4826970d25
This makes carry handling simpler for the compiler (though it should have been able to do this without help).
58 lines
1.3 KiB
C++
58 lines
1.3 KiB
C++
/*
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* Copyright (C) 2014 Cloudius Systems, Ltd.
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*/
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#include "ip_checksum.hh"
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#include "net.hh"
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#include <arpa/inet.h>
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namespace net {
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void checksummer::sum(const char* data, size_t len) {
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auto orig_len = len;
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if (odd) {
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csum += uint8_t(*data++);
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--len;
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}
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auto p64 = reinterpret_cast<const packed<uint64_t>*>(data);
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while (len >= 8) {
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csum += ntohq(*p64++);
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len -= 8;
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}
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auto p16 = reinterpret_cast<const packed<uint16_t>*>(p64);
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while (len >= 2) {
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csum += ntohs(*p16++);
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len -= 2;
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}
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auto p8 = reinterpret_cast<const uint8_t*>(p16);
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if (len) {
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csum += *p8++ << 8;
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len -= 1;
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}
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odd ^= orig_len & 1;
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}
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uint16_t checksummer::get() const {
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__int128 csum1 = (csum & 0xffff'ffff'ffff'ffff) + (csum >> 64);
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uint64_t csum = (csum1 & 0xffff'ffff'ffff'ffff) + (csum1 >> 64);
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csum = (csum & 0xffff) + ((csum >> 16) & 0xffff) + ((csum >> 32) & 0xffff) + (csum >> 48);
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csum = (csum & 0xffff) + (csum >> 16);
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csum = (csum & 0xffff) + (csum >> 16);
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return htons(~csum);
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}
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void checksummer::sum(const packet& p) {
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for (auto&& f : p.fragments()) {
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sum(f.base, f.size);
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}
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}
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uint16_t ip_checksum(const void* data, size_t len) {
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checksummer cksum;
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cksum.sum(reinterpret_cast<const char*>(data), len);
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return cksum.get();
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}
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}
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