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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.

 *  @param header The IP packet header. Input parameter.

 */

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

/** Returns the actual IP header length.

 *  @param header The IP packet header. Input parameter.

 */

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

/** Returns the actual IP packet total length.

 *  @param header The IP packet header. Input parameter.

 */

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

/** Returns the actual IP packet data length.

 *  @param header The IP packet header. Input parameter.

 */

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

/** Returns the IP packet header checksum.

 *  @param header The IP packet header. Input parameter.

 */

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

/** Returns the fragment offest.

 *  @param length The prefixed data total length. Input parameter.

 */

#define IP_COMPUTE_FRAGMENT_OFFSET( length ) (( length ) / 8 )

/** 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.

	 *  @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 )

/*@}*/

/** 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

/** @}

 */