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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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49
src/net_util.h
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@ -121,7 +121,54 @@ ZEEK_FORWARD_DECLARE_NAMESPACED(IP_Hdr, zeek);
namespace zeek {
// Returns the ones-complement checksum of a chunk of b short-aligned bytes.
namespace detail {
struct checksum_block {
const uint8_t* block;
int len;
};
struct ipv4_pseudo_hdr {
in_addr src;
in_addr dst;
uint8_t zero;
uint8_t next_proto;
uint16_t len;
};
struct ipv6_pseudo_hdr {
in6_addr src;
in6_addr dst;
uint32_t len;
uint8_t zero[3];
uint8_t next_proto;
};
extern uint16_t in_cksum(const checksum_block* blocks, int num_blocks);
inline uint16_t in_cksum(const uint8_t* data, int len)
{
checksum_block cb{data, len};
return in_cksum(&cb, 1);
}
extern uint16_t ip4_in_cksum(const IPAddr& src, const IPAddr& dst,
uint8_t next_proto, const uint8_t* data, int len);
extern uint16_t ip6_in_cksum(const IPAddr& src, const IPAddr& dst,
uint8_t next_proto, const uint8_t* data, int len);
inline uint16_t ip_in_cksum(bool is_ipv4, const IPAddr& src, const IPAddr& dst,
uint8_t next_proto, const uint8_t* data, int len)
{
if ( is_ipv4 )
return ip4_in_cksum(src, dst, next_proto, data, len);
return ip6_in_cksum(src, dst, next_proto, data, len);
}
} // namespace zeek::detail
// Returns the ones-complement checksum of a chunk of 'b' bytes.
extern int ones_complement_checksum(const void* p, int b, uint32_t sum);
extern int ones_complement_checksum(const IPAddr& a, uint32_t sum);