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