Steam Deck USB Ethernet

usb-ether.sh

#!/bin/sh

if [ "$UID" -ne 0 ]; then
	echo "This script needs to be executed as root"
	exit 1
fi

vendor_id="0x3000" # Valve
product_id="0x28DE"
serial_number="$(dmidecode -s system-serial-number)" # The Steam Deck's serial number
manufacturer="Valve" # Manufacturer
product="Steam Deck" # Product
device="0x1004" # Device version
usb_version="0x0200" # USB 2.0
device_class="2" # Communications
cfg1="CDC" # Config 1 description
cfg2="RNDIS" # Config 2 description
power=250 # Max power
dev_mac1="42:61:64:55:53:42"
host_mac1="48:6f:73:74:50:43"
dev_mac2="42:61:64:55:53:44"
host_mac2="48:6f:73:74:50:45"
ms_vendor_code="0xcd" # Microsoft
ms_qw_sign="MSFT100" # Microsoft
ms_compat_id="RNDIS" # Matches Windows RNDIS drivers
ms_subcompat_id="5162001" # Matches Windows RNDIS 6.0 driver

cdc_mode="ecm" # Which CDC gadget to use
start_rndis=true # Whether to start the Microsoft RNDIS gadget

while getopts "ncerR" option ${@:2}; do
	case "${option}" in
		"n")
			cdc_mode=ncm
			;;
		"c")
			cdc_mode=ecm
			;;
		"e")
			cdc_mode=eem
			;;
		"r")
			start_rndis=true
			;;
		"R")
			start_rndis=false
			;;
	esac
done

case "$1" in
	start)
		# Create the networkd config file for the USB interface
		cat << EOF > /etc/systemd/network/usb0.network
[Match]
Name=usb0

[Network]
Address=192.168.100.1/24
DHCPServer=true
IPMasquerade=ipv4

[DHCPServer]
PoolOffset=100
PoolSize=20
EmitDNS=yes
DNS=8.8.8.8
EOF

		cat << EOF > /etc/systemd/network/usb1.network
[Match]
Name=usb1

[Network]
Address=192.168.101.1/24
DHCPServer=true
IPMasquerade=ipv4

[DHCPServer]
PoolOffset=100
PoolSize=20
EmitDNS=yes
DNS=8.8.8.8
EOF

		# Start networkd and iptables
		systemctl start systemd-networkd
		systemctl start iptables
		
		# Enable DRD driver
		echo -n "0000:04:00.3" > /sys/bus/pci/drivers/xhci_hcd/unbind
		echo -n "0000:04:00.3" > /sys/bus/pci/drivers/dwc3-pci/bind

		# Load the drivers
		modprobe libcomposite

		# Create the gadget
		mkdir /sys/kernel/config/usb_gadget/g.1
		cd /sys/kernel/config/usb_gadget/g.1

		# Specify the vendor and product ID
		echo "${vendor_id}" > idVendor
		echo "${product_id}" > idProduct

		# Create the gadget configuration
		mkdir configs/c.1

		# Create the strings directories
		mkdir strings/0x409
		mkdir configs/c.1/strings/0x409

		# Specify the serial number, manufacturer, and product strings
		echo "${serial_number}" > strings/0x409/serialnumber
		echo "${manufacturer}" > strings/0x409/manufacturer
		echo "${product}" > strings/0x409/product

		# Specify the device version, USB specification, and device class
		echo "${device}" > bcdDevice
		echo "${usb_version}" > bcdUSB
		echo "${device_class}" > bDeviceClass

		# Set the configuration description and power
		echo "${cfg1}" > configs/c.1/strings/0x409/configuration
		echo "${power}" > configs/c.1/MaxPower

		# Create the gadget function
		mkdir functions/${cdc_mode}.0

		# Set the MAC addresses of the gadget
		echo "${host_mac1}" > functions/${cdc_mode}.0/host_addr
		echo "${dev_mac1}" > functions/${cdc_mode}.0/dev_addr

		# Start RNDIS if enabled
		if [ "${start_rndis}" = true ]; then
			# Create the gadget configuration
			mkdir configs/c.2

			# Create the strings directories
			mkdir configs/c.2/strings/0x409

			# Specify the configuration description and power
			echo "${cfg2}" > configs/c.2/strings/0x409/configuration
			echo "${power}" > configs/c.2/MaxPower

			# Set some Microsoft specific configuration
			echo "1" > os_desc/use
			echo "${ms_vendor_code}" > os_desc/b_vendor_code
			echo "${ms_qw_sign}" > os_desc/qw_sign

			# Create the gadget function
			mkdir functions/rndis.0

			# Set the MAC addresses of the gadget
			echo "${host_mac2}" > functions/rndis.0/host_addr
			echo "${dev_mac2}" > functions/rndis.0/dev_addr

			# Set the RNDIS driver version
			echo "${ms_compat_id}" > functions/rndis.0/os_desc/interface.rndis/compatible_id
			echo "${ms_subcompat_id}" > functions/rndis.0/os_desc/interface.rndis/sub_compatible_id
		fi

		# Associate the CDC function with its configuration
		ln -s functions/${cdc_mode}.0 configs/c.1/

		# Associate the RNDIS function with its configuration
		if [ "${start_rndis}" = true ]; then
			ln -s functions/rndis.0 configs/c.2
			ln -s configs/c.2 os_desc
		fi
		
		# Enable NAT for both networks
		iptables -t nat -A POSTROUTING -s 192.168.100.0/24 -o wlan0 -j MASQUERADE
		iptables -t nat -A POSTROUTING -s 192.168.101.0/24 -o wlan0 -j MASQUERADE

		# Enable the gadget
		ls /sys/class/udc > UDC
		;;

	stop)
		# Disable the gadget
		cd /sys/kernel/config/usb_gadget/g.1
		echo "" > UDC
		
		# Disable NAT for both networks
		iptables -t nat -D POSTROUTING -s 192.168.100.0/24 -o wlan0 -j MASQUERADE
		iptables -t nat -D POSTROUTING -s 192.168.101.0/24 -o wlan0 -j MASQUERADE

		# Remove functions from the configuration
		rm configs/c.1/ncm.0 2> /dev/null
		rm configs/c.1/ecm.0 2> /dev/null
		rm configs/c.1/eem.0 2> /dev/null
		rm configs/c.2/rndis.0 2> /dev/null

		# Remove the strings directories in configurations
		rmdir configs/c.1/strings/0x409
		rmdir configs/c.2/strings/0x409 2> /dev/null

		# Remove the configurations
		rmdir configs/c.1
		rm os_desc/c.2 2> /dev/null
		rmdir configs/c.2 2> /dev/null

		# Remove the functions
		rmdir functions/ncm.0 2> /dev/null
		rmdir functions/ecm.0 2> /dev/null
		rmdir functions/eem.0 2> /dev/null
		rmdir functions/rndis.0 2> /dev/null

		# Remove the strings directories in the gadget
		rmdir strings/0x409

		# Delete the gadget
		cd ..
		rmdir g.1

		# Unload the drivers
		cd ../../
		modprobe -r usb_f_ncm
		modprobe -r usb_f_ecm
		modprobe -r usb_f_eem
		modprobe -r usb_f_rndis
		modprobe -r libcomposite
		
		
		# Disable DRD driver
		echo -n "0000:04:00.3" > /sys/bus/pci/drivers/dwc3-pci/unbind
		echo -n "0000:04:00.3" > /sys/bus/pci/drivers/xhci_hcd/bind

		# Stop networkd
		systemctl stop systemd-networkd 2> /dev/null

		# Remove the networkd config files for USB interfaces
		rm /etc/systemd/network/usb0.network
		rm /etc/systemd/network/usb1.network
		;;
	*)
		echo "Usage:"
		echo -e "\t./usb-ether.sh start\tStarts the USB ethernet"
		echo -e "\t\t-n\tUse the CDC-NCM USB Ethernet driver (for OSX and iOS)"
		echo -e "\t\t-c\tUse the CDC-ECM USB Ethernet driver (default)"
		echo -e "\t\t-e\tUse the CDC-EEM USB Ethernet driver"
		echo -e "\t\t-r\tEnable the RNDIS USB Ethernet driver for Windows (default)"
		echo -e "\t\t-R\tDisable the RNDIS USB Ethernet driver for Windows"
		echo -e "\t./usb-ether.sh stop - Stops the USB ethernet"
		;;
esac

Using Dafta's ip and gateway, this now works perfectly! Thanks both. Not sure why DHCP isn't working, but manual IP is more than fine.

I get a single error on line 90, given the replies above, I commented both line 90 and line 91 out but this meant that windows wouldnt even see the Ethernet device at all.

The error doesn't matter, leave the two lines uncommented.

Oh this is supposed to be doing DHCP... Weird.

It definitely should be.

IP: 192.168.100.100 (or above anything not below 100)
Gateway: 192.168.100.1

This is wrong, for Windows it should be:

IP: 192.168.101.100 (or above) Gateway: 192.168.101.1

Windows uses the RNDIS gadget which uses the 192.168.101.0/24 subnet, instead of the CDC-ECM which used the 192.168.100.0/24 subnet.

What defines the different subnet? The script only mentions .100. Is this just automatically generated? 😕

Honestly, I have no clue lol. I tried figuring it out but it's been a long time since I wrote this and I just don't remember anymore lol.

DHCP should work now. @imnotsurewhatyouwantfromme You can try with this updated script and won't need to manually set IP.