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Switch one's complement checksum implementation

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Borrows the `in_cksum` code from tcpdump, which borrowed from FreeBSD.
It handles unaligned data better and also unrolls the inner loop to
process 16 two-byte values at a time versus 2 one-byte values at a time
in the previous version.  Generally measured as ~1.5x faster in a
release build.  The new API should generally be more amenable to any
future optimization explorations since all relevant data blocks are
available within a single call rather than spread across multiple.
This commit is contained in:
Jon Siwek 2020-09-24 08:47:50 -07:00
parent 8feca7291b
commit d070709c57
12 changed files with 283 additions and 74 deletions
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19
src/analyzer/protocol/tcp/TCP_Endpoint.cc
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@ -41,14 +41,6 @@ TCP_Endpoint::TCP_Endpoint(TCP_Analyzer* arg_analyzer, bool arg_is_orig)
src_addr = is_orig ? Conn()->RespAddr() : Conn()->OrigAddr();
dst_addr = is_orig ? Conn()->OrigAddr() : Conn()->RespAddr();
checksum_base = ones_complement_checksum(src_addr, 0);
checksum_base = ones_complement_checksum(dst_addr, checksum_base);
// Note, for IPv6, strictly speaking this field is 32 bits
// rather than 16 bits. But because the upper bits are all zero,
// we get the same checksum either way. The same applies to
// later when we add in the data length in ValidChecksum().
checksum_base += htons(IPPROTO_TCP);
}
TCP_Endpoint::~TCP_Endpoint()
@ -121,17 +113,12 @@ void TCP_Endpoint::SizeBufferedData(uint64_t& waiting_on_hole,
waiting_on_hole = waiting_on_ack = 0;
}
bool TCP_Endpoint::ValidChecksum(const struct tcphdr* tp, int len) const
bool TCP_Endpoint::ValidChecksum(const struct tcphdr* tp, int len, bool ipv4) const
{
uint32_t sum = checksum_base;
int tcp_len = tp->th_off * 4 + len;
if ( len % 2 == 1 )
// Add in pad byte.
sum += htons(((const u_char*) tp)[tcp_len - 1] << 8);
sum += htons((unsigned short) tcp_len); // fill out pseudo header
sum = ones_complement_checksum((void*) tp, tcp_len, sum);
auto sum = detail::ip_in_cksum(ipv4, src_addr, dst_addr, IPPROTO_TCP,
reinterpret_cast<const uint8_t*>(tp), tcp_len);
return sum == 0xffff;
}