Rating:
All these checks:
```
if(inet_pton($ip) < (int) inet_pton($subnet)) {
// ...
}
if(! (inet_pton($ip) < inet_pton($bcast))) {
// ...
}
if($ip == $backend) {
// ...
}
```
can be bypassed by using IP address with the last part starts with `0: 192.168.112.02`. The `file_get_contents` function will normalize the IP into 192.168.112.2 and fetch the content.