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39 lines
840 B
C++
39 lines
840 B
C++
/*
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* Copyright (C) 2014 Cloudius Systems, Ltd.
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*
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*/
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#include "ip.hh"
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namespace net {
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uint16_t ip_checksum(void* data, size_t len) {
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uint64_t csum = 0;
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auto p64 = reinterpret_cast<uint64_t*>(data);
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while (len >= 8) {
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auto old = csum;
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csum += ntohq(*p64++);
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csum += (csum < old);
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len -= 8;
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}
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auto p16 = reinterpret_cast<uint16_t*>(p64);
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while (len >= 2) {
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auto old = csum;
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csum += ntohs(*p16++);
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csum += (csum < old);
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len -= 2;
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}
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auto p8 = reinterpret_cast<uint16_t*>(p16);
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if (len) {
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auto old = csum;
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csum += *p8++;
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csum += (csum < old);
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len -= 1;
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}
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csum = (csum & 0xffff) + ((csum >> 16) & 0xffff) + ((csum >> 32) & 0xffff) + (csum >> 48);
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csum += csum >> 16;
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return htons(~csum);
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}
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}
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