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/*
* Extracted from RFC 1071 with some minor changes to fix compilation on GCC,
* this can probably be improved
* --pablo 11/feb/07
*/
#include <conntrackd.h>
unsigned short do_csum(const void *addr, unsigned int count)
{
unsigned int sum = 0;
/* checksumming disabled, just skip */
if (CONFIG(flags) & DONT_CHECKSUM)
return 0;
while(count > 1) {
/* This is the inner loop */
sum += *((unsigned short *) addr++);
count -= 2;
}
/* Add left-over byte, if any */
if(count > 0)
sum += *((unsigned char *) addr);
/* Fold 32-bit sum to 16 bits */
while (sum>>16)
sum = (sum & 0xffff) + (sum >> 16);
return ~sum;
}
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