2 #include <ip_checksum.h>
4 unsigned long compute_ip_checksum(void *addr, unsigned long length)
13 /* In the most straight forward way possible,
14 * compute an ip style checksum.
18 for(i = 0; i < length; i++) {
24 /* Add the new value */
26 /* Wrap around the carry */
28 sum = (sum + (sum >> 16)) & 0xFFFF;
31 value.byte[0] = sum & 0xff;
32 value.byte[1] = (sum >> 8) & 0xff;
33 return (~value.word) & 0xFFFF;
36 unsigned long add_ip_checksums(unsigned long offset, unsigned long sum, unsigned long new)
38 unsigned long checksum;
42 /* byte swap the sum if it came from an odd offset
43 * since the computation is endian independant this
46 new = ((new >> 8) & 0xff) | ((new << 8) & 0xff00);
49 if (checksum > 0xFFFF) {
52 return (~checksum) & 0xFFFF;