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CDCE(4) Kernel Interfaces Manual CDCE(4) NAME cdce -- USB Communication Device Class Ethernet (ECM/NCM) driver SYNOPSIS To compile this driver into the kernel, place the following lines in your kernel configuration file: device uhci device ohci device usb device miibus device uether device cdce Mobile Devices (e.g., Huawei E3372, E5573 and others) may need addi- tionally the u3g command port: device ucom device u3g Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5): if_cdce_load="YES" DESCRIPTION The cdce 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. 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 cdce driver does not support different media types or options. HARDWARE The cdce 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: • Android USB tethering • iPhone USB tethering • Prolific PL-2501 Host-to-Host Bridge Controller • Sharp Zaurus PDA • Terayon TJ-715 DOCSIS Cable Modem • Huawei 3G/4G LTE (e.g., E3372, E5573) and other mobile network de- vices EXAMPLES Mobile cdce Network Devices may need a connect command sequence via the u3g(4) serial command port before activating the NCM/ECM/ACM network interface. For example: echo 'AT^NDISUP=1,1,"internet"' > /dev/cuaU[0].0 Wwhere "internet" is your providers apn name. DIAGNOSTICS cdce%d: no union descriptor The driver could not fetch an interface descriptor from the USB device. For a manually added USB vendor/prod- uct, the CDCE_NO_UNION flag can be tried to work around the missing de- scriptor. 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 ven- dor/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 SEE ALSO arp(4), cdceem(4), intro(4), ipheth(4), netintro(4), u3g(4), ucom(4), urndis(4), usb(4), ifconfig(8) Universal Serial Bus Class Definitions for Communication Devices, http://www.usb.org/developers/devclass_docs/usbcdc11.pdf. Data sheet Prolific PL-2501 Host-to-Host Bridge/Network Controller, http://tech.prolific.com.tw/visitor/fcabdl.asp?fid=20679530. HISTORY The cdce device driver first appeared in OpenBSD 3.6, NetBSD 3.0 and FreeBSD 6.0. AUTHORS 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>. 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. FreeBSD ports 15.1 December 23, 2025 CDCE(4)
NAME | SYNOPSIS | DESCRIPTION | HARDWARE | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS
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