Swift Asynchronous DNS Resolver

A Swift library for asynchronous DNS requests, wrapping c-ares with Swift-friendly APIs and data structures.

Project status

This is the beginning of a community-driven open-source project actively seeking contributions, be it code, documentation, or ideas.

Getting started

If you have a server-side Swift application or a cross-platform (e.g. Linux, macOS) application that needs DNS resolution, Swift Asynchronous DNS Resolver is a great idea. Below you will find all you need to know to get started.

Adding the dependency

To add a dependency on the package, declare it in your Package.swift:

.package(url: "https://github.com/apple/swift-async-dns-resolver.git", from: "0.1.0"),

and to your application target, add AsyncDNSResolver to your dependencies:

.target(name: "MyApplication", dependencies: ["AsyncDNSResolver"]),

Using a DNS resolver

// import the package
import AsyncDNSResolver

// initialize the DNS resolver
let resolver = AsyncDNSResolver()

// run a query
self.resolver.query(.A(name: "apple.com") { result in
    switch result {
    case .success(let aRecords):
        // process the ARecords
    case .failure(let error):
        // process the error
    }
})

Detailed design

The main types in the library are AsyncDNSResolver, AsyncDNSResolver.Query, and AsyncDNSResolver.Options.

AsyncDNSResolver uses the C-library c-ares underneath and delegates all queries to it.

AsyncDNSResolver.Query defines the supported DNS query types, while AsyncDNSResolver.Options provides different options for configuring AsyncDNSResolver.

The current implementation relies on a DispatchQueue to process queries asynchronously. An implementation that makes use of an event loop might be better.

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Do not hesitate to get in touch, over on https://forums.swift.org/c/server.