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;
• a WireGuard data plane, in userspace: its own key per network, deterministic IPv6 overlay addressing, real tunnels carried over iroh, and address ownership enforced rather than believed;
• a command line agent, tsunagi.

What it deliberately does not do

Not implemented, and not pretended to be: 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. The WireGuard plugin's own limits, including that its system backend is Linux-only, are in docs/wireguard.md.

Control and data are separated logically, not physically. Both ride on iroh, on different ALPNs and different connections, so the data plane inherits iroh's hole punching and relay fallback instead of reimplementing them — while the control protocol still knows nothing about packets and can keep a different transport underneath it later. Filtering user traffic remains 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.
• WireGuard runs in userspace (boringtun): no kernel module and no wg tool. Only creating a real network interface needs CAP_NET_ADMIN, and --no-tun skips even that.

Trying it on two machines

On the first machine:

cargo build --release
./target/release/tsunagi secret          # prints tsn1...; share it privately
./target/release/tsunagi doctor          # what this host can and cannot do

./target/release/tsunagi up --network lab --secret "$SECRET" --wireguard

It prints its endpoint id and then waits. On the second machine, pass that id:

./target/release/tsunagi up --network lab --secret "$SECRET" --wireguard \
  --peer <endpoint-id-from-the-first-machine>

Within a few seconds both print something like:

  + peer b47c958462 connected over Direct rtt=Some(4.5ms)
  + data link to b47c958462 for wireguard: Direct via Ip(…), datagram 1382

--- status ---
control: 1 peer(s), 0 dial failure(s), 0 handshake failure(s)
wireguard: tsunkkcp43lmdje on fd15:1d9e:fa21:f201:…/64 mtu 1100, 1/1 tunnel(s) established
  4jO4kx9Z fd15:1d9e:fa21:f201:… handshake 3s ago tx=0 rx=0 dropped=0 path=Direct via Ip(…)

1/1 tunnel(s) established means a real WireGuard handshake completed. Then ping6 the peer's overlay address.

Notes:

• Only one side needs --peer; the link is bidirectional. Peer discovery beyond this manual bootstrap is future work.
• The default --transport n0 uses iroh's public address lookup and relays, so two machines behind NAT find each other. --transport local keeps everything on the local network.
• Without CAP_NET_ADMIN, add --no-tun: the mesh, the data links and the WireGuard handshakes all still run and are visible in the status output, only traffic does not reach the operating system. That is the quickest way to confirm the network forms.
• Run as root (or grant CAP_NET_ADMIN) to get a real interface.

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 are also two runnable demos, which are demos and not substitutes for the tests:

cargo run --example two_agents       # control plane only
cargo run --example wireguard_mesh   # a WireGuard overlay carrying a real packet

Both run with no privileges and change nothing on the host.

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

The WireGuard plugin keeps its own keys in its own wireguard.sqlite, wherever its configuration points, because plugin keys are neither the iroh identity nor the network secret.

The command line agent puts everything under the platform's per-user directories by default; --state-dir and --cache-dir override them.

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/wireguard.md — the WireGuard plugin: overlay addressing, announcements, backends, reconciliation.
• 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.