Files
fips/testing/nat
Johnathan Corgan 55331a80b5 Gate on shell functions whose exit status is a log call's
A bash function returns its last command's status, so one ending in a log
call returns 0 whatever it did, and a caller written as `if func` or
`func || fail` has a gate that cannot fire. This tree found two in one
day: run_chaos ended in record, making every chaos row unconditionally
green since 2026-03-09, and build_fips_for_e2e ended in log, letting five
end-to-end legs test the previous commit's binary and report green. Both
were repaired one at a time. This is the rule that catches the next one.

What it enforces is a contract, not a bug hunt: a function whose status a
caller tests must end in an explicit return rather than leaving its
success value to whatever the last log call produced. That distinction is
deliberate and worth stating, because all three instances found in the
tree were benign — each failure path already returned early, so the
trailing echo reported a real success. Reading the function is the only
way to know that, and the next edit that puts an unguarded command before
the final log converts the benign shape into the defect with nothing to
notice. An explicit return costs a line and makes the class unreachable.
The three are given one here.

Scoped on the call sites rather than the definitions, the same way
check-log-strings.py scopes on what a grep reads rather than what its file
mentions: 315 functions scanned, 42 end in a log call, and only the ones
whose status something consumes are reported. A function that ends by
reporting and is called for its output is idiomatic and is left alone.
Without that scoping the finding list would be 42 long and would stop
being read.

Validated by construction rather than by a green run: injecting a copy of
build_fips_for_e2e's exact shape — unguarded docker cp, then a log as the
last statement, with a `|| { ...; return 1; }` caller — makes the checker
report it and exit 1.

Wired into both runners beside the parity and log-string checks.
2026-07-23 14:09:04 +00:00
..

NAT Lab Harness

Real Docker-based NAT traversal integration tests for the mainline FIPS Nostr/STUN bootstrap path.

This harness spins up:

  • two FIPS nodes
  • a local Nostr relay
  • a local STUN server
  • one or two Linux router containers performing NAT with iptables

For the NAT scenarios, the node LAN interfaces are not attached to Docker bridge networks. The harness creates explicit veth pairs and moves them into the node and router namespaces after docker compose up so every packet must traverse the router namespace.

It covers three scenarios:

  • cone: both peers behind explicit namespace/veth full-cone emulation, UDP traversal succeeds
  • symmetric: both peers behind symmetric-style NAT, UDP traversal fails, TCP fallback succeeds
  • lan: both peers share a LAN subnet, LAN targets are preferred over reflexive addresses

NAT model notes

The harness does not rely on plain Docker MASQUERADE for the cone case.

  • cone
    • uses explicit full-cone emulation in the router namespace
    • outbound UDP is SNATed to the router WAN address while preserving the source port
    • inbound UDP to the router WAN address is DNATed back to the single LAN host regardless of remote source
  • symmetric
    • uses UDP MASQUERADE --random-fully
    • outbound mappings may be port-randomized and are only reopened by matching conntrack state

This distinction matters because plain MASQUERADE is convenient source NAT, but it does not by itself model the "accept from any remote once mapped" behavior expected from a full-cone NAT.

Prerequisites

  • Docker with Compose support
  • locally built fips-test:latest

Build the test image with:

./testing/scripts/build.sh

Run

Run all scenarios:

./testing/nat/scripts/nat-test.sh

Run one scenario:

./testing/nat/scripts/nat-test.sh cone
./testing/nat/scripts/nat-test.sh symmetric
./testing/nat/scripts/nat-test.sh lan

Layout

  • docker-compose.yml
    • relay/STUN/WAN topology plus container definitions
  • node/
    • node bootstrap wrapper that waits for the injected veth interface
  • router/
    • NAT router image and iptables setup
  • stun/
    • minimal STUN binding responder
  • relay/
    • local strfry config
  • scripts/generate-configs.sh
    • derives ephemeral identities and writes per-scenario FIPS configs
  • scripts/setup-topology.sh
    • injects and configures the NAT LAN veth pairs in the container namespaces
  • scripts/nat-test.sh
    • boots the lab, waits for convergence, and asserts the resulting path

Assertions

  • cone

    • both nodes connect
    • connected transport is UDP
    • active link remote addresses are on the WAN NAT subnet
  • symmetric

    • NAT bootstrap does not establish a UDP link
    • fallback converges
    • connected transport is TCP via router-published WAN addresses
  • lan

    • both nodes connect
    • connected transport is UDP
    • active link remote addresses stay on the shared LAN subnet