DNS Rewrite intermittent SERVFAIL, caching issue

[tescophil]

Prerequisites

• I have checked the Wiki and Discussions and found no answer

• I have searched other issues and found no duplicates

• I want to report a bug and not ask a question or ask for help

• I have set up AdGuard Home correctly and configured clients to use it. (Use the Discussions for help with installing and configuring clients.)

Platform (OS and CPU architecture)

Linux, AMD64 (aka x86_64)

Installation

GitHub releases or script from README

Setup

On one machine

AdGuard Home version

v0.107.59

Action

DNS rewrites result in intermittent SERVFAIL return code due to multiple entries in cache (looks like ?) for the same domain.

Expected result

I expect to see one cached entry for each domain, this looks like they're are multiple entries. Also if a query returns SERVFAIL then DON'T cache it as it may be a temporary failure which is then persisted in the cache.

Actual result

Query returns with SERVFAIL

Additional information and/or screenshots

Here are two queries a couple of milliseconds apart, cached responses from different servers (which I don't understand) one responds SERVFAIL and the other NOERROR

Time
07:40:45.441
Date
04/04/2025
Status
Rewritten
Domain
diag.meethue.com
Type
AAAA
Protocol
Plain DNS
Response details
DNS server
https://doh.opendns.com:443/dns-query
Served from cache
Elapsed
0.28 ms
Rule(s)
/^diag.meethue.com/$important,dnsrewrite=xxxxx.duckdns.org
Custom filtering rules
Response
CNAME: xxxxx.duckdns.org. (ttl=3600)
Response code
SERVFAIL

Time
07:40:45.443
Date
04/04/2025
Status
Rewritten
Domain
diag.meethue.com
Type
AAAA
Protocol
Plain DNS
Response details
DNS server
https://cloudflare-dns.com:443/dns-query
Served from cache
Elapsed
0.28 ms
Rule(s)
/^diag.meethue.com/$important,dnsrewrite=xxxxx.duckdns.org
Custom filtering rules
Response
CNAME: xxxxx.duckdns.org. (ttl=3600)
Response code
NOERROR

[comio]

I have sporadic resolution fails on another xxx.duckdns.org address (used by ddns client). Very strange.