#!/bin/sh
#		dns event handling script
#

RESOLV_CONF="/etc/resolv.conf"

usage() {
	echo "Usage: $0 {set/clean} dns..."
	exit 1
}

clean() {
  # clean /etc/resolv.conf 
  cat /dev/null > $RESOLV_CONF
}

show() {  
  cat $RESOLV_CONF
}
 
takelock()
{
   while [ -f "/tmp/dns_lock_fd" ]; do
   :
   echo "lock dns file now!"
   sleep 1;
   done
   echo 1 > "/tmp/dns_lock_fd"
} 

givelock()
{
   rm /tmp/dns_lock_fd
}


rmV4DNS(){
   cat /etc/resolv.conf | grep : > /var/dns6   
   cat /var/dns6 > /etc/resolv.conf
}
 
rmV6DNS(){
   cat /etc/resolv.conf | grep -v : > /var/dns4 
   cat /var/dns4 > /etc/resolv.conf
}

 
count=1
if [ $# \< $count ] ; then
	usage
fi


	  takelock;     
case "$1" in 
	
	set)	 
	
    rmV4DNS;
		i=2
		total=$#		
		while [ $i -le $total ];
		do
		  shift
		  dns=$1
		  echo "adding dns " $dns
		  echo nameserver "$dns" >> $RESOLV_CONF
		  i=`expr $i + 1`		   
		done		
		show
		;;		
		
	setv6)	 
	
    rmV6DNS;
		i=2
		total=$#		
		while [ $i -le $total ];
		do
		  shift
		  dns=$1
		  echo "adding dns " $dns
		  echo nameserver "$dns" >> $RESOLV_CONF
		  i=`expr $i + 1`		   
		done		
		show
		;;


  rmv4)
    rmV4DNS
   ;;
  rmv6)
    rmV6DNS
   ;; 
  
     
	clean)
		clean
		;;
		
	*)
		usage
	;;	
esac
  givelock;