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mirror of https://code.semirocket.science/wrapsix synced 2024-11-10 08:10:59 +02:00
wrapsix/wrapper/checksum.c
xHire 4bc68edce5 Improved creating of a socket for the resolver
Written new mechanism of wrapper from scratch in C
* It listens to all ICMPv6 packets (for now) and translates them to ICMPv4 ones
* It can compute the checksum of the packet as well
2008-12-31 13:41:21 +01:00

31 lines
441 B
C

unsigned short checksum(const void *_buf, int len)
{
const unsigned short *buf = _buf;
unsigned sum = 0;
while (len >= 2) {
sum += *buf ++;
if (sum & 0x80000000) {
sum = (sum & 0xffff) + (sum >> 16);
}
len -= 2;
}
if (len) {
unsigned char temp[2];
temp[0] = *(unsigned char *) buf;
temp[1] = 0;
sum += *(unsigned short *) temp;
}
while (sum >> 16) {
sum = (sum & 0xffff) + (sum >> 16);
}
return ~sum;
}