You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: netutil.rs
    path of file: ./repos/hypercube/src
    
    the code of the file until where you have to start completion:  

use nix::sys::socket::setsockopt;
use nix::sys::socket::sockopt::{ReuseAddr, ReusePort};
use pnet_datalink as datalink;
use rand::{thread_rng, Rng};
use reqwest;
use socket2::{Domain, SockAddr, Socket, Type};
use std::io;
use std::net::{IpAddr, Ipv4Addr, SocketAddr, UdpSocket};
use std::os::unix::io::AsRawFd;

 
pub struct UdpSocketPair {
    pub addr: SocketAddr,     
    pub receiver: UdpSocket,  
    pub sender: UdpSocket,    
}

 
pub fn get_public_ip_addr() -> Result<IpAddr, String> {
   
    
    fn test_find_eth0ish_ip_addr() {
        logger::setup();

        macro_rules! mock_interface {
            ($name:ident, $ip_mask:expr) => {
                datalink::NetworkInterface {
                    name: stringify!($name).to_string(),
                    index: 0,
                    mac: None,
                    ips: vec![IpNetwork::V4($ip_mask.parse().unwrap())],
                    flags: 0,
                }
            };
        }

        // loopback bad
        assert_eq!(
            find_eth0ish_ip_addr(&mut vec![mock_interface!(lo, "127.0.0.1/24")]),
            None
        );
        // multicast bad
        assert_eq!(
            find_eth0ish_ip_addr(&mut vec![mock_interface!(eth0, "224.0.1.5/24")]),
            None
        );

        // finds "wifi0"
        assert_eq!(
            find_eth0ish_ip_addr(&mut vec![
                mock_interface!(eth0, "224.0.1.5/24"),
                mock_interface!(eth2, "192.168.137.1/8"),
                mock_interface!(eth3, "10.0.75.1/8"),
                mock_interface!(eth4, "172.22.140.113/4"),
                mock_interface!(lo, "127.0.0.1/24"),
                mock_interface!(wifi0, "192.168.1.184/8"),
            ]),
            Some(mock_interface!(wifi0, "192.168.1.184/8").ips[0].ip())
        );
        // finds "wifi0" in the middle
        assert_eq!(
            find_eth0ish_ip_addr(&mut vec![
                mock_interface!(eth0, "224.0.1.5/24"),
                mock_interface!(eth2, "192.168.137.1/8"),
                mock_interface!(eth3, "10.0.75.1/8"),
                mock_interface!(wifi0, "192.168.1.184/8"),
                mock_interface!(eth4, "172.22.140.113/4"),
                mock_interface!(lo, "127.0.0.1/24"),
            ]),
            Some(mock_interface!(wifi0, "192.168.1.184/8").ips[0].ip())
        );
        // picks "eth2", is lowest valid "eth"
        assert_eq!(
            find_eth0ish_ip_addr(&mut vec![
                mock_interface!(eth0, "224.0.1.5/24"),
                mock_interface!(eth2, "192.168.137.1/8"),
                mock_interface!(eth3, "10.0.75.1/8"),
                mock_interface!(eth4, "172.22.140.113/4"),
                mock_interface!(lo, "127.0.0.1/24"),
            ]),
            Some(mock_interface!(eth2, "192.168.137.1/8").ips[0].ip())
        );
    }