d818ce4957
When the VIRTIO device doesn't report a MAC in config space, generate a random locally-administered unicast MAC instead of panicking with unimplemented!(). This matches Linux 7.1 drivers/net/virtio_net.c virtnet_probe() behavior. Reads /scheme/rand for random bytes; falls back to a fixed MAC if the random source is unavailable. MAC is forced to unicast + locally administered (bit 0=0, bit 1=1).