Upgrade of procps disables net.ipv4.ip_forward=1

[Jonathan Kaulard]

Expected behavior:
Settings in /etc/sysctl.conf won't be changed by an upgrade or there will be a prompt if the original file should be overwritten.

What happened:
After performing an upgrade of package procps IPv4Forwarding was disabled in /etc/sysctl.conf without asking:

# Uncomment the next line to enable packet forwarding for IPv4
#net.ipv4.ip_forward=1

I was able to reproduce this behavior by using unattended-upgrades and also by upgrading manually (apt-get upgrade)

My system:

lsb_release -rd
Description: Ubuntu 18.04.2 LTS
Release: 18.04

apt-cache policy procps
procps:
  Installed: 2:3.3.12-3ubuntu1.1
  Candidate: 2:3.3.12-3ubuntu1.1
  Version table:
 *** 2:3.3.12-3ubuntu1.1 500
        500 http://de.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2:3.3.12-3ubuntu1 500
        500 http://de.archive.ubuntu.com/ubuntu bionic/main amd64 Packages

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.