Johnathan Corgan
ffe4ff6c71
The path_mtu field is an unsigned per-hop transit annotation carried outside the signed proof, and the MtuExceeded and PathBroken signals arrive unencrypted with no sender check, so any forwarder could lower it and it was accepted with no minimum. A single MtuExceeded carrying a very small value drove a session's path MTU to zero, after which every packet to that destination was answered with an ICMPv6 Packet Too Big instead of being sent: a blackhole lasting until the daemon restarted. The same value reached the SYN-time TCP MSS clamp, where anything at or below 137 saturates to a segment size of zero and the band just above it yields single digits. Ignore values below an actionable minimum rather than applying or storing them, at the three places a remote value is acted on: the path MTU state machine, the reactive MtuExceeded write, and the discovery response, whose coordinates are still cached so refusing the annotation cannot become a way to deny discovery. The MSS clamp additionally refuses to write a zero. Ignoring rather than clamping is deliberate: a clamp would fabricate an estimate the node has no basis for. Release a stored per-destination path MTU when the path is invalidated by a PathBroken report, by session idle expiry, or by handshake timeout, and reseed the link MTU read from local configuration in its place, so a directly connected peer does not lose its own measurement along with the remote claim. Locally derived MTUs are not subject to the minimum, and adaptation to hops well below the IPv6 minimum continues to work. Count and name the path MTU values ignored as below the floor Three sites ignore a remote-supplied path MTU below the actionable floor and one releases a stale entry, and an operator had no way to see any of it happening. Count each site and log the value seen with the destination, so a node being fed poison is distinguishable from a node on a quiet link. Clamp on the degenerate case, not on the remote floor The floor guard at the MSS clamp site tested the stored value alone, with no test of where it came from, so it also rejected the link MTU the node seeds from its own transport. That contradicts the contract the constant's own doc states, and it bites hardest on BLE, where the seeded value is negotiated with the peer rather than read from config: a peer whose effective MTU negotiated to 240 lost a correct 103-byte clamp and got the 1143-byte conservative ceiling, after which every full-size segment was refused by the transport with no signal and no feedback to the application. Every remote value is already refused at the three ingress guards, so a sub-floor value reaching the clamp is by construction a local one. The clamp therefore needs only to refuse the degenerate case it was really about, where no payload byte survives the arithmetic at all. Also retarget the seed-site warning, which fired on the same wrong threshold and advised checking a transport setting that a negotiated link does not have, and correct the constant's doc, which contradicted its own formula about where the single-digit band ends.
FIPS: Free Internetworking Peering System
A self-organizing encrypted mesh network built on Nostr identities, capable of operating over arbitrary transports without central infrastructure.
FIPS is under active development. The protocol and APIs are not yet stable. See Status & roadmap below.
What FIPS does
A machine running FIPS becomes a node in the mesh with a self-generated cryptographic identity (a Nostr keypair). There are two equally-supported deployment modes.
As an overlay on top of existing IP networks, FIPS lets your node reach any other FIPS node wherever it sits — behind a NAT, on a different ISP, on a phone over cellular, on a laptop with only Bluetooth in range, or behind a Tor onion. The mesh forwards IPv6 traffic transparently and end-to-end encrypted, with no central VPN concentrator or coordinating server.
Ground up over raw Ethernet, WiFi, or Bluetooth, FIPS provides a complete permissionless network without any pre-existing IP infrastructure, ISP, or DNS. Any node that joins the link gets routable IPv6 addresses, peer discovery, and a path to every other node automatically.
Either way, existing networking software runs over it unchanged — SSH, HTTP servers, file transfer, anything IPv6-native works the same way it would on a local network.
Features
- Self-organizing mesh routing. Spanning-tree coordinates with bloom-filter-guided discovery; no global routing tables, no flooding.
- Multi-transport. UDP, TCP, Ethernet, Tor, Nym, and Bluetooth (BLE L2CAP) ship today; transports compose on a single mesh and a node may run several at once.
- Two-layer encryption. Noise IK between peers (hop-by-hop) and Noise XK between mesh endpoints (independent end-to-end), with periodic rekey for forward secrecy.
- Nostr-native identity. secp256k1 / schnorr keypairs as node addresses; self-generated, no registration, no central authority.
- IPv6 adapter. A TUN interface maps each remote npub to an
fd00::/8address, so unmodified IPv6 software reaches mesh peers as<npub>.fips. Built-in.fipsDNS resolver, with optional static name mapping via/etc/fips/hosts. - Nostr-mediated discovery and NAT traversal. Peers publish endpoint adverts on public Nostr relays, exchange candidates via NIP-59 gift-wrapped offers and answers, and establish direct paths through NATs using STUN-assisted hole punching. On the local network, mDNS LAN discovery finds peers directly without relays.
- LAN gateway. Optional
fips-gatewayservice folds an entire unmodified LAN into the mesh: outbound (LAN clients reach mesh destinations through a DNS-allocated virtual IPv6 pool and nftables NAT) and inbound (LAN-side services exposed to the mesh through 1:1 port forwards). - Per-link metrics. RTT, loss, jitter, and goodput on every hop, plus mesh-size estimation, via the Metrics Measurement Protocol.
- ECN congestion signaling. Hop-by-hop CE-flag relay with RFC 3168 IPv6 marking and transport kernel-drop detection.
- Mesh-interface security baseline. Optional default-deny
nftables policy for
fips0shipped as a packaged conffile (/etc/fips/fips.nft) with an operator drop-in directory (/etc/fips/fips.d/) and a disabled-by-defaultfips-firewall.service. The baseline polices only the mesh interface, leaving Docker, Tor, and the host firewall untouched. - Operator visibility.
fipsctlCLI for control and inspection with time-series stats history queryable for any metric,fipstopTUI for live status with inline sparkline dashboards, and a JSON-line control socket on each binary for direct programmatic access. - Reproducible builds with toolchain pinning and
SOURCE_DATE_EPOCH.
Quick start
The shortest path on Debian / Ubuntu:
git clone https://github.com/jmcorgan/fips.git
cd fips
cargo install cargo-deb
cargo deb
sudo dpkg -i target/debian/fips_*.deb
sudo systemctl start fips
This installs the daemon, CLI tools (fipsctl, fipstop), the
optional fips-gateway service, systemd units, and a default
/etc/fips/fips.yaml you can edit before starting.
For macOS, Windows, OpenWrt, the systemd tarball, a Nix flake, or a from-source build, see docs/getting-started.md for the full multi-platform installation guide.
To join a live mesh and reach your first peer, follow the new-user tutorial progression starting at docs/tutorials/join-the-test-mesh.md.
Building from source
cargo build --release
Requires Rust 1.94.1+ (edition 2024). Linux, macOS, and Windows are supported; transport availability varies by platform.
| Transport | Linux | macOS | Windows | OpenWrt |
|---|---|---|---|---|
| UDP | ✅ | ✅ | ✅ | ✅ |
| TCP | ✅ | ✅ | ✅ | ✅ |
| Ethernet | ✅ | ✅ | ❌ | ✅ |
| Tor | ✅ | ✅ | ✅ | ✅ |
| Nym | ✅ | ✅ | ✅ | ❌ |
| BLE | ✅ | ❌ | ❌ | ❌ |
On Linux, a source build requires libclang — the LAN gateway's
nftables bindings are generated by bindgen at build time, which
needs libclang.so on the build host. Install it before building
(sudo apt install libclang-dev on Debian / Ubuntu); without it the
build fails inside the rustables crate with an "Unable to find
libclang" error. This is a build-time prerequisite only — it is not a
runtime dependency, and the pre-built .deb artifacts do not need it.
BLE is optional and, on Linux, requires BlueZ and libdbus
(sudo apt install bluez libdbus-1-dev on Debian / Ubuntu). It is
gated on a build-script probe — install the dependencies first and
the cargo build line above picks it up. The OpenWrt ipk omits
BLE because libdbus is not available on the target.
Nym (mixnet) transport builds on all desktop platforms. The OpenWrt
❌ is provisional, pending verification of nym-socks5-client
availability on the target; it will flip to ✅ only if confirmed
buildable there.
Alternatively, the repo ships a Nix flake: nix develop
drops you into a shell with the pinned toolchain and every build
prerequisite (libclang, dbus, pkg-config) already provided, and
nix build .#fips builds all four binaries with no host setup. See the
Nix / NixOS section of packaging/README.md.
Documentation
docs/ is organised by reader purpose:
- Tutorials — hand-held walk-throughs from a fresh install through to a participating mesh node, plus advanced deployments (gateway on OpenWrt, hosting services, ground-up two-device mesh).
- How-to guides — operator recipes for specific tasks: firewall activation, Nostr discovery, Tor onion service, Bluetooth peering, LAN gateway deployment and troubleshooting, MTU diagnostics, host aliases, persistent identity, unprivileged-user setup, UDP buffer tuning.
- Reference —
fips.yamlconfiguration, wire formats, control-socket protocol, CLI references for each binary, security posture matrix, Nostr events catalog, transport statistics inventory. - Design — protocol-level architecture and layer specifications. Start with fips-concepts.md for the framing, then fips-architecture.md for the protocol stack.
If you want to contribute, see CONTRIBUTING.md and testing/README.md.
Examples
- examples/sidecar-nostr-relay/ — Run a strfry Nostr relay reachable exclusively over the FIPS mesh. The relay container shares the FIPS sidecar's network namespace and is isolated from the host network.
- examples/sidecar-nostr-mixnet-relay/ — Single-container demo of FIPS peering through a mixnet (implemented with Nym): the FIPS daemon, the mixnet proxy, and a strfry Nostr relay all in one isolated container, with the direct route to the peer firewalled off so traffic provably crosses the mixnet.
- examples/k8s-sidecar/ — Run FIPS as
a Kubernetes Pod sidecar. The sidecar creates
fips0in the Pod's shared network namespace so every other container in the Pod gets mesh access without modification. - examples/wireguard-sidecar-macos/ —
Reach the FIPS mesh from a macOS host through a local Docker
container over a WireGuard tunnel. Only traffic destined for
fd00::/8transits the sidecar; regular internet traffic continues to use the host network.
Project structure
src/ Rust source: library + fips, fipsctl, fipstop, fips-gateway binaries
docs/ Documentation: tutorials, how-to, reference, design
packaging/ Debian, macOS .pkg, Windows ZIP, OpenWrt ipk, AUR, systemd tarball
examples/ Deployment examples (Nostr relay, K8s sidecar, macOS WireGuard)
testing/ Docker-based integration test harnesses + chaos simulation
Status & roadmap
FIPS is at v0.4.2-dev on the maint branch.
v0.4.1 has
shipped; this line carries patch-level fixes for the 0.4.x series. The
core protocol works end-to-end over
UDP, TCP, Ethernet, Tor, Nym, and Bluetooth on a global, public test
mesh of thousands of nodes. v0.4.0 added the Nym mixnet transport and
mDNS LAN discovery alongside the existing Nostr-mediated peer discovery,
UDP NAT traversal, peer ACL, and packaging hardening. New wire-format work
continues to be staged on the next branch for the subsequent
release line.
What works today
- Spanning-tree construction with greedy coordinate routing.
- Bloom-filter-guided destination discovery (no flooding, single-path with retry).
- Two-layer Noise encryption (IK at the link, XK at the session) with periodic hitless rekey for forward secrecy at both layers.
- Persistent or ephemeral node identity with key-file management.
- IPv6 TUN adapter with built-in
.fipsDNS resolver and multi-backend auto-configuration (systemd dns-delegate, systemd-resolved, dnsmasq, NetworkManager). - Static hostname mapping (
/etc/fips/hosts) with auto-reload. - Per-link metrics (RTT, loss, jitter, goodput) and mesh size estimation.
- ECN congestion signaling (hop-by-hop CE relay, IPv6 CE marking, kernel-drop detection).
- UDP, TCP, Ethernet, Tor, Nym (mixnet), and BLE transports (BLE via L2CAP CoC with per-link MTU negotiation).
- Nostr-mediated overlay endpoint discovery and UDP hole punching for NAT traversal, plus mDNS LAN discovery for local peers.
- LAN gateway (
fips-gateway) with both outbound (LAN-to-mesh) and inbound (mesh-to-LAN port-forwarding) modes. - Peer ACL: per-npub allow / deny admission control at the link
layer; opt-in mesh-firewall baseline at
fips0ingress. - Runtime inspection and peer management via
fipsctlandfipstop. - Reproducible builds with toolchain pinning and
SOURCE_DATE_EPOCH. - Linux (Debian, systemd tarball, OpenWrt, AUR), macOS (
.pkg), and Windows (ZIP, service) packaging. - Docker-based integration and chaos testing.
Near-term priorities
- Native API for FIPS-aware applications (npub:port addressing without the IPv6-shim path).
- Security audit of the cryptographic protocols.
Longer-term
- Mobile platform support.
- Bandwidth-aware routing and QoS.
- Protocol stability and a versioned wire format.
- Published crate.
License
MIT — see LICENSE.