#!/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.


# When the system boots, systemd-resolved seems to recreate /run/systemd/resolve,
# or something, because the bindmounts to that directory do not always exist
# for units starting up at the same time. Anyways, removing and creating that
# directory definitely has the effect of deleting the bindmount, so
# here I solve for that ever happening.

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\" exit status: $?, PIPESTATUS: ${PIPESTATUS[*]}" >&2' ERR

if (( $# == 0 )); then
  echo error: expected service argument >&2
  exit 1
fi

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

sleep 5
while true; do
  sleep 20
  for unit; do
    pid=$(systemctl show --property MainPID --value $unit 2>/dev/null ||:)
    case $pid in
      [1-9]*)
        if ! nsenter -t $pid -m timeout 20 mountpoint /run/systemd/resolve &>/dev/null; then
          echo mail bind restart of $unit
          timeout 60 systemctl restart $unit ||:
        fi
        ;;
    esac
  done
done