Forwarder seems to not use /etc/hosts despite use_hosts_file == true

[hch12907]

Describe the bug

I added 201.11.11.11 example.com to /etc/hosts. Pinging example.com shows that I am pinging the IP, so the hosts configuration is correct and working. But when I used dig example.com on my DNS forwarder it returned 93.184.216.34 (the actual IP of example.com from upstream DNS) instead of the IP inside the hosts file.

To Reproduce

Here is a small snippet:

use std::str::FromStr;
use std::sync::Arc;
use std::time::Duration;

use hickory_proto::op::Query;
use hickory_proto::rr::LowerName;
use hickory_resolver::config::{NameServerConfigGroup, ResolverOpts};
use hickory_resolver::{Hosts, Name};
use hickory_server::authority::{AuthorityObject, Catalog, ZoneType};
use hickory_server::store::forwarder::{ForwardAuthority, ForwardConfig};
use hickory_server::ServerFuture;
use tokio::net::{TcpListener, UdpSocket};

#[tokio::main]
async fn main() {
    let hosts = Hosts::new();
    println!("{:?}", hosts.lookup_static_host(&Query::query(Name::from_utf8("example.com").unwrap(), hickory_proto::rr::RecordType::A)));

    let mut catalog = Catalog::new();

    let forward_config = ForwardConfig {
        name_servers: NameServerConfigGroup::quad9_tls(),
        options: Some(ResolverOpts::default())
    };

    let authority = ForwardAuthority::try_from_config(
        Name::from_str(".").unwrap(), ZoneType::Forward, &forward_config).unwrap();

    catalog.upsert(LowerName::from_str(".").unwrap(), Box::new(Arc::new(authority)) as Box<dyn AuthorityObject>);

    let mut server_future = ServerFuture::new(catalog);
    let udp_socket = UdpSocket::bind("127.0.0.1:8000").await.unwrap();
    server_future.register_socket(udp_socket);
    let tcp_socket = TcpListener::bind("127.0.0.1:8000").await.unwrap();
    server_future.register_listener(tcp_socket, Duration::from_secs(3));

    server_future.block_until_done().await.unwrap();
}

Expected behavior
As expected, the snippet above prints Some(...) with the correct RData Some(A(A(201.11.11.11))).

But unexpectedly, dig @127.0.0.1 -p 8000 example.com still returned 93.184.216.34. It should be 201.11.11.11.

System:

• OS: Linux
• Architecture: x86_64
• Version: Arch Linux
• rustc version: 1.75.0

Version:
Crate: hickory-resolver / hickory-server
Version: 0.24.0

[hch12907]

This is because AsyncResolver::inner_lookup doesn't take hosts into account. Only AsyncResolver::lookup_ip does.

[djc]

How/why do you end up calling inner_lookup(), if not via lookup_ip()?

[hch12907]

(Going by memory since I am not with my laptop currently) ForwardAuthority calls AsyncResolver::lookup(), which in turn calls inner_lookup().