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

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