Copyright © 2010 Thomas M. Eastep
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
2023/02/18
Table of Contents
The Shorewall init scripts released from shorewall.net and by most distributions start Shorewall after networking. This allows Shorewall to detect the network configuration and taylor itself accordingly. It is possible to start Shorewall prior to networking but doing so limits the set of Shorewall features that can be used.
When Shorewall starts after networking, there is the possibility of unwanted connections being accepted between the time that an interface comes up and the time that Shorewall has finished starting up. Also, Shorewall has had no means of reacting when interfaces are brought up and down.
Beginning with Shorewall 4.4.10, a new package, Shorewall Init, is available. Shorewall Init serves two purposes:
It can 'close' the firewall before the network interfaces are brought up during boot.
It can change the firewall state as the result of interfaces being brought up or taken down.
These two features can be controlled independently. Shorewall Init can be used together with any combination of the other Shorewall packages. Shorewall-init works on RedHat-based, SuSE-based and Debian-based distributions.
When Shorewall-init is first installed, it does nothing until you configure it.
The configuration file is /etc/default/shorewall-init
on Debian-based systems and
/etc/sysconfig/shorewall-init otherwise. There are
two settings in the file:
Lists the Shorewall packages that you want to integrate with Shorewall-init.
Example: PRODUCTS="shorewall shorewall6"
When set to 1, enables integration with NetworkManager and the ifup/ifdown scripts.
To close your firewall before networking starts:
In the Shorewall-init configuration file, set PRODUCTS to the firewall products installed on your system.
Be sure that your current firewall script(s) (normally in
/var/lib/<product>/firewall) is(are)
compiled with the 4.4.10 compiler.
Shorewall and Shorewall6 users can execute these commands:
| shorewall compile |
| shorewall6 compile |
Shorewall-lite and Shorewall6-lite users can execute these commands on the administrative system:
shorewall export
firewall-name-or-ip-address |
shorewall6 export
firewall-name-or-ip-address |
That's all that is required.
To integrate with NetworkManager and ifup/ifdown, additional steps are required. You probably don't want to enable this feature if you run a link status monitor like FOOLSM.
In the Shorewall-init configuration file, set IFUPDOWN=1.
In your Shorewall interfaces file(s), set the
required option on any interfaces that must be up in
order for the firewall to start. At least one interface must have the
required or optional option if you
perform the next optional step.
Optional) -- If you have specified at least one
required or optional interface, you
can then disable automatic firewall startup at boot time. On Debian
systems, set startup=0 in
/etc/default/.
On other systems, use your service startup configuration tool
(chkconfig, insserv, ...) to disable startup.product
If your system uses Upstart as it's system initialization daemon, you should not disable startup. Upstart is standard on recent Ubuntu and Fedora releases and is optional on Debian.
The following actions occur when an interface comes up:
| FIREWALL STATE | INTERFACE | ACTION |
| Any | Required | start |
| stopped | Optional | start |
| started | Optional | enable |
| started | Any | restart |
The following actions occur when an interface goes down:
| FIREWALL STATE | INTERFACE | ACTION |
| Any | Required | stop |
| stopped | Optional | start |
| started | Optional | disable |
| started | Any | restart |
For optional interfaces, the
/var/lib/
files are maintained to reflect the state of the interface so that they
may be used by the standard isusable script. Please
note that the action is carried out using the current compiled script; the
configuration is not recompiled.product/interface.state
A new option has been added to shorewall.conf
and shorewall6.conf. The REQUIRE_INTERFACE option
determines the outcome when an attempt to start/restart/restore/refresh
the firewall is made and none of the optional interfaces are available.
With REQUIRE_INTERFACE=No (the default), the operation is performed. If
REQUIRE_INTERFACE=Yes, then the operation fails and the firewall is placed
in the stopped state. This option is suitable for a laptop with both
ethernet and wireless interfaces. If either come up, the firewall starts.
If neither comes up, the firewall remains in the stopped state.
Similarly, if an optional interface goes down and there are no optional interfaces remaining in the up state, then the firewall is stopped.
On Debian-based systems, during system shutdown the firewall is
opened prior to network shutdown (/etc/init.d/shorewall
stop performs a 'clear' operation rather than a 'stop'). This is
required by Debian standards. You can change this default behavior by
setting SAFESTOP=1 in /etc/default/shorewall
(/etc/default/shorewall6, ...).