Module org.newsclub.net.unix.darwin

Package org.newsclub.net.unix.darwin.system

Class IPUtil

java.lang.Object

org.newsclub.net.unix.darwin.system.IPUtil

public final class IPUtil
extends Object

Some IP protocol-related helper methods.

Author:

Christian Kohlschütter

Field Summary

Fields

Modifier and Type	Field	Description
static final byte	AF_INET_PROTOCOL_ICMP	The ICMP protocol.
static final int	DOMAIN_AF_INET	The identifier for AF_INET (at least on Darwin).
static final int	DOMAIN_HEADER_LENGTH	The length (in bytes) of the "domain" header used in loopback packet systems like UTUN_CONTROL.
static final int	IPV4_DEFAULT_HEADER_SIZE	The length (in bytes) of an IPv4 header without options.

Method Summary

Modifier and Type	Method	Description
static int	checksumICMPheader(ByteBuffer bb, int start, int end)	Computes the checksum for an ICMP header, and overwrites any existing checksum with the correct one.
static int	checksumIPv4header(ByteBuffer bb, int start, int end)	Computes the checksum for an IPv4 header, and overwrites any existing checksum with the correct one.
static void	putICMPEchoResponse(ByteBuffer bb, short echoIdentifier, short sequenceNumber, ByteBuffer payload)	Put (write) an ICMP echo response header to the given byte buffer, using the given parameters.
static void	putIPv4Header(ByteBuffer bb, int payloadLength, byte protocol, int srcIP, int dstIP)	Put (write) an IPv4 header to the given byte buffer, using the given parameters.

Methods inherited from class java.lang.Object

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

Field Details

DOMAIN_HEADER_LENGTH

public static final int DOMAIN_HEADER_LENGTH

The length (in bytes) of the "domain" header used in loopback packet systems like UTUN_CONTROL.

See Also:

• Constant Field Values

DOMAIN_AF_INET

public static final int DOMAIN_AF_INET

The identifier for AF_INET (at least on Darwin).

See Also:

• Constant Field Values

IPV4_DEFAULT_HEADER_SIZE

public static final int IPV4_DEFAULT_HEADER_SIZE

The length (in bytes) of an IPv4 header without options.

See Also:

• Constant Field Values

AF_INET_PROTOCOL_ICMP

public static final byte AF_INET_PROTOCOL_ICMP

The ICMP protocol.

See Also:

• Constant Field Values

Method Details

checksumIPv4header

public static int checksumIPv4header(ByteBuffer bb,
 int start,
 int end)

Computes the checksum for an IPv4 header, and overwrites any existing checksum with the correct one.

Parameters:

bb - The buffer containing the IPv4 header

start - The beginning position of the header in the buffer.

end - The end position (exclusive) of the header in the buffer.

Returns:

The computed 16-bit checksum

checksumICMPheader

public static int checksumICMPheader(ByteBuffer bb,
 int start,
 int end)

Computes the checksum for an ICMP header, and overwrites any existing checksum with the correct one. Also see RFC 792.

Parameters:

bb - The buffer containing the ICMP header

start - The beginning position of the header in the buffer.

end - The end position (exclusive) of the header in the buffer.

Returns:

The computed 16-bit checksum

putIPv4Header

public static void putIPv4Header(ByteBuffer bb,
 int payloadLength,
 byte protocol,
 int srcIP,
 int dstIP)

Put (write) an IPv4 header to the given byte buffer, using the given parameters. This should write exactly 20 bytes to the buffer. The buffer position then is at the end of the header.

Parameters:

bb - The target byte buffer.

payloadLength - The length of the payload (excluding the IPv4 header).

protocol - The protocol identifier.

srcIP - The source IPv4 address.

dstIP - The destination IPv4 address.

putICMPEchoResponse

public static void putICMPEchoResponse(ByteBuffer bb,
 short echoIdentifier,
 short sequenceNumber,
 ByteBuffer payload)

Put (write) an ICMP echo response header to the given byte buffer, using the given parameters.

Parameters:

bb - The target byte buffer.

echoIdentifier - The identifier, from the ICMP echo request.

sequenceNumber - The sequence number, from the ICMP echo request.

payload - The payload, from the ICMP echo request.