`mesh-lab diagram` renders a scenario as draw.io, from either source, through
one layout — so a difference between what was asked for and what exists is a
difference you can see.
The shape says what a resource is and is fixed per kind. The badges say what is
true about that particular one and come entirely from metadata: translation,
forwardability, mapping expiry, refuses-inbound, container-or-VM, running. The
interesting properties of a network are exactly the ones with no visual
consequence — a translated address looks identical to an untranslated one.
For the live picture to be a record rather than a restatement, raise now writes
down what it applied: a segment's kind, ranges and MTU on the link; a gateway's
translation, forwardability and expiry on the gateway; inbound: deny on the
machine. Every behavioural tag is written AFTER the thing works, never at
creation — a failed raise leaves wreckage standing on purpose, and a picture of
that wreckage must not badge translation the router never got.
The pairing earned itself immediately: drawn side by side, every virtual machine
held no addresses. A container's interface carries the device's name and a VM
names its own, so joining them by name silently dropped one whole class of
machine. Fixed by joining on MAC.
Also brings tests under the typecheck gate, which caught integration timeouts
being passed as a 4th argument and therefore ignored entirely.
The full topology now raises: four machines, three routers, a transit
router, six segments, in 35 seconds. Everything the declaration model can
express except `place`, which is refused because the node host it would
place does not exist yet.
Transit was a real gap, not a bug. The design says public networks are
unrelated and routed to each other, never bridged — and I built the
segments and never built the thing that routes between them, so three
public networks were islands and nothing crossed. A transit router now
holds an interface on every public segment, forwarding and no translation:
the closest thing the lab has to the internet, deliberately dumb.
Proven rather than asserted, by ping TTL across the raised 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 let a node discover a peer it could never reach in production, and
report success. That is the fault the as-is layer records the mesh already
hitting with multicast name resolution.
inbound: deny is implemented as a host firewall on the machine, read back
after applying. A declared refusal that silently did not load leaves the
machine wide open, which looks exactly like a machine that is working.
Established and related traffic is accepted, so a defended machine can
still dial out rather than being a disconnected one.
Verified by running, all of it:
home -> devices (policy allow) reachable
devices -> home (policy deny) blocked
behind unforwardable NAT -> out reachable
in -> behind unforwardable NAT unreachable
inbound: deny, dialling out reachable
reaching a machine that denies inbound refused
The two routers differ exactly as declared: the forwardable one carries the
policy rule and no inbound drop, the unforwardable one carries `ct state
new drop` and no DNAT.
jschoubben