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relay

This crate houses a minimalistic STUN & TURN server.

Features

We aim to support the following feature set:

  • STUN binding requests
  • TURN allocate requests
  • TURN refresh requests
  • TURN channel bind requests
  • TURN channel data requests

Relaying of data through other means such as DATA frames is not supported.

Building

You can build the relay using: cargo build --release --bin firezone-relay

You should then find a binary in target/release/firezone-relay.

Running

The Firezone Relay supports Linux only. To run the Relay binary on your Linux host:

  1. Generate a new Relay token from the "Relays" section of the admin portal and save it in your secrets manager.
  2. Ensure the FIREZONE_TOKEN=<relay_token> environment variable is set securely in your Relay's shell environment. The Relay expects this variable at startup.
  3. Now, you can start the Firezone Relay with:
firezone-relay

To view more advanced configuration options pass the --help flag:

firezone-relay --help

Ports

By default, the relay listens on port udp/3478. This is the standard port for STUN/TURN. Additionally, the relay needs to have access to the port range 49152 - 65535 for the allocations.

Portal Connection

When given a token, the relay will connect to the Firezone portal and wait for an init message before commencing relay operations.

Design

The relay is designed in a sans-IO fashion, meaning the core components do not cause side effects but operate as pure, synchronous state machines. They take in data and emit commands: wake me at this point in time, send these bytes to this peer, etc.

This allows us to very easily unit-test all kinds of scenarios because all inputs are simple values.

The main server runs in a single task and spawns one additional task for each allocation. Incoming data that needs to be relayed is forwarded to the main task where it gets authenticated and relayed on success.