Ubuntu Manpage: vnetbuild.conf - VNetBuild configuration file

Provided by: firehol-tools-doc_3.1.7+ds-3_all

NAME

       vnetbuild.conf - VNetBuild configuration file

SYNOPSIS

              host *ID*
                  dev *DEVICE* [ *ID*/*PAIRDEV* ] [ *IP*/*MASK*... ]
                  ...
                  bridgedev *BRIDGE* [ *DEVICE*... ] [ *IP*/*MASK*... ]
                  ...
                  route *ROUTECMD*
                  ...
                  pre_up *DEVICE* *CUSTOMCMD*
                  ...
                  exec *CUSTOMCMD*
                  ...

              ...

              switch *ID*
                  dev *DEVICE* [ *ID*/*PAIRDEV* ]
                  ...
                  pre_up *DEVICE* *CUSTOMCMD*
                  ...
                  exec *CUSTOMCMD*
                  ...

              ...

DESCRIPTION

       There  is  no  default  configuration  file for vnetbuild(1); one must always be specified on the command
       line.

       The configuration file defines a set of namespaces that will be operated on.

       VNetBuild defines two types of namespace, a host and a switch.  Any number of each may be specified, with
       any number of configuration statements in each.

       Note   The Linux kernel does not see any difference between a host and  a  switch  namespace.   VNetBuild
              provides the distinction to make it easy build full virtual networks.

NAMESPACE DEFINITIONS

       Namespace  definitions  come  in two types, host and switch.  Simply provide a simple unique alphanumeric
       ID.  Any subsequent statements apply to this namespace until the next host or switch statement.

       A host definition is designed to work like a physical machine.  It allows you to specify  any  number  of
       dev  entries  for  network  interfaces, with their IP addresses.  You can also define any number of Linux
       bridges with bridgedev to add your defined interfaces to.

       A host also allows any number of custom exec commands for extensibility and provides a route statement to
       deal with the common case of wanting to add network routes to the host.

       A switch definition is designed to work like a physical network switch.  It allows you to add any  number
       of dev entries (and also custom exec commands for extensibility) but nothing else.

       In  addition, dev entries in a switch may only specify device names, they cannot have an IP address asso‐
       ciated.  A switch has a bridge automatically created in it and all dev entries are automatically added to
       it.

CONFIGURATION STATEMENTS

dev DEVICE ...
Define a virtual ethernet device, DEVICE in a host or switch.

Devices must exist in pairs. A dev must first be defined unpaired in a namespace, then some sub‐
sequent dev must define the pair:

host a
dev veth0
host b
dev vppp0 a/veth0

Any DEVICE name which is acceptable to the Linux kernel may be used. We recommend sticking to
e.g. veth0, vppp0 etc. to make it clear that they are virtual and also how you are thinking of
the device in terms of your setup. Devices will be created as type veth, irrespective of what you
call them.

Hosts may optionally specify one or more IP/MASK values which will be applied (along with the cal‐
culated broadcast address) automatically, e.g.:

host a
dev veth0 10.0.0.1/8 192.168.1.2/24
host b
dev vppp0 a/veth0 10.0.0.2/8 192.168.1.3/24

A dev may not specify an IP address if it is in a switch. Switches exist just to tie together
multiple devices in hosts, just like a physical network switch.

bridgedev BRIDGE ...
Define an ethernet bridge, BRIDGE in a host. These are setup automatically using ip(8) and shown
with bridge(8).

A bridge can specify network devices from its own namespace to be automatically added, as well as
its own IP address(es).

host a
dev veth0
dev veth1 otherns/vdev0
bridgedev vbr0 veth0 veth1 10.0.0.3/8

Devices included in a bridge generally do not need their own IP address (although that is permit‐
ted).

Bridges cannot have a pair themselves, but any devices added to a bridge need a pair as usual.

route ROUTECMD
Specify an additional network route for a host.

Most commonly to add a default route from hosts on a “LAN” to the machine that acts as a gateway,
e.g.:

route default via 10.0.0.254

The syntax of ROUTECMD is anything that can fit this pattern:

ip route add ROUTECMD

See ip(8) and ip-route(8) for help adding routes. If you want to do anything more complex than
simply adding routes, use the exec configuration statement.

pre_up DEVICE CUSTOMCMD
Execute custom commands in a host or switch just before bringing up the specified device. All of
the pre_up statements for a device are combined and executed in the namespace.

In addition to any explicitly defined interfaces, switches have an implicit bridge device called
switch which can also be used in pre_up commands.

Bridges always start after other devices, so to run a command after all everything has been creat‐
ed but before any interfaces are up, you can make use of pre_up on the first defined dev.

See below for some common uses for custom pre_up and exec commands.

exec CUSTOMCMD
Execute a custom command in a host or switch once the rest of the namespace setup is complete.

Once all the namespaces are created, the final step in setting each one up is to have its exec
statements combined and executed.

It is roughly the equivalent to writing your own script and executing it after vnetbuild start has
finished:

sudo ip netns exec myns ./myscript.sh

See below for some common uses for custom pre_up and exec commands.

COMMON CUSTOM COMMANDS

       For the most part it doesn’t matter whether these commands are used in pre_up or exec  operations  -  the
       only  difference is when they will execute, so e.g. if you want a firewall in place before any interfaces
       come up then start it from the pre_up of the first device.  If you only want the firewall after  all  de‐
       vices are up, put it in exec, e.g.:

              host myfirewall
                  ...
                  exec firehol myfirewall.conf start

       Forwarding is not enabled by the Linux kernel when a namespace is first created.  This can be easily done
       for any hosts that need to forward traffic:

              host mygateway
                  ...
                  exec echo 1 > /proc/sys/net/ipv4/ip_forward

       The exec operates in the mygateway namespace so your host is not affected.

       Bridges  are  created without STP being enabled.  To enable STP to ensure loops are not created, the fol‐
       lowing can be done:

              host myhost
                  bridgedev vbr0 ...
                  ...
                  pre_up vbr0 echo 2 > /sys/class/net/vbr0/bridge/stp_state

              switch myswitch
                  ...
                  pre_up switch echo 2 > /sys/class/net/vbr0/bridge/stp_state

       You could also use brctl stp vbr0 on and brctl stp switch on instead of setting the values directly.   To
       disable multicast snooping you can use exactly the same method e.g.:

              switch myswitch
                  ...
                  pre_up switch echo 0 > /sys/class/net/switch/bridge/multicast_snooping

       It is possible to run firehol within a namespace to set up custom

       Logs  from network namespaces are not included in the normal system logs.  To enable iptables logging you
       must start an instance of ulogd(8) in the namespace and use ULOG or NFLOG  logging.   For  FireHOL,  that
       means set FIREHOL_LOG_MODE=ULOG or FIREHOL_LOG_MODE=NFLOG.  Note that NFLOG only works with ulogd version
       2.

       The default configuration for ulogd(8) is /etc/ulogd.conf.  Assuming the default place it will write ipt‐
       ables logs to is /var/log/ulog/syslogemu.log (otherwise change the sed command as required), it is simple
       to set up per-namespace logging:

              host mygateway
                ...
                exec sed 's:/var/log/ulog/syslogemu.log:/var/log/ulog/mygateway.log:' /etc/ulogd.conf > $NSTMP/ulogd.conf
                exec /usr/sbin/ulogd -d -c $NSTMP/ulogd.conf

       The -d flag to ulogd(8) makes it become a daemon; when vnetbuild stop executes it will automatically kill
       any programs running in the namespaces is is stopping, which includes the logging daemon.

       The  configuration  file  will  get cleaned as soon as vnetbuild start is finished.  To be able to access
       such files you need to write them to a location not under $NSTMP or create  them  outside  the  vnetbuild
       configuration altogether.

EXAMPLE

       A simple LAN arrangement with two hosts, one of which is a gateway to third host:

              host host01
                dev veth0 10.0.0.1/8
                dev vppp0 192.168.0.1/24
                exec echo 1 > /proc/sys/net/ipv4/ip_forward
                route default via 192.168.0.1

              host host02
                dev veth0 10.0.0.2/8
                route default via 10.0.0.1

              switch lan
                dev d01 host01/veth0
                dev d02 host02/veth0

              host extern01
                dev veth0 host01/vppp0 192.168.0.254/24
                route default via 192.168.0.1
                exec echo 1 > /proc/sys/net/ipv4/ip_forward

LIMITATIONS

       When created, the namespaces setup by vnetbuild are completely disconnected from any real network.  There
       is  no way of defining such a connection in the vnetbuild configuration as allowing it would lead to con‐
       flicts with the normal network setup tools and configuration files in most distributions.

       It is possible to arrange your network so you can connect real devices into one  or  more  network  name‐
       spaces.  For the general approach see this mailing list post (http://lists.firehol.org/pipermail/firehol-
       support/2015-April/003043.html).

AUTHORS

       FireHOL Team.

VNetBuild Reference                             Built 24 Jan 2024                              vnetbuild.conf(5)