Comment 28 for bug 900384

found this on usbip.sourceforge.net:

Download

For Linux, the source code of usbip was merged into the staging tree, and finally has been moved to the mainline since Linux-3.17. Development is ongoing in the kernel community, not here. Linux distributions will provide binary packages of usbip. Just for historical records, the project page keeps old download files of the Linux version. Do not use them.

However, in newest kernel it don't work (4.4.0-12 / lubuntu 16.04) even if i can find:
./lib/modules/4.4.0-12-generic/kernel/drivers/usb/usbip
./lib/modules/4.4.0-12-generic/kernel/drivers/usb/usbip/usbip-host.ko
./lib/modules/4.4.0-12-generic/kernel/drivers/usb/usbip/usbip-core.ko