Munin plugin to probe TCP and UDP ports

munin-plugin.nc_port

#!/bin/bash

: << =cut

=head1 NAME

nc_port - Plugin to monitor TCP/UDP port connectivity

=head1 CONFIGURATION

The following environment variables are used by this plugin

 nc             - Netcat program to use
 nc_args        - Arguments to nc (default "-z")
 host           - Hosts and ports to connect to

=head2 CONFIGURATION EXAMPLES

The following configuration can be used to probe www.google.com
on TCP port 80 (http) and Google's 8.8.8.8 on UDP port 53 (dns):

 [nc_port]
  env.host      www.google.com:80

 [nc_port_udp]
  env.host      8.8.8.8:53
  env.critical  1:1

=head1 AUTHOR

Copyright (C) 2019 Daniel Rudolf

=head1 LICENSE

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 dated June, 1991.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

=head1 MAGIC MARKERS

 #%# family=manual

=cut

. "$MUNIN_LIBDIR/plugins/plugin.sh"

BASENAME="$(basename "$0")"

NC="${nc:-nc}"
NC_ARGS="${nc_args:--z}"

if [[ "$BASENAME" == nc_port_udp* ]]; then
    BASENAME="${BASENAME:11}"
    NC_ARGS+=" -u"
elif [[ "$BASENAME" == nc_port* ]]; then
    BASENAME="${BASENAME:7}"
fi

FILE_HOST=""
if [[ "$BASENAME" == _* ]]; then
    FILE_HOST="${BASENAME:1}"
fi

HOST="${host:-${FILE_HOST:-example.com}}"

if [ "$1" == "autoconf" ]; then
    echo "yes"
    exit 0
fi

PROTOCOL="TCP"
if [[ "$NC_ARGS" =~ (^| )\-[a-zA-Z0-9]*u[a-zA-Z0-9]*( |$) ]]; then
    PROTOCOL="UDP"
fi

IFS=' '
for ARG in $HOST; do
    if ! [[ "$HOST" =~ :[0-9]+$ ]]; then
        if [ "$PROTOCOL" == "UDP" ]; then
            HOST="$HOST:53"
        else
            HOST="$HOST:80"
        fi
    fi
done

if [ "$1" == "config" ]; then
    echo "graph_title $PROTOCOL port connectivity"
    echo "graph_args --lower-limit -0.2 --upper-limit 1.2"
    echo "graph_vlabel connectivity"
    echo "graph_category network"
    echo "graph_info This graph shows whether a daemon is listening on the given address or not."

    for ARG in $HOST; do
        LABEL="$(clean_fieldname "$ARG")"
        echo "${LABEL}.label $ARG"
        echo "${LABEL}.info Daemon is (value 1) or is not (value 0) listening on $ARG"
        print_warning "$LABEL"
        print_critical "$LABEL"
    done
    exit 0
fi

for ARG in $HOST; do
    LABEL="$(clean_fieldname "$ARG")"
    if "$NC" $NC_ARGS "$(echo "$ARG" | cut -d ':' -f 1)" "$(echo "$ARG" | cut -d ':' -f 2)" 2>&1 > /dev/null; then
        echo "${LABEL}.value 1"
    else
        echo "${LABEL}.value 0"
    fi
done