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Synchronize your DNS to multiple providers from a simple DSL
f1b30a1a04
## Summary This PR adds a new domain modifier `IGNORE_EXTERNAL_DNS()` that automatically detects and ignores DNS records managed by Kubernetes [external-dns](https://github.com/kubernetes-sigs/external-dns) controller. **Related Issue:** This addresses the feature request discussed in StackExchange/dnscontrol#935 (Idea: Ownership system), where @tlimoncelli indicated openness to accepting a PR for this functionality. ## Problem When running DNSControl alongside Kubernetes external-dns, users face a challenge: - **external-dns** dynamically creates DNS records based on Kubernetes Ingress/Service resources - Users cannot use `IGNORE()` because they cannot predict which record names external-dns will create - Using `NO_PURGE()` is too broad - it prevents DNSControl from cleaning up any orphaned records The fundamental issue is that `IGNORE()` requires static patterns known at config-time, but external-dns creates records dynamically at runtime. ## Solution `IGNORE_EXTERNAL_DNS()` solves this by detecting external-dns managed records at runtime: ```javascript D("example.com", REG_CHANGEME, DnsProvider(DSP_MY_PROVIDER), IGNORE_EXTERNAL_DNS(), // Automatically ignore external-dns managed records A("@", "1.2.3.4"), CNAME("www", "@") ); ``` ### How It Works external-dns uses a TXT record registry to track ownership. For each managed record, it creates a TXT record like: - `a-myapp.example.com` → TXT containing `heritage=external-dns,external-dns/owner=...` - `cname-api.example.com` → TXT containing `heritage=external-dns,external-dns/owner=...` This PR: 1. Scans existing TXT records for the `heritage=external-dns` marker 2. Parses the TXT record name prefix (e.g., `a-`, `cname-`) to determine the managed record type 3. Automatically adds those records to the ignore list during diff operations ## Changes | File | Purpose | |------|---------| | `models/domain.go` | Add `IgnoreExternalDNS` field to DomainConfig | | `pkg/js/helpers.js` | Add `IGNORE_EXTERNAL_DNS()` JavaScript helper | | `pkg/diff2/externaldns.go` | Core detection logic for external-dns TXT records | | `pkg/diff2/externaldns_test.go` | Unit tests for detection logic | | `pkg/diff2/handsoff.go` | Integrate external-dns detection into handsoff() | | `pkg/diff2/diff2.go` | Pass IgnoreExternalDNS flag to handsoff() | | `commands/types/dnscontrol.d.ts` | TypeScript definitions for IDE support | | `documentation/.../IGNORE_EXTERNAL_DNS.md` | User documentation | ## Design Philosophy This follows DNSControl's pattern of convenience builders (like `M365_BUILDER`, `SPF_BUILDER`, `DKIM_BUILDER`) that make complex operations simple. Just as those builders abstract away implementation details, `IGNORE_EXTERNAL_DNS()` abstracts away the complexity of detecting external-dns managed records. ## Testing All unit tests pass: ``` go test ./pkg/diff2/... -v # Tests detection logic go test ./pkg/js/... # Tests JS helpers go build ./... # Builds successfully ``` ## Caveats Documented - Only supports TXT registry (the default for external-dns) - Requires external-dns to use default naming conventions - May need updates if external-dns changes its registry format --------- Co-authored-by: Tom Limoncelli <6293917+tlimoncelli@users.noreply.github.com> |
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DNSControl
DNSControl is a system for maintaining DNS zones. It has two parts: a domain specific language (DSL) for describing DNS zones plus software that processes the DSL and pushes the resulting zones to DNS providers such as Route53, Cloudflare, and Gandi. It can send the same DNS records to multiple providers. It even generates the most beautiful BIND zone files ever. It runs anywhere Go runs (Linux, macOS, Windows). The provider model is extensible, so more providers can be added.
Currently supported DNS providers:
- AdGuard Home
- Akamai Edge DNS
- AutoDNS
- AWS Route 53
- AXFR+DDNS
- Azure DNS
- Azure Private DNS
- BIND
- Bunny DNS
- CentralNic Reseller (CNR) - formerly RRPProxy
- Cloudflare
- ClouDNS
- CSC Global (Experimental)
- deSEC
- DigitalOcean
- DNS Made Easy
- DNSimple
- Domainnameshop (Domeneshop)
- Exoscale
- Fortigate
- Gandi
- Gcore
- Google DNS
- Hetzner
- HEXONET
- hosting.de
- Huawei Cloud DNS
- Hurricane Electric DNS
- INWX
- Joker
- Linode
- Loopia
- LuaDNS
- Microsoft Windows Server DNS Server
- Mythic Beasts
- Name.com
- Namecheap
- Netcup
- Netlify
- NS1
- Oracle Cloud
- OVH
- Packetframe
- Porkbun
- PowerDNS
- Realtime Register
- RWTH DNS-Admin
- Sakura Cloud
- SoftLayer
- TransIP
- Vercel
- Vultr
Currently supported Domain Registrars:
- AWS Route 53
- CentralNic Reseller (CNR) - formerly RRPProxy
- CSC Global
- DNSimple
- DNSOVERHTTPS
- Dynadot
- easyname
- Gandi
- HEXONET
- hosting.de
- Internet.bs
- INWX
- Loopia
- Name.com
- Namecheap
- OpenSRS
- OVH
- Porkbun
- Realtime Register
At Stack Overflow, we use this system to manage hundreds of domains and subdomains across multiple registrars and DNS providers.
You can think of it as a DNS compiler. The configuration files are written in a DSL that looks a lot like JavaScript. It is compiled to an intermediate representation (IR). Compiler back-ends use the IR to update your DNS zones on services such as Route53, Cloudflare, and Gandi, or systems such as BIND.
An Example
dnsconfig.js:
// define our registrar and providers
var REG_NAMECOM = NewRegistrar("name.com");
var r53 = NewDnsProvider("r53")
D("example.com", REG_NAMECOM, DnsProvider(r53),
A("@", "1.2.3.4"),
CNAME("www","@"),
MX("@",5,"mail.myserver.com."),
A("test", "5.6.7.8")
)
Running dnscontrol preview will talk to the providers (here name.com as registrar and route 53 as the dns host), and determine what changes need to be made.
Running dnscontrol push will make those changes with the provider and my dns records will be correctly updated.
The easiest way to run DNSControl is to use the Docker container:
docker run --rm -it -v "$(pwd):/dns" ghcr.io/stackexchange/dnscontrol preview
See Getting Started page on documentation site to get started!
Benefits
- Less error-prone than editing a BIND zone file.
- More reproducible than clicking buttons on a web portal.
- Easily switch between DNS providers: The DNSControl language is vendor-agnostic. If you use it to maintain your DNS zone records, you can switch between DNS providers easily. In fact, DNSControl will upload your DNS records to multiple providers, which means you can test one while switching to another. We've switched providers 3 times in three years and we've never lost a DNS record.
- Apply CI/CD principles to DNS! At StackOverflow we maintain our DNSControl configurations in Git and use our CI system to roll out changes. Keeping DNS information in a VCS means we have full history. Using CI enables us to include unit-tests and system-tests. Remember when you forgot to include a "." at the end of an MX record? We haven't had that problem since we included a test to make sure Tom doesn't make that mistake... again.
- Adopt (GitOps) PR-based updates. Allow developers to send updates as PRs, which you can review before you approve.
- Variables save time! Assign an IP address to a constant and use the variable name throughout the file. Need to change the IP address globally? Just change the variable and "recompile."
- Macros! Define your SPF records, MX records, or other repeated data once and re-use them for all domains.
- Control Cloudflare from a single source of truth. Enable/disable Cloudflare proxying (the "orange cloud" button) directly from your DNSControl files.
- Keep similar domains in sync with transforms and other features. If one domain is supposed to be a filtered version of another, this is easy to set up.
- It is extendable! All the DNS providers are written as plugins. Writing new plugins is very easy.
Installation
DNSControl can be installed via packages for macOS, Linux and Windows, or from source code. See the official instructions.
Via GitHub Actions (GHA)
See dnscontrol-action or gacts/install-dnscontrol.
Deprecation warnings (updated 2025-11-21)
- REV() will switch from RFC2317 to RFC4183 in v5.0. This is a breaking change. Warnings are output if your configuration is affected. No date has been announced for v5.0. See https://docs.dnscontrol.org/language-reference/top-level-functions/revcompat
- NAMEDOTCOM, OPENSRS, and SOFTLAYER need maintainers! These providers have no maintainer. Maintainers respond to PRs and fix bugs in a timely manner, and try to stay on top of protocol changes. Interested in being a hero and adopting them? Contact tlimoncelli at stack overflow dot com.
More info at our website
The website: https://docs.dnscontrol.org/
The getting started guide: https://docs.dnscontrol.org/getting-started/getting-started
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