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Add Nostr-mediated overlay discovery and UDP NAT traversal (#53)
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>
This commit is contained in:
Tom
GitHub
@@ -26,6 +26,7 @@ specific topics.
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| -------- | ----------- |
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| [fips-mesh-operation.md](fips-mesh-operation.md) | How the mesh operates: routing, discovery, error recovery |
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| [fips-wire-formats.md](fips-wire-formats.md) | Wire format reference for all message types |
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| [fips-nostr-discovery.md](fips-nostr-discovery.md) | Optional Nostr-mediated peer discovery and UDP NAT hole-punch (behind `nostr-discovery` feature) |
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### Supporting References
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@@ -171,6 +171,60 @@ Controls bloom-guided node discovery (LookupRequest/LookupResponse).
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| `node.discovery.backoff_max_secs` | u64 | `0` | Cap on optional post-failure backoff |
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| `node.discovery.forward_min_interval_secs` | u64 | `2` | Transit-side rate limiting: minimum interval between forwarded lookups for the same target |
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#### Nostr Overlay Discovery (`node.discovery.nostr.*`)
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Optional Nostr-mediated overlay discovery. This layer publishes replaceable
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endpoint adverts (`fips-overlay-v1`), consumes advert-derived endpoint
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fallbacks for configured peers, and can optionally discover non-configured
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peers (`policy: open`). `udp:nat` remains the trigger for NAT traversal
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offer/answer + punch-through, after which the established UDP socket is handed
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into the normal FIPS transport/session stack.
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Inbox-relay discovery falls back to the local DM relay list if remote relay
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metadata cannot be fetched.
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This support is compiled behind the crate feature `nostr-discovery`; builds
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without that feature ignore `udp:nat` bootstrap configuration.
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| Parameter | Type | Default | Description |
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|-----------|------|---------|-------------|
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| `node.discovery.nostr.enabled` | bool | `false` | Enable Nostr-mediated overlay discovery |
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| `node.discovery.nostr.policy` | string | `"configured_only"` | Advert discovery policy: `disabled`, `configured_only`, `open` |
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| `node.discovery.nostr.open_discovery_max_pending` | usize | `64` | Max open-discovery peers queued in outbound retry/connection state at once |
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| `node.discovery.nostr.max_concurrent_incoming_offers` | usize | `16` | Max concurrent inbound traversal offers processed at once (rate limit against offer spam) |
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| `node.discovery.nostr.advert_cache_max_entries` | usize | `2048` | Max cached overlay adverts retained from relay traffic |
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| `node.discovery.nostr.seen_sessions_max_entries` | usize | `2048` | Max seen-session IDs retained for replay detection |
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| `node.discovery.nostr.advertise` | bool | `true` | Publish local endpoint adverts |
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| `node.discovery.nostr.advert_relays` | list[string] | `["wss://relay.damus.io", "wss://nos.lol", "wss://offchain.pub"]` | Relays used for service adverts |
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| `node.discovery.nostr.dm_relays` | list[string] | `["wss://relay.damus.io", "wss://nos.lol", "wss://offchain.pub"]` | Relays used for encrypted signaling events |
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| `node.discovery.nostr.stun_servers` | list[string] | `["stun:stun.l.google.com:19302", "stun:stun.cloudflare.com:3478", "stun:global.stun.twilio.com:3478"]` | STUN servers used for local reflexive address discovery |
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| `node.discovery.nostr.app` | string | `"fips-overlay-v1"` | Traversal application namespace and advert identifier suffix |
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| `node.discovery.nostr.signal_ttl_secs` | u64 | `120` | Signaling TTL in seconds |
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| `node.discovery.nostr.attempt_timeout_secs` | u64 | `10` | Overall traversal attempt timeout in seconds |
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| `node.discovery.nostr.replay_window_secs` | u64 | `300` | Replay tracking retention window in seconds |
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| `node.discovery.nostr.punch_start_delay_ms` | u64 | `2000` | Delay before punch traffic starts |
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| `node.discovery.nostr.punch_interval_ms` | u64 | `200` | Interval between punch packets |
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| `node.discovery.nostr.punch_duration_ms` | u64 | `10000` | How long to keep punching before failure |
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| `node.discovery.nostr.advert_ttl_secs` | u64 | `3600` | Advert TTL in seconds |
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| `node.discovery.nostr.advert_refresh_secs` | u64 | `1800` | How often adverts are refreshed in seconds |
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If `stun_servers` is omitted, the built-in default list above is used. If it is
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specified in YAML, the configured list fully overrides the defaults.
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Initiators use only this local list for outbound STUN queries; peer-advertised
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STUN values are published for diagnostics/interoperability but are not used as
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arbitrary egress targets.
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The built-in advert and DM relay defaults point at widely-operated public
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relays (Damus, nos.lol, Primal) as best-effort endpoints; operators are
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encouraged to override them with their own relay preferences for production
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deployments.
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Advert freshness is enforced semantically: events with expired NIP-40
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`expiration` tags are dropped, and adverts are also bounded by a created-at
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staleness window derived from `advert_ttl_secs` (with a grace multiplier).
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The current in-tree STUN parser handles IPv4 and IPv6 mapped-address
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attributes. Local traversal candidates include active non-loopback private
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interface addresses (RFC1918 IPv4 and IPv6 ULA) plus probed local egress
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addresses for the punch socket port.
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During punching, compatible private-subnet candidates and reflexive candidates
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are attempted in parallel; the first successful path wins.
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### Spanning Tree (`node.tree.*`)
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Controls tree construction and parent selection.
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@@ -324,6 +378,8 @@ restarting the daemon. Hostnames are case-insensitive.
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| `transports.udp.mtu` | u16 | `1280` | Transport MTU |
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| `transports.udp.recv_buf_size` | usize | `2097152` | UDP socket receive buffer size in bytes (2 MB). Linux kernel doubles the requested value internally. Host `net.core.rmem_max` must be >= this value. |
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| `transports.udp.send_buf_size` | usize | `2097152` | UDP socket send buffer size in bytes (2 MB). Host `net.core.wmem_max` must be >= this value. |
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| `transports.udp.advertise_on_nostr` | bool | `false` | Include this UDP transport in Nostr endpoint adverts |
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| `transports.udp.public` | bool | `false` | If advertised: `true` publishes direct `host:port`; `false` publishes `udp:nat` rendezvous |
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### Ethernet (`transports.ethernet.*`)
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@@ -582,6 +638,7 @@ Static peer list. Each entry defines a peer to connect to.
|
||||
| `peers[].addresses[].priority` | u8 | `100` | Address priority (lower = preferred) |
|
||||
| `peers[].connect_policy` | string | `"auto_connect"` | Connection policy: `auto_connect`, `on_demand`, or `manual` |
|
||||
| `peers[].auto_reconnect` | bool | `true` | Automatically reconnect after MMP link-dead removal (exponential backoff, unlimited retries) |
|
||||
| `peers[].via_nostr` | bool | `false` | Append Nostr advert-derived endpoints after static addresses for this peer |
|
||||
|
||||
## Minimal Example
|
||||
|
||||
|
||||
@@ -514,15 +514,19 @@ and radio are natural fits for this, as they can reach nearby devices without
|
||||
prior configuration. When discovery is available, nodes can automatically
|
||||
find and peer with other FIPS nodes on the same medium. Transports that
|
||||
lack discovery (such as configured UDP endpoints) simply skip this step and
|
||||
connect directly to configured addresses. Additionally, endpoint discovery
|
||||
using Nostr relays and signed events is planned, allowing internet-reachable
|
||||
nodes to publish their transport addresses for other FIPS nodes to find.
|
||||
connect directly to configured addresses. For internet-reachable nodes,
|
||||
endpoint discovery via signed Nostr events allows nodes to publish and
|
||||
consume transport addresses through public relays — available behind the
|
||||
`nostr-discovery` cargo feature.
|
||||
|
||||
NAT traversal is not currently addressed by the protocol.
|
||||
Internet-connected nodes behind NAT must be reachable through port
|
||||
forwarding, a publicly addressed peer, or relay through other mesh nodes.
|
||||
UDP hole punching and relay-assisted NAT traversal are potential future
|
||||
mechanisms but are not part of the current design.
|
||||
NAT traversal for internet-connected nodes is supported via STUN-assisted
|
||||
UDP hole punching, with offer/answer signaling carried over Nostr gift-wrap
|
||||
events. Once a direct UDP path is established, the punched socket is handed
|
||||
into the standard FIPS transport/session stack. Nodes that cannot establish
|
||||
a direct path remain reachable through port forwarding, a publicly addressed
|
||||
peer, or relay through other mesh nodes. The Nostr-mediated discovery and
|
||||
NAT traversal paths are gated by the `nostr-discovery` cargo feature and
|
||||
configured under `node.discovery.nostr.*`.
|
||||
|
||||
> **Implementation status**: UDP/IP, TCP/IP, Ethernet, Tor
|
||||
> (SOCKS5 outbound + directory-mode inbound via onion service),
|
||||
|
||||
@@ -292,6 +292,12 @@ Roaming is most useful for UDP, where source addresses can change due to NAT
|
||||
rebinding or network changes. For connection-oriented transports, "roaming"
|
||||
manifests as reconnection rather than mid-session address change.
|
||||
|
||||
Roaming addresses *mid-session* NAT rebinding. Establishing the initial UDP
|
||||
path through NAT is a separate concern, addressed by the optional
|
||||
Nostr-mediated overlay discovery and STUN-assisted hole punching feature
|
||||
(see [fips-transport-layer.md](fips-transport-layer.md) and
|
||||
[fips-configuration.md](fips-configuration.md)).
|
||||
|
||||
## Replay Protection
|
||||
|
||||
Each link session maintains per-direction counters:
|
||||
|
||||
659
docs/design/fips-nostr-discovery.md
Normal file
659
docs/design/fips-nostr-discovery.md
Normal file
@@ -0,0 +1,659 @@
|
||||
# FIPS Nostr-Mediated Discovery and NAT Traversal
|
||||
|
||||
Nostr-mediated discovery lets FIPS nodes find each other, and if
|
||||
necessary, punch through UDP NAT, using public Nostr relays as the
|
||||
signaling channel. A node publishes its reachable transport endpoints to
|
||||
a small set of relays under its own Nostr identity (which is also its
|
||||
FIPS identity), and peers resolve those endpoints at dial time by npub.
|
||||
For peers behind UDP NAT, the same relay channel carries an encrypted
|
||||
offer/answer exchange, and STUN supplies the reflexive address used for
|
||||
a coordinated hole-punch.
|
||||
|
||||
The feature is compiled into FIPS by default on all supported platforms
|
||||
(Linux, macOS, Windows) and ships in every stock packaging artifact
|
||||
(`.deb`, AUR, systemd tarball, OpenWrt `.ipk`, macOS `.pkg`, Windows
|
||||
`.zip`). It is runtime-opt-in: the YAML configuration defaults to
|
||||
disabled, so shipping the feature is a no-op until an operator enables
|
||||
it. When disabled, nodes behave exactly as before: only the static
|
||||
`peers[]` addresses are used. See
|
||||
[Build configuration](#build-configuration) for details on opting out
|
||||
at build time.
|
||||
|
||||
## Role
|
||||
|
||||
The feature adds three capabilities on top of FIPS's static peer model:
|
||||
|
||||
- **Advertising.** A node publishes the transport endpoints it wants
|
||||
peers to use (direct UDP, direct TCP, a Tor onion, or the special
|
||||
`udp:nat` rendezvous token) as a signed Nostr event. The advert is
|
||||
anchored to the node's FIPS identity key — a peer that knows the npub
|
||||
knows the advert is authentic.
|
||||
- **Lookup.** When dialing a configured peer marked `via_nostr`, or any
|
||||
peer in `policy: open` mode, the node fetches that peer's advert from
|
||||
the configured relays and appends the advertised endpoints to its
|
||||
dial list. Static addresses are always tried first.
|
||||
- **UDP NAT hole-punch.** When both sides of a connection have UDP NAT
|
||||
endpoints, the advert carries enough information to run a STUN-based
|
||||
offer/answer exchange over encrypted ([NIP-59](https://github.com/nostr-protocol/nips/blob/master/59.md))
|
||||
Nostr events. Each side observes its reflexive address via STUN,
|
||||
exchanges candidate pairs through the relay, and both sides send UDP
|
||||
probes at a shared punch time. On the first successful probe, the
|
||||
punch socket is handed to FMP and becomes a normal UDP transport.
|
||||
|
||||
## When to use it
|
||||
|
||||
- **You run a public node** and want peers who know your npub to reach
|
||||
you without you distributing an address list out-of-band.
|
||||
- **You want to reach a peer behind UDP NAT** without deploying a relay
|
||||
or running Tor on both sides. The peer advertises `udp:nat` and you
|
||||
dial by npub.
|
||||
- **You want zero-touch peer discovery** within a known application
|
||||
namespace (`policy: open`), subject to an admission budget.
|
||||
- **You want to advertise a Tor onion** so peers don't need to know the
|
||||
`.onion` address out-of-band.
|
||||
|
||||
Skip the feature when every peer is already reachable through a stable
|
||||
static address (a LAN mesh, a pre-configured test bed, or a deployment
|
||||
where operators distribute `peers[]` blocks directly). The feature adds
|
||||
relay dependencies, STUN round-trips for NAT cases, and a small ambient
|
||||
background of relay traffic; none of that is useful when you already
|
||||
know where peers are.
|
||||
|
||||
## Build configuration
|
||||
|
||||
`nostr-discovery` is a default Cargo feature. Plain `cargo build
|
||||
--release` produces a binary with the feature compiled in, and every
|
||||
stock packaging artifact under `packaging/` ships with it enabled.
|
||||
There is no extra `--features` flag to remember, on any platform.
|
||||
|
||||
Shipping the feature is runtime-safe: Nostr discovery is **off by
|
||||
default in the YAML configuration**
|
||||
(`node.discovery.nostr.enabled: false` in every stock config). An
|
||||
operator opts in per-node by flipping the flag and providing a relay
|
||||
list; until then the feature is dormant and does not open connections
|
||||
to any relay.
|
||||
|
||||
To build a binary **without** the feature — for example, to reduce
|
||||
the dependency footprint on a minimal build — use
|
||||
`--no-default-features`:
|
||||
|
||||
```bash
|
||||
cargo build --release --no-default-features
|
||||
```
|
||||
|
||||
The `nostr` and `nostr-sdk` crates are then omitted from the
|
||||
dependency tree entirely, and `node.discovery.nostr` config blocks
|
||||
fail at startup validation.
|
||||
|
||||
## Scenarios and configuration
|
||||
|
||||
Each scenario below gives the minimal YAML fragment that enables it.
|
||||
Only keys relevant to Nostr discovery are shown; surrounding node,
|
||||
transport, TUN, DNS, and peer configuration follows the usual shape
|
||||
described in [fips-configuration.md](fips-configuration.md).
|
||||
|
||||
All scenarios assume `node.identity` is set to a persistent key — an
|
||||
ephemeral identity would invalidate any advert the moment the node
|
||||
restarts.
|
||||
|
||||
### Scenario 1: Advertise a directly-reachable UDP node
|
||||
|
||||
The node has a public IP (or a stable port-forward) and binds UDP on a
|
||||
known port. It publishes `udp:host:port` to the advert relays. Any peer
|
||||
that knows this node's npub and has Nostr discovery enabled can dial it
|
||||
without knowing the address out-of-band.
|
||||
|
||||
```yaml
|
||||
node:
|
||||
identity:
|
||||
persistent: true
|
||||
discovery:
|
||||
nostr:
|
||||
enabled: true
|
||||
advertise: true
|
||||
|
||||
transports:
|
||||
udp:
|
||||
bind_addr: "0.0.0.0:2121"
|
||||
advertise_on_nostr: true
|
||||
public: true
|
||||
```
|
||||
|
||||
What this achieves: the node publishes a single `udp:<public-ip>:2121`
|
||||
endpoint to the three default advert relays
|
||||
(`wss://relay.damus.io`, `wss://nos.lol`, `wss://offchain.pub`).
|
||||
|
||||
What the other side needs: either a static `addresses` entry for this
|
||||
peer, or a peer entry with `via_nostr: true` and an empty (or omitted)
|
||||
`addresses` list — the advert-resolved endpoint will be used at dial
|
||||
time. Static and Nostr-resolved addresses can also be combined: when
|
||||
both are present, static addresses are tried first and Nostr-resolved
|
||||
endpoints are appended as fallback.
|
||||
|
||||
### Scenario 2: Advertise a Tor onion node
|
||||
|
||||
The node runs a Tor onion service in directory mode (Tor-managed
|
||||
`HiddenServiceDir`) and advertises the `.onion` address. Peers dial via
|
||||
their local Tor SOCKS5 proxy without ever knowing the onion string
|
||||
out-of-band.
|
||||
|
||||
```yaml
|
||||
node:
|
||||
identity:
|
||||
persistent: true
|
||||
discovery:
|
||||
nostr:
|
||||
enabled: true
|
||||
advertise: true
|
||||
|
||||
transports:
|
||||
tor:
|
||||
mode: directory
|
||||
socks5_addr: "127.0.0.1:9050"
|
||||
directory_service:
|
||||
hostname_file: "/var/lib/tor/fips/hostname"
|
||||
bind_addr: "127.0.0.1:8444"
|
||||
advertise_on_nostr: true
|
||||
```
|
||||
|
||||
What this achieves: the node publishes a `tor:<hash>.onion:8443`
|
||||
endpoint alongside any other advertised transports. The advert itself
|
||||
is still published over clearnet WebSocket relays — Tor protects the
|
||||
data plane, not the discovery plane. See
|
||||
[Security and threat model](#security-and-threat-model) for the trade-off.
|
||||
|
||||
### Scenario 3: Lookup a configured peer by npub (no advertising)
|
||||
|
||||
The node does not publish any advert of its own. It only consumes
|
||||
adverts for peers it has explicitly listed with `via_nostr: true`. This
|
||||
is the right shape for a client that wants Nostr-mediated resolution
|
||||
without becoming a rendezvous target itself.
|
||||
|
||||
```yaml
|
||||
node:
|
||||
identity:
|
||||
persistent: true
|
||||
discovery:
|
||||
nostr:
|
||||
enabled: true
|
||||
advertise: false
|
||||
policy: configured_only
|
||||
|
||||
transports:
|
||||
udp:
|
||||
bind_addr: "0.0.0.0:2121"
|
||||
|
||||
peers:
|
||||
- npub: "npub1peer..."
|
||||
alias: "remote-node"
|
||||
addresses:
|
||||
- transport: udp
|
||||
addr: "203.0.113.45:2121"
|
||||
priority: 10
|
||||
via_nostr: true
|
||||
connect_policy: auto_connect
|
||||
```
|
||||
|
||||
What this achieves: on dial, the static address is tried first; if the
|
||||
peer has published a newer advert (for example, its public IP has
|
||||
changed), those addresses are appended as additional candidates.
|
||||
`configured_only` is the default — it is shown here for clarity.
|
||||
|
||||
If you have no static address for the peer at all, omit `addresses`
|
||||
entirely (or leave it empty) — `via_nostr: true` is sufficient on its
|
||||
own and dial endpoints are taken from the advert.
|
||||
|
||||
### Scenario 4: UDP NAT hole-punch with a configured peer
|
||||
|
||||
Neither side has a stable public UDP endpoint. Both sides advertise
|
||||
`udp:nat`, run the STUN + offer/answer exchange, and punch through
|
||||
their NATs to establish a direct UDP link. This is the full
|
||||
NAT-traversal path.
|
||||
|
||||
```yaml
|
||||
node:
|
||||
identity:
|
||||
persistent: true
|
||||
discovery:
|
||||
nostr:
|
||||
enabled: true
|
||||
advertise: true
|
||||
dm_relays:
|
||||
- "wss://relay.damus.io"
|
||||
- "wss://nos.lol"
|
||||
stun_servers:
|
||||
- "stun:stun.l.google.com:19302"
|
||||
- "stun:stun.cloudflare.com:3478"
|
||||
|
||||
transports:
|
||||
udp:
|
||||
bind_addr: "0.0.0.0:2121"
|
||||
advertise_on_nostr: true
|
||||
public: false
|
||||
|
||||
peers:
|
||||
- npub: "npub1peer..."
|
||||
alias: "nat-peer"
|
||||
addresses:
|
||||
- transport: udp
|
||||
addr: "nat"
|
||||
priority: 1
|
||||
via_nostr: true
|
||||
connect_policy: auto_connect
|
||||
auto_reconnect: true
|
||||
```
|
||||
|
||||
What this achieves: the node publishes a `udp:nat` endpoint plus its
|
||||
signaling relays and STUN server list in the advert. The peer side runs
|
||||
the same configuration. When either side initiates, an encrypted offer
|
||||
is sealed to the peer's npub, a matching answer comes back, and both
|
||||
sides punch at the negotiated time. On success, the punch socket is
|
||||
adopted as an FMP UDP transport and Noise IK proceeds normally.
|
||||
|
||||
> **Validation:** `advertise_on_nostr: true` with `public: false` on UDP
|
||||
> requires both `dm_relays` and `stun_servers` to be non-empty. The
|
||||
> node fails startup with a config validation error if either list is
|
||||
> empty. This is enforced because a `udp:nat` advert without signaling
|
||||
> relays or STUN servers is unreachable by construction.
|
||||
|
||||
Works best with full-cone NAT on at least one side. Symmetric NAT on
|
||||
both sides is not reliably traversable with this protocol and will time
|
||||
out after `punch_duration_ms`; fall back to a Tor or TCP transport in
|
||||
that case.
|
||||
|
||||
### Scenario 5: Open discovery — no pre-configured peers
|
||||
|
||||
Under `policy: open`, any node that publishes an advert under the same
|
||||
`app` namespace becomes a candidate. Discovered peers are queued for
|
||||
connection attempts subject to `open_discovery_max_pending`.
|
||||
|
||||
```yaml
|
||||
node:
|
||||
identity:
|
||||
persistent: true
|
||||
discovery:
|
||||
nostr:
|
||||
enabled: true
|
||||
advertise: true
|
||||
policy: open
|
||||
open_discovery_max_pending: 32
|
||||
app: "my-experiment.v1"
|
||||
|
||||
transports:
|
||||
udp:
|
||||
bind_addr: "0.0.0.0:2121"
|
||||
advertise_on_nostr: true
|
||||
public: true
|
||||
|
||||
peers: []
|
||||
```
|
||||
|
||||
What this achieves: peers are discovered entirely through ambient advert
|
||||
traffic on the configured relays. Setting a non-default `app` value
|
||||
(replacing `fips-overlay-v1`) scopes the discovery set to participants
|
||||
who opt into the same experiment and avoids being joined to unrelated
|
||||
overlays that happen to share the default namespace.
|
||||
|
||||
> **Scope warning:** Open discovery is an admission-free mode. Any node
|
||||
> that publishes on the same `app` name and passes the peer-ACL check
|
||||
> becomes a connection candidate. If you rely on peer ACLs for admission
|
||||
> control, verify that list is set correctly before enabling this mode.
|
||||
|
||||
## Operational knobs
|
||||
|
||||
All fields below live under `node.discovery.nostr.*`. Defaults are
|
||||
defined in `src/config/node.rs`.
|
||||
|
||||
| Field | Type | Default | Purpose |
|
||||
| --- | --- | --- | --- |
|
||||
| `enabled` | bool | `false` | Master switch. When false, the discovery runtime is not started. |
|
||||
| `advertise` | bool | `true` | If true, publish this node's own overlay advert. |
|
||||
| `advert_relays` | list | `["wss://relay.damus.io", "wss://nos.lol", "wss://offchain.pub"]` | Relays used to publish and fetch overlay adverts (kind 37195). |
|
||||
| `dm_relays` | list | same as `advert_relays` | Relays used for encrypted offer/answer signaling (kind 21059). |
|
||||
| `stun_servers` | list | `["stun:stun.l.google.com:19302", "stun:stun.cloudflare.com:3478", "stun:global.stun.twilio.com:3478"]` | STUN servers used to observe the local reflexive address before a punch. Peer-advertised STUN values are not used. |
|
||||
| `share_local_candidates` | bool | `false` | If true, include this node's RFC 1918 / ULA interface addresses as host candidates in the traversal offer. Off by default — sharing private host candidates is only useful when peers are on the same physical LAN, and tends to cause misleading punch successes when an asymmetric L3 path (corporate VPN, Tailscale subnet route, overlapping address space) makes a peer's private IP one-way reachable. Enable per-node only when same-LAN punching is wanted. |
|
||||
| `app` | string | `"fips-overlay-v1"` | Application namespace. Included in the advert identifier; only peers with the same value cross-resolve. |
|
||||
| `policy` | enum | `configured_only` | Advert consumption policy: `disabled`, `configured_only`, or `open`. |
|
||||
| `signal_ttl_secs` | u64 | `120` | TTL on the encrypted offer/answer events. Also caps the wait for an answer. |
|
||||
| `advert_ttl_secs` | u64 | `3600` | NIP-40 expiration set on this node's published advert. |
|
||||
| `advert_refresh_secs` | u64 | `1800` | Interval between re-publishes. Must be less than `advert_ttl_secs`. |
|
||||
| `attempt_timeout_secs` | u64 | `10` | Overall timeout for a single punch attempt (STUN + signal + punch). |
|
||||
| `punch_start_delay_ms` | u64 | `2000` | Delay between receiving the answer and sending the first punch packet. Gives the remote side time to arrive at the same point. |
|
||||
| `punch_interval_ms` | u64 | `200` | Gap between successive punch probes. |
|
||||
| `punch_duration_ms` | u64 | `10000` | How long to keep probing before declaring the attempt failed. |
|
||||
| `replay_window_secs` | u64 | `300` | How long a session id stays in the replay-detection cache. |
|
||||
| `max_concurrent_incoming_offers` | usize | `16` | Semaphore cap on inbound offers being processed simultaneously. Excess offers are dropped with a warn log. |
|
||||
| `advert_cache_max_entries` | usize | `2048` | Max cached peer adverts (LRU by expiry). |
|
||||
| `seen_sessions_max_entries` | usize | `2048` | Max tracked session ids for replay detection. |
|
||||
| `open_discovery_max_pending` | usize | `64` | Max peers queued for connection attempts under `policy: open`. |
|
||||
|
||||
The per-transport keys are:
|
||||
|
||||
| Key | Type | Where | Default | Purpose |
|
||||
| --- | --- | --- | --- | --- |
|
||||
| `advertise_on_nostr` | bool | `transports.{udp,tcp,tor}` | `false` | Include this transport's endpoint in the overlay advert. |
|
||||
| `public` | bool | `transports.udp` | `false` | When `advertise_on_nostr` is true: `true` publishes `udp:host:port`, `false` publishes `udp:nat`. |
|
||||
| `via_nostr` | bool | `peers[]` | `false` | Append advert-resolved endpoints to this peer's dial list. |
|
||||
|
||||
## Validation rules at startup
|
||||
|
||||
The following combinations are rejected with `ConfigError::Validation`:
|
||||
|
||||
- Any transport sets `advertise_on_nostr: true` while
|
||||
`node.discovery.nostr.enabled` is `false` or absent.
|
||||
- Any peer sets `via_nostr: true` while
|
||||
`node.discovery.nostr.enabled` is `false` or absent.
|
||||
- A UDP transport sets `advertise_on_nostr: true` with `public: false`
|
||||
(a `udp:nat` advert) but `dm_relays` is empty.
|
||||
- A UDP transport sets `advertise_on_nostr: true` with `public: false`
|
||||
but `stun_servers` is empty.
|
||||
|
||||
## Under the covers
|
||||
|
||||
The rest of this document describes how the feature works inside the
|
||||
node. For the on-the-wire event format and NIP references, see the
|
||||
protocol reference at
|
||||
[../proposals/nostr-udp-hole-punch-protocol.md](../proposals/nostr-udp-hole-punch-protocol.md).
|
||||
|
||||
### Overview
|
||||
|
||||
The discovery runtime is a background task group started during node
|
||||
initialization when `nostr.enabled` is true. It maintains a single
|
||||
`nostr-sdk` client connected to the union of `advert_relays` and
|
||||
`dm_relays`, and runs four loops: advert publication, advert
|
||||
subscription (for open discovery and cache warming), DM subscription
|
||||
(for incoming offers and answers), and a periodic advert-cache prune.
|
||||
Discovery has no CLI surface; all operations are driven by the
|
||||
configuration and by connection attempts made by the rest of the node.
|
||||
|
||||
```text
|
||||
+-----------------------+
|
||||
| Discovery runtime |
|
||||
+-----------------------+
|
||||
| | |
|
||||
advert publish | | DM sub (offers, answers)
|
||||
| |
|
||||
v v
|
||||
+-------------------------+
|
||||
| Nostr relay pool | (advert_relays ∪ dm_relays)
|
||||
+-------------------------+
|
||||
^ ^
|
||||
advert fetch/cache | | encrypted signaling
|
||||
| |
|
||||
+----------------+ | | +--------------------+
|
||||
| connect_peer |--+ +->| offer / answer |
|
||||
| (node side) | | handler |
|
||||
+----------------+ +--------------------+
|
||||
| |
|
||||
v v
|
||||
+---------+ +--------------+
|
||||
| STUN |<-- same socket --->| UDP punch |
|
||||
+---------+ +--------------+
|
||||
|
|
||||
v
|
||||
adopt_established_traversal()
|
||||
|
|
||||
v
|
||||
FMP IK handshake
|
||||
on adopted socket
|
||||
```
|
||||
|
||||
### Phase 1 — Advertisement
|
||||
|
||||
Adverts are published as Nostr kind `37195` parameterized replaceable
|
||||
events (FIPS-specific, in the application-defined replaceable range
|
||||
`30000–39999`; the digits visually spell `FIPS` — 7=F, 1=I, 9=P, 5=S).
|
||||
The `d` tag is set to the `app` value (default `fips-overlay-v1`), so
|
||||
each node has a single, in-place-updatable advert under its identity.
|
||||
The event is signed with the node's FIPS identity key; there is no
|
||||
separate Nostr key. A NIP-40 `expiration` tag is set to now +
|
||||
`advert_ttl_secs`.
|
||||
|
||||
The advert content is a JSON document shaped as `OverlayAdvert`:
|
||||
|
||||
```json
|
||||
{
|
||||
"identifier": "fips-overlay-v1",
|
||||
"version": 1,
|
||||
"endpoints": [
|
||||
{"transport": "udp", "addr": "203.0.113.45:2121"},
|
||||
{"transport": "tor", "addr": "xxxxx.onion:8443"},
|
||||
{"transport": "udp", "addr": "nat"}
|
||||
],
|
||||
"signalRelays": ["wss://relay.damus.io", "wss://nos.lol"],
|
||||
"stunServers": ["stun:stun.l.google.com:19302"]
|
||||
}
|
||||
```
|
||||
|
||||
`signalRelays` and `stunServers` are only present when at least one
|
||||
endpoint is `udp:nat`; for advert shapes that cannot involve punching
|
||||
they are omitted to reduce advert size and keep the relay and STUN
|
||||
lists private to the nodes that need them.
|
||||
|
||||
Publication happens on startup, again whenever the set of advertised
|
||||
endpoints changes (for example, when a Tor onion hostname first
|
||||
becomes available), and on a refresh timer every `advert_refresh_secs`.
|
||||
If the `advertise` flag is turned off, the previous advert event is
|
||||
deleted using a NIP-9 kind 5 delete event. Advert publication is
|
||||
fan-out: the same event is sent to every relay in `advert_relays` with
|
||||
no explicit failover — relay redundancy is implicit.
|
||||
|
||||
### Phase 2 — Lookup
|
||||
|
||||
When the node decides to dial a peer that is eligible for Nostr
|
||||
resolution (a `via_nostr` peer, or any peer under `policy: open`), it
|
||||
issues a Nostr REQ filtered by `author = peer_pubkey`, `kind = 37195`,
|
||||
`#d = <app>`. The fetch is time-bounded (~2 s) and runs against all
|
||||
configured `advert_relays` in parallel. The first valid advert wins.
|
||||
|
||||
Results are kept in an in-memory cache keyed by author npub. Cache
|
||||
entries carry the advert's expiration time; a periodic prune drops
|
||||
expired entries, and an LRU-by-expiry eviction enforces
|
||||
`advert_cache_max_entries`. A parallel long-lived subscription on the
|
||||
advert relays populates the cache passively, so open-discovery
|
||||
candidates do not require per-dial fetches.
|
||||
|
||||
On cache hit, advert endpoints are appended to the peer's static
|
||||
address list with lower priority; the static list is tried first.
|
||||
|
||||
### Phase 3 — Offer/Answer signaling
|
||||
|
||||
For any endpoint shaped as `udp:nat`, dialing triggers an
|
||||
offer/answer exchange before the first packet is sent. Signaling events
|
||||
are Nostr kind `21059` (ephemeral, not stored by conforming relays),
|
||||
gift-wrapped per [NIP-59](https://github.com/nostr-protocol/nips/blob/master/59.md)
|
||||
and encrypted with [NIP-44](https://github.com/nostr-protocol/nips/blob/master/44.md),
|
||||
so only the intended recipient can decrypt the payload.
|
||||
|
||||
The initiator performs STUN first (see Phase 4), then builds a
|
||||
`TraversalOffer` containing:
|
||||
|
||||
- A unique `sessionId` and a random `nonce` (used to correlate the
|
||||
answer).
|
||||
- Its reflexive address (if STUN succeeded).
|
||||
- Its list of local (private) addresses for same-LAN paths.
|
||||
- The STUN server it used, for informational reporting only.
|
||||
- An `expiresAt` equal to now + `signal_ttl_secs`.
|
||||
|
||||
The offer is sealed to the recipient's npub and published to the peer's
|
||||
preferred signaling relays — the node first tries to resolve the peer's
|
||||
NIP-65 inbox relay list (kind 10002), and falls back to `dm_relays` if
|
||||
the inbox-relays fetch fails. Each side also publishes its own inbox
|
||||
relay list on startup so dialers can discover it.
|
||||
|
||||
On the receiving side, an inbound semaphore bounds concurrent offer
|
||||
processing at `max_concurrent_incoming_offers`. When the semaphore is
|
||||
full, the offer is dropped with a warn log; this is the primary guard
|
||||
against offer-spam from a misbehaving or compromised relay. A
|
||||
`sessionId` replay cache (bounded by `seen_sessions_max_entries`, with
|
||||
entries valid for `replay_window_secs`) rejects duplicates.
|
||||
|
||||
The responder runs its own STUN query and replies with a
|
||||
`TraversalAnswer` carrying its reflexive and local addresses plus a
|
||||
`PunchHint { startAtMs, intervalMs, durationMs }` that tells both sides
|
||||
when to begin probing and how aggressively. If the responder has no
|
||||
usable addresses at all, it replies with `accepted: false` and a
|
||||
`reason` string.
|
||||
|
||||
### Phase 4 — UDP hole-punch
|
||||
|
||||
Each side runs STUN (parsing XOR-MAPPED-ADDRESS from the response, all
|
||||
other attributes ignored) on the *same* UDP socket it will later use
|
||||
for punching and for the adopted FMP transport. This is critical: NAT
|
||||
state is per-socket, so the punch has to reuse the socket that taught
|
||||
the NAT about this binding.
|
||||
|
||||
Given its own reflexive + local addresses and the peer's, each side
|
||||
builds a candidate-pair plan that tries, in priority order:
|
||||
|
||||
1. **Reflexive ↔ reflexive.** The classic STUN path. Tried first because
|
||||
it is the only candidate that's reliable across arbitrary network
|
||||
topologies — host candidates from one peer that happen to be
|
||||
reachable from the other (via a corporate VPN, a Tailscale subnet
|
||||
route, or overlapping private address space) will succeed at the
|
||||
socket layer in the punch but fail in the FMP handshake when the
|
||||
return path doesn't match.
|
||||
2. **LAN ↔ LAN.** If both sides share a /24 prefix, same-subnet private
|
||||
addresses are likely reachable directly. Only fires when both peers
|
||||
shared local host candidates (which requires `share_local_candidates`
|
||||
to be enabled — off by default).
|
||||
3. **Mixed.** Reflexive on one side, local on the other — catches
|
||||
hairpin and one-side-public scenarios.
|
||||
|
||||
At `startAtMs` both sides begin sending 24-byte probe packets on the
|
||||
candidate pair(s) at `intervalMs` cadence for up to `durationMs`. A
|
||||
probe carries a 4-byte magic (`NPTC`), a 4-byte sequence, and the
|
||||
first 16 bytes of `SHA256(sessionId)`; both sides can compute the same
|
||||
session hash independently from the public `sessionId`, so no shared
|
||||
secret is needed on the punch path itself. On receiving a valid probe,
|
||||
a side replies with an `NPTA` ack. The first valid probe or ack seen
|
||||
from the far side records the working remote address and completes the
|
||||
attempt.
|
||||
|
||||
On timeout (`attempt_timeout_secs` as overall bound,
|
||||
`punch_duration_ms` as probe window), both sides issue NIP-9 deletes
|
||||
for their offer and answer events and report failure up to the
|
||||
discovery runtime's `BootstrapEvent::Failed` channel.
|
||||
|
||||
### Phase 5 — Adoption
|
||||
|
||||
On success, the discovery runtime emits `BootstrapEvent::Established`
|
||||
carrying the session id, the punch socket, and the learned remote
|
||||
address. `adopt_established_traversal()` in the node lifecycle takes
|
||||
the socket, registers it with the UDP transport layer as a new
|
||||
transport instance, and calls `initiate_connection()` with the peer's
|
||||
FIPS identity as the expected remote. FMP's Noise IK handshake runs on
|
||||
the same socket — there is no "promote link" step between punch and
|
||||
handshake; the punch socket *is* the FMP socket.
|
||||
|
||||
From that moment on, the connection is a normal FMP link and is
|
||||
subject to the usual liveness (MMP heartbeats), rekey, and removal
|
||||
behavior. A link-dead event does not re-enter the discovery runtime
|
||||
automatically; reconnection relies on `auto_reconnect` and the same
|
||||
dial path that triggered the original punch.
|
||||
|
||||
### Auto-connect semantics
|
||||
|
||||
Discovery does not itself initiate connections. It only supplies
|
||||
addresses. Dial attempts originate from the existing peer-connection
|
||||
machinery:
|
||||
|
||||
- **Configured peers** (`peers[]` with `connect_policy: auto_connect`)
|
||||
are dialed on startup and on retry. When `via_nostr` is set, advert
|
||||
endpoints are appended to the dial list with lower priority than
|
||||
static entries.
|
||||
- **Open discovery peers** are assembled from the advert cache, fenced
|
||||
by the peer ACL, and enqueued into a bounded retry queue sized by
|
||||
`open_discovery_max_pending`. There is no event-driven
|
||||
"connect on every advert" — a peer re-enters the queue only when its
|
||||
prior attempt has drained.
|
||||
- **Manual dials** (`fipsctl connect`) can target any configured peer
|
||||
and use the same dial path, including Nostr resolution if configured.
|
||||
|
||||
### Rate limits and safeguards
|
||||
|
||||
| Mechanism | Default | What it prevents | Behavior at limit |
|
||||
| --- | --- | --- | --- |
|
||||
| Offer semaphore (`max_concurrent_incoming_offers`) | 16 | CPU and memory exhaustion from offer spam on DM relays. | Warn log, offer dropped. |
|
||||
| Advert cache (`advert_cache_max_entries`) | 2048 | Memory growth from ambient advert traffic under `policy: open`. | LRU-by-expiry eviction. |
|
||||
| Seen-sessions (`seen_sessions_max_entries`) | 2048 | Replay of stale `sessionId` values. | Oldest entry evicted. |
|
||||
| Signal TTL (`signal_ttl_secs`) | 120 s | Indefinite in-flight offers on relays. | Expired offers rejected at validation. |
|
||||
| Open discovery queue (`open_discovery_max_pending`) | 64 | Unbounded retry queue under ambient advert load. | New candidates skipped until the queue drains. |
|
||||
| Punch window (`punch_duration_ms`) | 10 s | Endless probe traffic after one side has given up. | Attempt declared failed; sockets discarded. |
|
||||
|
||||
Only one of these (`max_concurrent_incoming_offers`) is a load-shedding
|
||||
mechanism — the rest are capacity bounds. The load-shedding threshold
|
||||
is deliberately conservative so that a misbehaving relay cannot flood
|
||||
the node with offers fast enough to starve legitimate traffic.
|
||||
|
||||
### Relay model
|
||||
|
||||
All configured relays (advert + DM) are opened on a single
|
||||
`nostr-sdk::Client` at startup. Publication is fan-out: the same event
|
||||
is sent to every relay in the target list, with no explicit retry or
|
||||
relay selection. Redundancy is implicit — a downed relay simply means
|
||||
its copy of the advert or signal is unavailable, while other relays
|
||||
still serve the same data.
|
||||
|
||||
For signaling specifically, the node prefers the recipient's NIP-65
|
||||
inbox relays when available (the recipient publishes its inbox list as
|
||||
a kind 10002 event to its own DM relays on startup) and falls back to
|
||||
the local `dm_relays` list otherwise. This keeps the common case
|
||||
off the sender's DM relays when those are different from the
|
||||
recipient's, at the cost of one extra NIP-65 fetch per offer.
|
||||
|
||||
There is no per-relay rate limiting or health check. The relay model
|
||||
assumes that an operator chooses relays they trust to be best-effort
|
||||
available and that outright misbehavior is handled at the offer
|
||||
semaphore and replay-cache layers downstream.
|
||||
|
||||
## Security and threat model
|
||||
|
||||
- **Relay operators can observe metadata.** They see which npubs
|
||||
publish adverts, to whom offers are sent, and the timing of that
|
||||
traffic. The *contents* of offer and answer events are
|
||||
NIP-59/NIP-44 sealed — only the intended recipient decrypts them.
|
||||
Adverts are public by design.
|
||||
- **STUN servers see the node's public IP and port.** Only the STUN
|
||||
servers listed in the node's own `stun_servers` are ever contacted
|
||||
for reflexive discovery. Peer-advertised STUN values are
|
||||
informational; a malicious peer cannot steer this node to a
|
||||
chosen STUN target. See the doc comment on
|
||||
`node.discovery.nostr.stun_servers`.
|
||||
- **The FIPS identity key signs adverts.** Compromise of
|
||||
`fips.key` is compromise of the node's Nostr identity — an attacker
|
||||
can publish adverts on behalf of the node. The recovery path is
|
||||
the same as for any identity compromise: rotate the key and
|
||||
re-advertise. There is no separate Nostr keypair to rotate
|
||||
independently.
|
||||
- **Tor advertising leaks timing via clearnet relays.** When a
|
||||
Tor-only node advertises its onion address, the advert itself is
|
||||
published on clearnet WebSocket relays. Operators who want full
|
||||
unlinkability between the advertising identity and the node's
|
||||
IP must route relay traffic through Tor as well — for example by
|
||||
running `fips` inside a network namespace with a Tor SOCKS
|
||||
proxy as its only egress, or by pointing `advert_relays` and
|
||||
`dm_relays` at onion relay endpoints.
|
||||
- **Open discovery accepts anyone publishing on the same `app`.**
|
||||
Admission control is the peer ACL, not the discovery layer. Verify
|
||||
the ACL before enabling `policy: open`, and consider using a
|
||||
non-default `app` value to scope visibility.
|
||||
- **Nothing about discovery bypasses FMP.** A successful punch yields
|
||||
a UDP socket with a claimed remote identity. That identity is not
|
||||
trusted until FMP's Noise IK handshake completes. A peer whose
|
||||
advert says "I am npub X at 1.2.3.4:5678" but whose FMP handshake
|
||||
presents a different static key is rejected at the mesh layer.
|
||||
|
||||
## See also
|
||||
|
||||
- [fips-configuration.md](fips-configuration.md) — full configuration
|
||||
reference, including all surrounding keys elided from the scenarios
|
||||
above.
|
||||
- [fips-transport-layer.md](fips-transport-layer.md) — UDP, TCP, and
|
||||
Tor transport mechanics; the punch socket is adopted as a normal
|
||||
UDP transport after handoff.
|
||||
- [fips-mesh-layer.md](fips-mesh-layer.md) — FMP Noise IK handshake
|
||||
that runs on the adopted socket.
|
||||
- [../proposals/nostr-udp-hole-punch-protocol.md](../proposals/nostr-udp-hole-punch-protocol.md)
|
||||
— protocol-level reference for event tags, NIP usage, and the
|
||||
on-the-wire offer/answer schema.
|
||||
@@ -695,7 +695,7 @@ X." FMP does not need to distinguish beacons from query responses.
|
||||
| Radio | Beacon | Shared RF channel, natural fit |
|
||||
| BLE | Advertising | GATT service UUID |
|
||||
|
||||
### Nostr Relay Discovery *(future direction)*
|
||||
### Nostr Relay Discovery
|
||||
|
||||
For internet-reachable transports, a node publishes a signed Nostr event
|
||||
containing its FIPS discovery information — public key and reachable
|
||||
@@ -707,6 +707,12 @@ feeds addresses to other transports. A node discovers via Nostr that a peer
|
||||
is reachable at UDP 1.2.3.4:9735, then establishes the link over the UDP
|
||||
transport.
|
||||
|
||||
For NAT'd UDP endpoints, a node may advertise `addr: "nat"` instead of a
|
||||
concrete address, signaling that peers should initiate STUN-assisted UDP
|
||||
hole punching. Offer/answer exchange uses Nostr gift-wrap (NIP-59) events
|
||||
on the configured DM relays; the resulting punched socket is adopted into
|
||||
the standard UDP transport via the bootstrap handoff path.
|
||||
|
||||
Key properties:
|
||||
|
||||
- Identity is built in — Nostr events are signed, so discovery information
|
||||
@@ -723,8 +729,11 @@ Key properties:
|
||||
> broadcast — the `discover()` trait method returns newly seen endpoints,
|
||||
> and per-transport `auto_connect()` / `accept_connections()` policies
|
||||
> control whether discovered peers are connected automatically or require
|
||||
> explicit configuration. TCP and Tor have no discovery mechanism.
|
||||
> Nostr relay discovery is not yet implemented.
|
||||
> explicit configuration. TCP and Tor have no built-in discovery mechanism.
|
||||
> Nostr relay discovery and STUN-assisted UDP hole punching are
|
||||
> implemented behind the `nostr-discovery` cargo feature; see
|
||||
> [fips-configuration.md](fips-configuration.md) for the
|
||||
> `node.discovery.nostr.*` configuration tree.
|
||||
|
||||
## Transport Interface
|
||||
|
||||
|
||||
Reference in New Issue
Block a user