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/*
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 * Copyright (c) 2009 Lukas Mejdrech
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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/** @addtogroup ip
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 *  @{
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 */
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/** @file
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 *  IP header and options definitions.
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 *  Based on the RFC~791.
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 */
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#ifndef __NET_IP_HEADER_H__
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#define __NET_IP_HEADER_H__
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#include <byteorder.h>
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#include <sys/types.h>
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/** Returns the actual IP header length.
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 *  @param header The IP packet header. Input parameter.
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 */
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#define IP_HEADER_LENGTH( header )      (( header )->header_length * 4u )
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/** Returns the actual IP header length.
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 *  @param header The IP packet header. Input parameter.
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 */
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#define IP_COMPUTE_HEADER_LENGTH( length )      (( uint8_t ) (( length ) / 4u ))
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/** Returns the actual IP packet total length.
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 *  @param header The IP packet header. Input parameter.
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 */
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#define IP_TOTAL_LENGTH( header )       ntohs(( header )->total_length )
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/** Returns the actual IP packet data length.
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 *  @param header The IP packet header. Input parameter.
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 */
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#define IP_HEADER_DATA_LENGTH( header ) ( IP_TOTAL_LENGTH( header ) - IP_HEADER_LENGTH( header ))
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/** Returns the IP packet header checksum.
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 *  @param header The IP packet header. Input parameter.
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 */
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#define IP_HEADER_CHECKSUM( header )    ( htons( ip_checksum(( uint8_t * )( header ), IP_HEADER_LENGTH( header ))))
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/** Returns the fragment offest.
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 *  @param header The IP packet header. Input parameter.
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 */
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#define IP_FRAGMENT_OFFSET( header ) (((( header )->fragment_offset_high << 8 ) + ( header )->fragment_offset_low ) * 8u )
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/** Returns the fragment offest high bits.
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 *  @param length The prefixed data total length. Input parameter.
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 */
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#define IP_COMPUTE_FRAGMENT_OFFSET_HIGH( length ) (((( length ) / 8u ) & 0x1F00 ) >> 8 )
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/** Returns the fragment offest low bits.
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 *  @param length The prefixed data total length. Input parameter.
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 */
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#define IP_COMPUTE_FRAGMENT_OFFSET_LOW( length ) ((( length ) / 8u ) & 0xFF )
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/** Type definition of the internet header.
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 *  @see ip_header
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 */
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typedef struct ip_header    ip_header_t;
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/** Type definition of the internet header pointer.
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 *  @see ip_header
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 */
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typedef ip_header_t *       ip_header_ref;
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/** Internet header.
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 *  The variable options should be included after the header itself and indicated by the increased header length value.
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 */
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struct ip_header{
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#ifdef ARCH_IS_BIG_ENDIAN
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    /** The Version field indicates the format of the internet header.
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     */
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    uint8_t     version:4;
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    /** Internet Header Length is the length of the internet header in 32~bit words, and thus points to the beginning of the data.
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     *  Note that the minimum value for a~correct header is~5.
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     */
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    uint8_t     header_length:4;
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#else
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    /** Internet Header Length is the length of the internet header in 32~bit words, and thus points to the beginning of the data.
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     *  Note that the minimum value for a~correct header is~5.
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     */
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    uint8_t     header_length:4;
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    /** The Version field indicates the format of the internet header.
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     */
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    uint8_t     version:4;
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#endif
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    /** The Type of Service provides an indication of the abstract parameters of the quality of service desired.
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     *  These parameters are to be used to guide the selection of the actual service parameters when transmitting a~datagram through a~particular network.
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     *  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).
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     *  The major choice is a~three way tradeoff between low-delay, high-reliability, and high-throughput.
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     */
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    uint8_t     tos;
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    /** Total Length is the length of the datagram, measured in octets, including internet header and data.
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     *  This field allows the length of a~datagram to be up to 65,535~octets.
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     */
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    uint16_t    total_length;
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    /** An identifying value assigned by the sender to aid in assembling the fragments of a~datagram.
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     */
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    uint16_t    identification;
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#ifdef ARCH_IS_BIG_ENDIAN
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    /** Various control flags.
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     */
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    uint8_t flags:3;
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    /** This field indicates where in the datagram this fragment belongs.
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     *  High bits.
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     */
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    uint8_t fragment_offset_high:5;
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#else
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    /** This field indicates where in the datagram this fragment belongs.
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     *  High bits.
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     */
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    uint8_t fragment_offset_high:5;
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    /** Various control flags.
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     */
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    uint8_t flags:3;
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#endif
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    /** This field indicates where in the datagram this fragment belongs.
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     *  Low bits.
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     */
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    uint8_t fragment_offset_low;
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    /** This field indicates the maximum time the datagram is allowed to remain in the internet system.
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     *  If this field contains the value zero, then the datagram must be destroyed.
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     *  This field is modified in internet header processing.
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     *  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.
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     *  The intention is to cause undeliverable datagrams to be discarded, and to bound the maximum datagram lifetime.
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     */
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    uint8_t     ttl;
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    /** This field indicates the next level protocol used in the data portion of the internet datagram.
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     */
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    uint8_t     protocol;
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    /** A checksum of the header only.
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     *  Since some header fields change (e.g., time to live), this is recomputed and verified at each point that the internet header is processed.
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     *  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.
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     *  For purposes of computing the checksum, the value of the checksum field is zero.
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     */
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    uint16_t    header_checksum;
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    /** The source address.
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     */
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    uint32_t    source_address;
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    /** The destination address.
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     */
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    uint32_t    destination_address;
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} __attribute__ ((packed));
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/** Type definition of the internet option header.
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 *  @see ip_header
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 */
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typedef struct ip_option    ip_option_t;
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/** Type definition of the internet option header pointer.
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 *  @see ip_header
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 */
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typedef ip_option_t *       ip_option_ref;
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/** Internet option header.
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 *  Only type field is always valid.
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 *  Other fields' validity depends on the option type.
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 */
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struct ip_option{
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    /** A single octet of option-type.
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     */
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    uint8_t     type;
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    /** An option length octet.
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     */
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    uint8_t     length;
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    /** A~pointer.
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     */
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    uint8_t     pointer;
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#ifdef ARCH_IS_BIG_ENDIAN
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    /** The number of IP modules that cannot register timestamps due to lack of space.
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     */
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    uint8_t overflow:4;
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    /** Various internet timestamp control flags.
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     */
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    uint8_t flags:4;
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#else
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    /** Various internet timestamp control flags.
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     */
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    uint8_t flags:4;
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    /** The number of IP modules that cannot register timestamps due to lack of space.
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     */
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    uint8_t overflow:4;
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#endif
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} __attribute__ ((packed));
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/** @name IP flags definitions
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 */
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/*@{*/
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/** Fragment flag field shift.
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 */
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#define IPFLAG_FRAGMENT_SHIFT       1
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/** Fragmented flag field shift.
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 */
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#define IPFLAG_FRAGMENTED_SHIFT     0
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/** May fragment flag value.
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 *  Allows the packet fragmentation.
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 */
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#define IPFLAG_MAY_FRAGMENT         ( 0x0 << IPFLAG_FRAGMENT_SHIFT )
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/** Don't fragment flag value.
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 *  Permits the packet fragmentation.
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 */
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#define IPFLAG_DONT_FRAGMENT        ( 0x1 << IPFLAG_FRAGMENT_SHIFT )
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/** Last fragment flag value.
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 *  Indicates the last packet fragment.
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 */
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#define IPFLAG_LAST_FRAGMENT        ( 0x0 << IPFLAG_FRAGMENTED_SHIFT )
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/** More fragments flag value.
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 *  Indicates that more packet fragments follow.
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 */
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#define IPFLAG_MORE_FRAGMENTS       ( 0x1 << IPFLAG_FRAGMENTED_SHIFT )
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/*@}*/
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/** Type definition of the internet version 4 pseudo header.
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 *  @see ipv4_pseudo_header
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 */
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typedef struct ipv4_pseudo_header   ipv4_pseudo_header_t;
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/** Type definition of the internet version 4 pseudo header pointer.
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 *  @see ipv4_pseudo_header
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 */
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typedef ipv4_pseudo_header_t *      ipv4_pseudo_header_ref;
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/** Internet version 4 pseudo header.
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 */
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struct ipv4_pseudo_header{
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    /** The source address.
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     */
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    uint32_t    source_address;
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    /** The destination address.
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     */
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    uint32_t    destination_address;
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    /** Reserved byte.
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     *  Must be zero.
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     */
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    uint8_t     reserved;
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    /** This field indicates the next level protocol used in the data portion of the internet datagram.
272
     */
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    uint8_t     protocol;
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    /** Data length is the length of the datagram, measured in octets.
275
     */
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    uint16_t    data_length;
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} __attribute__ ((packed));
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#endif
280
 
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/** @}
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 */