NetworkManager is not changing /etc/resolv.conf after openvpn dns push

Question

I've got a problem which is "NetworkManager is not updating /etc/resolv.conf after openvpn connection with dns push configured".

Here's my openvpn server config: (I've changed domain name to ABC.COM for security reason ;))

########################################
# Sample OpenVPN config file for
# 2.0-style multi-client udp server
#
# Adapted from http://openvpn.sourceforge.net/20notes.html
#
# tun-style tunnel

port 1194
dev tun

# Use "local" to set the source address on multi-homed hosts
#local [IP address]

# TLS parms
tls-server 
ca keys/ca.crt
cert keys/static.crt
key keys/static.key
dh keys/dh1024.pem
proto tcp-server

# Tell OpenVPN to be a multi-client udp server
mode server

# The server's virtual endpoints
ifconfig 10.8.0.1 10.8.0.2

# Pool of /30 subnets to be allocated to clients.
# When a client connects, an --ifconfig command
# will be automatically generated and pushed back to
# the client.
ifconfig-pool 10.8.0.4 10.8.0.255

# Push route to client to bind it to our local
# virtual endpoint.
push "route 10.8.0.1 255.255.255.255"

push "dhcp-option DNS 10.8.0.1"

# Push any routes the client needs to get in
# to the local network.
#push "route 192.168.0.0 255.255.255.0"

# Push DHCP options to Windows clients.
push "dhcp-option DOMAIN ABC.COM"
#push "dhcp-option DNS 192.168.0.1"
#push "dhcp-option WINS 192.168.0.1"

# Client should attempt reconnection on link
# failure.
keepalive 10 60

# Delete client instances after some period
# of inactivity.
inactive 600

# Route the --ifconfig pool range into the
# OpenVPN server.
route 10.8.0.0 255.255.255.0

# The server doesn't need privileges
user openvpn
group openvpn

# Keep TUN devices and keys open across restarts.
persist-tun
persist-key

verb 4

As you can see it's basicaly sample config with little tuning.

Now..

On my machine (openvpn client), I can see that dns is ok:

{17:12}/etc/NetworkManager ➭ nslookup git.ABC.COM 10.8.0.1
Server:     10.8.0.1
Address:    10.8.0.1#53

Name:   git.ABC.COM
Address: 10.8.0.1

{17:18}/etc/NetworkManager ➭ nslookup ABC.COM 10.8.0.1   
Server:     10.8.0.1
Address:    10.8.0.1#53

Name:   ABC.COM
Address: 18X.XX.XX.71

openvpn logs on server side says (if I understand correctly) that DNS has been pushed:

openvpn[13257]: TCPv4_SERVER link remote: [AF_INET]83.30.135.214:37658
openvpn[13257]: 83.30.135.214:37658 TLS: Initial packet from [AF_INET]83.30.135.214:37658, sid=3251df51 915772f3
openvpn[13257]: 83.30.135.214:37658 VERIFY OK: depth=1, C=XX, ST=XX, L=XXX, O=XXX, OU=XXX, CN=XXX, name=XXX, emailAddress=mail@ABC.COM
openvpn[13257]: 83.30.135.214:37658 VERIFY OK: depth=0, C=XX, ST=XX, L=XXX, O=XXX, OU=XXX, CN=XXX, name=XXX, emailAddress=mail@ABC.COM
openvpn[13257]: 83.30.135.214:37658 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key
openvpn[13257]: 83.30.135.214:37658 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
openvpn[13257]: 83.30.135.214:37658 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key
openvpn[13257]: 83.30.135.214:37658 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
openvpn[13257]: 83.30.135.214:37658 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA
openvpn[13257]: 83.30.135.214:37658 [jacek] Peer Connection Initiated with [AF_INET]83.30.135.214:37658
openvpn[13257]: jacek/83.30.135.214:37658 MULTI_sva: pool returned IPv4=10.8.0.10, IPv6=(Not enabled)
openvpn[13257]: jacek/83.30.135.214:37658 MULTI: Learn: 10.8.0.10 -> jacek/83.30.135.214:37658
openvpn[13257]: jacek/83.30.135.214:37658 MULTI: primary virtual IP for jacek/83.30.135.214:37658: 10.8.0.10
openvpn[13257]: jacek/83.30.135.214:37658 PUSH: Received control message: 'PUSH_REQUEST'
openvpn[13257]: jacek/83.30.135.214:37658 send_push_reply(): safe_cap=940
openvpn[13257]: jacek/83.30.135.214:37658 SENT CONTROL [jacek]: 'PUSH_REPLY,route 10.8.0.1 255.255.255.255,dhcp-option DNS 10.8.0.1,dhcp-option DOMAIN ABC.COM,ping 10,ping-restart 60,ifconfig 10.8.0.10 10.8.0.9' (status=1)

openvp logs on my side:

Aug 05 17:13:55 localhost.localdomain openvpn[1198]: TCPv4_CLIENT link remote: [AF_INET]XXX.XX.37.71:1194
Aug 05 17:13:55 localhost.localdomain openvpn[1198]: TLS: Initial packet from [AF_INET]XXX.XX.37.71:1194, sid=89cc981c d57dd826
Aug 05 17:13:56 localhost.localdomain openvpn[1198]: VERIFY OK: depth=1, C=XX, ST=XX, L=XXX, O=XXX, OU=XXX, CN=XXX, name=XXX, emailAddress=mail@ABC.COM
Aug 05 17:13:56 localhost.localdomain openvpn[1198]: VERIFY OK: depth=0, C=XX, ST=XX, L=XXX, O=XXX, OU=XXX, CN=XXX, name=XXX, emailAddress=mail@ABC.COM
Aug 05 17:13:58 localhost.localdomain openvpn[1198]: Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key
Aug 05 17:13:58 localhost.localdomain openvpn[1198]: Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Aug 05 17:13:58 localhost.localdomain openvpn[1198]: Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key
Aug 05 17:13:58 localhost.localdomain openvpn[1198]: Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Aug 05 17:13:58 localhost.localdomain openvpn[1198]: Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 1024 bit RSA
Aug 05 17:13:58 localhost.localdomain openvpn[1198]: [static] Peer Connection Initiated with [AF_INET]XXX.XX.37.71:1194
Aug 05 17:14:00 localhost.localdomain openvpn[1198]: SENT CONTROL [static]: 'PUSH_REQUEST' (status=1)
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: PUSH: Received control message: 'PUSH_REPLY,route 10.8.0.1 255.255.255.255,dhcp-option DNS 10.8.0.1,dhcp-option DOMAIN ABC.COM,ping 10,ping-restart 60,ifconfig 10.8.0.10 10.8.0.9'
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: OPTIONS IMPORT: timers and/or timeouts modified
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: OPTIONS IMPORT: --ifconfig/up options modified
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: OPTIONS IMPORT: route options modified
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: OPTIONS IMPORT: --ip-win32 and/or --dhcp-option options modified
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: ROUTE_GATEWAY 10.123.123.1/255.255.255.0 IFACE=wlan0 HWADDR=44:6d:57:32:81:2e
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: TUN/TAP device tun0 opened
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: TUN/TAP TX queue length set to 100
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: /usr/sbin/ip link set dev tun0 up mtu 1500
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: /usr/sbin/ip addr add dev tun0 local 10.8.0.10 peer 10.8.0.9
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: /usr/sbin/ip route add 10.8.0.1/32 via 10.8.0.9
Aug 05 17:14:01 localhost.localdomain openvpn[1198]: Initialization Sequence Completed

It looks like everything's fine.

But. I checked /var/log/messages also... and I found that line:

Aug  5 17:14:01 localhost NetworkManager[761]: <warn> /sys/devices/virtual/net/tun0: couldn't determine device driver; ignoring...

ip a returns:

5: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
    link/none 
    inet 10.8.0.10 peer 10.8.0.9/32 scope global tun0
       valid_lft forever preferred_lft forever

route -n returns:

# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.123.123.1    0.0.0.0         UG    0      0        0 wlan0
10.8.0.1        10.8.0.9        255.255.255.255 UGH   0      0        0 tun0
10.8.0.9        0.0.0.0         255.255.255.255 UH    0      0        0 tun0
10.123.123.0    0.0.0.0         255.255.255.0   U     0      0        0 wlan0

So basically everything works, except the DNS being pushed... Oh! Right, and my /etc/resolv.conf:

# Generated by NetworkManager
domain home
search home
nameserver 10.123.123.1

Where's the issue?

(I have a response from Windows-user with openvpn client, that on his side DNS works fine, so it's an issue on my side.

Ok now I have another response (after I restarted openvpn service on server side) - it's not working.

I must say that it worked yesterday on my machine too.. so have I screwed up something on server? What could it be? )

Edit: Okay, I've got another Windows-user response (the same user as before) - it's working now. So.. I guess it was caused by openvpn restart and some delays with it. I haven't done anything since then. So we're back onto my machine.

I also traced that that wierd tun0 message appeared also yesterday, and yesterday it worked. Or maybe I added entry to resolv.conf by myself? I don't remember.. (damn it)

Answer 1

This works for me: http://www.softwarepassion.com/solving-dns-problems-with-openvpn-on-ubuntu-box/

The important step is adding following three lines of configuration into your client openvpn config file:

script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf

Also ensure the resolvconf package is installed on the client, because that update-resolv-conf script depends on it.

It works with openvpn client service or command to start it manually.

However, the Ubuntu Network Manager doesn't this. It's an issue so far: https://bugs.launchpad.net/ubuntu/+source/openvpn/+bug/1211110

Answer 2

Works for me after disabling NetworkManager's own dnsmasq.

Edit /etc/NetworkManager/NetworkManager.conf

 #dns=dnsmasq

and restart NetworkManager

sudo restart network-manager

Answer 3

Finally works (with standard NetworkManager and OVPN plugin)

nmcli -p connection modify MY_VPN_CONNECTION ipv4.never-default no
nmcli -p connection modify MY_VPN_CONNECTION ipv4.ignore-auto-dns no
nmcli -p connection modify MY_VPN_CONNECTION ipv4.dns-priority -42

In this case once VPN connection is established, all DNS requests are directed to VPN-supplied DNS servers without any manipulations with dnsmasq, up/down/dispatch helper scripts.

Answer 4

im running on linux ubuntu 18.04 and i had the same issue. The scripts in up and down sections only works for me if i execute the openvpn script in the command line but in my case, i running the Openvpn with Network Manager GUI. To resolve the issue, i create a rule in udev system to execute an script that change my DNS nameservers and domain and search tags.

To accomplished the tasks i use the name "exa" to named the interface as an example. You sure use the name that you want; please take care of the name in all sections of the tasks, and replace in all parts.

1- first change the order of the "dns" word in /etc/nsswitch.conf for the line that start with hosts:

old:

hosts:          files mdns4_minimal [NOTFOUND=return] resolve [!UNAVAIL=return] dns myhostname

new:

hosts:          files mdns4_minimal dns [NOTFOUND=return] resolve [!UNAVAIL=return] myhostname

2- next, create a bash script in /usr/local/bin/add_dns.sh and put the privileges to full (777):

#!/bin/bash

sleep 5

mv /etc/resolv.conf /etc/resolv.conf.old
echo "nameserver 10.10.10.10" > /etc/resolv.conf
echo "nameserver 10.10.11.10" >> /etc/resolv.conf
echo "search domain.example.com" >> /etc/resolv.conf
echo "domain domain.example.com" >> /etc/resolv.conf

3- create a rule in udev, /etc/udev/rules.d/74-exa-vpn.rules:

ACTION=="add", SUBSYSTEM=="net", ENV{INTERFACE}=="exa", RUN+="/usr/local/bin/add_dns.sh"

4- reload the udev config with:

$ udevadm control --reload

5- Go to the networkmanager GUI and next go to the config of the VPN profile. Next, go to the tab "identity" -> "Advanced": in the option "set virutal device type TUN and name", put the name "exa" and save all.

The good thing is when i disconnect the VPN, the networkmanager replace the file created by the udev script and replace for the original.

Answer 5

It is possible to push DNS settings in OpenVPN. Like you have in your config, it is done in the server configuration with the following line:

push "dhcp-option DNS 10.20.30.40"

This works out of the gate for me using the Windows GUI, but it needs a bit of nudging for Linux systems. For connecting to my home network (using Fedora 18 at present), I used a script by gronke on GitHub (https://github.com/gronke/OpenVPN-linux-push) to automate the updating process.

To use these scripts, I added the following to my OpenVPN client file:

up /home/gadgeteering/tools/vpn/up.sh
down /home/gadgeteering/tools/vpn/down.sh

up.sh:

#! /bin/bash
DEV=$1

if [ ! -d /tmp/openvpn ]; then
mkdir /tmp/openvpn
fi
CACHE_NAMESERVER="/tmp/openvpn/$DEV.nameserver"
echo -n "" > $CACHE_NAMESERVER

dns=dns
for opt in ${!foreign_option_*}
do
eval "dns=\${$opt#dhcp-option DNS }"
if [[ $dns =~ [0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3} ]]; then
if [ ! -f /etc/resolv.conf.default ]; then
cp /etc/resolv.conf /etc/resolv.conf.default
fi

cat /etc/resolv.conf | grep -v ^# | grep -v ^nameserver > /tmp/resolv.conf
echo "nameserver $dns" >> /tmp/resolv.conf
echo $dns >> $CACHE_NAMESERVER
cat /etc/resolv.conf | grep -v ^# | grep -v "nameserver $dns" | grep nameserver >> /tmp/resolv.conf
mv /tmp/resolv.conf /etc/resolv.conf

fi
done

down.sh:

#! /bin/bash
DEV=$1
CACHE_NAMESERVER="/tmp/openvpn/$DEV.nameserver"
echo $CACHE_NAMESERVER

if [ -f $CACHE_NAMESERVER ]; then
for ns in `cat $CACHE_NAMESERVER`; do
echo "Removing $ns from /etc/resolv.conf"
cat /etc/resolv.conf | grep -v "nameserver $ns" > /tmp/resolv.conf
mv /tmp/resolv.conf /etc/resolv.conf

done
fi

Answer 6

There is a possibility to make NetworkManager working by manually replacing /etc/resolv.conf. Beware that this is quite a hack and cannot be considered as a valid solution for every situation.

#!/bin/bash
case "$2" in
    vpn-up)
    tmp=$(mktemp)
    func=$(mktemp)
    echo 'ping -c 1 -w 1 -q $1 > /dev/null ;
          if [ 0 -eq $? ]; then echo $1; fi' > $func
    grep -v "^#" /etc/resolv.conf > $tmp
    grep -rl type=vpn /etc/NetworkManager/system-connections \
        | xargs -n 1 sed -rne 's|dns=||p' \
        | sed -re 's|;|\n|g' \
        | grep -v "^\s*$" \
        | xargs -n 1 bash $func \
        | sed -re "s|(.*)|nameserver \1|" \
        | cat - $tmp \
        > /etc/resolv.conf
    rm -f $tmp $func;;
    vpn-down) resolvconf -u;;
esac

This script should be placed under /etc/NetworkManager/dispatcher.d; should be executable and owned by root. It reads all NetworkManager vpn configutations it can find and rewrites /etc/resolv.conf with accessible nameservers found there. It doesn't write domain and search lines; but it allows to forget about nasty NetworkManager bug.

I use Ubuntu 16.04, it works.

Answer 7

OpenVPN is currently unable to push DNS settings. You will have to manually change /etc/resolv.conf to match your (secured) DNS server. I just run a BIND9 service on the same machine as my Access Server and point to that via tunnel. Use your local IP adress of that machine eg 192.168.1.110

Good luck!

Jasper

Answer 8

I have an OpenSUSE client that doesn't use resolvconf, nor systemd-networkd, but I was able to modify the common update-resolv-conf script to work with NetworkManager's nmcli command:

#!/usr/bin/env 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
#
# 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-SEARCH bnc.local'

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" || "$part2" == "DOMAIN-SEARCH" ]] ; then
                IF_DNS_SEARCH="$IF_DNS_SEARCH $part3"
            fi
        fi
    done
    if [ -n "$IF_DNS_SEARCH" ]; then
        nmcli connection modify "${dev}" ipv4.dns-search "$IF_DNS_SEARCH"
    fi
    if [ -n "$IF_DNS_NAMESERVERS" ]; then
        nmcli connection modify "${dev}" ipv4.dns "$IF_DNS_NAMESERVERS"
    fi
    nmcli connection up "${dev}" # Force NM to reevaluate the properties
    ;;
esac

# Workaround / jm@epiclabs.io 
# force exit with no errors. Due to an apparent conflict with the Network Manager
# $RESOLVCONF sometimes exits with error code 6 even though it has performed the
# action correctly and OpenVPN shuts down.
exit 0

It doesn't have a down handler because NetworkManager automatically removes the nameserver and search (DNS search) parameters on the termination of the connection.