Johnathan Corgan
6a564e26ac
Everything the release needs except the version number, which stays at 0.5.0-dev until the tag. The changelog entry covers only the work that is new on this line. The point release's forty-six entries arrived under their own heading with the forward merge and are left alone; the twenty that remained are regrouped by topic and eight more added for changes no entry covered. Three of those eight matter to someone upgrading. Five root modules and four re-exports left the public library surface and Node::connections narrowed, none of it recorded anywhere; the entry names what to use instead and distinguishes the removed connection-phase enum from the Noise type of the same name, which is a different type that still exists. Tracing targets moved, so an existing RUST_LOG filter stops matching rather than erroring. And the handshake resend interval key no longer governs the first resend, which is now a constant, though it still governs later ones. Seven more entries cover the work that landed after the first content pass was written: the experimental native datagram API, the fipsctl probe diagnostic, per-instance transport addressing, the app-owned UDP socket seam, and the connect, disconnect and path-MTU fixes. The four bug fixes among them all reach the deployed line, so the release notes no longer claim this release carries exactly one fix for a shipped bug; it carries four. There is no security section, because after the split every security entry belongs to the point release. The release notes say so plainly rather than leaving a reader upgrading across both releases to conclude this one carries no security work. The notes are organized by audience, since the release spans OpenWrt routers, embedders, FreeBSD, and the existing platforms, and a single list serves none of them. The native datagram API is given a section of its own rather than folded into the embedding seam: it is a client-facing API rather than a way to host a node, and its one rule with no Berkeley-socket counterpart, that the v1 wire carries no half-close, needs to be somewhere a client author will read it. FreeBSD is advertised as supported on x86_64 only, stated wherever the platform appears. Android is advertised as an embedding seam and not as a supported platform: a compile-gated library surface with no artifact and no host application guide. The configuration table rename is carried through every shipped file that taught the old spelling: nine documentation files, the OpenWrt sample config and a test generator, twenty-two sites in all. Guides written this same cycle were among them, which is how the omission was found. The documentation that arrived with the native API was checked for the same omission and was already clean. The compatibility tests keep the old spelling deliberately, since they exist to test the fold. The changelog section is the fold of master's [Unreleased], not a snapshot of it. An earlier version of this commit took a copy that then drifted, so each section ended up holding a bullet the other did not and re-folding them would have picked a winner silently. Both causes were fixed on master instead — the NixOS module had never been recorded there, and the pre-release batch of fixes was new — so [Unreleased] is a strict superset and this is a copy rather than a merge. [0.5.0] carries all forty-six bullets byte for byte, [Unreleased] is empty, and [0.4.2] is untouched, checked by hashing it against master's copy. The BLE work landed after the content pass and gets one summary entry in the changelog and one section in the release notes rather than nine bullets: the ble_available gate replacing target_os = "linux", packet-boundary recovery for stream-oriented backends, peer recognition by node identity instead of a rotating link address, the L2CAP PSM moving into the backend seam and onto the advertisement, the embedder-supplied Android radio, bounded probe retry, and inbound handshakes moved off the accept loop. The two release-notes copies no longer share their link paths. Relative links resolve from one directory only, so the seven written for docs/releases/ all 404ed from the root copy. The root copy now uses paths from the repository root and the versioned copy keeps the ../ form; both sets were resolved against the tree. The same two links are broken the same way in the v0.4.0 through v0.4.2 notes, left as shipped history. The contributor tallies are re-derived against maint..HEAD rather than adjusted: twenty commits from outside the project and 171 from me, with Arjen at fifteen and fr34aky at two. An earlier count of twelve and 138 was carried from a measurement taken three days before this content was written, and the BLE branch widened the gap after it. Arjen's NixOS flake module, the UDP sin6_scope_id fix and most of the BLE rework were uncredited, as was fr34aky's L2CAP PSM seam. They want one last re-derive at tag time if anything lands before the tag. A sweep of all 99 tracked markdown files against the tree corrected fifty-three of them. Four told the reader to run a build.sh that does not exist; the only harness builder is testing/scripts/build.sh. The BLE build prerequisites were described as optional on the strength of a probe that build.rs does not perform, and bluez was named a build prerequisite when libdbus-sys asks only for libdbus-1-dev and pkg-config and bluez is the runtime daemon. Link cost is the primary sort key in next-hop ranking, not reserved for future use; Ethernet runs on macOS as well as Linux; the BLE MTU is the L2CAP CoC MTU rather than a negotiated ATT_MTU; effective Ethernet MTU is 1497; the LAN discovery subsystem is src/mdns and eight citations still named a src/discovery that never existed here. The connectivity states in three tutorials were invented, and their jq filters matched nothing including healthy peers. One command filtered on a literal fd97: address prefix, which only the first byte of fixes, so it returned empty for all but one reader in 256 and every later step using the variable failed silently. transports.tor.advertise_on_nostr was undocumented despite being validated against node.rendezvous.nostr.enabled. The transport design document gains the BLE section it never had, written from the source: the backend cascade and its compile_error tripwire, the platform gate, the PSM advertisement wire layout and the byte budget that forces a 16-bit service-data key, and the probe and admission bounds. Three source files carried the same class of staleness and are corrected with the documentation: the OpenWrt ipk usage line and Makefile error text both named a packaging/openwrt that does not exist, and chaos.sh parsed --subnet without listing it. Folded in with the content commit, having been prepared alongside it: The three GitHub Action pins that had gone stale. Every third-party action is pinned to a commit SHA, nothing reports that a pin has aged, and re-resolving all ten against their tags found dorny/test-reporter@v2, taiki-e/install-action@v2 and vmactions/freebsd-vm@v1 had moved. The three install-action@nextest references stay unpinned, since that action reads the tool to install from the ref name. check-action-pins.sh passes at 75 references and all nine workflow files parse. The lockfile refresh, which is the mutating half of the dependency sweep. Thirty-six packages move to their latest semver-compatible versions and every one is transitive; nothing declared in Cargo.toml changes version. No advisory forces any of them. It was taken before the validation battery, because a gate run against a lockfile that later moves proves nothing about what ships. The sha2 0.10 to 0.11, hkdf 0.12 to 0.13 and bech32 0.11 to 0.12 majors, three of the four deferred at v0.4.0 for change surface rather than security. All three land with no source change. sha2 and hkdf must move together, since both depend on digest 0.11, and neither changes an algorithm. That matters because the chaining-key KDF in the Noise handshake is built on Hkdf::<Sha256>, where an output change would be a wire break rather than a compile error; no known-answer vectors exist for that path, so the wire-compatibility gate is what covers it. secp256k1 0.31 is deliberately absent, since nostr's own requirement would leave two copies of the ECC library in the tree. The README support matrix, rebuilt as one feature table broken out by Linux variety. A single Linux column hid that Debian, Ubuntu, Arch and NixOS are one glibc build differing in packaging, that OpenWrt is musl and drops BLE, and that Android is not a daemon platform. Transport rows sort by how many platforms carry them. A Native API row reads its platform set from the cfg gates. The installer row becomes a package format row naming the artifact, and only the .deb is exercised per release. Four changelog and release-note gaps the BLE re-walk found: a Bluetooth LE bullet stranded inside the released 0.4.2 section, a missing Fixed entry for the scan and probe loop counting a pool-refused connection as an established link, the unnamed embedder call that installs an application-owned radio, and the fact that stopping the transport now stops scanning as well as advertising. Three release-document gaps found walking the unsurveyed commits: the UDP reuse-flag fix stated in the direction opposite to the one it was made, with the silent second-daemon bind it prevents left unsaid; the corrected native-API socket paragraph carried into both release-note copies, which still named SOCK_SEQPACKET on FreeBSD and two kernels where three are handled; and the coordinate-cache hardening, which shipped with no text anywhere despite adding four operator-visible status fields. That last entry states plainly that the checks are mitigations and not a closure, since the coordinate is still not authenticated. Also folded in, the documentation pass that followed the content commit: A stage-pipeline diagram for the probe, embedded in the fipsctl reference under the five-stage list. It draws the five stages left to right with each stage's failure reasons below it, and the bypass that skips both lookup stages when the coordinates are cached or the target is a direct peer. Its branches come from the probe state machine rather than from the report, so the path stage is drawn as the one failure that does not stop the probe. A rewrite of the README's "What FIPS does" section. It now opens with what a machine running FIPS gets, rather than with the two deployment modes, and gives the self-organizing and permissionless property its own paragraph since it holds for both modes. A regrouping of the README's feature list into the mesh, getting traffic onto it, and running a node, with a bullet added for the native datagram API, which had none despite sitting in the support matrix. The Quick start now leads with the released packages rather than a source build. It also fixes a real defect: the package enables fips.service and fips-dns.service and starts neither on a fresh install, so .fips name resolution was silently dead until the next reboot and neither page said to start the service. A rewrite of the release notes. They opened with seven subsections of upgrade caveats and reached the first feature two hundred lines in; they now open with a summary of the release and elaborate below it in the same order. Android is stated as supported through an embedded crate rather than as a standalone daemon, consistently across all three documents. The OpenWrt pair is corrected: it is 802.11s between routers with FIPS supplying encryption, authentication and routing, plus a convention of an open !FIPS SSID a client joins over WiFi, not meshing over a router's own radios. The probe's path output is described as the least-common-ancestor walk, which is the worst-case fallback route rather than the route a packet takes. Detail that did not change what a reader does was cut from the notes and kept in the changelog.
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FIPS Prior Work and References
FIPS builds on proven designs rather than inventing new cryptography or routing algorithms. Nearly every major design decision has deployed precedent. This document collects the relevant prior art, organized by the FIPS subsystem that draws on it, and gathers the academic and standards references cited from the per-subsystem design docs.
Spanning Tree Self-Organization
The idea that distributed nodes can build a spanning tree through purely local decisions — each node selecting a parent based on announcements from its neighbors — dates to the IEEE 802.1D Spanning Tree Protocol (STP, 1985). STP demonstrated that a network-wide tree emerges from a simple deterministic rule (lowest bridge ID wins root election) applied independently at each node. FIPS uses the same principle — lowest node address determines the root — adapted from an Ethernet bridging context to a general-purpose overlay mesh.
Tree Coordinate Routing
The spanning tree coordinates, bloom filter candidate selection, and greedy routing algorithms are adapted from Yggdrasil v0.5 and its Ironwood routing library. Yggdrasil's key insight was using the tree path from root to node as a routable coordinate, enabling greedy forwarding without global routing tables. FIPS adapts these algorithms for multi-transport operation, Nostr identity integration, and constrained MTU environments.
The theoretical foundation for greedy routing on tree embeddings draws on Kleinberg's work on navigable small-world networks, which showed that greedy forwarding succeeds in O(log² n) steps when the network has hierarchical structure. Thorup-Zwick compact routing schemes separately demonstrated that sublinear routing state is achievable with bounded stretch, motivating the use of tree coordinates rather than full routing tables.
Split-Horizon Bloom Filter Propagation
FIPS distributes reachability information using bloom filters computed with a split-horizon rule: when advertising to a peer, exclude that peer's own contributions. This technique is borrowed from distance-vector routing protocols — RIP (1988) and Babel use split-horizon to prevent routing loops by not advertising a route back to the neighbor it was learned from. FIPS applies the same principle to probabilistic set advertisements rather than distance-vector tables.
Cryptographic Identity as Network Address
FIPS nodes are identified by their Nostr public keys (secp256k1). The network address is the cryptographic identity — there is no separate address assignment or registration step. CJDNS pioneered this approach in overlay meshes, deriving IPv6 addresses from the double-SHA-512 of each node's public key. Tor .onion addresses and the IETF Host Identity Protocol (HIP) follow the same principle. FIPS uses Nostr's existing key infrastructure rather than introducing a new identity scheme.
Dual-Layer Encryption
FIPS encrypts traffic twice: FMP provides hop-by-hop link encryption (protecting against transport-layer observers), while FSP provides independent end-to-end session encryption (protecting against intermediate FIPS nodes). This layered approach mirrors Tor, where each relay peels one layer of encryption (hop-by-hop) while the innermost layer protects end-to-end payload. I2P uses a similar garlic routing scheme with tunnel-layer and end-to-end encryption. Unlike Tor and I2P, FIPS does not provide anonymity — its dual encryption protects confidentiality and integrity rather than hiding traffic patterns.
Noise Protocol Framework
FIPS uses the Noise Protocol Framework at both protocol layers, with different handshake patterns chosen for each layer's threat model. FMP link encryption uses Noise IK, providing mutual authentication with a single round trip where the initiator knows the responder's static key in advance. WireGuard uses the same IK base pattern (extended with a pre-shared key as IKpsk2) for VPN tunnels. FSP session encryption uses Noise XK, the same pattern used by the Lightning Network, where the initiator's static key is transmitted in a third message rather than the first. XK provides stronger initiator identity hiding at the cost of an additional round trip — a worthwhile tradeoff for session-layer traffic that traverses untrusted intermediate nodes. At the link layer, where both peers are configured and directly connected, IK's single round trip is preferred.
Specific Noise references and adapted constructions:
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Perrin, T. "The Noise Protocol Framework". Revision 34, 2018. Framework for building crypto protocols using Diffie-Hellman key agreement and AEAD ciphers. FSP uses the XK handshake pattern.
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Donenfeld, J.A. "WireGuard: Next Generation Kernel Network Tunnel". NDSS 2017. Transport-independent cryptographic sessions bound to identity keys rather than network addresses; AEAD-only authentication model.
Index-Based Session Dispatch
FIPS uses locally-assigned 32-bit session indices to demultiplex incoming packets to the correct cryptographic session in O(1) time, without parsing source addresses or performing expensive lookups. This directly follows WireGuard's receiver index approach, where each peer assigns a random index during handshake and the remote side includes it in every packet header.
Replay Protection Over Unreliable Transports
FSP and FMP both use explicit per-packet counters with a sliding bitmap window for replay protection — the standard DTLS approach, chosen because implicit nonce counters desynchronize permanently under UDP packet loss or reordering.
- Rescorla, E., Modadugu, N. RFC 6347: "Datagram Transport Layer Security Version 1.2". 2012. Explicit sequence numbers with sliding bitmap window for replay protection over unreliable transports.
Transport-Agnostic Overlay Mesh
FIPS is designed to operate over any datagram-capable transport — UDP, raw Ethernet, Bluetooth, radio, serial — through a uniform transport abstraction. Several mesh overlays have demonstrated transport-agnostic design: CJDNS runs over UDP and Ethernet, Yggdrasil supports TCP and TLS transports, and Tor can use pluggable transports to tunnel through various media. FIPS extends this pattern to shared-medium transports (radio, BLE) with per-transport MTU and discovery capabilities.
Metrics Measurement Protocol
MMP's design assembles well-established measurement techniques into a unified per-link protocol. The SenderReport/ReceiverReport exchange structure follows RTCP (RFC 3550), which uses the same report pairing for media stream quality monitoring in RTP sessions. MMP's jitter computation uses the RTCP interarrival jitter algorithm directly.
The smoothed RTT estimator uses the Jacobson/Karels algorithm (RFC 6298), the same SRTT computation used in TCP for retransmission timeout calculation since 1988. MMP derives RTT from timestamp-echo in ReceiverReports with dwell-time compensation, rather than from packet round-trips.
The spin bit in the FMP frame header follows the QUIC spin bit (RFC 9312) — a single bit that alternates each round trip, enabling passive latency measurement. FIPS implements the spin bit state machine but relies on timestamp-echo for SRTT, as irregular mesh traffic makes spin bit RTT unreliable.
The Expected Transmission Count (ETX) metric, computed from bidirectional delivery ratios, was introduced by De Couto et al. (2003) for wireless mesh routing and is used in protocols including OLSR and Babel. FIPS computes ETX per-link from MMP loss measurements and uses it for cost-based parent selection and as the primary key in next-hop candidate ranking.
The CE (Congestion Experienced) echo flag provides hop-by-hop ECN signaling, following the TCP/IP ECN echo pattern (RFC 3168). Transit nodes detect congestion via MMP loss/ETX metrics or kernel buffer drops and set the CE flag on forwarded frames; destination nodes mark ECN-capable IPv6 packets accordingly.
Path MTU Discovery
FSP adapts RFC 1191 Path MTU Discovery for overlay networks. The
classic ICMP Packet Too Big mechanism is replaced by a transit-node
min() propagation in SessionDatagram and LookupResponse plus an
end-to-end PathMtuNotification echo back to the source.
- Mogul, J., Deering, S. RFC 1191: "Path MTU Discovery". 1990. End-to-end path MTU discovery; FSP adapts this for overlay networks using transit-node min() propagation.
Session Restart and Simultaneous Initiation
FSP's epoch-based peer restart detection mirrors IKEv2's INITIAL_CONTACT notification, and its lowest-address-wins simultaneous-initiation tie-breaker mirrors IKEv2's resolution rule.
- Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., Kivinen, T. RFC 7296: "Internet Key Exchange Protocol Version 2 (IKEv2)". 2014. Simultaneous initiation resolution (§2.8) and INITIAL_CONTACT peer restart detection (§2.4).
Hybrid Coordinate Warmup
FSP's hybrid coordinate warmup (CP flag piggybacking + standalone CoordsWarmup) draws on Yggdrasil's approach of embedding coordinates in session traffic to keep transit caches populated.
- Yggdrasil Network. Coordinate-based overlay routing with session traffic used to warm transit node coordinate caches.
Cryptographic Primitives
FIPS reuses Nostr's cryptographic stack — secp256k1 for identity keys, Schnorr signatures for authentication, SHA-256 for hashing, and ChaCha20-Poly1305 for authenticated encryption. This is the same primitive set used across Bitcoin, Nostr, and a growing ecosystem of self-sovereign identity systems. No novel cryptography is introduced.
Spanning-Tree Dynamics: Foundations
The CRDT framing, gossip dissemination, failure detection, link metrics, and route stability mechanisms in spanning-tree-dynamics.md draw on a body of academic and standards work, summarized below.
Virtual Coordinate Routing
- Rao, A., Ratnasamy, S., Papadimitriou, C., Shenker, S., Stoica, I. "Geographic Routing without Location Information". MobiCom 2003. Established virtual coordinate routing using network topology.
Greedy Embedding Theory
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Kleinberg, R. "Geographic Routing Using Hyperbolic Space". IEEE INFOCOM 2007. Proved every connected graph has a greedy embedding in hyperbolic space; showed spanning trees enable coordinate assignment.
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Cvetkovski, A., Crovella, M. "Hyperbolic Embedding and Routing for Dynamic Graphs". IEEE INFOCOM 2009. Dynamic embedding for nodes joining/leaving; introduced Gravity-Pressure routing for failure recovery.
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Crovella, M. et al. "On the Choice of a Spanning Tree for Greedy Embedding". Networking Science 2013. Analysis of how tree structure affects routing stretch.
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Bläsius, T. et al. "Hyperbolic Embeddings for Near-Optimal Greedy Routing". ACM Journal of Experimental Algorithmics 2020. Achieved 100% success ratio with 6% stretch on Internet graph.
Link Metrics
- De Couto, D., Aguayo, D., Bicket, J., Morris, R. "A High-Throughput Path Metric for Multi-Hop Wireless Routing". MobiCom 2003. Introduced ETX (Expected Transmission Count) as a link quality metric for wireless mesh networks.
Routing Protocol Stability
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IEEE 802.1D. "IEEE Standard for Local and Metropolitan Area Networks: Media Access Control (MAC) Bridges". Spanning Tree Protocol (STP) — root election via bridge ID, BPDU exchange.
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Moy, J. RFC 2328: "OSPF Version 2". 1998. Link-state routing with cumulative path costs and SPF computation. FIPS's local-only cost approach is contrasted with OSPF's cumulative model in spanning-tree-dynamics.md §8.
Distributed Systems Primitives
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Shapiro, M., Preguiça, N., Baquero, C., Zawirski, M. "Conflict-free Replicated Data Types". SSS 2011. Formal definition of CRDTs enabling coordination-free consistency.
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Das, A., Gupta, I., Motivala, A. "SWIM: Scalable Weakly-consistent Infection-style Process Group Membership". IPDPS 2002. O(1) failure detection, O(log N) dissemination via gossip.
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Kermarrec, A-M. "Gossiping in Distributed Systems". ACM SIGOPS Operating Systems Review 2007. Framework for gossip-based protocols achieving O(log N) propagation.
FIPS Contributions
The protocol builds on these foundations and adds several new elements:
- Cost-aware parent selection using local-only link metrics
(
effective_depth = depth + link_cost), replacing Yggdrasil's depth-only selection - Combined ETX + SRTT link cost formula with MMP-measured components
- Flap dampening with mandatory switch bypass
- Announcement suppression for transient state changes
- Tree-only bloom filter merge with split-horizon exclusion
- Hybrid coordinate warmup (CP flag piggybacking plus standalone CoordsWarmup) layered on top of SessionSetup self-bootstrapping
- Bloom-guided tree routing for discovery (vs. flooding)
- Reverse-path routing for LookupResponse via
recent_requests
External Reference Index
| Reference | Used by |
|---|---|
| IEEE 802.1D STP | spanning tree, root election |
| Yggdrasil v0.5 | tree coordinates, greedy routing |
| Ironwood | tree coordinates, candidate ranking |
| Kleinberg, Small-world | greedy routing on tree embeddings |
| CJDNS | cryptographic-identity-as-address |
| Tor | onion address scheme, dual-layer encryption |
| I2P | dual-layer encryption (garlic routing) |
| HIP | identity-as-address |
| Babel | split-horizon, ETX |
| RIP | split-horizon |
| Noise Framework | FMP IK, FSP XK |
| WireGuard | IK pattern, receiver-index dispatch, identity-bound sessions |
| Lightning BOLT #8 | XK pattern |
| QUIC (RFC 9000) | spin bit, transport design |
| QUIC Spin Bit (RFC 9312) | passive RTT measurement |
| RTCP (RFC 3550) | sender/receiver report structure, jitter algorithm |
| TCP SRTT/RTO (RFC 6298) | Jacobson/Karels SRTT |
| ECN (RFC 3168) | CE echo |
| DTLS 1.2 (RFC 6347) | replay window |
| IKEv2 (RFC 7296) | INITIAL_CONTACT, simultaneous-initiation tie-breaker |
| PMTUD (RFC 1191) | adapted PMTUD |
| ETX paper, De Couto et al. | ETX metric |
| OLSR | ETX in mesh routing |
| Nostr | identity stack |