Re: [Openvpn-users] Linux client not taking DNS from open VPN server

[Jan J. K. <ja...@ni...>]

Mr Gabriel Ogunleye wrote:
> My linux client does not use the DNS pushed to it from my openvpn server, but my windows client does. Any reason why the linux one works differently, I was about to roll out a linux desktop to my technical staff, but I am wondering if they will have to manually add the DNS server each time they connect. 
>   
Hi Gabriel,

there are quite a few "push" and DHCP settings that are not 
automatically picked up by Linux clients. It is , however, quite easy to 
add a script that parses these settings and makes the appropriate 
changes to the config files. I use an 'update-dns' bash script to update 
the /etc/resolv.conf file whenever I connect to one of my OpenVPN 
servers. Add these lines to your client config files
  up   /etc/openvpn/update-dns
  down /etc/openvpn/update-dns
and here's the script:

#!/bin/bash

if [ "$script_type" = "up" ]
then
  # cycle through foreign_option_{n} to scan for DNS servers
  n=1
  keep_going=1
  dns_list=""
  while [ $keep_going -eq 1  -a $n -lt 99 ]
  do
    eval option=\$foreign_option_$n
    if [ -n "$option" ]
    then
      # now look for "dhcp-option DNS"
      dns_server=${option#dhcp-option DNS }
      if [ ! "${option}" = "$dns_server" ]
      then
        # found one!
        echo "  $0: DHCP pushed us nameserver $dns_server"
        dns_list="$dns_list\nnameserver $dns_server"
      fi
    else
        keep_going=0
    fi
    let n=n+1
  done

  # now update the list of nameservers in /etc/resolv.conf
  if [ -n "$dns_list" ]
  then
    echo "  $0: Adding nameservers to /etc/resolv.conf"
    mv /etc/resolv.conf /etc/resolv.conf.pre-openvpn
    sed "s/^nameserver .*/$dns_list\n&/" /etc/resolv.conf.pre-openvpn > 
/etc/resolv.conf
  fi
elif [ "$script_type" = "down" ]
then
  if [ -r /etc/resolv.conf.pre-openvpn ]
  then
    echo "  $0: Restoring original /etc/resolv.conf"
    mv /etc/resolv.conf.pre-openvpn /etc/resolv.conf
  fi
fi


HTH,

JJK