#!/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.


# usage: I run this script on a timer to correct the dns on wrt for
# clients where dns is updated dynamically by openvpn, in the case that
# openvpn crashes or the computer running openvpn crashes.

set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

x="$(readlink -f "$BASH_SOURCE")"; cd ${x%/*} # directory of this file

while read -r ip host; do
    found=false
    is_connected="grep -q "^CLIENT_LIST,$host," /run/openvpn-server/status-server.log"
    if $is_connected; then continue; fi
    if ! grep -q "^CLIENT_LIST,$host," /run/openvpn-server/status-server.log; then
        cd $(mktemp -d); dir=$PWD
        ssh wrt tar -C /etc -c hosts | tar -x
        if grep -qFx "$ip $host" hosts; then continue; fi
        # openvpn udpates its status file every 60 seconds by default
        if (( $(stat -c%Y hosts) > EPOCHSECONDS + 60 )); then
            sleep 60
            if $is_connected; then continue; fi
        fi
        ssh root@wrt.b8.nz cedit ovpn-$host <<<"$ip $host" || [[ $? == 1 ]]
    fi
done <lan-dns