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Optional peer discovery and NAT hole-punching path gated behind a new
`nostr-discovery` cargo feature. Nodes publish signed overlay endpoint
adverts to public Nostr relays, consume peer adverts to populate
fallback dial addresses, and use STUN-assisted UDP hole punching with
NIP-59 gift-wrap offer/answer signaling to establish direct UDP paths
between NATed peers. Once a punched socket is up, it is handed into
the existing FIPS UDP transport and the standard Noise/FMP session
stack takes over unchanged.
The cargo feature is in the default feature set
(`default = ["nostr-discovery"]`) so stock builds include it; a
build that explicitly disables default features (or selects a
feature set without `nostr-discovery`) does not link the nostr /
nostr-sdk crates and does not emit a no-op poll in the tick loop.
Runtime behavior is independently gated by
`node.discovery.nostr.enabled`, which defaults to false; if the
config enables Nostr on a non-feature build, startup logs a
warning and continues without it.
== Cargo feature and dependencies
- New cargo feature `nostr-discovery = ["dep:nostr", "dep:nostr-sdk"]`.
Not in the default feature set.
- New optional Linux-only dependencies: `nostr 0.44` (features: std,
nip59) and `nostr-sdk 0.44`. Gift-wrap unwrap is hand-rolled in
`src/discovery/nostr/signal.rs` rather than relying on the SDK's
rumor-author check, which FIPS sidesteps by trusting `seal.pubkey`
exclusively.
== Wire format
Overlay advert event: `kind 37195`, parameterized replaceable
(NIP-01 application-defined replaceable range 30000-39999), with
`d = "fips-overlay-v1"`. The digits visually spell FIPS (7=F, 1=I,
9=P, 5=S); a relay survey confirmed the kind is unused.
Advert content carries the version tag, endpoint list
(`udp|tcp|tor` + addr), optional signal-relay and stun-server
metadata, and `issuedAt` / `expiresAt` timestamps. Endpoint
`addr: "nat"` is the sentinel that triggers traversal on the peer
side. NIP-40 `expiration` tag bounds staleness on permanent
shutdown. Lifecycle relies on parameterized-replaceable
supersession; the daemon does not emit NIP-09 kind-5 deletes —
strict relays (Damus, Primal) race delete-against-replace and can
silently drop the replacement.
Gift-wrapped signal event: `kind 21059`. Punch packets carry magic
values `PUNCH_MAGIC` / `PUNCH_ACK_MAGIC`, a sequence number, and a
16-byte session hash.
== Discovery surface
- `src/discovery.rs` (always compiled)
- `EstablishedTraversal`: bound UDP socket + selected remote +
peer npub + optional transport name/config tuning overrides.
- `BootstrapHandoffResult`: returned on successful handoff —
allocated transport id, local/remote addrs, peer NodeAddr,
session id.
- `src/discovery/nostr/` (`#![cfg(feature = "nostr-discovery")]`)
- `types.rs`: wire and control types described above. `ADVERT_KIND`
constant. `BootstrapError` enumerates failure modes (disabled,
missing advert, missing NAT endpoint, no usable relays, invalid
advert, invalid npub, signal timeout, punch timeout, replay,
STUN failure, protocol, nostr, io, serde, event-parse).
- `runtime.rs`: `NostrDiscovery` coordinator. Owns the shared
nostr-sdk `Client`, subscribes to advert + signal event kinds,
maintains a bounded advert cache and a bounded seen-sessions
replay set, drains `BootstrapEvent::{Established, Failed}` for
the node to consume, exposes `update_local_advert`,
`request_connect`, `advert_endpoints_for_peer`,
`cached_open_discovery_candidates`, and `shutdown`.
- `signal.rs`: NIP-59 gift-wrap encode/decode. Outbound wraps are
built against per-attempt ephemeral keys; inbound events are
unwrapped against the node identity.
- `stun.rs`: RFC 5389/8489 Binding Request client with
XOR-MAPPED-ADDRESS parsing for both IPv4 and IPv6; used only to
observe the initiator's own reflexive address against its
locally configured STUN list (peer-advertised STUN is
informational, never an egress target).
- `traversal.rs`: per-attempt candidate-pair punch planner.
Allocates a fresh `0.0.0.0:0` UDP socket per attempt, enumerates
LAN-private and ULA interface addresses alongside the STUN
reflexive address, schedules probe/ack exchanges at the
configured interval for the configured duration, and picks the
first candidate pair that authenticates end-to-end.
Strategy ordering is Reflexive↔Reflexive first, then LAN, then
Mixed. The STUN-observed pair is the only candidate that's reliable
across arbitrary network topologies; trying it first prevents the
planner from latching onto a misleading host-candidate path before
the reflexive path gets a chance. There is no catch-all
Local↔Local strategy: a previous design that paired every local
host candidate from one side with every local host candidate from
the other could declare success on a one-way reachable asymmetric
L3 path (corporate VPN, Tailscale subnet route, overlapping private
address space), only for the FMP handshake to stall because the
return path didn't match. The legitimate `Lan` strategy still pairs
candidates that share a subnet.
== Configuration surface
`node.discovery.nostr.*` (`NostrDiscoveryConfig`), all `serde(default)`
with `deny_unknown_fields`:
- `enabled` (default false), `advertise` (default true)
- `advert_relays`, `dm_relays`, `stun_servers`: defaults are
`wss://relay.damus.io`, `wss://nos.lol`, `wss://offchain.pub`
for both relay lists, and Google / Cloudflare / Twilio for STUN.
Operators are expected to override for production. Other
verified-working public relays for reference:
`nostr.bitcoiner.social`, `nostr-pub.wellorder.net`,
`nostr.oxtr.dev`, `nostr.mom`.
- `app` (default `"fips-overlay-v1"`), `signal_ttl_secs` (120)
- `policy`: `NostrDiscoveryPolicy::{Disabled, ConfiguredOnly (default),
Open}` — controls whether advert-derived endpoints are consumed
only for peers carrying `via_nostr = true`, or also for
non-configured peers within a budget cap.
- `share_local_candidates` (default false) — when false, the offer's
`local_addresses` list is empty and peers see only the reflexive
address. Enable per-node only for genuinely same-LAN deployments;
off-by-default eliminates the misleading-path failure mode for
the common case where peers are not on the same broadcast domain.
- `open_discovery_max_pending` (64) — caps queued open-discovery
retries; bounded by available outbound slots.
- `max_concurrent_incoming_offers` (16) — semaphore against offer
spam; excess offers are debug-logged and dropped.
- `advert_cache_max_entries` (2048) and `seen_sessions_max_entries`
(2048) — bound memory under ambient relay volume; overflow
evictions are debug-logged.
- `attempt_timeout_secs` (10), `replay_window_secs` (300)
- `punch_start_delay_ms` (2000), `punch_interval_ms` (200),
`punch_duration_ms` (10000)
- `advert_ttl_secs` (3600), `advert_refresh_secs` (1800)
Per-peer and per-transport flags:
- `PeerConfig.via_nostr: bool` — when true (and Nostr is enabled),
advert-derived addresses are appended as fallback dial candidates
after static addresses for that peer.
- `PeerConfig.addresses` is now `serde(default)` and may be empty
when `via_nostr: true`; validation requires at least one of the
two to be present per peer, and the error message names the
peer's npub.
- `UdpConfig.advertise_on_nostr: Option<bool>` and
`UdpConfig.public: Option<bool>` — UDP transports can be
advertised either as direct `host:port` (public = true) or as the
`addr: "nat"` sentinel that triggers rendezvous on the peer side.
- `TcpConfig.advertise_on_nostr` and `TorConfig.advertise_on_nostr`
— TCP and Tor onion endpoints can be advertised as directly
reachable.
- A reserved peer address `transport: udp, addr: "nat"` parses without
special-casing in YAML and routes through the bootstrap runtime.
Cross-field validation (`Config::validate`, called from `Node::new`
and `Node::with_identity`):
- Any transport with `advertise_on_nostr = true` requires
`node.discovery.nostr.enabled = true`.
- Any peer with `via_nostr = true` requires
`node.discovery.nostr.enabled = true`.
- A non-public UDP advert (`advertise_on_nostr = true`,
`public = false` — i.e. `udp:nat`) additionally requires at least
one `dm_relay` and at least one `stun_server`.
Surfaced as `ConfigError::Validation`.
== Node integration
`src/node/lifecycle.rs` is the main integration point.
- At node start (after transports are up, before TUN), if Nostr is
enabled and the feature is compiled in, `NostrDiscovery::start` is
invoked, the initial local overlay advert is built from the live
transport set and published, and the runtime handle is stored.
- The rx tick loop calls `poll_nostr_discovery` (feature-gated both
at method definition and call site), which refreshes the local
advert, drains bootstrap events, adopts established traversals,
schedules retries for failed traversals, and — under `policy:
open` — enqueues outbound retries for non-configured peers
visible in the advert cache, bounded by
`open_discovery_max_pending` and the remaining outbound slots.
- Outbound peer dialing is refactored to `try_peer_addresses`, which
first exhausts the static address list in priority order and only
then appends advert-derived fallback addresses; both lists run
through the same `attempt_peer_address_list` code path. The
`udp:nat` sentinel address triggers `NostrDiscovery::request_connect`
for the peer instead of a direct dial and returns `Ok(())`.
- `build_overlay_advert` walks operational transports, consults
per-instance `UdpConfig` / `TcpConfig` / `TorConfig` (matching by
optional transport instance name), and emits an `OverlayAdvert`
including `signalRelays` and `stunServers` when any UDP endpoint
is advertised as NAT.
- `adopt_established_traversal` is the bootstrap handoff API:
allocates a new `TransportId`, constructs a `UdpTransport` with
the user-supplied (or default) `UdpConfig`, calls the new
`adopt_socket_async` to reuse the punched socket verbatim,
registers the transport in the normal transport map, records it
in `bootstrap_transports`, and calls `initiate_connection` so the
normal handshake path runs. On failure, the transport is stopped
and removed cleanly and the set membership is rolled back.
- On clean shutdown, `NostrDiscovery::shutdown` is awaited so
background tasks stop before transports are torn down. (The
advert is not explicitly retracted; NIP-40 expiration plus the
next refresh from any live publisher supersedes it.)
New `Node` fields:
- `nostr_discovery: Option<Arc<NostrDiscovery>>` (feature-gated).
- `bootstrap_transports: HashSet<TransportId>` — per-peer UDP
transports adopted from NAT traversal, cleaned up via
`cleanup_bootstrap_transport_if_unused` whenever the link,
connection, peer, or pending-connect referencing them is removed.
Retry and error surface:
- `RetryState.expires_at_ms: Option<u64>` — optional absolute expiry
for a retry entry. `pump_retries` drops expired entries with an
info log. Used for open-discovery retries, which expire at two
times the advert TTL.
- New `NodeError::BootstrapHandoff(String)` returned from
`adopt_established_traversal` when the underlying transport
adoption fails or local address discovery fails.
- New `ConfigError::Validation(String)`.
- A small refactor extracts `Node::now_ms()` and reuses it across
lifecycle, rx-loop tick, and timeout bookkeeping.
== UDP transport
`src/transport/udp/`:
- `UdpRawSocket::adopt(std::net::UdpSocket, recv_buf, send_buf)`:
adopts an externally bound socket, makes it non-blocking, applies
the configured buffer sizes (warning if the kernel clamps), and
reports the resulting local address. Preserves the NAT mapping —
no rebind.
- `UdpTransport::adopt_socket_async(std::net::UdpSocket)`: the
`start_async` analogue for an already-bound socket, wiring the
async socket and recv task exactly as the fresh-bind path would.
- `Drop` impl for `UdpTransport`: if a transport is dropped while
still holding a recv task or socket (for example on error
teardown), aborts the task, clears the socket, and emits a debug
log so the cleanup is visible in tracing rather than silent.
== Logging and observability
Default `EnvFilter` demotes third-party relay-pool DEBUG output to
TRACE-only: `nostr_relay_pool`, `nostr_sdk`, and `nostr` are pinned
at INFO when our level is anything below TRACE, and at TRACE when
our level is TRACE — so the raw frames are still reachable when
explicitly asked for. RUST_LOG continues to override completely.
Concise one-line DEBUG events are emitted at the meaningful points
in the discovery / hole-punch sequence:
- `advert: published` (event id, relay count, endpoints, ttl)
- `advert: peer cached` (notify-loop ingress for non-self)
- `advert: resolved` (cache hit / relay fetch outcome)
- `traversal: initiator starting`
- `traversal: initiator STUN observed` (reflexive, local count)
- `traversal: offer sent` (session id, relay count, event id)
- `traversal: answer received` (accepted, reflexive, local)
- `traversal: initiator punch succeeded` (remote addr)
- `traversal: offer received` (responder side)
- `traversal: responder STUN observed`
- `traversal: answer sent`
- `traversal: responder punch succeeded`
Npubs are shortened to `npub1<4>..<4>` and event/session ids to
their first 8 hex characters.
Other operator-facing logs:
- `UdpTransport` adoption and drop paths log at info / debug.
- `adopt_established_traversal` logs at debug on entry and info on
successful return, tagged with peer npub, session id, transport
id, and both socket endpoints, so the bootstrap handoff is
traceable end-to-end alongside the `UdpTransport::drop` log.
- `cleanup_bootstrap_transport_if_unused` logs at debug when the
reference-count check drops an adopted transport.
- `connect_peer` tags its entry `debug!` with `peer_npub` so
downstream STUN, punch, and handshake logs for the same peer
correlate for operators.
- Advert-cache and seen-sessions overflow evictions log at debug so
mis-sized caps are visible under ambient relay volume.
- Gift-wrap unwrap failures on `SIGNAL_KIND` events log at trace
(hot path: fires for every unrelated signal event on the same
relay).
- Traversal-offer handler failures log at debug. Expected conditions
such as punch timeout on symmetric NAT are covered there; real
problems are reported upstream via `BootstrapEvent::Failed`.
- Inbound-offer rate-limit messages name the governing config field
(`max_concurrent_incoming_offers`) and state that the offer was
rate-limited rather than failing.
== Tests
- 18 new unit tests in `src/discovery/nostr/tests.rs` covering advert
encoding, signal envelope round-trip, STUN parsing, punch-packet
codec, and replay-window enforcement. Run under the
`nostr-discovery` feature.
- Config-validation tests in `src/config/mod.rs` covering the three
cross-field invariants and YAML parsing of the full
`node.discovery.nostr` block plus `peers[].via_nostr`, empty
`addresses` with `via_nostr: true`, and a `udp: nat` address.
- `src/node/tests/bootstrap.rs` integration tests that drive a
synthetic traversal (bound UDP socket pair + synthetic peer
identity) through `adopt_established_traversal` and assert the
Noise handshake completes over the adopted socket.
- Punch-planner tests assert reflexive-before-LAN ordering and that
same-LAN scenarios still include the LAN target in the plan.
- `testing/nat/` Docker NAT lab harness:
- Local `strfry` relay, local STUN responder, and one or two
router containers performing `iptables` NAT.
- Node LAN interfaces are provisioned with explicit `veth` pairs
injected into the node and router namespaces so every packet
traverses the router namespace (plain Docker bridges are not
used for the LAN).
- `cone` scenario: both peers behind full-cone-emulation NAT
(SNAT with source-port preservation, inbound DNAT back to the
single LAN host regardless of remote source); asserts UDP
traversal succeeds and link remote addresses are on the router
WAN subnet.
- `symmetric` scenario: `MASQUERADE --random-fully`; asserts UDP
traversal fails and TCP fallback converges over router-
published WAN addresses.
- `lan` scenario: both peers share a LAN subnet; asserts LAN
addresses are preferred over reflexive ones.
- Cleanup tears down all profile-gated services
(`--profile cone --profile symmetric --profile lan`) so no
orphan containers survive a run.
- `testing/scripts/build.sh` builds the Docker test image with
`--features "tui nostr-discovery"` by default so NAT-harness
binaries include bootstrap support.
== CI
- Linux release build and nextest unit-test job both use
`--features "gateway nostr-discovery"` so the feature-gated code
and its unit tests compile and run in CI.
- Three new integration matrix entries (`nat-cone`, `nat-symmetric`,
`nat-lan`) invoke `testing/nat/scripts/nat-test.sh`, collect
`docker compose logs` on failure, and always stop containers.
== Packaging and operations
- `packaging/common/fips.yaml` ships a fully commented
`node.discovery.nostr.*` block, plus documented
`advertise_on_nostr` / `public` examples under the UDP transport,
an `advertise_on_nostr` example under TCP, and a `via_nostr: true`
example under the static peer section with both a direct
`host:port` UDP address and a `udp: nat` fallback.
- `.github/workflows/package-openwrt.yml`: NIP-94 release event
publishes target the new default relay set.
== Documentation
- `README.md`: overlay discovery + NAT traversal moved from
"Near-term priorities" into "What works today".
- `docs/design/fips-intro.md`: rewrites the paragraphs that
previously described Nostr discovery and NAT traversal as future
work; describes the shipped mechanism and the feature gate.
- `docs/design/fips-transport-layer.md`: drops the "(future
direction)" qualifier from the Nostr Relay Discovery section,
expands with the `udp:nat` advertisement and bootstrap handoff
description, and updates the Current State callout.
- `docs/design/fips-mesh-layer.md`: notes that mid-session NAT
rebinding (roaming) and initial NAT traversal (Nostr path) are
distinct mechanisms.
- `docs/design/fips-configuration.md`: documents the full
`node.discovery.nostr.*` surface, including the three resource
caps and `share_local_candidates`.
- `docs/design/fips-nostr-discovery.md`: design and configuration
reference for the shipped mechanism, including the empty-
`addresses`-with-`via_nostr` shorthand.
- `docs/proposals/nostr-udp-hole-punch-protocol.md`: adds an
Implemented status callout, clarifies that the punch socket is
per-peer and per-attempt rather than shared with the application
listener, aligns field names with the shipped JSON
(`sessionId`, `issuedAt` / `expiresAt`, `reflexiveAddress`,
`localAddresses`, `stunServer`), sets the `d`-tag to
`fips-overlay-v1`, names the kind as 37195, and notes that
advertised STUN entries are informational.
- `docs/proposals/README.md`: adds a Status column and marks the
hole-punching proposal Implemented.
- `CHANGELOG.md`: Unreleased > Added entry covering the discovery
path, STUN/punch path, configuration surface, and Docker NAT lab.
Co-authored-by: Johnathan Corgan <johnathan@corganlabs.com>
2.2 KiB
2.2 KiB
FIPS Design Documents
Protocol design specifications for the Federated Interoperable Peering System — a self-organizing encrypted mesh network built on Nostr identities.
Reading Order
Start with the introduction, then follow the protocol stack from bottom to top. After the stack, the mesh operation document explains how all the pieces work together. Supporting references provide deeper dives into specific topics.
Protocol Stack
| Document | Description |
|---|---|
| fips-intro.md | Protocol introduction: goals, architecture, layer model |
| fips-transport-layer.md | Transport layer: datagram delivery over arbitrary media |
| fips-mesh-layer.md | FIPS Mesh Protocol (FMP): peer authentication, link encryption, forwarding |
| fips-session-layer.md | FIPS Session Protocol (FSP): end-to-end encryption, sessions |
| fips-ipv6-adapter.md | IPv6 adaptation: TUN interface, DNS, MTU enforcement |
Mesh Behavior
| Document | Description |
|---|---|
| fips-mesh-operation.md | How the mesh operates: routing, discovery, error recovery |
| fips-wire-formats.md | Wire format reference for all message types |
| fips-nostr-discovery.md | Optional Nostr-mediated peer discovery and UDP NAT hole-punch (behind nostr-discovery feature) |
Supporting References
| Document | Description |
|---|---|
| fips-spanning-tree.md | Spanning tree algorithms: root discovery, parent selection, coordinates |
| fips-bloom-filters.md | Bloom filter math: FPR analysis, size classes, split-horizon |
Implementation
| Document | Description |
|---|---|
| fips-configuration.md | YAML configuration reference |
Supplemental
| Document | Description |
|---|---|
| spanning-tree-dynamics.md | Spanning tree walkthroughs: convergence scenarios, worked examples |
Document Relationships
