org.jnetpcap.protocol.tcpip
Class Tcp.AlternateChecksumRequest

java.lang.Object
  org.jnetpcap.nio.JMemory
      org.jnetpcap.nio.JBuffer
          org.jnetpcap.packet.JHeader
              org.jnetpcap.packet.JSubHeader<Tcp>
                  org.jnetpcap.protocol.tcpip.Tcp.TcpOption
                      org.jnetpcap.protocol.tcpip.Tcp.AlternateChecksumRequest

All Implemented Interfaces:

JPayloadAccessor

Enclosing class:

Tcp

@Header(id=14)
public static class Tcp.AlternateChecksumRequest
extends Tcp.TcpOption

The option described in this memo provides a mechanism to negotiate the use of an alternate checksum at connection-establishment time, as well as a mechanism to carry additional checksum information for algorithms that utilize checksums that are longer than 16 bits.

Definition of the option: the TCP Alternate Checksum Request Option may be sent in a SYN segment by a TCP to indicate that the TCP is prepared to both generate and receive checksums based on an alternate algorithm. During communication, the alternate checksum replaces the regular TCP checksum in the checksum field of the TCP header. Should the alternate checksum require more than 2 bytes to transmit, the checksum may either be moved into a TCP Alternate Checksum Data Option and the checksum field of the TCP header be sent as 0, or the data may be split between the header field and the option. Alternate checksums are computed over the same data as the regular TCP checksum.

Author:

Mark Bednarczyk, Sly Technologies, Inc.

Nested Class Summary

static class

Tcp.AlternateChecksumRequest.Algorithm A SYN segment used to originate a connection may contain the Alternate Checksum Request Option, which specifies an alternate checksum-calculation algorithm to be used for the connection.

Nested classes/interfaces inherited from class org.jnetpcap.protocol.tcpip.Tcp.TcpOption

Tcp.TcpOption.OptionCode

Nested classes/interfaces inherited from class org.jnetpcap.packet.JHeader

JHeader.State

Nested classes/interfaces inherited from class org.jnetpcap.nio.JMemory

JMemory.Type

Field Summary

Fields inherited from class org.jnetpcap.packet.JHeader

annotatedHeader, BYTE, EMPTY_HEADER_ARRAY, isSubHeader, packet, state

Fields inherited from class org.jnetpcap.nio.JMemory

JNETPCAP_LIBRARY_NAME, MAX_DIRECT_MEMORY_DEFAULT, POINTER

Constructor Summary

Tcp.AlternateChecksumRequest()

Method Summary

int	algorithm() Specifies the checksum algorithm to be used.
void	algorithm(int value) Sets a new value for algorithm field.
Tcp.AlternateChecksumRequest.Algorithm	algorithmEnum() Returns the algorithm type as enum constant.

Methods inherited from class org.jnetpcap.protocol.tcpip.Tcp.TcpOption

code, code, length, length, lengthCheck, lengthDescription

Methods inherited from class org.jnetpcap.packet.JSubHeader

getLength, getOffset, getParent, setLength, setOffset, setParent

Methods inherited from class org.jnetpcap.packet.JHeader

decode, decodeHeader, getAnnotatedHeader, getDescription, getFields, getGap, getGapLength, getGapOffset, getHeader, getHeaderLength, getHeaderOffset, getId, getIndex, getName, getNextHeaderId, getNextHeaderOffset, getNicname, getPacket, getPayload, getPayloadLength, getPayloadOffset, getPostfix, getPostfixLength, getPostfixOffset, getPrefix, getPrefixLength, getPrefixOffset, getPreviousHeaderId, getPreviousHeaderOffset, getState, getSubHeaders, hasDescription, hasGap, hasNextHeader, hasPayload, hasPostfix, hasPrefix, hasPreviousHeader, hasSubHeaders, isFragmented, isGapTruncated, isHeaderTruncated, isPayloadTruncated, isPostfixTruncated, isPrefixTruncated, peer, peer, peerPayloadTo, setPacket, setSubHeaders, sizeof, toString, transferPayloadTo, transferPayloadTo, transferPayloadTo, validateHeader

Methods inherited from class org.jnetpcap.nio.JBuffer

findUTF8String, getByte, getByteArray, getByteArray, getByteArray, getDouble, getFloat, getInt, getLong, getShort, getUByte, getUInt, getUShort, getUTF8Char, getUTF8String, getUTF8String, getUTF8String, getUTF8String, isReadonly, order, order, peer, peer, peer, peer, setByte, setByteArray, setByteBuffer, setDouble, setFloat, setInt, setLong, setShort, setShort0, setUByte, setUInt, setUShort, transferFrom, transferFrom, transferFrom, transferTo, transferTo, transferTo

Methods inherited from class org.jnetpcap.nio.JMemory

availableDirectMemory, check, cleanup, createReference, isInitialized, isJMemoryBasedOwner, isOwner, maxDirectMemory, peer, reservedDirectMemory, setSize, size, softDirectMemory, toDebugString, toHexdump, toHexdump, totalActiveAllocated, totalAllocateCalls, totalAllocated, totalAllocatedSegments0To255Bytes, totalAllocatedSegments256OrAbove, totalDeAllocateCalls, totalDeAllocated, transferFrom, transferFrom, transferFromDirect, transferOwnership, transferTo, transferTo, transferTo, transferTo, transferTo, transferTo0

Methods inherited from class java.lang.Object

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

Constructor Detail

Tcp.AlternateChecksumRequest

public Tcp.AlternateChecksumRequest()

Method Detail

algorithm

@Field(offset=16,
       length=8)
public int algorithm()

Specifies the checksum algorithm to be used.

Returns:

type of algorithm

algorithmEnum

public Tcp.AlternateChecksumRequest.Algorithm algorithmEnum()

Returns the algorithm type as enum constant.

Returns:

constant representing the algorithm or null if unrecognized

algorithm

public void algorithm(int value)

Sets a new value for algorithm field.

Parameters:

value - new value to set