update-resolv-conf

#!/bin/bash
#
# Parses DHCP options from openvpn to update resolv.conf
# To use set as 'up' and 'down' script in your openvpn *.conf:
#  up /etc/openvpn/update-resolv-conf
#  down /etc/openvpn/update-resolv-conf
# To use the VPN DNS server for all domains (not only the VPN domains),
# add the public_dns flag to the script. (eg. when routing all traffic via vpn)
#
# Used snippets of resolvconf script by Thomas Hood <jdthood@yahoo.co.uk>
# and Chris Hanson
# Licensed under the GNU GPL.  See /usr/share/common-licenses/GPL.
#
# 05/2006 chlauber@bnc.ch
# 07/2013 dheidler@gmail.com
#
# Example envs set from openvpn:
# foreign_option_1='dhcp-option DNS 193.43.27.132'
# foreign_option_2='dhcp-option DNS 193.43.27.133'
# foreign_option_3='dhcp-option DOMAIN be.bnc.ch'
# foreign_option_4='dhcp-option DOMAIN vpn'
 
[ -x /usr/sbin/resolvconf ] || exit 0
 
case $script_type in
 
up)
   for optionname in ${!foreign_option_*} ; do
      option="${!optionname}"
      echo $option
      part1=$(echo "$option" | cut -d " " -f 1)
      if [ "$part1" == "dhcp-option" ] ; then
         part2=$(echo "$option" | cut -d " " -f 2)
         part3=$(echo "$option" | cut -d " " -f 3)
         if [ "$part2" == "DNS" ] ; then
            IF_DNS_NAMESERVERS="$IF_DNS_NAMESERVERS $part3"
         fi
         if [ "$part2" == "DOMAIN" ] ; then
            IF_DNS_SEARCH="$IF_DNS_SEARCH $part3"
         fi
      fi
   done
   R=""
   if [ "$IF_DNS_SEARCH" ] ; then
           R="${R}search $IF_DNS_SEARCH
"
   fi
   for NS in $IF_DNS_NAMESERVERS ; do
           R="${R}nameserver $NS
"
   done
   if [ "$1" == "public_dns" ] ; then
       private_flag=""
   else
       private_flag="-p"
   fi
   echo -n "$R" | /usr/sbin/resolvconf $private_flag -a "${dev}"
   ;;
down)
   /usr/sbin/resolvconf -d "${dev}"
   ;;
esac