iroh-topic-tracker 0.2.0

Iroh universal (gossip) topic tracker based on @Nuhvi's mainline draft proposal: https://github.com/bittorrent/bittorrent.org/pull/174.
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# iroh-topic-tracker

[![Crates.io](https://img.shields.io/crates/v/iroh-topic-tracker.svg)](https://crates.io/crates/iroh-topic-tracker)
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[![License](https://img.shields.io/badge/license-MIT%2FApache-blue.svg)](LICENSE-MIT)

Serverless, decentralized peer discovery for `iroh-gossip` topics using experimental **DHT Signed Peer Announcements**.

This crate uses the implementation of the experimental **Draft BEP** ([PR #174](https://github.com/bittorrent/bittorrent.org/pull/174)) for announcing and discovering cryptographically signed peer identities (Ed25519 public keys) on the Mainline DHT by [@Nuhvi](https://github.com/Nuhvi). This enables overlay networks like Iroh to discover peers without centralized trackers, utilizing signed announcements to verify identity before connection.

## Architecture

Instead of announcing IP addresses, peers announce their **EndpointId** (Ed25519 public key) signed with a timestamp. This allows for secure, trackerless discovery where connection establishment and NAT traversal are handled entirely by Iroh.

```mermaid
sequenceDiagram
    participant A as Node A
    participant DHT as Mainline DHT (Extended)
    participant B as Node B

    Note over A, B: Topic InfoHash = hash(topic)

    A->>DHT: announce_signed_peer(InfoHash, NodeId_A, Sig)
    B->>DHT: get_signed_peers(InfoHash)
    DHT-->>B: Returns: [(NodeId_A, Sig, Timestamp)]

    B->>B: Verify Signature & Timestamp
    B->>A: Iroh Direct Connection (Holepunch)
    A->>B: iroh-gossip takes over
```

## Features

- Ed25519 signature based discovery using `announce_signed_peer` / `get_signed_peers` extensions.
- Relies on public DHT nodes supporting the extension (e.g. Mainline DHT with PR #174, there are two atm to my knowledge + all iroh-topic-tracker participants).
- Prevents identity spoofing via Ed25519 signatures.

## Usage

Add to `Cargo.toml`:

```toml
[dependencies]
iroh = "1"
iroh-gossip = "0.101"
iroh-topic-tracker = "0.2.0"
```

Subscribe to a topic with automatic discovery:

```rust
use std::time::Duration;
use futures_lite::StreamExt;
use iroh::{Endpoint, SecretKey, protocol::Router};
use iroh_gossip::net::Gossip;

use iroh_topic_tracker::{TopicDiscoveryConfig, TopicDiscoveryExt};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let secret_key = SecretKey::generate(&mut rand::rng());

    let endpoint = Endpoint::builder()
        .secret_key(secret_key.clone())
        .bind()
        .await?;

    let gossip = Gossip::builder().spawn(endpoint.clone());

    let _router = Router::builder(endpoint.clone())
        .accept(iroh_gossip::ALPN, gossip.clone())
        .spawn();

    let topic_id = "testnet".as_bytes().to_vec();
    let config = TopicDiscoveryConfig::builder(endpoint)
        .max_peers_per_round(Some(5))
        .connection_timeout(Duration::from_secs(10))
        .build();

    println!("Starting subscription to topic...");
    let (sender, mut receiver, discovery_handle) = gossip
        .subscribe_with_discovery_joined(topic_id, vec![], config)
        .await?;

    println!("Subscribed to topic and joined the network.");

    println!("Broadcasting hello world...");
    sender
        .broadcast(format!("hello world {}", rand::random::<u32>()).into())
        .await?;


    discovery_handle.stop();

    Ok(())
}

```

## References

- [Draft BEP: DHT Signed Peer Announcements (PR #174)](https://github.com/bittorrent/bittorrent.org/pull/174)

## License

Dual-licensed under [Apache 2.0](LICENSE-APACHE.txt) and [MIT](LICENSE-MIT.txt).