iroh 0.98.0 - Getting back to traversing NATs

Welcome to a new release of iroh, a modular networking stack in Rust, for building direct connections between devices.

This release is focused on NAT traversal reliability. In 0.96 we flagged a known regression where holepunching wasn't re-triggered on network changes. Through 0.96 and 0.97 a few more subtle regressions crept in alongside multipath, QUIC-NAT-Traversal, and the noq split. Connections that used to punch through would sometimes sit on the relay. Paths that used to recover across a Wi-Fi to LTE switch would stall.

Most of the work for this landed in noq 0.18, with a matching set of fixes on the iroh side. We also built out a much bigger patchbay test matrix that now reproduces the scenarios that were breaking.

This release also introduces pluggable crypto backends, rate limiting hooks in the router, and a new relay protocol version that exercises our version-negotiation machinery.

🕳️ Getting back to traversing NATs

If you've been running iroh in environments that need NAT traversal, the last two releases probably felt worse than 0.95. This release fixes most of these issues we have observed.

Most of the work landed in noq 0.18, which has a big batch of multipath and NAT traversal fixes. A few highlights:

• Abandoned paths are now handled correctly. We were ignoring ACKs for abandoned paths (noq#519), not accepting remote PATH_ABANDON for the last path (noq#522), and scheduling tail-loss probes on paths that were already gone (noq#562). All fixed.
• PTO backoff no longer stalls connections. PTO is now capped at 2 seconds post-handshake (noq#523) and gets reset for recoverable paths on a network change (noq#545), so a brief outage doesn't push the connection into a multi-second sleep.
• NAT traversal retries properly. Off-path probes are retried and stale CIDs retired (noq#524), existing paths are revalidated during NAT traversal rounds (noq#531), and the server sends NAT traversal probes with the active CID (noq#575). Holepunching frames no longer get stuck behind stream data (noq#540).
• Tail-loss probes are always ack-eliciting (noq#561). This was a subtle source of connections that looked alive but weren't making progress.

On the iroh side we also kept busy:

• Faster relay health check after a network change (#4041). Instead of waiting up to 5 seconds for the next scheduled ping, we now send an immediate RTT-based ping (3x last RTT, min 500ms). If the relay is broken, we now detect it faster and reconnect.
• Holepunching after network changes restarts correctly again (#3928).
• Exponential backoff when polling for the default route after a network change (#4039), instead of hammering the OS.
• Path idle timeouts are tuned to match the relay and direct-path characteristics (#4038).

🔐 Pluggable Crypto Backends

iroh has historically pulled in ring as its TLS crypto provider. That's fine for most users. It's a problem if you're on a platform where ring doesn't build, if your org mandates a FIPS-certified backend like aws-lc-rs, or if you just don't want to ship ring at all.

0.98 makes the crypto provider pluggable. There are two new feature flags:

• ring (default): use rustls's ring provider.
• aws-lc-rs: use rustls's aws-lc-rs provider.

Or you can turn both off and wire in your own:

let endpoint = Endpoint::builder(presets::N0)
    .crypto_provider(my_custom_provider)
    .bind()
    .await?;

If neither feature flag is enabled and you don't call crypto_provider, bind() will return an error telling you what you forgot. If both features are enabled, we default to ring.

We also added two new presets alongside presets::N0:

• presets::Minimal: the minimum required options on the builder (only available with ring or aws-lc-rs enabled).
• presets::Empty: replaces the old Endpoint::empty_builder(), which has been removed.

Checkout PR #3992 for more details.

🚦 Rate Limiting in the Router

If you run a single iroh endpoint that's exposed to the world (a public irpc service, an n0des node, anything where arbitrary clients can connect), you want to be able to shed load before the connection handshake completes. 0.98 adds hooks for that.

For more on why early rejection is cheap at the QUIC layer, see How QUIC rejects garbage packets and for measurements of the filters in this release against a real endpoint, see QUIC packet rejection in practice.

The router now supports optional connection filters that run at several points in the connection lifecycle: by remote address, by endpoint ID (for relay connections), and by ALPN. Each stage can accept, reject, retry, or ignore the incoming connection.

Router::builder(endpoint)
    .filter(|conn| {
        if is_banned(conn.remote_addr()) {
            ConnectionAction::Ignore
        } else {
            ConnectionAction::Accept
        }
    })
    .spawn()

Rejecting early is much cheaper than closing the connection after it's established. Benchmarks on the PR show ~30x throughput for address-based rejection vs. accepting and closing. For relay connections, rejecting by endpoint ID is the cheapest option since we get that information before the handshake completes.

Checkout PR #3951 for more details.

📡 Relay Protocol v2

The relay protocol now supports version negotiation, and we're using it: this release ships iroh-relay-v2. The wire changes are minor. There's a new Status frame that replaces the old Health frame with a binary-encoded extensible payload, and unknown frames are now ignored rather than erroring out. The real goal here was to exercise the version-negotiation machinery end-to-end. Old clients can talk to new relays, and new clients can talk to old relays.

Next time we need to extend the relay protocol, the path is already paved.

Checkout PR #3955 for more details.

⭐ Other Notable Changes

• Configurable external addresses (#4098). If you already know your endpoint's public address (e.g. from a reverse proxy or platform metadata), you can now tell the endpoint about it directly instead of relying on discovery.
• Deprecated IPv6 addresses are no longer advertised (#4106). Deprecated IPv6 addresses (in the RFC 4862 sense) aren't meant to be used for new connections, so we no longer include them in NAT traversal advertisements.
• pkarr is now vendored as iroh-dns (#4026). We only ever used the DNS-record encoding bits, so we inlined those into a new iroh-dns crate and dropped the third-party pkarr dependency. Smaller dep tree, no behavioural change for most users.
• More metrics on the relay server (#4085). Useful if you run your own relay and want to monitor it.

⚠️ Breaking Changes

• iroh
  • changed
    • iroh::address_lookup::ConcurrentAddressLookup renamed to iroh::address_lookup::AddressLookupServices, and no longer implements the AddressLookup trait; owned by Endpoint, used via its inherent methods (#4130)
    • iroh::Endpoint::address_lookup now returns Result<&AddressLookupServices, EndpointError> (#4130)
    • AddressLookupServices::resolve now returns impl Stream<Item = Result<Item, AddressLookupFailed>> instead of Option<BoxStream<...>> (#4130)
    • iroh::address_lookup::Error is now a struct; existing constructor methods unchanged (#4126)
    • iroh::endpoint::ConnectWithOptsError::NoAddress { source } - source is now AddressLookupFailed, which can carry errors from all failed services (#4126)
    • iroh::DirectAddrType is now #[non_exhaustive] (#4107)
    • iroh::address_lookup::mdns::DiscoveryEvent is now #[non_exhaustive] (#4107)
    • iroh::address_lookup::pkarr::dht::Builder::client(pkarr::Client) replaced by dht_builder(mainline::DhtBuilder) (#4026)
    • PkarrError::PublicKey source type is now iroh_base::KeyParsingError (#4026)
    • PkarrError::Verify source type is now iroh_dns::pkarr::SignedPacketVerifyError (#4026)
  • added
    • iroh::endpoint::Builder::crypto_provider (#3992)
  • removed
    • ConcurrentAddressLookup::empty(), ConcurrentAddressLookup::from_services() - use AddressLookupServices::default() with add / add_boxed instead (#4130)
    • impl<T: IntoIterator<Item = Box<dyn AddressLookup>>> From<T> for ConcurrentAddressLookup (#4130)
    • Endpoint::empty_builder - use Endpoint::builder(presets::Empty) or Endpoint::builder(presets::Minimal) instead (#3992)
    • Builder::pkarr_relay(Url), Builder::n0_dns_pkarr_relay(), Builder::dht(bool) on DHT address lookup - the DHT lookup only uses the Mainline DHT; use PkarrPublisher for relay publishing (#4026)
  • behavioural
    • If neither the ring nor aws-lc-rs feature flag is enabled and you don't call crypto_provider, Builder::bind() will return an error (#3992)
• iroh-base
  • changed
    • iroh_base::SecretKey::generate() no longer takes an Rng generic argument; uses rand::rng() internally. Use SecretKey::from_bytes if you need a specific RNG (#4075)
    • iroh_base::key::KeyDecodeError - variants changed, no longer embeds third-party error types, now #[non_exhaustive] (#4073)
  • renamed
    • iroh_base::CustomAddr::as_vec -> iroh_base::CustomAddr::to_vec (#4074)
• iroh-relay
  • changed
    • iroh_relay::server::client::Config - new field protocol_version: ProtocolVersion (#3955)
    • iroh_relay::protos::relay::RelayToClientMsg - new Status(Status) variant; Health variant deprecated (#3955)
    • iroh_relay::server::http_server::RelayService no longer implements hyper::Service - use RelayServiceWithNotify (via RelayServiceWithNotify::new) (#4083)
    • iroh_relay::server::http_server::RelayService::handle_connection - new establish_timeout argument (#4083)
    • iroh_relay::PingTracker::new - default_timeout parameter renamed to max_timeout (#4041)
    • iroh_relay::RelayConfig, RelayQuicConfig, protos::relay::{RelayToClientMsg, ClientToRelayMsg}, protos::common::FrameType, server::Metrics, server::RelayMetrics are now #[non_exhaustive]; use constructors or default() instead of struct literals (#4107)
    • iroh_relay::endpoint_info::EndpointIdExt::from_z32 return type is now Result<EndpointId, iroh_base::KeyParsingError> (#4026)
    • iroh_relay::endpoint_info::EndpointInfo::{from_pkarr_signed_packet, to_pkarr_signed_packet} now use iroh_dns::pkarr::SignedPacket (#4026)
    • iroh_relay::endpoint_info::EndpointInfo::from_txt_lookup signature relaxed to impl Iterator<Item = impl Display>; no longer #[cfg(not(wasm_browser))]-gated (#4026)
    • iroh_relay::endpoint_info::EncodingError::FailedBuildingPacket source type is now iroh_dns::pkarr::SignedPacketBuildError (#4026)
  • renamed
    • iroh_relay::PingTracker::default_timeout() -> PingTracker::max_timeout() (#4041)
  • added
    • iroh_relay::http::ProtocolVersion (#3955)
    • iroh_relay::PingTracker::new_ping_with_timeout(timeout), PingTracker::ping_timeout() (#4041)
  • removed
    • iroh_relay::http::RELAY_PROTOCOL_VERSION - use ProtocolVersion::V1.to_str() for the old constant value (#3955)
    • iroh_relay::endpoint_info::DecodingError - handle iroh_base::KeyParsingError instead (#4026)
    • iroh_relay::endpoint_info::EncodingError::InvalidTxtEntry variant (#4026)
• iroh-dns (new crate)
  • added
    • new crate containing SignedPacket, Timestamp, EndpointIdExt, TxtAttrs, IrohAttr, IROH_TXT_NAME, ParseError, EncodingError (#4026)
• Build and features
  • changed
    • cargo feature address-lookup-pkarr-dht now pulls in mainline instead of pkarr/dht + pkarr/relays (#4026)
    • z32 and pkarr are no longer direct dependencies of iroh, iroh-relay, or iroh-dns-server; downstream users depending on them transitively must depend on them explicitly (#4026)

🎉 The Road to 1.0

Reliability fixes aren't glamorous, but they're what makes the stack trustworthy enough to build on. NAT traversal is back on solid ground, and the patchbay matrix is there to keep it that way. On to the remaining 1.0 rough edges.

But wait, there's more!

Many bugs were squashed, and smaller features were added. For all those details, check out the full changelog: https://github.com/n0-computer/iroh/releases/tag/v0.98.0.

If you want to know what is coming up, check out the v0.99.0 milestone, and if you have any wishes, let us know about the issues! If you need help using iroh or just want to chat, please join us on discord! And to keep up with all things iroh, check out our Twitter, Mastodon, and Bluesky.