Example for raw dns query?

[pusateri]

resolve README lists “querying for raw DNS records“ as a feature but could you add an example for how this is supposed to work? Maybe TXT records would make a good example since they are specifically listed.

If not an example, maybe just some hints in this issue?

[partim]

Will do!

As a hint for now: Resolver (and subsequently StubResolver) has a method query that takes a question and returns a Query which is just a future for the response. So, basically, the flow is the same as with, say, addresses but with query instead of lookup_addr.

[pusateri]

Thanks. How about sending an Update and waiting for a response? How does that fit into the existing library?

[partim]

It doesn’t fit too well at this point. If your updates are reasonably simple, you can probably do the sending using UDP sockets yourself taking inspiration from domain-resolv/src/stub/net/udp.rs. If you don’t need fail-over, it’ll be even more simple.

[pusateri]

Ok, thanks. I'll homebrew something. I want to add a timeout on the response too so I know to try another server. I'm going to run into this with Push Notifications too. They don't always look like queries but they are Messages.

[pusateri]

Also, FYI, Push Notifications don't always get a response.

[partim]

I feel like UPDATE support would be a good feature for a separate module. It may also be a good reason to factor out the networking code into its own module rather than have it in the resolver.

This currently is an issue with async functions not working in no_std crates, but apparently that is being fixed with the next Rust release.

[glts]

Also interested in an example ... StubResolver::run seems to be exactly what I need to perform a simple synchronous DNS query, but I haven't been able to write a closure that is acceptable to the compiler.

[partim]

I’ve added an example in #65 and, incidentally, also found an issue with starting the runtime. I’ll release a new version of domain-resolv soon.

[pemensik]

Is there simple way to use also async version of raw queries?

I have made this function:

use domain::resolv::StubResolver;
use domain::base::question::Question;
use domain::base::name;

async fn get_root_soa(resolver: &StubResolver) {
    let root = name::Dname::root();
    let question = Question::new_in(root, Rtype::Soa);
    match resolver.query(question).await {
        Ok(answer) => {
            match answer.answer() {
                Ok(rrset) => println!("Root soa answer: {:?}", rrset),
                Err(err) => println!("Error decoding root SOA answer: {}", err),
            };
        },
        Err(err) => {
            println!("Root soa resolution failed!");
        }
    };
}

But rust compiler complains with:

error[E0698]: type inside `async fn` body must be known in this context
   --> src/main.rs:109:16
    |
109 |     let root = name::Dname::root();
    |                ^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `Octets` declared on the struct `Dname`
    |
note: the type is part of the `async fn` body because of this `await`
   --> src/main.rs:111:35
    |
111 |     match resolver.query(question).await {
    |                                   ^^^^^^

I hoped Dname is just implementation detail. But I don't know how to define the full type in this case. And I just used root, not any parsed domain. Could be also working asynchronous variant of sync test added?

[pemensik]

I would ask on better channel, but I haven't found any. Reported on #133

[sigh-gone]

How do i get the StubResolver with the latest iteration? I'm trying to get domain records.

[partim]

@pemensik Sorry, I somehow missed your question (or maybe thought you would start a discussion as suggested in #133.)

The issue with Dname::root is that is generic over the octets sequence type. So either you need to specify the desired type, e.g., through Dname::<&'static [u8]>::root(), or you use one of the functions that only work for a specific type such as Dname::root_slice().

[partim]

@sigh-gone If you don’t care about any specific configuration, StubResolver::new() should work. The examples directory in the repository has a few examples on how to do actual lookups with it.

[partim]

I’m closing the issue for now. Feel free to reopen it if you have a follow-up question.