field Values

PROTOCOL_IP

public static final int PROTOCOL_IP

Protocol constant for IPv4.

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Constant Field Values

PROTOCOL_ICMP

public static final int PROTOCOL_ICMP

Protocol constant for ICMP.

See Also:

Constant Field Values

PROTOCOL_TCP

public static final int PROTOCOL_TCP

Protocol constant for TCP.

See Also:

Constant Field Values

PROTOCOL_UDP

public static final int PROTOCOL_UDP

Protocol constant for UDP.

See Also:

Constant Field Values

_data_

protected byte[] _data_

Raw packet data.

Constructor Detail

IPPacket

public IPPacket(int size)

Creates a new IPPacket of a given size.

Parameters:

size - The number of bytes in the packet.

Method Detail

size

public int size()

Returns:

The size of the packet.

setData

public void setData(byte[] data)

Sets the raw packet byte array. Although this method would appear to violate object-oriented principles, it is necessary to implement efficient packet processing. You don't necessarily want to allocate a new IPPacket and data buffer every time a packet arrives and you need to be able to wrap packets from APIs that supply them as byte arrays.

Parameters:

data - The raw packet byte array to wrap.

getData

public void getData(byte[] data)

Copies the raw packet data into a byte array. If the array is too small to hold the data, the data is truncated.

Parameters:

data - The raw packet byte array to wrap.

copy

public final void copy(IPPacket packet)

Copies the contents of an IPPacket to the calling instance. If the two packets are of different lengths, a new byte array is allocated equal to the length of the packet parameter.

Parameters:

packet - The packet to copy from.

setIPPacketLength

public final void setIPPacketLength(int length)

Sets the IP packet total length header value.

Parameters:

length - The total IP packet length in bytes.

getIPPacketLength

public final int getIPPacketLength()

Returns:

The IP packet total length header value.

setIPHeaderLength

public void setIPHeaderLength(int length)

Sets the IP header length field. At most, this can be a four-bit value. The high order bits beyond the fourth bit will be ignored.

Parameters:

length - The length of the IP header in 32-bit words.

getIPHeaderLength

public final int getIPHeaderLength()

Returns:

The length of the IP header in 32-bit words.

getIPHeaderByteLength

public final int getIPHeaderByteLength()

Returns:

The length of the IP header in bytes.

setProtocol

public final void setProtocol(int protocol)

Sets the protocol number.

Parameters:

protocol - The protocol number.

getProtocol

public final int getProtocol()

Returns:

The protocol number.

getTTL

public final int getTTL()

Returns:

The time to live value in seconds.

computeIPChecksum

public final int computeIPChecksum(boolean update)

Computes the IP checksum, optionally updating the IP checksum header.

Parameters:

update - Specifies whether or not to update the IP checksum header after computing the checksum. A value of true indicates the header should be updated, a value of false indicates it should not be updated.

Returns:

The computed IP checksum.

computeIPChecksum

public final int computeIPChecksum()

Same as computeIPChecksum(true);

Returns:

The computed IP checksum value.

getIPChecksum

public final int getIPChecksum()

Returns:

The IP checksum header value.

getSource

public final void getSource(byte[] address)

Retrieves the source IP address into a byte array. The array should be LENGTH_SOURCE_ADDRESS bytes long.

Parameters:

address - The array in which to store the address.

getDestination

public final void getDestination(byte[] address)

Retrieves the destionation IP address into a byte array. The array should be LENGTH_DESTINATION_ADDRESS bytes long.

Parameters:

address - The array in which to store the address.

getSource

public final void getSource(java.lang.StringBuffer buffer)

Retrieves the source IP address as a string into a StringBuffer.

Parameters:

buffer - The StringBuffer in which to store the address.

getDestination

public final void getDestination(java.lang.StringBuffer buffer)

Retrieves the destination IP address as a string into a StringBuffer.

Parameters:

buffer - The StringBuffer in which to store the address.

setSourceAsWord

public final void setSourceAsWord(int src)

Sets the source IP address using a word representation.

Parameters:

src - The source IP address as a 32-bit word.

setDestinationAsWord

public final void setDestinationAsWord(int dest)

Sets the destination IP address using a word representation.

Parameters:

dest - The source IP address as a 32-bit word.

getSourceAsWord

public final int getSourceAsWord()

Returns:

The source IP address as a 32-bit word.

getDestinationAsWord

public final int getDestinationAsWord()

Returns:

The destination IP address as a 32-bit word.

getSourceAsInetAddress

public final java.net.InetAddress getSourceAsInetAddress()
                                                  throws java.net.UnknownHostException

Returns:

The source IP address as a java.net.InetAddress instance.

Throws:

java.net.UnknownHostException

getDestinationAsInetAddress

public final java.net.InetAddress getDestinationAsInetAddress()
                                                       throws java.net.UnknownHostException

Returns:

The destination IP address as a java.net.InetAddress instance.

Throws:

java.net.UnknownHostException