zeronsd: a name service centered around the ZeroTier Central API

zeronsd provides names that are a part of ZeroTier Central's configured networks; once provided an IPv4-capable network it:

• Listens on the local interface joined to that network -- you will want to start one ZeroNS per ZeroTier network.
• Provides general DNS by forwarding all queries to /etc/resolv.conf resolvers that do not match the TLD, similar to dnsmasq.
• Tells Central to point all clients that have the "Manage DNS" settings turned on to resolve to it.
• Provides UDP, TCP, and DNS-over-TLS support (if configured with certificates).
• Finally, sets a provided TLD (.home.arpa is the default; recommended by IANA), as well as configuring A (IPv4) and AAAA (IPv6) records for:
  • Member IDs: zt-<memberid>.<tld> will resolve to the IPv4 & IPv6 addresses for them.
  • Names: if the names are compatible with DNS names, they will be converted as such: to <name>.<tld>.
    • Please note that collisions are possible and that it's up to the admin to prevent them.
  • It additionally includes PTR records for members, in all scenarios other than 6plane.
  • Wildcard everything mode: this mode (enabled by passing the -w flag) enables wildcards for all names under the TLD; for example my-site.zt-<memberid>.<tld> will resolve to the member's IP, and named hosts work the same way.

Installation

Zeronsd is only distributed as Docker images, hosted in the ZeroTier Docker Hub organization.

Development

If you want to hack on or build zeronsd yourself, the easiest way is to use Nix. If you do, you can get an environment ready to develop, test, or build/package the project just by running nix flake develop. Likewise, nix flake build will create a binary at result/bin/zeronsd.

just docker-build will use Docker to build a cross-platform image from your source directory. Note: there are multiple ways to configure Docker for multi-platform builds. Describing how to do so is beyond the scope of this README. (For those working on a Mac, there's an example colima template/config file in `examples/``).

Use just --list to see all of the development tasks currently available.

Usage

Setting ZEROTIER_CENTRAL_TOKEN in the environment (or providing the -t flag, which points at a file containing this value) is required. You must be able to administer the ZeroTier network to use zeronsd with it. Also, running as root is required as many client resolvers do not work over anything but port 53. Your zeronsd instance will listen on both udp and tcp, port 53.

Bare commandline

Tip: running sudo? Pass the -E flag to import your current shell's environment, making it easier to add the ZEROTIER_CENTRAL_TOKEN, or use the -t flag to avoid the environment entirely.

zeronsd start <network id>

Configuration

zeronsd as of v0.3 takes a configuration file via the -c flag which correlates to all of the command-line options. --config-type corresponds to the format of the configuration file: yaml is the default, and json and toml are also supported.

The configuration directives are as follows:

• domain: (string) will set a TLD for your records; the default is home.arpa.
• log_level: (string) will tweak the log level in use. Default is info, but offerings are [off, trace, debug, error, warn, info]. Please note at lower log levels there can be a lot of output!
• hosts: (string) will parse a file in /etc/hosts format and append it to your records.
• secret: (string) path to authtoken.secret which is needed to talk to ZeroTier on localhost. You can provide this file with this argument, but it is auto-detected on multiple platforms including Linux, OS X and Windows.
• token: (string) path to file containing your ZeroTier Central token.
• wildcard: (bool) Enables wildcard mode, where all member names get a wildcard in this format: *.<name>.<tld>; this points at the member's IP address(es).

Running as a service

This behavior is currently only supported on Linux and Mac OS X; we will accept patches for other platforms.

The zeronsd supervise and zeronsd unsupervise commands can be used to manipulate systemd unit files related to your network. For the supervise case, simply pass the arguments you would normally pass to start and it will generate a unit from it.

Example:

# to enable
zeronsd supervise -t ~/.token -f /etc/hosts -d mydomain 36579ad8f6a82ad3
# generates systemd unit file named /lib/systemd/system/zeronsd-36579ad8f6a82ad3.service
systemctl daemon-reload
systemctl enable zeronsd-36579ad8f6a82ad3.service && systemctl start zeronsd-36579ad8f6a82ad3.service

# to disable
systemctl disable zeronsd-36579ad8f6a82ad3.service && systemctl stop zeronsd-36579ad8f6a82ad3.service
zeronsd unsupervise 36579ad8f6a82ad3
systemctl daemon-reload

Logging

Set ZERONSD_LOG or RUST_LOG to various log levels or other parameters according to the env_logger specification for more.

Docker

Running in docker is a little more complicated. You must be able to have a network interface you can import (joined a network) and must be able to reach localhost:9999 on the host. At this time, for brevity's sake we are recommending running with --net=host until we have more time to investigate a potentially more secure solution.

You also need to mount your authtoken.secret, which we use to talk to zerotier-one

docker run --net host -it \
  -v /var/lib/zerotier-one/authtoken.secret:/authtoken.secret \
  -v <token file>:/token.txt \
  zeronsd:alpine start -s /authtoken.secret -t /token.txt \
  <network id>

Other notes

You must have already joined a network and obviously, zerotier-one should be running!

It should print some diagnostics after it has talked to your zerotier-one instance to figure out what IP to listen on. After that it should communicate with the central API and set everything else up automatically.

Flags for the start and supervise subcommands:

• -d <tld> will set a TLD for your records; the default is home.arpa.
• -f <hosts file> will parse a file in /etc/hosts format and append it to your records.
• -s <secret file> path to authtoken.secret which is needed to talk to ZeroTier on localhost. You can provide this file with this argument, but it is auto-detected on multiple platforms including Linux, OS X and Windows.
• -t <central token file> path to file containing your ZeroTier Central token.
• -w Enables wildcard mode, where all member names get a wildcard in this format: *.<name>.<tld>; this points at the member's IP address(es).
• -v Enables verbose logging. Repeat for more verbosity.
• -V prints the version.

TTLs

Records currently have a TTL of 60s, and Central's records are refreshed every 30s through the API. I felt this was a safer bet than letting timeouts happen.

Per-Interface DNS resolution

OS X and Windows users get this functionality by default, so there is no need for it. Please note at this point in time, however, that PTR resolution does not properly work on either platform. This is a defect in ZeroTier and should be corrected soon.

Make sure the enable "Allow DNS" in the ZeroTier client through menubar app or with zerotier-cli set $NETWORK_ID allowDNS=1.

Linux users are strongly encouraged to use systemd-networkd along with systemd-resolved to get per-interface resolvers that you can isolate to the domain you want to use. If you'd like to try something that can assist with getting you going quickly, check out the zerotier-systemd-manager repository.

BSD systems still need a bit of work; work that we could really use your help with if you know the lay of the land on your BSD of choice. Set up an issue if this interests you.

Acknowledgements

ZeroNS demands a lot out of the trust-dns toolkit and I personally am grateful such a library suite exists. It made my job very easy.

License

BSD 3-Clause

Author

Erik Hollensbe github@hollensbe.org ZeroTier Engineering