[Bug 1579640] Re: IPv6 nameservers not removed from /etc/resolv.conf when switching to a IPv4 network

[Rémi Denis-Courmont]

rdnssd simply tracks the kernel notion's of what are the RDNSS at a
time. The kernel did not send expiration for the entries when you left
the network, hence the entries are considered still valid.

What you want is an integrated IPv4/IPv6 connection manager, like e..
network-manager. This is way out of scope of rdnssd.

** Changed in: ndisc6 (Ubuntu)
       Status: New => Invalid

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Title:
  IPv6 nameservers not removed from /etc/resolv.conf when switching to a
  IPv4 network

Status in ndisc6 package in Ubuntu:
  Invalid

Bug description:
  I installed rdnssd on a laptop which I mostly use in two places. At
  one place, I have  dual stack network, with dual stack DNS servers, in
  the other place, the network is IPv4 only.

  When I go to the first place, rdnssd correctly receives the advertised
  DNS (IPv6) servers and places them in /etc/resolv.conf. Everything
  works.

  However, when I go to the second network, the IPv6 addresses for the
  DNS servers remain in /etc/resolv.conf, and that means networking
  mostly doesn't work, since most DNS queries are sent to the two IPv6
  addresses which are now "Network unreachable".

  When switching to a IPv4 only network (or an IPv6 network which
  doesn't advertise IPv6 addresses for it's DNS via RDNSS), the IPv6
  addresses of the DNS should be removed from /etc/resolv.conf

  lsb_release -rd
  Description:	Ubuntu 14.04.4 LTS
  Release:	14.04

  apt-cache policy rdnssd
  rdnssd:
    Installed: 1.0.1-1ubuntu1
    Candidate: 1.0.1-1ubuntu1
    Version table:
   *** 1.0.1-1ubuntu1 0
          500 http://ftp.arnes.si/pub/mirrors/ubuntu/ trusty/universe amd64 Packages
          100 /var/lib/dpkg/status

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: rdnssd 1.0.1-1ubuntu1
  ProcVersionSignature: Ubuntu 3.19.0-58.64~14.04.1-generic 3.19.8-ckt16
  Uname: Linux 3.19.0-58-generic x86_64
  NonfreeKernelModules: nvidia wl
  ApportVersion: 2.14.1-0ubuntu3.19
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Mon May  9 09:16:48 2016
  InstallationDate: Installed on 2015-11-28 (162 days ago)
  InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
  SourcePackage: ndisc6
  UpgradeStatus: No upgrade log present (probably fresh install)

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