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/* $Id: cksum.c,v 1.3 2004/04/14 12:30:18 antirez Exp $ */
#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;
sum = 0;
while (nbytes > 1) {
sum += *buf++;
nbytes -= 2;
}
if (nbytes == 1) {
sum += *((__u8*)buf);
}
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
/* return a bad checksum with --badcksum option */
if (opt_badcksum) sum ^= 0x5555;
return (__u16) ~sum;
}