[SOLVED] Detecting hotplugged Ethernet cables in OpenBSD

Turbocapitalist · 10-23-2017, 11:16 AM

What is the best way to trigger a script when specific Ethernet interfaces go from status "no carrier" to status "active" and back again?

I'm aware of hotplugd(8) which can detect the status of some devices but not able to find how to make it aware of whether specific Ethernet cables are plugged in or not.

jggimi · 10-23-2017, 11:39 AM

You want ifstated(8) and ifstated.conf(5).

Turbocapitalist · 10-23-2017, 12:43 PM

Sweet. That was hiding in plain sight. The manual pages hostname.if(5) and hotplugd(8) don't mention it at all. The example configuration is a great help though. Now I just have to work out the logic of having hot swappable egress without race conditions.

jggimi · 10-23-2017, 01:33 PM

The hotplugd(8) tool is used for device additions and removals, which occur on a bus (PCI, USB, etc.) That's a little different than a state change reported through an existing NIC.

Consider the case of a USB-attached NICs. The attach/detach of the NIC to the bus would be managed by hotplug(). The state of the network cabling attached to the NIC could be managed by ifstated().

And ifstated() can be used with external scripts so that you can manage all sorts of states. Not just a NIC's media interface.