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

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root@132 / [12]# echo 1 > /proc/sys/net/ipv6/bindv6only
 
root@132 / [12]# echo 1 > /proc/sys/net/ipv6/bindv6only
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Or put in your /etc/sysctl.conf file:
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net.ipv6.bindv6only = 1
 
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Revision as of 13:56, 4 August 2010

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

Kernel TUN/TAP support

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) or into /etc/sysconfig/vz-scripts/CTID.mount. (echo 'modprobe tun' >> /etc/sysconfig/vz-scripts/CTID.mount)

Granting container an access to TUN/TAP

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

vzctl set 101 --devices c:10:200:rw --save
vzctl set 101 --capability net_admin:on --save

And create the character device file inside the container (execute the following on the host node): 

vzctl exec 101 mkdir -p /dev/net
vzctl exec 101 mknod /dev/net/tun c 10 200
vzctl exec 101 chmod 600 /dev/net/tun

Configuring VPN inside container

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:

Tinc problems

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

Troubleshooting

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

# 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.

The solution is given here: 

http://kb.parallels.com/en/5228

Also see page 69-70 of: 

http://download.openvz.org/doc/OpenVZ-Users-Guide.pdf

Note that the above steps do not solve the problem if a gentoo VE sits on a Centos HN; it's still an unsolved mystery.

External links

Retrieved from "https://wiki.openvz.org/index.php?title=VPN_via_the_TUN/TAP_device&oldid=8981"