Network disabling does not always work

The test suite has reported once that it found eth0 to be up while the network disabling option was selected in the greeter. There is probably a problem in this feature. Debug log and infos can be found in the 2016 June fragile test referencing ticket (#11087 (closed)).

  Scenario: The Tails Greeter "disable all networking" option disables networking within Tails      # features/checks.feature:99
calling as root: echo 'hello?'
call returned: [0, "hello?\n", ""]
[log] CLICK on (1024,384)
calling as root: /sbin/ifconfig eth0 | grep -q 'inet addr'
call returned: [1, "", "eth0: error fetching interface information: Device not found\n"]
calling as root: date -s '@1465635115'
call returned: [0, "Sat Jun 11 08:51:55 UTC 2016\n", ""]
    Given I have started Tails from DVD without network and stopped at Tails Greeter's login screen # features/step_definitions/snapshots.rb:199
[log] CLICK on (433,404)
    And I enable more Tails Greeter options                                                         # features/step_definitions/common_steps.rb:308
[log] CLICK on (643,447)
    And I disable all networking in the Tails Greeter                                               # features/step_definitions/checks.rb:240
[log] CLICK on (512,671)
[log] CLICK on (812,712)
calling as root: test -e '/etc/sudoers.d/tails-greeter' -o -e '/etc/sudoers.d/tails-greeter-no-password-lecture'
call returned: [1, "", ""]
calling as root: test -e '/etc/sudoers.d/tails-greeter' -o -e '/etc/sudoers.d/tails-greeter-no-password-lecture'
call returned: [0, "", ""]
calling as amnesia: gsettings set org.gnome.desktop.session idle-delay 0
call returned: [0, "", ""]
calling as amnesia: gsettings set org.gnome.desktop.interface toolkit-accessibility true
call returned: [0, "", ""]
calling as amnesia: xdotool search --all --onlyvisible --maxdepth 1 --classname 'Florence'
call returned: [1, "", ""]
    And I log in to a new session                                                                   # features/step_definitions/common_steps.rb:292
calling as root: . /usr/local/lib/tails-shell-library/hardware.sh && get_all_ethernet_nics
call returned: [0, "eth0\n", ""]
    Then no network interfaces are enabled                                                          # features/step_definitions/mac_spoofing.rb:75
      <0> expected but was
      <1>. (Test::Unit::AssertionFailedError)
      ./features/step_definitions/mac_spoofing.rb:79:in `/^(\d+|no) network interface(?:s)? (?:is|are) enabled$/'
      features/checks.feature:104:in `Then no network interfaces are enabled'
      Scenario failed at time 00:58:11

      Screenshot: https://jenkins.tails.boum.org/job/test_Tails_ISO_devel/400/artifact/build-artifacts/00:58:11_The_Tails_Greeter__disable_all_networking__option_disables_networking_within_Tails.png

      Video: https://jenkins.tails.boum.org/job/test_Tails_ISO_devel/400/artifact/build-artifacts/00:58:11_The_Tails_Greeter__disable_all_networking__option_disables_networking_within_Tails.mkv

Related issues

• Related to #6811 (closed)
• Related to #10774

Original created by @bertagaz on 11593 (Redmine)