tsunagi/README.md

tsunagi

A proof-of-concept Rust library for small private mesh networks — a handful of friends, home machines, a few servers. Units to dozens of participants, not thousands.

The end user configures exactly two things:

network_name
secret          # one shared secret; "password" and "secret" mean the same value

From those, every agent independently derives the same network space. There is no central server, no network owner with special powers, no registration and no majority vote. Anyone who knows the parameters can join; nobody has to trust anybody else.

What this proof of concept actually does

A working library with real iroh connections and integration tests:

• persistent device identity stored in SQLite, stable across restarts;
• several independent networks at once in one agent;
• deterministic network identity derived from name + secret;
• candidates supplied by a replaceable discovery component;
• real iroh connections plus an explicit mutual proof of network membership;
• a small versioned control protocol: handshake, hostname/capability announcement, ping/pong;
• automatic reconnect with bounded exponential backoff and jitter;
• status snapshots, an event stream and honest diagnostics;
• configuration restored after a restart;
• correct behaviour when the disposable cache is missing or corrupt.

What it deliberately does not do

Not implemented, and not pretended to be: WireGuard or any other IP plugin, Mainline DHT, DNS, routing through intermediate participants, a full CRDT, dynamically loaded plugins, a system service, a complete CLI, or a local control socket. Snapshot synchronisation and signed revocations are designed for but not implemented — see docs/sync-model.md.

Only control messages travel over iroh. User IP traffic is not tunnelled through it. Filtering user traffic is the operating system's and the user's responsibility, not this library's.

Requirements

• Rust 1.91 or newer (iroh 1.2 requires it) (edition 2024). Pinned dependencies in Cargo.lock.
• No internet, no DHT, no public relay, no administrator rights and no changes to OS network settings are needed to build or test.

Checks

cargo fmt --all -- --check
cargo clippy --locked --workspace --all-targets -- -D warnings
cargo test --locked --workspace --all-targets

The whole suite runs offline on loopback. Set TSUNAGI_TEST_LOG=tsunagi=debug to see agent logs while a test runs.

There is also a runnable demo, which is a demo and not a substitute for the tests:

cargo run --example two_agents

Usage

use std::sync::Arc;
use tsunagi::config::{AgentConfig, StoragePaths, TransportPolicy};
use tsunagi::discovery::SharedMemoryDiscovery;
use tsunagi::identity::{NetworkName, NetworkSecret};
use tsunagi::proto::ControlMessage;
use tsunagi::{Agent, Result};

// The library never starts a runtime, installs a logger, handles signals,
// forks, or calls process::exit. The binary owns all of that.
#[tokio::main]
async fn main() -> Result<()> {
    let config = AgentConfig::new(StoragePaths::user_default()?)
        .with_transport(TransportPolicy::N0Defaults)
        .with_discovery(Arc::new(SharedMemoryDiscovery::new()));

    let agent = Agent::spawn(config).await?;

    let name = NetworkName::new("kitchen-table")?;
    let secret = NetworkSecret::generate();       // 32 random bytes
    println!("share this: {}", secret.encode().as_str());

    let network = agent.join_network(&name, &secret).await?;

    let mut events = agent.subscribe();
    tokio::spawn(async move {
        while let Ok(event) = events.recv().await {
            println!("{event:?}");
        }
    });

    for peer in agent.network_status(network).await?.connected_peers() {
        agent
            .send(network, peer, ControlMessage::Ping { seq: 1, payload: vec![] })
            .await?;
    }

    agent.shutdown().await;
    Ok(())
}

TransportPolicy::LocalOnly is the default, so a plain AgentConfig::new never reaches the internet by accident. Opt into DirectOnly or N0Defaults explicitly.

Storage

Two physically separate SQLite files, placed wherever the library's configuration says (StoragePaths). A future system service supplies its own paths; tests always use temporary directories.

file	holds	when damaged
state.sqlite	device identity, network configuration, hostname	clear error, never reset
cache.sqlite	address hints and other recoverable data	discarded and recreated

One state directory belongs to one live agent, enforced with a real OS file lock rather than an existence check.

Documentation

• docs/architecture.md — module boundaries and runtime.
• docs/protocol.md — identity derivation, framing, handshake.
• docs/sync-model.md — the planned signed-state model and what is deliberately not built yet.
• docs/threat-model.md — threat model and known limits.
• docs/testing.md — what the suite covers and what it does not.
• AGENTS.md — rules for anyone (human or agent) changing this repo.

Security in one paragraph

Membership is proved by an HMAC over a transcript keyed by a value derived from the shared secret, bound to the specific iroh connection through the TLS exporter, to the network id, to both endpoint identities and to distinct role labels. This targets high-entropy secrets: there is no PAKE here, so a short human passphrase is guessable offline by anyone who can reach the handshake. Anyone who knows the secret is a full participant and can create many identities. Read docs/threat-model.md before relying on any of this.

Licence

MIT OR Apache-2.0.