I can still reproduce this and I've double checked that my IPv4 and v6
settings are identical in terms of both the 'Method' filed (set to
'Automatic VPN' for both) and that both are set to accept all routes
from the VPN server.

Logs are here: https://pastebin.canonical.com/164434/

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https://bugs.launchpad.net/bugs/1603898

Title:
  DNS resolution fails when using VPN and routing all traffic over it

Status in network-manager package in Ubuntu:
  New
Status in network-manager source package in Xenial:
  New

Bug description:
  When using our company VPN, the Network Manager configured dnsmasq
  ends up in a weird state where its unable to answer queries because
  it's (incorrectly) sending them to 127.0.0.1:53 where nothing is
  listening.

  | root@ornery:~# nmcli con show 'Canonical UK - All Traffic' | grep -i dns
  | ipv4.dns:
  | ipv4.dns-search:
  | ipv4.dns-options:                       (default)
  | ipv4.ignore-auto-dns:                   no
  | ipv6.dns:
  | ipv6.dns-search:
  | ipv6.dns-options:                       (default)
  | ipv6.ignore-auto-dns:                   no
  | IP4.DNS[1]:                             10.172.192.1
  | root@ornery:~# ps auxfwwwww | grep [4]035
  | nobody    4035  0.0  0.0  52872  1620 ?        S    Jun29   6:39  \_ 
/usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts --bind-interfaces 
--pid-file=/var/run/NetworkManager/dnsmasq.pid --listen-address=127.0.1.1 
--cache-size=0 --proxy-dnssec 
--enable-dbus=org.freedesktop.NetworkManager.dnsmasq 
--conf-dir=/etc/NetworkManager/dnsmasq.d
  | root@ornery:~# 

  Querying the DNS server provided by the VPN connection works; querying
  dnsmasq doesn't:

  | root@ornery:~# dig +short @10.172.192.1 www.openbsd.org
  | 129.128.5.194
  | root@ornery:~# dig @127.0.1.1 www.openbsd.org
  | 
  | ; <<>> DiG 9.10.3-P4-Ubuntu <<>> @127.0.1.1 www.openbsd.org
  | ; (1 server found)
  | ;; global options: +cmd
  | ;; Got answer:
  | ;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 6996
  | ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
  | 
  | ;; QUESTION SECTION:
  | ;www.openbsd.org.               IN      A
  | 
  | ;; Query time: 0 msec
  | ;; SERVER: 127.0.1.1#53(127.0.1.1)
  | ;; WHEN: Mon Jul 18 10:25:48 CEST 2016
  | ;; MSG SIZE  rcvd: 33
  | 
  | root@ornery:~# 

  While running 'dig @127.0.1.1 www.openbsd.org':

  | root@ornery:~# tcpdump -i lo port 53 -v -n
  | tcpdump: listening on lo, link-type EN10MB (Ethernet), capture size 262144 
bytes
  | 10:26:04.728905 IP (tos 0x0, ttl 64, id 56577, offset 0, flags [none], 
proto UDP (17), length 72)
  |     127.0.0.1.54917 > 127.0.1.1.53: 32273+ [1au] A? www.openbsd.org. (44)
  | 10:26:04.729001 IP (tos 0x0, ttl 64, id 49204, offset 0, flags [DF], proto 
UDP (17), length 61)
  |     127.0.1.1.53 > 127.0.0.1.54917: 32273 Refused$ 0/0/0 (33)

  | root@ornery:~# netstat -anp | grep 127.0.[01].1:53
  | tcp        0      0 127.0.1.1:53            0.0.0.0:*               LISTEN  
    4035/dnsmasq    
  | udp        0      0 127.0.1.1:53            0.0.0.0:*                       
    4035/dnsmasq    
  | root@ornery:~# 

  You can see below a) that dnsmasq thinks it is configured to use a DNS
  server provided by the VPN, and/but that b) it tries to answer a non
  local query like www.openbsd.org locally.

  | root@ornery:~# kill -USR1 4035; tail /var/log/syslog | grep dnsmasq
  | Jul 18 09:29:22 ornery dnsmasq[4035]: time 1468830562
  | Jul 18 09:29:22 ornery dnsmasq[4035]: cache size 0, 0/0 cache insertions 
re-used unexpired cache entries.
  | Jul 18 09:29:22 ornery dnsmasq[4035]: queries forwarded 1880976, queries 
answered locally 375041
  | Jul 18 09:29:22 ornery dnsmasq[4035]: queries for authoritative zones 0
  | Jul 18 09:29:22 ornery dnsmasq[4035]: server 10.172.192.1#53: queries sent 
792, retried or failed 0
  | root@ornery:~# dig +short @127.0.1.1 www.openbsd.org
  | root@ornery:~# kill -USR1 4035; tail /var/log/syslog | grep dnsmasq
  | Jul 18 09:29:22 ornery dnsmasq[4035]: queries for authoritative zones 0
  | Jul 18 09:29:22 ornery dnsmasq[4035]: server 10.172.192.1#53: queries sent 
792, retried or failed 0
  | Jul 18 09:29:37 ornery dnsmasq[4035]: time 1468830577
  | Jul 18 09:29:37 ornery dnsmasq[4035]: cache size 0, 0/0 cache insertions 
re-used unexpired cache entries.
  | Jul 18 09:29:37 ornery dnsmasq[4035]: queries forwarded 1880976, queries 
answered locally 375042
  | Jul 18 09:29:37 ornery dnsmasq[4035]: queries for authoritative zones 0
  | Jul 18 09:29:37 ornery dnsmasq[4035]: server 10.172.192.1#53: queries sent 
792, retried or failed 0
  | root@ornery:~# 

  This is on Ubuntu 16.04, with the following packages:

  | james@ornery:~$ COLUMNS=200 dpkg -l dnsmasq-base network-manager 
network-manager-openvpn | grep ^ii
  | ii  dnsmasq-base                                 2.75-1ubuntu0.16.04.1      
 amd64                       Small caching DNS proxy and DHCP/TFTP server
  | ii  network-manager                              1.2.0-0ubuntu0.16.04.2     
 amd64                       network management framework (daemon and userspace 
tools)
  | ii  network-manager-openvpn                      1.1.93-1ubuntu1            
 amd64                       network management framework (OpenVPN plugin core)
  | james@ornery:~$

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