cdce(4) USB Communication Device Class Ethernet driver


To compile this driver into the kernel, place the following lines in your kernel configuration file:
device uhci device ohci device usb device cdce

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf5:



The driver provides support for USB Host-to-Host (aka USB-to-USB) and USB-to-Ethernet bridges based on the USB Communication Device Class (CDC) and Ethernet subclass.

The USB bridge appears as a regular network interface on both sides, transporting Ethernet frames.

For more information on configuring this device, see ifconfig(8).

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 driver does not support different media types or options.


The following devices are supported by the driver:

  • Prolific PL-2501 Host-to-Host Bridge Controller
  • Sharp Zaurus PDA
  • Terayon TJ-715 DOCSIS Cable Modem


"cdce%d: no union descriptor"
The driver could not fetch an interface descriptor from the USB device. For a manually added USB vendor/product, the CDCE_NO_UNION flag can be tried to work around the missing descriptor.
"cdce%d: no data interface"
"cdce%d: could not read endpoint descriptor"
"cdce%d: unexpected endpoint"
"cdce%d: 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.
"cdce%d: 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.
"cdce%d: no memory for rx list -- packet dropped!"
Memory allocation through MGETHDR or MCLGET failed, the system is running low on mbufs.
"cdce%d: abort/close rx/tx pipe failed"
"cdce%d: rx/tx list init failed"
"cdce%d: open rx/tx pipe failed"
"cdce%d: usb error on rx/tx"


The device driver first appeared in Ox 3.6 , Nx 3.0 and Fx 6.0 .


An -nosplit The driver was written by An Craig Boston Aq [email protected] based on the aue(4) driver written by An Bill Paul Aq [email protected] and ported to Ox by An Daniel Hartmeier Aq [email protected] .


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.