The pool params (size, IP base, iface prefix, nft table) were triplicated
— hardcoded in netpool.py, scripts/firecracker-netpool.sh, and
nix/firecracker-netpool.nix — plus the IP math (3x) and the nft ruleset
(2x). Nothing enforced agreement; changing the base (ce3fad9, off CGNAT)
forced a coordinated three-file edit, and a missed one would silently
provision a range the launcher doesn't expect.
Collapse to one source of truth:
* netpool.defaults.env — a plain KEY=VALUE file (bash-sourceable,
systemd EnvironmentFile-compatible, Python- and Nix-parseable) holding
the four defaults. A BOT_BOTTLE_FC_* env var still overrides any key.
* netpool.py reads it for the Python defaults (missing file = hard
error, not confusing empty defaults).
* the shell script falls back to it (no literal `:-8` / `10.243.0.0`),
and its `up` is now non-destructive/idempotent (only creates a
missing TAP), so re-running never cuts a live VM.
* the Nix module readFile-parses it for its option defaults and
delegates bring-up to the SAME shell script (dropping its duplicate
IP math, nft ruleset, and TAP loop) — passing every value as
Environment= so the store-detached script never needs the file.
Net: defaults 3x -> 1x, nft ruleset 2x -> 1x, TAP loop 2x -> 1x. The one
remaining IP-math dup (Python launch-addressing vs bash bring-up) is
justified — different runtimes. Tests now guard the invariant (Python
reads the shared file; the script/module hold no literals) instead of
pinning duplicated strings.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WBMWTEtQdJ4W5UrWuLHCck
didericis
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