Files
fips/testing/nat
Johnathan Corgan d21f818659 Check that log strings tests match on are still ones the daemon emits
A test that greps the daemon's log for a message the daemon stopped emitting
does not fail. It stops observing, and an assertion built on it — especially
one expecting a count of zero — then passes because nothing can be seen
rather than because nothing happened. Several findings have come from that
one class, so it is now checked mechanically.

testing/check-log-strings.py extracts the strings test code matches against
daemon log text and requires each to exist in src/. It reads four shapes:
python `"..." in line` tests, the first argument of the shell log helpers,
bash associative-array pattern tables, and greps whose input is daemon log
output. Patterns carry regex syntax, so each is reduced to the longest
literal run of every alternation branch, with escaping resolved in the same
pass — `\.` is a literal dot and `.` is a wildcard, and conflating them would
let a pattern match text that is not there.

Scoping is by what a grep READS, not by what its file mentions. A suite greps
its own analyzer output, fipsctl JSON, Tor's log and ping output, and none of
those have to correspond to a string in src/; scoping on the file produced 34
false positives. Strings that legitimately do not come from src/ are named in
ALLOWED with a reason, so the exceptions are reviewable rather than invisible.

It found six dead strings, three of which were not previously known: a second
copy of "Excessive decrypt failures" in the interop pattern table, a dead
"Handshake error" branch inside an alternation whose other branches still
matched, and "bootstrap failed" in the NAT suite. All six are corrected to
what the daemon emits, or dropped where the surviving branch already covers
the case. Verified by breaking it two ways and confirming it reports.

Also here, since it is the same failure shape one layer down: the shared log
library returned an empty string for a container whose logs it could not
read, so analysing a missing container reported no panics, no errors and no
sessions, and exited 0 — indistinguishable from a clean run. It now reports
which containers could not be read and raises, matching the fix already
landed in the chaos copy.
2026-07-23 02:42:25 +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