CDCE(4)

📦 version 15.1, in freebsd 14.5, freebsd 15.1

🎀 CDCE(4) — USB Communication Device Class Ethernet (ECM/NCM) driver, from the Kernel Interfaces Manual 🎀

okay bestie, this is the cdce page and it's literally the USB bridge driver moment. 💅

✨ NAME ✨

cdce — USB Communication Device Class Ethernet (ECM/NCM) driver. She's giving bridge-queen realness, no cap. 🦋

🦋 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 additionally 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. Noted, bestie — no extra media-type side quests here. 💀

🔥 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 devices

👑 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. (Yes, Wwhere — we keep the typo. It's part of the lore. 😭)

💖 DIAGNOSTICS 💖

  • 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

🌈 SEE ALSO 🌈

⭐ 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.

This is the part where you side-eye the USB device. 🙈

This is the Debian build, dated December 23, 2025 — CDCE(4), signing off. 💅✨

📦 where this page comes from