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A kernel built without CONFIG_NF_CONNTRACK_PROCFS, such as Ubuntu's, has no /proc/net/nf_conntrack. The gateway then counted zero sessions for every mapping, so a mapping still carrying traffic was reclaimed on its TTL and grace period alone. When the proc file is absent, the gateway now dumps the IPv6 conntrack table over NETLINK_NETFILTER, the request conntrack -L makes, and counts each entry once per distinct destination, the same rule the proc parser applies. The choice is made on every read, because the proc file appears only once nf_conntrack is loaded. Any other proc error is still reported without falling back. When both sources fail, the per-tick warning carries the netlink error, and the startup line names both errors. The dump uses netlink-packet-netfilter 0.3, the release built on the netlink-packet-core 0.8 that rtnetlink already uses. The gateway suite now expects the netlink source line when the container has no proc file, and checks that the gateway counts the session left by the HTTP request through the first virtual IP.
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 |
| fips-native-api.md | Native datagram API: pubkey-addressed flows over FSP, and what it is instead of the TUN path |
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 |