Return all ip addresses of a subnetwork.
```rust use subnetwork;
fn main() { let ret = match subnetwork::ipv4_iter("192.168.1.0", 24) { Some(ret) => ret, None => panic!("get subnet failed"), }; for r in ret { println!("{:?}", r); } } ```
bash
192.168.1.1
192.168.1.2
192.168.1.3
192.168.1.4
192.168.1.5
192.168.1.6
192.168.1.7
192.168.1.8
192.168.1.9
192.168.1.10
192.168.1.11
192.168.1.12
192.168.1.13
192.168.1.14
192.168.1.15
192.168.1.16
...
192.168.1.255