dnswatcher/TODO.md

# Workflow

* branch (from `main`)
* do the work in Next Step
* move Next Step to the top of Completed Steps
* move the top item of Future Steps into Next Step
* commit (`TODO.md` changes in the same commit as the work)
* merge to `main` if the branch is not protected, otherwise open a PR
* push

# Status

pre-1.0. No git tags. Core resolver work in flight on feature/resolver
(dirty: internal/resolver/resolver_test.go). Local checkout has diverged
from origin: origin/main is 8 commits ahead (watcher orchestrator,
unified TARGETS) and origin/feature/resolver already contains the full
iterative resolver implementation with hermetic mocked tests.

# Next Step

Policy scaffold commit: add LICENSE, REPO_POLICIES.md, .editorconfig,
.dockerignore, and .gitea/workflows/check.yml, and add the missing
fmt-check, docker, and hooks targets to the Makefile. One commit, then
confirm make check still passes.

# Completed Steps

- 2026-08-07: golangci-lint bumped to v2.12.2 (commit-pinned installs
  in `Dockerfile` and `script/bootstrap`); `.golangci.yml` set to the
  org-standard v2-schema config used across the org's repos
  (owner-authorized; same file is being landed as canonical via prompts
  PR #24), with settings under `linters.settings` so the
  lll/funlen/cyclop/dupl thresholds apply; fixed the resulting
  `goconst`, `dupl`, and `lll` findings; the informational `gomodguard`
  deprecation warning under this config is accepted
- 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints,
  Makefile shims, README Entrypoints section
- 2026-02-20: iterative DNS resolver implemented; tests made hermetic
  with mocked DNS (origin/feature/resolver, unmerged)
- 2026-02-20: CI actions and go install refs pinned to commit SHAs;
  Gitea Actions workflow for make check (origin/ci/make-check, unmerged)
- 2026-02-20: watcher monitoring orchestrator merged to main (#8)
- 2026-02-20: DOMAINS/HOSTNAMES unified into single TARGETS config (#11)
- 2026-02-19: TCP port connectivity checker, made concurrent with port
  validation; gosec G704 SSRF findings fixed without suppression
  (feature branches, unmerged)
- 2026-02-19: TLS certificate inspector with no-peer-certificates error
  path and IP SANs (feature branch, unmerged)
- 2026-02-19: gosec SSRF and formatting fixes on main
- 2026-02-19: initial scaffold with per-nameserver DNS monitoring model

# Future Steps

Compliance:

- Add README sections required by policy (Description, Getting Started,
  Rationale, Design, TODO, License, Author) if any are missing
- Pin Dockerfile base images by sha256 and ensure the Docker build runs
  make check

Branch reconciliation:

- Sync local checkout with origin: local main is 8 commits behind
  origin/main; local feature/resolver has diverged from
  origin/feature/resolver, which already implements the resolver
- Merge in-flight branches to main once green: feature/resolver,
  ci/make-check, feature/portcheck-implementation,
  feature/tlscheck-implementation

Resolver (plan from untracked TODO.md; largely implemented on
origin/feature/resolver, verify each item before closing):

- Add github.com/miekg/dns dependency
- roots.go: hardcoded IANA root server list (a through m, IPv4/IPv6),
  rootServers() returning ip:53 strings
- query.go: low-level query(ctx, server, name, qtype): UDP with TCP
  fallback on truncation, RD=0, context respected, 5s per-query timeout,
  returns raw *dns.Msg
- trace.go: iterative delegation chasing from roots: referral detection
  (NOERROR, empty answer, NS in authority), glue extraction with
  bailiwick check, out-of-bailiwick NS resolved with recursion guard,
  delegation depth limit (20), retry across nameservers on failure, do
  not chase CNAMEs inside trace
- FindAuthoritativeNameservers: NS set via trace, sorted, FQDN
  normalized, trailing dot handled; must pass its 9 tests
- QueryNameserver: resolve NS host to IPs, query A/AAAA/CNAME/MX/TXT/
  SRV/CAA/NS, build NameserverResponse with status mapping (OK,
  NXDomain, NoData, Error), documented record formatting, sorted values,
  lame delegation detection; must pass its 16 tests
- QueryAllNameservers: find NS set for parent domain (public suffix
  list), query all NS in parallel with bounded concurrency, return map
  even when all fail, context cancellation; must pass its 4 tests
- LookupNS: thin wrapper over FindAuthoritativeNameservers, sorted,
  identical results; must pass its 3 tests
- ResolveIPAddresses: collect A/AAAA from all NS, follow CNAME chains
  with MaxCNAMEDepth, dedupe, sort, NXDOMAIN returns empty slice with
  nil error; must pass its 9 tests
- All 39 resolver tests pass, make check green, merge to main

Watcher (internal/watcher/watcher.go):

- Scheduling loop in Run(ctx): initial check on startup, separate
  tickers for DNS/port and TLS intervals, persist state via state.Save()
  after each cycle, clean shutdown on context cancel
- Domain check: LookupNS, compare to stored state, store silently on
  first run, notify with old/new NS lists on change
- Hostname check: QueryAllNameservers, compare per-NS records; notify on
  record changes, NS failure, NS recovery, inconsistency detected,
  inconsistency resolved, empty response; store silently on first run
- Port check: ResolveIPAddresses, check ports 80 and 443 per IP, notify
  on open/closed transitions, handle new and disappeared IPs
- TLS check: for each open IP:443, CheckCertificate; notify on expiry
  warning, certificate change (CN/issuer/SANs), TLS failure/recovery

Port checker (internal/portcheck/portcheck.go):

- Tests against known-open ports and RFC documentation IPs
- CheckPort: net.DialTimeout (5s), context respected; (true, nil) open,
  (false, nil) closed/timeout/refused, error only for unexpected
  failures

TLS checker (internal/tlscheck/tlscheck.go):

- Tests against known public HTTPS servers, verify fields populated
- CheckCertificate: tls.Dial to specific IP:443 with hostname as SNI;
  extract subject CN, issuer CN and org, NotAfter, SANs; error on
  handshake failure

Notification service (internal/notify/notify.go, Slack/Mattermost/ntfy
backends exist):

- Structured notification types: DNS change, port change, TLS expiry,
  TLS change, NS failure, NS recovery, NS inconsistency
- Per-backend formatting: Slack/Mattermost attachment colors (red
  failures/expiry, yellow warnings, green recoveries, blue info); ntfy
  priorities (urgent failures, high warnings, default changes, low
  recoveries); include hostname, nameserver, old/new values, timestamps

HTTP API handlers:

- Wire *state.State and *watcher.Watcher into handler params
- GET /api/v1/status: full state snapshot as JSON
- GET /api/v1/domains: domain states with NS records and last-checked
- GET /api/v1/hostnames: hostname states with per-NS record data

Infrastructure notes (from untracked TODO.md):

- Module path sneak.berlin/go/dnswatcher differs from the git.eeqj.de
  remote intentionally; do not "fix" it
- Dependencies: github.com/miekg/dns, golang.org/x/net/publicsuffix
- Resolver tests originally used live DNS against *.dns.sneak.cloud
  (required records documented in the test file header); origin now has
  mocked hermetic tests, keep them hermetic