#!/bin/bash
#
# smtp_hello_ - munin plugin for measuring smtp hello response
# Copyright (C) 2008 Marek Mahut <mmahut@fedoraproject.org>
# Copyright (C) 2022 Andreas Perhab, WT-IO-IT GmbH <a.perhab@wtioit.at>
#
# Usage:
#   ln -s /usr/share/munin/plugins/smtp_hello_ /etc/munin/plugins/smtp_hello_mysmtpserver.example.com
#
# Environment variables (optional):
#   SMTP_PORT: port number to use for connection, default is 25
#   SMTP_COMMAND: command to use to test the connection, default is "HELO localhost"
#   TIMEOUT_SECONDS: seconds to take at most for the test, default is 120
#
#
# 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; either version 2
# of the License, or (at your option) any later version.
#
# 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.
#
#$log$
#Revision 2.0  2022/05/03 09:15:32 Andreas Perhab (ap-wtioit)
#Improve compatiblity.
#
#%# family=auto
#%# capabilities=autoconf

. "$MUNIN_LIBDIR/plugins/plugin.sh"

if [ "${MUNIN_DEBUG:-0}" == "1" ]; then
  set -x
fi

SMTP_COMMAND=${SMTP_COMMAND:-HELO localhost}
SMTP_PORT=${SMTP_PORT:-25}
TIMEOUT_SECONDS=${TIMEOUT_SECONDS:-120}
# if we have curl all non-zero exit codes indicate an error
status_warning=${status_warning:-0:0}
# default warning time begins at half the timeout
host_warning=${host_warning:-:$((TIMEOUT_SECONDS/2))}
# default when we get values bigger than 99% of timeout we mark the value as critical
host_critical=${host_critical:-:$((TIMEOUT_SECONDS * 99 / 100))}

host=$(basename "$0" | sed 's/^smtp_hello_//g')

time_executable=""
if which time >/dev/null; then
  # use time executable found in PATH
  time_executable=$(which time)
elif [ -x /usr/bin/time ] ; then
  # use time executable found in /usr/bin
  time_executable="/usr/bin/time"
fi
if [ "$time_executable" != "" ] ; then
  function take_the_time() {
    "$time_executable" -f "%e" "$@" 2>&1 | tail -n 1
    return "${PIPESTATUS[0]}"
  }
elif { time echo; } >/dev/null 2>&1; then
  # if we cannot find time executable but time keyword is successful we use the keyword
  function take_the_time() {
    # we use LC_ALL=C to force . as decimal separator on systems where LC_ is set to a language that uses ,
    # to limit the effect of LC_ALL=C and TIMEFORMAT, as well as to be able to redirect stderr of the time keyword
    # we use a subshell here
    (
      TIMEFORMAT='%R'
      LC_ALL=C
      time "$@" 1>/dev/null
    ) 2>&1
    return $?
  }
fi

nc_executable=""
if which nc >/dev/null ; then
  # use nc from PATH
  nc_executable=$(which nc)
elif [ -x /usr/bin/nc ] ; then
  # as fallback use /usr/bin/nc if found
  nc_executable="/usr/bin/nc"
fi

if which curl >/dev/null && curl_version_info=$(curl --version) && [[ "$curl_version_info" == *" smtp "* ]]; then
  curl_with_smtp_support=1
fi

if [ "$1" == "config" ]; then

  echo "graph_title smtp response time"
  echo "graph_vlabel response in sec"
  echo "graph_period minute"
  echo "graph_category network"
  echo "graph_args --base 1000 --lower-limit 0"
  echo "host.label $host"
  print_warning "host"
  print_critical "host"
  if [ "$curl_with_smtp_support" == "1" ] ; then
    echo "status.label $host smtp success"
    print_warning "status"
    print_critical "status"
  fi

elif [ "$1" == "autoconf" ]; then

  if [ "$take_the_time" != "" ] && [ -x "$nc_executable" ]; then
    echo "yes"
  else
    echo "no (/usr/bin/time or /usr/bin/nc missing)"
  fi
  exit 0

else
  if [ "$curl_with_smtp_support" == "1" ] ; then
    value=$(take_the_time curl --silent -X "$SMTP_COMMAND" --max-time "$TIMEOUT_SECONDS" "smtp://$host:$SMTP_PORT/")
    status=$?
  else
    # Note: "HELO localhost" only works if the SMTP server terminates the connection when presenting the HELO line
    # if you have troubles here, try installing curl (with smtp support), and we will use a proper smtp client
    # implementation. alternatively you can also set the SMTP_COMMAND environment variable to QUIT
    value=$(echo "$SMTP_COMMAND" | take_the_time "$nc_executable" -C -w "$TIMEOUT_SECONDS" "$host" "$SMTP_PORT")
    # with the simple echo command we would need to check a lot of conditions to determine a successful status
    # if you want this feature, install curl instead
    status=""
  fi
  echo "host.value $value"
  if [ -n "$status" ] ; then
    echo "status.value $status"
  fi
fi