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Johnathan Corgan 5abf9a9325 docs: four-section /docs/ restructure with new-user content, accuracy pass, and gateway feature-set rewrite

Restructures /docs/ by reader purpose (tutorials, how-to,
reference, design), adds the new-user-progression and
operator-recipe content the prior layout lacked, runs an
accuracy pass against current source across the pre-existing
design docs, and rewrites the gateway feature-set documentation
end-to-end around its actual operational profile (a niche
feature designed for systems already serving DHCP/DNS to a
LAN, with two independent halves — outbound LAN→mesh, inbound
mesh→LAN — sharing one nftables table, one binary, and one
control socket). Top-level README and getting-started rewritten
around two equally-weighted deployment modes (overlay on
existing IP networks; ground-up over non-IP transports).

## Additions

- 11 new tutorials in docs/tutorials/: an 8-step new-user
  progression from single-daemon test-mesh peering through
  to a ground-up two-device mesh, an IPv6-adapter side-trip
  walkthrough, an Advanced Tutorials index, and a hand-held
  OpenWrt walk-through for fips-gateway deployment that
  exercises both halves of the feature.
- 12 new how-tos in docs/how-to/: firewall activation,
  Nostr discovery (resolve / advertise / open across five
  scenarios), Tor onion (directory + control_port modes),
  UDP buffer tuning, unprivileged-user setup, persistent
  identity, host aliases, Bluetooth LE peering, MTU
  diagnostics, manual Linux-host gateway deployment (covers
  both halves), gateway troubleshooting (organised by half),
  and a section index.
- 9 new reference docs in docs/reference/: configuration,
  wire formats, control-socket protocol, four CLI references
  (fips, fipsctl, fipstop, fips-gateway), security posture
  matrix, and Nostr events catalog. Configuration and
  wire-formats are renamed-and-extended from prior design/
  versions; the other seven are net-new.
- 6 new design docs: fips-concepts, fips-architecture, and
  fips-prior-work split out of the deleted fips-intro.md;
  consolidated fips-mmp and fips-mtu aggregations; and a
  new generic port-advertisement-and-nat-traversal doc
  (Nostr-signaled port advertisement plus UDP NAT-traversal
  protocol, FIPS as an example implementation, suitable for
  eventual NIP submission).
- Top-level docs/getting-started.md walking through the
  binary-installer-only Install story.
- packaging/common/hosts pre-populated with the eight public
  test-mesh nodes so shortnames resolve out of the box on
  every fresh install.

## Changes

- 23 wire-format diagrams relocated to reference/diagrams/
  alongside the wire-formats move.
- 4 design diagrams corrected against source code
  (fips-protocol-stack, fips-identity-derivation,
  fips-coordinate-discovery, fips-routing-decision).
- 10 pre-existing design docs reconciled with current
  source. Numeric corrections: stale link-MMP report bounds
  (now [1s, 5s] with 200 ms cold-start floor); UDP default
  MTU (now 1280, IPv6 minimum); node_addr formula
  (SHA-256(pubkey)[..16]); Noise patterns (IK at link, XK
  at session); peer-ACL semantics (strict allowlist requires
  ALL in peers.deny); daemon DNS upstream ([::1]:5354);
  on-the-wire bloom-filter size (1,071 bytes); obsolete
  Cargo-feature references (PR #79 dropped them) removed.
- Transport framing tightened across the docs: TCP is for
  UDP-filtered networks (not NAT traversal); Tor is a
  deployment mode (not failover); WebSocket dropped (not a
  shipped FIPS transport); WiFi promoted to Implemented via
  Ethernet in infrastructure mode; classic-Bluetooth row
  removed (BLE is the only Bluetooth-mode transport).
- docs/design/fips-gateway.md rewritten end-to-end to lead
  with the niche-feature framing and the two-halves
  structure. Title moved from "FIPS Outbound LAN Gateway"
  to "FIPS Gateway"; architecture section describes the
  common machinery (the fips-gateway service, the nftables
  table, the control socket) before splitting into separate
  "Outbound Half" and "Inbound Half" sections of equal
  weight; security considerations split per-half; no Future
  Work section (speculative directions live in the project
  tracker, not in protocol design docs). Inbound port
  forwarding is a first-class half rather than a buried
  "Implemented Extensions" subsection.
- Gateway terminology unified across all gateway docs as a
  separate Linux service running alongside the fips daemon
  (its own systemd unit / OpenWrt init script). Container-
  pattern terms (sidecar) are reserved for the
  Docker/Kubernetes sidecar deployment examples — the
  testing/sidecar/ tree, examples/k8s-sidecar/,
  examples/sidecar-nostr-relay/,
  examples/wireguard-sidecar-macos/, and the related
  CHANGELOG / top-level README entries — where the term
  carries its standard container meaning.
- Net-new design body content: rekey section in
  fips-mesh-layer (Noise IK msg1/msg2 over the established
  link, K-bit cutover, drain window, smaller-NodeAddr-wins
  tie-breaker on dual-init); Mesh Size Estimation and
  Antipoison FPR Cap sections in fips-bloom-filters;
  Mesh-Interface Query Filter subsection in
  fips-ipv6-adapter; failure-suppression knobs and clock-
  skew tolerance in fips-nostr-discovery; loop-rejection
  and mid-chain ancestor swap added to spanning-tree
  propagation / stability rules; Priority Chain in
  fips-mesh-operation renumbered to match the
  routing-decision diagram.
- Top-level README: dropped the stale nostr-discovery
  cargo-feature parenthetical. docs/README.md and the four
  section READMEs (tutorials, how-to, reference, design)
  refreshed for the new structure; index rows reflect both
  halves of the gateway feature and the new fips-gateway
  CLI reference.
- Cargo.toml [package.metadata.deb] assets path updated for
  the fips-security.md move; .gitignore /reference/ rule
  anchored to repo root so docs/reference/ is trackable.
- packaging/openwrt-ipk/files/etc/fips/fips.yaml
  configuration-doc URL updated to the new
  docs/reference/configuration.md location.

## Deletions

- docs/design/fips-intro.md (split into the three new intro
  design docs).
- docs/design/document-relationships.svg (orphan, no longer
  referenced).
- docs/proposals/ tree removed; the only proposal it
  contained (the Nostr UDP hole-punch protocol) was
  rewritten as the new generic
  design/port-advertisement-and-nat-traversal.md.

2026-05-08 03:02:12 +00:00

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Enable the Mesh-Interface Firewall

FIPS ships a default-deny nftables baseline at /etc/fips/fips.nft that restricts inbound traffic on the fips0 mesh interface to conntrack replies and ICMPv6 echo. The baseline is not enabled by default — see ../design/fips-security.md for the threat model and the rationale behind keeping activation explicit. This guide covers the operator steps to load the baseline, extend it with per-host allowances, and inspect drops.

Activate the baseline

The package ships fips-firewall.service, a systemd oneshot that runs nft -f /etc/fips/fips.nft on start and removes the inet fips table on stop. To activate:

sudo systemctl enable --now fips-firewall.service

This loads the table now and arranges for it to load on every subsequent boot. To disable and tear it down:

sudo systemctl disable --now fips-firewall.service

To reload after editing /etc/fips/fips.nft or adding a drop-in under /etc/fips/fips.d/:

sudo systemctl reload-or-restart fips-firewall.service

The file is idempotent — it begins with add table inet fips; flush table inet fips; so re-running it replaces the live ruleset atomically. Equivalently:

sudo nft -f /etc/fips/fips.nft

Folding the baseline into the host's main nftables

If you prefer to load the baseline from your existing /etc/nftables.conf rather than via the systemd unit, include it directly:

# in /etc/nftables.conf
include "/etc/fips/fips.nft"

In that case do not enable fips-firewall.service — the host's main nftables setup owns the loading. The two paths are mutually exclusive.

Extend with per-host allowances via drop-ins

The baseline drops everything inbound on fips0 except conntrack replies and ICMPv6 echo. To open specific services to specific mesh nodes, drop a file into /etc/fips/fips.d/ ending in .nft. Each file is included inline into the inbound chain at the marked point and may contain any nftables rule lines valid in that context.

Reload after editing:

sudo systemctl reload-or-restart fips-firewall.service
# or:  sudo nft -f /etc/fips/fips.nft

Allow inbound SSH from a specific mesh node

# /etc/fips/fips.d/ssh-from-bastion.nft
ip6 saddr fd97:1234:5678:9abc:def0:1234:5678:9abc tcp dport 22 accept

The source filter is the node's mesh address. To find a node's mesh address, look in their fips.pub (which contains the npub) and derive the fd97:... address from it, or query the running daemon:

fipsctl show identity-cache
fipsctl show peers

Allow inbound DNS broadly

Some services need to be reachable from any mesh node (a public DNS resolver, a public bootstrap node):

# /etc/fips/fips.d/dns-public.nft
udp dport 53 accept
tcp dport 53 accept

Omit the source filter only when the service is intended to be universally reachable on the mesh. The baseline's purpose is to make "universally reachable" an explicit decision rather than the default.

Multiple nodes, one service

# /etc/fips/fips.d/git-from-trusted.nft
ip6 saddr {
    fd97:1111:2222:3333:4444:5555:6666:7777,
    fd97:8888:9999:aaaa:bbbb:cccc:dddd:eeee
} tcp dport 9418 accept

Set syntax keeps multi-node rules readable and is more efficient than a chain of individual rules.

Inspect drops

The baseline counter increments on every dropped packet. Inspect it:

sudo nft list table inet fips

Look for the counter packets N bytes M drop line at the bottom of the inbound chain. A non-zero counter means mesh nodes are sending traffic that hits the default-deny — usually benign (probes, neighbor discovery) but occasionally a misconfigured drop-in.

To see which packets are being dropped, uncomment the log line near the bottom of /etc/fips/fips.nft:

log prefix "fips drop: " level info limit rate 10/minute

Reload:

sudo nft -f /etc/fips/fips.nft

Then tail the kernel log:

sudo journalctl -k -f -g "fips drop:"

The rate-limit prevents flooding the journal under sustained probing. Adjust the rate, log level, or prefix as needed for the situation. Re-comment the rule when you are done; production hosts do not need the log line on by default.

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