Bug#998211: libc6: MAXNS should be increased to allow for redundant IPv6 nameservers

[Daniel Gröber <dxld@darkboxed.org>]

Package: libc6
Version: 2.31-13
Severity: important
Tags: ipv6
X-Debbugs-Cc: dxld@darkboxed.org

Dear Maintainer,

glibc currently limits the number of nameserver directives in
resolv.conf to 3. On IPv4/6 dual-stack hosts this can be quite
limiting. When redundant nameservers are available we can either
choose to have redundancy on v4 or v6 which is unsatisfying.

I'm not aware of this problem having been discussed in Debian before,
but Ubuntu has an open bug[1] for it. There also is a surprisingly
insightful Stackoverflow post[2] on how one might go about increasing
MAXNS without an ABI break.

[1]: https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/118930
[2]: https://stackoverflow.com/questions/64047757/more-than-3-dns-server-in-ubuntu

--Daniel

-- System Information:
Debian Release: 11.0
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 5.10.0-6-amd64 (SMP w/16 CPU threads)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages libc6 depends on:
ii  libcrypt1  1:4.4.18-4
ii  libgcc-s1  10.2.1-6

Versions of packages libc6 recommends:
ii  libidn2-0       2.3.0-5
ii  libnss-nis      3.1-4
ii  libnss-nisplus  1.3-4

Versions of packages libc6 suggests:
ii  debconf [debconf-2.0]  1.5.77
pn  glibc-doc              <none>
ii  libc-l10n              2.31-13
ii  locales                2.31-13

-- debconf information excluded