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shorewall_code/Shorewall-docs/shorewall_extension_scripts.xml
teastep 863bd01657 Misc doc changes
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@1122 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
2004-02-04 22:40:37 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<article>
<!--$Id$-->
<articleinfo>
<title>Extension Scripts</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate>2004-02-01</pubdate>
<copyright>
<year>2001-2004</year>
<holder>Thomas M. Eastep</holder>
</copyright>
<legalnotice>
<para>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
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation License</ulink></quote>.</para>
</legalnotice>
</articleinfo>
<para>Extension scripts are user-provided scripts that are invoked at
various points during firewall start, restart, stop and clear. The scripts
are placed in /etc/shorewall and are processed using the Bourne shell
<quote>source</quote> mechanism.</para>
<caution>
<orderedlist>
<listitem>
<para>Be sure that you actually need to use an extension script to do
what you want. Shorewall has a wide range of features that cover most
requirements.</para>
</listitem>
<listitem>
<para>DO NOT SIMPLY COPY RULES THAT YOU FIND ON THE NET INTO AN
EXTENSION SCRIPT AND EXPECT THEM TO WORK AND TO NOT BREAK SHOREWALL.
TO USE SHOREWALL EXTENSION SCRIPTS YOU MUST KNOW WHAT YOU ARE DOING
WITH RESPECT TO iptables/Netfilter</para>
</listitem>
</orderedlist>
</caution>
<para>The following scripts can be supplied:</para>
<itemizedlist>
<listitem>
<para>init -- invoked early in <quote>shorewall start</quote> and
<quote>shorewall restart</quote></para>
</listitem>
<listitem>
<para>start -- invoked after the firewall has been started or restarted.</para>
</listitem>
<listitem>
<para>stop -- invoked as a first step when the firewall is being
stopped.</para>
</listitem>
<listitem>
<para>stopped -- invoked after the firewall has been stopped.</para>
</listitem>
<listitem>
<para>clear -- invoked after the firewall has been cleared.</para>
</listitem>
<listitem>
<para>refresh -- invoked while the firewall is being refreshed but
before the common and/or blacklst chains have been rebuilt.</para>
</listitem>
<listitem>
<para>newnotsyn (added in version 1.3.6) -- invoked after the
<quote>newnotsyn</quote> chain has been created but before any rules
have been added to it.</para>
</listitem>
</itemizedlist>
<para><emphasis role="bold">If your version of Shorewall doesn&#39;t have
the file that you want to use from the above list, you can simply create the
file yourself.</emphasis> You can also supply a script with the same name as
any of the filter chains in the firewall and the script will be invoked
after the /etc/shorewall/rules file has been processed but before the
/etc/shorewall/policy file has been processed. The /etc/shorewall/common
file receives special treatment. If this file is present, the rules that it
defines will totally replace the default rules in the common chain. These
default rules are contained in the file /etc/shorewall/common.def which may
be used as a starting point for making your own customized file. Rather than
running iptables directly, you should run it using the function
run_iptables. Similarly, rather than running <quote>ip</quote> directly, you
should use run_ip. These functions accept the same arguments as the
underlying command but cause the firewall to be stopped if an error occurs
during processing of the command. If you decide to create
/etc/shorewall/common it is a good idea to use the following technique.</para>
<para>/etc/shorewall/common:</para>
<programlisting> &#60;add your rules here&#62;
. /etc/shorewall/common.def</programlisting>
<para>Using this technique allows you to add new rules while still getting
the benefit of the latest common.def file. Remember that
/etc/shorewall/common defines rules that are only applied if the applicable
policy is DROP or REJECT. These rules are NOT applied if the policy is
ACCEPT or CONTINUE</para>
</article>