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/*****************************************************************************\
* compute_ip_checksum.c
\*****************************************************************************/
#include <stdint.h>
#include "ip_checksum.h"
/* Note: The contents of this file were borrowed from the coreboot source
* code which may be obtained from https://www.coreboot.org.
* Specifically, this code was obtained from coreboot (LinuxBIOS)
* version 1.0.0.8.
*/
unsigned long compute_ip_checksum(void *addr, unsigned long length)
{
uint8_t *ptr;
volatile union {
uint8_t byte[2];
uint16_t word;
} value;
unsigned long sum;
unsigned long i;
/* In the most straight forward way possible,
* compute an ip style checksum.
*/
sum = 0;
ptr = addr;
for (i = 0; i < length; i++) {
unsigned long value;
value = ptr[i];
if (i & 1) {
value <<= 8;
}
/* Add the new value */
sum += value;
/* Wrap around the carry */
if (sum > 0xFFFF) {
sum = (sum + (sum >> 16)) & 0xFFFF;
}
}
value.byte[0] = sum & 0xff;
value.byte[1] = (sum >> 8) & 0xff;
return (~value.word) & 0xFFFF;
}
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