jschoubben
274bd3b304
Address family was not a field. IPv6 usually has no NAT, so a machine behind a household gateway is typically unforwardable on v4 and DIRECTLY ATTACHED on v6, at the same moment. The three positions therefore apply per family, and reachability is a property of (machine, family) rather than of a machine. The consequence is bigger than the syntax: 'can these two nodes reach each other' stops being a yes/no question. It is asked once per family, and the asymmetric answers are the interesting ones. A mesh treating reachability as one fact per node reaches a peer over one family, fails over the other, and reports whichever it tried. That distinction did not exist in the model and would have been found by a failure rather than by reading. Two fields follow from it. inbound: allow|deny became necessary because with NAT unreachability was implied by topology, while a globally routable v6 address is reachable unless something refuses — so refusing has to be sayable or v6 addressing silently implies reachability. And nat: became a list of families rather than a boolean, because a real gateway translates v4 and routes v6 and a boolean cannot say that. mapping_ttl closes the keepalive gap: a mesh holding a connection through NAT without refreshing it works perfectly until the far side goes quiet for longer than the mapping lives. segments[].mtu closes the fragmentation gap: an overlay adds a header, so a tunnel over a reduced-MTU path establishes a connection and then silently drops large packets. at: takes a list, so a multi-homed machine is expressible — which the model already implicitly required, since a border machine sits on two segments. v6 uses RFC 3849 documentation space, the exact counterpart of the RFC 5737 rule and load-bearing for the same reason. Remaining: nested forwarding and an address changing in place, both extensible when needed. Path quality stays deliberately out — it changes performance, not correctness, and modelling it makes a network simulator rather than a fixture.
03-DESIGN
The authoritative specification. Implementation is built against what is written here.
Two layers
| Folder | What it is |
|---|---|
00-as-is/ |
The mesh that exists today. Shipped behaviour, described as it is — including behaviour nobody would choose again. |
01-to-be/ |
The mesh being built toward. Every statement traceable to a record in 02-DECISIONS/. |
They are never mixed. A statement about the future does not belong in an as-is document, and an as-is document is never edited to describe an intention.
When a to-be design ships, it does not move. Its as-is counterpart is written or updated,
the to-be document's status becomes implemented, and both stand — one describing what runs,
the other recording what was intended. Deleting the intention loses the reasoning, which is
the expensive half.
Frontmatter
Every design document (not the READMEs) carries:
---
layer: as-is | to-be
status: designed | in-progress | implemented | abandoned
code: [] # owning code repo(s), from 00-META/repos.md
updated: YYYY-MM-DD # date of the last status change, not of text edits
decisions: [] # 02-DECISIONS/ records this document rests on
---
For an as-is document, status: implemented is the normal state — it describes something that
runs — and code: names where that implementation lives.
Status changes when implementation state changes, never because design text was edited. An
implemented claim must be defensible from the owning repository's main branch, not from
intent. If it cannot be checked, it is in-progress.
Cross-cutting views are generated from this frontmatter by the hq-status skill and never
written to disk.
What belongs here
Functional analysis, architectural description, and specification — prose and diagrams
only, no code. A manifest field may be named; a manifest may not be pasted. A document
enters the to-be layer only after the decision behind it is recorded in 02-DECISIONS/
and the research that produced it is closed.
Subfolders are encouraged where a layer grows enough to need them.