[PATCH][BZ 21295] getaddrinfo: do not overwrite IPv6 IPs with IPv4 when using AF_UNSPEC

[Florian Weimer]

On 04/20/2017 03:44 PM, kmeaw@kmeaw.com wrote:

> But Ubuntu 12.04 does not:
> 
> root@6e6d4b17326a:/# dpkg-query -s libc6 | grep Version:
> Version: 2.15-0ubuntu10.17
> root@6e6d4b17326a:/# strings /lib/x86_64-linux-gnu/libnss_dns.so.2|grep name4
> root@6e6d4b17326a:/# strings /lib/x86_64-linux-gnu/libnss_dns.so.2|grep name
> __ns_name_unpack
> __ns_name_ntop
> _nss_dns_gethostbyname2_r
> _nss_dns_gethostbyname_r
> _nss_dns_gethostbyname3_r
> __dn_skipname
> _nss_dns_getnetbyname_r
> _nss_dns_getcanonname_r
> root@6e6d4b17326a:/#

Very odd.  This is due to the patch 
debian/patches/all/fedora-nss_dns-gethostbyname4-disable.diff:

# Description: disable _nss_dns_gethostbyname4_r for the moment, as it
#  causes problems for IPv6 users; patch from Fedora by Jakub Jelinek
# Ubuntu: https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/313218
# Upstream: https://bugzilla.redhat.com/show_bug.cgi?id=459756

So your reproducer is indeed very Ubuntu-specific at this point.  (Red 
Hat Enterprise Linux 6 backported the single-request resolver option 
instead, which can be used to work around issues with the parallel lookup.)

We still need to fix this upstream because it's also a bug with AI_ALL 
and AI_V4MAPPED (see my other message).

Thanks,
Florian