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

#include "c_rtp.h"
#include "c_udp.h"
#include "rohc_traces_internal.h"
#include "rohc_packets.h"
#include "rohc_utils.h"
#include "sdvl.h"
#include "crc.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>

Include dependency graph for c_rtp.c:

Functions
static bool	c_rtp_create (struct rohc_comp_ctxt const context, const struct net_pkt const packet)
	Create a new RTP context and initialize it thanks to the given IP/UDP/RTP packet. More...

static void	c_rtp_destroy (struct rohc_comp_ctxt *const context)
	Destroy the RTP context. More...

static bool	c_rtp_check_profile (const struct rohc_comp const comp, const struct net_pkt const packet)
	Check if the given packet corresponds to the RTP profile. More...

static bool	c_rtp_check_context (const struct rohc_comp_ctxt const context, const struct net_pkt const packet, size_t *const cr_score)
	Check if the IP/UDP/RTP packet belongs to the context. More...

static int	c_rtp_encode (struct rohc_comp_ctxt const context, const struct net_pkt const uncomp_pkt, uint8_t const rohc_pkt, const size_t rohc_pkt_max_len, rohc_packet_t const packet_type, size_t *const payload_offset)
	Encode an IP/UDP/RTP packet according to a pattern decided by several different factors. More...

static void	rtp_decide_state (struct rohc_comp_ctxt *const context)
	Decide the state that should be used for the next packet compressed with the ROHC RTP profile. More...

static rohc_packet_t	c_rtp_decide_FO_packet (const struct rohc_comp_ctxt *context)
	Decide which packet to send when in First Order (FO) state. More...

static rohc_packet_t	c_rtp_decide_SO_packet (const struct rohc_comp_ctxt *context)
	Decide which packet to send when in Second Order (SO) state. More...

static rohc_ext_t	c_rtp_decide_extension (const struct rohc_comp_ctxt *context)
	Decide what extension shall be used in the UO-1/UO-2 packet. More...

static uint32_t	c_rtp_get_next_sn (const struct rohc_comp_ctxt const context, const struct net_pkt const uncomp_pkt)
	Determine the SN value for the next packet. More...

static bool	rtp_encode_uncomp_fields (struct rohc_comp_ctxt const context, const struct net_pkt const uncomp_pkt)
	Encode uncompressed RTP fields. More...

static size_t	rtp_code_static_rtp_part (const struct rohc_comp_ctxt const context, const uint8_t const next_header, uint8_t *const dest, const size_t counter)
	Build the static part of the UDP/RTP headers. More...

static size_t	rtp_code_dynamic_rtp_part (const struct rohc_comp_ctxt const context, const uint8_t const next_header, uint8_t *const dest, const size_t counter)
	Build the dynamic part of the UDP/RTP headers. More...

static int	rtp_changed_rtp_dynamic (const struct rohc_comp_ctxt const context, const struct udphdr const udp, const struct rtphdr *const rtp)
	Check if the dynamic part of the UDP/RTP headers changed. More...

Variables
const struct rohc_comp_profile	c_rtp_profile
	Define the compression part of the RTP profile as described in the RFC 3095. More...

Detailed Description

ROHC compression context for the RTP profile.

Author: David Moreau from TAS; 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

Function Documentation

◆ c_rtp_check_context()

static bool c_rtp_check_context	(	const struct rohc_comp_ctxt *const	context,
		const struct net_pkt *const	packet,
		size_t *const	cr_score
	)

static

Check if the IP/UDP/RTP packet belongs to the context.

Conditions are:

the number of IP headers must be the same as in context
IP version of the two IP headers must be the same as in context
IP packets must not be fragmented
the source and destination addresses of the two IP headers must match the ones in the context
the transport protocol must be UDP
the source and destination ports of the UDP header must match the ones in the context
IPv6 only: the Flow Label of the two IP headers must match the ones the context
the SSRC field of the RTP header must match the one in the context

All the context but the last one are done by the c_udp_check_context() function.

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

Parameters

	context	The compression context
	packet	The IP/UDP/RTP packet to check
[out]	cr_score	The score of the context for Context Replication (CR)

Returns: true if the IP/UDP/RTP packet belongs to the context false if it does not belong to the context

See also: c_udp_check_context

◆ c_rtp_check_profile()

static bool c_rtp_check_profile	(	const struct rohc_comp *const	comp,
		const struct net_pkt *const	packet
	)

static

Check if the given packet corresponds to the RTP profile.

Conditions are:

the transport protocol is UDP
the version of the outer IP header is 4 or 6
the outer IP header is not an IP fragment
if there are at least 2 IP headers, the version of the inner IP header is 4 or 6
if there are at least 2 IP headers, the inner IP header is not an IP fragment
the inner IP payload is at least 8-byte long for UDP header
the UDP Length field and the UDP payload match
the UDP payload is at least 12-byte long for RTP header
the UDP ports are in the list of RTP ports or the user-defined RTP callback function detected one RTP packet

See also: c_udp_check_profile

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

Parameters

comp	The ROHC compressor
packet	The packet to check

Returns

Whether the IP packet corresponds to the profile:

true if the IP packet corresponds to the profile,
false if the IP packet does not correspond to the profile

◆ c_rtp_create()

static bool c_rtp_create	(	struct rohc_comp_ctxt *const	context,
		const struct net_pkt *const	packet
	)

static

Create a new RTP context and initialize it thanks to the given IP/UDP/RTP packet.

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

Parameters

context	The compression context
packet	The IP/UDP/RTP packet given to initialize the new context

Returns: true if successful, false otherwise

◆ c_rtp_decide_extension()

static rohc_ext_t c_rtp_decide_extension ( const struct rohc_comp_ctxt * context )

static

Decide what extension shall be used in the UO-1/UO-2 packet.

Extensions 0, 1 & 2 are IPv4 only because of the IP-ID.

Parameters

context The compression context

Returns: The extension code among ROHC_EXT_NO, ROHC_EXT_0, ROHC_EXT_1 and ROHC_EXT_3 if successful, ROHC_EXT_UNKNOWN otherwise

◆ c_rtp_decide_FO_packet()

static rohc_packet_t c_rtp_decide_FO_packet ( const struct rohc_comp_ctxt * context )

static

Decide which packet to send when in First Order (FO) state.

Packets that can be used are the IR-DYN and UO-2 packets.

See also: decide_packet

Parameters

context The compression context

Returns

The packet type among:

ROHC_PACKET_UOR_2_RTP
ROHC_PACKET_UOR_2_TS
ROHC_PACKET_UOR_2_ID
ROHC_PACKET_IR_DYN

◆ c_rtp_decide_SO_packet()

static rohc_packet_t c_rtp_decide_SO_packet ( const struct rohc_comp_ctxt * context )

static

Decide which packet to send when in Second Order (SO) state.

Packets that can be used are the UO-0, UO-1 and UO-2 (with or without extensions) packets.

See also: decide_packet

Parameters

context The compression context

Returns

The packet type among:

ROHC_PACKET_UO_0
ROHC_PACKET_UO_1_RTP
ROHC_PACKET_UO_1_TS
ROHC_PACKET_UO_1_ID
ROHC_PACKET_UOR_2_RTP
ROHC_PACKET_UOR_2_TS
ROHC_PACKET_UOR_2_ID
ROHC_PACKET_IR_DYN

◆ c_rtp_destroy()

static void c_rtp_destroy ( struct rohc_comp_ctxt *const context )

static

Destroy the 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

◆ c_rtp_encode()

static int c_rtp_encode	(	struct rohc_comp_ctxt *const	context,
		const struct net_pkt *const	uncomp_pkt,
		uint8_t *const	rohc_pkt,
		const size_t	rohc_pkt_max_len,
		rohc_packet_t *const	packet_type,
		size_t *const	payload_offset
	)

static

Encode an IP/UDP/RTP packet according to a pattern decided by several different factors.

Parameters

context	The compression context
uncomp_pkt	The uncompressed packet to encode
rohc_pkt	OUT: The ROHC packet
rohc_pkt_max_len	The maximum length of the ROHC packet
packet_type	OUT: The type of ROHC packet that is created
payload_offset	OUT: The offset for the payload in the IP packet

Returns: The length of the ROHC packet if successful, -1 otherwise

◆ c_rtp_get_next_sn()

static uint32_t c_rtp_get_next_sn	(	const struct rohc_comp_ctxt *const	context,
		const struct net_pkt *const	uncomp_pkt
	)

static

Determine the SN value for the next packet.

Profile SN is the 16-bit RTP SN.

Parameters

context	The compression context
uncomp_pkt	The uncompressed packet to encode

Returns: The SN

◆ rtp_changed_rtp_dynamic()

static int rtp_changed_rtp_dynamic	(	const struct rohc_comp_ctxt *const	context,
		const struct udphdr *const	udp,
		const struct rtphdr *const	rtp
	)

static

Check if the dynamic part of the UDP/RTP headers changed.

Parameters

context	The compression context
udp	The UDP header
rtp	The RTP header

Returns: The number of UDP/RTP fields that changed

◆ rtp_code_dynamic_rtp_part()

static size_t rtp_code_dynamic_rtp_part	(	const struct rohc_comp_ctxt *const	context,
		const uint8_t *const	next_header,
		uint8_t *const	dest,
		const size_t	counter
	)

static

Build the dynamic part of the UDP/RTP headers.

 Dynamic part of UDP header (5.7.7.5):

    +---+---+---+---+---+---+---+---+
 1  /           Checksum            /   2 octets
    +---+---+---+---+---+---+---+---+

 Dynamic part of RTP header (5.7.7.6):

    +---+---+---+---+---+---+---+---+
 2  |  V=2  | P | RX|      CC       |  (RX is NOT the RTP X bit)
    +---+---+---+---+---+---+---+---+
 3  | M |            PT             |
    +---+---+---+---+---+---+---+---+
 4  /      RTP Sequence Number      /  2 octets
    +---+---+---+---+---+---+---+---+
 5  /   RTP Timestamp (absolute)    /  4 octets
    +---+---+---+---+---+---+---+---+
 6  /      Generic CSRC list        /  variable length
    +---+---+---+---+---+---+---+---+
 7  : Reserved  | X |  Mode |TIS|TSS:  if RX = 1
    +---+---+---+---+---+---+---+---+
 8  :         TS_Stride             :  1-4 octets, if TSS = 1
    +---+---+---+---+---+---+---+---+
 9  :         Time_Stride           :  1-4 octets, if TIS = 1
    +---+---+---+---+---+---+---+---+

Parts 6 & 9 are not supported yet. The TIS flag in part 7 is not supported.

Parameters

context	The compression context
next_header	The UDP/RTP headers
dest	The rohc-packet-under-build buffer
counter	The current position in the rohc-packet-under-build buffer

Returns: The new position in the rohc-packet-under-build buffer

◆ rtp_code_static_rtp_part()

static size_t rtp_code_static_rtp_part	(	const struct rohc_comp_ctxt *const	context,
		const uint8_t *const	next_header,
		uint8_t *const	dest,
		const size_t	counter
	)

static

Build the static part of the UDP/RTP headers.

 Static part of UDP header (5.7.7.5):

    +---+---+---+---+---+---+---+---+
 1  /          Source Port          /   2 octets
    +---+---+---+---+---+---+---+---+
 2  /       Destination Port        /   2 octets
    +---+---+---+---+---+---+---+---+

 Static part of RTP header (5.7.7.6):

    +---+---+---+---+---+---+---+---+
 3  /             SSRC              /   4 octets
    +---+---+---+---+---+---+---+---+

Parts 1 & 2 are done by the udp_code_static_udp_part() function. Part 3 is done by this function.

Parameters

context	The compression context
next_header	The UDP/RTP headers
dest	The rohc-packet-under-build buffer
counter	The current position in the rohc-packet-under-build buffer

Returns: The new position in the rohc-packet-under-build buffer

See also: udp_code_static_udp_part

◆ rtp_decide_state()

static void rtp_decide_state ( struct rohc_comp_ctxt *const context )

static

Decide the state that should be used for the next packet compressed with the ROHC RTP profile.

The three states are:

Initialization and Refresh (IR),
First Order (FO),
Second Order (SO).

Parameters

context The compression context

◆ rtp_encode_uncomp_fields()

static bool rtp_encode_uncomp_fields	(	struct rohc_comp_ctxt *const	context,
		const struct net_pkt *const	uncomp_pkt
	)

static

Encode uncompressed RTP fields.

Handle the RTP TS field.

Parameters

context	The compression context
uncomp_pkt	The uncompressed packet to encode

Returns: true in case of success, false otherwise

Variable Documentation

◆ c_rtp_profile

const struct rohc_comp_profile c_rtp_profile

Initial value:

=
{
        .id             = ROHC_PROFILE_RTP, 
        .protocol       = ROHC_IPPROTO_UDP, 
        .create         = c_rtp_create,     
        .destroy        = c_rtp_destroy,
        .check_profile  = c_rtp_check_profile,
        .check_context  = c_rtp_check_context,
        .encode         = c_rtp_encode,
        .feedback       = rohc_comp_rfc3095_feedback,
}

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

Functions

Variables

Detailed Description

Function Documentation

◆ c_rtp_check_context()

◆ c_rtp_check_profile()

◆ c_rtp_create()

◆ c_rtp_decide_extension()

◆ c_rtp_decide_FO_packet()

◆ c_rtp_decide_SO_packet()

◆ c_rtp_destroy()

◆ c_rtp_encode()

◆ c_rtp_get_next_sn()

◆ rtp_changed_rtp_dynamic()

◆ rtp_code_dynamic_rtp_part()

◆ rtp_code_static_rtp_part()

◆ rtp_decide_state()

◆ rtp_encode_uncomp_fields()

Variable Documentation

◆ c_rtp_profile