kill switch induces mystifying failure

[Ian Jackson]

Binary package hint: network-manager

My mother has a Dell laptop with builtin ipw3945 wireless.

Recently she accidentally knocked the hardware wifi kill switch. This caused the network to stop working, as might be expected. However, what ought not to be expected is that there was no indication to the user of what the problem was.

Investigating myself (remotely, via a wired network connection) I found that the ipw3945 driver did know that the hardware was present and that the kill switch was engaged:

Oct 22 15:53:50 friesland kernel: [ 1319.704000] Kill switch must be turned off for wireless networking to work.

However, there was no machinery to bring this to the attention of the user. The driver simply failed to create the appropriate network interface. network-manager stopped seeing it. From the point of view of the higher layers it was as if the hardware had vanished.

Furthermore, after the kill switch was put back to the operational position, the network didn't start working again. I restarted the /sbin/ipw3945d-2.6.20-15-generic daemon to no useful effect. I didn't reload the module by hand; it seems possible that this would have fixed it. But in any case no further user action should be needed.