domain/resolv/resolver.rs
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//! The trait defining an abstract resolver.
use crate::base::message::Message;
use crate::base::name::ToName;
use crate::base::question::Question;
use std::future::Future;
use std::io;
//----------- Resolver -------------------------------------------------------
/// A type that acts as a DNS resolver.
///
/// A resolver is anything that tries to answer questions using the DNS. The
/// [`query`] method takes a single question and returns a future that will
/// eventually resolve into either an answer or an IO error.
///
/// [`query`]: Resolver::query
pub trait Resolver {
type Octets: AsRef<[u8]>;
/// The answer returned by a query.
///
/// This isn’t [`Message`] directly as it may be useful for the resolver
/// to provide additional information. For instance, a validating
/// resolver (a resolver that checks whether DNSSEC signatures are
/// correct) can supply more information as to why validation failed.
type Answer: AsRef<Message<Self::Octets>>;
/// The future resolving into an answer.
type Query: Future<Output = Result<Self::Answer, io::Error>> + Send;
/// Returns a future answering a question.
///
/// The method takes anything that can be converted into a question and
/// produces a future trying to answer the question.
fn query<N, Q>(&self, question: Q) -> Self::Query
where
N: ToName,
Q: Into<Question<N>>;
}
//------------ SearchNames ---------------------------------------------------
/// A type that can produce a list of name suffixes.
///
/// Legacy systems have the ability to interpret relative domain names as
/// within the local system. They provide a list of suffixes that can be
/// attached to the name to make it absolute.
///
/// A search resolver is a resolver that provides such a list. This is
/// implemented via an iterator over domain names.
pub trait SearchNames {
type Name: ToName;
type Iter: Iterator<Item = Self::Name>;
/// Returns an iterator over the search suffixes.
fn search_iter(&self) -> Self::Iter;
}