1.\" 2.\" SPDX-License-Identifier: BSD-2-Clause 3.\" 4.\" Copyright (c) 2019 Edward Tomasz Napierala <trasz@FreeBSD.org> 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.Dd September 18, 2025 27.Dt CDCEEM 4 28.Os 29.Sh NAME 30.Nm cdceem 31.Nd USB Communication Device Class Ethernet Emulation Model driver 32.Sh SYNOPSIS 33To compile this driver into the kernel, 34place the following lines in your 35kernel configuration file: 36.Bd -ragged -offset indent 37.Cd "device uhci" 38.Cd "device ohci" 39.Cd "device usb" 40.Cd "device miibus" 41.Cd "device uether" 42.Cd "device cdceem" 43.Ed 44.Pp 45Alternatively, to load the driver as a 46module at boot time, place the following line in 47.Xr loader.conf 5 : 48.Bd -literal -offset indent 49if_cdceem_load="YES" 50.Ed 51.Sh DESCRIPTION 52The 53.Nm 54driver provides support for USB devices based on the USB Communication 55Device Class Ethernet Emulation Model (CDC EEM) specification. 56.Pp 57The driver works on both host, and device-side; see 58.Xr usb_template 4 59for details. 60.Pp 61The USB device appears as a regular network interface on both sides, 62transporting Ethernet frames. 63.Pp 64For more information on configuring this device, see 65.Xr ifconfig 8 . 66.Pp 67The 68.Nm 69driver does not support different media types or options. 70.Sh SYSCTL VARIABLES 71The following variables are available as both 72.Xr sysctl 8 73variables and 74.Xr loader 8 75tunables: 76.Bl -tag -width indent 77.It Va hw.usb.cdceem.debug 78Verbosity level for log messages from the 79.Nm 80driver. 81Set to 0 to disable logging or 1 to warn about potential problems. 82Larger values enable debugging output. 83Defaults to 1. 84.It Va hw.usb.cdceem.send_echoes 85If set to 1, the driver will send an Echo EEM packet when the 86interface is brought up. 87While responding to Echo is mandatory, some devices cannot handle it. 88Only use for debugging. 89Defaults to 0. 90.It Va hw.usb.cdceem.send_fake_crc 91If set to 1, the driver will use 0xdeadbeef as the CRC value 92for outgoing Data EEM packets. 93Only use for debugging. 94Defaults to 0. 95.El 96.Sh SEE ALSO 97.Xr arp 4 , 98.Xr cdce 4 , 99.Xr intro 4 , 100.Xr ipheth 4 , 101.Xr netintro 4 , 102.Xr urndis 4 , 103.Xr usb 4 , 104.Xr usb_template 4 , 105.Xr ifconfig 8 106.Rs 107.%T "Universal Serial Bus Communications Class Subclass Specification for Ethernet Emulation Model Devices" 108.%U https://usb.org/sites/default/files/CDC_EEM10.pdf 109.Re 110.Sh HISTORY 111The 112.Nm 113device driver first appeared in 114.Fx 12.1 . 115.Sh AUTHORS 116The 117.Nm 118driver was written by 119.An Edward Tomasz Napierala Aq Mt trasz@FreeBSD.org 120under sponsorship from Hewlett Packard Enterprise. 121