usbip needs to be bumped as linux 4.13's one has some incompatible changes. https://github.com/torvalds/linux/commit/dff3565b8e1c0be6fc83ba47dcab45c149dcab5b#diff-1860d675dbf910a8f3f01825f849e7cf Due to this change, net-misc/usbip-3.19 fails on Linux 4.13 as it has to refer USBIP_VHCI_DEVICE_NAME(/sys/bus/platform/devices/vhci_hcd.0) instead of USBIP_VHCI_DRV_NAME(/sys/class/platform/vhci_hcd).
Added 4.13.
I already asked robbat2 to bump sys-apps/linux-misc-apps in bug 634614, going forward this should be the package to get usbip userspace tools from.