Stefan Reinauer | 6540ae5 | 2007-07-12 16:35:42 +0000 | [diff] [blame] | 1 | /*****************************************************************************\ |
| 2 | * compute_ip_checksum.c |
Stefan Reinauer | 6540ae5 | 2007-07-12 16:35:42 +0000 | [diff] [blame] | 3 | \*****************************************************************************/ |
| 4 | |
| 5 | #include <stdint.h> |
| 6 | #include "ip_checksum.h" |
| 7 | |
Stefan Reinauer | f527e70 | 2008-01-18 15:33:49 +0000 | [diff] [blame] | 8 | /* Note: The contents of this file were borrowed from the coreboot source |
Paul Menzel | a8843de | 2017-06-05 12:33:23 +0200 | [diff] [blame] | 9 | * code which may be obtained from https://www.coreboot.org. |
Stefan Reinauer | f527e70 | 2008-01-18 15:33:49 +0000 | [diff] [blame] | 10 | * Specifically, this code was obtained from coreboot (LinuxBIOS) |
| 11 | * version 1.0.0.8. |
Stefan Reinauer | 6540ae5 | 2007-07-12 16:35:42 +0000 | [diff] [blame] | 12 | */ |
| 13 | |
| 14 | unsigned long compute_ip_checksum(void *addr, unsigned long length) |
| 15 | { |
Stefan Reinauer | 90b96b6 | 2010-01-13 21:00:23 +0000 | [diff] [blame] | 16 | uint8_t *ptr; |
| 17 | volatile union { |
| 18 | uint8_t byte[2]; |
| 19 | uint16_t word; |
| 20 | } value; |
| 21 | unsigned long sum; |
| 22 | unsigned long i; |
| 23 | /* In the most straight forward way possible, |
| 24 | * compute an ip style checksum. |
| 25 | */ |
| 26 | sum = 0; |
| 27 | ptr = addr; |
| 28 | for (i = 0; i < length; i++) { |
| 29 | unsigned long value; |
| 30 | value = ptr[i]; |
| 31 | if (i & 1) { |
| 32 | value <<= 8; |
| 33 | } |
| 34 | /* Add the new value */ |
| 35 | sum += value; |
| 36 | /* Wrap around the carry */ |
| 37 | if (sum > 0xFFFF) { |
| 38 | sum = (sum + (sum >> 16)) & 0xFFFF; |
| 39 | } |
| 40 | } |
| 41 | value.byte[0] = sum & 0xff; |
| 42 | value.byte[1] = (sum >> 8) & 0xff; |
| 43 | return (~value.word) & 0xFFFF; |
Stefan Reinauer | 6540ae5 | 2007-07-12 16:35:42 +0000 | [diff] [blame] | 44 | } |