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#![cfg(target_os = "android")]
//! See [AndroidDnsResolver].
use async_trait::async_trait;
use hickory_resolver::{
TokioAsyncResolver,
config::{NameServerConfigGroup, ResolverConfig, ResolverOpts},
};
use mullvad_api::DnsResolver;
use std::{io, net::SocketAddr};
use talpid_core::connectivity_listener::ConnectivityListener;
/// A non-blocking DNS resolver. The default resolver uses `getaddrinfo`, which often prevents the
/// tokio runtime from being dropped, since it waits indefinitely on blocking threads. This is
/// particularly bad on Android, so we use a non-blocking resolver instead.
pub struct AndroidDnsResolver {
connectivity_listener: ConnectivityListener,
}
impl AndroidDnsResolver {
pub fn new(connectivity_listener: ConnectivityListener) -> Self {
Self {
connectivity_listener,
}
}
}
#[async_trait]
impl DnsResolver for AndroidDnsResolver {
async fn resolve(&self, host: String) -> io::Result<Vec<SocketAddr>> {
let ips = self
.connectivity_listener
.current_dns_servers()
.map_err(|err| {
io::Error::other(format!("Failed to retrieve current servers: {err}"))
})?;
let group = NameServerConfigGroup::from_ips_clear(&ips, 53, false);
let config = ResolverConfig::from_parts(None, vec![], group);
let mut opts = ResolverOpts::default();
opts.attempts = 0;
opts.use_hosts_file = false;
let resolver = TokioAsyncResolver::tokio(config, opts);
let lookup = resolver
.lookup_ip(host)
.await
.map_err(|err| io::Error::other(format!("lookup_ip failed: {err}")))?;
Ok(lookup.into_iter().map(|ip| (ip, 0).into()).collect())
}
}
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