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<articleinfo>
<title>Dynamic Zones</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2009</year>
<year>2013</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>
<section>
<title>Overview</title>
<para>There is sometimes a need to be able to define a zone whose members
are unknown at compile-time. For example, you may wish to require
authentication of internal users before allowing them access to the
internet. When a user is authenticated, the user's IP address is added to
the zone of users permitted web access.</para>
<para>Shorewall provides basic support for defining such zones. This
support is based on <ulink
url="http://ipset.netfilter.org/">ipset</ulink>. Most current
distributions have ipset, but you may need to install the <ulink
url="http://xtables-addons.sourceforge.net/">xtables-addons</ulink>
package.</para>
</section>
<section>
<title>Dynamic Zones</title>
<para>Prior to Shorewall 4.5.9, when multiple records for a zone appear in
<filename>/etc/shorewall/hosts</filename>, Shorewall would create a
separate ipset for each interface. This meant that an add or delete
command was required for each of the interface, when the address involved
was reachable via multiple interfaces.</para>
<para>Beginning with Shoreawll 4.5.9, it is possible to have a single
ipset shared among all interfaces. This also simplifies management of
dynamic zone contents for dynamic zones associated with only a single
interface.</para>
<para>The earlier implementation described below is still available in
these later releases.</para>
<section id="defining">
<title>Defining a Dynamic Zone</title>
<para>A dynamic zone is defined by specifying the <emphasis
role="bold">dynamic_shared</emphasis> option in the zones file and using
the <emphasis role="bold">dynamic</emphasis> keyword in the hosts
list.</para>
<para><filename>/etc/shorewall/zones</filename>:<programlisting>#NAME TYPE OPTIONS
net ipv4
rsyncok:loc ipv4 <emphasis role="bold">dynamic_shared</emphasis></programlisting><filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
loc eth0 - …
loc eth1 - …</programlisting>
<para><filename>/etc/shorewall/hosts</filename>:</para>
<programlisting>#ZONE HOSTS OPTIONS
rsyncok eth0:<emphasis role="bold">dynamic</emphasis>
rsyncok eth1:<emphasis role="bold">dynamic</emphasis></programlisting>
<para>When the <emphasis role="bold">dynamic_shared</emphasis> option is
specified, a single ipset is created; the ipset has the same name as the
zone.</para>
<para>In the above example, <emphasis role="bold">rsyncok</emphasis> is
a sub-zone of the single zone <emphasis role="bold">loc</emphasis>.
Making a dynamic zone a sub-zone of multiple other zones is also
supported.</para>
</section>
<section id="Adding">
<title>Adding a Host to a Dynamic Zone.</title>
<para>Adding a host to a dynamic zone is accomplished by adding the
host's IP address to the appropriate ipset. Shorewall provldes a command
for doing that:<blockquote>
<para><command>shorewall add</command> <replaceable>zone
address</replaceable> ...</para>
</blockquote></para>
<para>Example:</para>
<blockquote>
<para><command>shorewall add rsyncok 70.90.191.124</command></para>
</blockquote>
</section>
<section id="delete">
<title>Deleting a Host from a Dynamic Zone</title>
<para>Deleting a host from a dynamic zone is accomplished by removing
the host's IP address from the appropriate ipset. Shorewall provldes a
command for doing that:</para>
<blockquote>
<para><command>shorewall delete</command>
<replaceable>zone</replaceable> <replaceable>address</replaceable>
...</para>
</blockquote>
<para>Example:</para>
<blockquote>
<para><command>shorewall delete rsyncok 70.19.191.124</command></para>
</blockquote>
<para>The command can only be used when the ipset involved is of type
iphash. For other ipset types, the <command>ipset</command> command must
be used directly.</para>
</section>
<section id="listing">
<title>Listing the Contents of a Dynamic Zone</title>
<para>The shorewall show command may be used to list the current
contents of a dynamic zone.</para>
<blockquote>
<para><command>shorewall show dynamic</command>
<replaceable>zone</replaceable></para>
</blockquote>
<para>Example:</para>
<blockquote>
<programlisting><command>shorewall show dynamic rsyncok</command>
rsyncok:
70.90.191.122
70.90.191.124</programlisting>
</blockquote>
</section>
</section>
<section id="start-stop">
<title>Dynamic Zone Contents and Shorewall stop/start/restart</title>
<para>When SAVE_IPSETS=Yes in shorewall.conf, the contents of a dynamic
zone survive <command>shorewall stop/shorewall start</command> and
<command>shorewall restart</command>. During <command>shorewall
stop</command>, the contents of the ipsets are saved in the file
<filename>${VARDIR}/ipsets.save</filename> (usually
<filename>/var/lib/shorewall/ipsets.save</filename>). During
<command>shorewall start</command>, the contents of that file are restored
to the sets. During both <command>shorewall start</command> and
<command>shorewall restart</command>, any new ipsets required as a result
of a configuration change are added.</para>
</section>
</article>