Comment 1 for bug 1793427

I have a very similar problem when using a PPTP VPN.

I also have Ubuntu 18.04.1 LTS with the following packages installed:

network-manager 1.10.6-2ubuntu1.1
network-manager-config-connectivity-ubuntu 1.10.6-2ubuntu1.1
network-manager-gnome 1.8.10-2ubuntu1
network-manager-pptp 1.2.6-1
network-manager-pptp-gnome 1.2.6-1

systemd 237-3ubuntu10.9

Before connecting to the VPN I see the following permissions in the /run/systemd/resolve directory:

$ ls -l /run/systemd/resolve/
razem 12
drwx------ 2 systemd-resolve systemd-resolve 60 gru 13 23:03 netif
-rw-r--r-- 1 systemd-resolve systemd-resolve 609 gru 13 23:03 resolv.conf
-rw-r--r-- 1 systemd-resolve systemd-resolve 719 gru 13 23:03 stub-resolv.conf
-rw-r--r-- 1 root root 747 gru 13 22:58 stub-resolv.conf.tmp

I do not see any changes in permissions after connecting to the PPTP VPN.

However after disconnecting the VPN the permissions change as in the original bug report:

$ ls -l /run/systemd/resolve/
razem 12
drwx------ 2 systemd-resolve systemd-resolve 60 gru 13 23:23 netif
-rw-r--r-- 1 systemd-resolve systemd-resolve 681 gru 13 23:23 resolv.conf
-rw------- 1 root root 719 gru 13 23:03 stub-resolv.conf
-rw-r--r-- 1 root root 747 gru 13 23:23 stub-resolv.conf.tmp

With such permissions the DNS resolution process is broken.