shorewall_code/docs/Shorewall-perl.xml

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  <articleinfo>
    <title>Shorewall-perl</title>

    <authorgroup>
      <author>
        <firstname>Tom</firstname>

        <surname>Eastep</surname>
      </author>
    </authorgroup>

    <pubdate><?dbtimestamp format="Y/m/d"?></pubdate>

    <copyright>
      <year>2007</year>

      <year>2009</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 id="What">
    <title>Shorewall-perl - What is it?</title>

    <para>Shorewall-perl was released as a companion product to Shorewall in
    Shorewall 4.0.0.</para>

    <para>Shorewall-perl contained a re-implementation of the Shorewall
    compiler written in Perl. The advantages of using Shorewall-perl over
    Shorewall-shell (the shell-based compiler included in earlier Shorewall
    3.x releases) were:</para>

    <itemizedlist>
      <listitem>
        <para>The Shorewall-perl compiler was much faster.</para>
      </listitem>

      <listitem>
        <para>The script generated by the compiler used
        <command>iptables-restore</command> to instantiate the Netfilter
        configuration. So it ran much faster than the script generated by the
        Shorewall-shell compiler and did not stop new connections during
        <command>shorewall restart</command>.</para>
      </listitem>

      <listitem>
        <para>The Shorewall-perl compiler did more thorough checking of the
        configuration than the Shorewall-shell compiler did.</para>
      </listitem>

      <listitem>
        <para>The error messages produced by the compiler were better, more
        consistent and always included the file name and line number where the
        error was detected.</para>
      </listitem>

      <listitem>
        <para>Going forward, the Shorewall-perl compiler got all enhancements;
        the Shorewall-shell compilerl only got those enhancements that were
        easy to retrofit.</para>
      </listitem>
    </itemizedlist>

    <para>Beginning with Shorewall 4.3.5, Shorewall-perl is an integral part
    of Shorewall and support for Shorewall-shell has been discontinued.</para>
  </section>

  <section id="DownSide">
    <title>Shorewall-perl - The down side</title>

    <para>While there are significant advantages to using Shorewall-perl,
    there are also disadvantages.</para>

    <section id="Incompatibilities">
      <title>Incompatibilities</title>

      <para>There are a number of incompatibilities between the Shorewall-perl
      compiler and the earlier one.</para>

      <orderedlist>
        <listitem>
          <para>The Perl-based compiler requires multiport match in your
          kernel and iptables.</para>
        </listitem>

        <listitem>
          <para>BRIDGING=Yes is not supported. The kernel code necessary to
          support this option was removed in Linux kernel 2.6.20. <ulink
          url="bridge-Shorewall-perl.html">Alternative bridge support</ulink>
          is provided by Shorewall-perl.</para>
        </listitem>

        <listitem>
          <para>DYNAMIC_ZONES=Yes is not supported in Shorewall-perl 4.2.
          <ulink url="ipsets.html#Dynamic">Use an ipset </ulink>to define your
          dytnamic zones. In Shorewall 4.4, dynamic zone support based on
          ipsets was added to Shorewall.</para>
        </listitem>

        <listitem>
          <para>The BROADCAST column in the interfaces file is essentially
          unused if your kernel/iptables has Address Type Match support. If
          that support is present and you enter anything in this column but
          '-' or 'detect', you will receive a warning.</para>
        </listitem>

        <listitem>
          <para>The 'refresh' command is now similar to restart with the
          exceptions that:</para>

          <itemizedlist>
            <listitem>
              <para>The command fails if Shorewall is not running.</para>
            </listitem>

            <listitem>
              <para>A directory name cannot be specified in the
              command.</para>
            </listitem>

            <listitem>
              <para>The refresh command does not alter the Netfilter
              configuration except for the static blacklist (it also refreshes
              the mangle table, beginning with Shorewall 4.2.0).</para>
            </listitem>
          </itemizedlist>
        </listitem>

        <listitem id="Extensions">
          <para>With the shell-based compiler, extension scripts were copied
          into the compiled script and executed at run-time. In many cases,
          this approach doesn't work with Shorewall Perl because (almost) the
          entire rule set is built by the compiler. As a result,
          Shorewall-perl runs some extension scripts at compile-time rather
          than at run-time. Because the compiler is written in Perl, your
          extension scripts from earlier versions will no longer work.</para>

          <para>The following table summarizes when the various extension
          scripts are run:</para>

          <informaltable align="left" frame="none">
            <tgroup cols="3">
              <tbody>
                <row>
                  <entry><emphasis role="bold">Compile-time (Must be written
                  in Perl)</emphasis></entry>

                  <entry><emphasis role="bold">Run-time</emphasis></entry>

                  <entry><emphasis role="bold">Eliminated</emphasis></entry>
                </row>

                <row>
                  <entry>initdone</entry>

                  <entry>clear</entry>

                  <entry>continue</entry>
                </row>

                <row>
                  <entry>maclog</entry>

                  <entry>init</entry>

                  <entry></entry>
                </row>

                <row>
                  <entry>Per-chain (including those associated with
                  actions)</entry>

                  <entry>start</entry>

                  <entry></entry>
                </row>

                <row>
                  <entry></entry>

                  <entry>started</entry>

                  <entry></entry>
                </row>

                <row>
                  <entry></entry>

                  <entry>stop</entry>

                  <entry></entry>
                </row>

                <row>
                  <entry></entry>

                  <entry>stopped</entry>

                  <entry></entry>
                </row>

                <row>
                  <entry></entry>

                  <entry>tcclear</entry>

                  <entry></entry>
                </row>
              </tbody>
            </tgroup>
          </informaltable>

          <para>Compile-time extension scripts are executed using the Perl
          'eval `cat &lt;file&gt;`' mechanism. Be sure that each script
          returns a 'true' value; otherwise, the Shorewall-perl compiler will
          assume that the script failed and will abort the compilation.</para>

          <para>When a script is invoked, the <emphasis
          role="bold">$chainref</emphasis> scalar variable will usually hold a
          reference to a chain table entry.</para>

          <simplelist>
            <member><emphasis role="bold">$chainref-&gt;{name}</emphasis>
            contains the name of the chain</member>

            <member><emphasis role="bold">$chainref-&gt;{table}</emphasis>
            holds the table name</member>
          </simplelist>

          <para>To add a rule to the chain:</para>

          <simplelist>
            <member>add_rule $chainref,
            <replaceable>the-rule</replaceable></member>
          </simplelist>

          <para>Where</para>

          <simplelist>
            <member><replaceable>the rule</replaceable> is a scalar argument
            holding the rule text. Do not include "-A
            <replaceable>chain-name</replaceable>"</member>
          </simplelist>

          <para>Example:</para>

          <simplelist>
            <member>add_rule $chainref, '-j ACCEPT';</member>
          </simplelist>

          <para>To insert a rule into the chain:</para>

          <simplelist>
            <member>insert_rule $chainref, <replaceable>rulenum</replaceable>,
            <replaceable>the-rule</replaceable></member>
          </simplelist>

          <para>The log_rule_limit function works like it does in the shell
          compiler with three exceptions:</para>

          <itemizedlist>
            <listitem>
              <para>You pass the chain reference rather than the name of the
              chain.</para>
            </listitem>

            <listitem>
              <para>The commands are 'add' and 'insert' rather than '-A' and
              '-I'.</para>
            </listitem>

            <listitem>
              <para>There is only a single "pass as-is to iptables" argument
              (so you must quote that part)</para>
            </listitem>
          </itemizedlist>

          <para>Example:</para>

          <programlisting>    log_rule_limit
              'info' , 
              $chainref , 
              $chainref-&gt;{name},
              'DROP' , 
              '',    #Limit
              '' ,   #Log tag
              'add'
              '-p tcp ';         </programlisting>

          <para>Here is an example of an actual initdone script used with
          Shorewall 3.4:<programlisting>run_iptables -t mangle -I PREROUTING -p esp -j MARK --set-mark 0x50
run_iptables -t filter -I INPUT -p udp --dport 1701 -m mark --mark 0x50 -j ACCEPT
run_iptables -t filter -I OUTPUT -p udp --sport 1701 -j ACCEPT
</programlisting></para>

          <para>Here is the corresponding script used with
          Shorewall-perl:<programlisting>use Shorewall::Chains;

insert_rule $mangle_table-&gt;{PREROUTING}, 1, "-p esp -j MARK --set-mark 0x50";
insert_rule $filter_table-&gt;{INPUT},      1, "-p udp --dport 1701 -m mark --mark 0x50 -j ACCEPT";
insert_rule $filter_table-&gt;{OUTPUT},     1, "-p udp --sport 1701 -j ACCEPT";

1;</programlisting></para>

          <para>The initdone script is unique because the $chainref variable
          is not set before the script is called. The above script illustrates
          how the $mangle_table, $filter_table, and $nat_table references can
          be used to add or insert rules in arbitrary chains.</para>
        </listitem>

        <listitem>
          <para>The <filename>/etc/shorewall/tos</filename> file now has
          zone-independent SOURCE and DEST columns as do all other files
          except the rules and policy files.</para>

          <para>The SOURCE column may be one of the following:</para>

          <simplelist>
            <member>[<command>all</command>:]&lt;<replaceable>address</replaceable>&gt;[,...]</member>

            <member>[<command>all</command>:]&lt;<replaceable>interface</replaceable>&gt;[:&lt;<replaceable>address</replaceable>&gt;[,...]]</member>

            <member><command>$FW</command>[:&lt;<replaceable>address</replaceable>&gt;[,...]]</member>
          </simplelist>

          <para>The DEST column may be one of the following:</para>

          <simplelist>
            <member>[<command>all</command>:]&lt;<replaceable>address</replaceable>&gt;[,...]</member>

            <member>[<command>all</command>:]&lt;<replaceable>interface</replaceable>&gt;[:&lt;<replaceable>address</replaceable>&gt;[,...]]</member>
          </simplelist>

          <para>This is a permanent change. The old zone-based rules have
          never worked right and this is a good time to replace them. I've
          tried to make the new syntax cover the most common cases without
          requiring change to existing files. In particular, it will handle
          the tos file released with Shorewall 1.4 and earlier.</para>
        </listitem>

        <listitem id="SAVE_IPSETS">
          <para>Shorewall-perl insists that ipset names begin with a letter
          and be composed of alphanumeric characters and underscores (_). When
          used in a Shorewall configuration file, the name must be preceded by
          a plus sign (+) as with the shell-based compiler.</para>

          <para>From Shorewall-perl 4.0.0 - Shorewall 4.4.5, Shorewall was out
          of the ipset load/reload business with the exception of ipsets used
          for dynamic zones:</para>

          <blockquote>
            <para>With scripts generated by the Perl-based Compiler, the
            Netfilter rule set is never cleared. That means that there is no
            opportunity for Shorewall to load/reload your ipsets since that
            cannot be done while there are any current rules using
            ipsets.</para>

            <para>So:</para>

            <orderedlist numeration="upperroman">
              <listitem>
                <para>Your ipsets must be loaded before Shorewall starts. You
                are free to try to do that with the following code in
                <filename>/etc/shorewall/init (it works for me; your mileage
                may vary)</filename>:</para>

                <programlisting>if [ "$COMMAND" = start ]; then
    ipset -U :all: :all:
    ipset -U :all: :default:
    ipset -F
    ipset -X
    ipset -R &lt; /etc/shorewall/ipsets
fi</programlisting>

                <para>The file <filename>/etc/shorewall/ipsets</filename> will
                normally be produced using the <command>ipset -S</command>
                command. I have this in my<filename>
                /etc/shorewall/stop</filename> file:</para>

                <programlisting>if ipset -S &gt; /etc/shorewall/ipsets.tmp; then
    mv -f /etc/shorewall/ipsets /etc/shorewall/ipsets.bak
    mv /etc/shorewall/ipsets.tmp /etc/shorewall/ipsets
fi</programlisting>

                <para>The above extension scripts will work most of the time
                but will fail in a <command>shorewall stop</command> -
                <command>shorewall start</command> sequence if you use ipsets
                in your routestopped file (see below).</para>
              </listitem>

              <listitem>
                <para>Your ipsets may not be reloaded until Shorewall is
                stopped or cleared.</para>
              </listitem>

              <listitem>
                <para>If you specify ipsets in your routestopped file then
                Shorewall must be cleared in order to reload your
                ipsets.</para>
              </listitem>
            </orderedlist>

            <para>As a consequence, scripts generated by the Perl-based
            compiler will ignore <filename>/etc/shorewall/ipsets</filename>
            and will issue a warning if you set SAVE_IPSETS=Yes in
            <filename>shorewall.conf</filename>.</para>
          </blockquote>

          <para>Beginning with Shorewall 4.4.6 (and 4.5.3), SAVE_IPSETS=Yes is
          once again supported. See <ulink
          url="manpages/shorewall.conf.html">shorewall.conf</ulink>(5).</para>
        </listitem>

        <listitem>
          <para>Because the configuration files (with the exception of
          <filename>/etc/shorewall/params</filename>) are now processed by the
          Shorewall-perl compiler rather than by the shell, only the basic
          forms of Shell expansion ($variable and ${variable}) are supported.
          The more exotic forms such as ${variable:=default} are not
          supported. Both variables defined in /etc/shorewall/params and
          environmental variables (exported by the shell) can be used in
          configuration files.</para>
        </listitem>

        <listitem>
          <para>USE_ACTIONS=No is not supported. That option is intended to
          minimize Shorewall's footprint in embedded applications. As a
          consequence, Default Macros are not supported by
          Shorewall-perl.</para>
        </listitem>

        <listitem>
          <para>DELAYBLACKLISTLOAD=Yes is not supported. The entire rule set
          is atomically loaded with one execution of
          <command>iptables-restore</command>.</para>
        </listitem>

        <listitem>
          <para>MAPOLDACTIONS=Yes is not supported. People should have
          converted to using macros by now.</para>
        </listitem>

        <listitem>
          <para>The pre Shorewall-3.0 format of the zones file is not
          supported (IPSECFILE=ipsec); neither is the
          <filename>/etc/shorewall/ipsec</filename> file.</para>
        </listitem>

        <listitem>
          <para>BLACKLISTNEWONLY=No is not permitted with FASTACCEPT=Yes. This
          combination doesn't work in previous versions of Shorewall so the
          Perl-based compiler simply rejects it.</para>
        </listitem>

        <listitem>
          <para>Shorewall-perl has a single rule generator that is used for
          all rule-oriented files. This implementation enforces consistency of
          syntax between files.</para>

          <para>With shorewall-shell, there is a special syntax in the SOURCE
          column of /etc/shorewall/masq to designate "all traffic entering the
          firewall on this interface except...".</para>

          <para>Example:<programlisting>#INTERFACE       SOURCE                  ADDRESSES
eth0             eth1!192.168.4.9        ...</programlisting>Shorewall-perl
          uses syntax that is consistent with the rest of
          Shorewall:<programlisting>#INTERFACE       SOURCE                  ADDRESSES
eth0             eth1:!192.168.4.9       ...</programlisting></para>
        </listitem>

        <listitem>
          <para>The 'allowoutUPnP' built-in action is no longer supported. In
          kernel 2.6.14, the Netfilter team have removed support for '-m owner
          --owner-cmd' which that action depended on.</para>
        </listitem>

        <listitem>
          <para>The PKTTYPE option is ignored by Shorewall-perl.
          Shorewall-perl will use Address type match if it is available;
          otherwise, it will behave as if PKTTYPE=No had been
          specified.</para>
        </listitem>

        <listitem>
          <para>Shorewall-perl detects dead policy file entries that result
          when an entry is masked by an earlier more general entry.</para>

          <para>Example:</para>

          <programlisting>#SOURCE DEST     POLICY    LOG LEVEL
all     all      REJECT    info
loc     net      ACCEPT</programlisting>

          <para>Shorewall-shell silently accepts the above even though the
          loc-&gt;net policy is useless. Shorewall-perl generates a fatal
          compilation error.</para>
        </listitem>

        <listitem>
          <para>In the SOURCE column of the rules file, when an interface name
          is followed by a list of IP addresses, the behavior of
          Shorewall-perl differs from that of Shorewall-shell.</para>

          <para>Example:<programlisting>#ACTION SOURCE                                 DEST PROTO DEST
#                                                         PORT(S)
ACCEPT  loc:eth0:192.168.1.3,192.168.1.5       $FW  tcp   22</programlisting>With
          Shorewall-shell, this rule accepts SSH connection to the firewall
          from 192.168.1.3 through eth0 or from 192.168.1.5 through any
          interface. With Shorewall-perl, the rule accepts SSH connections
          through eth0 from 192.168.1.3 and through eth0 from 192.168.1.5.
          Shorewall-shell supports this syntax that gives the same result as
          Shorewall-perl.<programlisting>#ACTION SOURCE                                 DEST PROTO DEST
#                                                         PORT(S)
ACCEPT loc:eth0:192.168.1.3,eth0:192.168.1.5   $fw  tcp   22</programlisting>
          Shorewall-perl does not support this alternative syntax.</para>
        </listitem>

        <listitem>
          <para>Shorewall-perl gives a warning if a zone name is entered in
          the DEST column of a <firstterm>nonat</firstterm> rule. Nonat rules
          include:</para>

          <itemizedlist>
            <listitem>
              <para>DNAT-</para>
            </listitem>

            <listitem>
              <para>REDIRECT-</para>
            </listitem>

            <listitem>
              <para>NONAT</para>
            </listitem>
          </itemizedlist>

          <para>So rather than this:<programlisting>#ACTION            SOURCE             DEST             PROTO        DEST PORT(S)
DNAT-              net                loc:192.168.1.3  tcp          21</programlisting></para>

          <para>you instead want:<programlisting>#ACTION            SOURCE             DEST             PROTO        DEST PORT(S)
DNAT-              net                192.168.1.3      tcp          21</programlisting></para>
        </listitem>

        <listitem>
          <para>Supplying an interface name in the SOURCE column of
          /etc/shorewall/masq is deprecated as of Shorewall 4.4. Entering the
          name of an interface there will result in a compile-time
          warning:</para>

          <para>WARNING: Using an interface as the masq SOURCE requires the
          interface to be up and configured when Shorewall
          starts/restarts</para>

          <para>To avoid this warning, replace interface names by the
          corresponding network() in CIDR format (e.g.,
          192.168.144.0/24).</para>
        </listitem>
      </orderedlist>
    </section>

    <section id="PerlDep">
      <title>Dependence on Perl</title>

      <para>Shorewall-perl is dependent on Perl which has a large disk
      footprint. This makes Shorewall-perl less desirable in an embedded
      environment. The best way to work around this limitation is to install
      Shorewall-perl on an administrative system and employ Shorewall-lite on
      your embedded systems. Shorewall-perl will run on Windows under <ulink
      url="http://www.cygwin.com/">Cygwin</ulink> and on an <ulink
      url="http://www.apple.com/mac/">Apple MacIntosh</ulink> running OS X.
      Install from a shell prompt <ulink url="Install.htm">using the
      install.sh script</ulink>.</para>
    </section>
  </section>

  <section id="Install">
    <title>Installing Shorewall Version 4.0 or 4.2</title>

    <para>Shorewall 4.2 contains six packages, four of which are also included
    in Shorewall 4.0:</para>

    <itemizedlist>
      <listitem>
        <para><emphasis role="bold">Shorewall-shell</emphasis> - the old
        shell-based compiler and related components.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">Shorewall-perl</emphasis> - the new
        Perl-based compiler.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">Shorewall-common</emphasis> - the part of
        Shorewall common to both compilers.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">Shorewall-lite</emphasis>- same as the 3.4
        version of Shorewall Lite. Can run scripts generated by either
        Shorewall-perl or Shorewall-shell.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">Shorewall6</emphasis> - The utilities for
        creating and operating an Ipv6 firewall. Requires Shorewall-perl and
        Shorewall-common. Introduced in Shorewall 4.2.4.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">Shorewall6-lite</emphasis> - Ipv6
        equivalent of Shorewall Lite. Can run scripts generated by
        Shoreall-perl 4.2.4 and later.</para>
      </listitem>
    </itemizedlist>

    <para>If you upgrade to Shorewall Version 4.0 or 4.2, you must install
    Shorewall-shell and/or Shorewall-perl; in fact, if you are using the
    tarball for your installation, you must install Shorewall-shell and/or
    Shorewall-perl <emphasis role="bold">before</emphasis> you upgrade
    Shorewall. See the <ulink url="upgrade_issues.htm">upgrade issues</ulink>
    for details.</para>
  </section>

  <section id="CompilerSelection">
    <title>Compiler Selection (Shorewall 4.0-4.2)</title>

    <para>If you only install one compiler, then that compiler will be
    used.</para>

    <para>If you install both compilers, then the compiler actually used for
    IPv4 depends on the SHOREWALL_COMPILER setting in
    <filename>shorewall.conf</filename>.</para>

    <para>The value of this new option can be either 'perl' or 'shell'.</para>

    <para>If you add 'SHOREWALL_COMPILER=perl' to
    <filename>/etc/shorewall/shorewall.conf</filename> then by default, the
    new compiler will be used on the system. If you add it to
    <filename>shorewall.conf</filename> in a separate directory (such as a
    Shorewall-lite export directory) then the new compiler will only be used
    when you compile from that directory.</para>

    <para>If you only install one compiler, it is suggested that you do not
    set SHOREWALL_COMPILER.</para>

    <para>If both compilers are installed, you can select the compiler to use
    on the command line using the 'C option:<simplelist>
        <member>'-C shell' means use the shell compiler</member>

        <member>'-C perl' means use the perl compiler</member>
      </simplelist>The -C option overrides the setting in
    shorewall.conf.</para>

    <para>Example:<programlisting><command>shorewall restart -C perl</command></programlisting></para>

    <para>When the Shorewall-perl compiler has been selected, the
    <filename>params</filename> file is processed using the shell
    <option>-a</option> option which causes all variables set within the file
    to be exported automatically by the shell. The Shorewall-perl compiler
    uses the current environmental variables to perform variable expansion
    within the other Shorewall configuration files.</para>
  </section>

  <section id="Modules">
    <title>The Shorewall Perl Modules</title>

    <para>In Shorewall 4.4 and later, Shorewall's Perl modules are installed
    in /usr/share/shorewall/Shorewall and the names of the packages are of the
    form Shorewall::<firstterm>name</firstterm>. So by using this
    directive<programlisting>use lib '/usr/share/shorewall';</programlisting></para>

    <para>You can then load the modules via normal Perl use statements.</para>

    <section id="compiler.pl">
      <title>/usr/share/shorewall/compiler.pl</title>

      <para>While the compiler is normally run indirectly using
      /sbin/shorewall, it can be run directly as well.<programlisting><command>compiler.pl</command> [ <emphasis>option</emphasis> ... ] [ <emphasis>filename</emphasis> ]</programlisting></para>

      <para>If a <emphasis>filename</emphasis> is given, then the
      configuration will be compiled and the output placed in the named file.
      If <emphasis>filename</emphasis> is not given, then the configuration
      will simply be syntax checked.</para>

      <para>Options are:</para>

      <para><simplelist>
          <member><command>-v</command>&lt;<emphasis>verbosity</emphasis>&gt;</member>

          <member><command>--verbosity=</command>&lt;<emphasis>verbosity</emphasis>&gt;</member>
        </simplelist>The &lt;<emphasis>verbosity</emphasis>&gt; is a number
      between 0 and 2 and corresponds to the VERBOSITY setting in
      <filename>shorewall.conf</filename>. This setting controls the verbosity
      of the compiler itself.<note>
          <para>The VERBOSITY setting in the
          <filename>shorewall.conf</filename> file read by the compiler will
          determine the default verbosity for the compiled program.</para>
        </note><simplelist>
          <member><emphasis role="bold">-e</emphasis></member>

          <member><emphasis role="bold">--export</emphasis></member>
        </simplelist>If given, the configuration will be compiled for export
      to another system.<simplelist>
          <member><emphasis role="bold">-d</emphasis>
          &lt;<emphasis>directory</emphasis>&gt;</member>

          <member><emphasis
          role="bold">--directory=</emphasis>&lt;<emphasis>directory</emphasis>&gt;</member>
        </simplelist>If this option is omitted, the configuration in
      /etc/shorewall is compiled/checked. Otherwise, the configuration in the
      named directory will be compiled/checked.<simplelist>
          <member><emphasis role="bold">-t</emphasis></member>

          <member><emphasis role="bold">--timestamp</emphasis></member>
        </simplelist>If given, each progress message issued by the compiler
      and by the compiled program will be timestamped.<simplelist>
          <member><emphasis role="bold">--debug</emphasis></member>
        </simplelist>If given, when a warning or error message is issued, it
      is supplemented with a stack trace. Requires the Carp Perl
      module.<simplelist>
          <member><emphasis
          role="bold">--refresh=</emphasis>&lt;<emphasis>chainlist</emphasis>&gt;</member>
        </simplelist>If given, the compiled script's 'refresh' command will
      refresh the chains in the comma-separated
      &lt;<emphasis>chainlist</emphasis>&gt; rather than
      'blacklst'.<simplelist>
          <member><emphasis
          role="bold">--log</emphasis>=&lt;logfile&gt;</member>
        </simplelist></para>

      <para>If given, compiler will log to this file provider that
      --log_verbosity is &gt; -1.<simplelist>
          <member><emphasis
          role="bold">--log_verbosity</emphasis>=-1|0|1|2</member>
        </simplelist></para>

      <para>If given, controls the verbosity of logging to the log specified
      by the --log parameter.</para>

      <simplelist>
        <member><emphasis role="bold">--family=</emphasis>4|6</member>
      </simplelist>

      <para>Specifies whether an IPv4 or an IPv6 firewall is to be
      created.</para>

      <simplelist>
        <member><emphasis role="bold">--preview</emphasis></member>
      </simplelist>

      <para>Added in Shorewall 4.4.6. If no filename is given, this option
      causes the generated input to iptables-input to be displayed on standard
      output.</para>

      <para>Example (compiles the configuration in the current directory
      generating a script named 'firewall' and using VERBOSITY
      2).<programlisting><emphasis role="bold">/usr/share/shorewall/compiler.pl -v 2 -d . firewall</emphasis></programlisting><note>
          <para>The Perl-based compiler does not process
          <filename>/etc/shorewall/params</filename>. To include definitions
          in that file, you would need to do something like the
          following:<programlisting><command>. /usr/share/shorewall/lib.base  # In case /etc/shorewall/params does INCLUDE
set -a                           # Export all variables set in /etc/shorewall/params
. /etc/shorewall/params
set +a
/usr/share/compiler.pl ...</command></programlisting></para>
        </note></para>
    </section>

    <section id="Compiler">
      <title>Shorewall::Compiler</title>

      <para>To avoid a proliferation of parameters to
      Shorewall::Compiler::compile(), that function uses named parameters.
      Parameter names are:</para>

      <variablelist>
        <varlistentry>
          <term>script ('object' is also accepted but deprecated)</term>

          <listitem>
            <para>Output script file. If omitted or '', the configuration is
            syntax checked.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>directory</term>

          <listitem>
            <para>Directory. If omitted or '', configuration files are located
            using CONFIG_PATH. Otherwise, the directory named by this
            parameter is searched first.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>verbosity</term>

          <listitem>
            <para>Verbosity; range -1 to 2</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>timestamp</term>

          <listitem>
            <para>0|1 -- timestamp messages.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>debug</term>

          <listitem>
            <para>0|1 -- include stack trace in warning/error messages.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>export</term>

          <listitem>
            <para>0|1 -- compile for export.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>chains</term>

          <listitem>
            <para>List of chains to be reloaded by 'refresh'</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>log</term>

          <listitem>
            <para>File to log compiler messages to.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>log_verbosity</term>

          <listitem>
            <para>Log Verbosity; range -1 to 2.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>family</term>

          <listitem>
            <para>Address family: 4 or 6</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>preview</term>

          <listitem>
            <para>Added in Shorewall 4.4.6.l Preview the ruleset on standard
            output.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>Those parameters that are supplied must have defined values.
      Defaults are: <simplelist>
          <member>script '' ('check' command)</member>

          <member>directory ''</member>

          <member>verbosity 1</member>

          <member>timestamp 0</member>

          <member>debug 0</member>

          <member>export 0</member>

          <member>chains ''</member>

          <member>log ''</member>

          <member>log_verbosity -1</member>

          <member>family 4</member>
        </simplelist></para>

      <para>Example: <programlisting>use lib '/usr/share/shorewall/';
use Shorewall::Compiler;

compiler( script =&gt; '/root/firewall', log =&gt; '/root/compile.log', log_verbosity =&gt; 2 ); </programlisting></para>
    </section>

    <section id="Chains">
      <title>Shorewall::Chains</title>

      <para><programlisting>use lib '/usr/share/shorewall';
use Shorewall::Chains;

my $chainref1 = chain_new $table, $name1;
add_rule $chainref1, $rule;
insert_rule $chainref1, $ordinal, $rule;
my $chainref2 = new_manual_chain $name3;
my $chainref3 = ensure_manual_chain $name;
log_rule_limit $level, $chainref3, $name, $disposition, $limit, $tag, $command, $predicates;


my $chainref4 = $chain_table{$table}{$name};
my $chainref5 = $nat_table{$name};
my $chainref6 = $mangle_table{$name};
my $chainref7 = $filter_table{$name};</programlisting>Shorewall::Chains is
      Shorewall-perl's interface to iptables/netfilter. It creates a
      <firstterm>chain table</firstterm> (%chain_table) which is populated as
      the various tables are processed. The table (actually a hash) is
      two-dimensional with the first dimension being the Netfilter table name
      (raw, mangle, nat and filter) and the second dimension being the chain
      name. Each table is a hash reference -- the hash defines the attributes
      of the chain. See the large comment at the beginning of the module
      (<filename>/usr/share/shorewall-perl/Shorewall/Chains.pm</filename>).</para>

      <para>The module export the chain table along with three hash references
      into the table:<literal></literal></para>

      <variablelist>
        <varlistentry>
          <term>$nat_table</term>

          <listitem>
            <para>Reference to the 'nat' portion of the table
            ($chain_table{nat}). This is a hash whose key is the chain name.
            This variable is not set when an IPv6 firewall is being
            created.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$mangle_table</term>

          <listitem>
            <para>Reference to the 'mangle' portion of the table
            ($chain_table{mangle}). This is a hash whose key is the chain
            name.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$filter</term>

          <listitem>
            <para>Reference to the 'filter' portion of the table
            ($chain_table{filter}). This is a hash whose key is the chain
            name.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>You can create a new chain in any of the tables using <emphasis
      role="bold">new_chain()</emphasis>. Arguments to the function
      are:</para>

      <variablelist>
        <varlistentry>
          <term>$table</term>

          <listitem>
            <para>'nat', 'mangle', or 'filter'.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$name</term>

          <listitem>
            <para>Name of the chain to create.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>The function creates a hash at $chain_table{$table}{$name} and
      populates the hash with default values. A reference to the hash is
      returned.</para>

      <para>Each chain table entry includes a list of rules to be added to the
      chain. These rules are written to the iptables-restore input file when
      the resulting script is executed. To append a rule to that list, call
      <emphasis role="bold">add_rule()</emphasis>. Arguments are:</para>

      <variablelist>
        <varlistentry>
          <term>$chainref</term>

          <listitem>
            <para>A reference to the chain table entry.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$rule</term>

          <listitem>
            <para>The rule to add. Do not include the leading '-A ' in this
            argument -- it will be supplied by the function.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>To insert a rule into that list, call <emphasis
      role="bold">insert_rule()</emphasis>. Arguments are:</para>

      <variablelist>
        <varlistentry>
          <term>$chainref</term>

          <listitem>
            <para>A reference to the chain table entry.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$ordinal</term>

          <listitem>
            <para>The position of the inserted rule in the list. A value of 1
            inserts the rule at the head of the list, a value of 2 places the
            rule second in the list, and so on.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$rule</term>

          <listitem>
            <para>The rule to add. Do not include the leading '-I' in this
            argument -- it will be supplied by the function.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>To create a <ulink url="ManualChains.html">manual chain</ulink>,
      use the new_manual_chain() function. The function accepts a single
      argument which is the name of the chain. The function returns a
      reference to the resulting chain table entry.</para>

      <para>A companion function, <emphasis
      role="bold">ensure_manual_chain()</emphasis>, can be called when a
      manual chain of the desired name may have already been created. If a
      manual chain table entry with the passed name already exists, a
      reference to the chain table entry is returned. Otherwise, the function
      calls <emphasis role="bold">new_manual_chain()</emphasis> and returns
      the result.</para>

      <para>To create a logging rule, call <emphasis
      role="bold">log_rule_limit()</emphasis>. Arguments are:</para>

      <variablelist>
        <varlistentry>
          <term>$level</term>

          <listitem>
            <para>The log level. May be specified as a name or as a
            number.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$chainref</term>

          <listitem>
            <para>Chain table reference for the chain to which the rule is to
            be added.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$name</term>

          <listitem>
            <para>The chain name to be reported in the log message (see
            LOGFORMAT in <ulink
            url="manpages/shorewall.conf.html">shorewall.conf</ulink>(5)).</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$disposition</term>

          <listitem>
            <para>The disposition to be reported in the log message (see
            LOGFORMAT in <ulink
            url="manpages/shorewall.conf.html">shorewall.conf</ulink>(5)).</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$limit</term>

          <listitem>
            <para>Rate limiting match. If an empty string is passed, the
            LOGRATE/LOGBURST (<ulink
            url="manpages/shorewall.conf.html">shorewall.conf</ulink>(5)) is
            used.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$tag</term>

          <listitem>
            <para>Log tag.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$command</term>

          <listitem>
            <para>If 'add', append the log rule to the chain. If 'insert',
            then insert the rule at the beginning of the chain.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>$predicates</term>

          <listitem>
            <para>Any additional matches that are to be applied to the
            rule.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="Config">
      <title>Shorewall::Config</title>

      <para><programlisting>use lib '/usr/share/shorewall';
use Shorewall::Config;

warning message "This entry is bogus";
fatal_error "You have made an error";

progress_message  "This will only be seen if VERBOSITY &gt;= 2";
progress_message2 "This will only be seen if VERBOSITY &gt;= 1";
progress_message3 "This will be seen unless VERBOSITY &lt; 0";
</programlisting>The <emphasis role="bold">shorewall()</emphasis> function may
      be optionally included:<programlisting>use lib '/usr/share/shorewall';
use Shorewall::Config qw/shorewall/;

shorewall $config_file_entry;</programlisting>The Shorewall::Config module
      provides basic services to Shorewall-perl. By default, it exports the
      functions that produce progress messages and warning/error
      messages.</para>

      <para>To issue a warning message, call <emphasis
      role="bold">warning_message()</emphasis>. The single argument describes
      the warning.</para>

      <para>To raise a fatal error, call <emphasis
      role="bold">fatal_error()</emphasis>. Again, the single argument
      described the error.</para>

      <para>In both cases, the function will augment the warning/error with
      the current configuration file and line number, if any. <emphasis
      role="bold">fatal_error()</emphasis> raised an exception via either
      <emphasis role="bold">confess()</emphasis> or <emphasis
      role="bold">die()</emphasis>, depending on whether the debugging stack
      trace is enabled or not..</para>

      <para>The three 'progress message' functions conditionally produce
      output depending on the current verbosity setting.</para>

      <para>The <emphasis role="bold">shorewall()</emphasis> function is used
      by <ulink url="configuration_file_basics.htm#Embedded">embedded Perl
      scripts</ulink> to generate entries to be included in the current
      configuration file.</para>
    </section>
  </section>
</article>