Erlang DNS Server

Serve DNS authoritative responses... with Erlang.

This application consists of three main subsystems:

• m:erldns_zones The system responsible for loading and caching zone data.

• m:erldns_pipeline The system responsible for processing incoming DNS queries, including resolution and any extension thereof.

• m:erldns_listeners The system responsible for listening for incoming DNS queries. The system is designed to be able to listen on multiple ports and interfaces and supports both UDP and TCP, Unix network stack optimisations, and high parallelism.

There is also an Admin API for querying the current zone cache and for basic control.

Instrumentation

Telemetry is used to instrument the code.

All events are divided in the following namespaces:

• [erldns, pipeline | _] are triggered by the m:erldns_pipeline subsystem.
• [erldns, request | _] are triggered by the m:erldns_listeners subsystem.

Getting started

You can use this application as a standalone service or embedded into your OTP application. In both cases, you'll need to: configure it, and load zones.

Zones

Zones are loaded from JSON files in the priv/zones/ directory. The path is configured in erldns.config using the zones.path setting. For more details about zone file format and configuration, see priv/zones/ZONES.

Configuration

An example configuration file can be found in erldns.example.config. For more details, see the subsystems and the admin API documentation.

To get started, copy it into your own erldns.config and modify as needed.

Building

To build:

make

To start fresh:

make fresh
make

Running

Launch directly

overmind start

To get an interactive Erlang REPL

rebar3 shell

Build a distribution with and run the release

rebar3 release
_build/default/rel/erldns/bin/erldns foreground

Usage

DNS Queries

Here are some queries to try:

dig -p 8053 @127.0.0.1 example.com a
dig -p 8053 @127.0.0.1 example.com cname
dig -p 8053 @127.0.0.1 example.com ns
dig -p 8053 @127.0.0.1 example.com mx
dig -p 8053 @127.0.0.1 example.com txt
dig -p 8053 @127.0.0.1 example.com sshfp
dig -p 8053 @127.0.0.1 example.com soa
dig -p 8053 @127.0.0.1 example.com naptr
dig -p 8053 @127.0.0.1 -x 127.0.0.1 ptr

Admin API

The Admin API provides a RESTful HTTP interface for managing zones at runtime. By default, it listens on port 8083.

# List all zones
curl http://localhost:8083/

# Get zone details
curl http://localhost:8083/zones/example.com

# Get specific records
curl "http://localhost:8083/zones/example.com/records/example.com?type=A"

For complete documentation including authentication, TLS configuration, and extensibility options, see the Admin API documentation.

Performance

If you want to perform some benchmarks, see the benchmarking guide.

AXFR Support

AXFR zone transfers are not currently implemented. The current implementation (m:erldns_axfr) is a stub.

Platform notes

erldns adjusts its socket options and socket counts to the host platform,

Tests

To run automated tests:

make test

This runs the following:

• erlfmt
• Elvis linter
• xref
• dialyzer
• ExDoc
• Common Tests
• Coverage