c_udp_lite.c File Reference

ROHC compression context for the UDP-Lite profile. More...

#include "c_udp.h"
#include "c_ip.h"
#include "rohc_traces_internal.h"
#include "rohc_packets.h"
#include "rohc_utils.h"
#include "crc.h"
#include "rohc_comp_rfc3095.h"
#include "protocols/udp_lite.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
Include dependency graph for c_udp_lite.c:

Data Structures

struct  udp_lite_tmp_vars
 Define the UDP-Lite-specific temporary variables in the profile compression context. More...
struct  sc_udp_lite_context
 Define the UDP-Lite part of the profile compression context. More...

Defines

#define MAX_LITE_COUNT   2
 The maximal number of times the checksum coverage dit not change or may be inferred.

Functions

static bool c_udp_lite_create (struct rohc_comp_ctxt *const context, const struct net_pkt *const packet)
 Create a new UDP-Lite context and initialize it thanks to the given IP/UDP-Lite packet.
static bool c_udp_lite_check_profile (const struct rohc_comp *const comp, const struct net_pkt *const packet)
 Check if the given packet corresponds to the UDP-Lite profile.
static bool c_udp_lite_check_context (const struct rohc_comp_ctxt *const context, const struct net_pkt *const packet)
 Check if the IP/UDP-Lite packet belongs to the context.
static int c_udp_lite_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-lite packet according to a pattern decided by several different factors.
static size_t udp_lite_code_dynamic_udplite_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-Lite header.
static size_t udp_lite_build_cce_packet (const struct rohc_comp_ctxt *const context, const uint8_t *const next_header, uint8_t *const dest, const size_t counter, size_t *const first_position)
 Build the Checksum Coverage Extension (CCE) packet.
static bool udp_lite_send_cce_packet (const struct rohc_comp_ctxt *const context, const struct udphdr *const udp_lite)
 Check whether a Checksum Coverage Extension (CCE) packet must be sent or not in order to compress the given UDP-Lite header.
static size_t udp_lite_code_uo_remainder (const struct rohc_comp_ctxt *const context, const uint8_t *const next_header, uint8_t *const dest, const size_t counter)
 Build UDP-Lite-related fields in the tail of the UO packets.
static void udp_lite_init_cc (struct rohc_comp_ctxt *const context, const uint8_t *const next_header)
 Initialize checksum coverage in the compression context with the given UDP-Lite header.

Variables

struct rohc_comp_profile c_udp_lite_profile
 Define the compression part of the UDP-Lite profile as described in the RFC 4019.

Detailed Description

ROHC compression context for the UDP-Lite profile.

Author:
Didier Barvaux <didier.barvaux@toulouse.viveris.com>
Didier Barvaux <didier@barvaux.org>

Define Documentation

#define MAX_LITE_COUNT   2

The maximal number of times the checksum coverage dit not change or may be inferred.

Function Documentation

static bool c_udp_lite_check_context ( const struct rohc_comp_ctxt *const   context,
const struct net_pkt *const   packet 
) [static]

Check if the IP/UDP-Lite 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-Lite
  • the source and destination ports of the UDP-Lite header must match the ones in the context
  • IPv6 only: the Flow Label of the two IP headers must match the ones the context

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-Lite packet to check
Returns:
true if the IP/UDP-Lite packet belongs to the context, false if it does not belong to the context
static bool c_udp_lite_check_profile ( const struct rohc_comp *const   comp,
const struct net_pkt *const   packet 
) [static]

Check if the given packet corresponds to the UDP-Lite profile.

Conditions are:

  • the transport protocol is UDP-Lite
  • 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
See also:
rohc_comp_rfc3095_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
static bool c_udp_lite_create ( struct rohc_comp_ctxt *const   context,
const struct net_pkt *const   packet 
) [static]

Create a new UDP-Lite context and initialize it thanks to the given IP/UDP-Lite 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-Lite packet given to initialize the new context
Returns:
true if successful, false otherwise
static int c_udp_lite_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-lite 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
static size_t udp_lite_build_cce_packet ( const struct rohc_comp_ctxt *const   context,
const uint8_t *const   next_header,
uint8_t *const   dest,
const size_t  counter,
size_t *const   first_position 
) [static]

Build the Checksum Coverage Extension (CCE) packet.

The Checksum Coverage Extension is located at the very start of the UO packet (part 2 in the following figure).


     0   1   2   3   4   5   6   7
     --- --- --- --- --- --- --- ---
 1  :         Add-CID octet         :  If for small CIDs and CID 1 - 15
    +---+---+---+---+---+---+---+---+
 2  | 1   1   1   1   1   0   F | K |  Outer packet type identifier
    +---+---+---+---+---+---+---+---+
    :                               :
 3  /   0, 1, or 2 octets of CID    /  1 - 2 octets if large CIDs
    :                               :
    +---+---+---+---+---+---+---+---+
    :                               :
 4  /   UO-0, UO-1 or UO-2 packet   /
    :                               :
    +---+---+---+---+---+---+---+---+

Parts 1, 3 and 4 are coded by the generic code_UO0_packet, code_UO1_packet and code_UO2_packet functions. These functions call the code_UO_packet_head function which in case of UDP-Lite profile is the udp_lite_build_cce_packet function.

When the udp_lite_build_cce_packet is called, the parameter first_position points on the part 2 and the parameter counter points on the beginning of the part 4.

Parameters:
context The compression context
next_header The UDP header
dest The rohc-packet-under-build buffer
counter The current position in the rohc-packet-under-build buffer
first_position The position to place the first byte of packet
Returns:
The new position in the rohc-packet-under-build buffer
static size_t udp_lite_code_dynamic_udplite_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-Lite header. 


 Dynamic part of UDP-Lite header (5.2.1 of RFC 4019):

    +---+---+---+---+---+---+---+---+
 1  /       Checksum Coverage       /   2 octets
    +---+---+---+---+---+---+---+---+
 2  /           Checksum            /   2 octets
    +---+---+---+---+---+---+---+---+
Parameters:
context The compression context
next_header The UDP-Lite header
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
static size_t udp_lite_code_uo_remainder ( const struct rohc_comp_ctxt *const   context,
const uint8_t *const   next_header,
uint8_t *const   dest,
const size_t  counter 
) [static]

Build UDP-Lite-related fields in the tail of the UO packets. 


     --- --- --- --- --- --- --- ---
    :                               :  2 octets,
 1  +  UDP-Lite Checksum Coverage   +  if context(CFP) = 1 or
    :                               :  if packet type = CCE
     --- --- --- --- --- --- --- ---
    :                               :
 2  +       UDP-Lite Checksum       +  2 octets
    :                               :
     --- --- --- --- --- --- --- ---
Parameters:
context The compression context
next_header The UDP-Lite header
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
static void udp_lite_init_cc ( struct rohc_comp_ctxt *const   context,
const uint8_t *const   next_header 
) [static]

Initialize checksum coverage in the compression context with the given UDP-Lite header.

Parameters:
context The compression context
next_header The UDP-Lite header
static bool udp_lite_send_cce_packet ( const struct rohc_comp_ctxt *const   context,
const struct udphdr *const   udp_lite 
) [static]

Check whether a Checksum Coverage Extension (CCE) packet must be sent or not in order to compress the given UDP-Lite header.

The function also updates the FK variable stored in the UDP-Lite context.

Parameters:
context The compression context
udp_lite The UDP-Lite header
Returns:
true if a CCE packet must be sent, false if not

Variable Documentation

struct rohc_comp_profile c_udp_lite_profile
Initial value:
{
        .id             = ROHC_PROFILE_UDPLITE, 
        .protocol       = ROHC_IPPROTO_UDPLITE, 
        .create         = c_udp_lite_create,    
        .destroy        = rohc_comp_rfc3095_destroy,
        .check_profile  = c_udp_lite_check_profile,
        .check_context  = c_udp_lite_check_context,
        .encode         = c_udp_lite_encode,
        .reinit_context = rohc_comp_reinit_context,
        .feedback       = rohc_comp_rfc3095_feedback,
}

Define the compression part of the UDP-Lite profile as described in the RFC 4019.

Generated on 4 Jul 2018 for ROHC compression/decompression library by  doxygen 1.6.1