NLnetLabs-domain/examples/client.rs

use std::net::UdpSocket;
use std::str::FromStr;

use domain::base::opt::AllOptData;
use domain::base::{
    Message, MessageBuilder, Name, Rtype, StaticCompressor, StreamTarget,
};
use domain::rdata::AllRecordData;

fn create_message() -> StreamTarget<Vec<u8>> {
    // Create a message builder wrapping a compressor wrapping a stream
    // target.
    let mut msg = MessageBuilder::from_target(StaticCompressor::new(
        StreamTarget::new_vec(),
    ))
    .unwrap();

    // Set the RD bit and a random ID in the header and proceed to
    // the question section.
    msg.header_mut().set_rd(true);
    msg.header_mut().set_random_id();
    let mut msg = msg.question();

    // Add a hard-coded question and proceed to the answer section.
    msg.push((Name::<Vec<u8>>::from_str("example.com.").unwrap(), Rtype::A))
        .unwrap();

    // Skip to the additional section
    let mut msg = msg.additional();

    // Add an OPT record.
    msg.opt(|opt| {
        opt.set_udp_payload_size(4096);
        Ok(())
    })
    .unwrap();

    // Convert the builder into the actual message.
    msg.finish().into_target()
}

fn main() {
    // Bind a UDP socket to a kernel-provided port
    let socket =
        UdpSocket::bind("0.0.0.0:0").expect("couldn't bind to address");

    let message = create_message();

    let server: String = "127.0.0.1".to_string();
    let port: u16 = 53;

    // Send message off to the server using our socket
    socket
        .send_to(message.as_dgram_slice(), (server, port))
        .unwrap();

    // Create recv buffer
    let mut buffer = vec![0; 1232];

    // Recv in buffer
    socket.recv_from(&mut buffer).unwrap();

    // Parse and print the response
    let response = Message::from_octets(buffer).unwrap();

    for question in response.question() {
        println!("{}", question.unwrap());
    }

    // Unpack and parse with all known record types
    for record in response.answer().unwrap().limit_to::<AllRecordData<_, _>>()
    {
        println!("{}", record.unwrap());
    }

    for record in response
        .authority()
        .unwrap()
        .limit_to::<AllRecordData<_, _>>()
    {
        println!("{}", record.unwrap());
    }

    // Display is only implemented for some OPTs at the time of writing
    for option in response.opt().unwrap().opt().iter::<AllOptData<_, _>>() {
        let opt = option.unwrap();
        match opt {
            AllOptData::Nsid(nsid) => println!("{nsid}"),
            AllOptData::ExtendedError(extendederror) => {
                println!("{extendederror}")
            }
            _ => println!("NO OPT!"),
        }
    }
}