zabbix_mailflow

#!/bin/bash
#
# Zabbix agent extension for monitoring SMTP flows

BUFFER=/tmp/zabbix-mailflow
CFG=/etc/zabbix/zabbix-mailflow.conf
AWKSCRIPT=/etc/zabbix/zabbix_mailflow_getheader.awk
SOFTWARE="awk fetchmail jo ssh"

source $CFG

function discover_mailflow() {
    jo -p data=$( jo -a $(
      for ((i=0; i<$LAST_RELAY; i++))
      do
         jo {\#RELAY}=${RELAY[i]}
      done
      ) )
}

function send_mail() {
    mkdir -p $BUFFER; chmod 750 $BUFFER
    cd $BUFFER

    NOW=$(date +%s)
    ssh $MAILCLIENT "echo 'This message is intended for Zabbix.' | mail -s $NOW $EMAILADDR"
    echo $NOW >> sent.log

    # clean up old messages
    for mail in $(head -n-$(($MAILCOUNT * 3)) sent.log)
    do
       rm -f $mail
    done

    tail -n $(($MAILCOUNT * 3)) sent.log > sent.log.tmp
    mv sent.log.tmp sent.log

    # also check for unreceived mail, it has no use to put this in a seperate function, as this function already runs each minute
    fetchmail

}

function process_mail() {
    cd $BUFFER || exit 1

    while IFS=- read timestamp index
    do
       [[ $index -le $LAST_RELAY ]] && MAILSTATS="${MAILSTATS}${RELAY[$index]}:$timestamp\n"
       [[ $index -eq $SUBJECT ]] && MAILID=$timestamp
    done <<< $(awk -v first_relay="$FIRST_RELAY" -v last_relay="$LAST_RELAY" -f $AWKSCRIPT /dev/stdin)

    echo -e $MAILSTATS > $MAILID
}

function getmaster() {
   cd $BUFFER || exit 1

   # skip the last message, to prevent false positives
   MAILS=$(tail -n $MAILCOUNT $BUFFER/sent.log | head -n-1)
   MISSED=0
   declare -a RELAY_SUM

   # gather sum delay for all relay for all mails checked
   for mail in $MAILS
   do
      test -f $mail || {
         let "MISSED++"
         continue
      }

      for ((i=$FIRST_RELAY; i<$LAST_RELAY; i++))
      do
         DELAY=$(grep ${RELAY[i]} $mail | cut -d: -f2)
         test -z $DELAY && continue
         RELAY_SUM[i]=$((${RELAY_SUM[i]} + $DELAY))
      done
   done

   # calculate the average delay for each relay
   for ((i=$FIRST_RELAY; i<$LAST_RELAY; i++))
   do
      echo ${RELAY[i]}:$((${RELAY_SUM[i]} / $(( $MAILCOUNT - $MISSED)) ))
   done
   echo missing:$MISSED
}

function sanity_check() {
   ok=1
   for prog in $SOFTWARE
   do
      which $prog > /dev/null || { echo "Missing program $prog."; ok=0; }
   done
   test -f $CONFIG || { echo "Missing configfile $CONFIG"; ok=0; }
   test $ok -ne 1 && { echo "Sanity check failed. Aboring." ; exit 1; }

   mkdir -p $BUFFER
}

sanity_check

action=$1
arg=$2

case "$action" in
    mailflow.discover)
        discover_mailflow
        ;;
    mailflow.master)
        getmaster
        ;;
    process_mail)
        process_mail
        ;;
    send_mail)
        send_mail
        ;;
esac