[OpenBSD]

Manual Page Search Parameters
CDCE(4) Device Drivers Manual CDCE(4)

cdce —
USB Communication Device Class Ethernet device

cdce* at uhub?

The cdce driver provides support for USB Host-to-Host (aka USB-to-USB) bridges based on the USB Communication Device Class (CDC) and Ethernet subclass, including the following:
The USB bridge appears as a regular network interface on both sides, transporting Ethernet frames. USB 1.x bridges support speeds of up to 12Mbps, and USB 2.0 speeds of up to 480Mbps. Packets are received and transmitted over separate USB bulk transfer endpoints.
The cdce driver does not support different media types or options. For more information on configuring this device, see ifconfig(8).

cdce0: extra ethernet descriptor
There is more than one Ethernet descriptor.
cdce0: no data interface
The data interface announced by the union descriptor cannot be found.
cdce0: no descriptor for interrupt endpoint N
cdce0: interface alternate setting N failed
cdce0: no descriptor for bulk endpoint N
cdce0: could not find data bulk in/out
For a manually added USB vendor/product, these errors indicate that the bridge is not compatible with the driver.
cdce0: watchdog timeout
A packet was queued for transmission and a transmit command was issued, however the device failed to acknowledge the transmission before a timeout expired.
cdce0: no memory for rx list -- packet dropped!
Memory allocation through MGETHDR or MCLGET failed, the system is running low on mbufs.
cdce0: abort/close rx/tx/interrupt pipe failed
cdce0: rx/tx list init failed
cdce0: open rx/tx/interrupt pipe failed
cdce0: usb error on rx/tx

arp(4), intro(4), netintro(4), usb(4), hostname.if(5), ifconfig(8)
Universal Serial Bus Class Definitions for Communication Devices, http://www.usb.org/developers/docs/devclass_docs/.
Data sheet Prolific PL-2501 Host-to-Host Bridge/Network Controller.

The cdce device driver first appeared in OpenBSD 3.6.

The cdce driver was written by Craig Boston <craig@tobuj.gank.org> based on the aue(4) driver written by Bill Paul <wpaul@windriver.com> and ported to OpenBSD by Daniel Hartmeier <dhartmei@openbsd.org>.

Many USB devices notoriously fail to report their class and interfaces correctly. Undetected products might work flawlessly when their vendor and product IDs are added to the driver manually.
November 13, 2016 OpenBSD-6.1