https://github.com/zevv/janet-dns

Asynchronous DNS resolver library for the Janet language.
https://github.com/zevv/janet-dns

async dns janet resolver

Last synced: about 1 month ago
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Asynchronous DNS resolver library for the Janet language.

• Host: GitHub
• URL: https://github.com/zevv/janet-dns
• Owner: zevv
• License: mit
• Created: 2023-05-13T13:46:49.000Z (over 1 year ago)
• Default Branch: master
• Last Pushed: 2023-05-14T20:33:18.000Z (over 1 year ago)
• Last Synced: 2024-12-16T01:37:24.180Z (about 1 month ago)
• Topics: async, dns, janet, resolver
• Language: Janet
• Homepage:
• Size: 20.5 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        

## Introduction

This is a proof-of-concept async DNS resolver library for the Janet programming

language. This code is not at all production ready, as it only implements the

happy path and has virtually no error handling.

## Description

Address resolution is a complicated task that is usually performed by the libc

standard library using `getaddrinfo()` or similar calls. The Janet standard

library also uses this call for resolving when calling `net/address`; this can

be problematic because `getaddrinfo()` can potentially block for several

seconds, effectively blocking the current Janet thread and it's event loop as

well.

This library implements a very simply DNS resolver that does not rely on the

libc standard library functions; instead it communicates directly with DNS

servers to perform the lookup, allowing for proper async behavior that will not

block the event loop.

Note that the resolving behavior of this library is by no means standard and

might differ from the underlying libc implementation; also, it will only use

DNS for resolution and does not implement any other source like a local hosts

file.

## Example

```janet

(import ./resolver)

# Create resolver instance

(def res (resolver/new "8.8.4.4"))

# Call the :resolve method to perform a DNS lookup

(defn test[]

  (ev/sleep 0.1)

  (pp (:resolve res "nyt.com"))

  (ev/sleep 0.1)

  (pp (:resolve res "google.com" :AAAA)))

(ev/call test)

```

## TODO and Open questions

- Improve error handling

- Acquire DNS server IPs from system resolver configuration

- Cache resceived answers with proper time-to-live

- Implement TCP/53

- Primary/secondary server fallback