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120 lines
3.5 KiB
C
120 lines
3.5 KiB
C
/*
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* Copyright (C) 2019 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @defgroup net_ipv6_ext_frag IPv6 fragmentation extension
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* @ingroup net_ipv6_ext
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* @brief Definitions for IPv6 fragmentation extension
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* @see [RFC 8200, section 4.5](https://tools.ietf.org/html/rfc8200#section-4.5)
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* @{
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*
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* @file
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* @brief Fragmentation extension definitions
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*
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* @author Martine Lenders <m.lenders@fu-berlin.de>
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*/
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#ifndef NET_IPV6_EXT_FRAG_H
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#define NET_IPV6_EXT_FRAG_H
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#include <stdbool.h>
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#include <stdint.h>
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#include "byteorder.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define IPV6_EXT_FRAG_OFFSET_MASK (0xFFF8) /**< Mask for the offset */
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#define IPV6_EXT_FRAG_M (0x0001) /**< M flag */
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/**
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* @brief Fragment header definition
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*/
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typedef struct __attribute__((packed)) {
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uint8_t nh; /**< next header */
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uint8_t resv; /**< reserved */
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/**
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* @brief 11-bit fragment offset and flags
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*
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* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Fragment Offset |Res|M|
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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*/
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network_uint16_t offset_flags;
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network_uint32_t id; /**< identification */
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} ipv6_ext_frag_t;
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/**
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* @brief Get offset of fragment in bytes
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*
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* @param[in] frag A fragment header
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*
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* @return Offset of fragment in bytes.
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*/
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static inline unsigned ipv6_ext_frag_get_offset(const ipv6_ext_frag_t *frag)
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{
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/* The offset is left-shifted by 3 bytes in the header * (equivalent to
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* multiplication with 8), and the offset is in units 8 bytes
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* so no shifting or multiplying necessary to get offset in bytes */
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return (byteorder_ntohs(frag->offset_flags) & IPV6_EXT_FRAG_OFFSET_MASK);
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}
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/**
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* @brief Checks if more fragments are coming after the given fragment
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*
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* @param[in] frag A fragment header
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*
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* @return true, when more fragments are coming after the given fragment.
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* @return false, when the given fragment is the last.
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*/
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static inline bool ipv6_ext_frag_more(const ipv6_ext_frag_t *frag)
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{
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return (byteorder_ntohs(frag->offset_flags) & IPV6_EXT_FRAG_M);
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}
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/**
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* @brief Sets the offset field of a fragment header
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*
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* @note Must be called before @ref ipv6_ext_frag_set_more()
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*
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* @param[in,out] frag A fragment header
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* @param[in] offset The offset of the fragment in bytes.
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* Is assumed to be a multiple of 8.
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* Is assumed to be lesser or equal to 65528.
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*/
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static inline void ipv6_ext_frag_set_offset(ipv6_ext_frag_t *frag,
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unsigned offset)
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{
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/* The offset is left-shifted by 3 bytes in the header * (equivalent to
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* multiplication with 8), and the offset is a multiple of 8 bytes
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* so no shifting or division necessary to set offset in units of 8 bytes */
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frag->offset_flags = byteorder_htons(offset & IPV6_EXT_FRAG_OFFSET_MASK);
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}
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/**
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* @brief Sets the M flag of a fragment header
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*
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* @note Must be called after @ref ipv6_ext_frag_set_offset()
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*
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* @param[in,out] frag A fragment header
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*/
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static inline void ipv6_ext_frag_set_more(ipv6_ext_frag_t *frag)
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{
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frag->offset_flags.u8[1] |= IPV6_EXT_FRAG_M;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif /* NET_IPV6_EXT_FRAG_H */
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/** @} */
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