20cf6932cd
Add a new session-layer error signal that transit routers send back to the source when a forwarded packet exceeds the next-hop transport MTU. This complements the existing proactive path MTU discovery (min'd at each hop) by providing immediate feedback when oversized packets are dropped, closing the transient window before the proactive mechanism converges. Wire format: 36-byte payload (msg_type + flags + dest_addr + reporter + mtu) with FSP phase=0x0 and U flag set, matching the existing CoordsRequired/PathBroken pattern. Changes: - Add SessionMessageType::MtuExceeded (0x22) and MtuExceeded struct with encode/decode methods to protocol/session.rs - Add NodeError::MtuExceeded variant to propagate structured MTU info from TransportError through send_encrypted_link_message() - Catch MtuExceeded in the forwarding path and send error signal back to the datagram source via send_mtu_exceeded_error(), rate-limited by the existing routing_error_rate_limiter - Handle incoming MtuExceeded at the source by calling PathMtuState::apply_notification() for immediate MTU decrease - Add unit tests for encode/decode roundtrip, boundary MTU values, and too-short payload rejection
FIPS: Free Internetworking Peering System
A distributed, decentralized network routing protocol for mesh nodes connecting over arbitrary transports.
Status: Experimental / Pre-release
FIPS is under active development. The protocol and APIs are not stable. Expect breaking changes.
Overview
FIPS is a self-organizing mesh network that operates natively over a variety of physical and logical media — local area networks, Bluetooth, serial links, radio, or the existing internet as an overlay. Nodes generate their own identities, discover each other, and route traffic without any central authority or global topology knowledge.
FIPS uses Nostr keypairs (secp256k1/schnorr) as native node identities, making every Nostr user a potential network participant. Nodes address each other by npub, and the same cryptographic identity used in the Nostr ecosystem serves as both the routing address and the basis for end-to-end encrypted sessions across the mesh.
Features
- Self-organizing mesh routing — spanning tree coordinates and bloom filter candidate selection, no global routing tables
- Multi-transport — UDP/IP overlay today; designed for Ethernet, Bluetooth, serial, radio, and Tor
- Noise encryption — hop-by-hop link encryption plus independent end-to-end session encryption
- Nostr-native identity — secp256k1 keypairs as node addresses, no registration or central authority
- IPv6 adaptation — TUN interface maps npubs to fd00::/8 addresses for unmodified IP applications
- Metrics Measurement Protocol — per-link RTT, loss, jitter, and goodput measurement
- Zero configuration — sensible defaults; a node can run with no config file
Quick Start
Requirements
- Rust 1.85+ (edition 2024)
- Linux (TUN interface requires
CAP_NET_ADMINor root)
Build
git clone https://github.com/jmcorgan/fips.git
cd fips
cargo build --release
Run
# With default configuration (ephemeral identity, default ports):
sudo ./target/release/fips
# With a configuration file:
sudo ./target/release/fips -c fips.yaml
See docs/design/fips-configuration.md for the full configuration reference.
Multi-node Testing
See testing/ for Docker-based integration test harnesses including static topology tests and stochastic chaos simulation.
Documentation
Protocol design documentation is in docs/design/, organized as a layered protocol specification. Start with fips-intro.md for the full protocol overview.
Project Structure
src/ Rust source (library + daemon binary)
docs/design/ Protocol design specifications
testing/ Docker-based integration test harnesses
benches/ Criterion benchmarks
License
MIT — see LICENSE.