dnsaur

An asynchronous DNS stub resolver.

Motivation

The monoio async runtime does not ship with an asynchronous DNS resolver, and rather relies on a threadpool to handle the blocking calls (like most other runtimes). This library aims to do the resolution in an async manner, including the file system access (using io_uring).

Usage

use std::net::IpAddr;
use std::time::Duration;
use std::collections::BTreeSet;

use dnsaur::{StubResolver, Error};

#[monoio::main(driver = "iouring", enable_timer = true)]
async fn main() -> Result<(), Error> {
    let mut dns = dnsaur::StubResolver::load().await?;
    // pairs of (ip, ttl)
    let ips: Vec<(IpAddr, Duration)> = dns.lookup("example.com").await?;
    let ips = dns.lookup::<BTreeSet<_>>("example.com").await?;
    // reload
    let _ = dns.reload().await?;
    Ok(())
}

or if you want a global client instance, enable the feature global:

use std::net::IpAddr;
use std::time::Duration;
use std::collections::BTreeSet;

use dnsaur::Error;

#[monoio::main(driver = "iouring", enable_timer = true)]
async fn main() -> Result<(), Error> {
    // pairs of (ip, ttl)
    let ips: Vec<(IpAddr, Duration)> = dnsaur::lookup("example.com").await?;
    let ips = dnsaur::lookup::<BTreeSet<_>>("example.com").await?;
    // reload
    let _ = dnsaur::reload().await?;
    // autoreload
    monoio::spawn(async {
       loop {
           monoio::time::sleep(Duration::from_secs(5 * 60)).await;
           let _ = dnsaur::reload().await?;
       }
       Ok::<(), Error>(())
    });
    Ok(())
}

Details

• /etc/hosts and /etc/resolv.conf are parsed to build the configuration.
• The entries in the hosts are tried first, and if not present, the nameservers from resolv.conf will be queried.
• Querying of the nameservers is done sequentially (i.e. we query the second nameserver only if the first one has failed).
• A and AAAA records are queried concurrently.
• Default UDP buffer size is 1232 bytes.

Non-standard behavior

TODO

• Support for rotate

Status

Hic Sunt Dracones

License

Mozilla Public License Version 2.0. See the LICENSE file for details.

Acknowledgement

This library is inspired by async-dns