Bug#816669: libc6 causes crash of IRSSI due to IPv6

[Loke_AF <loke@gtfo.sadaharu.eu>]

Package: libc6
Version: 2.19-18+deb8u3
Severity: important

Dear Maintainer,

this is my first bug report so apologies in advance if I mess (have messed) something.

IRRSI 0.8.17 started crashing with: "res_query.c:262: __libc_res_nquery: Assertion `(hp != ((void )0)) && (hp2 != ((void )0))' failed."
Problem persisted on every restart of IRSSI after 2 - 35min at random.

The condition that triggered it was "an IPv6 address was configured but no default route was available".
Once IPv6 was properly working again, the problem dissappeared.

Contents of /etc/resolv.conf:
search ovh.net
nameserver 2001:41d0:3:1c7::1
nameserver 213.186.33.99



-- System Information:
Debian Release: 8.3
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libc6 depends on:
ii  libgcc1  1:4.9.2-10

libc6 recommends no packages.

Versions of packages libc6 suggests:
ii  debconf [debconf-2.0]  1.5.56
pn  glibc-doc              <none>
ii  locales-all [locales]  2.19-18+deb8u3

-- debconf information:
  glibc/upgrade: true
  glibc/restart-failed:
* libraries/restart-without-asking: true
  glibc/disable-screensaver:
  glibc/restart-services: vsftpd postfix cron