# Running Housecarl ## The services ```sh systemctl status housecarl # housecarld: the API, the web UI, the log journalctl -u housecarl -f systemctl reload housecarl # reread the TLS certificate systemctl status housecarl-ruleset # the ruleset loaded at boot ``` The firewall itself is the kernel's: it stays in force while housecarld is stopped, restarted or upgraded. Without housecarld there is no API, no web UI, no log and no probation timer. housecarld logs each change it applies, rollbacks, and what it couldn't apply. When it starts, it applies the configuration again (rolling back first what was on probation when it stopped). ## Reviewing before applying In the web UI, edits are collected as pending changes (the bar under the header), and Changes shows them with the diff of the ruleset; Apply puts them in force together. The switch in the header (Review edits / Live edits) applies each edit at once instead. With hc, see [cli.md](cli.md#changesets). ## Changes on probation Changes made over the network roll back unless confirmed ([design.md](design.md#not-locking-yourself-out)); in shadow mode, where a change can't cut anyone off, none do ([shadow.md](shadow.md)). The web UI and `hc` confirm their own changes once they reach Housecarl again over a new connection, so normally nothing waits: ``` $ hc rule add input --from admins --service ssh created rule input #31 applied and confirmed (history 12): this client reached Housecarl again over a new connection ``` A change that cuts the client off can't be confirmed that way: ``` applied on probation (history 13), but couldn't confirm it: … context deadline exceeded It is rolled back within 1m50s unless confirmed ('hc confirm') ``` By hand (with `--no-confirm`, or with Settings → "a person confirms each change"): ```sh hc status # Probation: 2 changes roll back in 97s unless confirmed hc confirm hc rollback # or undo them now ``` The web UI shows a banner with a countdown and both buttons. A rollback is in the history, as an undo by `housecarl` via `rollback`, so it can be undone like any change. If you are cut off by a change: wait. When the time is up, the previous ruleset comes back by itself. If you are cut off by a confirmed change, use the console, or SSH from a source the rules still let in: ```sh sudo hc history list sudo hc history undo 42 ``` ## The ruleset at boot A confirmed ruleset (or one changed through the socket) is saved to `/var/lib/housecarl/ruleset.nft`, which `housecarl-ruleset.service` loads before the network comes up, so before PPPoE, WireGuard or DHCP bring up their interfaces. To see what would load: ```sh sudo cat /var/lib/housecarl/ruleset.nft sudo nft -c -f /var/lib/housecarl/ruleset.nft # check it ``` In shadow mode both files are shadow mode's, and the fallback filters nothing ([shadow.md](shadow.md#what-works-differently)). Dynamic sets start empty after a reboot. Sets from Jarl have the addresses they last had, in the saved ruleset and again when housecarld starts, whether Jarl is reachable yet or not ([jarl.md](jarl.md#when-jarl-cant-be-reached)). The saved ruleset has no flowtable, since its devices may not exist yet: housecarld adds it when it starts, and whenever a flowtable device appears ([flowtable.md](flowtable.md#devices-that-come-and-go)). ### If the ruleset fails to load at boot Should `ruleset.nft` fail to load (a damaged file, an nftables or kernel upgrade that refuses something in it), the machine would otherwise boot with no firewall at all until housecarld starts. Instead, `housecarl-ruleset.service` loads a **fallback** that housecarld saves beside it, `/var/lib/housecarl/ruleset-fallback.nft`, from the same confirmed configuration: * **Nothing new gets in from the external zones' interfaces**, to the firewall or through it: no port forwards, no SSH or web UI from the internet. * What the firewall and the inside need to keep working is let in: established connections, the ICMPv6 IPv6 needs (neighbour discovery, router advertisements, packet too big), and DHCPv6 replies from link-local addresses. * **Everything else is let through**: the LAN, WireGuard and the firewall itself are reachable from the inside, so you can log in and fix it. * IPv4 leaving an external zone is masqueraded (when any source NAT is configured), so the inside still reaches the internet. MSS clamping stays, if it is on. PPPoE itself isn't affected: its discovery and session are Ethernet frames, and the PPP link's negotiation happens before any IP, neither of which an `inet` table sees. The fallback only knows which interfaces face the internet from the zones marked **external**. With none, it lets nothing but loopback through, and the warning `no_external_zone` says so. When the fallback loads, the unit is marked failed, and the journal says why (as a critical message): ```sh systemctl status housecarl-ruleset journalctl -b -u housecarl-ruleset ``` housecarld puts the real ruleset back when it starts, and saves a fresh `ruleset.nft`. If it can't apply it either, the fallback stays in force: `hc status` and the dashboard say "NOT in force: the boot fallback is in force", and `/healthz` answers 503 ([Monitoring](#monitoring)). Fix what `hc status` or the journal reports, then restart housecarld. Keep Debian's `nftables.service` disabled (`systemctl disable nftables`, without `--now`): at boot it loads `/etc/nftables.conf`, and stopping or restarting it runs `nft flush ruleset`, which deletes every table, Housecarl's included. `housecarl-ruleset.service` runs after it at boot, which covers the ordinary case, but not a restart of `nftables.service` later. Housecarl never reads or writes `/etc/nftables.conf`; its ruleset is saved in `/var/lib/housecarl/ruleset.nft`. The dashboard and `hc status` warn while `nftables.service` is enabled. Other programs' tables are left alone: fail2ban's (`inet f2b-table`), Docker's, Incus's. Housecarl replaces only its own table, so they keep their rules through every Housecarl change and restart, and nothing needs restarting in a particular order. A packet must get past every table on its hook, so a drop in any of them wins. ## Hits Every rule, NAT rule, built-in and policy has a counter. `hc rule list`, `hc forward list` and the web UI show packets; `hc counters` shows them all, with bytes. They count from housecarld's start, and carry across changes to the ruleset. A deleted object's counter goes with it; an import with `--replace` gives every object a new ID, so its counters start again. A disabled rule keeps its count for when it is enabled. ## Quotas `hc quotas` (and the rules page) show what each quota used and when it resets; `hc rule reset-quota ID` starts one again (`--address` one device's, `--give 5gbytes` a top-up until the next reset). housecarld resets quotas at midnight when their period ends (late, if it was stopped then), and saves their usage every five minutes, after every change and when it stops; after a reboot it puts it back. A reboot without a clean stop loses at most the last five minutes' count. ## The log Rules with `--log` (Log in the web UI) and, with `hc settings set --log-drops on`, what the input and forward policies drop (at most 10 packets a second) are logged: ```sh hc log -f hc log --search 198.51.100.7 ``` ``` 10:02:13 hc input #95 drop: wan - 198.51.100.7:53868 -> 203.0.113.10:22 tcp syn 10:02:15 hc forward policy drop: wan eth1 198.51.100.9:443 -> 192.168.1.20:51432 tcp ``` In shadow mode ([shadow.md](shadow.md)) what the policies would drop is always logged, in all three chains, and drops are marked as what would have been done: the packets went on. The packets go to netlink log group 4171, where housecarld reads them; the last 2000 are kept in memory. They aren't written to the kernel log or the journal. A rule's log isn't rate-limited: on a busy rule, give it a limit, or log only new connections (`--state new`). ## Connections The built-in that accepts established connections lets their packets through without checking the rules again: a rule added later doesn't stop a connection already open. Traffic → Connections (`hc connections`) lists what the kernel tracks, with NAT (`to 192.168.1.10:443`: a port forward; `as 203.0.113.10`: masqueraded) and the time left: ```sh hc connections --search 192.168.1.50 hc connections --search ":443 tcp" hc connections close --search 192.168.1.50 ``` Closing a connection deletes its tracking entry: its next packet is checked by the rules as they are now. One they block is stopped; one they allow carries on (TCP connections are picked up again mid-stream). To make a block stop open connections by itself, tick "every packet" on the rule (`--every-packet`): it is checked before established connections are accepted, like rules with a quota ([rules.md](rules.md#rules)). ## Tracing Traffic → Trace (`hc trace`) follows packets through the whole ruleset: Housecarl's rules and every other table (Docker's, fail2ban's, an old `inet main`), each rule and policy they meet, and what accepted or dropped them: ``` $ hc trace --address 192.168.1.50 --port 443 --seconds 60 14:02:13.120 192.168.1.50:51432 -> 198.51.100.9:443 tcp syn in eth1 out wan inet housecarl forward: built-in: mss-clamp -> continue inet housecarl forward: rule forward #12 (kids at night) -> drop => DROPPED by rule forward #12 (kids at night) ``` It traces packets from or to the address, on the port (either way), for 5 to 600 seconds, at most 200 packets and 20 a second. It works with nftables' own tracing: a table of its own (`inet housecarl-trace`, hooked before everything else) marks the packets, and `nft monitor trace` reports them; the table goes when the trace ends. One trace runs at a time. ## When something doesn't get through 1. Trace it (above): it names the rule or policy that dropped it, in whichever table. 2. `hc log -f` with `--log-drops on`: is it dropped by a policy (no rule accepted it), or by a rule (its number is in the line)? 3. `hc rule list forward` (or `input`): hits on the rule you expect? 4. `hc ruleset`: the rule as nftables sees it, with the zones' interfaces and the sets' families. 5. `hc status`: other tables. A Docker or Incus table, or an old one, can drop what Housecarl accepts. 6. Port forwards: `hc forward list` hits, and the inside host's own firewall and default route (answers must go back through Housecarl). ## Backups `housecarl-backup.timer` runs `housecarld backup` daily. It writes a consistent copy of the database to `backup.dir` (`/var/backups/housecarl/housecarl-