[GH-ISSUE #2836] 'hosts' doesn't seem to work #1070

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opened 2026-03-16 01:32:13 +03:00 by kerem · 4 comments

kerem commented

2026-03-16 01:32:13 +03:00

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Originally created by @ryoii on GitHub (Mar 10, 2025).
Original GitHub issue: https://github.com/hickory-dns/hickory-dns/issues/2836

I want to use the built-in 'hosts' to handle some DNS requests. I try like this

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let mut root_cert_store = rustls::RootCertStore::empty();
    root_cert_store.roots = webpki_roots::TLS_SERVER_ROOTS.into();

    let dns_name = "1.1.1.1";
    // let dns_ips = vec![dns_name.parse()?];
    let dns_ips = vec![];
    let ns = NameServerConfigGroup::from_ips_https(
        &dns_ips,
        443,
        "".to_string(),
        true
    );

    let mut opt = ResolverOpts::default();
    opt.use_hosts_file = ResolveHosts::Always;
    opt.tls_config = ClientConfig::builder()
        .with_root_certificates(root_cert_store)
        .with_no_client_auth();

    let config = ResolverConfig::from_parts(None, vec![], ns);
    let mut hosts = Hosts::new();
    hosts.read_hosts_conf("0.0.0.0 www.google.com".as_bytes())?;

    // with hosts
    {
        let query = Query::query("www.google.com".into_name()?, RecordType::A);
        let lookup = hosts.lookup_static_host(&query);
        println!("Lookup for {:?}: {:?}", query, lookup);
    }

    // with resolver
    {
        let mut resolver = TokioResolver::tokio(config, opt);
        resolver.set_hosts(Some(hosts));

        let lookup = resolver.lookup_ip("www.google.com").await?;
        println!("Lookup result: {:?}", lookup);
    }

    Ok(())
}

It returns an error proto error: no connections available while calling lookup_ip.
Once I set a doh server let dns_ips = vec![dns_name.parse()?];, It works but doesn't return 0.0.0.0 as I expected.

Library version
hickory-resolver = { version = "0.25.0-alpha.5", features = ["dns-over-rustls", "dns-over-https-rustls"]}

Originally created by @ryoii on GitHub (Mar 10, 2025). Original GitHub issue: https://github.com/hickory-dns/hickory-dns/issues/2836 I want to use the built-in 'hosts' to handle some DNS requests. I try like this ```rust #[tokio::main] async fn main() -> anyhow::Result<()> { let mut root_cert_store = rustls::RootCertStore::empty(); root_cert_store.roots = webpki_roots::TLS_SERVER_ROOTS.into(); let dns_name = "1.1.1.1"; // let dns_ips = vec![dns_name.parse()?]; let dns_ips = vec![]; let ns = NameServerConfigGroup::from_ips_https( &dns_ips, 443, "".to_string(), true ); let mut opt = ResolverOpts::default(); opt.use_hosts_file = ResolveHosts::Always; opt.tls_config = ClientConfig::builder() .with_root_certificates(root_cert_store) .with_no_client_auth(); let config = ResolverConfig::from_parts(None, vec![], ns); let mut hosts = Hosts::new(); hosts.read_hosts_conf("0.0.0.0 www.google.com".as_bytes())?; // with hosts { let query = Query::query("www.google.com".into_name()?, RecordType::A); let lookup = hosts.lookup_static_host(&query); println!("Lookup for {:?}: {:?}", query, lookup); } // with resolver { let mut resolver = TokioResolver::tokio(config, opt); resolver.set_hosts(Some(hosts)); let lookup = resolver.lookup_ip("www.google.com").await?; println!("Lookup result: {:?}", lookup); } Ok(()) } ``` It returns an error `proto error: no connections available` while calling `lookup_ip`. Once I set a doh server `let dns_ips = vec![dns_name.parse()?];`, It works but doesn't return `0.0.0.0` as I expected. Library version `hickory-resolver = { version = "0.25.0-alpha.5", features = ["dns-over-rustls", "dns-over-https-rustls"]}`

kerem closed this issue

2026-03-16 01:32:18 +03:00

kerem commented

2026-03-16 01:32:24 +03:00

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@djc commented on GitHub (Mar 10, 2025):

Your example configures 0 IP addresses for the NameServerConfigGroup so it's not surprising that the resolver is unable to make a connection. Do you want to argue that an empty config group should still be able to resolve names that are configured in the hosts file, without even trying DNS queries?

@djc commented on GitHub (Mar 10, 2025): Your example configures 0 IP addresses for the `NameServerConfigGroup` so it's not surprising that the resolver is unable to make a connection. Do you want to argue that an empty config group should still be able to resolve names that are configured in the hosts file, without even trying DNS queries?

kerem commented

2026-03-16 01:32:29 +03:00

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@ryoii commented on GitHub (Mar 10, 2025):

Do you want to argue that an empty config group should still be able to resolve names that are configured in the hosts file, without even trying DNS queries?

Sure, if the hosts file can provide query results, shouldn't the request for the dns service be send?

But, as I said, even if I provide the IP address for the NameServerConfigGroup

    let dns_name = "1.1.1.1";
    let dns_ips = vec![dns_name.parse()?];
    // let dns_ips = vec![];
    let ns = NameServerConfigGroup::from_ips_https(
        &dns_ips,
        443,
        "".to_string(),
        true
    );

It also won't return 0.0.0.0 as I was expected.

@ryoii commented on GitHub (Mar 10, 2025): > Do you want to argue that an empty config group should still be able to resolve names that are configured in the hosts file, without even trying DNS queries? Sure, if the hosts file can provide query results, shouldn't the request for the dns service be send? But, as I said, even if I provide the IP address for the `NameServerConfigGroup` ```rust let dns_name = "1.1.1.1"; let dns_ips = vec![dns_name.parse()?]; // let dns_ips = vec![]; let ns = NameServerConfigGroup::from_ips_https( &dns_ips, 443, "".to_string(), true ); ``` It also won't return `0.0.0.0` as I was expected.

kerem commented

2026-03-16 01:32:35 +03:00

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@djc commented on GitHub (Mar 10, 2025):

This appears to be a regression introduced with #2560 -- should be fixed in #2839. Thanks for the clear reproduction!

@djc commented on GitHub (Mar 10, 2025): This appears to be a regression introduced with #2560 -- should be fixed in #2839. Thanks for the clear reproduction!

kerem commented

2026-03-16 01:32:40 +03:00

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@ryoii commented on GitHub (Mar 11, 2025):

According to #2839
Using root domain can work around.

hosts.read_hosts_conf("0.0.0.0 www.google.com.".as_bytes())?;

@ryoii commented on GitHub (Mar 11, 2025): According to #2839 Using root domain can work around. ```rust hosts.read_hosts_conf("0.0.0.0 www.google.com.".as_bytes())?; ```

kerem referenced this issue

2026-03-16 04:00:20 +03:00

[PR #1070] [MERGED] fix docs on negative_*_ttl #1945