Mirror/zeek
1
0
Fork 0
mirror of https://github.com/zeek/zeek.git synced 2025-10-02 14:48:21 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 2

Switch one's complement checksum implementation

Browse source 
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
Download patch file Download diff file Expand all files Collapse all files

79
src/net_util.cc
View file

@ -16,8 +16,49 @@
namespace zeek {
// - adapted from tcpdump
// Returns the ones-complement checksum of a chunk of b short-aligned bytes.
uint16_t detail::ip4_in_cksum(const IPAddr& src, const IPAddr& dst,
uint8_t next_proto, const uint8_t* data, int len)
{
constexpr auto nblocks = 2;
detail::checksum_block blocks[nblocks];
ipv4_pseudo_hdr ph;
memset(&ph, 0, sizeof(ph));
src.CopyIPv4(&ph.src);
dst.CopyIPv4(&ph.dst);
ph.len = htons(static_cast<uint16_t>(len));
ph.next_proto = next_proto;
blocks[0].block = reinterpret_cast<const uint8_t*>(&ph);
blocks[0].len = sizeof(ph);
blocks[1].block = data;
blocks[1].len = len;
return in_cksum(blocks, nblocks);
}
uint16_t detail::ip6_in_cksum(const IPAddr& src, const IPAddr& dst,
uint8_t next_proto, const uint8_t* data, int len)
{
constexpr auto nblocks = 2;
detail::checksum_block blocks[nblocks];
ipv6_pseudo_hdr ph;
memset(&ph, 0, sizeof(ph));
src.CopyIPv6(&ph.src);
dst.CopyIPv6(&ph.dst);
ph.len = htonl(static_cast<uint32_t>(len));
ph.next_proto = next_proto;
blocks[0].block = reinterpret_cast<const uint8_t*>(&ph);
blocks[0].len = sizeof(ph);
blocks[1].block = data;
blocks[1].len = len;
return in_cksum(blocks, nblocks);
}
// Returns the ones-complement checksum of a chunk of 'b' bytes.
int ones_complement_checksum(const void* p, int b, uint32_t sum)
{
const unsigned char* sp = (unsigned char*) p;
@ -46,17 +87,7 @@ int ones_complement_checksum(const IPAddr& a, uint32_t sum)
int icmp_checksum(const struct icmp* icmpp, int len)
{
uint32_t sum;
if ( len % 2 == 1 )
// Add in pad byte.
sum = htons(((const u_char*) icmpp)[len - 1] << 8);
else
sum = 0;
sum = ones_complement_checksum((void*) icmpp, len, sum);
return sum;
return detail::in_cksum(reinterpret_cast<const uint8_t*>(icmpp), len);
}
#ifdef ENABLE_MOBILE_IPV6
@ -89,26 +120,8 @@ int icmp6_checksum(const struct icmp* icmpp, const IP_Hdr* ip, int len)
{
// ICMP6 uses the same checksum function as ICMP4 but a different
// pseudo-header over which it is computed.
uint32_t sum;
if ( len % 2 == 1 )
// Add in pad byte.
sum = htons(((const u_char*) icmpp)[len - 1] << 8);
else
sum = 0;
// Pseudo-header as for UDP over IPv6 above.
sum = ones_complement_checksum(ip->SrcAddr(), sum);
sum = ones_complement_checksum(ip->DstAddr(), sum);
uint32_t l = htonl(len);
sum = ones_complement_checksum((void*) &l, 4, sum);
uint32_t addl_pseudo = htons(IPPROTO_ICMPV6);
sum = ones_complement_checksum((void*) &addl_pseudo, 4, sum);
sum = ones_complement_checksum((void*) icmpp, len, sum);
return sum;
return detail::ip6_in_cksum(ip->SrcAddr(), ip->DstAddr(), IPPROTO_ICMPV6,
reinterpret_cast<const uint8_t*>(icmpp), len);
}