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/*

 * Copyright (c) 2009 Lukas Mejdrech

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in the

 *   documentation and/or other materials provided with the distribution.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/** @addtogroup ip

 *  @{

 */

/** @file

 *  IP header and options definitions.

 *  Based on the RFC~791.

 */

#ifndef __NET_IP_HEADER_H__

#define __NET_IP_HEADER_H__

#include <byteorder.h>

#include <sys/types.h>

/** Returns the actual IP header length in bytes.

 *  @param[in] header The IP packet header.

 */

#define IP_HEADER_LENGTH( header )      (( header )->header_length * 4u )

/** Returns the IP header length.

 *  @param[in] length The IP header length in bytes.

 */

#define IP_COMPUTE_HEADER_LENGTH( length )      (( uint8_t ) (( length ) / 4u ))

/** Returns the actual IP packet total length.

 *  @param[in] header The IP packet header.

 */

#define IP_TOTAL_LENGTH( header )       ntohs(( header )->total_length )

/** Returns the actual IP packet data length.

 *  @param[in] header The IP packet header.

 */

#define IP_HEADER_DATA_LENGTH( header ) ( IP_TOTAL_LENGTH( header ) - IP_HEADER_LENGTH( header ))

/** Returns the IP packet header checksum.

 *  @param[in] header The IP packet header.

 */

#define IP_HEADER_CHECKSUM( header )    ( htons( ip_checksum(( uint8_t * )( header ), IP_HEADER_LENGTH( header ))))

/** Returns the fragment offest.

 *  @param[in] header The IP packet header.

 */

#define IP_FRAGMENT_OFFSET( header ) (((( header )->fragment_offset_high << 8 ) + ( header )->fragment_offset_low ) * 8u )

/** Returns the fragment offest high bits.

 *  @param[in] length The prefixed data total length.

 */

#define IP_COMPUTE_FRAGMENT_OFFSET_HIGH( length ) (((( length ) / 8u ) & 0x1F00 ) >> 8 )

/** Returns the fragment offest low bits.

 *  @param[in] length The prefixed data total length.

 */

#define IP_COMPUTE_FRAGMENT_OFFSET_LOW( length ) ((( length ) / 8u ) & 0xFF )

/** Type definition of the internet header.

 *  @see ip_header

 */

typedef struct ip_header    ip_header_t;

/** Type definition of the internet header pointer.

 *  @see ip_header

 */

typedef ip_header_t *       ip_header_ref;

/** Internet header.

 *  The variable options should be included after the header itself and indicated by the increased header length value.

 */

struct ip_header{

#ifdef ARCH_IS_BIG_ENDIAN

    /** The Version field indicates the format of the internet header.

     */

    uint8_t     version:4;

    /** Internet Header Length is the length of the internet header in 32~bit words, and thus points to the beginning of the data.

     *  Note that the minimum value for a~correct header is~5.

     */

    uint8_t     header_length:4;

#else

    /** Internet Header Length is the length of the internet header in 32~bit words, and thus points to the beginning of the data.

     *  Note that the minimum value for a~correct header is~5.

     */

    uint8_t     header_length:4;

    /** The Version field indicates the format of the internet header.

     */

    uint8_t     version:4;

#endif

    /** The Type of Service provides an indication of the abstract parameters of the quality of service desired.

     *  These parameters are to be used to guide the selection of the actual service parameters when transmitting a~datagram through a~particular network.

     *  Several networks offer service precedence, which somehow treats high precedence traffic as more important than other traffic (generally by accepting only traffic above a~certain precedence at time of high load).

     *  The major choice is a~three way tradeoff between low-delay, high-reliability, and high-throughput.

     */

    uint8_t     tos;

    /** Total Length is the length of the datagram, measured in octets, including internet header and data.

     *  This field allows the length of a~datagram to be up to 65,535~octets.

     */

    uint16_t    total_length;

    /** An identifying value assigned by the sender to aid in assembling the fragments of a~datagram.

     */

    uint16_t    identification;

#ifdef ARCH_IS_BIG_ENDIAN

    /** Various control flags.

     */

    uint8_t flags:3;

    /** This field indicates where in the datagram this fragment belongs.

     *  High bits.

     */

    uint8_t fragment_offset_high:5;

#else

    /** This field indicates where in the datagram this fragment belongs.

     *  High bits.

     */

    uint8_t fragment_offset_high:5;

    /** Various control flags.

     */

    uint8_t flags:3;

#endif

    /** This field indicates where in the datagram this fragment belongs.

     *  Low bits.

     */

    uint8_t fragment_offset_low;

    /** This field indicates the maximum time the datagram is allowed to remain in the internet system.

     *  If this field contains the value zero, then the datagram must be destroyed.

     *  This field is modified in internet header processing.

     *  The time is measured in units of seconds, but since every module that processes a~datagram must decrease the TTL by at least one even if it process the datagram in less than a~second, the TTL must be thought of only as an upper bound on the time a~datagram may exist.

     *  The intention is to cause undeliverable datagrams to be discarded, and to bound the maximum datagram lifetime.

     */

    uint8_t     ttl;

    /** This field indicates the next level protocol used in the data portion of the internet datagram.

     */

    uint8_t     protocol;

    /** A checksum of the header only.

     *  Since some header fields change (e.g., time to live), this is recomputed and verified at each point that the internet header is processed.

     *  The checksum algorithm is: The checksum field is the 16~bit one's complement of the one's complement sum of all 16~bit words in the header.

     *  For purposes of computing the checksum, the value of the checksum field is zero.

     */

    uint16_t    header_checksum;

    /** The source address.

     */

    uint32_t    source_address;

    /** The destination address.

     */

    uint32_t    destination_address;

} __attribute__ ((packed));

/** Type definition of the internet option header.

 *  @see ip_header

 */

typedef struct ip_option    ip_option_t;

/** Type definition of the internet option header pointer.

 *  @see ip_header

 */

typedef ip_option_t *       ip_option_ref;

/** Internet option header.

 *  Only type field is always valid.

 *  Other fields' validity depends on the option type.

 */

struct ip_option{

    /** A single octet of option-type.

     */

    uint8_t     type;

    /** An option length octet.

     */

    uint8_t     length;

    /** A~pointer.

     */

    uint8_t     pointer;

#ifdef ARCH_IS_BIG_ENDIAN

    /** The number of IP modules that cannot register timestamps due to lack of space.

     */

    uint8_t overflow:4;

    /** Various internet timestamp control flags.

     */

    uint8_t flags:4;

#else

    /** Various internet timestamp control flags.

     */

    uint8_t flags:4;

    /** The number of IP modules that cannot register timestamps due to lack of space.

     */

    uint8_t overflow:4;

#endif

} __attribute__ ((packed));

/** @name IP flags definitions

 */

/*@{*/

/** Fragment flag field shift.

 */

#define IPFLAG_FRAGMENT_SHIFT       1

/** Fragmented flag field shift.

 */

#define IPFLAG_FRAGMENTED_SHIFT     0

/** May fragment flag value.

 *  Allows the packet fragmentation.

 */

#define IPFLAG_MAY_FRAGMENT         ( 0x0 << IPFLAG_FRAGMENT_SHIFT )

/** Don't fragment flag value.

 *  Permits the packet fragmentation.

 */

#define IPFLAG_DONT_FRAGMENT        ( 0x1 << IPFLAG_FRAGMENT_SHIFT )

/** Last fragment flag value.

 *  Indicates the last packet fragment.

 */

#define IPFLAG_LAST_FRAGMENT        ( 0x0 << IPFLAG_FRAGMENTED_SHIFT )

/** More fragments flag value.

 *  Indicates that more packet fragments follow.

 */

#define IPFLAG_MORE_FRAGMENTS       ( 0x1 << IPFLAG_FRAGMENTED_SHIFT )

/*@}*/

/** Type definition of the internet version 4 pseudo header.

 *  @see ipv4_pseudo_header

 */

typedef struct ipv4_pseudo_header   ipv4_pseudo_header_t;

/** Type definition of the internet version 4 pseudo header pointer.

 *  @see ipv4_pseudo_header

 */

typedef ipv4_pseudo_header_t *      ipv4_pseudo_header_ref;

/** Internet version 4 pseudo header.

 */

struct ipv4_pseudo_header{

    /** The source address.

     */

    uint32_t    source_address;

    /** The destination address.

     */

    uint32_t    destination_address;

    /** Reserved byte.

     *  Must be zero.

     */

    uint8_t     reserved;

    /** This field indicates the next level protocol used in the data portion of the internet datagram.

     */

    uint8_t     protocol;

    /** Data length is the length of the datagram, measured in octets.

     */

    uint16_t    data_length;

} __attribute__ ((packed));

#endif

/** @}

 */