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Johnathan Corgan
1c93fde672
The incoming-offer semaphore was global with no per-sender accounting and the permit was taken before any identity check, so one sender could hold every slot and deny rendezvous to everyone else. Each sender now has its own allowance with the global count kept as the outer bound. Note what this does and does not do: it raises the cost from one keypair to a small number of them, so a sender willing to spend throwaway identities can still saturate the pool at unchanged total offer rate. The signal freshness bound is only sound while the acceptance window stays strictly inside the replay window, or an offer evicted from the replay cache is still fresh enough to be accepted twice. The relation was stated in a comment and enforced nowhere. Config validation now rejects the bad combination at load, derived from the skew constant rather than a literal, and checked regardless of whether the feature is enabled so that turning it on later cannot surface an error at a surprising moment. The NAT lab config generator produced a combination the new rule rejects and is corrected in the same change. The punch-target filter shipped with no test that would fail if it were reverted. Loopback, link-local and multicast candidates and an oversized list are now covered, and the cap assertion is tightened from a bound to an equality. The private-range inclusion that LAN traversal depends on is pinned as a healthy path so a blanket ban cannot pass. Green: fmt, build, clippy and test --lib, 1533 passed.
FIPS Design
Architectural and protocol-level explanations for FIPS — the why and the how behind the wire and the system. For wire formats and configuration keys, see reference/. For task recipes, see how-to/. For end-to-end lessons, see tutorials/.
Reading Order
Start with fips-concepts.md for the novice-friendly framing of what FIPS is and why, then move to fips-architecture.md for the protocol stack, identity model, and two-layer encryption walkthrough. From there, follow the protocol stack from bottom to top. After the stack, fips-mesh-operation.md explains how the pieces work together at runtime. Cross-cutting and supporting documents cover specific subsystems in detail.
Foundations
| Document | Description |
|---|---|
| fips-concepts.md | What FIPS is, why it exists, mental model |
| fips-architecture.md | Protocol stack, identity, two-layer encryption |
| fips-prior-work.md | Designs and protocols FIPS builds on |
Protocol Stack
| Document | Description |
|---|---|
| fips-transport-layer.md | Transport layer: datagram delivery over arbitrary media |
| fips-mesh-layer.md | FIPS Mesh Protocol (FMP): peer authentication, link encryption, forwarding |
| fips-session-layer.md | FIPS Session Protocol (FSP): end-to-end encryption, sessions |
| fips-ipv6-adapter.md | IPv6 adaptation: TUN interface, DNS, MTU enforcement |
Cross-Cutting
| Document | Description |
|---|---|
| fips-mmp.md | Metrics Measurement Protocol (link + session) |
| fips-mtu.md | Path MTU model, encapsulation overhead, PMTUD |
| fips-security.md | fips0 interface threat model and default-deny baseline |
Mesh Behavior
| Document | Description |
|---|---|
| fips-mesh-operation.md | How the mesh operates: routing, discovery, error recovery |
| fips-nostr-discovery.md | Optional Nostr-mediated peer discovery and UDP NAT hole-punch |
| port-advertisement-and-nat-traversal.md | Nostr-signaled port advertisement and UDP NAT-traversal protocol; generic, with FIPS as an example implementation |
Deeper Dives
| Document | Description |
|---|---|
| fips-spanning-tree.md | Spanning tree algorithms: root discovery, parent selection, coordinates |
| fips-bloom-filters.md | Bloom filter properties: FPR analysis, size classes, split-horizon |
| spanning-tree-dynamics.md | Spanning tree walkthroughs: convergence scenarios, worked examples |
Adjacent Components
| Document | Description |
|---|---|
| fips-gateway.md | fips-gateway service: outbound (LAN-to-mesh) DNS-proxy + virtual-IP NAT and inbound (mesh-to-LAN) port-forwarding, sharing one nftables table |