a21be505db3a04bd04022e725e32fd0fcbdf3e8d
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Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 jschoubben
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a6b7d67e19 |
Gateways sharing an address are one gateway
Found by asking what gw-devices and gw-home actually were, in a picture that
finally made them easy to see side by side.
planRouters grouped on the exact address list, so `home` declaring a v4 and a v6
address and `devices` declaring only the v4 became two router containers — both
holding 198.51.100.7 on the same segment. The lab raised it without complaint.
Not theoretical. On the raised instance the transit router resolved that one
address to two different MACs across a cache flush:
198.51.100.7 -> 02:c9:16:70:23:29 (gw0, which HAS the :443 dnat)
198.51.100.7 -> 02:bd:75:0b:b0:75 (gw1, which has none)
So home-server's published port worked or did not depending on which container
answered ARP last — intermittent, and it would have presented as a flaky test
rather than as a broken scenario.
One public address is one box. Checked against the thing this models rather than
argued from the model: a bridged modem, a single gateway holding the public
address, one network behind it, and every port forward landing on one host at
that address. Two routers on one address is not a topology, it is a collision.
Gateways to the same segment sharing any address are now one router and their
address lists union, so a v6 address declared on only one of the segments it
serves is still carried. Where such declarations disagree on nat, forwardable or
mapping_ttl, validate refuses — one box cannot behave two ways.
the-ordinary-shape now raises 7 machines instead of 8, and gw0 holds the public
address on eth0 while serving home on eth1 and devices on eth2.
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jschoubben
|
2243618f01 |
Draw a scenario, from the declaration and from the hypervisor
`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. |
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jschoubben
|
5d01006eab |
Transit, host firewalls, and the whole topology raising
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. |
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jschoubben
|
a270cd5b02 |
Routers: NAT, port forwarding, policy and mapping expiry
A gateway is the one implicit machine in a declaration — a scenario says a segment sits behind one and never names the thing that serves it. This materialises it. A router is a container, not a virtual machine, because it is scenery rather than something under test (hq ADR 0033). Verified before building that a plain unprivileged container can do all of it: ip_forward and ipv6 forwarding settable, nftables masquerade accepted, and the conntrack timeouts mapping_ttl depends on both writable. No privileged mode. Verified by running, on a machine behind a household gateway reached from one 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 The last line is the published-but-behind-NAT case research 004 says only exists in production. It is now a 32-second scenario on a workstation. Segments sharing a gateway declaration share ONE router — that is what a VLAN-capable router is, and two routers sharing an external address would not work anyway. mapping_ttl is read back after setting rather than assumed. Those sysctls are not on every kernel, and a scenario that declared an expiring mapping and silently got a permanent one would be exactly the fault being built against. Four bugs found by running it, three of them the same fault — a failure made invisible. The router had no route to a package repository, by design, so installing nftables at raise time could not work. The image is now built once with temporary connectivity and cached; every scenario after that needs no network. That failure was hidden behind `|| true`, which is why it took a raise to find. The builder then failed on DNS: exec works before a container has an address, and I had treated usable as ready. It now waits for the thing actually needed. The stock Alpine image ships `auto eth0 / inet dhcp` and its boot-time networking service flushed the static address the scenario set — on eth0 only, so the outside interface came up bare while inside ones were fine. The image build now neutralises it: a router reconfiguring itself from an image default is the lab overriding the declaration. `ip addr add … || true` had hidden this too, and is now `ip addr replace` with no swallow. And routers were orphaned by destroy, holding their networks open so destroy reported removing zero segments. They now carry the same machine tag as everything else, so one query finds an instance's resources. |