﻿id	summary	reporter	owner	description	type	status	component	version	resolution	keywords	cc	guest	host
20977	The natdnshostresolver DNS server may incorrectly answer NXDOMAIN instead of NOERROR for AAAA requests	optaget		"I am running a Windows guest on a Windows host. The guest thinks it has IPv6 connectivity (I need this for testing something on ::1) while the host does not think it has IPv6 connectivity.

If I run ""dig aaaa wwww.dr.dk"" in the host I get:

{{{
; <<>> DiG 9.16.1-Ubuntu <<>> aaaa www.dr.dk
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36226
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;www.dr.dk.                     IN      AAAA

;; ANSWER SECTION:
www.dr.dk.              3       IN      CNAME   www.dr.dk-v1.edgekey.net.
www.dr.dk-v1.edgekey.net. 330   IN      CNAME   e16198.dscb.akamaiedge.net.
e16198.dscb.akamaiedge.net. 7   IN      AAAA    2a02:26f0:3b:2bc::3f46
e16198.dscb.akamaiedge.net. 7   IN      AAAA    2a02:26f0:3b:295::3f46
e16198.dscb.akamaiedge.net. 7   IN      AAAA    2a02:26f0:3b:29c::3f46
e16198.dscb.akamaiedge.net. 7   IN      AAAA    2a02:26f0:3b:286::3f46
e16198.dscb.akamaiedge.net. 7   IN      AAAA    2a02:26f0:3b:2a2::3f46

;; Query time: 60 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Fri Jun 10 13:45:00 CEST 2022
;; MSG SIZE  rcvd: 253
}}}
If I run it in the guest I get:
{{{
; <<>> DiG 9.16.28 <<>> aaaa www.dr.dk
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 2870
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: fcdf863339a0e226 (echoed)
;; QUESTION SECTION:
;www.dr.dk.                     IN      AAAA

;; Query time: 0 msec
;; SERVER: 10.0.2.3#53(10.0.2.3)
;; WHEN: Fri Jun 10 11:45:18 Coordinated Universal Time 2022
;; MSG SIZE  rcvd: 50
}}}
The fact that the guest receives NXDOMAIN is problematic: If Windows thinks it has both IPv4 and IPv6 connectivity, it will make an A and an AAAA DNS lookup in parallel for a given hostname. However, if it first receives an NXDOMAIN for the AAAA request, it will immediately conclude that there are no A records either. In practice this means that DNS lookups often fail for me in the guest.

I believe the behavior of Windows is correct. See https://datatracker.ietf.org/doc/html/rfc2308."	defect	closed	other	VirtualBox 6.1.34	fixed			Windows	Windows
