Dnsmasq creates "nameserver ::1" in /etc/resolv.cof --> ddns not working anymore

[DocSneider]

Hello,

since upgrading my x86 board (APU2) with a custom build image, the dyndns daemon is not working anymore.

The reason seems to be, that in the "/etc/resolv.conf" a wrong entry is added:

root@OpenWrt ~ # cat  /etc/resolv.conf 
search private
nameserver 127.0.0.1
nameserver ::1

The entry "nameserver ::1" is then used by the ddns daemon, as a parameter for nslookup and causes the following error:

 171357       : #> /usr/bin/nslookup my-url.com  >/var/run/ddns/strato.dat 2>/var/run/ddns/strato.err
 171357 ERROR : BusyBox nslookup error: '1'
 171357       : nslookup: bad address '::1'
 171357  WARN : Get registered/public IP for 'my-url.com' failed - retry 5/0 in 60 seconds

If I delete the entry, the ddns daemon works again.

But where does "nameserver ::1" actually come from?

Here is how the dnsmasq-part of my dhcp config looks like:

config dnsmasq
	option domainneeded '1'
	option localise_queries '1'
	option rebind_protection '1'
	option rebind_localhost '1'
	option local '/lan/'
	option domain 'private'
	option expandhosts '1'
	option allservers '1'
	option noping '0'
	option authoritative '1'
	option readethers '1'
	option leasefile '/tmp/dhcp.leases'
	option localservice '0'
	option cachesize '8192'
	option cachelocal '1'
	list server '1.1.1.1'
	list server '1.0.0.1'
	list server '9.9.9.9'
	option nonwildcard '0'
	option logqueries '0'
	option confdir '/tmp/dnsmasq.d'
	option resolvfile '/tmp/resolv.conf.d/resolv.conf.auto'

Any hints, how to stop dnsmasq from creating this entry?

Thanks in advance!

Some debug information:

root@OpenWrt ~ # opkg info dnsmasq
Package: dnsmasq
Version: 2.86-15
Depends: libc, libubus20220601
Status: install user installed
Architecture: x86_64
Conffiles:
 /etc/config/dhcp ddd520eb24451a892c9c666d83c10c9ea4fc944efbc34a149bc962c56bd8812f
 /etc/dnsmasq.conf 1e6ab19c1ae5e70d609ac7b6246541d52042e4dee1892f825266507ef52d7dfd
Installed-Time: 1666771178

root@OpenWrt ~ # cat /etc/os-release 
NAME="OpenWrt"
VERSION="SNAPSHOT"
ID="openwrt"
VERSION_ID="snapshot"
BUILD_ID="r21112-eb456aedfe"
OPENWRT_BOARD="x86/64"
OPENWRT_ARCH="x86_64"
OPENWRT_TAINTS="no-all busybox"
OPENWRT_RELEASE="OpenWrt SNAPSHOT r21112-eb456aedfe"

root@OpenWrt ~ # cat /proc/version 
Linux version 5.15.74 (openwrt@openWrt-buildhost-ssd) (x86_64-openwrt-linux-musl-gcc (OpenWrt GCC 11.3.0 r21112-eb456aedfe) 11.3.0, GNU ld (GNU Binutils) 2.37) #0 SMP Wed Oct 26 07:59:38 20

[mk24]

::1 is the IPv6 equivalent of 127.0.0.1 in IPv4 -- an address reserved for loopback connections within the local machine.
This entry is in any build it should not break anything.

[rhester72]

By any chance have you taken any deliberate steps to try to disable local IPv6?

[DocSneider]

Thanks for your help @rhester72 & @mk24!

I don´t have that much experience with IPv6. And as I don´t need it in my LAN, I thought I can disable the feature when building the image:

So I think by enabling the option again the problem will be solved.
I will try and give you an update here.

But I wonder why dnsmasq is using IPv6, while the support is disabled?

[rhester72]

I think the way you're disabling it isn't really disabling it.

If /proc/sys/net/ipv6 exists, dnsmasq will add the entry to /etc/resolv.conf.

I don't know how to fully disable IPv6 (at least such that it's not in the kernel, which appears to be the requirement) in OpenWRT, as I've never had the need.

[trendy]

You can configure ddns to use a specific nameserver when looking up the hostname.

[slh]

Disabling IPv6 support at build time if not a supported configuration, don't do that (unless you really, really, really know what you're doing and are willing to fix up whatever comes your way - and even then, just don't).

[DocSneider]

Thanks for your explanation, it´s now clear for me

[DocSneider]

As expected, the problem was gone after re enabling IPv6.
Thanks all for the help!