Package: ifupdown
Version: 0.8.19
This code in /lib/udev/ifupdown-hotplug just fails when there is is another
ifup running at the same time:
| local out=$(ps -C ifup ho args)
| if [ "${out%$INTERFACE*}" != "$out" ]; then
| mesg "Already ifup-ing interface $INTERFACE"
| exit 0
| fi
When tracing the execution of that, this is the result:
| + local out=ifup --allow=hotplug veth-foo
| /lib/udev/ifupdown-hotplug: 70: local: veth-foo: bad variable name
The result is, obviously, that the interface simply stays unconfigured.
Commenting out that block seems to "solve" the problem.