man/man4/cdce.4

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.\" $NetBSD: cdce.4,v 1.4 2004/12/08 18:35:56 peter Exp $
.\"
.Dd December 23, 2025
.Dt CDCE 4
.Os
.Sh NAME
.Nm cdce
.Nd USB Communication Device Class Ethernet (ECM/NCM) driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device uhci"
.Cd "device ohci"
.Cd "device usb"
.Cd "device miibus"
.Cd "device uether"
.Cd "device cdce"
.Ed
.Pp
Mobile Devices (e.g., Huawei E3372, E5573 and others)
may need additionally the u3g command port:
.Bd -ragged -offset indent
.Cd "device ucom"
.Cd "device u3g"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
if_cdce_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for USB Host-to-Host (aka USB-to-USB) and
USB-to-Ethernet bridges based on the USB Communication Device Class
Ethernet Control Model (CDC ECM) and Network Control Model (CDC NCM)
specifications.
It also provides device-side CDC ECM support.
.Pp
The USB bridge appears as a regular network interface on both sides,
transporting Ethernet frames.
.Pp
For more information on configuring this device, see
.Xr ifconfig 8 .
.Pp
USB 1.x bridges support speeds of up to 12Mbps, and USB 2.0 speeds of
up to 480Mbps.
.Pp
Packets are
received and transmitted over separate USB bulk transfer endpoints.
.Pp
The
.Nm
driver does not support different media types or options.
.Sh HARDWARE
The
.Nm
driver supports USB Ethernet interfaces implementing the
USB Communication Device Class Ethernet Control Model (CDC ECM) or
Network Control Model (CDC NCM) protocol, such as:
.Pp
.Bl -bullet -compact
.It
Android USB tethering
.It
iPhone USB tethering
.It
Realtek RTL8153 USB 3.0 to Gigabit Ethernet controller
.It
Prolific PL-2501 Host-to-Host Bridge controller
.It
Sharp Zaurus PDA
.It
Terayon TJ-715 DOCSIS Cable Modem
.It
Huawei 3G/4G LTE (e.g., E3372, E5573) and other mobile network devices
.El
.Sh EXAMPLES
Mobile
.Nm
Network Devices may need a connect command sequence via the
.Xr u3g 4
serial command port before activating the NCM/ECM/ACM network interface.
For example:
.Pp
.Dl echo 'AT^NDISUP=1,1,"internet"' > /dev/cuaU[0].0
.Pp
Wwhere
.Dq internet
is your providers apn name.
.Sh DIAGNOSTICS
.Bl -diag
.It "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.
.It "cdce%d: no data interface"
.It "cdce%d: could not read endpoint descriptor"
.It "cdce%d: unexpected endpoint"
.It "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.
.It "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.
.It "cdce%d: no memory for rx list -- packet dropped!"
Memory allocation through MGETHDR or MCLGET failed, the system
is running low on mbufs.
.It "cdce%d: abort/close rx/tx pipe failed"
.It "cdce%d: rx/tx list init failed"
.It "cdce%d: open rx/tx pipe failed"
.It "cdce%d: usb error on rx/tx"
.El
.Sh SEE ALSO
.Xr arp 4 ,
.Xr cdceem 4 ,
.Xr intro 4 ,
.Xr ipheth 4 ,
.Xr netintro 4 ,
.Xr u3g 4 ,
.Xr ucom 4 ,
.Xr urndis 4 ,
.Xr usb 4 ,
.Xr ifconfig 8
.Rs
.%T "Universal Serial Bus Class Definitions for Communication Devices"
.%U http://www.usb.org/developers/devclass_docs/usbcdc11.pdf
.Re
.Rs
.%T "Data sheet Prolific PL-2501 Host-to-Host Bridge/Network Controller"
.%U http://tech.prolific.com.tw/visitor/fcabdl.asp?fid=20679530
.Re
.Sh HISTORY
The
.Nm
device driver first appeared in
.Ox 3.6 ,
.Nx 3.0
and
.Fx 6.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Craig Boston Aq Mt craig@tobuj.gank.org
based on the
.Xr aue 4
driver written by
.An Bill Paul Aq Mt wpaul@windriver.com
and ported to
.Ox
by
.An Daniel Hartmeier Aq Mt dhartmei@openbsd.org .
.Sh CAVEATS
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.