Difference between revisions of "VPN via the TUN/TAP device"

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<translate>
 +
<!--T:1-->
 
This article describes how to use VPN via the TUN/TAP device inside a [[container]].
 
This article describes how to use VPN via the TUN/TAP device inside a [[container]].
  
−
== Kernel TUN/TAP support ==
+
== Kernel TUN/TAP support == <!--T:2-->
 
OpenVZ supports VPN inside a container via kernel TUN/TAP module and device.
 
OpenVZ supports VPN inside a container via kernel TUN/TAP module and device.
 
To allow container #101 to use the TUN/TAP device the following should be done:
 
To allow container #101 to use the TUN/TAP device the following should be done:
  
 +
<!--T:3-->
 
Make sure the '''tun''' module has been already loaded on the [[hardware node]]:
 
Make sure the '''tun''' module has been already loaded on the [[hardware node]]:
 +
lsmod | grep tun
 +
 +
<!--T:4-->
 +
If it is not there, use the following command to load '''tun''' module:
 +
modprobe tun
 +
 +
<!--T:5-->
 +
To make sure that '''tun''' module will be automatically loaded on every reboot you can also add it or into <code>/etc/modules.conf</code> (on RHEL see <code>/etc/sysconfig/modules/</code> directory).
 +
 +
== Granting container an access to TUN/TAP == <!--T:6-->
 +
 +
<!--T:7-->
 +
Allow your container to use the tun/tap device by running the following commands on the host node:
 +
 +
<!--T:8-->
 +
CTID=101
 +
vzctl set $CTID --devnodes net/tun:rw --capability net_admin:on --save
 +
 +
== Configuring VPN inside container == <!--T:9-->
 +
After the configuration steps above are done it is possible to use VPN software working with TUN/TAP inside
 +
container just like on a usual standalone Linux box.
 +
 +
<!--T:10-->
 +
The following software can be used for VPN with TUN/TAP:
 +
* Tinc (http://tinc-vpn.org)
 +
* OpenVPN (http://openvpn.net)
 +
* Virtual TUNnel (http://vtun.sourceforge.net)
 +
 +
== Reaching hosts behind VPN container == <!--T:11-->
 +
In order to reach hosts behind VPN container you must configure it to use a VETH interface instead a VENET one, at least with an OpenVPN server.
 +
 +
<!--T:12-->
 +
With a VENET interface you will only reach the VPN container.
 +
 +
<!--T:13-->
 +
To use a VETH device follow [[Veth]] article.
 +
 +
<!--T:14-->
 +
If you insist on using a VENET interface and need to reach hosts behind the OpenVPN VE then you can use source NAT. You need to mangle source packets so that they appear to originate from the OpenVPN server VE.
 +
 +
== Tinc problems == <!--T:15-->
 +
 +
<!--T:16-->
 +
Using the default venet0:0 interface on the container, tinc seems to have problems as it complains the port 655 is already used on 0.0.0.0.
 +
 +
<!--T:17-->
 +
Netstat shows that the port 655 is available:
 +
 +
<!--T:18-->
 
<pre>
 
<pre>
−
# lsmod | grep tun
+
root@132 / [3]# netstat -l
 +
Active Internet connections (only servers)
 +
Proto Recv-Q Send-Q Local Address          Foreign Address        State     
 +
tcp        0      0 localhost.localdom:8001 *:*                    LISTEN   
 +
tcp        0      0 *:2223                  *:*                    LISTEN   
 +
tcp6      0      0 [::]:2223              [::]:*                  LISTEN   
 +
udp6      0      0 [::]:talk              [::]:*                           
 +
udp6      0      0 [::]:ntalk              [::]:*                           
 +
Active UNIX domain sockets (only servers)
 +
Proto RefCnt Flags      Type      State        I-Node  Path
 +
unix  2      [ ACC ]    STREAM    LISTENING    4831020  /var/run/uml-utilities/uml_switch.ctl
 
</pre>
 
</pre>
  
−
If it is not there, use the following command to load '''tun''' module:
+
<!--T:19-->
 +
Starting the Tincd daemon where it complains that port 655 is not available:
 +
 
 +
<!--T:20-->
 +
<pre>
 +
root@132 / [4]# tincd -n myvpn
 +
root@132 / [5]# tail -f /var/log/syslog
 +
Jul 26 14:08:01 132 /USR/SBIN/CRON[15159]: (root) CMD (  cd / && run-parts --report /etc/cron.hourly)
 +
Jul 26 14:37:42 132 -- MARK --
 +
Jul 26 14:57:42 132 -- MARK --
 +
Jul 26 15:08:01 132 /USR/SBIN/CRON[15178]: (root) CMD (  cd / && run-parts --report /etc/cron.hourly)
 +
Jul 26 15:11:23 132 tinc.myvpn[15139]: Got TERM signal
 +
Jul 26 15:11:23 132 tinc.myvpn[15139]: Terminating
 +
Jul 26 15:11:37 132 tinc.myvpn[15191]: tincd 1.0.8 (Aug 14 2007 13:51:23) starting, debug level 0
 +
Jul 26 15:11:37 132 tinc.myvpn[15191]: /dev/net/tun is a Linux tun/tap device (tun mode)
 +
Jul 26 15:11:37 132 tinc.myvpn[15191]: Can't bind to 0.0.0.0 port 655/tcp: Address already in use
 +
Jul 26 15:11:37 132 tinc.myvpn[15191]: Ready
 +
^C
 +
root@132 / [6]#
 +
</pre>
 +
 
 +
<!--T:21-->
 +
An echo to Bindv6only (see [http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=440150 discussion here]) seems to resolve the problem:
 +
 
 +
<!--T:22-->
 +
<pre>
 +
root@132 / [12]# echo 1 > /proc/sys/net/ipv6/bindv6only
 +
</pre>
 +
 
 +
<!--T:23-->
 +
Or put in your /etc/sysctl.conf file:
 +
 
 +
<!--T:24-->
 
<pre>
 
<pre>
−
# modprobe tun
+
net.ipv6.bindv6only = 1
 
</pre>
 
</pre>
  
−
You can also add it into /etc/modules.conf to make sure it will be loaded on every reboot automatically.
+
<!--T:25-->
 +
Then apply the changes with:
  
−
== Granting container an access to TUN/TAP ==
+
<!--T:26-->
−
Allow your container to use the tun/tap device:
+
<pre>
 +
root@132 / [14]# sysctl -p
 +
</pre>
  
−
vzctl set 101 --devices c:10:200:rw --save
+
== The tunctl problem == <!--T:27-->
−
vzctl set 101 --capability net_admin:on --save
+
Unfortunately, you are limited to [http://forum.openvz.org/index.php?t=msg&th=4280&goto=22066&#msg_22066 non-persistent tunnels inside the VEs]:
  
−
And create the character device file inside the container:
+
<!--T:28-->
 
<pre>
 
<pre>
−
# vzctl exec 101 mkdir -p /dev/net
+
# tunctl
−
# vzctl exec 101 mknod /dev/net/tun c 10 200
+
enabling TUNSETPERSIST: Operation not permitted
−
# vzctl exec 101 chmod 600 /dev/net/tun
 
 
</pre>
 
</pre>
  
−
== Configuring VPN inside container ==
+
<!--T:29-->
−
After the configuration steps above are done it is possible to use VPN software working with TUN/TAP inside
+
Get a patched tunctl [https://github.com/xl0/uml-utilities here], and run it with the -n option. It will create a non-persistent tun device and sleep instead of terminating, to keep the device from deletion. To remove the tunnel, kill the tunctl process.
−
container just like on a usual standalone linux box.
+
 
 +
 
 +
== Troubleshooting == <!--T:30-->
 +
If NAT is needed within the VE, this error will occur on attempts to use NAT:
  
−
The following software can be used for VPN with TUN/TAP:
+
<!--T:31-->
−
* Virtual TUNnel (http://vtun.sourceforge.net)
+
# iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j MASQUERADE
−
* OpenVPN (http://openvpn.sourceforge.net)
+
iptables v1.4.3.2: can't initialize iptables table `nat': Table does not exist (do you need to insmod?)
 +
Perhaps iptables or your kernel needs to be upgraded.
  
 +
<!--T:32-->
 +
Solution:
 +
* use recent kernel
 +
* enable NAT inside CT:
 +
: <code>vzctl set $CTID --netfilter full --save</code>
  
−
== External links ==
+
== External links == <!--T:33-->
 
* [http://vtun.sourceforge.net Virtual TUNnel]
 
* [http://vtun.sourceforge.net Virtual TUNnel]
−
* [http://openvpn.sourceforge.net OpenVPN]
+
* [http://openvpn.net OpenVPN]
−
 
+
* [http://tinc-vpn.org Tinc]
 +
* [http://openvpn.net/index.php/access-server/howto-openvpn-as/186-how-to-run-access-server-on-a-vps-container.html How to run OpenVPN Access Server in OpenVZ]
 +
* [http://kb.odin.com/en/696 Odin KB #696: Is VPN via the TUN/TAP device supported inside a Container?]
 +
</translate>
 
[[Category: HOWTO]]
 
[[Category: HOWTO]]
 
[[Category: Networking]]
 
[[Category: Networking]]

Latest revision as of 09:28, 31 October 2017

<translate> This article describes how to use VPN via the TUN/TAP device inside a container.

Kernel TUN/TAP support[edit]

OpenVZ supports VPN inside a container via kernel TUN/TAP module and device. To allow container #101 to use the TUN/TAP device the following should be done:

Make sure the tun module has been already loaded on the hardware node: 

lsmod | grep tun

If it is not there, use the following command to load tun module: 

modprobe tun

To make sure that tun module will be automatically loaded on every reboot you can also add it or into /etc/modules.conf (on RHEL see /etc/sysconfig/modules/ directory).

Granting container an access to TUN/TAP[edit]

Allow your container to use the tun/tap device by running the following commands on the host node:

CTID=101 

vzctl set $CTID --devnodes net/tun:rw --capability net_admin:on --save

Configuring VPN inside container[edit]

After the configuration steps above are done it is possible to use VPN software working with TUN/TAP inside container just like on a usual standalone Linux box.

The following software can be used for VPN with TUN/TAP:

Reaching hosts behind VPN container[edit]

In order to reach hosts behind VPN container you must configure it to use a VETH interface instead a VENET one, at least with an OpenVPN server.

With a VENET interface you will only reach the VPN container.

To use a VETH device follow Veth article.

If you insist on using a VENET interface and need to reach hosts behind the OpenVPN VE then you can use source NAT. You need to mangle source packets so that they appear to originate from the OpenVPN server VE.

Tinc problems[edit]

Using the default venet0:0 interface on the container, tinc seems to have problems as it complains the port 655 is already used on 0.0.0.0.

Netstat shows that the port 655 is available: 

root@132 / [3]# netstat -l
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 localhost.localdom:8001 *:*                     LISTEN     
tcp        0      0 *:2223                  *:*                     LISTEN     
tcp6       0      0 [::]:2223               [::]:*                  LISTEN     
udp6       0      0 [::]:talk               [::]:*                             
udp6       0      0 [::]:ntalk              [::]:*                             
Active UNIX domain sockets (only servers)
Proto RefCnt Flags       Type       State         I-Node   Path
unix  2      [ ACC ]     STREAM     LISTENING     4831020  /var/run/uml-utilities/uml_switch.ctl

Starting the Tincd daemon where it complains that port 655 is not available: 

root@132 / [4]# tincd -n myvpn
root@132 / [5]# tail -f /var/log/syslog
Jul 26 14:08:01 132 /USR/SBIN/CRON[15159]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Jul 26 14:37:42 132 -- MARK --
Jul 26 14:57:42 132 -- MARK --
Jul 26 15:08:01 132 /USR/SBIN/CRON[15178]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Jul 26 15:11:23 132 tinc.myvpn[15139]: Got TERM signal
Jul 26 15:11:23 132 tinc.myvpn[15139]: Terminating
Jul 26 15:11:37 132 tinc.myvpn[15191]: tincd 1.0.8 (Aug 14 2007 13:51:23) starting, debug level 0
Jul 26 15:11:37 132 tinc.myvpn[15191]: /dev/net/tun is a Linux tun/tap device (tun mode)
Jul 26 15:11:37 132 tinc.myvpn[15191]: Can't bind to 0.0.0.0 port 655/tcp: Address already in use
Jul 26 15:11:37 132 tinc.myvpn[15191]: Ready
^C
root@132 / [6]#

An echo to Bindv6only (see discussion here) seems to resolve the problem: 

root@132 / [12]# echo 1 > /proc/sys/net/ipv6/bindv6only

Or put in your /etc/sysctl.conf file: 

net.ipv6.bindv6only = 1

Then apply the changes with: 

root@132 / [14]# sysctl -p

The tunctl problem[edit]

Unfortunately, you are limited to non-persistent tunnels inside the VEs: 

# tunctl
enabling TUNSETPERSIST: Operation not permitted

Get a patched tunctl here, and run it with the -n option. It will create a non-persistent tun device and sleep instead of terminating, to keep the device from deletion. To remove the tunnel, kill the tunctl process.


Troubleshooting[edit]

If NAT is needed within the VE, this error will occur on attempts to use NAT:

  1. iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j MASQUERADE
iptables v1.4.3.2: can't initialize iptables table `nat': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

Solution:

  • use recent kernel
  • enable NAT inside CT:
vzctl set $CTID --netfilter full --save

External links[edit]

</translate>

Retrieved from "https://wiki.openvz.org/index.php?title=VPN_via_the_TUN/TAP_device&oldid=22831"