How to use USB device networking
The Linux USB gadget sub-system supports USB device functionality, including USB networking.
Configure hardware for USB OTG or USB device support
Depending on your hardware, you can use either USB OTG or USB device to enable support for USB networking.
Build USB Ethernet network gadget driver
The USB Ethernet network gadget driver caused the device to appear to be a USB network dongle when connected to a host computer. Generally it is best to build USB gadget drivers as modules instead of building them into the kernel so you can unload one and load another.
Symbol: USB_ETH [=m]
Prompt: Ethernet Gadget (with CDC Ethernet support)
Defined at drivers/usb/gadget/Kconfig:628
Depends on: <choice> && NET
Location:
-> Kernel configuration
-> Device Drivers
-> USB support (USB_SUPPORT [=y])
-> USB Gadget Support (USB_GADGET [=y])
-> USB Gadget Drivers (<choice> [=m])
Build and install the kernel to the target hardware.
Load USB Ethernet network gadget driver
After booting the target hardware to a shell prompt, run:
modprobe g_ether
and you should see output similar to:
g_ether gadget: using random self ethernet address g_ether gadget: using random host ethernet address usb0: MAC be:b5:85:ef:48:33 usb0: HOST MAC 1a:b2:c3:43:8a:6e g_ether gadget: Ethernet Gadget, version: Memorial Day 2008 g_ether gadget: g_ether ready
You can then verify the usb0 network interface exists:
ifconfig usb0
with output similar to:
usb0 Link encap:Ethernet HWaddr BE:B5:85:EF:48:33
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Connect device to host PC
Before connecting the target device to the host PC, watch the syslog, by running the following command on the host PC:
sudo tail -f /var/log/messages
Connect the USB cable between the target device and the host PC. The messages file on the host PC should indicate the new USB device was detected.
Jun 6 10:15:29 contra-lx kernel: [1638241.377831] usb 1-4.4.2: new high speed USB device using ehci_hcd and address 47 Jun 6 10:15:29 contra-lx kernel: [1638241.510787] cdc_subset: probe of 1-4.4.2:1.0 failed with error -22 Jun 6 10:15:29 contra-lx kernel: [1638241.513437] cdc_subset 1-4.4.2:1.1: usb0: register 'cdc_subset' at usb-0000:00:02.1-4.4.2, Linux Device, 82:13:56:20:b4:cb Jun 6 10:15:29 contra-lx kernel: [1638241.513490] usbcore: registered new interface driver cdc_subset Jun 6 10:15:29 contra-lx kernel: [1638241.533442] cdc_ether: probe of 1-4.4.2:1.0 failed with error -16 Jun 6 10:15:29 contra-lx kernel: [1638241.533619] usbcore: registered new interface driver cdc_ether
On the host you can verify the new usb0 interface exists by running:
ifconfig usb0
with the output being similar to:
usb0 Link encap:Ethernet HWaddr 82:13:56:20:b4:cb
inet6 addr: fe80::8013:56ff:fe20:b4cb/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:78 (78.0 B)
When you connect the cable, in the target device console, you should see:
g_ether gadget: high speed config #1: CDC Ethernet (ECM)
Assigning IP addresses
For this simple example, fixed IP addresses are assigned to the both the host PC USB network interface and the target device USB network interface.
On the host
HOST_USB_IP=10.0.1.1 sudo ifconfig usb0 $HOST_USB_IP netmask 255.255.255.0 route
On the target device
TARGET_USB_IP=10.0.1.2 ifconfig usb0 $TARGET_USB_IP netmask 255.255.255.0 route
with the route showing the default gateway is
Verifying network connectivity
On the target device, ping the host PC:
ping 10.0.1.1 -c 5
On the host PC, verify the number of packet sent and received is not zero
ifconfig usb0
Look at the values of RX packets: and TX packets:87.
Bridging host PC to allow device to reach the Internet
If your host PC is connected to the Internet (through WiFi or Ethernet), then you can allow the target device to share the host PC's Internet connection.