/*****************************************************************************\
* compute_ip_checksum.c
- * $Id$
\*****************************************************************************/
#include <stdint.h>
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;
+ 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;
}