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/* csum.c
* Computes the standard internet checksum of a set of data (from RFC1071)
* ChangeLog since sendip 2.0:
* 02/12/2001: Moved ipv6_csum into icmp.c as that is where it is used
* 22/01/2002: Include types.h to make sure u_int*_t defined on Solaris
*/
#define __USE_BSD /* GLIBC */
#define _DEFAULT_SOURCE /* LIBC5 */
#include <sys/types.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
#include "types.h"
u_int16_t csum (u_int16_t *packet, int packlen);
/* Checksum a block of data */
u_int16_t csum (u_int16_t *packet, int packlen) {
register unsigned long sum = 0;
while (packlen > 1) {
sum+= *(packet++);
packlen-=2;
}
if (packlen > 0)
sum += *(unsigned char *)packet;
/* TODO: this depends on byte order */
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return (u_int16_t) ~sum;
}
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