/etc/resolv.conf turns 0640 after closing connection

[Robert Sander]

After I close the connection DNS resolving does not work any more as the file linked to from /etc/resolv.conf is not world-readable:

lrwxrwxrwx 1 root root 39 Mär 14 21:04 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf

root:/run/systemd/resolve# ls -l
insgesamt 12
drwxr-xr-x 3 systemd-resolve systemd-resolve 120 Aug 30 15:01 .
drwxr-xr-x 20 root root 460 Aug 30 14:44 ..
drwx------ 2 systemd-resolve systemd-resolve 60 Aug 30 15:01 netif
-rw-r--r-- 1 systemd-resolve systemd-resolve 640 Aug 30 15:01 resolv.conf
-rw------- 1 root root 715 Aug 30 14:55 stub-resolv.conf
-rw-r--r-- 1 root root 733 Aug 30 14:55 stub-resolv.conf.tmp

I have to run

sudo chmod 0640 /run/systemd/resolve/stub-resolv.conf

to be able to use DNS again.

/etc/nsswitch.conf contains:

hosts: files dns

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: network-manager-strongswan 1.4.2-2
ProcVersionSignature: Ubuntu 5.0.0-25.26~18.04.1-generic 5.0.18
Uname: Linux 5.0.0-25-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.7
Architecture: amd64
CurrentDesktop: XFCE
Date: Fri Aug 30 15:10:21 2019
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-trusty-amd64-osp1-20150720-0
InstallationDate: Installed on 2016-06-01 (1184 days ago)
InstallationMedia: Ubuntu 14.04 "Trusty" - Build amd64 LIVE Binary 20150720-04:06
SourcePackage: network-manager-strongswan
UpgradeStatus: Upgraded to bionic on 2018-08-22 (373 days ago)