crc.c File Reference

ROHC CRC routines. More...

#include "crc.h"
#include "protocols/ip_numbers.h"
#include "protocols/ip.h"
#include "protocols/ipv4.h"
#include "protocols/ipv6.h"
#include "protocols/udp.h"
#include "protocols/rtp.h"
#include "protocols/esp.h"
#include "protocols/tcp.h"
#include <stdlib.h>
#include <assert.h>

Include dependency graph for crc.c:

Functions
static uint8_t	ipv6_ext_calc_crc_static (const struct rohc_pkt_ip_hdr *const ip_hdr, const rohc_crc_type_t crc_type, const uint8_t init_val)
	Compute the CRC-STATIC part of IPv6 extensions. More...
static uint8_t	ipv6_ext_calc_crc_dyn (const struct rohc_pkt_ip_hdr *const ip_hdr, const rohc_crc_type_t crc_type, const uint8_t init_val)
	Compute the CRC-DYNAMIC part of IPv6 extensions. More...
uint32_t	crc_calc_fcs32 (const uint8_t *const data, const size_t length, const uint32_t init_val)
	Optimized CRC FCS-32 calculation using a table. More...
uint8_t	ip_compute_crc_static (const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs, const rohc_crc_type_t crc_type, const uint8_t init_val)
	Compute the CRC-STATIC part of an IP header. More...
uint8_t	ip_compute_crc_dynamic (const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs, const rohc_crc_type_t crc_type, const uint8_t init_val)
	Compute the CRC-DYNAMIC part of an IP header. More...
uint8_t	compute_crc_ctrl_fields (const rohc_profile_t profile_id, const uint8_t reorder_ratio, const uint16_t msn, const uint8_t ip_id_behaviors[], const size_t ip_id_behaviors_nr)
	Compute the CRC-3 over control fields for ROHCv2 profiles. More...

Variables
static const uint32_t	crc_table_fcs32 [256]
	The pre-computed table for 32-bit Frame Check Sequence (FCS) More...

Detailed Description

ROHC CRC routines.

Author

Didier Barvaux didie.nosp@m.r.ba.nosp@m.rvaux.nosp@m.@tou.nosp@m.louse.nosp@m..viv.nosp@m.eris..nosp@m.com

Didier Barvaux didie.nosp@m.r@ba.nosp@m.rvaux.nosp@m..org

FWX rohc_.nosp@m.team.nosp@m.@dial.nosp@m.ine..nosp@m.fr

Function Documentation

compute_crc_ctrl_fields()

uint8_t compute_crc_ctrl_fields	(	const rohc_profile_t	profile_id,
		const uint8_t	reorder_ratio,
		const uint16_t	msn,
		const uint8_t	ip_id_behaviors[],
		const size_t	ip_id_behaviors_nr
	)

Compute the CRC-3 over control fields for ROHCv2 profiles.

Parameters

profile_id	The current profile ID
reorder_ratio	The 2-bit reorder_ratio control field, padded with 6 MSB of zeroes
msn	The 16-bit MSN control field
ip_id_behaviors	The 2-bit control fields behavior of IP-ID, one per IP header, all are padded with 6 MSB of zeroes
ip_id_behaviors_nr	The number of IP headers, ie. the number of IP-ID behavior control fields to compute the CRC over

Returns

The computed CRC-3

crc_calc_fcs32()

uint32_t crc_calc_fcs32	(	const uint8_t *const	data,
		const size_t	length,
		const uint32_t	init_val
	)

Optimized CRC FCS-32 calculation using a table.

Public functions

Parameters

data	The data to compute the CRC for
length	The size of the data
init_val	The initial value of the CRC

Returns

The 32-bit CRC

ip_compute_crc_dynamic()

uint8_t ip_compute_crc_dynamic	(	const struct rohc_pkt_hdrs *const	uncomp_pkt_hdrs,
		const rohc_crc_type_t	crc_type,
		const uint8_t	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

uncomp_pkt_hdrs	The uncompressed headers to compute CRC for
crc_type	The type of CRC
init_val	The initial CRC value

Returns

The computed CRC

ip_compute_crc_static()

uint8_t ip_compute_crc_static	(	const struct rohc_pkt_hdrs *const	uncomp_pkt_hdrs,
		const rohc_crc_type_t	crc_type,
		const uint8_t	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

uncomp_pkt_hdrs	The uncompressed headers to compute CRC for
crc_type	The type of CRC
init_val	The initial CRC value

Returns

The computed CRC

ipv6_ext_calc_crc_dyn()

static uint8_t ipv6_ext_calc_crc_dyn ( const struct rohc_pkt_ip_hdr *const  ip_hdr, const rohc_crc_type_t  crc_type, const uint8_t  init_val  )

static

Compute the CRC-DYNAMIC part of IPv6 extensions.

Only entire AH header is concerned.

Parameters

ip_hdr	The IP header for which to compute CRC over extension headers
crc_type	The type of CRC
init_val	The initial CRC value

Returns

The compute CRC

ipv6_ext_calc_crc_static()

static uint8_t ipv6_ext_calc_crc_static ( const struct rohc_pkt_ip_hdr *const  ip_hdr, const rohc_crc_type_t  crc_type, const uint8_t  init_val  )

static

Compute the CRC-STATIC part of IPv6 extensions.

Prototypes of private functions

Private functions All extensions are concerned except entire AH header.

Parameters

ip_hdr	The IP header for which to compute CRC over extension headers
crc_type	The type of CRC
init_val	The initial CRC value

Returns

The compute CRC

Variable Documentation

crc_table_fcs32

const uint32_t crc_table_fcs32[256]

static

The pre-computed table for 32-bit Frame Check Sequence (FCS)

x**0 + x**1 + x**2 + x**4 + x**5 + x**7 + x**8 + x**10 + x**11 + x**12 + x**16 + x**22 + x**23 + x**26 + x**32

Copied from RFC 1662, appendix C.3