shadow.enabled in housecarl.yaml loads Housecarl's ruleset so that it
blocks, rejects and translates nothing: drops and rejects count and
accept (an accept only ends Housecarl's chain), policies accept and log
what they would drop, NAT only counts, MSS clamping and the flowtable
are left out, and raw rules that do more than accept, drop or reject are
left out with a warning. Comments mark what would happen ([would drop]).
Filter chains run after the other firewall's (+10) or before (-10); NAT
chains always first. Every change is checked by nftables in both forms.
No probation; takeovers and closing connections are refused. The boot
fallback filters nothing. internal/tablewatch puts the table back after
a flush ruleset. Mode in status, healthz, whoami, the web UI, the log
and the tracer; hc ruleset --enforcing. docs/shadow.md.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
- Connections: the kernel's tracked connections, read and closed over
ctnetlink (internal/conntrack, raw netlink like the drop log), with
their NAT and TCP state; closing one makes the rules check its next
packet again (GET /connections, POST /connections/close; hc
connections; Traffic → Connections).
- Rules can check every packet (every_packet, --every-packet): before
established connections are accepted, so a drop or reject also stops
connections already open. They can't accept.
- A packet tracer (internal/trace): a table of its own, inet
housecarl-trace, marks the packets a filter picks, `nft monitor trace`
reports every rule and policy they meet in every table, and the tracer
names what accepted or dropped them, Housecarl's rules by name (POST,
GET, DELETE /trace; hc trace; Traffic → Trace). One trace at a time,
at most 200 packets and 20 a second; the table goes when it ends.
e2e: 157 checks, among them an upload a normal block doesn't stop and an
every-packet one does, and a trace naming the blocking rule.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
abrown38andClaude Opus 5.5