check_dns.sh: redisign of the whole script.

check_dns.sh

@@ -5,6 +5,8 @@ if [[ -f "/usr/sbin/named" ]] ; then
 	check_string_ps="/usr/sbin/named"
 fi
 
+check_file="/tmp/dns-check-failed"
+
 alternate_addr="oopen.de google.com heise.de debian.org ubuntu.com"
 
 
@@ -18,7 +20,7 @@ fi
 # -
 service_name=bind9
 
-LOCK_DIR=`mktemp -d`
+LOCK_DIR="/tmp/$(basename $0).$$.LOCK"
 
 
 #---------------------------------------
@@ -27,6 +29,14 @@ LOCK_DIR=`mktemp -d`
 #-----------------------------
 #---------------------------------------
 
+clean_up() {
+
+   # Perform program exit housekeeping
+   rm -rf "$LOCK_DIR"
+   blank_line
+   exit $1
+}
+
 fatal(){
    echo ""
    if $terminal ; then
@@ -85,16 +95,6 @@ ok (){
    echo ""
 }
 
-fatal(){
-   echo ""
-   echo -e "   [ Fatal ] $*"
-   echo ""
-   echo -e "\tScript terminated.."
-   echo ""
-   rm -rf $LOCK_DIR
-   exit 1
-}
-
 trim() {
     local var="$*"
     var="${var#"${var%%[![:space:]]*}"}"   # remove leading whitespace characters
@@ -102,22 +102,55 @@ trim() {
     echo -n "$var"
 }
 
+blank_line() {
+   if $terminal ; then
+      echo ""
+   fi
+}
 
-#---------------------------------------
-#-----------------------------
-# Check some prerequisites
-#-----------------------------
-#---------------------------------------
 
-# - Running in a terminal?
+## - Test of valid IPv4 Address
+## -
+## -    Returns 0 if valid, > 0 otherwise
+## -
+is_valid_ipv4() {
+  local -a octets=( ${1//\./ } )
+  local RETURNVALUE=0
+
+  # return an error if the IP doesn't have exactly 4 octets
+  [[ ${#octets[@]} -ne 4 ]] && return 1
+
+  for octet in ${octets[@]}
+  do
+    if [[ ${octet} =~ ^[0-9]{1,3}$ ]]
+    then # shift number by 8 bits, anything larger than 255 will be > 0
+      ((RETURNVALUE += octet>>8 ))
+    else # octet wasn't numeric, return error
+      return 1
+    fi
+  done
+  return ${RETURNVALUE}
+}
+
+
+# ----------
+# - Jobhandling
+# ----------
+
+# - Run 'clean_up' for signals SIGHUP SIGINT SIGTERM
 # -
-if [[ -t 1 ]] ; then
-   terminal=true
-   LOGGING=true
-else
-   terminal=false
-   LOGGING=false
-fi
+trap clean_up SIGHUP SIGINT SIGTERM
+
+# - Create lock directory '$LOCK_DIR"
+#
+mkdir "$LOCK_DIR"
+
+
+
+# ----------
+# - Some checks
+# ----------
+
 
 # - Running in a terminal?
 # -
@@ -159,24 +192,47 @@ if $LOGGING ; then
    echo -e "   ======================================"
 fi
 
-for ip_addr in $alternate_addr  ; do
-   ping -c3 $ip_addr >> /dev/null 2>&1
-   if [ $? -eq 0 ]; then
+for host in $alternate_addr  ; do
 
-      PID=$(ps -e f | grep -E "[[:digit:]]\ ${check_string_ps}"| grep -v grep | awk '{print$2}')
-      if [[ "X${PID}" = "X" ]]; then
-         break
-      else
+   ip_addr="$(dig +short $host 2> /dev/null)"
 
+   #if [[ $? -eq 0 ]] && [[ -n "$ip_addr" ]] ; then 
+   if [[ $? -eq 0 ]] && is_valid_ipv4 $ip_addr ; then 
       if $LOGGING ; then
          ok "Bind Nameservice is up and running."
       fi
-         exit 0
+      if [[ -f "$check_file" ]]; then
+         rm -f "$check_file" > /dev/null 2>&1
       fi
+      clean_up 0
    fi
+
 done;
 
-error "Bind Nameservice seems to be down! Trying to restart service now.."
+if [[ ! -f "$check_file" ]] ; then
+   touch /tmp/dns-check-failed
+   if $LOGGING ; then
+      warn "There was no correct answer from the 'bind' name service.
+
+             This time i will go on, but if next time the bind service still answers 
+             incorrect, i'll do something."
+   fi
+   clean_up 1
+fi
+
+PID=$(ps -e f | grep -E "[[:digit:]]\ ${check_string_ps}"| grep -v grep | awk '{print$2}')
+if [[ "X${PID}" = "X" ]]; then
+
+   error "Bind Nameservice seems to be down! Trying to restart service now.."
+
+else
+
+   error "A \"named\" process is running, but bind service did no answer in a correct way.
+
+             ** Probably you have a network problem **
+             
+             What the heck: I restart the bind9 service anyway - Maybe that will help."
+fi
 
 if $systemd_supported ; then
    $systemctl stop $service_name > /dev/null 2> ${LOCK_DIR}/err_msg.log
@@ -214,8 +270,10 @@ done
 
 if [[ "X${PID}" = "X" ]] ; then
    error "Restarting Bind Nameservice failed!"
+   clean_up 1
 else
    ok "Bind Nameservice is up and running."
 fi
 
-exit 0;
+   
+clean_up 0;