pcpp::GREv0Layer Class Reference

#include <GreLayer.h>

Inheritance diagram for pcpp::GREv0Layer:

Public Member Functions
	GREv0Layer (uint8_t *data, size_t dataLen, Layer *prevLayer, Packet *packet)
	GREv0Layer ()
gre_basic_header *	getGreHeader () const
bool	getChecksum (uint16_t &checksum)
bool	setChecksum (uint16_t checksum)
bool	unsetChecksum ()
bool	getOffset (uint16_t &offset) const
bool	getKey (uint32_t &key) const
bool	setKey (uint32_t key)
bool	unsetKey ()
void	computeCalculateFields ()
std::string	toString () const
Public Member Functions inherited from pcpp::GreLayer
bool	getSequenceNumber (uint32_t &seqNumber) const
bool	setSequenceNumber (uint32_t seqNumber)
bool	unsetSequenceNumber ()
void	parseNextLayer ()
size_t	getHeaderLen () const
OsiModelLayer	getOsiModelLayer () const
Public Member Functions inherited from pcpp::Layer
virtual	~Layer ()
Layer *	getNextLayer () const
Layer *	getPrevLayer () const
ProtocolType	getProtocol () const
uint8_t *	getData () const
size_t	getDataLen () const
uint8_t *	getLayerPayload () const
size_t	getLayerPayloadSize () const
bool	isAllocatedToPacket () const
void	copyData (uint8_t *toArr) const
uint8_t *	getDataPtr (size_t offset=0) const

Additional Inherited Members
Static Public Member Functions inherited from pcpp::GreLayer
static ProtocolType	getGREVersion (uint8_t *greData, size_t greDataLen)

Detailed Description

Represents a GRE version 0 protocol. Limitation: currently this layer doesn't support GRE routing information parsing and editing. So if a GREv0 packet includes routing information it won't be parse correctly. I didn't add it because of lack of time, but if you need it please tell me and I'll add it

Constructor & Destructor Documentation

GREv0Layer() [1/2]

pcpp::GREv0Layer::GREv0Layer ( uint8_t *  data, size_t  dataLen, Layer *  prevLayer, Packet *  packet  )

inline

A constructor that creates the layer from an existing packet raw data

Parameters

[in]	data	A pointer to the raw data
[in]	dataLen	Size of the data in bytes
[in]	prevLayer	A pointer to the previous layer
[in]	packet	A pointer to the Packet instance where layer will be stored in

GREv0Layer() [2/2]

pcpp::GREv0Layer::GREv0Layer

(

)

A constructor that creates a new GREv0 header and allocates the data

Member Function Documentation

computeCalculateFields()

void pcpp::GREv0Layer::computeCalculateFields ( )

virtual

Calculate the following fields:

• gre_basic_header::protocol
• GRE checksum field (if exists in packet)

Implements pcpp::Layer.

getChecksum()

bool pcpp::GREv0Layer::getChecksum

(

uint16_t &

checksum

)

Get checksum value if field exists in layer

Parameters

[out]

checksum

The returned checksum value if exists in layer. Else remain unchanged

Returns

True if checksum field exists in layer. In this case checksum parameter will be filled with the value. Or false if checksum field doesn't exist in layer

getGreHeader()

gre_basic_header* pcpp::GREv0Layer::getGreHeader ( ) const

inline

Get a pointer to the basic GRE header containing only non-optional fields. Notice this points directly to the data, so every change will change the actual packet data. Also please notice that changing the set bits (gre_basic_header::strictSourceRouteBit, gre_basic_header::sequenceNumBit, gre_basic_header::keyBit, gre_basic_header::routingBit, gre_basic_header::checksumBit, gre_basic_header::ackSequenceNumBit) without using the proper set or unset methods (such as setChecksum(), unsetChecksum(), etc.) may result to wrong calculation of header length and really weird bugs. Please avoid doing so

Returns

A pointer to the gre_basic_header

getKey()

bool pcpp::GREv0Layer::getKey

(

uint32_t &

key

)

const

Get key value if field exists in layer

Parameters

[out]

key

The returned key value if exists in layer. Else remain unchanged

Returns

True if key field exists in layer. In this case key parameter will be filled with the value. Or false if key field doesn't exist in layer

getOffset()

bool pcpp::GREv0Layer::getOffset

(

uint16_t &

offset

)

const

Get offset value if field exists in layer. Notice there is no setOffset() method as GRE routing information isn't supported yet (see comment on class description)

Parameters

[out]

offset

The returned offset value if exists in layer. Else remain unchanged

Returns

True if offset field exists in layer. In this case offset parameter will be filled with the value. Or false if offset field doesn't exist in layer

setChecksum()

bool pcpp::GREv0Layer::setChecksum

(

uint16_t

checksum

)

Set checksum value. If checksum or offset fields already exist (gre_basic_header::checksumBit or gre_basic_header::routingBit are set) then only the new value is set. If both fields don't exist a new 4-byte value will be added to the layer, gre_basic_header::checksumBit will be set (gre_basic_header::routingBit will remain unset), the new checksum value will be set and offset value will be set to 0. The reason both fields are added is that GREv0 protocol states both of them or none of them should exist on packet (even if only one of the bits are set)

Parameters

[in]

checksum

The checksum value to set

Returns

True if managed to set the value/s successfully, or false otherwise (if couldn't extend the layer)

setKey()

bool pcpp::GREv0Layer::setKey

(

uint32_t

key

)

Set key value. If field already exists (gre_basic_header::keyBit is set) then only the new value is set. If field doesn't exist it will be added to the layer, gre_basic_header::keyBit will be set and the new value will be set

Parameters

[in]

key

The key value to set

Returns

True if managed to set the value successfully, or false otherwise (if couldn't extend the layer)

toString()

std::string pcpp::GREv0Layer::toString ( ) const

virtual

Returns

A string representation of the layer most important data (should look like the layer description in Wireshark)

Implements pcpp::Layer.

unsetChecksum()

bool pcpp::GREv0Layer::unsetChecksum

(

)

Unset checksum and possibly remove it from the layer. It will be removed from the layer only if gre_basic_header::routingBit is not set as well. Otherwise checksum field will remain on packet with value of 0

Returns

True if managed to unset successfully or false (and error log) if checksum wasn't set in the first place or if didn't manage to remove it from the layer

unsetKey()

bool pcpp::GREv0Layer::unsetKey

(

)

Unset key and remove it from the layer

Returns

True if managed to unset successfully or false (and error log) if key wasn't set in the first place or if didn't manage to remove it from the layer