#!/bin/bash
# I, Ian Kelling, follow the GNU license recommendations at
# https://www.gnu.org/licenses/license-recommendations.en.html. They
# recommend that small programs, < 300 lines, be licensed under the
# Apache License 2.0. This file contains or is part of one or more small
# programs. If a small program grows beyond 300 lines, I plan to switch
# its license to GPL.

# Copyright 2024 Ian Kelling

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

if ! test "$BASH_VERSION"; then echo "error: shell is not bash" >&2; exit 1; fi
shopt -s inherit_errexit 2>/dev/null ||: # ignore fail in bash < 4.4
set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

[[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"


shopt -s nullglob

# we already configured the interface once, afterwards, comment and
# uncomment to enable/disable. This makes it so we don't depend on /p
# being mounted.

if [[ -s /etc/network/interfaces.d/ethusb ]]; then
  sed -i --follow-symlinks 's/^#//' /etc/network/interfaces.d/ethusb
  exit 0
fi


while read -r ip host mac; do
  if [[ $mac != usb ]]; then
    continue
  fi
  if [[ $host = ${HOSTNAME}c ]]; then
    usbip=$ip
    break
  fi
done </p/c/host-info

if [[ ! $usbip ]]; then
  exit 0
fi

ethx=0

# device that has an eth0, but we aren't using it because it is
# broken. We could just hardcode a mac comparison with `cat
# /sys/class/net/eth0/address` but this is cooler.
if [[ -e  /sys/class/net/eth0 ]]; then
  bus_info=$(ethtool -i eth0 | awk '$1 == "bus-info:" { print $2 }')
  if [[ $bus_info != usb* ]]; then
    ethx=1
  fi
fi

cat >/etc/network/interfaces.d/ethusb <<EOF
auto eth$ethx
iface eth$ethx inet static
  address 10.2.0.$ip/16
  gateway 10.2.0.1
EOF