fips/testing/interop

Mixed-Version Interop Test Harness

A CI lab harness for mixed-version interoperability testing. It runs an N-node full mesh where nodes run different builds of the FIPS daemon, and checks that every pair of versions interoperates — FMP link, FSP session, connectivity, and rekey survival — without a failure a same-version pair would not have.

What it tests

The static/rekey suites bake one binary set for all nodes, so they only ever test a version against itself. This harness breaks that assumption: each node runs an image built from its own git ref. The harness then looks for interop regressions — places where two different versions fail to interoperate:

• FMP handshake failures across versions
• unknown FMP version drops
• FSP / FMP AEAD decrypt failures
• replay storms / excessive-decrypt-failure removals
• link or session teardowns
• asymmetric connectivity drops
• rekey (FMP link + FSP session) that completes within a version but stalls or breaks across versions

Every failure is attributed to a specific version pair, classified same-version vs MIXED. The summary states whether failures are mixed-version-only (a genuine interop regression), both mixed and same (general instability), or same-version-only (a build is unstable even against itself).

The node-spec

The harness is parameterized by a node-spec: a multiset of image slots, of size >= 2. Each slot is one of a, b, c, and the same slot may appear more than once. The slots resolve to the three images built by build-images.sh:

Slot	Role	Intended ref
a	version under test	the branch tip / commit to vet
b	parent / comparison	parent commit on the same branch
c	release baseline	latest release tag (v0.3.0)

build-images.sh is unchanged — it always builds exactly three images from three refs. A node-spec like a a b c resolves to the same three images; only the mesh topology grows.

Node identity vs image slot

Node identity and image slot are separate:

• A spec entry is a slot letter.
• Node id = <slot><ordinal>, ordinal counting occurrences of that slot, 1-based.
• Container name = fips-interop-<nodeid>.
• IPv4 = 172.30.0.1<index>, index = 0-based position in the spec (.10, .11, .12, ...).
• Each node maps to its image slot: a1, a2 → fips-interop:a.
• A pair is same-version iff the two nodes' slots resolve to the same built SHA (read from .build/refs.env); else MIXED.

Two same-slot nodes get distinct identities — derive_keys.py is keyed by node id, so a1 and a2 are different npubs even though they run the same binary.

Example specs

Node-spec	Node ids	Pairs
a b c	a1 b1 c1	3 pairs, all MIXED — today's triangle (default).
a a b c	a1 a2 b1 c1	6 pairs: a1↔a2 same + 5 MIXED.
a a a	a1 a2 a3	3 pairs, all same — a same-version flake rig.

Why the a a b c control topology matters

The triangle a b c has no same-version pair — every pair is mixed, so under packet loss you cannot tell an interop regression from generic loss noise. The a a b c spec adds a control arm: the a1↔a2 pair runs identical binaries. Under a netem stress loop:

• a failure on a mixed pair the control pair does not share → an interop regression;
• a failure both the mixed pairs and the control pair share → loss-induced instability, not version-specific.

That control pair is what makes a stress run interpretable. It is the default node-spec for interop-stress.sh.

The a a a spec is the degenerate case: all-same-version, used purely as a flake rig — exercising a single build against itself under loss to find loss-induced instability with no version variable at all.

Files

File	Purpose
build-images.sh	Build fips-interop:a/b/c, one Docker image per git ref.
generate-configs.sh	Generate per-node configs, the generated compose, manifests.
interop-test.sh	Test driver: bring up, converge, rekey, analyze, attribute.
interop-stress.sh	Netem stress loop: N reps, pass rate, mixed-vs-same attribution.
README.md	This document.

Generated at runtime: generated-configs/ (per-node configs + docker-compose.generated.yml + nodes.env + npubs.env), .build/, .stress-runs/. The root for these three is selected by the FIPS_INTEROP_RUNS_DIR environment variable — see Scratch directory location below.

The static docker-compose.yml is gone — the compose file is now generated per node-spec into generated-configs/docker-compose.generated.yml.

How per-node images work

build-images.sh <ref-a> <ref-b> <ref-c> (unchanged — always three refs):

1. For each ref, git worktree add --detach a temp checkout of the repo.
2. cargo build --release the four binaries (fips, fipsctl, fipstop, fips-gateway) in that worktree.
3. Copy the binaries into a build context alongside the shared testing/docker/Dockerfile (and entrypoint.sh, resolv.conf).
4. docker build it, tagging fips-interop:<slot> and labelling the image with its ref + short SHA.
5. Remove the temp worktree (done per-ref so peak disk stays at one worktree).

It also writes .build/refs.env, recording each slot's ref and SHA. The driver reads it to know which pairs are mixed-version. (If absent, it falls back to the image labels.)

How to run it

Build the images (once per ref set)

cd /dpool/src/clabs/nostr/fips
bash testing/interop/build-images.sh <ref-a> <ref-b> <ref-c>

Example: A = tip of fix/fsp-rekey-overlapping-epoch, B = maint, C = release tag v0.3.0:

bash testing/interop/build-images.sh fix/fsp-rekey-overlapping-epoch maint v0.3.0

Run a single mesh

bash testing/interop/interop-test.sh [node-spec...]

node-spec defaults to a b c (the original triangle). Examples:

bash testing/interop/interop-test.sh                # a b c   — 3-node triangle
bash testing/interop/interop-test.sh a a b c        # 4-node, one control pair
bash testing/interop/interop-test.sh a a a          # 3-node same-version flake rig

The driver regenerates configs automatically whenever the requested node-spec differs from the one on disk, so changing the spec just works. A run takes a few minutes (driven by REKEY_AFTER_SECS, default 35, times two rekey cycles).

Run the netem stress loop

FIPS_INTEROP_NETEM="delay 10ms 5ms 25% loss 2%" \
  bash testing/interop/interop-stress.sh [--reps N] [node-spec...]

• --reps N — repetitions (default 10).
• node-spec — default a a b c (the control topology).
• Reps run serially — the harness uses fixed container names and a fixed Docker network, so two reps must never overlap.
• If FIPS_INTEROP_NETEM is unset the script warns (a stress run normally wants netem) but still runs a clean baseline loop.

Each rep invokes interop-test.sh with netem set and captures its full output and exit code; a rep passes iff interop-test.sh exits 0. Artifacts land in testing/interop/.stress-runs/<UTC-timestamp>/:

• rep-NN/driver.log — full driver output for every rep.
• rep-NN/docker-<container>.log — per-container docker logs for failed reps only.
• summary.txt — the aggregate report.

The aggregate report gives reps run, passed/failed counts and an integer pass rate, then tallies — across all failed reps — connectivity failures by pair kind (mixed vs same), and a verdict:

• mixed pairs only, never the control pair → interop-regression signal;
• both mixed and same pairs → loss-induced general instability;
• same-version control pair only → the build is unstable against itself.

interop-stress.sh exits non-zero only for the interop-regression signal. A sub-100% pass rate under loss is expected and is not by itself a failure, so every other outcome exits 0.

Options

Variable	Effect
FIPS_INTEROP_NETEM	tc-netem string applied to each container's eth0, e.g. "delay 10ms 5ms 25% loss 1%". Passed through interop-stress.sh to interop-test.sh.
REKEY_AFTER_SECS	Rekey interval for generated configs (default 35).
FIPS_INTEROP_KEEP_UP	1 = leave containers running after the test.
FIPS_INTEROP_KEEP_WORKTREES	1 = keep build-images.sh worktrees (debug).
FIPS_INTEROP_RUNS_DIR	Root for the three scratch dirs — see Scratch directory location.

The netem hook reuses the flake-lab mechanism (docker exec ... tc qdisc on each container's eth0) — host-side bridge qdisc does not shape inter-container port-to-port traffic, so the impairment must live inside the containers.

Scratch directory location

The three scratch dirs the harness writes — .build/ (per-ref build contexts and refs.env), generated-configs/ (per-node configs + generated compose + manifests), and .stress-runs/ (stress-loop artefacts) — are rooted under FIPS_INTEROP_RUNS_DIR when that environment variable is set. With

export FIPS_INTEROP_RUNS_DIR=/var/lib/fips-interop

all three land under /var/lib/fips-interop/, and the source tree stays clean.

When FIPS_INTEROP_RUNS_DIR is unset, each harness script falls back to writing under testing/interop/ itself and prints a one-line stderr warning naming the variable. The in-tree paths are .gitignored, so accidentally running without the variable does not dirty the checkout — but pointing the variable outside the source tree is recommended, so lab runs do not interleave with the source working copy at all.

How to read the output

The driver runs six phases:

Phase	Check
0	Bring up the mesh (+ optional netem).
1	All nodes reach N-1 authenticated peers; all directed pairs ping over fips0 (the definitive FSP-session check).
2	First FMP rekey cutover completes within the timeout.
3	All pairs still ping after the first rekey.
4	Wait out a second rekey cycle.
5	All pairs still ping after the second rekey.
6	Per-node / per-pair interop log analysis.

Phase 6 is the interop-specific part. It reports:

• Global health — panics, ERROR lines, unknown FMP version drops, link teardowns, decrypt failures, handshake failures, rekey-msg2 failures. Any non-zero count is broken down per node, attributed to a specific build.
• Rekey machinery exercised — both FMP and FSP rekey cutovers fired.
• Per-pair interop summary — each unordered pair, classified same-version vs MIXED, with whether it stayed healthy through the run.

The final verdict lists every failure attributed to a specific x[ref@sha] <-> y[ref@sha] pair or build, then states the attribution:

• mixed-version only → a genuine interop regression.
• both mixed and same → general instability, not version-specific.
• same-version only → a build is unstable even against itself.

Exit code is 0 only if every check passed and no per-pair failure was recorded; non-zero otherwise, with a diagnostic dump (peer/link snapshots and interop-relevant log tails for all nodes).

CI integration

The harness is self-contained and slots into .github/workflows/ci.yml alongside the existing integration matrix suites. A future matrix entry would, per push to a PR branch:

1. Resolve the three refs — e.g. A = github.sha, B = git rev-parse github.sha^, C = $(git describe --tags --abbrev=0) or a pinned release tag.
2. bash testing/interop/build-images.sh "$A" "$B" "$C".
3. bash testing/interop/interop-test.sh a a b c for the control topology, or interop-stress.sh for a loss sweep.
4. On failure, upload the diagnostic dump (or .stress-runs/) as an artifact.

The three cargo build --release passes are the cost driver; on a CI runner this suite is heavier than the single-image suites. Reasonable options are to run it only on release branches / tags, gate it behind a label, or cache the fips-interop:c (release) image since the release tag rarely moves.

Until then the harness runs on demand locally — the same way the flake-lab is used today.