[Bug 1671606] Re: DNS server from vpn connection is not being used after network-manager upgrade to 1.2.6-0ubuntu0.16.04.1

[Mercury]

Ryan,

The problem is not that a recent change in resolvconf caused a
regression.

The problem with resolvconf is that the upgrade to network-manager
exposed an existing bug in resolvconf.

This happens because the new version of network-manager now tells
resolvconf that it must only use a specific interface when talking to
the name server, and resolvconf was not properly tracking how interfaces
were added and removed from the system.

This is most obvious for VPN connections which use an interface for VPN
traffic, as that interface will be destroyed and recreated on every VPN
connection, triggering the bug in resolvconf. (Setting up the new DNS
for the new VPN interface is insufficient to make it happy.)

This can also be triggered on systems that remove and readd interfaces
for things like suspend or hibernate.

Redhat documented the bug fairly well when they found it, their bug
report on the matter is
https://bugzilla.redhat.com/show_bug.cgi?id=1373485

The actual patch that needs to be applied is git commit
2675f2061525bc954be14988d64384b74aa7bf8b, and the upstream gitweb URL
for viewing the diff is:
http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=2675f2061525bc954be14988d64384b74aa7bf8b

There is a separate (but very related) issue, in that some existing VPNs
that involve ipsec have one interface for sending traffic and to hold an
IP, but the response traffic appears on the interface of the primary
internet connection.  This is completely broken in the middle of an LTS
by this change, and fixing the bug in resolvconf won't help.  I'm still
trying to sort out the right answer for some of my VPN use cases there.

** Changed in: resolvconf (Ubuntu)
       Status: Invalid => Confirmed

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https://bugs.launchpad.net/bugs/1671606

Title:
  DNS server from vpn connection is not being used after network-manager
  upgrade to 1.2.6-0ubuntu0.16.04.1

Status in network-manager package in Ubuntu:
  Confirmed
Status in resolvconf package in Ubuntu:
  Confirmed

Bug description:
  I use my company's cisco vpn via network-manager in Ubuntu 16.04.2
  LTS. After recent upgrade of network-manager:amd64 from version
  1.2.2-0ubuntu0.16.04.4 to version 1.2.6-0ubuntu0.16.04.1 DNS
  resolution of VPN's server hostnames does not work. Roll back to
  version 1.2.2-0ubuntu0.16.04.4 solves the problem.

  Steps for reproducing:
  1. upgrade network-manager:amd64 from version 1.2.2-0ubuntu0.16.04.4 to version 1.2.6-0ubuntu0.16.04.1
  2. connect to VPN via network-manager applet
  3. nslookop servername.internal --> ** server can't find servername.internal: NXDOMAIN
  4. disconnect from VPN via network-manager applet
  5. roll back network-manager via command: sudo apt-get install network-manager=1.2.2-0ubuntu0.16.04.4
  6. restart network-manager via sudo service network-manager restart
  7. connect to VPN via network-manager applet
  8. nslookop servername.internal --> the server is resolved correctly

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: network-manager 1.2.6-0ubuntu0.16.04.1
  ProcVersionSignature: Ubuntu 4.4.0-66.87-generic 4.4.44
  Uname: Linux 4.4.0-66-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.5
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Thu Mar  9 19:49:55 2017
  InstallationDate: Installed on 2015-10-05 (520 days ago)
  InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
  NetworkManager.state:
   [main]
   NetworkingEnabled=true
   WirelessEnabled=true
   WWANEnabled=true
   WimaxEnabled=true
  SourcePackage: network-manager
  UpgradeStatus: No upgrade log present (probably fresh install)
  nmcli-nm:
   RUNNING  VERSION  STATE      STARTUP  CONNECTIVITY  NETWORKING  WIFI-HW  WIFI     WWAN-HW  WWAN
   running  1.2.6    connected  started  full          enabled     enabled  enabled  enabled  enabled

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