ROHC CRC routines. More...

#include "crc.h"
#include "rtp.h"
#include <netinet/udp.h>
#include <assert.h>

Include dependency graph for crc.c:

Functions
int	crc_get_polynom (int type)
	Get the polynom for the CRC type.
void	crc_init_table (unsigned char *table, unsigned char poly)
	Initialize a table given a 256 bytes table and the polynom to use.
unsigned int	crc_calculate (int type, unsigned char *data, int length, unsigned int init_val)
	Calculate the checksum for the given data.
unsigned int	compute_crc_static (const unsigned char ip, const unsigned char ip2, const unsigned char *next_header, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-STATIC part of an IP header.
unsigned int	compute_crc_dynamic (const unsigned char ip, const unsigned char ip2, const unsigned char *next_header, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-DYNAMIC part of an IP header.
unsigned int	udp_compute_crc_static (const unsigned char ip, const unsigned char ip2, const unsigned char *next_header, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-STATIC part of an UDP or UDO-Lite header.
unsigned int	udp_compute_crc_dynamic (const unsigned char ip, const unsigned char ip2, const unsigned char *next_header, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-DYNAMIC part of an UDP or UDP-Lite header.
unsigned int	rtp_compute_crc_static (const unsigned char ip, const unsigned char ip2, const unsigned char *next_header, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-STATIC part of a RTP header.
unsigned int	rtp_compute_crc_dynamic (const unsigned char ip, const unsigned char ip2, const unsigned char *next_header, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-DYNAMIC part of a RTP header.
unsigned int	ipv6_ext_compute_crc_static (const unsigned char *ip, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-STATIC part of IPv6 extensions.
unsigned int	ipv6_ext_compute_crc_dynamic (const unsigned char *ip, unsigned int crc_type, unsigned int init_val)
	Compute the CRC-DYNAMIC part of IPv6 extensions.
Variables
unsigned char	crc_table_8 [256]
	Table to enable fast CRC-8 computation.
unsigned char	crc_table_7 [256]
	Table to enable fast CRC-7 computation.
unsigned char	crc_table_6 [256]
	Table to enable fast CRC-6 computation.
unsigned char	crc_table_3 [256]
	Table to enable fast CRC-3 computation.
unsigned char	crc_table_2 [256]
	Table to enable fast CRC-2 computation.

Detailed Description

ROHC CRC routines.

Author:: Didier Barvaux <didier.barvaux@toulouse.viveris.com>; The hackers from ROHC for Linux

Function Documentation

unsigned int compute_crc_dynamic	(	const unsigned char *	ip,
		const unsigned char *	ip2,
		const unsigned char *	next_header,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-DYNAMIC part of an IP header.

Concerned fields are:

bytes 3-4, 5-6, 11-12 in original IPv4 header
bytes 5-6 in original IPv6 header

Parameters:

ip	The outer IP packet
ip2	The inner IP packet if there is 2 IP headers, NULL otherwise
next_header	The next header located after the IP header(s)
crc_type	The type of CRC
init_val	The initial CRC value

Returns:: The checksum

References crc_calculate(), get_ip_version(), IPV4, ipv6_ext_compute_crc_dynamic(), and version.

Referenced by c_generic_create(), d_generic_create(), and udp_compute_crc_dynamic().

unsigned int compute_crc_static	(	const unsigned char *	ip,
		const unsigned char *	ip2,
		const unsigned char *	next_header,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-STATIC part of an IP header.

Concerned fields are: all fields expect those for CRC-DYNAMIC

bytes 1-2, 7-10, 13-20 in original IPv4 header
bytes 1-4, 7-40 in original IPv6 header

This function is one of the functions that must exist in one profile for the framework to work.

Parameters:

ip	The outer IP packet
ip2	The inner IP packet if there is 2 IP headers, NULL otherwise
next_header	The next header located after the IP header(s)
crc_type	The type of CRC
init_val	The initial CRC value

Returns:: The checksum

References crc_calculate(), get_ip_version(), IPV4, ipv6_ext_compute_crc_static(), and version.

Referenced by c_generic_create(), d_generic_create(), and udp_compute_crc_static().

unsigned int crc_calculate	(	int	type,
		unsigned char *	data,
		int	length,
		unsigned int	init_val
	)

Calculate the checksum for the given data.

Parameters:

type	The CRC type (CRC_TYPE_2, CRC_TYPE_3, CRC_TYPE_6, CRC_TYPE_7 or CRC_TYPE_8)
data	The data to calculate the checksum on
length	The length of the data
init_val	The initial CRC value

Returns:: The checksum

References CRC_TYPE_2, CRC_TYPE_3, CRC_TYPE_6, CRC_TYPE_7, and CRC_TYPE_8.

Referenced by c_generic_feedback(), c_uncompressed_feedback(), code_IR_DYN_packet(), code_IR_packet(), compute_crc_dynamic(), compute_crc_static(), f_wrap_feedback(), ipv6_ext_compute_crc_dynamic(), ipv6_ext_compute_crc_static(), rohc_ir_dyn_packet_crc_ok(), rohc_ir_packet_crc_ok(), rtp_compute_crc_dynamic(), rtp_compute_crc_static(), udp_compute_crc_dynamic(), udp_compute_crc_static(), and uncompressed_code_IR_packet().

int crc_get_polynom ( int type )

Get the polynom for the CRC type.

Public functions

Parameters:

type	The CRC type

Returns:: The polynom for the requested CRC type

References CRC_TYPE_2, CRC_TYPE_3, CRC_TYPE_6, CRC_TYPE_7, and CRC_TYPE_8.

void crc_init_table	(	unsigned char *	table,
		unsigned char	poly
	)

Initialize a table given a 256 bytes table and the polynom to use.

Parameters:

table	The 256 bytes table
poly	The polynom

unsigned int ipv6_ext_compute_crc_dynamic	(	const unsigned char *	ip,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-DYNAMIC part of IPv6 extensions.

Only entire AH header is concerned.

Parameters:

ip	The IPv6 packet
crc_type	The type of CRC
init_val	The initial CRC value

Returns:: The checksum

References crc_calculate(), ip_get_extension_size(), ip_get_next_ext_header_from_ext(), and IPV6_EXT_AUTH.

Referenced by compute_crc_dynamic().

unsigned int ipv6_ext_compute_crc_static	(	const unsigned char *	ip,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-STATIC part of IPv6 extensions.

All extensions are concerned except entire AH header.

Parameters:

ip	The IPv6 packet
crc_type	The type of CRC
init_val	The initial CRC value

Returns:: The checksum

References crc_calculate(), ip_get_extension_size(), ip_get_next_ext_header_from_ext(), and IPV6_EXT_AUTH.

Referenced by compute_crc_static().

unsigned int rtp_compute_crc_dynamic	(	const unsigned char *	ip,
		const unsigned char *	ip2,
		const unsigned char *	next_header,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-DYNAMIC part of a RTP header.

Concerned fields are:

bytes 2, 3-4, 5-8 in original RTP header

Parameters:

ip	The outer IP packet
ip2	The inner IP packet if there is 2 IP headers, NULL otherwise
next_header	The next header located after the IP header(s)
crc_type	The type of CRC
init_val	The initial CRC value

Returns:: The checksum

References crc_calculate(), and udp_compute_crc_dynamic().

Referenced by c_rtp_create(), and d_rtp_create().

unsigned int rtp_compute_crc_static	(	const unsigned char *	ip,
		const unsigned char *	ip2,
		const unsigned char *	next_header,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-STATIC part of a RTP header.

Concerned fields are: all fields expect those for CRC-DYNAMIC

bytes 1, 9-12 (and CSRC list) in original RTP header

Parameters:

ip	The outer IP packet
ip2	The inner IP packet if there is 2 IP headers, NULL otherwise
next_header	The next header located after the IP header(s)
crc_type	The type of CRC
init_val	The initial CRC value

Returns:: The checksum

References crc_calculate(), and udp_compute_crc_static().

Referenced by c_rtp_create(), and d_rtp_create().

unsigned int udp_compute_crc_dynamic	(	const unsigned char *	ip,
		const unsigned char *	ip2,
		const unsigned char *	next_header,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-DYNAMIC part of an UDP or UDP-Lite header.

Concerned fields are:

bytes 5-6, 7-8 in original UDP header

Parameters:

ip	The outer IP packet
ip2	The inner IP packet if there is 2 IP headers, NULL otherwise
next_header	The next header located after the IP header(s)
crc_type	The type of CRC
init_val	The initial CRC value

Returns:: The checksum

References compute_crc_dynamic(), and crc_calculate().

Referenced by c_udp_create(), c_udp_lite_create(), d_udp_create(), d_udp_lite_create(), and rtp_compute_crc_dynamic().

unsigned int udp_compute_crc_static	(	const unsigned char *	ip,
		const unsigned char *	ip2,
		const unsigned char *	next_header,
		unsigned int	crc_type,
		unsigned int	init_val
	)

Compute the CRC-STATIC part of an UDP or UDO-Lite header.

Concerned fields are: all fields expect those for CRC-DYNAMIC

bytes 1-4 in original UDP header

Parameters:

ip	The outer IP packet
ip2	The inner IP packet if there is 2 IP headers, NULL otherwise
next_header	The next header located after the IP header(s)
crc_type	The type of CRC
init_val	The initial CRC value