BUSYBOX: ifplug does not read args from ifplugd.conf

[nleuenberger-zb]

Hi there!

We observed an issue that happens when:

• this default busybox/ifplugd recipe is used
• no systemd (we used sysvinit)
• the ethernet iface gets assigned two ip addresses (e.g. one static + one dhcp)
• the ethernet cable was plugged but then gets unplugged for more than 10 seconds

In this case the ifplugd.action fails with exit 1 and the ifplugd service is terminated:

[ 1077.436072] stm32-dwmac 5800a000.ethernet eth0: Link is Up - 100Mbps/Full - flow control off
ifplugd(eth0): link is up
[ 1079.514909] stm32-dwmac 5800a000.ethernet eth0: Link is Down
ifplugd(eth0): link is down
ifplugd(eth0): executing '/etc/ifplugd/ifplugd.action eth0 down'
ifplugd down
ip: can't send flush request: Cannot assign requested address
ifplugd(eth0): exit code: 1
ifplugd(eth0): exiting

This results in a dead eth0 port. The link is not brought up. Only a manual ifup eth0 resolves the issue.

The root cause seems to be that the busybox version of ifplugd does not read the supplied ifplugd.conf. Therefore the -I that makes it ignore failures of the ifplugd.action script is not enabled.

I've removed the superfluous config file and rolled the relevant arguments (busybox does not support -f and -w) into the start script. Note that I have no idea how this affects systemd enabled systems. But given the if systemd=0 check then I conclude that this is anyway only used for non-systemd.

Let me know if anything else shall be changed or tested more in-depth.
I'm happy to make any required changes.

Cheers, Nik