DragonFlyBSD

The attached program blocks, reliably, in an uninterruptible wait on my DragonFly BSD 6.4 VM if I run it and then:

plug in a USB Wi-FI interface and tell VMware Fusion to attach it to the running VM;

wait for the interface to be attached and to be recognized by the program;

unplug the interface.

It hands in my_getifaddrs() (which is a copy of the DFly BSD getifaddrs()) when it's called after the program receives an RTM_IFINFO message. The hang is in the first sysctl() it does in the loop.

The RTM_IFINFO message is indicating that the carrier state of the removed interface is unknown; after that, an RTM_IFANNOUNCE message is received, indicating that the interface in question was removed, and then another RTM_IFINFO message, for the same interface, is received, again indicating that the carrier state is unknown.

I suspect this will happen on real hardware as well. It may also occur for, for example, Ethernet interfaces, and interfaces on pluggable-at-run-time buses other than USB.