Unbound fails to resolve DNS if the system has IPv6 enabled but IPv6 connectivity is broken

[adrelanos]

Describe the bug

Unbound fails to resolve DNS if the system has IPv6 enabled but IPv6 connectivity is broken.

Does unbound attempt to fallback on IPv4 in case IPv6 is broken?

To reproduce

Steps to reproduce the behavior:

1. Debian bookworm
2. Install dnssec-trigger
3. nslookup

Expected behavior

Functional DNS.

System:

• Unbound version: 1.17.1
• OS: Debian bookworm
• unbound -V output:

Version 1.17.1

Configure line: --build=x86_64-linux-gnu --prefix=/usr --includedir=${prefix}/include --mandir=${prefix}/share/man --infodir=${prefix}/share/info --sysconfdir=/etc --localstatedir=/var --disable-option-checking --disable-silent-rules --libdir=${prefix}/lib/x86_64-linux-gnu --runstatedir=/run --disable-maintainer-mode --disable-dependency-tracking --with-pythonmodule --with-pyunbound --enable-subnet --enable-dnstap --enable-systemd --with-libnghttp2 --with-chroot-dir= --with-dnstap-socket-path=/run/dnstap.sock --disable-rpath --with-pidfile=/run/unbound.pid --with-libevent --enable-tfo-client --with-rootkey-file=/usr/share/dns/root.key --enable-tfo-server
Linked libs: libevent 2.1.12-stable (it uses epoll), OpenSSL 3.0.9 30 May 2023
Linked modules: dns64 python subnetcache respip validator iterator
TCP Fastopen feature available

BSD licensed, see LICENSE in source package for details.
Report bugs to [email protected] or https://github.com/NLnetLabs/unbound/issues