#!/bin/sh

# Copyright (c) 2013 Stefan Huber <shuber@sthu.org>
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use,
# copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following
# conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.

. $(dirname $0)/utils.sh


PROGNAME=$(basename $0)
REVISION="0.1"

usage() {

    cat <<EOF
check_rdns v$REVISION
Copyright (c) 2013 Stefan Huber <shuber@sthu.org>
    
Usage: $PROGNAME -H ip-address [OPTIONS]

Arguments:
    -H, --address IP-address    The ip-addres on which reverse-DNS is performed.

Options:
    -h, --help                  Print this text.
    -a, --expect=HOST           The expected result.
    -s, --server=HOST           The DNS server to contact.
    -t, --timeout=SEC           Seconds before lookup times out. (Default: 10)
    -w, --warning=MSEC          Return warning if lookup time exceeds value.
    -c, --critical=MSEC         Return critical if lookup time exceeds value.
    -V, --version               Print version info.
EOF
}


TEMP=`getopt -o "H:a:c:hs:t:w:V" --long "help,address:,expect:,critical:,server:,timeout:,warning:,version" -n "$PROGNAME" -- "$@"`
eval set - "$TEMP"

ADDRESS=
EXPECT=
SERVER=
TIMEOUT=10
WARNING=
CRITICAL=

while true; do
    case "$1" in
        -h | --help )
            usage
            exit $STATE_OK ;;
        -V | --version )
            echo "$PROGNAME v$REVISION"
            exit $STATE_OK ;;
        -H | --address )
            ADDRESS="$2"; shift 2 ;;
        -a | --expect )
            EXPECT="$2"; shift 2 ;;
        -s | --server )
            SERVER="$2"; shift 2 ;;
        -t | --timeout )
            TIMEOUT="$2"; shift 2 ;;
        -w | --warning )
            WARNING="$2"; shift 2 ;;
        -c | --critical )
            CRITICAL="$2"; shift 2 ;;
        -- )
            shift
            break ;;
        * )
            break ;;
    esac
done

if [ -z "$ADDRESS" ]; then
    echo "Error: No address given."
    usage
    exit $STATE_CRITICAL
fi

DIGOPTS="+time=$TIMEOUT +noquestion +noauthority -t PTR"
[ -z "$SERVER" ] || DIGOPTS="@$SERVER $DIGOPTS"

RESULT=$(dig $DIGOPTS -x "$ADDRESS"):
DIGSTATUS=$?

if [ $DIGSTATUS != "0" ]; then
    echo "DNS failed: dig exit code $DIGSTATUS |"
    exit $STATE_CRITICAL
fi

# Get the actual result
HOST=$(echo "$RESULT" | grep -m 1 -o "[[:space:]]IN[[:space:]]*PTR[[:space:]].*\.$" | awk '{ print $3 }' )
if [ -z "$HOST" ]; then
    echo "DNS failed: reverse DNS gave no answer. |"
    exit $STATE_CRITICAL
fi


# Get the query time in msec
QUERYTIME=$(echo "$RESULT" | grep -m 1 "Query time:" | cut -d ":" -f 2 | awk '{ print $1 }')


MATCHED=
if [ -n "$EXPECT" ]; then
    if [ "$EXPECT" != "$HOST" ]; then
        echo "DNS critical - query result \"$HOST\" != \"$EXPECT\", query time: $QUERYTIME msec |"
        exit $STATE_CRITICAL
    else
        MATCHED=" (match ok)"
    fi
fi

if [ -n "$CRITICAL" ] && [ "$QUERYTIME" -gt "$CRITICAL" ]; then
    echo "DNS critical - query time $QUERYTIME msec too large ($CRITICAL msec), query result: \"$HOST\"$MATCHED |"
    exit $STATE_CRITICAL
fi

if [ -n "$WARNING" ] && [ "$QUERYTIME" -gt "$WARNING" ]; then
    echo "DNS warning - query time $QUERYTIME msec too large ($WARNING msec), query result: \"$HOST\"$MATCHED |"
    exit $STATE_WARNING
fi

echo "DNS OK - query time $QUERYTIME msec, query result: \"$HOST\"$MATCHED |"
exit $STATE_OK