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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 tcp

 *  @{

 */

/** @file

 *  TCP header definition.

 *  Based on the RFC~793.

 */

#ifndef __NET_TCP_HEADER_H__

#define __NET_TCP_HEADER_H__

#include <sys/types.h>

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

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

 */

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

/** Returns the TCP header length.

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

 */

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

/** Type definition of the transmission datagram header.

 *  @see tcp_header

 */

typedef struct tcp_header   tcp_header_t;

/** Type definition of the transmission datagram header pointer.

 *  @see tcp_header

 */

typedef tcp_header_t *      tcp_header_ref;

/** Type definition of the transmission datagram header option.

 *  @see tcp_option

 */

typedef struct tcp_option   tcp_option_t;

/** Type definition of the transmission datagram header option pointer.

 *  @see tcp_option

 */

typedef tcp_option_t *      tcp_option_ref;

/** Type definition of the Maximum segment size TCP option.

 *  @see ...

 */

typedef struct tcp_max_segment_size_option  tcp_max_segment_size_option_t;

/** Type definition of the Maximum segment size TCP option pointer.

 *  @see tcp_max_segment_size_option

 */

typedef tcp_max_segment_size_option_t *     tcp_max_segment_size_option_ref;

/** Transmission datagram header.

 */

struct tcp_header{

    /** The source port number.

     */

    uint16_t    source_port;

    /** The destination port number.

     */

    uint16_t    destination_port;

    /** The sequence number of the first data octet in this segment (except when SYN is present).

     *  If SYN is present the sequence number is the initial sequence number (ISN) and the first data octet is ISN+1.

     */

    uint32_t    sequence_number;

    /** If the ACK control bit is set this field contains the value of the next sequence number the sender of the segment is expecting to receive.

     *  Once a~connection is established this is always sent.

     *  @see acknowledge

     */

    uint32_t    acknowledgement_number;

#ifdef ARCH_IS_BIG_ENDIAN

    /** The number of 32~bit words in the TCP Header.

     *  This indicates where the data begins.

     *  The TCP header (even one including options) is an integral number of 32~bits long.

     */

    uint8_t header_length:4;

    /** Four bits reserved for future use.

     *  Must be zero.

     */

    uint8_t reserved1:4;

#else

    /** Four bits reserved for future use.

     *  Must be zero.

     */

    uint8_t reserved1:4;

    /** The number of 32~bit words in the TCP Header.

     *  This indicates where the data begins.

     *  The TCP header (even one including options) is an integral number of 32~bits long.

     */

    uint8_t header_length:4;

#endif

#ifdef ARCH_IS_BIG_ENDIAN

    /** Two bits reserved for future use.

     *  Must be zero.

     */

    uint8_t reserved2:2;

    /** Urgent Pointer field significant.

     *  @see tcp_header:urgent_pointer

     */

    uint8_t urgent:1;

    /** Acknowledgment field significant

     *  @see tcp_header:acknowledgement_number

     */

    uint8_t acknowledge:1;

    /** Push function.

     */

    uint8_t push:1;

    /** Reset the connection.

     */

    uint8_t reset:1;

    /** Synchronize the sequence numbers.

     */

    uint8_t synchronize:1;

    /** No more data from the sender.

     */

    uint8_t finalize:1;

#else

    /** No more data from the sender.

     */

    uint8_t finalize:1;

    /** Synchronize the sequence numbers.

     */

    uint8_t synchronize:1;

    /** Reset the connection.

     */

    uint8_t reset:1;

    /** Push function.

     */

    uint8_t push:1;

    /** Acknowledgment field significant.

     *  @see tcp_header:acknowledgement_number

     */

    uint8_t acknowledge:1;

    /** Urgent Pointer field significant.

     *  @see tcp_header:urgent_pointer

     */

    uint8_t urgent:1;

    /** Two bits reserved for future use.

     *  Must be zero.

     */

    uint8_t reserved2:2;

#endif

    /** The number of data octets beginning with the one indicated in the acknowledgment field which the sender of this segment is willing to accept.

     *  @see tcp_header:acknowledge

     */

    uint16_t    window;

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

     *  If a~segment contains an odd number of header and text octets to be checksummed, the last octet is padded on the right with zeros to form a~16~bit word for checksum purposes.

     *  The pad is not transmitted as part of the segment.

     *  While computing the checksum, the checksum field itself is replaced with zeros.

     *  The checksum also coves a~pseudo header conceptually.

     *  The pseudo header conceptually prefixed to the TCP header contains the source address, the destination address, the protocol, and the TCP length.

     *  This information gives protection against misrouted datagrams.

     *  If the computed checksum is zero, it is transmitted as all ones (the equivalent in one's complement arithmetic).

     */

    uint16_t    checksum;

    /** This field communicates the current value of the urgent pointer as a~positive offset from the sequence number in this segment.

     *  The urgent pointer points to the sequence number of the octet following the urgent data.

     *  This field is only be interpreted in segments with the URG control bit set.

     *  @see tcp_header:urgent

     */

    uint16_t    urgent_pointer;

} __attribute__ ((packed));

/** Transmission datagram header option.

 */

struct tcp_option{

    /** Option type.

     */

    uint8_t     type;

    /** Option length.

     */

    uint8_t     length;

};

/** Maximum segment size TCP option.

 */

struct tcp_max_segment_size_option{

    /** TCP option.

     *  @see TCPOPT_MAX_SEGMENT_SIZE

     *  @see TCPOPT_MAX_SEGMENT_SIZE_LENGTH

     */

    tcp_option_t    option;

    /** Maximum segment size in bytes.

     */

    uint16_t        max_segment_size;

} __attribute__ ((packed));

#endif

/** @}

 */