libnids学习笔记------【hash算法】

[1] IP四元组hash

u_int
mkhash (u_int src, u_short sport, u_int dest, u_short dport)
{
  u_int res = 0;
  int i;
  u_char data[12];
  u_int *stupid_strict_aliasing_warnings=(u_int*)data;
  *stupid_strict_aliasing_warnings = src;
  *(u_int *) (data + 4) = dest;
  *(u_short *) (data + 8) = sport;
  *(u_short *) (data + 10) = dport;
  for (i = 0; i < 12; i++)
    res = ( (res << 8) + (data[perm[i]] ^ xor[i])) % 0xff100f;
  return res;
}

[2]数组hash索引

static int
mk_hash_index(struct tuple4 addr)
{
  int hash=mkhash(addr.saddr, addr.source, addr.daddr, addr.dest);
  return hash % tcp_stream_table_size;
}s