Join a multicast group using Rust with reuse addr & port

join_multicast.rs

#[cfg(unix)]
fn bind_multicast(socket: &Socket, addr: &SocketAddr) -> io::Result<()> {
    socket.bind(&socket2::SockAddr::from(*addr))
}

/// Returns a socket joined to the multicast address
fn join_multicast(
    multicast_addr: &SocketAddr,
) -> Result<Option<std::net::UdpSocket>, io::Error> {

    let ip_addr = multicast_addr.ip();
    if !ip_addr.is_multicast() {
        return Err(io::Error::new(
            io::ErrorKind::Other,
            format!("expected multicast address for binding: {}", ip_addr),
        ));
    }
  
    let socket = match ip_addr {
        IpAddr::V4(ref mdns_v4) => {
            let socket = Socket::new(
                Domain::ipv4(),
                Type::dgram(),
                Some(Protocol::udp()),
            ).expect("ipv4 dgram socket");
            socket.join_multicast_v4(mdns_v4, &Ipv4Addr::new(0, 0, 0, 0)).expect("join_multicast_v4");
            socket
        }
        IpAddr::V6(ref mdns_v6) => {
            let socket = Socket::new(
                Domain::ipv6(),
                Type::dgram(),
                Some(Protocol::udp()),
            ).expect("ipv6 dgram socket");

            socket.set_only_v6(true)?;
            socket.join_multicast_v6(mdns_v6, 0).expect("join_multicast_v6");
            socket
        }
    };

    socket.set_nonblocking(true).expect("nonblocking Error");
    socket.set_reuse_address(true).expect("reuse addr Error");
    #[cfg(unix)] // this is currently restricted to Unix's in socket2
    socket.set_reuse_port(true).expect("reuse port Error");
    bind_multicast(&socket, &multicast_addr).expect("bind Error");

    Ok(Some(socket.into_udp_socket()))
}