d_rtp.c File Reference

ROHC decompression context for the RTP profile. More...

#include "d_udp.h"
#include "d_ip.h"
#include "rohc_traces_internal.h"
#include "rohc_bit_ops.h"
#include "rohc_debug.h"
#include "rohc_utils.h"
#include "sdvl.h"
#include "crc.h"
#include "schemes/scaled_rtp_ts.h"
#include "rohc_decomp_detect_packet.h"
#include "protocols/udp.h"
#include "protocols/rtp.h"
#include <string.h>
#include <assert.h>

Include dependency graph for d_rtp.c:

Data Structures
struct	d_rtp_context
	Define the RTP part of the decompression profile context. More...
Functions
static void	d_rtp_destroy (void *const context)
	Destroy the given RTP context.
static rohc_packet_t	rtp_detect_packet_type (const struct rohc_decomp_ctxt *const context, const uint8_t *const rohc_packet, const size_t rohc_length, const size_t large_cid_len)
	Detect the type of ROHC packet for RTP profile.
static rohc_packet_t	rtp_choose_uo1_variant (const struct rohc_decomp_ctxt *const context, const uint8_t *const packet, const size_t rohc_length)
	Choose between UO-1-RTP, UO-1-TS, and UO-1-ID variants.
static rohc_packet_t	rtp_choose_uor2_variant (const struct rohc_decomp_ctxt *const context, const uint8_t *const packet, const size_t rohc_length, const size_t large_cid_len)
	Choose between UOR-2-RTP, UOR-2-TS, and UOR-2-ID variants.
static int	rtp_parse_static_rtp (const struct rohc_decomp_ctxt *const context, const unsigned char *packet, size_t length, struct rohc_extr_bits *const bits)
	Parse the UDP/RTP static part of the ROHC packet.
static int	rtp_parse_dynamic_rtp (const struct rohc_decomp_ctxt *const context, const uint8_t *packet, const size_t length, struct rohc_extr_bits *const bits)
	Parse the UDP/RTP dynamic part of the ROHC packet.
static int	rtp_parse_ext3 (const struct rohc_decomp_ctxt *const context, const unsigned char *const rohc_data, const size_t rohc_data_len, const rohc_packet_t packet_type, struct rohc_extr_bits *const bits)
	Parse the extension 3 of the UO-1-ID or UOR-2* packet.
static bool	is_uor2_reparse_required (const rohc_packet_t packet_type, const int are_all_ipv4_rnd)
	Does the UOR-2* packet need to be parsed again?
static int	rtp_parse_uo_remainder (const struct rohc_decomp_ctxt *const context, const unsigned char *packet, unsigned int length, struct rohc_extr_bits *const bits)
	Parse the UDP/RTP tail of the UO* ROHC packets.
static bool	rtp_decode_values_from_bits (const struct rohc_decomp_ctxt *context, const struct rohc_extr_bits bits, struct rohc_decoded_values *const decoded)
	Decode UDP values from extracted bits.
static int	rtp_build_uncomp_rtp (const struct rohc_decomp_ctxt *const context, const struct rohc_decoded_values decoded, unsigned char *dest, const unsigned int payload_len)
	Build an uncompressed UDP/RTP header.
static void	rtp_update_context (const struct rohc_decomp_ctxt *context, const struct rohc_decoded_values decoded)
	Update context with decoded UDP/RTP values.
static bool	is_outer_ipv4_ctxt (const struct d_generic_context *const ctxt)
	Is the outer IP header IPv4 wrt context?
static bool	is_outer_ipv4_rnd_ctxt (const struct d_generic_context *const ctxt)
	Is the outer IP header IPv4 and its IP-ID random wrt context?
static bool	is_inner_ipv4_ctxt (const struct d_generic_context *const ctxt)
	Is the inner IP header IPv4 wrt context?
static bool	is_inner_ipv4_rnd_ctxt (const struct d_generic_context *const ctxt)
	Is the inner IP header IPv4 and its IP-ID random wrt context?
void *	d_rtp_create (const struct rohc_decomp_ctxt *const context)
	Create the RTP decompression context.
Variables
struct rohc_decomp_profile	d_rtp_profile
	Define the decompression part of the RTP profile as described in the RFC 3095.

---

Detailed Description

ROHC decompression context for the RTP profile.

Author:

David Moreau from TAS

Didier Barvaux <didier.barvaux@toulouse.viveris.com>

Didier Barvaux <didier@barvaux.org>

---

Function Documentation

void* d_rtp_create

(

const struct rohc_decomp_ctxt *const

context

)

Create the RTP decompression context.

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

Returns:

The newly-created RTP decompression context

static void d_rtp_destroy

(

void *const

context

)

[static]

Destroy the given RTP context.

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

Parameters:

context

The RTP compression context to destroy

static bool is_inner_ipv4_ctxt

(

const struct d_generic_context *const

ctxt

)

[inline, static]

Is the inner IP header IPv4 wrt context?

Parameters:

ctxt	The generic decompression context

Returns:

true if IPv4, false otherwise

static bool is_inner_ipv4_rnd_ctxt

(

const struct d_generic_context *const

ctxt

)

[inline, static]

Is the inner IP header IPv4 and its IP-ID random wrt context?

Parameters:

ctxt	The generic decompression context

Returns:

true if IPv4, false otherwise

static bool is_outer_ipv4_ctxt

(

const struct d_generic_context *const

ctxt

)

[inline, static]

Is the outer IP header IPv4 wrt context?

Parameters:

ctxt	The generic decompression context

Returns:

true if IPv4, false otherwise

static bool is_outer_ipv4_rnd_ctxt

(

const struct d_generic_context *const

ctxt

)

[inline, static]

Is the outer IP header IPv4 and its IP-ID random wrt context?

Parameters:

ctxt	The generic decompression context

Returns:

true if IPv4, false otherwise

static bool is_uor2_reparse_required	(	const rohc_packet_t	packet_type,
		const int	are_all_ipv4_rnd
	)		[inline, static]

Does the UOR-2* packet need to be parsed again?

When parsing a UOR-2* packet, if RND changes, the packet might need to be parsed again with another UOR-2* packet type in mind:

• UOR-2-RTP needs to be parsed again as UOR-2-ID or UOR-2-TS if one of the RND flags becomes 0.
• UOR-2-ID needs to be parsed again as UOR-2-RTP if none of the RND flags is 0 anymore.
• UOR-2-TS needs to be parsed again as UOR-2-RTP if none of the RND flags is 0 anymore.

Parameters:

packet_type	The packet type
are_all_ipv4_rnd	Whether all RND values for outer and inner IP headers are set to 1

Returns:

Whether packet shall be parsed again or not

static int rtp_build_uncomp_rtp	(	const struct rohc_decomp_ctxt *const	context,
		const struct rohc_decoded_values	decoded,
		unsigned char *	dest,
		const unsigned int	payload_len
	)		[static]

Build an uncompressed UDP/RTP header.

Parameters:

context	The decompression context
decoded	The values decoded from the ROHC header
dest	The buffer to store the UDP/RTP header (MUST be at least of sizeof(struct udphdr) + sizeof(struct rtphdr) length)
payload_len	The length of the UDP/RTP payload

Returns:

The length of the next header (ie. the UDP/RTP header), -1 in case of error

static rohc_packet_t rtp_choose_uo1_variant	(	const struct rohc_decomp_ctxt *const	context,
		const uint8_t *const	packet,
		const size_t	rohc_length
	)		[static]

Choose between UO-1-RTP, UO-1-TS, and UO-1-ID variants.

This function is useful to choose which packet type to try to parse in the UO-1* families.

Parameters:

context	The decompression context
packet	The ROHC packet
rohc_length	The length of the ROHC packet

Returns:

The packet type

static rohc_packet_t rtp_choose_uor2_variant	(	const struct rohc_decomp_ctxt *const	context,
		const uint8_t *const	packet,
		const size_t	rohc_length,
		const size_t	large_cid_len
	)		[static]

Choose between UOR-2-RTP, UOR-2-TS, and UOR-2-ID variants.

This function is useful to choose which packet type to try to decode (may change later, causing a packet reparse) in the UOR-2* family.

Parameters:

context	The decompression context
packet	The ROHC packet
rohc_length	The length of the ROHC packet
large_cid_len	The length of the optional large CID field

Returns:

The packet type

static bool rtp_decode_values_from_bits	(	const struct rohc_decomp_ctxt *	context,
		const struct rohc_extr_bits	bits,
		struct rohc_decoded_values *const	decoded
	)		[static]

Decode UDP values from extracted bits.

The following values are decoded:

• UDP source port
• UDP destination port
• UDP checksum
• RTP TimeStamp (TS)
• RTP Marker (M) flag
• RTP eXtension (R-X) flag
• RTP Padding (R-P) flag
• RTP Payload Type (R-PT)

Parameters:

context	The decompression context
bits	The extracted bits
decoded	OUT: The corresponding decoded values

Returns:

true if decoding is successful, false otherwise

static rohc_packet_t rtp_detect_packet_type	(	const struct rohc_decomp_ctxt *const	context,
		const uint8_t *const	rohc_packet,
		const size_t	rohc_length,
		const size_t	large_cid_len
	)		[static]

Detect the type of ROHC packet for RTP profile.

Parameters:

context	The decompression context
rohc_packet	The ROHC packet
rohc_length	The length of the ROHC packet
large_cid_len	The length of the optional large CID field

Returns:

The packet type

static int rtp_parse_dynamic_rtp	(	const struct rohc_decomp_ctxt *const	context,
		const uint8_t *	packet,
		const size_t	length,
		struct rohc_extr_bits *const	bits
	)		[static]

Parse the UDP/RTP dynamic part of the ROHC packet.

Parameters:

context	The decompression context
packet	The ROHC packet to parse
length	The length of the ROHC packet
bits	OUT: The bits extracted from the ROHC header

Returns:

The number of bytes read in the ROHC packet, -1 in case of failure

static int rtp_parse_ext3	(	const struct rohc_decomp_ctxt *const	context,
		const unsigned char *const	rohc_data,
		const size_t	rohc_data_len,
		const rohc_packet_t	packet_type,
		struct rohc_extr_bits *const	bits
	)		[static]

Parse the extension 3 of the UO-1-ID or UOR-2* packet.

 Extension 3 for RTP profile (5.7.5):

       0     1     2     3     4     5     6     7
    +-----+-----+-----+-----+-----+-----+-----+-----+
 1  |  1     1  |  S  |R-TS | Tsc |  I  | ip  | rtp |
    +-----+-----+-----+-----+-----+-----+-----+-----+
 2  |            Inner IP header flags        | ip2 |  if ip = 1
    +-----+-----+-----+-----+-----+-----+-----+-----+
 3  |            Outer IP header flags              |  if ip2 = 1
    +-----+-----+-----+-----+-----+-----+-----+-----+
 4  |                      SN                       |  if S = 1
    +-----+-----+-----+-----+-----+-----+-----+-----+
    |                                               |
4.1 /                      TS                       / 1-4 octets, if R-TS = 1
    |                                               |
    +-----+-----+-----+-----+-----+-----+-----+-----+
    |                                               |
 5  /            Inner IP header fields             /  variable,
    |                                               |  if ip = 1
    +-----+-----+-----+-----+-----+-----+-----+-----+
 6  |                     IP-ID                     |  2 octets, if I = 1
    +-----+-----+-----+-----+-----+-----+-----+-----+
    |                                               |
 7  /            Outer IP header fields             /  variable,
    |                                               |  if ip2 = 1
    +-----+-----+-----+-----+-----+-----+-----+-----+
    |                                               |  variable,
 8  /          RTP Header flags and fields          /  if rtp = 1
    |                                               |
    +-----+-----+-----+-----+-----+-----+-----+-----+

Parameters:

context	The decompression context
rohc_data	The ROHC data to parse
rohc_data_len	The length of the ROHC data to parse
packet_type	The type of ROHC packet to parse
bits	IN: the bits already found in base header OUT: the bits found in the extension header 3

Returns:

The data length read from the ROHC packet, -2 in case packet must be reparsed, -1 in case of error

static int rtp_parse_static_rtp	(	const struct rohc_decomp_ctxt *const	context,
		const unsigned char *	packet,
		size_t	length,
		struct rohc_extr_bits *const	bits
	)		[static]

Parse the UDP/RTP static part of the ROHC packet.

Parameters:

context	The decompression context
packet	The ROHC packet to parse
length	The length of the ROHC packet
bits	OUT: The bits extracted from the ROHC header

Returns:

The number of bytes read in the ROHC packet, -1 in case of failure

static int rtp_parse_uo_remainder	(	const struct rohc_decomp_ctxt *const	context,
		const unsigned char *	packet,
		unsigned int	length,
		struct rohc_extr_bits *const	bits
	)		[static]

Parse the UDP/RTP tail of the UO* ROHC packets.

Parameters:

context	The decompression context
packet	The ROHC packet to parse
length	The length of the ROHC packet
bits	OUT: The bits extracted from the ROHC header

Returns:

The number of bytes read in the ROHC packet, -1 in case of failure

static void rtp_update_context	(	const struct rohc_decomp_ctxt *	context,
		const struct rohc_decoded_values	decoded
	)		[static]

Update context with decoded UDP/RTP values.

The following decoded values are updated in context:

• UDP source port
• UDP destination port
• RTP TimeStamp (TS)
• all other static/dynamic RTP fields

Parameters:

context	The decompression context
decoded	The decoded values to update in the context

---

Variable Documentation

struct rohc_decomp_profile d_rtp_profile

Initial value:

{
        .id              = ROHC_PROFILE_RTP, 
        .new_context     = d_rtp_create,
        .free_context    = d_rtp_destroy,
        .decode          = d_generic_decode,
        .detect_pkt_type = rtp_detect_packet_type,
        .get_sn          = d_generic_get_sn,
}

Define the decompression part of the RTP profile as described in the RFC 3095.