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| 4075 | mejdrech | 1 | /* |
| 2 | * Copyright (c) 2009 Lukas Mejdrech |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms, with or without |
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| 6 | * modification, are permitted provided that the following conditions |
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| 7 | * are met: |
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| 8 | * |
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| 9 | * - Redistributions of source code must retain the above copyright |
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| 10 | * notice, this list of conditions and the following disclaimer. |
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| 11 | * - Redistributions in binary form must reproduce the above copyright |
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| 12 | * notice, this list of conditions and the following disclaimer in the |
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| 13 | * documentation and/or other materials provided with the distribution. |
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| 14 | * - The name of the author may not be used to endorse or promote products |
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| 15 | * derived from this software without specific prior written permission. |
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| 16 | * |
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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| 27 | */ |
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| 28 | |||
| 29 | /** @addtogroup net |
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| 30 | * @{ |
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| 31 | */ |
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| 32 | |||
| 33 | /** @file |
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| 4505 | mejdrech | 34 | * General CRC and checksum computation implementation. |
| 4075 | mejdrech | 35 | */ |
| 36 | |||
| 37 | #include <sys/types.h> |
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| 38 | |||
| 4743 | mejdrech | 39 | #include "include/checksum.h" |
| 4075 | mejdrech | 40 | |
| 41 | #define CRC_DIVIDER_BE 0x04C11DB7 |
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| 42 | |||
| 43 | #define CRC_DIVIDER_LE 0xEDB88320 |
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| 44 | |||
| 4711 | mejdrech | 45 | /** IP checksum value for computed zero checksum. |
| 46 | * Zero is returned as 0xFFFF (not flipped) |
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| 47 | */ |
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| 48 | #define IP_CHECKSUM_ZERO 0xFFFFu |
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| 49 | |||
| 4558 | mejdrech | 50 | uint32_t compute_crc32_le( uint32_t seed, uint8_t * data, size_t length ){ |
| 4708 | mejdrech | 51 | size_t index; |
| 4075 | mejdrech | 52 | |
| 53 | while( length >= 8 ){ |
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| 54 | seed ^= ( * data ); |
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| 55 | for( index = 0; index < 8; ++ index ){ |
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| 56 | if( seed & 1 ){ |
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| 57 | seed = ( seed >> 1 ) ^ (( uint32_t ) CRC_DIVIDER_LE ); |
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| 58 | }else{ |
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| 59 | seed >>= 1; |
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| 60 | } |
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| 61 | } |
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| 62 | ++ data; |
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| 63 | length -= 8; |
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| 64 | } |
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| 65 | if( length > 0 ){ |
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| 66 | seed ^= ( * data ) >> ( 8 - length ); |
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| 67 | for( index = 0; index < length; ++ index ){ |
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| 68 | if( seed & 1 ){ |
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| 69 | seed = ( seed >> 1 ) ^ (( uint32_t ) CRC_DIVIDER_LE ); |
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| 70 | }else{ |
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| 71 | seed >>= 1; |
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| 72 | } |
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| 73 | } |
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| 74 | length -= 8; |
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| 75 | } |
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| 76 | return seed; |
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| 77 | } |
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| 78 | |||
| 4558 | mejdrech | 79 | uint32_t compute_crc32_be( uint32_t seed, uint8_t * data, size_t length ){ |
| 4708 | mejdrech | 80 | size_t index; |
| 4075 | mejdrech | 81 | |
| 82 | while( length >= 8 ){ |
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| 83 | seed ^= ( * data ) << 24; |
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| 84 | for( index = 0; index < 8; ++ index ){ |
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| 85 | if( seed & 0x80000000 ){ |
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| 86 | seed = ( seed << 1 ) ^ (( uint32_t ) CRC_DIVIDER_BE ); |
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| 87 | }else{ |
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| 88 | seed <<= 1; |
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| 89 | } |
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| 90 | } |
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| 91 | ++ data; |
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| 92 | length -= 8; |
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| 93 | } |
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| 94 | if( length > 0 ){ |
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| 95 | seed ^= (( * data ) & ( 0xFF << ( 8 - length ))) << 24; |
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| 96 | for( index = 0; index < length; ++ index ){ |
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| 97 | if( seed & 0x80000000 ){ |
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| 98 | seed = ( seed << 1 ) ^ (( uint32_t ) CRC_DIVIDER_BE ); |
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| 99 | }else{ |
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| 100 | seed <<= 1; |
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| 101 | } |
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| 102 | } |
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| 103 | length -= 8; |
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| 104 | } |
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| 105 | return seed; |
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| 106 | } |
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| 107 | |||
| 4558 | mejdrech | 108 | uint32_t compute_checksum( uint32_t seed, uint8_t * data, size_t length ){ |
| 109 | size_t index; |
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| 4505 | mejdrech | 110 | |
| 111 | // sum all the 16 bit fields |
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| 4558 | mejdrech | 112 | for( index = 0; index + 1 < length; index += 2 ){ |
| 4505 | mejdrech | 113 | seed += ( data[ index ] << 8 ) + data[ index + 1 ]; |
| 114 | } |
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| 115 | |||
| 116 | // last odd byte with zero padding |
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| 4558 | mejdrech | 117 | if( index + 1 == length ){ |
| 4505 | mejdrech | 118 | seed += data[ index ] << 8; |
| 119 | } |
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| 120 | |||
| 121 | return seed; |
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| 122 | } |
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| 123 | |||
| 124 | uint16_t compact_checksum( uint32_t sum ){ |
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| 125 | // shorten to the 16 bits |
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| 126 | while( sum >> 16 ) sum = ( sum & 0xFFFF ) + ( sum >> 16 ); |
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| 127 | |||
| 128 | return ( uint16_t ) sum; |
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| 129 | } |
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| 130 | |||
| 4722 | mejdrech | 131 | uint16_t flip_checksum( uint16_t checksum ){ |
| 4711 | mejdrech | 132 | // flip, zero is returned as 0xFFFF (not flipped) |
| 133 | return ( ~ checksum ) ? ( uint16_t ) ( ~ checksum ) : IP_CHECKSUM_ZERO; |
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| 134 | } |
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| 135 | |||
| 4722 | mejdrech | 136 | uint16_t ip_checksum( uint8_t * data, size_t length ){ |
| 137 | return flip_checksum( compact_checksum( compute_checksum( 0, data, length ))); |
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| 138 | } |
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| 139 | |||
| 4075 | mejdrech | 140 | /** @} |
| 141 | */ |