-/*
- * Checksum routine for Internet Protocol family headers (C Version)
- */
-static uint16_t
-in_cksum(uint16_t *addr, int len)
-{
- int nleft = len;
- uint16_t *w = addr;
- uint16_t answer;
- int sum = 0;
-
- /*
- * Our algorithm is simple, using a 32 bit accumulator (sum),
- * we add sequential 16 bit words to it, and at the end, fold
- * back all the carry bits from the top 16 bits into the lower
- * 16 bits.
- */
- while (nleft > 1) {
- sum += *w++;
- nleft -= 2;
- }
-
- /* mop up an odd byte, if necessary */
- if (nleft == 1)
- sum += *(unsigned char *)w;
-
- /* add back carry outs from top 16 bits to low 16 bits */
- sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
- sum += (sum >> 16); /* add carry */
- answer = ~sum; /* truncate to 16 bits */
- return answer;
-}
-