[Bug 1717995] Re: extra domains not removed from resolv.conf when VPN disconnects

[Walter Garcia-Fontes]

Same for me. I really don't understand how /etc/resolv.conf should be
managed in Ubuntu 17.04. I have the setup described in comment #7. I
tried to have only network-manager manage /etc/resolv.conf, but then I
loose name resolution in containers.

I think we should open a new bug report, as this one marked with "Fix
released" will never get attention. It may also something worth
investigating upstream.

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Title:
  extra domains not removed from resolv.conf when VPN disconnects

Status in systemd package in Ubuntu:
  Fix Released

Bug description:
  I use a VPN (network manager "vpnc" config) to connect to my work
  network.  The gateway is "webvpn.purestorage.com".  When I connect, I
  get "purestorage.com" added to the "search" line in my
  /etc/resolv.conf (and /run/resolvconf/interface/systemd-resolved) -
  which makes perfect sense, the VPN passes this info to me and then I
  can connect to systems within the work network without having to use a
  FQDN.

  The bug (which is a regression from older versions of Ubuntu) is that
  when I lose my connection to the VPN (either because I disconnect
  explicitly, or because the network goes down or I suspend my laptop),
  the "purestorage.com" domain is not removed from those "search" lines.
  And for some reason this prevents me from resolving
  webvpn.purestorage.com (which prevents me from reconnecting to the
  VPN).

  In particular, if I connect and disconnect my VPN, I get:

   $ systemd-resolve webvpn.purestorage.com
  webvpn.purestorage.com: resolve call failed: No appropriate name servers or networks for name found

  If I then edit /etc/resolv.conf by hand to remove all the
  purestorage.com entries from the search line - in other words, change

   $ cat /etc/resolv.conf 
  # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
  #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
  # 127.0.0.53 is the systemd-resolved stub resolver.
  # run "systemd-resolve --status" to see details about the actual nameservers.

  nameserver 127.0.0.53
  search home.digitalvampire.org purestorage.com dev.purestorage.com

  to

   $ cat /etc/resolv.conf 
  # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
  #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
  # 127.0.0.53 is the systemd-resolved stub resolver.
  # run "systemd-resolve --status" to see details about the actual nameservers.

  nameserver 127.0.0.53
  search home.digitalvampire.org

  and change nothing else, then:

   $ systemd-resolve webvpn.purestorage.com
  webvpn.purestorage.com: 192.30.189.1
                          (vpn.purestorage.com)

  -- Information acquired via protocol DNS in 25.9ms.
  -- Data is authenticated: no

  
  I'm not sure if the bug is in systemd, network manager, or some other package, but I'm happy to try any debugging that is helpful to resolve this (no pun intended).

  ProblemType: Bug
  DistroRelease: Ubuntu 17.10
  Package: systemd 234-2ubuntu10
  ProcVersionSignature: Ubuntu 4.12.0-13.14-generic 4.12.10
  Uname: Linux 4.12.0-13-generic x86_64
  ApportVersion: 2.20.7-0ubuntu1
  Architecture: amd64
  CurrentDesktop: GNOME
  Date: Mon Sep 18 11:20:17 2017
  InstallationDate: Installed on 2016-09-01 (381 days ago)
  InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Alpha amd64 (20160901)
  MachineType: LENOVO 20FRS2FK00
  ProcEnviron:
   TERM=screen
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.12.0-13-generic root=UUID=30d5ada5-835d-4cf7-96cf-3329c0316107 ro quiet splash vt.handoff=7
  SourcePackage: systemd
  UpgradeStatus: Upgraded to artful on 2017-07-26 (53 days ago)
  dmi.bios.date: 07/13/2017
  dmi.bios.vendor: LENOVO
  dmi.bios.version: N1FET53W (1.27 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 20FRS2FK00
  dmi.board.vendor: LENOVO
  dmi.board.version: SDK0J40697 WIN
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 31
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: None
  dmi.modalias: dmi:bvnLENOVO:bvrN1FET53W(1.27):bd07/13/2017:svnLENOVO:pn20FRS2FK00:pvrThinkPadX1Yoga1st:rvnLENOVO:rn20FRS2FK00:rvrSDK0J40697WIN:cvnLENOVO:ct31:cvrNone:
  dmi.product.family: ThinkPad X1 Yoga 1st
  dmi.product.name: 20FRS2FK00
  dmi.product.version: ThinkPad X1 Yoga 1st
  dmi.sys.vendor: LENOVO

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