docs(adr): ADR-025 local VM integration testing

Accepted decision to implement ADR-008 Level 2/3 on ubongo via
libvirt/KVM directly: throwaway VM overlays, stdlib-only driver,
tiered cert fidelity, three safety invariants. Addresses the
2026-06-17 mesh-hardening incident's reboot-survivability gap.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/decisions/025-local-vm-integration-testing.md

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+# ADR-025 — Local VM integration testing on ubongo
+
+## Status
+
+Accepted (2026-06-18). Implements ADR-008 Level 2/3 (deferred for lack of hosts; now
+viable on ubongo). The harness code is built and lint+pytest-clean; RED/GREEN
+acceptance is pending the first live run on ubongo.
+
+## Context
+
+Molecule (ADR-008 Level 1) tests each role in a single Docker container: one
+`converge`, no real kernel netfilter, no real Docker daemon in the loop, and **no
+reboot**. That structurally cannot catch an entire class of bug — reboot-survivability,
+host-firewall × Docker interaction, and boot-ordering — which is exactly the class
+that caused the **2026-06-17 mesh-hardening incident**.
+
+During that incident, `base`'s nftables `forward { policy drop; }` killed the askari
+Docker host **on reboot**: nftables loaded its default-deny before Docker, breaking
+published-port DNAT and inter-container forwarding. Public services and the mesh went
+down. It had worked right after `make deploy`, when Docker's runtime rules still
+coexisted. `ip_nonlocal_bind` also failed to beat the sshd boot-race, leaving the mesh
+listener absent at boot. Recovery required the Hetzner console and a WAN-SSH
+break-glass. Molecule had passed.
+
+ADR-008's Level 2/3 was deferred "for lack of hosts." ubongo breaks that deferral:
+
+> verified: ubongo KVM capability · Bash (2026-06-18 session) · `/dev/kvm` present +
+> accessible (kvm group), Intel VT-x (`vmx`) enabled, 8 vCPU (i3-10100T), ~13 GiB RAM
+> free of 16, ~198 GiB disk free; libvirt/QEMU/Vagrant **not yet installed** ·
+> 2026-06-18.
+
+## Decision
+
+### 1. Virtualisation approach: libvirt/KVM directly (Approach A)
+
+A golden Debian-13 genericcloud qcow2 is cached locally on ubongo. Each run boots an
+ephemeral qcow2 **overlay** backed by it (the golden image is never mutated), seeded
+via cloud-init NoCloud, driven by a **stdlib-only** Python driver (`scripts/
+integration-vm.py`) over `virsh` / `virt-install` / `cloud-localds`. No `libvirt-
+python` dependency — the driver stays portable and the role stays lean.
+
+### 2. Fidelity envelope
+
+The bugs are **post-boot**, not in the provisioning path. A lightweight local hypervisor
+is sufficient: real OS, real kernel netfilter, real Docker daemon, real published-port
+DNAT, a **real reboot**, and the coordinator running inside the VM (so the VM forms its
+own one-node mesh, reproducing the circular bootstrap). The Proxmox provisioning chrome
+is not mirrored.
+
+### 3. Scope: one throwaway VM at a time, instantiated from real inventory
+
+The first profile is **"be askari"** — a single box running Docker host + NetBird
+coordinator + mesh peer, mirroring the host whose incident motivates this work. The
+mechanism is generic: swap the profile to "be" any inventory host. Multi-VM topologies
+are a deferred extension.
+
+### 4. Acceptance: self-validating against the real failure
+
+The harness is accepted when it can, on a local VM:
+
+1. Apply `base` (firewall on, no `docker_host` container-forward drop-in) to a Docker
+   host, reboot, and observe the **2026-06-17 breakage** (Docker forwarding dead,
+   services down). If step 1 passes, the harness is not faithful.
+2. Apply the `docker_host` container-forward fix, re-run, and **survive the reboot**.
+
+### 5. Tiered cert fidelity via a `--certs` knob
+
+DNS-01 is what makes real certs possible without public inbound (validation is
+out-of-band via a Gandi TXT record; the VM needs only outbound to ACME + Gandi, which
+the isolated NAT network provides):
+
+| Tier | Description | Default? |
+|---|---|---|
+| `internal` | Caddy `tls internal` — zero deps, instant. For incident repro and runs where certs are not under test. | Yes |
+| `le-staging` | Real DNS-01 ACME against Let's Encrypt **staging** — real caddy-gandi path, real cert files/renewal, untrusted root, effectively no rate limits. | Built in v1; use when testing the ACME/cert path. |
+| `le-prod-wildcard` | A real trusted `*.test.wingu.me` wildcard, **issued once, persisted on ubongo, reused** across runs. | On-demand only. Accepted risk recorded as R6 in `docs/security/accepted-risks.md`. |
+
+A deliberate "no-egress" failure scenario (reproducing FRICTION 2026-06-17 #4 —
+`netbird-server` FATAL-loops on GeoLite2 download when egress is lost) forces
+`internal`, since ACME requires egress.
+
+### 6. The toolchain is Ansible-managed
+
+A new non-service role (`integration_test`, `control` group) installs and enables
+libvirt + QEMU + virtinst reproducibly. The driver manages the golden image lazily on
+first run (keeping the role lean; no fiddly download/refresh logic in Ansible). The
+repo owns ubongo's state.
+
+### 7. Stubs live in an overlay file, never in the real inventory
+
+Transient inventory entries for the test VM are generated at runtime as a single-host
+file. Stubs (cert tier, in-VM coordinator endpoint, VM connection details) live in
+`tests/integration/overrides/<host>.yml` — an explicit, reviewable overlay. The real
+inventory is never touched, so `make tf-inventory` and "don't edit inventory directly"
+stay intact.
+
+## Consequences
+
+- **Reconciles ADR-015:** ubongo runs ephemeral KVM test VMs as part of its
+  local-test-runner role — it is still not a production hypervisor. A default VM
+  (~2 vCPU / 3 GiB / 20 GiB thin overlay) against ~13 GiB free is comfortable; the
+  driver enforces **one integration VM at a time** (resource guard, name-prefix
+  `boma-it-*`) and refuses to start below a free-RAM threshold.
+- **Operationalises the standing rule:** "firewall/sshd/boot changes must be tested on
+  a real VM with a real reboot before they touch a live host" (FRICTION 2026-06-17 #6)
+  becomes a concrete, runnable step documented in `docs/runbooks/integration-testing.md`.
+- **Accepted risk R6:** `le-prod-wildcard` runs pass the production Gandi PAT
+  (`vault.gandi.pat`) to an ephemeral local VM and write transient `_acme-challenge`
+  TXT records into the real `wingu.me` zone. Scope: on-demand only; `le-staging` is the
+  default. Compensating controls: ephemeral VM, isolated NAT network, TXT records
+  auto-removed by Caddy after validation.
+- **Three safety invariants** make the test tool itself safe:
+  1. The transient inventory contains only the test VM — no real host is ever in scope.
+  2. "Be askari" points NetBird at the in-VM coordinator — the VM forms its own one-node
+     mesh; it never enrols in the real mesh.
+  3. Test VMs sit on an isolated libvirt NAT network — outbound NAT for ACME/image pulls
+     only, not reachable to the LAN (`10.20.x`) or the real mesh.
+- **Diagnostics on failure** (catching a bug is the point): failure keeps the VM and
+  dumps `nft list ruleset`, `docker ps`, `ss -tlnp`, `journalctl -b`,
+  `systemd-analyze critical-chain`. `make test-integration-clean` reaps all `boma-it-*`
+  orphans. Diagnostics land in gitignored `~/integration-runs/<ts>-<host>/`.
+- **Future pinch:** concurrency with the Level-4 Chromium/Playwright stack (ADR-017)
+  competes for ubongo RAM. The resource guard is the v1 answer — one integration VM at a
+  time; don't run alongside a heavy Level-4 session. Revisit at `/capacity-review`.
+
+## Scope
+
+**In scope:** reboot-survivability, host-firewall × Docker interaction, boot-ordering,
+cert/ACME paths, mesh bootstrap on one box.
+
+**Out of scope (v1):** multi-VM mini-cluster (inter-host mesh dataplane); CI gate
+(this is an interactive, agent-driven pre-deploy check; CI stays lint + Molecule per
+ADR-008/010); the Proxmox provisioning path (the bugs live in the boot/kernel/Docker
+layer, not provisioning).
+
+## What was ruled out
+
+| Option | Reason |
+|---|---|
+| **Proxmox VE nested on ubongo** | Highest fidelity including the provisioning step, but heavy (nested virt, RAM), in tension with ADR-015, and the incident bugs do not live in provisioning. |
+| **Vagrant + vagrant-libvirt** | Mature lifecycle/snapshots, but adds the Ruby/Vagrant ecosystem + a fragile plugin; boxes drift from the real Debian cloud image; the reboot→assert sequence still needs custom logic. |
+| **terraform-provider-libvirt** | Declarative and reuses TF, but poor at the imperative apply→reboot→re-apply test sequence; adds throwaway state; blurs ADR-006's "TF owns *production* VM existence on Proxmox" boundary. |
+
+## Verified facts (ADR-014)
+
+- verified: ubongo KVM capability · Bash · `/dev/kvm` present + accessible (kvm group),
+  Intel VT-x (`vmx`) enabled, 8 vCPU (i3-10100T), ~13 GiB RAM free of 16, ~198 GiB
+  disk free · 2026-06-18.
+
+## Related
+
+- ADR-006 — Terraform owns production VM existence (boundary this ADR respects).
+- ADR-008 — Testing methodology (Levels 1–4); this ADR is the concrete build of Level 2/3.
+- ADR-015 — Control host (ubongo); this ADR reconciles "not a hypervisor" with ephemeral test VMs.
+- ADR-016 — Mesh VPN; the "be askari" profile includes the coordinator role.
+- ADR-020 — Firewall strategy; firewall × Docker interaction is what this harness tests.
+- ADR-024 — Reverse proxy (Caddy); cert tiers exercise the DNS-01 ACME path.