function is_known_ip($ip) { // updated: 2026-03-04  
  // Convert IP string to number
  if (is_string($ip)) {
    $bytes = explode('.', $ip);
    $ip = 0;
    foreach ($bytes as $n) {
      $ip <<= 8;
      $ip |= (int)$n;
    }
  }
  // Check rules
  switch ($ip & 0b0_11111111_11111111_11100000_00000000) { // mask: 255.255.224.0
    case        0b0_01000101_10101100_01100000_00000000:   // ip:   69.172.96.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11110000_00000000) { // mask: 255.255.240.0
    case        0b0_11000001_00101011_11000000_00000000:   // ip:   193.43.192.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11111111_00000000) { // mask: 255.255.255.0
    case        0b0_10111100_11010010_11101111_00000000:   // ip:   188.210.239.0
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11111111_11100000) { // mask: 255.255.255.224
    case        0b0_01001110_00000110_01000011_10000000:   // ip:   78.6.67.128
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11111111_11110000) { // mask: 255.255.255.240
    case        0b0_10010000_00110000_11000001_00010000:   // ip:   144.48.193.16
    case        0b0_10010000_00110000_11000001_10010000:   // ip:   144.48.193.144
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11111111_11111000) { // mask: 255.255.255.248
    case        0b0_01001110_00000101_01001101_01100000:   // ip:   78.5.77.96
      return true;
  }
  switch ($ip & 0b0_11111111_11111111_11111111_11111111) { // mask: 255.255.255.255
    case        0b0_00000101_01100011_11000001_11100010:   // ip:   5.99.193.226
    case        0b0_00001111_10100000_00001011_11001000:   // ip:   15.160.11.200
    case        0b0_00001111_10100000_11111010_10011110:   // ip:   15.160.250.158
    case        0b0_00001111_10100001_10100101_11110101:   // ip:   15.161.165.245
    case        0b0_00010010_01100110_00101001_11100101:   // ip:   18.102.41.229
    case        0b0_10000110_11010101_00110001_10111010:   // ip:   134.213.49.186
    case        0b0_10000110_11010101_11011011_01011101:   // ip:   134.213.219.93
    case        0b0_10000110_11010101_11011110_01010111:   // ip:   134.213.222.87
    case        0b0_10100010_00001101_10011010_10101011:   // ip:   162.13.154.171
    case        0b0_10110010_00100001_01011100_01100010:   // ip:   178.33.92.98
    case        0b0_11010100_01001101_01011111_00100010:   // ip:   212.77.95.34
    case        0b0_11010100_01001101_01011111_00100011:   // ip:   212.77.95.35
      return true;
  }
  return false;
}