Bug#791920: systemd: with ifupdown, ifup at .service forces ifup eth0 even with no Ethernet link

[Vincent Lefevre]

Package: systemd
Version: 222-1
Severity: important

Note: the following applies when /etc/network/interfaces contains:

allow-hotplug eth0
iface eth0 inet dhcp

which is the default.

With ifupdown, ifup at .service forces ifup eth0 even with no Ethernet
link (e.g. no Ethernet cable plugged in), which is
  * bad because this hangs the boot for several dozens of seconds;
  * useless because when there is an Ethernet link, eth0 is already
    brought up by the /etc/init.d/networking script.

For instance, when there is an Ethernet link:

Jul 09 16:43:01 zira systemd[1]: Starting LSB: Raise network interfaces....
-- Subject: Unit networking.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit networking.service has begun starting up.
[...]
Jul 09 16:43:01 zira networking[541]: Configuring interface eth0=eth0 (inet)
[...]
Jul 09 16:43:01 zira networking[541]: done.
Jul 09 16:43:01 zira systemd[1]: Started LSB: Raise network interfaces..
-- Subject: Unit networking.service has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit networking.service has finished starting up.
-- 
-- The start-up result is done.
Jul 09 16:43:01 zira systemd[1]: Starting ifup for eth0...
-- Subject: Unit ifup at eth0.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit ifup at eth0.service has begun starting up.
Jul 09 16:43:01 zira ifup[771]: /sbin/ifup: interface eth0 already configured
[...]

As you can see, ifup at eth0.service starts up, but it is useless
because interface eth0 is already configured.

However, when there is no Ethernet link, eth0 is not configured
because /etc/init.d/networking does link detection. But there is
no link detection for ifup at eth0.service, which yields a freeze.

-- Package-specific info:

-- System Information:
Debian Release: stretch/sid
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/8 CPU cores)
Locale: LANG=POSIX, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd depends on:
ii  adduser         3.113+nmu3
ii  libacl1         2.2.52-2
ii  libapparmor1    2.9.2-3
ii  libaudit1       1:2.4.2-1
ii  libblkid1       2.26.2-6
ii  libc6           2.19-18
ii  libcap2         1:2.24-9
ii  libcap2-bin     1:2.24-9
ii  libcryptsetup4  2:1.6.6-5
ii  libgcrypt20     1.6.3-2
ii  libkmod2        20-1
ii  liblzma5        5.1.1alpha+20120614-2.1
ii  libmount1       2.26.2-6
ii  libpam0g        1.1.8-3.1
ii  libseccomp2     2.2.1-2
ii  libselinux1     2.3-2+b1
ii  libsystemd0     222-1
ii  mount           2.26.2-6
ii  sysv-rc         2.88dsf-59.2
ii  udev            222-1
ii  util-linux      2.26.2-6

Versions of packages systemd recommends:
ii  dbus            1.8.18-1
ii  libpam-systemd  222-1

Versions of packages systemd suggests:
pn  systemd-ui  <none>

-- Configuration Files:
/etc/systemd/journald.conf changed:
[Journal]
Storage=persistent


-- no debconf information