[Bug 1717015] Re: libc resolver stops searching domain search list after getting back NSEC record

[Florian Weimer]

Do you have packet captures which demonstrate the problem?  We will need
the data exchanged between the host which performs the DNS lookup and
the recursive resolvers configured in resolv.conf.

We are pretty sure that the stub resolver is tolerant to unknown DNS
record types, so the behavior you report is rather odd.

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https://bugs.launchpad.net/bugs/1717015

Title:
  libc resolver stops searching domain search list after getting back
  NSEC record

Status in glibc package in Ubuntu:
  New

Bug description:
  Suppose that:

  1. you have a "search" line in your /etc/resolv.conf file;
  2. it has two domains in it; and
  3. the first of the two domains does DNSSEC, including returning NSEC records for nonexisting hosts.

  In this situation, when you try to look up a host name in the second
  domain without specifying the domain part of the host name, the libc
  resolver will stop after it gets back the NSEC record and report that
  the host name doesn't exist, rather than moving on to the second
  domain in the search list and searching for the host in that domain.

  See also https://bugs.launchpad.net/ubuntu/+source/bind9/+bug/1717014
  .

  ProblemType: Bug
  DistroRelease: Ubuntu 17.04
  Package: libc6 2.24-9ubuntu2.2
  ProcVersionSignature: Ubuntu 4.10.0-33.37-generic 4.10.17
  Uname: Linux 4.10.0-33-generic x86_64
  ApportVersion: 2.20.4-0ubuntu4.5
  Architecture: amd64
  CurrentDesktop: Unity:Unity7
  Date: Wed Sep 13 16:00:45 2017
  Dependencies:
   gcc-6-base 6.3.0-12ubuntu2
   libc6 2.24-9ubuntu2.2
   libgcc1 1:6.3.0-12ubuntu2
  InstallationDate: Installed on 2016-08-09 (400 days ago)
  InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
  SourcePackage: glibc
  UpgradeStatus: Upgraded to zesty on 2017-04-19 (147 days ago)

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