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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.
 *  Names according to the linux src/include/linux/ip.h header file.
 */

#ifndef __NET_IP_HEADER_H__
#define __NET_IP_HEADER_H__

#include <byteorder.h>
#include <sys/types.h>

/** 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     ihl: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     ihl: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.
     *  @see 
     */
    uint16_t    flags:3;
    /** This field indicates where in the datagram this fragment belongs.
     */
    uint16_t    fragment_offset:3;
#else
    /** This field indicates where in the datagram this fragment belongs.
     */
    uint16_t    fragment_offset:13;
    /** Various control flags.
     */
    uint16_t    flags:3;
#endif
    /** 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 )

/*@}*/

/*
#define IPOPT_OPTVAL 0
#define IPOPT_OLEN   1
#define IPOPT_OFFSET 2
#define IPOPT_MINOFF 4
#define MAX_IPOPTLEN 40
*/

/** 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;
    /** Zero byte.
     */
    uint8_t     zero;
    /** 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

/** @}
 */