14e2277962
while others dislike them being extra commits, let's clean them up once and for all for the existing code. If it's ugly, let it only be ugly once :-) Signed-off-by: Stefan Reinauer <stepan@coresystems.de> Acked-by: Stefan Reinauer <stepan@coresystems.de> git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5507 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1
53 lines
1.1 KiB
C
53 lines
1.1 KiB
C
#include <stdint.h>
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#include <ip_checksum.h>
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unsigned long compute_ip_checksum(void *addr, unsigned long length)
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{
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uint8_t *ptr;
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volatile union {
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uint8_t byte[2];
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uint16_t word;
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} value;
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unsigned long sum;
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unsigned long i;
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/* In the most straight forward way possible,
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* compute an ip style checksum.
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*/
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sum = 0;
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ptr = addr;
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for(i = 0; i < length; i++) {
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unsigned long v;
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v = ptr[i];
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if (i & 1) {
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v <<= 8;
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}
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/* Add the new value */
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sum += v;
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/* Wrap around the carry */
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if (sum > 0xFFFF) {
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sum = (sum + (sum >> 16)) & 0xFFFF;
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}
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}
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value.byte[0] = sum & 0xff;
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value.byte[1] = (sum >> 8) & 0xff;
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return (~value.word) & 0xFFFF;
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}
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unsigned long add_ip_checksums(unsigned long offset, unsigned long sum, unsigned long new)
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{
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unsigned long checksum;
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sum = ~sum & 0xFFFF;
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new = ~new & 0xFFFF;
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if (offset & 1) {
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/* byte swap the sum if it came from an odd offset
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* since the computation is endian independant this
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* works.
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*/
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new = ((new >> 8) & 0xff) | ((new << 8) & 0xff00);
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}
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checksum = sum + new;
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if (checksum > 0xFFFF) {
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checksum -= 0xFFFF;
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}
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return (~checksum) & 0xFFFF;
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}
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