Adding ethernet libcomposite gadgets to bluetooth_2_usb

[xia0]

i needed to add an ethernet gadget to the raspberry pi so i could ssh into it without wifi but couldn't really find much documentation. not sure if it's the right way to do it as it doesn't use circuit python but here is my script. i have it set to run from /etc/rc.local. it needs to run in the background (add ampersand to end of command). it seems to be running fine on debian bookworm.

dnsmasq needs to be configured using the information on https://jon.sprig.gs/blog/post/2243 up to the bit where ip addresses are manually assigned. that's handled by the couple lines at the end of the script.

the script adds the configuration for the ethernet gadget before bluetooth_2_usb runs. it assigns 192.0.2.1 to the raspberry pi and uses dnsmasq to assign an ip to the host.

#!/bin/bash
# Based on a combination of: http://www.isticktoit.net/?p=1383
#   and: https://www.raspberrypi.org/forums/viewtopic.php?t=260107
#   and: https://gist.github.com/schlarpc/a327d4aa735f961555e02cbe45c11667/c80d8894da6c716fb93e5c8fea98899c9aab8d89
#   and: https://github.com/ev3dev/ev3-systemd/blob/02caecff9138d0f4dcfeb5afbee67a0bb689cec0/scripts/ev3-usb.sh
# source: https://jon.sprig.gs/blog/post/2243

configfs="/sys/kernel/config/usb_gadget"
this="${configfs}/adafruit-blinka"

# Configure values
serial="$(grep 'Serial' /proc/cpuinfo | head -n 1 | sed -E -e 's/^Serial\s+:\s+0000(.+)/\1/')"
model="$(grep 'Model' /proc/cpuinfo | head -n 1 | sed -E -e 's/^Model\s+:\s+(.+)/\1/')"
manufacturer="Raspberry Pi Foundation"

# The serial number ends in a mac-like address. Let's use this to build a MAC address.
#   The first binary xxxxxx10 octet "locally assigned, unicast" which means we can avoid
#   conflicts with other vendors.
mac_base="$(echo "${serial}" | sed 's/\(\w\w\)/:\1/g' | cut -b 4-)"
ecm_mac_address_dev="02${mac_base}"  # ECM/CDC address for the Pi end
ecm_mac_address_host="12${mac_base}" # ECM/CDC address for the "host" end that the Pi is plugged into
rndis_mac_address_dev="22${mac_base}"  # RNDIS address for the Pi end
rndis_mac_address_host="32${mac_base}" # RNDIS address for the "host" end that the Pi is plugged into

# Set up the ECM/CDC function
mkdir -p "${this}/functions/ecm.usb0"
echo "${ecm_mac_address_host}"     > "${this}/functions/ecm.usb0/host_addr"
echo "${ecm_mac_address_dev}"      > "${this}/functions/ecm.usb0/dev_addr"
mkdir -p "${this}/configs/c.1"
ln -s "${this}/functions/ecm.usb0"   "${this}/configs/c.1/"

mkdir -p "${this}/configs/c.2/strings/0x409"
echo "0xC0"                      > "${this}/configs/c.2/bmAttributes" # Self Powered
echo "250"                       > "${this}/configs/c.2/MaxPower"     # 250mA
mkdir -p "${this}/functions/rndis.usb0"
mkdir -p "${this}/functions/rndis.usb0/os_desc/interface.rndis"
echo "RNDIS"                       > "${this}/functions/rndis.usb0/os_desc/interface.rndis/compatible_id"
echo "5162001"                     > "${this}/functions/rndis.usb0/os_desc/interface.rndis/sub_compatible_id"
echo "${rndis_mac_address_host}"   > "${this}/functions/rndis.usb0/host_addr"
echo "${rndis_mac_address_dev}"    > "${this}/functions/rndis.usb0/dev_addr"
echo "RNDIS"                       > "${this}/configs/c.2/strings/0x409/configuration"
ln -s "${this}/configs/c.2"          "${this}/os_desc"
ln -s "${this}/functions/rndis.usb0" "${this}/configs/c.2/"

# wait until ethernet gadgets are configured before assigning IPs
while ! ls /sys/class/net/ | grep --quiet usb0
do
  sleep 1
done

# set ip addresses and start dhcp service to assign ip to host
ifconfig usb0 192.0.2.1 netmask 255.255.255.240 up
ifconfig usb1 192.0.2.17 netmask 255.255.255.240 up
systemctl start dnsmasq.service

exit 0

todo: replace ifconfig commands with ip

i used examples from the following sources:
https://jon.sprig.gs/blog/post/2243
https://forums.raspberrypi.com/viewtopic.php?t=306121