#!/bin/sh
# Handle USB networking and tethering with unudhcpd and NetworkManager
# without unbinding the USB gadget UDC on link up/down events.

con_uuid="83bd1823-feca-4c2b-9205-4b83dc792e1f"

[ -f /usr/share/misc/source_deviceinfo ] && . /usr/share/misc/source_deviceinfo
[ -e /etc/unudhcpd.conf ] && . /etc/unudhcpd.conf

usb_network_function="${deviceinfo_usb_network_function:-ncm.usb0}"
usb_network_function_fallback="rndis.usb0"
disable_dhcpd="${deviceinfo_disable_dhcpd:-false}"
host_ip="${unudhcpd_host_ip:-172.16.42.1}"
client_ip="${unudhcpd_client_ip:-172.16.42.2}"

CONFIGFS="/sys/kernel/config/usb_gadget"
if ! [ -d "$CONFIGFS" ]; then
  mount -t configfs configfs /sys/kernel/config 2>/dev/null || true
fi

ensure_gadget_bound() {
  udc_dev="$(ls /sys/class/udc 2>/dev/null | head -n 1)"
  [ -n "$udc_dev" ] || return 0
  if [ -d "$CONFIGFS/g1" ]; then
    cur_udc="$(cat "$CONFIGFS/g1/UDC" 2>/dev/null | tr -d '[:space:]')"
    if [ -z "$cur_udc" ]; then
      echo "$udc_dev" > "$CONFIGFS/g1/UDC" 2>/dev/null || true
    fi
  fi
}

ensure_gadget_bound

interface="$(
  cat "$CONFIGFS/g1/functions/$usb_network_function/ifname" 2>/dev/null ||
  cat "$CONFIGFS/g1/functions/$usb_network_function_fallback/ifname" 2>/dev/null ||
  echo "usb0"
)"

if [ -n "$DEVICE_IFACE" ] && [ "$DEVICE_IFACE" != "$interface" ]; then
  exit 0
fi

ensure_usb_dhcp() {
  ip link set "$interface" up 2>/dev/null || true
  if ! ip -4 addr show dev "$interface" 2>/dev/null | grep -q "$host_ip"; then
    ip addr add "$host_ip/16" dev "$interface" 2>/dev/null || true
  fi
  if [ "$disable_dhcpd" != "true" ] && ! pidof unudhcpd >/dev/null 2>&1; then
    (unudhcpd -i "$interface" -s "$host_ip" -c "$client_ip" >/dev/null 2>&1) &
    logger -t nm-tethering "unudhcpd started on $interface ($host_ip -> $client_ip)"
  fi
}

case "${NM_DISPATCHER_ACTION:-up}" in
  up|down|reapply)
    ensure_gadget_bound
    ensure_usb_dhcp
    ;;
esac
exit 0