42 lines
820 B
C
42 lines
820 B
C
/*
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* $smu-mark$
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* $name: cksum.c$
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* $author: Salvatore Sanfilippo <antirez@invece.org>$
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* $copyright: Copyright (C) 1999 by Salvatore Sanfilippo$
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* $license: This software is under GPL version 2 of license$
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* $date: Fri Nov 5 11:55:47 MET 1999$
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* $rev: 8$
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*/
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#include "hping2.h" /* only for arch semi-indipendent data types */
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#include "globals.h"
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/*
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* from R. Stevens's Network Programming
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*/
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__u16 cksum(__u16 *buf, int nbytes)
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{
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__u32 sum;
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__u16 oddbyte;
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sum = 0;
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while (nbytes > 1) {
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sum += *buf++;
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nbytes -= 2;
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}
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if (nbytes == 1) {
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oddbyte = 0;
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*((__u16 *) &oddbyte) = *(__u16 *) buf;
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sum += oddbyte;
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}
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sum = (sum >> 16) + (sum & 0xffff);
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sum += (sum >> 16);
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/* return a bad checksum with --badcksum option */
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if (opt_badcksum) sum ^= 0x5555;
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return (__u16) ~sum;
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}
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