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644 lines
26 KiB
XML
644 lines
26 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
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<article lang="en" status="">
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<!--$Id$-->
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<articleinfo>
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<title>Macros</title>
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<authorgroup>
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<author>
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<firstname>Tom</firstname>
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<surname>Eastep</surname>
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</author>
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<author>
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<firstname>Cristian</firstname>
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<surname>Rodríguez</surname>
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</author>
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</authorgroup>
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<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
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<copyright>
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<year>2005</year>
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<holder>Thomas M. Eastep</holder>
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</copyright>
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<legalnotice>
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<para>Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version
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1.2 or any later version published by the Free Software Foundation; with
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no Invariant Sections, with no Front-Cover, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled
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<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
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License</ulink></quote>.</para>
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</legalnotice>
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</articleinfo>
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<caution>
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<para><emphasis role="bold">This article applies to Shorewall 3.0 and
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later. If you are running a version of Shorewall earlier than Shorewall
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3.0.0 then please see the documentation for that
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release.</emphasis></para>
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</caution>
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<section id="Overview">
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<title>Overview of Shorewall Macros?</title>
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<para>Shorewall macros allow a symbolic name to be associated with a
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series of one or more iptables rules. The symbolic name may appear in the
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ACTION column of an <filename><ulink
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url="manpages/shorewall-rules.html">/etc/shorewall/rules</ulink></filename>
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file entry and in the TARGET column of an action in which case, the
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traffic matching that rules file entry will be passed to the series of
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iptables rules named by the macro.</para>
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<para>Macros can be thought of as templates. When a macro is invoked in an
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<filename>/etc/shorewall/rules</filename> entry, it may be qualified by a
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logging specification (log level and optionally a log tag). The presence
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of the log level/tag causes a modified series of rules to be generated in
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which each packet/rule match within the macro causes a log message to be
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generated.</para>
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<para>There are two types of Shorewall macros:</para>
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<orderedlist>
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<listitem>
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<para>Standard Macros. These macros are released as part of Shorewall.
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They are defined in macros.* files in <filename
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class="directory">/usr/share/shorewall</filename>. Each
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<filename>macros.*</filename> file has a comment at the beginning of
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the file that describes what the macro does. As an example, here is
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the definition of the <firstterm>SMB</firstterm> standard
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macro.</para>
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<programlisting>#
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# Shorewall 3.0 /usr/share/shorewall/macro.SMB
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#
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# Handle Microsoft SMB traffic. You need to invoke this macro in
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# both directions.
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#
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######################################################################################
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#TARGET SOURCE DEST PROTO DEST SOURCE RATE USER/
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# PORT PORT(S) LIMIT GROUP
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PARAM - - udp 135,445
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PARAM - - udp 137:139
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PARAM - - udp 1024: 137
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PARAM - - tcp 135,139,445
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#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
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<para>If you wish to modify one of the standard macros, do not modify
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the definition in /usr/share/shorewall. Rather, copy the file to
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<filename class="directory">/etc/shorewall</filename> (or somewhere
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else on your CONFIG_PATH) and modify the copy.</para>
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</listitem>
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<listitem>
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<para>User-defined Macros. These macros are created by end-users. They
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are defined in macros.* files in /etc/shorewall or in another
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directory listed in your CONFIG_PATH (defined in <ulink
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url="manpages/shorewall.conf.html">/etc/shorewall/shorewall.conf</ulink>).</para>
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</listitem>
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</orderedlist>
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<para>Most Standard Macros are <firstterm>parameterized</firstterm>. That
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means that you specify what you want to do (ACCEPT, DROP, REJECT, etc.)
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when you invoke the macro. The SMB macro shown above is parameterized
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(note PARAM in the TARGET column).</para>
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<para><emphasis role="bold">Shorewall versions prior to 4.2.0:</emphasis>
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When invoking a parameterized macro, you follow the name of the macro with
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a slash ("/") and the action that you want to substitute for PARAM.</para>
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<para>Example:</para>
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<blockquote>
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<para>/etc/shorewall/rules:</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMB/ACCEPT loc fw </programlisting>
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<para>The above is equivalent to coding the following series of
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rules:</para>
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<programlisting>#TARGET SOURCE DEST PROTO DEST PORT(s)
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ACCEPT loc fw udp 135,445
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ACCEPT loc fw udp 137:139
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ACCEPT loc fw udp 1024: 137
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ACCEPT loc fw tcp 135,139,445</programlisting>
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</blockquote>
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<para><emphasis role="bold">Shorewall versions 4.2.0 and later:</emphasis>
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When invoking a parameterized macro, you follow the name of the macro with
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the action that you want to substitute for PARAM enclosed in parentheses.
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The older syntax described above is still supported but is
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deprecated.</para>
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<para>Example:</para>
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<blockquote>
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<para>/etc/shorewall/rules:</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMB(ACCEPT) loc fw </programlisting>
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<para>The above is equivalent to coding the following series of
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rules:</para>
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<programlisting>#TARGET SOURCE DEST PROTO DEST PORT(s)
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ACCEPT loc fw udp 135,445
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ACCEPT loc fw udp 137:139
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ACCEPT loc fw udp 1024: 137
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ACCEPT loc fw tcp 135,139,445</programlisting>
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</blockquote>
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<para>Logging is covered in <link linkend="Logging">a following
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section</link>. The other columns are treated as follows:</para>
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<variablelist>
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<varlistentry>
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<term>SOURCE and DEST</term>
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<listitem>
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<para>If a value other than "-" appears in both the macro body and
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in the invocation of the macro, then the value in the invocation is
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examined and the appropriate action is taken (you will want to be
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running Shorewall 3.0.1 or later). If the value in the invocation
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appears to be an address (IP or MAC) or the name of an ipset, then
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it is placed after the value in the macro body. Otherwise, it is
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placed before the value in the macro body.</para>
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<para>Example 1:</para>
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<blockquote>
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<para>/etc/shorewall/macro.SMTP</para>
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<programlisting>#TARGET SOURCE DEST PROTO DEST PORT(S)
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PARAM - loc tcp 25</programlisting>
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<para>/etc/shorewall/rules (Shorewall 4.0):</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMTP/DNAT:info net 192.168.1.5</programlisting>
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<para>/etc/shorewall/rules (Shorewall 4.2.0 and later):</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMTP(DNAT):info net 192.168.1.5</programlisting>
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<para>This would be equivalent to coding the following directly in
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/etc/shorewall/rules</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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DNAT:info net loc:192.168.1.5 tcp 25</programlisting>
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</blockquote>
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<para>Example 2:</para>
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<blockquote>
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<para>/etc/shorewall/macro.SMTP</para>
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<programlisting>#TARGET SOURCE DEST PROTO DEST PORT(S)
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PARAM - 192.168.1.5 tcp 25</programlisting>
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<para>/etc/shorewall/rules (Shorewall 4.0)</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMTP/DNAT:info net loc</programlisting>
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<para>/etc/shorewall/rules (Shorewall 4.2.0 and later)</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMTP(DNAT):info net loc</programlisting>
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<para>This would be equivalent to coding the following directly in
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/etc/shorewall/rules</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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DNAT:info net loc:192.168.1.5 tcp 25</programlisting>
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</blockquote>
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<para>Beginning with Shorewall 3.1, you may also specify SOURCE or
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DEST in the SOURCE and DEST columns. This allows you to define
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macros that work in both directions.</para>
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<para>Example 3:</para>
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<blockquote>
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<para><filename>/etc/shorewall/macro.SMBBI</filename> (Note: there
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is already a macro like this released as part of Shorewall 3.1 and
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later):</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/
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# PORT PORT(S) DEST LIMIT GROUP
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PARAM - - udp 135,445
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PARAM - - udp 137:139
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PARAM - - udp 1024: 137
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PARAM - - tcp 135,139,445
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PARAM DEST SOURCE udp 135,445
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PARAM DEST SOURCE udp 137:139
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PARAM DEST SOURCE udp 1024: 137
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PARAM DEST SOURCE tcp 135,139,445
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#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
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<para>/etc/shorewall/rules (Shorewall 4.0):</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMBBI/ACCEPT loc fw</programlisting>
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<para>/etc/shorewall/rules (Shorewall 4.2.0 and later):</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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SMBBI(ACCEPT) loc fw</programlisting>
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<para>This would be equivalent to coding the following directly in
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/etc/shorewall/rules</para>
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<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
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ACCEPT loc fw udp 135,445
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ACCEPT loc fw udp 137:139
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ACCEPT loc fw udp 1024: 137
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ACCEPT loc fw tcp 135,139,445
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ACCEPT fw loc udp 135,445
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ACCEPT fw loc udp 137:139
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ACCEPT fw loc udp 1024: 137
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ACCEPT fw loc tcp 135,139,445</programlisting>
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</blockquote>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Remaining columns</term>
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<listitem>
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<para>Any value in the invocation replaces the value in the rule in
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the macro.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>One remaining restriction should be noted: macros that are invoked
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from actions cannot themselves invoke other actions.</para>
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</section>
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<section id="Default">
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<title>Default Macros</title>
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<para>Beginning with Shorewall release 3.4, Shorewall supports
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<firstterm>default macros</firstterm>; default macros perform the same
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function as <ulink url="???">default actions</ulink>. The DEFAULT_ACCEPT,
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DEFAULT_REJECT, DEFAULT_DROP and DEFAULT_QUEUE options in
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<filename>/etc/shorewall/shorewall.conf</filename> may specify the name of
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a macro. In that case, the rules in the macro will be traversed before the
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associated policy is applied.</para>
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<para>The value of the …_DEFAULT settings is interpreted as follows. If
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USE_ACTIONS=Yes in shorewall.conf, then the value is treated like the name
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of an action -- if that action is not found, then the value is treated
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like the name of a macro. If USE_ACTIONS=No, then the value is treated
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like the name of a macro. The special value "none" is always interpreted
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as "no default rules should be applied".</para>
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<para>Shorewall versions 3.4 and later include standard 'Reject' and
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'Drop' macros that are equivalent to the 'Reject' and 'Drop'
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actions.</para>
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<para>Default Macros are not supported by Shorewall-perl.</para>
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</section>
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<section id="Defining">
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<title>Defining your own Macros</title>
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<para>To define a new macro:</para>
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<orderedlist>
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<listitem>
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<para>Macro names must be valid shell variable names ((must begin with
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a letter and be composed of letters, digits and underscore characters)
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as well as valid Netfilter chain names.</para>
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</listitem>
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<listitem>
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<para>Copy /usr/share/shorewall/macro.template to
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<filename>/etc/shorewall/macro.MacroName</filename> (for example, if
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your new macro name is <quote>Foo</quote> then copy
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<filename>/usr/share/shorewall/macro.template</filename> to
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<filename>/etc/shorewall/macro.Foo</filename>).</para>
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</listitem>
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<listitem>
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<para>Now modify the new file to define the new macro.</para>
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</listitem>
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</orderedlist>
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<para>Columns in the macro.template file are as follows:</para>
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<itemizedlist>
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<listitem>
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<para>ACTION - ACCEPT, DROP, REJECT, DNAT, DNAT-, REDIRECT, CONTINUE,
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LOG, QUEUE, PARAM or an action name. Note that a macro may not invoke
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another macro.</para>
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<simplelist>
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<member>ACCEPT - allow the connection request</member>
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<member>ACCEPT+ - like ACCEPT but also excludes the connection from
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any subsequent DNAT[-] or REDIRECT[-] rules.</member>
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<member>NONAT - Excludes the connection from any subsequent DNAT[-]
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or REDIRECT[-] rules but doesn't generate a rule to accept the
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traffic.</member>
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<member>DROP - ignore the request</member>
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<member>REJECT - disallow the request and return an icmp unreachable
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or an RST packet.</member>
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<member>DNAT - Forward the request to another address (and
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optionally another port).</member>
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<member>DNAT- - Advanced users only. Like DNAT but only generates
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the DNAT iptables rule and not the companion ACCEPT rule.</member>
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<member>SAME - Similar to DNAT except that the port may not be
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remapped and when multiple server addresses are listed, all requests
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from a given remote system go to the same server.</member>
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<member>SAME- - Advanced users only. Like SAME but only generates
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the SAME iptables rule and not the companion ACCEPT rule.</member>
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<member>REDIRECT - Redirect the request to a local port on the
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firewall.</member>
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<member>REDIRECT- - Advanced users only. Like REDIRECT but only
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generates the REDIRECT iptables rule and not the companion ACCEPT
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rule.</member>
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<member>CONTINUE - (For experts only). Do not process any of the
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following rules for this (source zone,destination zone). If The
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source and/or destination If the address falls into a zone defined
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later in /etc/shorewall/zones, this connection request will be
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passed to the rules defined for that (those) zone(s).</member>
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<member>LOG - Simply log the packet and continue.</member>
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<member>QUEUE - Queue the packet to a user-space application such as
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ftwall (http://p2pwall.sf.net).</member>
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</simplelist>
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<para>The ACTION may optionally be followed by ":" and a syslog log
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level (e.g, REJECT:info or DNAT:debug). This causes the packet to be
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logged at the specified level.</para>
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</listitem>
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<listitem>
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<para>SOURCE - Source hosts to which the rule applies. A
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comma-separated list of subnets and/or hosts. Hosts may be specified
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by IP or MAC address; mac addresses must begin with <quote>~</quote>
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and must use <quote>-</quote> as a separator.</para>
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<para>Alternatively, clients may be specified by interface name. For
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example, eth1 specifies a client that communicates with the firewall
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system through eth1. This may be optionally followed by another colon
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(<quote>:</quote>) and an IP/MAC/subnet address as described above
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(e.g. eth1:192.168.1.5).</para>
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<para>May also contain 'DEST' as described above.</para>
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</listitem>
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<listitem>
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<para>DEST - Location of Server. Same as above with the exception that
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MAC addresses are not allowed.</para>
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<para>Unlike in the SOURCE column, you may specify a range of up to
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256 IP addresses using the syntax <<emphasis>first
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ip</emphasis>>-<<emphasis>last ip</emphasis>>.</para>
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<para>May also contain 'SOURCE' as described above.</para>
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</listitem>
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<listitem>
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<para>PROTO - Protocol - Must be <quote>tcp</quote>,
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<quote>udp</quote>, <quote>icmp</quote>, a number, or
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<quote>all</quote>.</para>
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</listitem>
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<listitem>
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<para>DEST PORT(S) - Destination Ports. A comma-separated list of Port
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names (from <filename>/etc/services</filename>), port numbers or port
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ranges; if the protocol is <quote>icmp</quote>, this column is
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interpreted as the destination icmp-type(s).</para>
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<para>A port range is expressed as <<emphasis>low
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port</emphasis>>:<<emphasis>high port</emphasis>>.</para>
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<para>This column is ignored if PROTOCOL = all but must be entered if
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any of the following fields are supplied. In that case, it is
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suggested that this field contain <quote>-</quote>.</para>
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<para>If your kernel contains multi-port match support, then only a
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single Netfilter rule will be generated if in this list and in the
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CLIENT PORT(S) list below:</para>
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<orderedlist>
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<listitem>
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<para>There are 15 or less ports listed.</para>
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</listitem>
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<listitem>
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<para>No port ranges are included.</para>
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</listitem>
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</orderedlist>
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<para>Otherwise, a separate rule will be generated for each
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port.</para>
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</listitem>
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<listitem>
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<para>SOURCE PORT(S) - Port(s) used by the client. If omitted, any
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source port is acceptable. Specified as a comma-separated list of port
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names, port numbers or port ranges.</para>
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<para>If you don't want to restrict client ports but need to specify
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an ADDRESS in the next column, then place "-" in this column.</para>
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<para>If your kernel contains multi-port match support, then only a
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single Netfilter rule will be generated if in this list and in the
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DEST PORT(S) list above:</para>
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<orderedlist>
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<listitem>
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<para>There are 15 or less ports listed.</para>
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</listitem>
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<listitem>
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<para>No port ranges are included.</para>
|
|
</listitem>
|
|
</orderedlist>
|
|
|
|
<para>Otherwise, a separate rule will be generated for each
|
|
port.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>RATE LIMIT - You may rate-limit the rule by placing a value in
|
|
this column:</para>
|
|
|
|
<para><programlisting> <<emphasis>rate</emphasis>>/<<emphasis>interval</emphasis>>[:<<emphasis>burst</emphasis>>]</programlisting>where
|
|
<<emphasis>rate</emphasis>> is the number of connections per
|
|
<<emphasis>interval</emphasis>> (<quote>sec</quote> or
|
|
<quote>min</quote>) and <<emphasis>burst</emphasis>> is the
|
|
largest burst permitted. If no <<emphasis>burst</emphasis>> is
|
|
given, a value of 5 is assumed. There may be no whitespace embedded in
|
|
the specification.</para>
|
|
|
|
<para><programlisting> Example: 10/sec:20</programlisting></para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>USER/GROUP - For output rules (those with the firewall as their
|
|
source), you may control connections based on the effective UID and/or
|
|
GID of the process requesting the connection. This column can contain
|
|
any of the following:</para>
|
|
|
|
<simplelist>
|
|
<member>[!]<<emphasis>user number</emphasis>>[:]</member>
|
|
|
|
<member>[!]<<emphasis>user name</emphasis>>[:]</member>
|
|
|
|
<member>[!]:<<emphasis>group number</emphasis>></member>
|
|
|
|
<member>[!]:<<emphasis>group name</emphasis>></member>
|
|
|
|
<member>[!]<<emphasis>user
|
|
number</emphasis>>:<<emphasis>group
|
|
number</emphasis>></member>
|
|
|
|
<member>[!]<<emphasis>user
|
|
name</emphasis>>:<<emphasis>group
|
|
number</emphasis>></member>
|
|
|
|
<member>[!]<<emphasis>user
|
|
inumber</emphasis>>:<<emphasis>group
|
|
name</emphasis>></member>
|
|
|
|
<member>[!]<<emphasis>user
|
|
name</emphasis>>:<<emphasis>group name</emphasis>></member>
|
|
|
|
<member>[!]+<<emphasis>program name</emphasis>> (Note: support
|
|
for this form was removed from Netfilter in kernel version
|
|
2.6.14).</member>
|
|
</simplelist>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Omitted column entries should be entered using a dash ("-:).</para>
|
|
|
|
<para>Example:</para>
|
|
|
|
<para><phrase><filename>/etc/shorewall/macro.LogAndAccept</filename></phrase><programlisting> LOG:info
|
|
ACCEPT</programlisting></para>
|
|
|
|
<para>To use your macro, in <filename>/etc/shorewall/rules</filename> you
|
|
might do something like:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
|
|
LogAndAccept loc $FW tcp 22</programlisting>
|
|
</section>
|
|
|
|
<section id="Logging">
|
|
<title>Macros and Logging</title>
|
|
|
|
<para>Specifying a log level in a rule that invokes a user- or
|
|
Shorewall-defined action will cause each rule in the macro to be logged
|
|
with the specified level (and tag).</para>
|
|
|
|
<para>The extent to which logging of macro rules occur is governed by the
|
|
following:</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>When you invoke a macro and specify a log level, only those
|
|
rules in the macro that have no log level will be changed to log at
|
|
the level specified at the action invocation.</para>
|
|
|
|
<para>Example:</para>
|
|
|
|
<para>/etc/shorewall/macro.foo</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
|
|
ACCEPT - - tcp 22
|
|
bar:info</programlisting>
|
|
|
|
<para>/etc/shorewall/rules:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
|
|
foo:debug $FW net</programlisting>
|
|
|
|
<para>Logging in the invoked 'foo' macro will be as if foo had been
|
|
defined as:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
|
|
ACCEPT:debug - - tcp 22
|
|
bar:info</programlisting>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If you follow the log level with "!" then logging will be at
|
|
that level for all rules recursively invoked by the macro.</para>
|
|
|
|
<para>Example:</para>
|
|
|
|
<para>/etc/shorewall/macro.foo</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
|
|
ACCEPT - - tcp 22
|
|
bar:info</programlisting>
|
|
|
|
<para>/etc/shorewall/rules:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
|
|
foo:debug! $FW net</programlisting>
|
|
|
|
<para>Logging in the invoked 'foo' macro will be as if foo had been
|
|
defined as:</para>
|
|
|
|
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
|
|
ACCEPT:debug - - tcp 22
|
|
bar:debug</programlisting>
|
|
</listitem>
|
|
</orderedlist>
|
|
</section>
|
|
|
|
<section id="ActionOrMacro">
|
|
<title>How do I know if I should create an Action or a Macro?</title>
|
|
|
|
<para>While actions and macros perform similar functions, in any given
|
|
case you will generally find that one is more appropriate than the
|
|
other.</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>You can not associate an Extension Script with a macro <ulink
|
|
url="Actions.html#Extension">the way that you can with an
|
|
Action</ulink>. So if you need access to iptables features not
|
|
directly supported by Shorewall then you must use an action.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Macros are expanded in-line while each action is its own chain.
|
|
So if there are a lot of rules involved in your new action/macro then
|
|
it is generally better to use an action than a macro. Only the packets
|
|
selected when you invoke the action are directed to the corresponding
|
|
chain. On the other hand, if there are only one or two rules involved
|
|
in what you want to do then a macro is more efficient.</para>
|
|
</listitem>
|
|
</orderedlist>
|
|
</section>
|
|
</article>
|