Finding which packages control network interfaces?

Question

I have a debian package that I'm running on startup.

I'm using upstart and I think I need to add a dependency to the upstart config:

start on someProgram

I'm not sure which program, but I'm not using network-manager, it's disabled. I'm doing something like this:

ethernet=$(ifconfig -a | grep Ethernet | grep ^e | cut -d' ' -f1)
wifi=$(ifconfig -a | grep wl | cut -d' ' -f1)
ping -I $ethernet -c 1 8.8.8.8 \
  || ping -I $wifi -c 1 8.8.8.8 \
  || echo "not online"

Problem is ifconfig doesn't always show the $wifi interface because the program has turned on too early in the startup process.

Also ping -I $ethernet -c 1 8.8.8.8 fails when it should succeed.

If I do sleep 30 then ping it works fine.

Does anyone know what package I should be waiting for to get this to work as expected?

I'm using Ubuntu 14.04 on an embedded device.

3.0.36+ #16 SMP PREEMPT Tue Oct 31 19:17:57 EDT 2017 armv7l armv7l armv7l GNU/Linux

---

I thought I had an answer:

I'm finding that the network interfaces can be referenced directly instead of a package:

start on (local-filesystems and net-device-up IFACE!=lo)

I'd still like to improve it slightly for my case.

Since I'd rather wait for wlan than eth but I'm not sure if I can use a wild card like: IFACE=wlan*

But it seems this doesn't wait for the interface to be available to ifconfig instead it waits for that interface to have an active Internet connection.

Answer 1

I ended up finding a workaround using an upstart pre-start script:

pre-start script
    while [ -z "$(ifconfig | grep wlan)" ]
    do
        sleep 1
    done
    sleep 5
end script