mesh-lab

The lab: a disposable Novox Mesh on one machine.

It ships to nobody. It runs on a workstation, raises virtual machines, puts things inside them, and throws them away.

Why it exists first

The node host takes over a machine's packages, services and network. It cannot be developed against a machine anyone needs — so the place to develop it has to exist before it does.

That makes this repository phase 0 of the migration, ahead of every tier it will later test.

Two classes of scenario

	Bootstrap	Full
Contains	virtual machines, the node host, a pinned substrate bundle	a complete mesh: forge, control plane, delivery, modules
Verdict from	what the host reports about the state it reconciled	a pipeline result ending in verify
Exercises	tiers 0 and 1	tier 2 and above, and modules
Exists to	develop the mesh	test what runs on it

The bootstrap scenario is a strict subset — same virtualisation, same networking, same lifecycle, stopping before a control plane exists. The full scenario is reached by putting more inside the machines, not by building a second thing.

Using it

mesh-lab check                       can this machine run scenarios at all
mesh-lab validate scenarios/x.yml    parse and check, raising nothing
mesh-lab raise scenarios/x.yml       materialise it, wait until the machines are USABLE
mesh-lab list                        instances currently standing
mesh-lab exec <instance> <machine> -- <cmd...>
mesh-lab snapshot <instance> <label>
mesh-lab restore <instance> <label>
mesh-lab destroy <instance>
mesh-lab diagram scenarios/x.yml     draw what the scenario asks for
mesh-lab diagram --live <instance>   draw what is actually standing

check refuses rather than warns. A machine without copy-on-write storage runs scenarios correctly and snapshots roughly 76× slower — which does not make the lab slow, it makes it unused, and a warning about that is read once and ignored forever.

If the incus socket is not reachable as your user — the group was granted to a session that already existed — set MESH_LAB_INCUS="sudo -n incus".

What a scenario declares

The underlay: what a hosting provider and a home router would provide, and nothing the mesh is responsible for.

segments:
  hosting:                          # one public network
    kind: public
    cidr: [192.0.2.0/24, "2001:db8:a::/48"]
  isp-home:                         # another, unrelated — routed to it, never bridged
    kind: public
    cidr: [198.51.100.0/24, "2001:db8:b::/48"]
  home:
    kind: private
    cidr: [192.168.1.0/24, "2001:db8:b:1::/64"]
    mtu: 1492
    gateway:
      to: isp-home
      address: [198.51.100.7]       # what the world sees this network as
      nat: [v4]                     # v4 translated, v6 routed
      forwardable: true
      mapping_ttl: 120s
machines:
  home-server:
    at: { segment: home, address: [192.168.1.135, "2001:db8:b:1::135"] }
    published: [{ port: 443, on: home }]
    inbound: allow

It declares nothing about overlay addresses, hubs, peering, names or certificates. Those are what the mesh does, and a scenario that supplied them would be certifying its own work.

Public segments must use documentation ranges (RFC 5737, RFC 3849) and the validator refuses anything else before raising. That is not pedantry: the mesh decides public-versus-private by matching the address, so a private range on a segment meant to be routable makes the mesh silently never form — no error, nothing to notice.

Reaching in

Everything goes through incus, never over IP. A scenario is a closed address space, so two instances raised from one declaration hold the same addresses and never meet — and the workstation has no route into either.

So a reachability question is asked from inside: can this machine reach that one is exec on the first, testing the second. The workstation's opinion would be a different question with a misleadingly similar answer.

What is implemented, and what is not

The declaration model is complete — it is the design's shape, and validating against it is useful before any of it can be raised. The runtime is not, and the gap is refused rather than ignored:

segments as isolated links	works
machines, multi-homed or detached	works
declared addresses, both families	works
segment MTU	works
raise · exec · snapshot · restore · destroy · list	works
gateways, NAT, masquerade	works
published: ports (DNAT through the gateway's address)	works
mapping_ttl: (conntrack timeout)	works, and verified after setting — a declared expiry that silently did not apply would be the fault this catches
forwardable: false	works — outbound only, no DNAT, unsolicited inbound dropped
policy: between segments	works, asymmetric
inbound: deny	works — host firewall, read back after applying
several public networks, routed not bridged	works — a transit router, never a shared bridge
place: [host]	works — tier 0 is placed and asked what the machine is
place: anything above tier 0	refused, by name — those tiers do not exist yet

raise refuses a scenario declaring anything in the lower half, naming every gap. It does not raise a mesh that silently lacks what it declared — that is the fault this lab exists to catch (novox/hq 04-ISSUES/003: a firewall key declared in five manifests and read by no code, so a manifest appears to restrict a port and restricts nothing).

bootstrap-single.yml places the host. The rest raise an underlay and put nothing on it, which is still correct for what they test.

Placing needs a built host binary — set MESH_LAB_HOST_BINARY to one. It is an explicit path rather than a search on purpose: the declaration design leaves where place: gets its artifacts from open, and guessing would harden into the answer by accident.

Measured on a workstation

	one machine	two machines	two machines + a router
raise, to usable	12.5 s	14.6 s	32 s
snapshot	0.14 s	0.28 s	—
restore, to usable again	10.5 s	11.6 s	—

A router adds seconds, not a boot: it is a container, because it is scenery rather than something under test (novox/hq ADR 0016).

Verified by running, not asserted — a machine at 192.168.1.135 behind a household gateway, reached from a machine on a routable address:

home-server -> anchor                        0% loss, through masquerade
anchor -> 192.168.1.135  (private, direct)   unreachable ✓
anchor -> 192.0.2.50:8080 (the GATEWAY)      HTTP 200
home -> devices  (policy allow)              reachable ✓
devices -> home  (policy deny)               blocked ✓
roamer behind unforwardable NAT -> anchor    reachable ✓  (outbound only)
anchor -> roamer                             unreachable ✓
workstation with inbound: deny, dialling out reachable ✓  (defended, not disconnected)
home-server -> workstation                   refused ✓

The third line is the case research 004 says only exists in production.

Routed, never bridged, proven rather than asserted — ping TTL across the full topology:

within one segment                           ttl=64   no hops
across two unrelated public networks         ttl=62   gateway + transit
multicast between public networks            0 replies

A flat "internet" would have shown ttl=64 and answered multicast, which would have let a node discover a peer it could never reach in production — and report success.

Machines boot concurrently, so a second machine costs seconds rather than doubling the wait. Nearly all of the remaining time is boot, which cannot be avoided.

These numbers depend entirely on a copy-on-write pool. On dir the same snapshot takes 9.9 s and a full copy of the disk, and a second one did not finish in two minutes — which is why check refuses rather than warns.

Drawing one

mesh-lab diagram scenarios/the-ordinary-shape.yml   what the declaration asks for
mesh-lab diagram --live <instance>                  what the hypervisor actually holds

Both produce draw.io files, laid out the same way — public networks at the top, each private one below the network it sits behind. Drawing both sources through one layout is the point: a difference between what was asked for and what exists becomes a difference you can see.

Two kinds of symbol, and the split matters:

• the shape says what a resource is, and is fixed per kind — a server is always the server shape, a gateway always the router shape, whatever else is true about it;
• the badges say what is true about that particular one, and come entirely from metadata: N translated, F forwarding (green yes, red no), T mappings expire, D refuses inbound, C container, VM virtual machine, ▶ running. Each carries the full sentence as a tooltip, because a one-letter code with no explanation is a private language.

Badges exist because the interesting properties of a network are exactly the ones with no visual consequence. An address that is translated looks identical to one that is not, until traffic proves otherwise.

The live drawing reads only the hypervisor — the same tags destroy uses — and never re-opens the scenario file. A picture built from the declaration and labelled as raised would report the request as though it were the result, which is the whole failure the pairing exists to expose. So raise records what it applied: a segment's kind and ranges on the link, a gateway's translation, forwardability and mapping expiry on the gateway, and inbound: deny on the machine.

Every behavioural tag is written after the thing works, never before. A tag written when the resource is created would restate the request; a failed raise leaves its wreckage standing on purpose, so a picture of that wreckage would badge translation the gateway was never configured to do. The gateway is tagged after its ruleset is applied, and the machine after the read-back proves its firewall loaded.

That pairing has already earned itself. Drawn side by side, the live picture showed every virtual machine holding no addresses at all: a container's interface carries the device's name, a virtual machine names its own, and joining them by name silently dropped one whole class of machine. The two pictures disagreed, so the bug was visible in seconds.

Where the reasoning lives

Design and decisions are in novox/hq, not here:

• 03-DESIGN/01-to-be/02-scenario-declaration.md — what a scenario declares
• 03-DESIGN/01-to-be/03-scenario-lifecycle.md — what happens to one
• 02-DECISIONS/0031-the-lab-provides-the-underlay.md
• 02-DECISIONS/0032-a-scenario-is-an-isolated-address-space.md

This repository carries implementation. It does not carry decisions.

Development

No build step — Node strips the types.

npm test                   the declaration layer and the diagram, offline, 49 tests
npm run test:integration   real scenarios against a real hypervisor, 14 tests
npm run typecheck          source and tests both — a test that does not compile is a test
                           that silently never ran
npm run check              typecheck + both suites — this is the gate

A test names the decision it defends (novox/hq ADR 0017). A decision with no test is one that will quietly stop being true, and nobody learns that from a document:

Test	Defends
the lab provides the underlay and nothing of the overlay	ADR 0016
the workstation has no route into the scenario	ADR 0016
a router is a container while machines are virtual machines	ADR 0016
raise waits for usable, not for the call to return	the lifecycle design
snapshots are whole-scenario	the lifecycle design
a public range that is not documentation space is refused	the declaration design
a scenario declaring what cannot be materialised is refused	the declaration design
the live diagram distinguishes scenery from a node	ADR 0016
the live diagram draws what exists, never what was asked for	the diagram design
a picture nobody can open is not a picture	the diagram design

Mocking the hypervisor is forbidden. A fake would assert that the fake behaves as expected, which is the shape of test this project exists to stop shipping. Integration tests skip with a reason on a machine that cannot raise scenarios, rather than passing green having checked nothing.

That suite earned itself on its first run: it found that a snapshot of a running machine could miss a file written seconds earlier — not stale, absent — because the write was still in the guest's page cache. The design had listed that as an open question. The test answered it, and snapshot now flushes first.