rohc_comp_rfc3095.h

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/*
 * Copyright 2010,2011,2012,2013,2014 Didier Barvaux
 * Copyright 2007,2008 Thales Alenia Space
 * Copyright 2007,2008,2009,2010,2012,2014 Viveris Technologies
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

/**
 * @file   rohc_comp_rfc3095.h
 * @brief  Generic framework for RFC3095-based compression profiles such as
 *         IP-only, UDP, UDP-Lite, ESP, and RTP profiles.
 * @author Didier Barvaux <didier.barvaux@toulouse.viveris.com>
 * @author Didier Barvaux <didier@barvaux.org>
 */

#ifndef ROHC_COMP_RFC3095_H
#define ROHC_COMP_RFC3095_H

#include "rohc_comp_internals.h"
#include "rohc_packets.h"
#include "schemes/comp_list.h"
#include "ip.h"
#include "crc.h"

#include <stdlib.h>


/**
 * @brief Store information about an IPv4 header between the different
 *        compressions of IP packets.
 *
 * Defines an object that contains counters, flags and structures related to an
 * IPv4 header and that need to be saved between the different compressions of
 * packets. A compression context owns objects like this for the two first
 * IPv4 headers.
 */
struct ipv4_header_info
{
        /// A window to store the IP-ID
        struct c_wlsb *ip_id_window;

        /// The previous IP header
        struct ipv4_hdr old_ip;

        /// The number of times the DF field was added to the compressed header
        size_t df_count;
        /// @brief The number of times the IP-ID is specified as random in the
        ///        compressed header
        size_t rnd_count;
        /// @brief The number of times the IP-ID is specified as coded in Network
        ///        Byte Order (NBO) in the compressed header
        size_t nbo_count;
        /// @brief The number of times the IP-ID is specified as static in the
        ///        compressed header
        size_t sid_count;

        /// Whether the IP-ID is considered as random or not
        int rnd;
        /// Whether the IP-ID is considered as coded in NBO or not
        int nbo;
        /// Whether the IP-ID is considered as static or not
        int sid;
        /// @brief Whether the IP-ID of the previous IP header was considered as
        ///        random or not
        int old_rnd;
        /// @brief Whether the IP-ID of the previous IP header was considered as
        ///        coded in NBO or not
        int old_nbo;
        /// @brief Whether the IP-ID of the previous IP header was considered as
        ///        static or not
        int old_sid;

        /// The delta between the IP-ID and the current Sequence Number (SN)
        /// (overflow over 16 bits is expected when SN > IP-ID)
        uint16_t id_delta;
};


/**
 * @brief Store information about an IPv6 header between the different
 *        compressions of IP packets.
 *
 * Defines an object that contains counters, flags and structures related to an
 * IPv6 header and that need to be saved between the different compressions of
 * packets. A compression context owns objects like this for the two first
 * IPv6 headers.
 */
struct ipv6_header_info
{
        /// The previous IPv6 header
        struct ipv6_hdr old_ip;
        /// The extension compressor
        struct list_comp ext_comp;
};


/**
 * @brief Store information about an IP (IPv4 or IPv6) header between the
 *        different compressions of IP packets.
 */
struct ip_header_info
{
        ip_version version;            ///< The version of the IP header

        /// The number of times the TOS/TC field was added to the compressed header
        size_t tos_count;
        /// The number of times the TTL/HL field was added to the compressed header
        size_t ttl_count;
        /// @brief The number of times the Protocol/Next Header field was added to
        ///        the compressed header
        size_t protocol_count;

        /** Whether the old_* members of the struct and in its children are
         *  initialized or not */
        bool is_first_header;

        union
        {
                struct ipv4_header_info v4; ///< The IPv4-specific header info
                struct ipv6_header_info v6; ///< The IPv6-specific header info
        } info;                        ///< The version specific header info
};


/**
 * @brief Structure that contains variables that are used during one single
 *        compression of packet.
 *
 * Structure that contains variables that are temporary, i.e. variables that
 * will only be used for the compression of the current packet. These variables
 * must be reinitialized every time a new packet arrive.
 *
 * @see c_init_tmp_variables
 */
struct generic_tmp_vars
{
        /// The number of fields that changed in the outer IP header
        unsigned short changed_fields;
        /// The number of fields that changed in the inner IP header
        unsigned short changed_fields2;
        /// The number of static fields that changed in the two IP headers
        int send_static;
        /// The number of dynamic fields that changed in the two IP headers
        int send_dynamic;

        /// The number of bits needed to encode the Sequence Number (SN)
        size_t nr_sn_bits_less_equal_than_4;
        /// The number of bits needed to encode the Sequence Number (SN)
        size_t nr_sn_bits_more_than_4;

        /// The number of bits needed to encode the IP-ID of the outer IP header
        size_t nr_ip_id_bits;
        /// The number of bits needed to encode the IP-ID of the inner IP header
        size_t nr_ip_id_bits2;

        /// The type of packet the compressor must send: IR, IR-DYN, UO*
        rohc_packet_t packet_type;
};


/**
 * @brief The generic decompression context for RFC3095-based profiles
 *
 * The object defines the generic context that manages IP(/nextheader) and
 * IP/IP(/nextheader) packets. nextheader is managed by the profile-specific
 * part of the context.
 */
struct rohc_comp_rfc3095_ctxt
{
        /// The Sequence Number (SN), may be 16-bit or 32-bit long
        uint32_t sn;
        /// A window used to encode the SN
        struct c_wlsb *sn_window;

        /** The number of IP headers */
        size_t ip_hdr_nr;
        /// Information about the outer IP header
        struct ip_header_info outer_ip_flags;
        /// Information about the inner IP header
        struct ip_header_info inner_ip_flags;

        /// Temporary variables that are used during one single compression of packet
        struct generic_tmp_vars tmp;

        /* below are some information and handlers to manage the next header
         * (if any) located just after the IP headers (1 or 2 IP headers) */

        /// The protocol number registered by IANA for the next header protocol
        unsigned int next_header_proto;
        /// The length of the next header
        unsigned int next_header_len;

        /** The handler for encoding profile-specific uncompressed header fields */
        bool (*encode_uncomp_fields)(struct rohc_comp_ctxt *const context,
                                     const struct net_pkt *const uncomp_pkt)
                __attribute__((warn_unused_result, nonnull(1, 2)));

        /// @brief The handler used to decide the state that should be used for the
        ///        next packet
        void (*decide_state)(struct rohc_comp_ctxt *const context);
        /** @brief The handler used to decide which packet to send in FO state */
        rohc_packet_t (*decide_FO_packet)(const struct rohc_comp_ctxt *context);
        /** @brief The handler used to decide which packet to send in SO state */
        rohc_packet_t (*decide_SO_packet)(const struct rohc_comp_ctxt *context);
        /** The handler used to decide which extension to send */
        rohc_ext_t (*decide_extension)(const struct rohc_comp_ctxt *context);

        /// The handler used to initialize some data just before the IR packet build
        void (*init_at_IR)(struct rohc_comp_ctxt *const context,
                           const uint8_t *const next_header);

        /** Determine the next SN value */
        uint32_t (*get_next_sn)(const struct rohc_comp_ctxt *const context,
                                const struct net_pkt *const uncomp_pkt)
                __attribute__((warn_unused_result, nonnull(1, 2)));

        /// @brief The handler used to add the static part of the next header to the
        ///        ROHC packet
        size_t (*code_static_part)(const struct rohc_comp_ctxt *const context,
                                   const uint8_t *const next_header,
                                   uint8_t *const dest,
                                   const size_t counter)
                __attribute__((warn_unused_result, nonnull(1, 2, 3)));

        /// @brief The handler used to add the dynamic part of the next header to the
        ///        ROHC pachet
        size_t (*code_dynamic_part)(const struct rohc_comp_ctxt *const context,
                                    const uint8_t *const next_header,
                                    uint8_t *const dest,
                                    const size_t counter)
                __attribute__((warn_unused_result, nonnull(1, 2, 3)));

        /// @brief The handler used to add the IR/IR-DYN remainder header to the
        ///        ROHC pachet
        int (*code_ir_remainder)(const struct rohc_comp_ctxt *const context,
                                 uint8_t *const dest,
                                 const size_t dest_max_len,
                                 const size_t counter)
                __attribute__((warn_unused_result, nonnull(1, 2)));

        /// @brief The handler used to add an additional header in the head of the
        ///        UO-0, UO-1 and UO-2 packets
        size_t (*code_UO_packet_head)(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)
                __attribute__((warn_unused_result, nonnull(1,2, 3, 5)));

        /// @brief The handler used to add an additional header in the tail of the
        ///        UO-0, UO-1 and UO-2 packets
        size_t (*code_uo_remainder)(const struct rohc_comp_ctxt *const context,
                                    const uint8_t *const next_header,
                                    uint8_t *const dest,
                                    const size_t counter)
                __attribute__((warn_unused_result, nonnull(1, 2, 3)));

        /// @brief The handler used to compute the CRC-STATIC value
        uint8_t (*compute_crc_static)(const uint8_t *const ip,
                                      const uint8_t *const ip2,
                                      const uint8_t *const next_header,
                                      const rohc_crc_type_t crc_type,
                                      const uint8_t init_val,
                                      const uint8_t *const crc_table)
                __attribute__((nonnull(1, 3, 6), warn_unused_result));

        /// @brief The handler used to compute the CRC-DYNAMIC value
        uint8_t (*compute_crc_dynamic)(const uint8_t *const ip,
                                       const uint8_t *const ip2,
                                       const uint8_t *const next_header,
                                       const rohc_crc_type_t crc_type,
                                       const uint8_t init_val,
                                       const uint8_t *const crc_table)
                __attribute__((nonnull(1, 3, 6), warn_unused_result));

        /// Profile-specific data
        void *specific;
};


/*
 * Function prototypes.
 */

bool rohc_comp_rfc3095_create(struct rohc_comp_ctxt *const context,
                              const rohc_lsb_shift_t sn_shift,
                              const struct net_pkt *const packet)
        __attribute__((warn_unused_result, nonnull(1, 3)));

void rohc_comp_rfc3095_destroy(struct rohc_comp_ctxt *const context)
        __attribute__((nonnull(1)));

bool rohc_comp_rfc3095_check_profile(const struct rohc_comp *const comp,
                                     const struct net_pkt *const packet)
        __attribute__((warn_unused_result, nonnull(1, 2)));

rohc_ext_t decide_extension(const struct rohc_comp_ctxt *const context)
        __attribute__((warn_unused_result, nonnull(1)));

int rohc_comp_rfc3095_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)
        __attribute__((warn_unused_result, nonnull(1, 2, 3, 5, 6)));

bool rohc_comp_rfc3095_feedback(struct rohc_comp_ctxt *const context,
                                const enum rohc_feedback_type feedback_type,
                                const uint8_t *const packet,
                                const size_t packet_len,
                                const uint8_t *const feedback_data,
                                const size_t feedback_data_len)
        __attribute__((warn_unused_result, nonnull(1, 3, 5)));

void rohc_comp_rfc3095_decide_state(struct rohc_comp_ctxt *const context)
        __attribute__((nonnull(1)));

void rohc_get_ipid_bits(const struct rohc_comp_ctxt *const context,
                        size_t *const nr_innermost_bits,
                        size_t *const nr_outermost_bits)
        __attribute__((nonnull(1, 2, 3)));

bool rohc_comp_rfc3095_is_sn_possible(const struct rohc_comp_rfc3095_ctxt *const rfc3095_ctxt,
                                      const size_t bits_nr,
                                      const size_t add_bits_nr)
        __attribute__((warn_unused_result, nonnull(1), pure));


/**
 * @brief Does the outer IP header require to transmit no non-random IP-ID bit?
 *
 * @param ctxt  The generic decompression context
 * @return      true if no required outer IP-ID bit shall be transmitted,
 *              false otherwise
 */
static inline bool no_outer_ip_id_bits_required(const struct rohc_comp_rfc3095_ctxt *const ctxt)
{
        return (ctxt->outer_ip_flags.version != IPV4 ||
                ctxt->outer_ip_flags.info.v4.rnd == 1 ||
                ctxt->tmp.nr_ip_id_bits == 0);
}


/**
 * @brief May the outer IP header transmit the required non-random IP-ID bits?
 *
 * @param ctxt               The generic decompression context
 * @param max_ip_id_bits_nr  The maximum number of IP-ID bits that may be transmitted
 * @return                   true if the required IP-ID bits may be transmitted,
 *                           false otherwise
 */
static inline bool is_outer_ip_id_bits_possible(const struct rohc_comp_rfc3095_ctxt *const ctxt,
                                                const size_t max_ip_id_bits_nr)
{
        return (ctxt->outer_ip_flags.version == IPV4 &&
                ctxt->outer_ip_flags.info.v4.rnd != 1 &&
                ctxt->tmp.nr_ip_id_bits <= max_ip_id_bits_nr);
}


/**
 * @brief Does the inner IP header require to transmit no non-random IP-ID bit?
 *
 * @param ctxt  The generic decompression context
 * @return      true if no required inner IP-ID bit shall be transmitted,
 *              false otherwise
 */
static inline bool no_inner_ip_id_bits_required(const struct rohc_comp_rfc3095_ctxt *const ctxt)
{
        return (ctxt->inner_ip_flags.version != IPV4 ||
                ctxt->inner_ip_flags.info.v4.rnd == 1 ||
                ctxt->tmp.nr_ip_id_bits2 == 0);
}


/**
 * @brief May the inner IP header transmit the required non-random IP-ID bits?
 *
 * @param ctxt               The generic decompression context
 * @param max_ip_id_bits_nr  The maximum number of IP-ID bits that may be transmitted
 * @return                   true if the required IP-ID bits may be transmitted,
 *                           false otherwise
 */
static inline bool is_inner_ip_id_bits_possible(const struct rohc_comp_rfc3095_ctxt *const ctxt,
                                                const size_t max_ip_id_bits_nr)
{
        return (ctxt->inner_ip_flags.version == IPV4 &&
                ctxt->inner_ip_flags.info.v4.rnd != 1 &&
                ctxt->tmp.nr_ip_id_bits2 <= max_ip_id_bits_nr);
}


/**
 * @brief How many IP headers are IPv4 headers with non-random IP-IDs ?
 *
 * @param ctxt  The generic decompression context
 * @return      The number of IPv4 headers with non-random IP-ID fields
 */
static inline size_t get_nr_ipv4_non_rnd(const struct rohc_comp_rfc3095_ctxt *const ctxt)
{
        size_t nr_ipv4_non_rnd = 0;

        /* outer IP header */
        if(ctxt->outer_ip_flags.version == IPV4 && ctxt->outer_ip_flags.info.v4.rnd != 1)
        {
                nr_ipv4_non_rnd++;
        }

        /* optional inner IP header */
        if(ctxt->ip_hdr_nr >= 1 &&
           ctxt->inner_ip_flags.version == IPV4 &&
           ctxt->inner_ip_flags.info.v4.rnd != 1)
        {
                nr_ipv4_non_rnd++;
        }

        return nr_ipv4_non_rnd;
}


/**
 * @brief How many IP headers are IPv4 headers with non-random IP-IDs and some
 *        bits to transmit ?
 *
 * @param ctxt  The generic decompression context
 * @return      The number of IPv4 headers with non-random IP-ID fields and some
 *              bits to transmit
 */
static inline size_t get_nr_ipv4_non_rnd_with_bits(const struct rohc_comp_rfc3095_ctxt *const ctxt)
{
        size_t nr_ipv4_non_rnd_with_bits = 0;

        /* outer IP header */
        if(ctxt->outer_ip_flags.version == IPV4 &&
           ctxt->outer_ip_flags.info.v4.rnd != 1 &&
           ctxt->tmp.nr_ip_id_bits > 0)
        {
                nr_ipv4_non_rnd_with_bits++;
        }

        /* optional inner IP header */
        if(ctxt->ip_hdr_nr >= 1 &&
           ctxt->inner_ip_flags.version == IPV4 &&
           ctxt->inner_ip_flags.info.v4.rnd != 1 &&
           ctxt->tmp.nr_ip_id_bits2 > 0)
        {
                nr_ipv4_non_rnd_with_bits++;
        }

        return nr_ipv4_non_rnd_with_bits;
}


#endif