Virtual Ethernet device
Virtual Ethernet device is an Ethernet-like device which can be used inside a container. Unlike venet network device, veth device has a MAC address, therefore it can be used in configurations, when veth is bridged to ethX or other device and container's user fully sets up his networking himself, including IPs, gateways etc.
Virtual Ethernet device consist of two Ethernet devices -- the one in CT0 and another one in CT. These devices are connected to each other, so if a packet goes to one device it will come out from the other device.
Contents
- 1 Virtual Ethernet device usage
- 2 Common configurations with virtual Ethernet devices
- 3 See also
- 4 External links
Virtual Ethernet device usage
Kernel module
First of all, make sure the vzethdev module is loaded:
# lsmod | grep vzeth vzethdev 8224 0 vzmon 35164 5 vzethdev,vznetdev,vzrst,vzcpt vzdev 3080 4 vzethdev,vznetdev,vzmon,vzdquota
In case it is not loaded, load it:
# modprobe vzethdev
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Note: in vzctl < 3.0.11, vzethdev is not autoloaded by /etc/init.d/vz script, so you have to edit it to load this module.
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MAC addresses
In the below commands, you should use random MAC addresses. Do not use MAC addresses of real eth devices, because this can lead to collisions.
MAC addresses must be entered in XX:XX:XX:XX:XX:XX format.
YOU MAY NOT NEED TO GENERATE MAC ADDRESSES BY HAND BECAUSE vzctl --veth_add MAY GENERATE THEM AUTOMATICALLY AS NECESSARY.
Nevertheless, there is a utility script available for generating MAC addresses: http://www.easyvmx.com/software/easymac.sh. It is to be used like this:
chmod +x easymac.sh ./easymac.sh -R
Adding veth to a CT
syntax vzctl version > 3.0.22
vzctl set <CTID> --netif_add <ifname>[,<mac>,<host_ifname>,<host_mac>,<bridge>]
Here
- ifname is the Ethernet device name in the CT
- mac is its MAC address in the CT
- host_ifname is the Ethernet device name on the host (CT0)
- host_mac is its MAC address on the host (CT0)
- bridge is an optional parameter which can be used in custom network start scripts to automatically add the interface to a bridge.
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Note: All parameters except ifname are optional and are automatically generated if not specified.
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Example:
vzctl set 101 --netif_add eth0 --save
Or, if you want to specify everything:
vzctl set 101 --netif_add eth0,00:12:34:56:78:9A,veth101.0,00:12:34:56:78:9B --save
Or, if you want to specify the bridge and leave the other values autogenerated:
vzctl set 101 --netif_add eth0,,,,vmbr1 --save
syntax vzctl version >= 3.0.14
Syntax is the same as above, but without a <bridge> parameter.
syntax vzctl version < 3.0.14
vzctl set <CTID> --veth_add <dev_name>,<dev_addr>,<ve_dev_name>,<ve_dev_addr>
Here
- dev_name is the Ethernet device name that you are creating on the host system
- dev_addr is its MAC address
- ve_dev_name is the corresponding Ethernet device name you are creating on the CT
- ve_dev_addr is its MAC address
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Note: this option is incremental, so devices are added to already existing ones. |
NB there should no spaces after the commas.
Example:
[host-node] ifconfig eth0 ... HWaddress 00:12:34:56:78:9B ...
[host-node] easymac.sh -R 00:12:34:56:78:9A
vzctl set 101 --veth_add veth101.0,00:12:34:56:78:9A,eth0,00:12:34:56:78:9B --save
After executing this command veth device will be created for CT 101 and veth configuration will be saved to a CT configuration file. Host-side Ethernet device will have veth101.0 name and 00:12:34:56:78:9A MAC address. CT-side Ethernet device will have eth0 name and 00:12:34:56:78:9B MAC address.
Removing veth from a CT
syntax vzctl version >= 3.0.14
vzctl set <CTID> --netif_del <dev_name>|all
Here
dev_nameis the Ethernet device name in the CT.
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Note: If you want to remove all Ethernet devices in CT, use all.
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Example:
vzctl set 101 --netif_del eth0 --save
syntax vzctl version < 3.0.14
vzctl set <CTID> --veth_del <dev_name>
Here dev_name is the Ethernet device name in the host system.
Example:
vzctl set 101 --veth_del veth101.0 --save
After executing this command veth device with host-side Ethernet name
veth101.0 will be removed from CT101 and veth configuration
will be updated in CT config file.
Common configurations with virtual Ethernet devices
Module vzethdev must be loaded to operate with veth devices.
Simple configuration with virtual Ethernet device
Start a CT
[host-node]# vzctl start 101
Add veth device to CT
[host-node]# vzctl set 101 --netif_add eth0 --save
This allocates a MAC address and associates it with the host eth0 port.
Configure devices in CT0
[host-node]# ifconfig veth101.0 0 [host-node]# echo 1 > /proc/sys/net/ipv4/conf/veth101.0/forwarding [host-node]# echo 1 > /proc/sys/net/ipv4/conf/veth101.0/proxy_arp [host-node]# echo 1 > /proc/sys/net/ipv4/conf/eth0/forwarding [host-node]# echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp
Notes:
- These files did not exist for me when trying (Mrjcleaver 14:04, 31 May 2008 (EDT))
Configure device in CT
[host-node]# vzctl enter 101 [ve-101]# /sbin/ifconfig eth0 0 [ve-101]# /sbin/ip addr add 192.168.0.101 dev eth0 [ve-101]# /sbin/ip route add default dev eth0
Notes:
- Until you ifconfig eth0 it won't appear. When you do it will use the mac address netif_add added earlier
- 192.168.0.101 is chosen to be an unrouteable private ip address. Where 101 reminds you that it is node 101.
- The "ip route" tells all traffic to head to "device eth0"
- In theory you could use dhcpd with OpenVZ and dhclient to pick up an DHCP address from your router instead of hardwiring it
Add route in CT0
[host-node]# ip route add 192.168.0.101 dev veth101.0
Virtual Ethernet device with IPv6
Start a CT
[host-node]# vzctl start 101
Add veth device to the CT
[host-node]# vzctl set 101 --veth_add eth0,00:12:34:56:78:9A,eth0,00:12:34:56:78:9B --save
Configure devices in the CT0
[host-node]# ifconfig veth101.0 0 [host-node]# echo 1 > /proc/sys/net/ipv6/conf/veth101.0/forwarding [host-node]# echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding [host-node]# echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
Configure device in CT
[host-node]# vzctl enter 101 [ve-101]# /sbin/ifconfig eth0 0
Start router advertisement daemon (radvd) for IPv6 in CT0
First you need to edit radvd configuration file. Here is a simple example of /etc/radv.conf:
interface veth101.0
{
AdvSendAdvert on;
MinRtrAdvInterval 3;
MaxRtrAdvInterval 10;
AdvHomeAgentFlag off;
prefix 3ffe:2400:0:0::/64
{
AdvOnLink on;
AdvAutonomous on;
AdvRouterAddr off;
};
};
interface eth0
{
AdvSendAdvert on;
MinRtrAdvInterval 3;
MaxRtrAdvInterval 10;
AdvHomeAgentFlag off;
prefix 3ffe:0302:0011:0002::/64
{
AdvOnLink on;
AdvAutonomous on;
AdvRouterAddr off;
};
};
Then, start radvd:
[host-node]# /etc/init.d/radvd start
Add IPv6 addresses to devices in CT0
[host-node]# ip addr add dev veth101.0 3ffe:2400::212:34ff:fe56:789a/64 [host-node]# ip addr add dev eth0 3ffe:0302:0011:0002:211:22ff:fe33:4455/64
Virtual Ethernet devices can be joined in one bridge
Perform steps 1 - 4 from Simple configuration chapter for several containers and/or veth devices
Create bridge device
[host-node]# brctl addbr vzbr0
Add veth devices to bridge
[host-node]# brctl addif vzbr0 veth101.0 ... [host-node]# brctl addif vzbr0 veth101.n [host-node]# brctl addif vzbr0 veth102.0 ... ... [host-node]# brctl addif vzbr0 vethXXX.N
Configure bridge device
[host-node]# ifconfig vzbr0 0 [host-node]# echo 1 > /proc/sys/net/ipv4/conf/vzbr0/forwarding [host-node]# echo 1 > /proc/sys/net/ipv4/conf/vzbr0/proxy_arp
Add routes in CT0
[host-node]# ip route add 192.168.101.1 dev vzbr0 ... [host-node]# ip route add 192.168.101.n dev vzbr0 [host-node]# ip route add 192.168.102.1 dev vzbr0 ... ... [host-node]# ip route add 192.168.XXX.N dev vzbr0
Thus you'll have more convinient configuration, i.e. all routes to containers will be through this bridge and containers can communicate with each other even without these routes.
Making a veth-device persistent
According to http://bugzilla.openvz.org/show_bug.cgi?id=301 , a bug that stopped the veth device persistent was "Obsoleted now when --veth_add/--veth_del are introduced"
See http://wiki.openvz.org/w/index.php?title=Virtual_Ethernet_device&diff=5990&oldid=5989#Making_a_veth-device_persistent for a workaround that used to be described in this section.
That's it! At this point, when you restart the CT you should see a new line in the output, indicating that the interface is being configured and a new route being added. And you should be able to ping the host, and to enter the CT and use the network.
Making a bridged veth-device persistent
Like the above example, here it is how to add the veth device to a bridge in a persistent way.
method for vzctl version > 3.0.22
Newer versions of vzctl includes a 'vznetaddbr' script, which makes use of the new <bridge> parameter of the --netif_add switch.
Just create /etc/vz/vznet.conf containing the following.
#!/bin/bash EXTERNAL_SCRIPT="/usr/sbin/vznetaddbr"
The script uses 'vmbr0' as default bridge name when no bridge is specified.
method for vzctl version <= 3.0.22
Older vzctl doesn't offer an automatic function to do this.
1. First, edit the CT's configuration to specify what is the host bridge , and to indicate that a custom script should be run when starting up a CT.
- Open up /etc/vz/conf/CTID.conf
- Comment out any IP_ADDRESS entries to prevent a CTNET-device from being created in the CT
- Add or change the entry CONFIG_CUSTOMIZED="yes"
- Add an entry VZHOSTBR="<bridge if>" which is the bridge interface (already configured and up), you want to extend.
2. Now to create that "custom script". The following helper script will check the configuration file for the bridge interface name and for the veth interface, and add the interface to the bridge. Create the script /usr/sbin/vznetaddbr to have the following, and then chmod 0500 /usr/sbin/vznetaddbr to make it executable.
#!/bin/bash # /usr/sbin/vznetaddbr # a script to add virtual network interfaces (veth's) in a CT to a bridge on CT0 CONFIGFILE=/etc/vz/conf/$VEID.conf . $CONFIGFILE VZHOSTIF=`echo $NETIF |sed 's/^.*host_ifname=\(.*\),.*$/\1/g'` if [ ! -n "$VZHOSTIF" ]; then echo "According to $CONFIGFILE CT$VEID has no veth interface configured." exit 1 fi if [ ! -n "$VZHOSTBR" ]; then echo "According to $CONFIGFILE CT$VEID has no bridge interface configured." exit 1 fi echo "Adding interface $VZHOSTIF to bridge $VZHOSTBR on CT0 for CT$VEID" /sbin/ifconfig $VZHOSTIF 0 echo 1 > /proc/sys/net/ipv4/conf/$VZHOSTIF/proxy_arp echo 1 > /proc/sys/net/ipv4/conf/$VZHOSTIF/forwarding /usr/sbin/brctl addif $VZHOSTBR $VZHOSTIF exit 0
3. Now create /etc/vz/vznet.conf containing the following. This is what defines the "custom script" as being the vznetaddbr which you just created.
#!/bin/bash EXTERNAL_SCRIPT="/usr/sbin/vznetaddbr"
This may not work for particularily old versions of vzctl, e.g., the version 3.0.11 that ships with Debian Etch. For those versions, you can try a hack: Use the custom script /etc/vz/conf/$VID.mount which is available, even in these old versions. But it gets called too early, before the networking has been set up. But it can start some background process, which waits and occasionally polls until $VZHOSTIF has become available. Here is one way to go about it:
#!/bin/bash
CONFIGFILE="/etc/vz/conf/$VEID.conf"
if [ -f "$CONFIGFILE" ]
then
. "$CONFIGFILE"
VZHOSTIF=`echo $NETIF |sed 's/^.*host_ifname=\(.*\),.*$/\1/g'`
export VZHOSTIF
export VZHOSTBR
# Fork into the background and try a few times,
# until the host side of the interface appears:
/bin/bash -c 'for i in 5 10 20 40 80 160
do
if ifconfig -a | grep -q "$VZHOSTIF"
then
exec /usr/sbin/vznetaddbr
else
sleep "$i"
fi
done
' &
# In the meantime, let the CT's start process continue,
# or else the interface will never appear:
exit 0
else
$0: Config file "$CONFIGFILE" does not exist.
exit 1
fi
4. Of course, the CT's operating system will need to have . Consult the manual for your CT's OS for details.
When the CT is started, the veth specified in the NETIF value is added to the bridge specified. You can check this by doing brctl show
Inside the CT you can configure the interface statically or using dhcp, as a real interface attached to a switch on the lan.
Virtual Ethernet devices + VLAN
This configuration can be done by adding vlan device to the previous configuration.
See also
- Virtual network device
- Differences between venet and veth
- Using private IPs for Hardware Nodes
- Troubleshooting: Bridge doesn't forward packets
