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fix(local): handle names under .localhost. (#8151)

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This commit is contained in:
Immanuel Tikhonov
2026-06-24 13:31:31 +04:00
committed by GitHub
parent faeb8ba699
commit e45ad5f87a
7 changed files with 211 additions and 38 deletions
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33
plugin/local/README.md
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@@ -6,16 +6,18 @@
## Description
*local* will respond with a basic reply to a "local request". Local request are defined to be
names in the following zones: localhost, 0.in-addr.arpa, 127.in-addr.arpa and 255.in-addr.arpa *and*
any query asking for `localhost.<domain>`. When seeing the latter a metric counter is increased and
if *debug* is enabled a debug log is emitted.
*local* will respond with a basic reply to a "local request". Local requests are defined to be
names in the following zones: localhost, 0.in-addr.arpa, 127.in-addr.arpa and 255.in-addr.arpa,
any query under `.localhost.`, and, by default for backward compatibility, any query prefixed by
`localhost.`. When seeing one of the non-apex localhost forms a metric counter is increased and if
*debug* is enabled a debug log is emitted.
With *local* enabled any query falling under these zones will get a reply. The prevents the query
With *local* enabled any query falling under these zones will get a reply. This prevents the query
from "escaping" to the internet and putting strain on external infrastructure.
The zones are mostly empty, only `localhost.` address records (A and AAAA) are defined and a
`1.0.0.127.in-addr.arpa.` reverse (PTR) record.
The zones are mostly empty, only `localhost.`, names under `.localhost.`, and legacy
`localhost.<domain>` names return loopback address records (A and AAAA), and only
`1.0.0.127.in-addr.arpa.` has a reverse (PTR) record.
## Syntax
@@ -23,12 +25,25 @@ The zones are mostly empty, only `localhost.` address records (A and AAAA) are d
local
~~~
~~~ txt
local {
localhost_prefix on|off
}
~~~
`localhost_prefix` controls the legacy `localhost.<domain>` behavior. The default is `on` for
backward compatibility. Set it to `off` to only treat names under `.localhost.` as special, which
matches RFC 6761. The legacy prefix behavior is deprecated and may be disabled by default in a
future release.
## Metrics
If monitoring is enabled (via the *prometheus* plugin) then the following metric is exported:
* `coredns_local_localhost_requests_total{}` - a counter of the number of `localhost.<domain>`
requests CoreDNS has seen. Note this does *not* count `localhost.` queries.
* `coredns_local_localhost_requests_total{}` - a counter of the number of non-apex localhost
special-case queries CoreDNS has seen. This includes `.localhost.` names and, when
`localhost_prefix` is `on`, legacy `localhost.<domain>` names. It does *not* count `localhost.`
queries.
Note that this metric *does not* have a `server` label, because it's more interesting to find the
client(s) performing these queries than to see which server handled it. You'll need to inspect the