iroh-topic-tracker

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) for announcing and discovering cryptographically signed peer identities (Ed25519 public keys) on the Mainline DHT by @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.

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

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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:

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

Subscribe to a topic with automatic discovery:

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)

License

Dual-licensed under Apache 2.0 and MIT.