jarl/docs/views.md

# Split DNS with views

Views let named answer differently depending on who asks. The usual setup
for a homelab that is also authoritative on the internet has two views:

* **internal**: your networks get recursion (they use the server as their
  resolver) and see private addresses (`nas.adbraun.lol → 10.10.0.20`) and
  internal-only zones such as reverse zones for private networks.
* **external**: everyone else gets authoritative answers only. That means
  public addresses, no recursion, and no internal zones.

## How named treats views (and why Jarl asks to move your zones)

Without any `view` statements, named puts every zone into an implicit
default view. That's why an imported server shows no views. **As soon as
one view exists, named requires every zone to be inside a view.** So the
first view you create has to take over the existing zones, including the
root hints zone `.` that Debian/Ubuntu configure.

Jarl does this in the same changeset that creates the view:

* web UI: Views → New view. The box "Move the N zone(s) that are not in a
  view into this view" is ticked by default.
* CLI: `jarl view create NAME --adopt-zones`
* API: `"adopt_zones": true`

Creating the first view without it is refused before anything reaches
named (`zone_outside_view`).

Views are matched in order: the first view whose `match-clients` (and
`match-destinations`) fit the client wins. Put the specific view first and
the catch-all last.

## Step by step

### 1. Check the ACL for your networks

The internal view matches your networks. Usually that's the ACL you already
use for `allow-recursion`:

```sh
jarl acl list
jarl acl update homelab --add localhost      # if missing; see the note below
```

Include **localhost** if the DNS server itself uses `127.0.0.1` as its
resolver. Otherwise the server's own lookups land in the external view and
get no recursion.

### 2. Create the internal view and move the existing zones into it

```sh
jarl view create internal --match-clients homelab --adopt-zones --dry-run   # look first
jarl view create internal --match-clients homelab --adopt-zones
```

```
create view internal
move zone . into view internal
move zone 0.10.10.in-addr.arpa into view internal
move zone adbraun.lol into view internal
applied (changeset 4)
```

Nothing changes for your clients: they match `internal` and get the same
answers as before. The server-wide options (`recursion`, `allow-recursion`,
`forwarders`, ...) still apply, because views inherit them.

### 3. Create the external view

```sh
jarl view create external --match-clients any
jarl option set recursion no --view external
jarl option set allow-recursion '{ none; }' --view external
```

The inherited `allow-recursion { homelab; }` already keeps outsiders from
recursing. The explicit `recursion no` also stops them reading the cache,
and makes the intent obvious. Setting `allow-recursion { none; }` as well
avoids named-checkconf's warning that `allow-recursion` is still active in a
view with recursion off. Jarl warns (`security_open_resolver`) if a view
ever offers recursion to everyone.

Jarl counts the external view as reachable from the internet (its
match-clients end in `any`) and checks it: rate limiting, ANY queries,
the version string and more. See the **Exposure** page or `jarl exposure`,
and [exposure.md](exposure.md) to set up response rate limiting.

### 4. Give the external view its zones

**Different data per view (split DNS).** Copy the zone, then change what
should differ:

```sh
jarl zone create adbraun.lol --view external --clone-from adbraun.lol --clone-view internal
jarl record list adbraun.lol --view external
jarl record update <id> --data 203.0.113.20          # public address instead of 10.10.0.20
jarl record delete adbraun.lol nas-internal A --view external
```

From then on the two copies are separate zones. A record added to one isn't
in the other, and the serials are separate.

**The same data in both views.** Use an `in-view` zone. The external view
then serves the internal view's zone, so there is one copy to maintain:

```sh
jarl zone create example.org --view external --type in-view --in-view internal
```

Don't do that for zones with private data. Internal-only zones (reverse
zones for 10.x / 192.168.x) simply don't get an external copy: named
answers outsiders with NXDOMAIN from its built-in empty zones.

### 5. Check from both sides

```sh
dig @ns1.adbraun.lol nas.adbraun.lol +short            # from the LAN: 10.10.0.20
dig @<public-ip> nas.adbraun.lol +short                 # from outside: 203.0.113.20
dig @<public-ip> example.com                            # from outside: status REFUSED
jarl check
```

On the server, `dig -b <source address>` picks which view you test, or,
from anywhere, sign the query with the view's key (below):

```sh
jarl view key external --named-conf > external.key
dig -k external.key @ns1.adbraun.lol nas.adbraun.lol +short   # 203.0.113.20, even from the LAN
```

## View keys

named picks a view by where a query comes from, so a query this server
sends to its own public address usually lands in the internal view: its
source is one of your own networks. That makes checks of the external view
from the server itself (such as Jarl's delegation check) see the wrong
view.

So Jarl gives every view a TSIG key, `jarl-view-NAME`, and puts it at the
front of the view's `match-clients`:

```
view "internal" {
	match-clients { !key jarl-view-external; key jarl-view-internal; homelab; };
	...
view "external" {
	match-clients { key jarl-view-external; any; };
```

A query signed with a view's key lands in that view, whatever its source;
the `!key` stops an earlier view from taking a later view's queries.
Clients don't send these keys, so for them nothing changes. Jarl signs its
own queries to this server's addresses with the key of the zone's view.
The keys live in `keys.conf` with your other keys, never in diffs or in
`jarl tsig list`; their secrets are derived from a random value in Jarl's
database (and in its backups), so they stay the same from one apply to
the next. `jarl view key VIEW`
shows one (it needs `tsig:write` and is audited). Key names starting with
`jarl-view-` are reserved, and the view keys can be used in your own
options (`allow-transfer { key jarl-view-external; }`).

## Living with views

* Commands that name a zone that exists in several views need `--view`
  (`jarl record add adbraun.lol www A ... --view external`). Jarl refuses to
  guess.
* `jarl acme` writes challenge records into **every** view that has the
  zone, so Let's Encrypt (external) and internal clients see the same
  thing. Use `--view` to limit it.
* `jarl view order internal external` changes the match order, and
  `jarl view list` shows it.
* Deleting a view is refused while it still has zones, unless you pass
  `--cascade`.
* Each view has its own page (Views → the view's name): its settings,
  options and zones.
* Give each view a colour (the view's page → Settings → Colour, or
  `jarl view color internal green`) to tell the zones of each view apart
  in the zone list. The colour only affects the web UI, so it applies at
  once, with no changeset or deploy. `jarl view color internal default`
  goes back to the link colour.
* Zone files are stored per view: `/var/lib/bind/jarl/internal/adbraun.lol.zone`,
  `/var/lib/bind/jarl/external/adbraun.lol.zone`.