shorewall_code/Shorewall/manpages/shorewall.conf.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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<refentry>
  <refmeta>
    <refentrytitle>shorewall.conf</refentrytitle>

    <manvolnum>5</manvolnum>

    <refmiscinfo>Configuration Files</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>shorewall.conf</refname>

    <refpurpose>Shorewall global configuration file</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>/etc/shorewall/shorewall.conf</command>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>/etc/shorewall6/shorewall6.conf</command>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>The IPv4 and IPv6 environments each have their own configuration.
    The IPv4 configuration resides in /etc/shorewall/ while the IPv6
    configuration resides in /etc/shorewall6/.</para>

    <para>The .conf files set options that apply to Shorewall and Shorewall6
    as a whole.</para>

    <para>The .conf files consist of Shell comments (lines beginning with
    '#'), blank lines and assignment statements
    (<emphasis>variable</emphasis>=<emphasis>value</emphasis>). If the
    <emphasis>value</emphasis> contains shell meta characters or white-space,
    then it must be enclosed in quotes. Example:
    MACLIST_LOG_LEVEL="NFLOG(1,0,1)".</para>
  </refsect1>

  <refsect1>
    <title>OPTIONS</title>

    <para>Many options have as their value a <emphasis>log-level</emphasis>.
    Log levels are a method of describing to syslog (8) the importance of a
    message and a number of parameters in this file have log levels as their
    value.</para>

    <para>These levels are defined by syslog and are used to determine the
    destination of the messages through entries in /etc/syslog.conf (5). The
    syslog documentation refers to these as "priorities"; Netfilter calls them
    "levels" and Shorewall also uses that term.</para>

    <para>Valid levels are:</para>

    <programlisting>       7       debug
       6       info
       5       notice
       4       warning
       3       err
       2       crit
       1       alert
       0       emerg</programlisting>

    <para>For most Shorewall logging, a level of 6 (info) is appropriate.
    Shorewall log messages are generated by NetFilter and are logged using
    facility 'kern' and the level that you specify. If you are unsure of the
    level to choose, 6 (info) is a safe bet. You may specify levels by name or
    by number.</para>

    <para>If you have built your kernel with ULOG (IPv4 only) and/or NFLOG
    target support, you may also specify a log level of ULOG and/or NFLOG
    (must be all caps). Rather than log its messages to syslogd, Shorewall
    will direct netfilter to log the messages via the ULOG or NFLOG target
    which will send them to a process called 'ulogd'. ulogd is available with
    most Linux distributions (although it probably isn't installed by
    default).</para>

    <note>
      <para>If you want to specify parameters to ULOG or NFLOG (e.g.,
      NFLOG(1,0,1)), then you must quote the setting.</para>

      <para>Example:</para>

      <programlisting>LOG_LEVEL="NFLOG(1,0,1)"</programlisting>
    </note>

    <para>Beginning with Shorewall 5.0.0, the log level may be followed by a
    colon (":") and a <firstterm>log tag</firstterm>. The log tag normally
    follows the packet disposition in Shorewall-generated Netfilter log
    messages, separated from the disposition by a colon (e.g, "DROP:mytag").
    See LOGTAGONLY below for additional information.</para>

    <para>Beginning with Shorewall 4.4.22, LOGMARK is also a valid level which
    logs the packet's mark value along with the other usual information. The
    syntax is:</para>

    <simplelist>
      <member><emphasis
      role="bold">LOGMARK[</emphasis><replaceable>(priority)</replaceable><emphasis
      role="bold">]</emphasis></member>
    </simplelist>

    <para>where <replaceable>priority</replaceable> is one of the levels
    listed in the list above. If omitted, the default is info (6).</para>

    <para>The following options may be set in shorewall.conf.</para>

    <variablelist>
      <varlistentry>
        <term><emphasis
        role="bold">ACCEPT_DEFAULT=</emphasis>{<emphasis>action</emphasis>[(<replaceable>parameters</replaceable>)][:<replaceable>level</replaceable>][,...]|<emphasis
        role="bold">none</emphasis>}</term>

        <listitem>
          <para/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">BLACKLIST_DEFAULT=</emphasis>{<emphasis>action</emphasis>[(<replaceable>parameters</replaceable>)][:<replaceable>level</replaceable>][,...]|<emphasis
        role="bold">none</emphasis>}</term>

        <listitem>
          <para/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">DROP_DEFAULT=</emphasis>{<emphasis>action</emphasis>[(<replaceable>parameters</replaceable>)][:<replaceable>level</replaceable>][,...]|<emphasis
        role="bold">none</emphasis>}</term>

        <listitem>
          <para/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">NFQUEUE_DEFAULT=</emphasis>{<emphasis>action</emphasis>[(<replaceable>parameters</replaceable>)][:<replaceable>level</replaceable>][,...]|<emphasis
        role="bold">none</emphasis>}</term>

        <listitem>
          <para/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">QUEUE_DEFAULT=</emphasis>{<emphasis>action</emphasis>[(<replaceable>parameters</replaceable>)][:<replaceable>level</replaceable>][,...]|<emphasis
        role="bold">none</emphasis>}</term>

        <listitem>
          <para/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">REJECT_DEFAULT=</emphasis>{<emphasis>action</emphasis>[(<replaceable>parameters</replaceable>)][:<replaceable>level</replaceable>][,...]|<emphasis
        role="bold">none</emphasis>}</term>

        <listitem>
          <para>In earlier Shorewall versions, a "<firstterm>default
          action</firstterm>" for DROP and REJECT policies was specified in
          the file /usr/share/shorewall/actions.std.</para>

          <para>In Shorewall 4.4.0, the DROP_DEFAULT, REJECT_DEFAULT,
          ACCEPT_DEFAULT, QUEUE_DEFAULT and NFQUEUE_DEFAULT options were
          added.</para>

          <para>DROP_DEFAULT describes the rules to be applied before a
          connection request is dropped by a DROP policy; REJECT_DEFAULT
          describes the rules to be applied if a connection request is
          rejected by a REJECT policy. The other three are similar for ACCEPT,
          QUEUE and NFQUEUE policies.</para>

          <para>The value applied to these may be:</para>

          <simplelist>
            <member>a) The name of an <replaceable>action</replaceable>. The
            name may optionally be followed by a comma-separated list of
            parameters enclosed in parentheses if the specified action accepts
            parameters (e.g., 'Drop(audit)').</member>

            <member>c) <emphasis role="bold">None</emphasis> or <emphasis
            role="bold">none</emphasis></member>
          </simplelist>

          <para>Prior to Shorewall 5.1.2, the default values are:</para>

          <simplelist>
            <member>DROP_DEFAULT="Drop"</member>

            <member>REJECT_DEFAULT="Reject"</member>

            <member>BLACKLIST_DEFAULT="Drop" (added in Shorewall
            5.1.1)</member>

            <member>ACCEPT_DEFAULT="none"</member>

            <member>QUEUE_DEFAULT="none"</member>

            <member>NFQUEUE_DEFAULT="none"</member>
          </simplelist>

          <para>Beginning with Shorewall 5.1.2, the default value is 'none'
          for all of these. Note that the sample configuration files do,
          however, provide settings for DROP_DEFAULT, BLACKLIST_DEFAULT and
          REJECT_DEFAULT.</para>

          <para>If you set the value of either option to "None" then no
          default action will be used and the default action or macro must be
          specified in <ulink
          url="shorewall-policy.html">shorewall-policy</ulink>(5).</para>

          <para>You can pass <replaceable>parameters</replaceable> to the
          specified action (e.g.,
          <emphasis>myaction(audit,DROP)</emphasis>).</para>

          <para>Beginning with Shorewall 4.5.10, the action name can be
          followed optionally by a colon and a log
          <replaceable>level</replaceable>. The level will be applied to each
          rule in the action or body that does not already have a log
          level.</para>

          <para>Beginning with Shorewall 5.1.2, multiple
          <replaceable>action</replaceable>[(<replaceable>parameters</replaceable>)][:<replaceable>level</replaceable>]
          specifications may be listed, separated by commas.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">ACCOUNTING=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.7. If set to Yes, Shorewall accounting
          is enabled (see <ulink
          url="shorewall-accounting.html">shorewall-accounting</ulink>(5)). If
          not specified or set to the empty value, ACCOUNTING=Yes is
          assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">ACCOUNTING_TABLE=</emphasis>[<emphasis
        role="bold">filter</emphasis>|<emphasis
        role="bold">mangle</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.20. This setting determines which
          Netfilter table the accounting rules are added in. By default,
          ACCOUNTING_TABLE=filter is assumed. See also <ulink
          url="shorewall-accounting.html">shorewall-accounting</ulink>(5).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">ADD_IP_ALIASES=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>This parameter determines whether Shorewall automatically adds
          the external address(es) in <ulink
          url="shorewall-nat.html">shorewall-nat</ulink>(5), and is only
          available in IPv4 configurations. If the variable is set to
          <emphasis role="bold">Yes</emphasis> or <emphasis
          role="bold">yes</emphasis> then Shorewall automatically adds these
          aliases. If it is set to <emphasis role="bold">No</emphasis> or
          <emphasis role="bold">no</emphasis>, you must add these aliases
          yourself using your distribution's network configuration
          tools.</para>

          <para>If this variable is not set or is given an empty value
          (ADD_IP_ALIASES="") then ADD_IP_ALIASES=Yes is assumed.</para>

          <warning>
            <para>Addresses added by ADD_IP_ALIASES=Yes are deleted and
            re-added during <emphasis role="bold">shorewall reload</emphasis>
            and <emphasis role="bold">shorewall restart</emphasis>. As a
            consequence, connections using those addresses may be
            severed.</para>
          </warning>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">ADD_SNAT_ALIASES=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>This parameter determines whether Shorewall automatically adds
          the SNAT ADDRESS in <ulink
          url="shorewall-masq.html">shorewall-masq</ulink>(5), and is only
          available in IPv4 configurations. If the variable is set to
          <emphasis role="bold">Yes</emphasis> or <emphasis
          role="bold">yes</emphasis> then Shorewall automatically adds these
          addresses. If it is set to <emphasis role="bold">No</emphasis> or
          <emphasis role="bold">no</emphasis>, you must add these addresses
          yourself using your distribution's network configuration
          tools.</para>

          <para>If this variable is not set or is given an empty value
          (ADD_SNAT_ALIASES="") then ADD_SNAT_ALIASES=No is assumed.</para>

          <warning>
            <para>Addresses added by ADD_SNAT_ALIASES=Yes are deleted and
            re-added during <emphasis role="bold">shorewall reload</emphasis>
            and <emphasis role="bold">shorewall restart</emphasis>. As a
            consequence, connections using those addresses may be
            severed.</para>
          </warning>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">ADMINISABSENTMINDED=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>The value of this variable affects Shorewall's stopped state.
          The behavior differs depending on whether <ulink
          url="shorewall-routestopped.html">shorewall-routestopped</ulink>(5)
          or <ulink
          url="shorewall-stoppedrules.html">shorewall-stoppedrules</ulink>(5)
          is used:</para>

          <variablelist>
            <varlistentry>
              <term>routestopped</term>

              <listitem>
                <para>When ADMINISABSENTMINDED=No, only traffic to/from those
                addresses listed in <filename>routestopped</filename> is
                accepted when Shorewall is stopped. When
                ADMINISABSENTMINDED=Yes, in addition to traffic to/from
                addresses in <filename>routestopped</filename>, connections
                that were active when Shorewall stopped continue to work and
                all new connections from the firewall system itself are
                allowed.</para>

                <para>Note that the routestopped file is not supported in
                Shorewall 5.0 and later versions.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>stoppedrules</term>

              <listitem>
                <para>All existing connections continue to work. To sever all
                existing connections when the firewall is stopped, install the
                conntrack utility and place the command <command>conntrack
                -F</command> in the stopped user exit
                (<filename>/etc/shorewall/stopped</filename>).</para>

                <para>If ADMINISABSENTMINDED=No, only new connections matching
                entries in <filename>stoppedrules</filename> are accepted when
                Shorewall is stopped. Response packets and related connections
                are automatically accepted.</para>

                <para>If ADMINISABSENTMINDED=Yes, in addition to connections
                matching entries in <filename>stoppedrules</filename>, all new
                connections from the firewall system itself are allowed when
                the firewall is stopped. Response packets and related
                connections are automatically accepted.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>If this variable is not set or is given the empty value then
          ADMINISABSENTMINDED=No is assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">ARPTABLES=</emphasis>[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.12 and available in IPv4 only. This
          parameter names the arptables executable to be used by Shorewall. If
          not specified or if specified as a null value, then the arptables
          executable located using the PATH option is used.</para>

          <para>Regardless of how the arptables utility is located (specified
          via arptables= or located via PATH), Shorewall uses the
          arptables-restore and arptables-save utilities from that same
          directory.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">AUTOCOMMENT=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Formerly named AUTO_COMMENT. If set, if there is not a current
          comment when a macro is invoked, the behavior is as if the first
          line of the macro file was "COMMENT &lt;macro name&gt;". If not
          specified, the AUTO_COMMENT option has a default value of
          'Yes'.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">AUTOHELPERS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.7. When set to <option>Yes</option>
          (the default), the generated ruleset will automatically associate
          helpers with applications that require them (FTP, IRC, etc.). When
          configuring your firewall on systems running kernel 3.5 or later, it
          is recommended that you:</para>

          <orderedlist>
            <listitem>
              <para>Set AUTOHELPERS=No.</para>
            </listitem>

            <listitem>
              <para>Modify the HELPERS setting (see below) to list the helpers
              that you need.</para>
            </listitem>

            <listitem>
              <para>Either:</para>

              <orderedlist numeration="loweralpha">
                <listitem>
                  <para>Modify <ulink
                  url="shorewall-conntrack.html">shorewall-conntrack</ulink>
                  (5) to only apply helpers where they are required; or</para>
                </listitem>

                <listitem>
                  <para>Specify the appropriate helper in the HELPER column in
                  <ulink url="shorewall-rules.html">shorewall-rules</ulink>
                  (5).</para>

                  <note>
                    <para>The macros for those applications requiring a helper
                    automatically specify the appropriate HELPER where
                    required.</para>
                  </note>
                </listitem>
              </orderedlist>
            </listitem>
          </orderedlist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">AUTOMAKE=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>|<option>recursive</option>|<replaceable>depth</replaceable>]</term>

        <listitem>
          <para>If set, the behavior of the <command>start</command>,
          <emphasis role="bold">reload</emphasis> and
          <command>restart</command> commands are changed; if no files in
          CONFIG_PATH (see below) have been changed since the last successful
          <command>start, reload</command> or <command>restart</command>
          command, then the compilation step is skipped and the compiled
          script that executed the last <command>start</command>, <emphasis
          role="bold">reload</emphasis> or <command>restart</command> command
          is used. If not specified, the default is AUTOMAKE=No.</para>

          <para>The setting of the AUTOMAKE option is ignored if the
          <command>start</command>, <emphasis role="bold">reload</emphasis> or
          <command>restart</command> command includes a directory name
          (e.g.,<command> shorewall restart
          /etc/shorewall.new</command>).</para>

          <para>When AUTOMAKE=Yes, each directory in the CONFIG_PATH was
          originally searched recursively for files newer than the compiled
          script. That was changed in Shorewall 5.1.10.2 such that only the
          listed directories themselves were searched. That broke some
          configurations that played tricks with embedded SHELL such as
          "<command>SHELL cat /etc/shorewall/rules.d/loc/*.rules".</command>
          Prior to 5.1.10.2, a change to a file in or adding a file to
          /etc/shorewall/rules.d/loc/ would trigger recompilation. Beginning
          with 5.1.10.2, such changes would not trigger recompilation.
          Beginning with Shorewall 5.2.0, the pre-5.1.10.2 behavior can be
          obtained by setting AUTOMAKE=recursive.</para>

          <para>Also beginning with Shorewall 5.2.0, AUTOMAKE may be set to a
          numeric <replaceable>depth</replaceable> which specifies how deeply
          each listed directory is to be searched. AUTOMAKE=1 only searches
          each directory itself and is equivalent to AUTOMAKE=Yes. AUTOMAKE=2
          will search each directory and its immediate sub-directories;
          AUTOMAKE=3 will search each directory, each of its immediate
          sub-directories, and each of their immediate sub-directories,
          etc.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">BALANCE_PROVIDERS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.1.1. When USE_DEFAULT_RT=Yes, this option
          determines whether the <option>balance</option> provider option (see
          <ulink
          url="shorewall-providers.html">shorewall-providers(5)</ulink>) is
          the default. When BALANCE_PROVIDERS=Yes, then the
          <option>balance</option> option is assumed unless the
          <option>fallback</option>, <option>loose</option>,
          <option>load</option> or <option>tproxy</option> option is
          specified. If this option is not set or is set to the empty value,
          then the default value is the value of USE_DEFAULT_RT.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">BASIC_FILTERS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall-4.6.0. When set to <emphasis
          role="bold">Yes</emphasis>, causes entries in <ulink
          url="shorewall-tcfilters.html">shorewall-tcfilters(5)</ulink> to
          generate a basic filter rather than a u32 filter. This setting
          requires the <firstterm>Basic Ematch</firstterm> capability in your
          kernel and iptables.</para>

          <note>
            <para>One of the advantages of basic filters is that ipset matches
            are supported in newer iproute2 and kernel versions. Because
            Shorewall cannot reliably detect this capability, use of basic
            filters is controlled by this option.</para>
          </note>

          <para>The default value is <emphasis role="bold">No</emphasis> which
          causes u32 filters to be generated.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">BLACKLIST=</emphasis>[{<emphasis
        role="bold">ALL</emphasis>|<emphasis
        role="bold"><replaceable>state</replaceable>[,...]</emphasis>}]</term>

        <listitem>
          <para>where state is one of NEW, ESTABLISHED, RELATED, INVALID,or
          UNTRACKED.</para>

          <para>Added in Shorewall 4.5.13 to replace the BLACKLISTNEWONLY
          option. Specifies the connection tracking states that are to be
          subject to blacklist screening. If BLACKLIST is not specified then
          the states subject to blacklisting are
          NEW,ESTABLISHED,INVALID,UNTRACKED.</para>

          <para>ALL sends all packets through the blacklist chains.</para>

          <para>Note: The ESTABLISHED state may not be specified if
          FASTACCEPT=Yes is specified.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">BLACKLIST_DISPOSITION=</emphasis>[<emphasis
        role="bold">DROP</emphasis>|A_DROP|<emphasis
        role="bold">REJECT|A_REJECT</emphasis>]</term>

        <listitem>
          <para>This parameter determines the disposition of packets from
          blacklisted hosts. It may have the value DROP if the packets are to
          be dropped or REJECT if the packets are to be replied with an ICMP
          port unreachable reply or a TCP RST (tcp only). If you do not assign
          a value or if you assign an empty value then DROP is assumed.</para>

          <para>A_DROP and A_REJECT are audited versions of DROP and REJECT
          respectively and were added in Shorewall 4.4.20. They require
          AUDIT_TARGET in the kernel and iptables.</para>

          <para>The BLACKLIST_DISPOSITION setting determines the disposition
          of packets sent to the <emphasis role="bold">blacklog</emphasis>
          target of <ulink url="shorewall-blrules.html">shorewall-blrules
          </ulink>(5), but otherwise does not affect entries in that
          file.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">BLACKLIST_LOG_LEVEL=</emphasis>[<emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]]</term>

        <listitem>
          <para>Formerly named BLACKLIST_LOGLEVEL. This parameter determines
          if packets from blacklisted hosts are logged and it determines the
          syslog level that they are to be logged at. Its value is a syslog
          level (Example: BLACKLIST_LOG_LEVEL=debug). If you do not assign a
          value or if you assign an empty value then packets from blacklisted
          hosts are not logged. The setting determines the log level of
          packets sent to the <emphasis role="bold">blacklog</emphasis> target
          of <ulink
          url="shorewall-blrules.html">shorewall-blrules</ulink>(5).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">CLAMPMSS=[</emphasis><emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>|<emphasis>value</emphasis>]</term>

        <listitem>
          <para>This parameter enables the TCP Clamp MSS to PMTU feature of
          Netfilter and is usually required when your internet connection is
          through PPPoE or PPTP. If set to <emphasis
          role="bold">Yes</emphasis> or <emphasis role="bold">yes</emphasis>,
          the feature is enabled. If left blank or set to <emphasis
          role="bold">No</emphasis> or <emphasis role="bold">no</emphasis>,
          the feature is not enabled.</para>

          <para><emphasis role="bold">Important</emphasis>: This option
          requires CONFIG_IP_NF_TARGET_TCPMSS in your kernel.</para>

          <para>You may also set CLAMPMSS to a numeric
          <emphasis>value</emphasis> (e.g., CLAMPMSS=1400). This will set the
          MSS field in TCP SYN packets going through the firewall to the
          <emphasis>value</emphasis> that you specify.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">CLEAR_TC=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>If this option is set to <emphasis role="bold">No</emphasis>
          then Shorewall won't clear the current traffic control rules during
          [<command>re</command>]<command>start</command> or
          <command>reload</command>. This setting is intended for use by
          people who prefer to configure traffic shaping when the network
          interfaces come up rather than when the firewall is started. If that
          is what you want to do, set TC_ENABLED=Yes and CLEAR_TC=No and do
          not supply an /etc/shorewall/tcstart file. That way, your traffic
          shaping rules can still use the “fwmark” classifier based on packet
          marking defined in <ulink
          url="shorewall-tcrules.html">shorewall-tcrules</ulink>(5). If not
          specified, CLEAR_TC=Yes is assumed.</para>

          <warning>
            <para>When you specify TC_ENABLED=shared (see below), then you
            should also specify CLEAR_TC=No.</para>
          </warning>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">COMPLETE=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.12. When you set this option to Yes,
          you are asserting that the configuration is complete so that your
          set of zones encompasses any hosts that can send or receive traffic
          to/from/through the firewall. This causes Shorewall to omit the
          rules that catch packets in which the source or destination IP
          address is outside of any of your zones. Default is No. It is
          recommended that this option only be set to Yes if:</para>

          <itemizedlist>
            <listitem>
              <para>You have defined an interface whose effective physical
              setting is '+'.</para>
            </listitem>

            <listitem>
              <para>That interface is assigned to a zone.</para>
            </listitem>

            <listitem>
              <para>You have no CONTINUE policies or rules.</para>
            </listitem>
          </itemizedlist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">CONFIG_PATH</emphasis>=[[:]<emphasis>directory</emphasis>[:<emphasis>directory</emphasis>]...]</term>

        <listitem>
          <para>Specifies where configuration files other than
          shorewall[6].conf may be found. CONFIG_PATH is specifies as a list
          of directory names separated by colons (":"). When looking for a
          configuration file:</para>

          <itemizedlist>
            <listitem>
              <para>If the command is "try" or a "&lt;configuration
              directory&gt;" was specified in the command (e.g.,
              <command>shorewall [-6] check ./gateway</command>) then the
              directory given in the command is searched first.</para>
            </listitem>

            <listitem>
              <para>Next, each directory in the CONFIG_PATH setting is
              searched in sequence.</para>
            </listitem>
          </itemizedlist>

          <para>If CONFIG_PATH is not given or if it is set to the empty value
          then the contents of /usr/share/shorewall/configpath are used. As
          released from shorewall.net, that file sets the CONFIG_PATH to
          /etc/shorewall:/usr/share/shorewall but your particular distribution
          may set it differently. See the output of shorewall show config for
          the default on your system.</para>

          <para>Beginning with Shorewall 5.1.10, the CONFIG_PATH setting may
          begin with a colon (":"), to signal that the first
          <replaceable>directory</replaceable> listed will be skipped if the
          user performing a compilation is not root or if the configuration is
          being compiled for export (-e option specified or if running one of
          the remote-* commands) . This prevents the compiler from looking in
          <filename>/etc/shorewall[6]</filename>/ when compilation is being
          done by a non-root user or if the generated script is to be sent to
          a remote firewall system.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DEFER_DNS_RESOLUTION=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.12. When set to 'Yes' (the default),
          DNS names are validated in the compiler and then passed on to the
          generated script where they are resolved by ip[6]tables-restore.
          This is an advantage if you use AUTOMAKE=Yes and the IP address
          associated with the DNS name is subject to change. When
          DEFER_DNS_RESOLUTION=No, DNS names are converted into IP addresses
          by the compiler. This has the advantage that when AUTOMAKE=Yes, the
          <command>start</command>, <emphasis role="bold">reload</emphasis>
          and <command>restart</command> commands will succeed even if no DNS
          server is reachable (assuming that the configuration hasn't changed
          since the compiled script was last generated).</para>

          <important>
            <para>When DEFER_DNS_RESOLUTION=No and AUTOMAKE=Yes and a DNS
            change makes it necessary to recompile an existing firewall
            script, the <option>-c</option> option must be used with the
            <command>reload</command> or <command>restart</command> command to
            force recompilation.</para>
          </important>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DELETE_THEN_ADD=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>If set to Yes (the default value), entries in the
          /etc/shorewall[6]/rtrules files cause an 'ip rule del' command to be
          generated in addition to an 'ip rule add' command. Setting this
          option to No, causes the 'ip rule del' command to be omitted.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DETECT_DNAT_IPADDRS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>IPv4 only.</para>

          <para>If set to <emphasis role="bold">Yes</emphasis> or <emphasis
          role="bold">yes</emphasis>, Shorewall will detect the first IP
          address of the interface to the source zone and will include this
          address in DNAT rules as the original destination IP address. If set
          to <emphasis role="bold">No</emphasis> or <emphasis
          role="bold">no</emphasis>, Shorewall will not detect this address
          and any destination IP address will match the DNAT rule. If not
          specified or empty, “DETECT_DNAT_IPADDRS=Yes” is assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DISABLE_IPV6=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>IPv4 only.</para>

          <para>If set to <emphasis role="bold">Yes</emphasis> or <emphasis
          role="bold">yes</emphasis>, IPv6 traffic to, from and through the
          firewall system is disabled. If set to <emphasis
          role="bold">No</emphasis> or <emphasis role="bold">no</emphasis>,
          Shorewall will take no action with respect to allowing or
          disallowing IPv6 traffic. If not specified or empty,
          “DISABLE_IPV6=No” is assumed.</para>

          <para>It is important to note that changing DISABLE_IPV6=Yes to
          DISABLE_IPV6=No does <emphasis>not</emphasis> enable IPV6. The
          recommended approach for enabling IPv6 on your system is:</para>

          <itemizedlist>
            <listitem>
              <para>Install, configure and start <ulink
              url="../IPv6Support.html">Shorewall6</ulink>.</para>
            </listitem>

            <listitem>
              <para>Change DISABLE_IPV6=Yes to DISABLE_IPV6=No in
              <filename>/etc/shorewall/shorewall.conf</filename>.</para>
            </listitem>

            <listitem>
              <para>Reload Shorewall</para>
            </listitem>
          </itemizedlist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DOCKER=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.0.6; IPv4 only. When set to
          <option>Yes</option>, the generated script will save
          Docker-generated rules before and restore them after executing the
          <command>start</command>, <command>stop</command>,
          <command>reload</command> and <command>restart</command> commands.
          If set to <option>No</option> (the default), the generated script
          will delete any Docker-generated rules when executing those
          commands. See<ulink url="../Docker.html">
          https://shorewall.org/Docker.html</ulink> for additional
          information.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">DOCKER_BRIDGE=</emphasis>[<emphasis>bridgename</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.2.4; IPv4 only. Specifies the name of the
          default Docker bridge. If not specified, the value 'docker0' is
          assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">DONT_LOAD=</emphasis>[<emphasis>module</emphasis>[,<emphasis>module</emphasis>]...]</term>

        <listitem>
          <para>Causes Shorewall to not load the listed kernel modules.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DYNAMIC_BLACKLIST=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>||<emphasis
        role="bold">ipset</emphasis>[<emphasis
        role="bold">-only</emphasis>][<replaceable>,option</replaceable>[,...]][:[<replaceable>setname</replaceable>][:<replaceable>log_level</replaceable>|:l<replaceable>og_tag</replaceable>]]]}</term>

        <listitem>
          <para>Added in Shorewall 4.4.7. When set to <emphasis
          role="bold">No</emphasis> or <emphasis role="bold">no</emphasis>,
          chain-based dynamic blacklisting using <command>shorewall [-6] [-l]
          drop</command>, <command>shorewall [-6] [-l] reject</command>,
          <command>shorewall logdrop</command> and <command>shorewall [-6]
          [-l] logreject</command> is disabled. Default is <emphasis
          role="bold">Yes</emphasis>. Beginning with Shorewall 5.0.8,
          ipset-based dynamic blacklisting using the <command>shorewall
          blacklist</command> command is also supported. The name of the set
          (<replaceable>setname</replaceable>) and the level
          (<replaceable>log_level</replaceable>), if any, at which blacklisted
          traffic is to be logged may also be specified. The default IPv4 set
          name is SW_DBL4 and the default IPv6 set name is SW_DBL6. The
          default log level is <option>none</option> (no logging). If
          <option>ipset-only</option> is given, then chain-based dynamic
          blacklisting is disabled just as if DYNAMIC_BLACKLISTING=No had been
          specified.</para>

          <para>Possible <replaceable>option</replaceable>s are:</para>

          <variablelist>
            <varlistentry>
              <term>src-dst</term>

              <listitem>
                <para>Normally, only packets whose source address matches an
                entry in the ipset are dropped. If <option>src-dst</option> is
                included, then packets whose destination address matches an
                entry in the ipset are also dropped.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>disconnect</option></term>

              <listitem>
                <para>The <option>disconnect</option> option was added in
                Shorewall 5.0.13 and requires that the conntrack utility be
                installed on the firewall system. When an address is
                blacklisted using the <command>blacklist</command> command,
                all connections originating from that address are
                disconnected. if the <option>src-dst</option> option was also
                specified, then all connections to that address are also
                disconnected.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>timeout</option>=<replaceable>seconds</replaceable></term>

              <listitem>
                <para>Added in Shorewall 5.0.13. Normally, Shorewall creates
                the dynamic blacklisting ipset with timeout 0 which means that
                entries are permanent. If you want entries in the set that are
                not accessed for a period of time to be deleted from the set,
                you may specify that period using this option. Note that the
                <command>blacklist</command> command can override the ipset's
                timeout setting.</para>

                <important>
                  <para>Once the dynamic blacklisting ipset has been created,
                  changing this option setting requires a complete restart of
                  the firewall; <command>shorewall [-6] restart</command> if
                  RESTART=restart, otherwise <command>shorewall [-6] [-l] stop
                  &amp;&amp; shorewall [-6] [-l] start</command></para>
                </important>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>log</term>

              <listitem>
                <para>Added in Shorewall 5.2.5. When specified, successful
                'blacklist' and 'allow' commands will log a message to the
                system log.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>noupdate</term>

              <listitem>
                <para>Added in Shorewall 5.2.5. Normally, once an address has
                been blacklisted, each time that a packet is received from the
                packet, the ipset's entry for the address is updated to reset
                the timeout to the value specifyed in the
                <option>timeout</option> option above. Setting the
                <option>noupdate</option> option, inhibits this resetting of
                the entry's timeout. This option is ignored when the
                <option>timeout</option> option is not specified.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>When ipset-based dynamic blacklisting is enabled, the contents
          of the blacklist will be preserved over
          <command>stop</command>/<command>reboot</command>/<command>start</command>
          sequences if SAVE_IPSETS=Yes, SAVE_IPSETS=ipv4 or if
          <replaceable>setname</replaceable> is included in the list of sets
          to be saved in SAVE_IPSETS.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">EXPAND_POLICIES=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Normally, when the SOURCE or DEST columns in
          shorewall-policy(5) contains 'all', a single policy chain is created
          and thes policy is enforced in that chain. For example, if the
          policy entry is<programlisting>#SOURCE DEST POLICY LOG
#                   LEVEL
net     all  DROP   info</programlisting>then the chain name is 'net-all'
          ('net2all if ZONE2ZONE=2) which is also the chain named in Shorewall
          log messages generated as a result of the policy. If
          EXPAND_POLICIES=Yes, then Shorewall will create a separate chain for
          each pair of zones covered by the policy. This makes the resulting
          log messages easier to interpret since the chain in the messages
          will have a name of the form 'a2b' where 'a' is the SOURCE zone and
          'b' is the DEST zone.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">EXPORTMODULES=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.17. When set to Yes when compiling for
          use by Shorewall Lite (<command>shorewall [-6]
          remote-start</command>, <command>shorewall [-6] remote-reload,
          shorewall [-6] remote-restart </command>or <command>shorewall [-6]
          export</command> commands), the compiler will copy the modules or
          helpers file from the administrative system into the script. When
          set to No or not specified, the compiler will not copy the modules
          or helpers file from <filename>/usr/share/shorewall[6]</filename>
          but will copy those found in another location on the
          CONFIG_PATH.</para>

          <para>When compiling for direct use by Shorewall, causes the
          contents of the local module or helpers file to be copied into the
          compiled script. When set to No or not set, the compiled script
          reads the file itself.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">FASTACCEPT=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Normally, Shorewall defers accepting ESTABLISHED/RELATED
          packets until these packets reach the chain in which the original
          connection was accepted. So for packets going from the 'loc' zone to
          the 'net' zone, ESTABLISHED/RELATED packets are ACCEPTED in the
          'loc-net' or 'loc2net' chain, depending on the setting of ZONE2ZONE
          (see below).</para>

          <para>If you set FASTACCEPT=Yes, then ESTABLISHED/RELATED packets
          are accepted early in the INPUT, FORWARD and OUTPUT chains. If you
          set FASTACCEPT=Yes then you may not include rules in the ESTABLISHED
          or RELATED sections of <ulink
          url="shorewall-rules.html">shorewall-rules</ulink>(5).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">FIREWALL</emphasis>=[<emphasis>dnsname-or-ip-address</emphasis>]</term>

        <listitem>
          <para>This option was added in Shorewall 5.0.13 and may be used on
          an administrative system in directories containing the
          configurations of remote firewalls. The contents of the variable are
          the default value for the <replaceable>system</replaceable>
          parameter to the <command>remote-start</command>,
          <command>remote-reload</command> and
          <command>remote-restart</command> commands.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">FORWARD_CLEAR_MARK=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Added in Shorewall 4.4.11. Traditionally, Shorewall has
          cleared the packet mark in the first rule in the mangle FORWARD
          chain. This behavior is maintained with the default setting of this
          option (FORWARD_CLEAR_MARK=Yes). If FORWARD_CLEAR_MARK is set to
          'No', packet marks set in the mangle PREROUTING chain are retained
          in the FORWARD chains.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">GEOIPDIR</emphasis>=[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.4. Specifies the pathname of the
          directory containing the <firstterm>GeoIP Match</firstterm>
          database. See <ulink
          url="../ISO-3661.html">https://shorewall.org/ISO-3661.html</ulink>.
          If not specified, the default value is
          <filename>/usr/share/xt_geoip/LE</filename> which is the default
          location of the little-endian database.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">HELPERS</emphasis>=[<emphasis>helper</emphasis>[,<replaceable>helper</replaceable>...]]</term>

        <listitem>
          <para>Added in Shorewall 4.5.7. This option specifies a
          comma-separated list naming the Netfilter application helpers that
          are to be enabled. If not specified, the default is to enable all
          helpers.</para>

          <para>Possible values for <replaceable>helper</replaceable>
          are:</para>

          <itemizedlist>
            <listitem>
              <para><emphasis role="bold">amanda</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">ftp</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">h323</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">irc</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">netbios-ns</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">none</emphasis> - This special value
              was added in Shorewall 4.5.16 and indicates that no helpers are
              to be enabled. It also prevents the compiler for probing for
              helper support; such probing generates messages on the system
              log of the form "xt_CT: No such helper XXX" where XXX is the
              helper name. When used, <emphasis role="bold">none</emphasis>
              must be the only helper specified.</para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">pptp</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">sane</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">sip</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">snmp</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">tftp</emphasis></para>
            </listitem>
          </itemizedlist>

          <para>When HELPERS is specified on a system running Kernel 3.5.0 or
          later, automatic association of helpers to connections is
          disabled.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">IGNOREUNKNOWNVARIABLES=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.11. Normally, if an unknown shell
          variable is encountered in a configuration file (except in ?IF and
          ?ELSIF directives), the compiler raises a fatal error. If
          IGNOREUNKNOWNVARIABLES is set to <emphasis
          role="bold">Yes</emphasis>, then such variables simply expand to an
          empty string. Default is <emphasis role="bold">No</emphasis>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">IMPLICIT_CONTINUE=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>When this option is set to <emphasis
          role="bold">Yes</emphasis>, it causes subzones to be treated
          differently with respect to policies.</para>

          <para>Subzones are defined by following their name with ":" and a
          list of parent zones (in <ulink
          url="shorewall-zones.html">shorewall-zones</ulink>(5)). Normally,
          you want to have a set of special rules for the subzone and if a
          connection doesn't match any of those subzone-specific rules then
          you want the parent zone rules and policies to be applied; see
          <ulink url="shorewall-nesting.html">shorewall-nesting</ulink>(5).
          With IMPLICIT_CONTINUE=Yes, that happens automatically.</para>

          <para>If IMPLICIT_CONTINUE=No or if IMPLICIT_CONTINUE is not set,
          then subzones are not subject to this special treatment. With
          IMPLICIT_CONTINUE=Yes, an implicit CONTINUE policy may be overridden
          by including an explicit policy (one that does not specify "all" in
          either the SOURCE or the DEST columns).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">INVALID_DISPOSITION=[A_DROP|A_REJECT|DROP|REJECT|CONTINUE]</emphasis></term>

        <listitem>
          <para>Added in Shorewall 4.5.13. Shorewall has traditionally passed
          INVALID packets through the NEW section of <ulink
          url="shorewall-rules.html">shorewall-rules</ulink> (5). When a
          packet in INVALID state fails to match any rule in the INVALID
          section, the packet is disposed of based on this setting. The
          default value is CONTINUE for compatibility with earlier
          versions.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">INVALID_LOG_LEVEL=</emphasis><emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.13. Packets in the INVALID state that
          do not match any rule in the INVALID section of <ulink
          url="shorewall-rules.html">shorewall-rules</ulink> (5) are logged at
          this level. The default value is empty which means no logging is
          performed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">IP</emphasis>=[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>If specified, gives the pathname of the 'ip' executable. If
          not specified, 'ip' is assumed and the utility will be located using
          the current PATH setting.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">IP_FORWARDING=</emphasis>[<emphasis
        role="bold">On</emphasis>|<emphasis
        role="bold">Off</emphasis>|<emphasis
        role="bold">Keep</emphasis>]</term>

        <listitem>
          <para>This IPv4 parameter determines whether Shorewall enables or
          disables IPv4 Packet Forwarding
          (<filename>/proc/sys/net/ipv4/ip_forward</filename>). In an IPv6
          configuration, this parameter determines the setting of
          <filename>/proc/sys/net/ipv6/config/all/ip_forwarding</filename>.</para>

          <para>Possible values are:</para>

          <variablelist>
            <varlistentry>
              <term><emphasis role="bold">On</emphasis> or <emphasis
              role="bold">on</emphasis></term>

              <listitem>
                <para>packet forwarding will be enabled.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">Off</emphasis> or <emphasis
              role="bold">off</emphasis></term>

              <listitem>
                <para>packet forwarding will be disabled.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">Keep</emphasis> or <emphasis
              role="bold">keep</emphasis></term>

              <listitem>
                <para>Shorewall will neither enable nor disable packet
                forwarding.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>If this variable is not set or is given an empty value
          (IP_FORWARD="") then IP_FORWARD=On is assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">IPSET</emphasis>=[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>If specified, gives the pathname of the 'ipset' executable. If
          not specified, 'ipset' is assumed and the utility will be located
          using the current PATH setting.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">IPSET_WARNINGS=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Added in Shorewall 4.5.2. Default is Yes. When set, causes the
          rules compiler to issue a warning when:</para>

          <itemizedlist>
            <listitem>
              <para>The compiler is being run by root and an ipset specified
              in the configuration does not exists. Only one warning is issued
              for each missing ipset.</para>
            </listitem>

            <listitem>
              <para>When [src] is specified in a destination column and when
              [dst] is specified in a source column.</para>
            </listitem>
          </itemizedlist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">IPTABLES=</emphasis>[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>IPv4 only.</para>

          <para>This parameter names the iptables executable to be used by
          Shorewall. If not specified or if specified as a null value, then
          the iptables executable located using the PATH option is
          used.</para>

          <para>Regardless of how the iptables utility is located (specified
          via IPTABLES= or located via PATH), Shorewall uses the
          iptables-restore and iptables-save utilities from that same
          directory.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">IP6TABLES=</emphasis>[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>IPv6 only.</para>

          <para>This parameter names the ip6tables executable to be used by
          Shorewall6. If not specified or if specified as a null value, then
          the ip6tables executable located using the PATH option is
          used.</para>

          <para>Regardless of how the ip6tables utility is located (specified
          via IP6TABLES= or located via PATH), Shorewall6 uses the
          ip6tables-restore and ip6tables-save utilities from that same
          directory.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">KEEP_RT_TABLES=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>IPv4:</para>

          <blockquote>
            <para>When set to <option>Yes</option>, this option prevents
            generated scripts from altering the /etc/iproute2/rt_tables
            database when there are entries in
            <filename>/etc/shorewall/providers</filename>. If you set this
            option to <option>Yes</option> while Shorewall (Shorewall-lite) is
            running, you should remove the file
            <filename>/var/lib/shorewall/rt_tables</filename>
            (<filename>/var/lib/shorewall-lite/rt_tables</filename>) before
            your next <command>stop</command>, <command>restore</command>,
            <emphasis role="bold">reload</emphasis> or
            <command>restart</command> command.</para>
          </blockquote>

          <para>IPv6:</para>

          <blockquote>
            <para>When set to <option>Yes</option>, this option prevents
            scripts generated by Shorewall6 from altering the
            /etc/iproute2/rt_tables database when there are entries in
            <filename>/etc/shorewall6/providers</filename>. If you set this
            option to <option>Yes</option> while Shorewall6 (Shorewall6-lite)
            is running, you should remove the file
            <filename>/var/lib/shorewall6/rt_tables</filename>
            (<filename>/var/lib/shorewall6-lite/rt_tables</filename>) before
            your next <command>stop</command>, <command>restore</command>,
            <emphasis role="bold">reload</emphasis> or
            <command>restart</command> command.</para>
          </blockquote>

          <important>
            <para>When both IPv4 and IPv6 Shorewall configurations are
            present, KEEP_RT_TABLES=No should be specified in only one of the
            two configurations unless the two provider configurations are
            identical with respect to interface and provider names and
            numbers.</para>
          </important>

          <para>The default is KEEP_RT_TABLES=No.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">LOAD_HELPERS_ONLY=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Added in Shorewall 4.4.7. When set to Yes, restricts the set
          of modules loaded by shorewall to those listed in
          <filename>/var/lib/shorewall[6]/helpers</filename> and those that
          are actually used. When not set, or set to the empty value,
          LOAD_HELPERS_ONLY=No is assumed in Shorewall versions 5.2.2 and
          earlier. Beginning with Shorewall 5.2.3, the LOAD_HELPERS_ONLY
          option is removed, and the behavior is as if LOAD_HELPERS_ONLY=Yes
          had been specified.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">LOCKFILE</emphasis>=[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>Specifies the name of the Shorewall[6] lock file, used to
          prevent simultaneous state-changing commands. If not specified,
          ${VARDIR}/shorewall[6]/lock is assumed (${VARDIR} is normally
          /var/lib but can be changed when Shorewall-core is installed -- see
          the output of <command>shorewall show vardir</command>).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">LOG_BACKEND=</emphasis>[<emphasis>backend</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.6.4. LOG_BACKEND determines the logging
          backend to be used for the <command>iptrace</command> command (see
          <ulink url="shorewall.html">shorewall(8)</ulink>).</para>

          <para><replaceable>backend</replaceable> is one of:</para>

          <variablelist>
            <varlistentry>
              <term>LOG</term>

              <listitem>
                <para>Use standard kernel logging.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>ULOG</term>

              <listitem>
                <para>IPv4 only.</para>

                <para>Use ULOG logging to ulogd.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>netlink</term>

              <listitem>
                <para>Use netlink logging to ulogd version 2 or later.</para>
              </listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">LOG_ZONE=</emphasis>[<emphasis
        role="bold"><option>src</option>|<option>dst</option>|<option>both</option></emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.2.0. When a log message is issued from a
          chain that relates to a pair of zones (e.g, 'fw-net'), the chain
          name normally appears in the log message (unless LOGTAGONLY=Yes and
          a log tag is specified). This can prevent OPTIMIZE category 8 from
          combining chains which are identical except for the names of the
          zones involved. LOG_ZONE allows for only the source or destination
          zone to appear in the messages by setting LOG_ZONE to
          <option>src</option> or <option>dest</option> respectively. If
          LOG_ZONE=<option>both</option> (the default), then the full chain
          name is included in log messages.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">LOG_LEVEL=</emphasis><emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 5.1.2. Beginning with that release, the
          sample configurations use this as the default log level and changing
          it will change all packet logging done by the configuration. In any
          configuration file (except <ulink
          url="shorewall-params.html">shorewall-params(5)</ulink>), $LOG_LEVEL
          will expand to this value.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">LOG_MARTIANS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>|Keep]</term>

        <listitem>
          <para>IPv4 only.</para>

          <para>If set to <emphasis role="bold">Yes</emphasis> or <emphasis
          role="bold">yes</emphasis>, sets
          <filename>/proc/sys/net/ipv4/conf/*/log_martians</filename> to 1
          with the exception of
          <filename>/proc/sys/net/ipv4/conf/all/log_martians which is set to
          0</filename>. The default value is <emphasis
          role="bold">Yes</emphasis> which sets both of the above to one. If
          you do not enable martian logging for all interfaces, you may still
          enable it for individual interfaces using the <emphasis
          role="bold">logmartians</emphasis> interface option in <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5).</para>

          <para>The value <emphasis role="bold">Keep</emphasis> causes
          Shorewall to ignore the option. If the option is set to <emphasis
          role="bold">Yes</emphasis>, then martians are logged on all
          interfaces. If the option is set to <emphasis
          role="bold">No</emphasis>, then martian logging is disabled on all
          interfaces except those specified in <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">LOG_VERBOSITY=</emphasis>[<emphasis>number</emphasis>]</term>

        <listitem>
          <para>This option controls the amount of information logged to the
          file specified in the STARTUP_LOG option.</para>

          <para>Values are:</para>

          <simplelist>
            <member>-1 - Logging is disabled</member>

            <member>0 - Silent. Only error messages are logged.</member>

            <member>1 - Major progress messages logged.</member>

            <member>2 - All progress messages logged</member>
          </simplelist>

          <para>If not specified, then -1 is assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">LOGALLNEW=</emphasis>[<emphasis>log-level</emphasis>]</term>

        <listitem>
          <para>This option is intended for use as a debugging aid. When set
          to a log level, this option causes Shorewall to generate a logging
          rule as the first rule in each builtin chain.</para>

          <itemizedlist>
            <listitem>
              <para>The table name is used as the chain name in the log
              prefix.</para>
            </listitem>

            <listitem>
              <para>The chain name is used as the target in the log
              prefix.</para>
            </listitem>
          </itemizedlist>

          <blockquote>
            <para>For example, using the default LOGFORMAT, the log prefix for
            logging from the nat table's PREROUTING chain is as follows in
            versions prior to 5.1.0:</para>

            <programlisting>    Shorewall:nat:PREROUTING
 </programlisting>

            <para>In Shorewall 5.1.0 and later releases, the log prefix
            is:</para>

            <programlisting>    nat:PREROUTING
 </programlisting>

            <important>
              <para>To help insure that all packets in the NEW state are
              logged, rate limiting (LOGLIMIT) should be disabled when using
              LOGALLNEW. Use LOGALLNEW at your own risk; it may cause high CPU
              and disk utilization and you may not be able to control your
              firewall after you enable this option.</para>
            </important>

            <para/>

            <caution>
              <para>Do not use this option if the resulting log messages will
              be sent to another system.</para>
            </caution>
          </blockquote>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">LOGFILE=</emphasis>[<emphasis>pathname</emphasis>|<option>systemd</option>]</term>

        <listitem>
          <para>This parameter tells the /sbin/shorewall program where to look
          for Shorewall messages when processing the <emphasis
          role="bold">dump</emphasis>, <emphasis
          role="bold">logwatch</emphasis>, <emphasis role="bold">show
          log</emphasis>, and <emphasis role="bold">hits</emphasis> commands.
          If not assigned or if assigned an empty value, /var/log/messages is
          assumed. For further information, see <ulink
          url="shorewall-logging.html">shorewall-logging(8)</ulink>. Beginning
          with Shorewall 5.0.10.1, you may specify <option>systemd</option> to
          use <command>journelctl -r</command> to read the log.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">LOGFORMAT=</emphasis>[<emphasis
        role="bold">"</emphasis><emphasis>formattemplate</emphasis><emphasis
        role="bold">"</emphasis>]</term>

        <listitem>
          <para>The value of this variable generate the --log-prefix setting
          for Shorewall logging rules. It contains a “printf” formatting
          template which accepts three arguments (the chain name, logging rule
          number (optional) and the disposition). To use LOGFORMAT with
          fireparse, set it as:</para>

          <programlisting>    LOGFORMAT="fp=%s:%d a=%s "</programlisting>

          <para>If the LOGFORMAT value contains the substring “%d” then the
          logging rule number is calculated and formatted in that position; if
          that substring is not included then the rule number is not included.
          If not supplied or supplied as empty (LOGFORMAT="") then
          “Shorewall:%s:%s:” is assumed.</para>

          <note>
            <para>The setting of LOGFORMAT has an effect of the permitted
            length of zone names. See <ulink
            url="shorewall-zones.html">shorewall-zones</ulink> (5).</para>
          </note>

          <caution>
            <para>Beginning with Shorewall 5.1.0, the default and sample
            shorewall[6].conf files set LOGFORMAT="%s %s ".</para>

            <para>Regardless of the LOGFORMAT setting, Shorewall IPv4 log
            messages that use this LOGFORMAT can be uniquely identified using
            the following regular expression:</para>

            <simplelist>
              <member>'IN=.* OUT=.* SRC=.*\..* DST='</member>
            </simplelist>

            <para>and Shorewall IPv6 log messages can be uniquely identified
            using the following regular expression:</para>

            <simplelist>
              <member>'IN=.* OUT=.* SRC=.*:.* DST='</member>
            </simplelist>

            <para>To match all Netfilter log messages (Both IPv4 and IPv6 and
            regardless of the LOGFORMAT setting), use:</para>

            <simplelist>
              <member>'IN=.* OUT=.* SRC=.* DST='</member>
            </simplelist>
          </caution>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">LOGLIMIT=[</emphasis>[{<emphasis>s</emphasis>|<emphasis
        role="bold">d</emphasis>}:]<emphasis>rate</emphasis><emphasis
        role="bold">/</emphasis>{<emphasis
        role="bold">sec</emphasis>|<emphasis
        role="bold">second|min</emphasis>|<emphasis
        role="bold">minute|hour</emphasis>|<emphasis
        role="bold">day</emphasis>}[:<emphasis>burst</emphasis>]]</term>

        <listitem>
          <para>Added in Shorewall 4.4.12. Limits the logging rate, either
          overall, or by source or destination IP address.</para>

          <para>If the value starts with 's:' then logging is limited per
          source IP. If the value starts with 'd:', then logging is limited
          per destination IP. Otherwise, the overall logging rate is
          limited.</para>

          <para>If <replaceable>burst</replaceable> is not specified, then a
          value of 5 is assumed.</para>

          <para>The keywords <emphasis role="bold">second</emphasis> and
          <emphasis role="bold">minute</emphasis> are accepted beginning with
          Shorewall 4.6.13.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">LOGTAGONLY=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Using LOGFORMAT=“Shorewall:%s:%s:”, chain names may not exceed
          5 characters or truncation of the log prefix may occur. Longer chain
          names may be used with log tags if you set LOGTAGONLY=Yes. With
          LOGTAGONLY=Yes, if a log tag is specified then the tag is included
          in the log prefix in place of the chain name.</para>

          <para>Beginning with Shorewall 4.5.12, when LOGTAGONLY=Yes, you have
          more control over the generated log prefix. Beginning with that
          release, the tag is interpreted as a <replaceable>chain
          name</replaceable> and a <replaceable>disposition</replaceable>
          separated by a comma. So this rule:</para>

          <programlisting>#ACTION                                SOURCE         DEST
LOG:info:foo,bar                       net            fw</programlisting>

          <para>would generate the following log prefix when using
          LOGFORMAT=“Shorewall:%s:%s:”:</para>

          <simplelist>
            <member>Shorewall:foo:bar:</member>
          </simplelist>

          <para>Similarly,</para>

          <programlisting>#ACTION                               SOURCE            DEST
LOG:info:,bar                        net                    fw</programlisting>

          <para>would generate</para>

          <simplelist>
            <member>Shorewall:net2fw:bar:</member>
          </simplelist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">MACLIST_DISPOSITION=</emphasis>[<emphasis
        role="bold">ACCEPT</emphasis>|<emphasis
        role="bold">DROP</emphasis>|<emphasis
        role="bold">REJECT</emphasis>|A_DROP|A_REJECT]</term>

        <listitem>
          <para>Determines the disposition of connections requests that fail
          MAC Verification and must have the value ACCEPT (accept the
          connection request anyway), REJECT (reject the connection request)
          or DROP (ignore the connection request). If not set or if set to the
          empty value (e.g., MACLIST_DISPOSITION="") then
          MACLIST_DISPOSITION=REJECT is assumed.</para>

          <para>A_DROP and A_REJECT are audited versions of DROP and REJECT
          respectively and were added in Shorewall 4.4.20. They require
          AUDIT_TARGET in the kernel and ip[6]tables.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">MACLIST_LOG_LEVEL=</emphasis>[<emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]]</term>

        <listitem>
          <para>Determines the syslog level for logging connection requests
          that fail MAC Verification. The value must be a valid syslogd log
          level. If you don't want to log these connection requests, set to
          the empty value (e.g., MACLIST_LOG_LEVEL="").</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">MACLIST_TABLE=</emphasis>[<emphasis
        role="bold">filter</emphasis>|<emphasis
        role="bold">mangle</emphasis>]</term>

        <listitem>
          <para>Normally, MAC verification occurs in the filter table (INPUT
          and FORWARD) chains. When forwarding a packet from an interface with
          MAC verification to a bridge interface, that doesn't work.</para>

          <para>This problem can be worked around by setting
          MACLIST_TABLE=mangle which will cause Mac verification to occur out
          of the PREROUTING chain. Because REJECT isn't available in that
          environment, you may not specify MACLIST_DISPOSITION=REJECT or
          MACLIST_DISPOSITION=A_REJECT with MACLIST_TABLE=mangle.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">MACLIST_TTL=[</emphasis><emphasis>number</emphasis>]</term>

        <listitem>
          <para>The performance of configurations with a large numbers of
          entries in <ulink
          url="shorewall-maclist.html">shorewall-maclist</ulink>(5) can be
          improved by setting the MACLIST_TTL variable in <ulink
          url="shorewall.conf.html">shorewall[6].conf</ulink>(5).</para>

          <para>If your iptables and kernel support the "Recent Match" (see
          the output of "shorewall check" near the top), you can cache the
          results of a 'maclist' file lookup and thus reduce the overhead
          associated with MAC Verification.</para>

          <para>When a new connection arrives from a 'maclist' interface, the
          packet passes through then list of entries for that interface in
          <ulink url="shorewall-maclist.html">shorewall-maclist</ulink>(5). If
          there is a match then the source IP address is added to the 'Recent'
          set for that interface. Subsequent connection attempts from that IP
          address occurring within $MACLIST_TTL seconds will be accepted
          without having to scan all of the entries. After $MACLIST_TTL from
          the first accepted connection request from an IP address, the next
          connection request from that IP address will be checked against the
          entire list.</para>

          <para>If MACLIST_TTL is not specified or is specified as empty (e.g,
          MACLIST_TTL="" or is specified as zero then 'maclist' lookups will
          not be cached).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">MANGLE_ENABLED=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Determines whether Shorewall will generate rules in the
          Netfilter mangle table. Setting MANGLE_ENABLED=No disables all
          Shorewall features that require the mangle table. The default is
          MANGLE_ENABLED=Yes.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">MINIUPNPD=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.0.8. If set to Yes, Shorewall will create
          a chain in the nat table named MINIUPNPD-POSTROUTING and will add
          jumps from POSTROUTING to that chain for each interface with the
          <option>upnpd</option> option specified. Default is No.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">MARK_IN_FORWARD_CHAIN=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>If your kernel has a FORWARD chain in the mangle table, you
          may set MARK_IN_FORWARD_CHAIN=Yes to cause the marking specified in
          the tcrules file to occur in that chain rather than in the
          PREROUTING chain. This permits you to mark inbound traffic based on
          its destination address when DNAT is in use. To determine if your
          kernel has a FORWARD chain in the mangle table, use the <emphasis
          role="bold">shorewall [-6] show mangle</emphasis> command; if a
          FORWARD chain is displayed then your kernel will support this
          option. If this option is not specified or if it is given the empty
          value (e.g., MARK_IN_FORWARD_CHAIN="") then MARK_IN_FORWARD_CHAIN=No
          is assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry id="MASK_BITS">
        <term><emphasis
        role="bold">MASK_BITS</emphasis>=[<replaceable>number</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.26. Number of bits on the right of the
          32-bit packet mark to be masked when clearing the traffic shaping
          mark. Must be &gt;= TC_BITS and &lt;= PROVIDER_OFFSET (if
          PROVIDER_OFFSET &gt; 0). Prior to Shorewall 5.0.0, default value and
          the default values of the other mark layout options is determined as
          follows:</para>

          <table frame="none">
            <title>Default Packet Mark Layout</title>

            <tgroup cols="2">
              <tbody>
                <row>
                  <entry>WIDE_TC_MARKS=No, HIGH_ROUTE_MARKS=No</entry>

                  <entry>TC_BITS=8, PROVIDER_BITS=8, PROVIDER_OFFSET=0,
                  MASK_BITS=8</entry>
                </row>

                <row>
                  <entry>WIDE_TC_MARKS=No, HIGH_ROUTE_MARKS=Yes</entry>

                  <entry>TC_BITS=8, PROVIDER_BITS=8, PROVIDER_OFFSET=8,
                  MASK_BITS=8</entry>
                </row>

                <row>
                  <entry>WIDE_TC_MARKS=Yes, HIGH_ROUTE_MARKS=No</entry>

                  <entry>TC_BITS=14, PROVIDER_BITS=8, PROVIDER_OFFSET=0,
                  MASK_BITS=16</entry>
                </row>

                <row>
                  <entry>WIDE_TC_MARKS=Yes, HIGH_ROUTE_MARKS=Yes</entry>

                  <entry>TC_BITS=14, PROVIDER_BITS=8, PROVIDER_OFFSET=16,
                  MASK_BITS=16</entry>
                </row>
              </tbody>
            </tgroup>
          </table>

          <para>From 5.0.0 onward, the default value of MASK_BITS is 8, the
          default value of PROVIDER_BITS, TC_BITS, MASK_BITS and
          PROVIDER_OFFSET is 8.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">MODULESDIR=</emphasis>[[+]<emphasis>pathname</emphasis>[<emphasis
        role="bold">:</emphasis><emphasis>pathname</emphasis>]...]</term>

        <listitem>
          <para>This parameter specifies the directory/directories where your
          kernel netfilter modules may be found. If you leave the variable
          empty, Shorewall will supply the value
          "/lib/modules/$uname/kernel/net/ipv${g_family}/netfilter:/lib/modules/$uname/kernel/net/netfilter:/lib/modules/$uname/kernel/net/sched:/lib/modules/$uname/extra:/lib/modules/$uname/extra/ipset"
          where <emphasis role="bold">uname</emphasis> holds the output of
          '<command>uname -r</command>' and <emphasis
          role="bold">g_family</emphasis> holds '4' in IPv4 configurations and
          '6' in IPv6 configurations.</para>

          <para>The option plus sign ('+') was added in Shorewall 5.0.3 and
          causes the listed pathnames to be appended to the default list
          above.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">MULTICAST=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>IPv4 only.</para>

          <para>This option will normally be set to 'No' (the default). It
          should be set to 'Yes' under the following circumstances:</para>

          <orderedlist>
            <listitem>
              <para>You have an interface that has parallel zones defined via
              /etc/shorewall/hosts.</para>
            </listitem>

            <listitem>
              <para>You want to forward multicast packets to two or more of
              those parallel zones.</para>
            </listitem>
          </orderedlist>

          <para>In such cases, you will configure a <option>destonly</option>
          network on each zone receiving multicasts.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">MUTEX_TIMEOUT=</emphasis>[<emphasis>seconds</emphasis>]</term>

        <listitem>
          <para>The value of this variable determines the number of seconds
          that programs will wait for exclusive access to the Shorewall[6]
          lock file. After the number of seconds corresponding to the value of
          this variable, programs will assume that the last program to hold
          the lock died without releasing the lock.</para>

          <para>If not set or set to the empty value, a value of 60 (60
          seconds) is assumed.</para>

          <para>An appropriate value for this parameter would be twice the
          length of time that it takes your firewall system to process a
          <emphasis role="bold">shorewall [-6] restart</emphasis>
          command.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">NFACCT=</emphasis>[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.7. Specifies the pathname of the nfacct
          utility. If not specified, Shorewall will use the PATH setting to
          find the program.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">NULL_ROUTE_RFC1918=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>|<emphasis
        role="bold">blackhole</emphasis>|<emphasis
        role="bold">unreachable</emphasis>|<emphasis
        role="bold">prohibit</emphasis>]</term>

        <listitem>
          <para>IPv4 only.</para>

          <para>When set to Yes, causes Shorewall to null-route the IPv4
          address ranges reserved by RFC1918. The default value is
          'No'.</para>

          <para>When combined with route filtering (ROUTE_FILTER=Yes or
          <option>routefilter</option> in <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)),
          this option ensures that packets with an RFC1918 source address are
          only accepted from interfaces having known routes to networks using
          such addresses.</para>

          <para>Beginning with Shorewall 4.5.15, you may specify
          <option>blackhole</option>, <option>unreachable</option> or
          <option>prohibit</option> to set the type of route to be created.
          See <ulink
          url="../MultiISP.html#null_routing">https://shorewall.org/MultiISP.html#null_routing</ulink>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">OPTIMIZE=</emphasis>[<replaceable>value</replaceable>]</term>

        <listitem>
          <para>The specified <replaceable>value</replaceable> enables certain
          optimizations. Each optimization category is associated with a power
          of two. To enable multiple optimization categories, simply add their
          corresponding numbers together.</para>

          <para>Beginning with Shorewall 4.5.20, you may specify OPTIMIZE=All
          to enable all optimization categories, and you may also specify
          OPTIMIZE=None to disable optimization.</para>

          <itemizedlist>
            <listitem>
              <para>Optimization category 1 - Traditionally, Shorewall has
              created rules for the complete matrix of host groups defined by
              the zones, interfaces and hosts files. Any traffic that didn't
              correspond to an element of that matrix was rejected in one of
              the built-in chains. When the matrix is sparse, this results in
              lots of largely useless rules.</para>

              <para>These extra rules can be eliminated by setting the 1 bit
              in OPTIMIZE.</para>

              <para>The 1 bit setting also controls the suppression of
              redundant wildcard rules (those specifying "all" in the SOURCE
              or DEST column). A wildcard rule is considered to be redundant
              when it has the same ACTION and Log Level as the applicable
              policy.</para>

              <note>
                <para>Optimization level 1 is ignored when optimization level
                4 is also selected, since level 4 performs similar
                optimizations in a more robust way.</para>
              </note>
            </listitem>

            <listitem>
              <para>Optimization category 2 - Added in Shorewall 4.4.7. When
              set, suppresses superfluous ACCEPT rules in a policy chain that
              implements an ACCEPT policy. Any ACCEPT rules that immediately
              precede the final blanket ACCEPT rule in the chain are now
              omitted.</para>
            </listitem>

            <listitem>
              <para>Optimization category 4 - Added in Shorewall 4.4.7. When
              set, causes short chains (those with less than 2 rules) to be
              optimized away. The following chains are excluded from
              optimization:</para>

              <itemizedlist>
                <listitem>
                  <para>accounting chains (unless
                  OPTIMIZE_ACCOUNTING=Yes)</para>
                </listitem>

                <listitem>
                  <para>action chains (user-defined)</para>
                </listitem>

                <listitem>
                  <para>'blacklst' chain</para>
                </listitem>

                <listitem>
                  <para>dynamic</para>
                </listitem>

                <listitem>
                  <para>forwardUPnP</para>
                </listitem>

                <listitem>
                  <para>UPnP (nat table)</para>
                </listitem>
              </itemizedlist>

              <para>Additionally:</para>

              <itemizedlist>
                <listitem>
                  <para>If a built-in chain has a single rule that branches to
                  a second chain, then the rules from the second chain are
                  moved to the built-in chain and the target chain is
                  omitted.</para>
                </listitem>

                <listitem>
                  <para>Chains with no references are deleted.</para>
                </listitem>

                <listitem>
                  <para>Accounting chains are subject to optimization if the
                  OPTIMIZE_ACCOUNTING option is set to 'Yes'.</para>
                </listitem>

                <listitem>
                  <para>If a chain ends with an unconditional branch to a
                  second chain (other than to 'reject'), then the branch is
                  deleted from the first chain and the rules from the second
                  chain are appended to it.</para>
                </listitem>
              </itemizedlist>

              <para>An additional optimization was added in Shorewall 4.5.4.
              If the last rule in a chain is an unqualified jump to a simple
              target, then all immediately preceding rules with the same
              simple target are omitted.</para>

              <para>For example, consider this chain:</para>

              <programlisting>	-A fw-net -p udp --dport 67:68 -j ACCEPT
	-A fw-net -p udp --sport 1194 -j ACCEPT
	-A fw-net -p 41 -j ACCEPT
	-A fw-net -j ACCEPT
</programlisting>

              <para>Since all of the rules are jumps to the simple target
              ACCEPT, this chain is totally optimized away and jumps to the
              chain are replace with jumps to ACCEPT.</para>
            </listitem>

            <listitem>
              <para>Optimization category 8 - Added in Shorewall 4.4.9. When
              set, causes chains with identical rules to be collapsed into a
              single chain.</para>

              <warning>
                <para>While Optimization category 8 can significantly reduce
                the size of the generated iptables ruleset, it can also take
                significant system resources during compilation. If you find
                that compilation takes an unreasonably long time, try
                disabling this category by setting OPTIMIZE=23.</para>
              </warning>
            </listitem>

            <listitem>
              <para>Optimization category 16 - Added in Shorewall 4.4.26. When
              set, causes sequences of <firstterm>compatible</firstterm> rules
              to be combined into a single rule. Rules are considered
              compatible if they differ only in their destination ports and
              comments.</para>

              <para>A sequence of compatible rules is often generated when
              macros are invoked in sequence.</para>

              <para>The ability to combine adjacent rules is limited by two
              factors:</para>

              <itemizedlist>
                <listitem>
                  <para>Destination port lists may only be combined up to a
                  maximum of 15 ports, where a port-pair counts as two
                  ports.</para>
                </listitem>

                <listitem>
                  <para>Rules may only be combined until the length of their
                  concatenated comment reaches 255 characters.</para>
                </listitem>
              </itemizedlist>

              <para>When either of these limits would be exceeded, the current
              combined rule is emitted and the compiler attempts to combine
              rules beginning with the one that would have exceeded the limit.
              Adjacent combined comments are separated by ', '. Empty comments
              at the front of a group of combined comments are replaced by
              'Others and'. Empty comments at the end of a group of combined
              comments are replaced by 'and others'.</para>

              <para>Beginning in Shorewall 4.5.10, this option also suppresses
              duplicate adjacent rules and duplicate non-adjacent rules that
              don't include <emphasis role="bold">mark</emphasis>, <emphasis
              role="bold">connmark</emphasis>, <emphasis
              role="bold">dscp</emphasis>, <emphasis
              role="bold">ecn</emphasis>, <emphasis
              role="bold">set</emphasis>, <emphasis role="bold">tos</emphasis>
              or <emphasis role="bold">u32</emphasis> matches.</para>

              <variablelist>
                <varlistentry>
                  <term>Example 1:</term>

                  <listitem>
                    <para>Rules with comments "FOO", &lt;empty&gt; and "BAR"
                    would result in the combined comment "FOO and others,
                    BAR".</para>
                  </listitem>
                </varlistentry>

                <varlistentry>
                  <term>Example 2:</term>

                  <listitem>
                    <para>Rules with comments &lt;empty&gt;, "FOO" and "BAR"
                    would result in the combined comment "Others and FOO,
                    BAR". Note: Optimize level 16 requires "Extended
                    Multi-port Match" in your iptables and kernel.</para>
                  </listitem>
                </varlistentry>
              </variablelist>
            </listitem>
          </itemizedlist>

          <para>In versions prior to 5.1.0, the default value is zero which
          disables all optimizations. Beginning with Shorewall 5.1.0, the
          default value is <emphasis role="bold">All</emphasis> which enables
          all optimizations.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">OPTIMIZE_ACCOUNTING=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.7. If set to Yes, Shorewall accounting
          changes are subject to optimization (OPTIMIZE=4,5,6 or 7). If not
          specified or set to the empty value, OPTIMIZE_ACCOUNTING=No is
          assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">PAGER=</emphasis><emphasis>pathname</emphasis></term>

        <listitem>
          <para>Added in Shorewall 5.0.6. Specifies a path name of a pager
          program like <command>less</command> or <command>more</command>.
          When PAGER is given, the output of verbose <command>status</command>
          commands and the <command>dump</command> command are piped through
          the named program when the output file is a terminal.</para>

          <para>Beginning with Shorewall 5.0.12, the default value of this
          option is the DEFAULT_PAGER setting in shorewallrc.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">PATH=</emphasis><emphasis>pathname</emphasis>[<emphasis
        role="bold">:</emphasis><emphasis>pathname</emphasis>]...</term>

        <listitem>
          <para>Determines the order in which Shorewall searches directories
          for executable files.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">PERL=</emphasis><emphasis>pathname</emphasis></term>

        <listitem>
          <para>Added in Shorewall 4.4.11 RC1. Specifies the path name of the
          Perl executable. Default is <filename>/usr/bin/perl</filename>. If
          the pathname specified by this option does not exist or the named
          file is not executable, then Shorewall falls back to
          <filename>/usr/bin/perl</filename></para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">PERL_HASH_SEED=</emphasis><emphasis
        role="bold"><replaceable>seed</replaceable><emphasis
        role="bold">|random</emphasis></emphasis></term>

        <listitem>
          <para>Added in Shorewall 5.1.4. Sets the Perl hash
          <replaceable>seed</replaceable> (an integer in the range 0-99999)
          when running the Shorewall rules compiler. If not specified, the
          value 0 is assumed. If <option>random</option> is specified, a
          random seed will be chosed by Perl. See perlsec(1) for additional
          information.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">PROVIDER_BITS</emphasis>=[<replaceable>number</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.26. The number of bits in the 32-bit
          packet mark to be used for provider numbers. May be zero. See <link
          linkend="MASK_BITS">MASK_BITS</link> above for default value.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">PROVIDER_OFFSET</emphasis>=[<replaceable>number</replaceable>]If</term>

        <listitem>
          <para>Added in Shorewall 4.4.26. The offset from the right
          (low-order end) of the provider number field in the 32-bit packet
          mark. If non-zero, must be &gt;= TC_BITS (Shorewall automatically
          adjusts PROVIDER_OFFSET's value). PROVIDER_OFFSET + PROVIDER_BITS +
          ZONE_BITS must be &lt; 32. See <link
          linkend="MASK_BITS">MASK_BITS</link> above for default value.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">RCP_COMMAND="</emphasis><replaceable>command</replaceable><emphasis
        role="bold">"</emphasis></term>

        <listitem>
          <para/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">RSH_COMMAND="</emphasis><replaceable>command</replaceable><emphasis
        role="bold">"</emphasis></term>

        <listitem>
          <para>Earlier generations of Shorewall Lite required that remote
          root login via ssh be enabled in order to use the
          <command>load</command> and <command>reload</command> commands.
          Beginning with release 3.9.5, you may define an alternative means
          for accessing the remote firewall system. In that release, two new
          options were added to shorewall.conf:</para>

          <simplelist>
            <member>RSH_COMMAND</member>

            <member>RCP_COMMAND</member>
          </simplelist>

          <para>The default values for these are as follows:</para>

          <programlisting>RSH_COMMAND: ssh ${root}@${system} ${command}
RCP_COMMAND: scp ${files} ${root}@${system}:${destination}</programlisting>

          <para>Shell variables that will be set when the commands are invoked
          are as follows:</para>

          <programlisting><replaceable>root</replaceable>        - root user. Normally <option>root</option> but may be overridden using the '-r' option.
<replaceable>system</replaceable>      - The name/IP address of the remote firewall system.
<replaceable>command</replaceable>     - For RSH_COMMAND, the command to be executed on the firewall system.
<replaceable>files</replaceable>       - For RCP_COMMAND, a space-separated list of files to be copied to the remote firewall system.
<replaceable>destination</replaceable> - The directory on the remote system that the files are to be copied into.</programlisting>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">RELATED_DISPOSITION=[ACCEPT|A_ACCEPT|A_DROP|A_REJECT|DROP|REJECT|CONTINUE]</emphasis></term>

        <listitem>
          <para>Added in Shorewall 4.4.27. Shorewall has traditionally
          ACCEPTed RELATED packets that don't match any rule in the RELATED
          section of <ulink url="shorewall-rules.html">shorewall-rules</ulink>
          (5). Concern about the safety of this practice resulted in the
          addition of this option. When a packet in RELATED state fails to
          match any rule in the RELATED section, the packet is disposed of
          based on this setting. The default value is ACCEPT for compatibility
          with earlier versions.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">RELATED_LOG_LEVEL=</emphasis><emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.27. Packets in the related state that
          do not match any rule in the RELATED section of <ulink
          url="shorewall-rules.html">shorewall-rules</ulink> (5) are logged at
          this level. The default value is empty which means no logging is
          performed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">REJECT_ACTION=</emphasis><emphasis>action</emphasis></term>

        <listitem>
          <para>Added in Shorewall 4.5.21. When a REJECT target is specified,
          Shorewall normally handles the response as follows:</para>

          <itemizedlist>
            <listitem>
              <para>If the destination address of the packet is a broadcast or
              multicast address, the packet is dropped.</para>
            </listitem>

            <listitem>
              <para>if the protocol is ICMP (2) then the packet is
              dropped.</para>
            </listitem>

            <listitem>
              <para>if the protocol is TCP (6) then the packet is rejected
              with an RST.</para>
            </listitem>

            <listitem>
              <para>if the protocol is UDP (17) then the packet is rejected
              with an 'port-unreachable' ICMP.</para>
            </listitem>

            <listitem>
              <para>if the protocol is ICMP (1) then the packet is rejected
              with a 'host-unreachable' ICMP.</para>
            </listitem>

            <listitem>
              <para>if the protocol is ICMP6 (1) then the packet is rejected
              with a 'icmp6-addr-unreachable' ICMP6.</para>
            </listitem>

            <listitem>
              <para>otherwise, the packet is rejected with a 'host-prohibited'
              ICMP.</para>
            </listitem>
          </itemizedlist>

          <para>You can modify this behavior by implementing your own
          <replaceable>action</replaceable> that handles REJECT and specifying
          it's name in this option. The <emphasis role="bold">nolog</emphasis>
          and <emphasis role="bold">noinline</emphasis> options will
          automatically be assumed for the specified
          <replaceable>action</replaceable>.</para>

          <para>The following action implements the default reject
          action:</para>

          <programlisting>?format 2
#TARGET         SOURCE  DEST    PROTO
Broadcast(DROP) -       -       -
DROP            -       -       2
INLINE          -       -       6       ;; -j REJECT --reject-with tcp-reset
?if __ENHANCED_REJECT
INLINE          -       -       17      ;; -j REJECT
?if __IPV4
INLINE          -       -       1       ;; -j REJECT --reject-with icmp-host-unreachable
INLINE          -       -       -       ;; -j REJECT --reject-with icmp-host-prohibited
?else
INLINE          -       -       58      ;; -j REJECT --reject-with icmp6-addr-unreachable
INLINE          -       -       -       ;; -j REJECT --reject-with icmp6-adm-prohibited
?endif
?else
INLINE          -       -       -       ;; -j REJECT
?endif</programlisting>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">RENAME_COMBINED=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.2.0. Traditionally, when OPTIMIZE
          category 8 is enabled, identical chains are combined under a name
          beginning with '~comb' or '~blacklist'. This behavior is maintained
          under the default setting RENAME_COMBINED=Yes. If
          RENAMED_COMBINED=No, the chains are combined under the original name
          of one of the chains.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">REQUIRE_INTERFACE=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.10. The default is No. If set to Yes,
          at least one optional interface must be up in order for the firewall
          to be in the started state. Intended to be used with the <ulink
          url="shorewall-init.html">Shorewall Init Package</ulink>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">RESTART=</emphasis>[<emphasis
        role="bold">restart</emphasis>|<emphasis
        role="bold">reload</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.0.1 to replace LEGACY_RESTART which was
          added in Shorewall 5.0.0. In that release, the <emphasis
          role="bold">reload</emphasis> command was redefined to do what
          <emphasis role="bold">restart</emphasis> had done in earlier
          releases and <emphasis role="bold">restart</emphasis> became a true
          restart (equivalent to <emphasis role="bold">stop</emphasis>
          followed by <emphasis role="bold">start</emphasis>). When
          RESTART=reload, the <emphasis role="bold">restart</emphasis> command
          performs the same operation as the <emphasis
          role="bold">reload</emphasis> command making it compatible with
          earlier releases. If not specified, RESTART=reload is
          assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">RESTORE_DEFAULT_ROUTE=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>This option determines whether to restore the default route
          saved when here are 'balance' providers defined but all of them are
          down.</para>

          <para>The default is RESTORE_DEFAULT_ROUTE=Yes which preserves the
          pre-4.2.6 behavior.</para>

          <para>RESTORE_DEFAULT_ROUTE=No is appropriate when you don't want a
          default route in the main table (USE_DEFAULT_RT=No) or in the
          default table (USE_DEFAULT_RT=Yes) when there are no balance
          providers available. In that case, RESTORE_DEFAULT_ROUTE=No will
          cause any default route in the relevant table to be deleted.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">RESTORE_ROUTEMARKS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.9. When set to <emphasis
          role="bold">Yes</emphasis> (the default), provider marks are
          restored unconditionally at the top of the mangle OUTPUT and
          PREROUTING chains, even if the saved mark is zero. When this option
          is set to <emphasis role="bold">No</emphasis>, the mark is restored
          only if it is non-zero. If you have problems with IPSEC ESP packets
          not being routed correctly on output, try setting this option to
          <emphasis role="bold">No</emphasis>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">RESTOREFILE=</emphasis><emphasis>filename</emphasis></term>

        <listitem>
          <para>Specifies the simple name of a file in /var/lib/shorewall to
          be used as the default restore script in the <emphasis
          role="bold">shorewall [-6] save</emphasis>, <emphasis
          role="bold">shorewall [-6] restore</emphasis>, <emphasis
          role="bold">shorewall [-6] forget </emphasis>and <emphasis
          role="bold">shorewall [6] -f start</emphasis> commands.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">RETAIN_ALIASES=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>IPv4 only.</para>

          <para>During <emphasis role="bold">shorewall star</emphasis>t, IP
          addresses to be added as a consequence of ADD_IP_ALIASES=Yes and
          ADD_SNAT_ALIASES=Yes are quietly deleted when <ulink
          url="shorewall-nat.html">shorewall-nat</ulink>(5) and <ulink
          url="shorewall-masq.html">shorewall-masq</ulink>(5) are processed
          then are re-added later. This is done to help ensure that the
          addresses can be added with the specified labels but can have the
          undesirable side effect of causing routes to be quietly deleted.
          When RETAIN_ALIASES is set to Yes, existing addresses will not be
          deleted. Regardless of the setting of RETAIN_ALIASES, addresses
          added during <emphasis role="bold">shorewall start</emphasis> are
          still deleted at a subsequent <emphasis role="bold">shorewall
          [stop</emphasis>, <emphasis role="bold">shorewall reload</emphasis>
          or <emphasis role="bold">shorewall restart</emphasis>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">ROUTE_FILTER=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>|Keep]</term>

        <listitem>
          <para>If this parameter is given the value <emphasis
          role="bold">Yes</emphasis> or <emphasis role="bold">yes</emphasis>
          then route filtering (anti-spoofing) is enabled on all network
          interfaces which are brought up while Shorewall is in the started
          state. The default value is <emphasis
          role="bold">no</emphasis>.</para>

          <para>The value <emphasis role="bold">Keep</emphasis> causes
          Shorewall to ignore the option. If the option is set to <emphasis
          role="bold">Yes</emphasis>, then route filtering occurs on all
          interfaces. If the option is set to <emphasis
          role="bold">No</emphasis>, then route filtering is disabled on all
          interfaces except those specified in <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5).</para>

          <important>
            <para>If you need to disable route filtering on any interface,
            then you must set ROUTE_FILTER=No then set routefilter=1 or
            routefilter=2 on those interfaces where you want route filtering.
            See <ulink
            url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)
            for additional details.</para>
          </important>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">RPFILTER_DISPOSITION=</emphasis>[<emphasis
        role="bold">DROP</emphasis>|<emphasis
        role="bold">REJECT</emphasis>|A_DROP|A_REJECT]</term>

        <listitem>
          <para>Added in Shorewall 4.5.7. Determines the disposition of
          packets entering from interfaces the <option>rpfilter</option>
          option (see <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)).
          Packets disposed of by this option are those whose response packets
          would not be sent through the same interface receiving the
          packet.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">RPFILTER_LOG_LEVEL=</emphasis><emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]</term>

        <listitem>
          <para>Added in shorewall 4.5.7. Determines the logging of packets
          disposed via the RPFILTER_DISPOSITION. The default value is
          <option>info</option>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SAVE_ARPTABLES=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Added in Shorewall 4.5.12. If SAVE_ARPTABLES=Yes, then the
          current arptables contents will be saved by <emphasis
          role="bold">shorewall save</emphasis> command and restored by
          <emphasis role="bold">shorewall restore</emphasis> command. Default
          value is No.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SAVE_IPSETS=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No|ipv4|<replaceable>setlist</replaceable></emphasis>}</term>

        <listitem>
          <para>Re-enabled in Shorewall 4.4.6. If SAVE_IPSETS=Yes, then the
          current contents of your ipsets will be saved by the <emphasis
          role="bold">shorewall stop</emphasis> and <emphasis
          role="bold">shorewall save</emphasis> commands and restored by the
          <emphasis role="bold">shorewall start</emphasis> and <emphasis
          role="bold">shorewall restore</emphasis> commands.</para>

          <para>Beginning with Shorewall 4.6.4, you can restrict the set of
          ipsets saved by specifying a setlist (a comma-separated list of ipv4
          ipset names). You may also restrict the saved sets to just the ipv4
          ones by specifying <emphasis role="bold">ipv4</emphasis>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SFILTER_DISPOSITION=</emphasis>[<emphasis
        role="bold">DROP</emphasis>|<emphasis
        role="bold">REJECT</emphasis>|A_DROP|A_REJECT]</term>

        <listitem>
          <para>Added in Shorewall 4.4.20. Determines the disposition of
          packets matching the <option>sfilter</option> option (see <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)) and
          of <firstterm>hairpin</firstterm> packets on interfaces without the
          <option>routeback</option> option.<footnote>
              <para>Hairpin packets are packets that are routed out of the
              same interface that they arrived on.</para>
            </footnote></para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">SFILTER_LOG_LEVEL=</emphasis><emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]</term>

        <listitem>
          <para>Added on Shorewall 4.4.20. Determines the logging of packets
          matching the <option>sfilter</option> option (see <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)) and
          of <firstterm>hairpin</firstterm> packets on interfaces without the
          <option>routeback</option> option.<footnote>
              <para>Hairpin packets are packets that are routed out of the
              same interface that they arrived on.</para>
            </footnote> The default is <option>info</option>. If you don't
          wish for these packets to be logged, use
          SFILTER_LOG_LEVEL=none.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">SHOREWALL_SHELL=</emphasis>[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>This option is used to specify the shell program to be used to
          interpret the compiled script. If not specified or specified as a
          null value, /bin/sh is assumed. Using a light-weight shell such as
          ash or dash can significantly improve performance.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SMURF_DISPOSITION=</emphasis>[<emphasis
        role="bold">DROP</emphasis>|A_DROP]</term>

        <listitem>
          <para>Added in Shorewall 4.4.20. The default setting is DROP which
          causes smurf packets (see the nosmurfs option in <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)) to
          be dropped. A_DROP causes the packets to be audited prior to being
          dropped and requires AUDIT_TARGET support in the kernel and
          iptables.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">SMURF_LOG_LEVEL=</emphasis>[<emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]]</term>

        <listitem>
          <para>Specifies the logging level for smurf packets (see the
          nosmurfs option in <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)). If
          set to the empty value ( SMURF_LOG_LEVEL="" ) then smurfs are not
          logged.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">STARTUP_ENABLED=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Determines if Shorewall is allowed to start. As released from
          shorewall.net, this option is set to <emphasis
          role="bold">No</emphasis>. When set to <emphasis
          role="bold">Yes</emphasis> or <emphasis role="bold">yes</emphasis>,
          Shorewall may be started. Used as a guard against Shorewall being
          accidentally started before it has been configured.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">STARTUP_LOG=</emphasis>[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>If specified, determines where Shorewall will log the details
          of each <emphasis role="bold">start</emphasis>, <emphasis
          role="bold">reload</emphasis>, <emphasis
          role="bold">restart</emphasis>, <emphasis
          role="bold">try</emphasis>, and <emphasis
          role="bold">safe-</emphasis>* command. Logging verbosity is
          determined by the setting of LOG_VERBOSITY above.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">SUBSYSLOCK=</emphasis>[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>This parameter should be set to the name of a file that the
          firewall should create if it starts successfully and remove when it
          stops. Creating and removing this file allows Shorewall to work with
          your distribution's initscripts. For OpenSuSE, this should be set to
          /var/lock/subsys/shorewall (var/lock/subsys/shorewall-lite if
          building for export). For Gentoo, it should be set to
          /run/lock/shorewall (/run/lock/shorewall-lite). For Redhat and
          derivatives as well as Debian and derivatives, the pathname should
          be omitted.</para>

          <important>
            <para>Beginning with Shorewall 5.1.0, this setting is ignored when
            SERVICEDIR is non-empty in
            <filename>${SHAREDIR}/shorewall/shorewallrc</filename> (usually
            <filename>/usr/share/shorewall/shorewallrc</filename>).</para>
          </important>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">TC</emphasis>=[<emphasis>pathname</emphasis>]</term>

        <listitem>
          <para>If specified, gives the pathname of the 'tc' executable. If
          not specified, 'tc' is assumed and the utility will be located using
          the current PATH setting.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">TC_BITS</emphasis>=[<replaceable>number</replaceable>]</term>

        <listitem>
          <para>The number of bits at the low end of the 32-bit packet mark to
          be used for traffic shaping marking. May be zero. See <link
          linkend="MASK_BITS">MASK_BITS</link> above for default value.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">TC_ENABLED=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>|<emphasis
        role="bold">Internal</emphasis>|<emphasis
        role="bold">Simple</emphasis>|<emphasis
        role="bold">Shared</emphasis>]</term>

        <listitem>
          <para>If you say <emphasis role="bold">Yes</emphasis> or <emphasis
          role="bold">yes</emphasis> here, Shorewall will use a script that
          you supply to configure traffic shaping. The script must be named
          'tcstart' and must be placed in a directory on your
          CONFIG_PATH.</para>

          <para>If you say <emphasis role="bold">No</emphasis> or <emphasis
          role="bold">no</emphasis> then traffic shaping is not
          enabled.</para>

          <para>If you set TC_ENABLED=Simple (Shorewall 4.4.6 and later),
          simple traffic shaping using <ulink
          url="shorewall-tcinterfaces.html">shorewall-tcinterfaces</ulink>(5)
          and <ulink url="shorewall-tcpri.html">shorewall-tcpri</ulink>(5) is
          enabled.</para>

          <para>If you set TC_ENABLED=Internal or internal or leave the option
          empty then Shorewall will use its builtin traffic shaper
          (tc4shorewall written by Arne Bernin.</para>

          <para>Beginning with Shorewall 4.4.15, you can set
          TC_ENABLED=Shared. This allows you to configure the tcdevices and
          tcclasses in your Shorewall6 configuration yet make them available
          to the compiler when compiling your Shorewall configuration. In
          addition to setting TC_ENABLED=Shared, you need to create symbolic
          links from your Shorewall configuration directory (normally
          /etc/shorewall/) to the tcdevices and tcclasses files in your
          Shorewall6 configuration directory (normally
          /etc/shorewall6/).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">TC_EXPERT=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Normally, Shorewall tries to protect users from themselves by
          preventing PREROUTING and OUTPUT tcrules from being applied to
          packets that have been marked by the 'track' option in <ulink
          url="shorewall-providers.html">shorewall-providers</ulink>(5).</para>

          <para>If you know what you are doing, you can set TC_EXPERT=Yes and
          Shorewall will not include these cautionary checks.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">TC_PRIOMAP</emphasis>=<emphasis>map</emphasis></term>

        <listitem>
          <para>Added in Shorewall 4.4.6. Determines the mapping of a packet's
          TOS field to priority bands. See <ulink
          url="shorewall-tcpri.html">shorewall-tcpri</ulink>(5). The
          <emphasis>map</emphasis> consists of 16 space-separated digits with
          values 1, 2 or 3. A value of 1 corresponds to Linux priority 0, 2 to
          Linux priority 1, and 3 to Linux Priority 2. The first entry gives
          the priority of TOS value 0, the second of TOS value 1, and so on.
          See tc-prio(8) for additional information.</para>

          <para>The default setting is TC_PRIOMAP="2 3 3 3 2 3 1 1 2 2 2 2 2 2
          2 2".</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">TCP_FLAGS_DISPOSITION=</emphasis>[<emphasis
        role="bold">ACCEPT</emphasis>|<emphasis
        role="bold">DROP</emphasis>|<emphasis
        role="bold">REJECT</emphasis>|A_DROP|A_REJECT]</term>

        <listitem>
          <para>Determines the disposition of TCP packets that fail the checks
          enabled by the <emphasis role="bold">tcpflags</emphasis> interface
          option (see <ulink
          url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5)) and
          must have a value of ACCEPT (accept the packet), REJECT (send an RST
          response) or DROP (ignore the packet). If not set or if set to the
          empty value (e.g., TCP_FLAGS_DISPOSITION="") then
          TCP_FLAGS_DISPOSITION=DROP is assumed.</para>

          <para>A_DROP and A_REJECT are audited versions of DROP and REJECT
          respectively and were added in Shorewall 4.4.20. They require
          AUDIT_TARGET in the kernel and iptables.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">TCP_FLAGS_LOG_LEVEL=</emphasis>[<emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]]</term>

        <listitem>
          <para>Determines the syslog level for logging packets that fail the
          checks enabled by the tcpflags interface option. The value must be a
          valid syslogd log level. If you don't want to log these packets, set
          to the empty value (e.g., TCP_FLAGS_LOG_LEVEL="").</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">TRACK_PROVIDERS=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>}</term>

        <listitem>
          <para>Added in Shorewall 4.4.3. When set to Yes, causes the
          <option>track</option> option to be assumed on all providers defined
          in <ulink
          url="shorewall-providers.html">shorewall-providers</ulink>(5). May
          be overridden on an individual provider through use of the
          <option>notrack</option> option. The default value is 'No'.</para>

          <para>Beginning in Shorewall 4.4.6, setting this option to 'Yes'
          also simplifies PREROUTING rules in <ulink
          url="shorewall-tcrules.html">shorewall-tcrules</ulink>(5).
          Previously, when TC_EXPERT=No, packets arriving through 'tracked'
          provider interfaces were unconditionally passed to the PREROUTING
          tcrules. This was done so that tcrules could reset the packet mark
          to zero, thus allowing the packet to be routed using the 'main'
          routing table. Using the main table allowed dynamic routes (such as
          those added for VPNs) to be effective. The rtrules file was created
          to provide a better alternative to clearing the packet mark. As a
          consequence, passing these packets to PREROUTING complicates things
          without providing any real benefit. Beginning with Shorewall 4.4.6,
          when TRACK_PROVIDERS=Yes and TC_EXPERT=No, packets arriving through
          'tracked' interfaces will not be passed to the PREROUTING rules.
          Since TRACK_PROVIDERS was just introduced in 4.4.3, this change
          should be transparent to most, if not all, users.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">TRACK_RULES=</emphasis>{<emphasis
        role="bold">Yes</emphasis>|<emphasis
        role="bold">No</emphasis>|File}</term>

        <listitem>
          <para>Added in Shorewall 4.5.20. If set to <emphasis
          role="bold">Yes</emphasis>, causes the compiler to add a comment to
          iptables rules to indicate the file name and line number of the
          configuration entry that generated the rule. If set to <emphasis
          role="bold">No</emphasis> (the default), then no such comments are
          added.</para>

          <para>Setting this option to <emphasis role="bold">Yes</emphasis>
          requires the <firstterm>Comments</firstterm> capability in iptables
          and kernel.</para>

          <para>Beginning with Shorewall 5.0.5, the option may also be set to
          <emphasis role="bold">File</emphasis>. That setting causes similar
          comments to be added to the
          <filename>.iptables-restore-input</filename> file, which is normally
          created in <filename>/var/lib/shorewall</filename>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">UNTRACKED_DISPOSITION=[ACCEPT|A_ACCEPT|A_DROP|A_REJECT|DROP|REJECT|CONTINUE]</emphasis></term>

        <listitem>
          <para>Added in Shorewall 4.5.13. Shorewall has traditionally passed
          UNTRACKED packets through the NEW section of <ulink
          url="shorewall-rules.html">shorewall-rules</ulink> (5). When a
          packet in UNTRACKED state fails to match any rule in the UNTRACKED
          section, the packet is disposed of based on this setting. The
          default value is CONTINUE for compatibility with earlier
          versions.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">UNTRACKED_LOG_LEVEL=</emphasis><emphasis>log-level</emphasis>[:<replaceable>log-tag</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.13. Packets in the UNTRACKED state that
          do not match any rule in the UNTRACKED section of <ulink
          url="shorewall-rules.html">shorewall-rules</ulink> (5) are logged at
          this level. The default value is empty which means no logging is
          performed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">USE_DEFAULT_RT=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>When set to 'Yes', this option causes the Shorewall multi-ISP
          feature to create a set of routing rules which are resilient to
          changes in the main routing table. Such changes can occur for a
          number of reasons, VPNs going up and down being an example. The idea
          is to send packets through the main table prior to applying any of
          the Shorewall-generated routing rules. So changes to the main table
          will affect the routing of packets by default.</para>

          <para>When USE_DEFAULT_RT=Yes:</para>

          <orderedlist>
            <listitem>
              <para>Both the DUPLICATE and the COPY columns in <ulink
              url="shorewall-providers.html">providers</ulink>(5) file must
              remain empty (or contain "-").</para>
            </listitem>

            <listitem>
              <para>The default route is added to the the 'default' table
              rather than to the main table.</para>
            </listitem>

            <listitem>
              <para>If running Shorewall 5.1.0 or earlier or if
              BALANCE_PROVIDERS=Yes (Shorewall 5.1.1 or later), then the
              <emphasis role="bold">balance</emphasis> provider option is
              assumed unless the <option>fallback</option>,
              <option>loose</option>, <option>load</option> or
              <option>tproxy</option> option is specified.</para>
            </listitem>

            <listitem>
              <para>Packets are sent through the main routing table by a rule
              with priority 999. In <ulink
              url="shorewall-rtrules.html">shorewall-rtrules</ulink>(5), the
              range 1-998 may be used for inserting rules that bypass the main
              table.</para>
            </listitem>

            <listitem>
              <para>All provider gateways must be specified explicitly in the
              GATEWAY column. <emphasis role="bold">detect</emphasis> may not
              be specified.<note>
                  <para><emphasis role="bold">detect</emphasis> may be
                  specified for interfaces whose configuration is managed by
                  dhcpcd. Shorewall will use dhcpcd's database to find the
                  interface's gateway.</para>
                </note></para>
            </listitem>

            <listitem>
              <para>You should disable all default route management outside of
              Shorewall. If a default route is added to the main table while
              Shorewall is started, then all policy routing will stop working
              (except for those routing rules in the priority range
              1-998).</para>
            </listitem>
          </orderedlist>

          <para>Prior to Shorewall 4.6.0, if USE_DEFAULT_RT was not set or if
          it was set to the empty string then USE_DEFAULT_RT=No was assumed.
          Beginning with Shorewall 4.6.0, the default is USE_DEFAULT_RT=Yes
          and use of USE_DEFAULT_RT=No is deprecated.</para>

          <warning>
            <para>The <command>enable</command>, <command>disable</command>
            and <command>reenable</command> commands do not work correctly
            when USE_DEFAULT_RT=No.</para>
          </warning>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">USE_NFLOG_SIZE=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.1.5. The second parameter to the NFLOG
          target specifies how many bytes of the packet to copy to the log; if
          omitted or if supplied as zero, the entire packet is copied. This
          feature has traditionally been implemented using the --nflog-range
          option to the NFLOG iptables target. Unfortuntely, the --nflog-range
          option never worked (the entire packet was always copied). To deal
          with this issue, the Netfilter team:</para>

          <itemizedlist>
            <listitem>
              <para>Added a warning message when --nflog-range is used</para>
            </listitem>

            <listitem>
              <para>Added --nflog-size which works like --nflog-range was
              intended to work.</para>
            </listitem>
          </itemizedlist>

          <para>When USE_NFLOG_SIZE=Yes, Shorewall will attempt to use the new
          --nflog-size feature. If that feature is not available in the
          running kernel and ip[6]tables, an error is raised.</para>

          <para>When USE_NFLOG_SIZE is not supplied, USE_NFLOG_SIZE=No is
          assumed. When USE_NFLOG_SIZE is added by shorewall update, it is
          added with setting No.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">USE_PHYSICAL_NAMES=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.27. Normally, when Shorewall creates a
          Netfilter chain that relates to an interface, it uses the
          interface's logical name as the base of the chain name. For example,
          if the logical name for an interface is OAKLAND, then the input
          chain for traffic arriving on that interface would be 'OAKLAND_in'.
          If this option is set to Yes, then the physical name of the
          interface will be used the base of the chain name.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">USE_RT_NAMES=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.15. When set to 'Yes', Shorewall will
          use routing table (provider) names in the generated script rather
          than table numbers. When set to 'No' (the default), routing table
          numbers will be used.</para>

          <caution>
            <para>If you set USE_RT_NAMES=Yes and KEEP_RT_TABLES=Yes, then you
            must insure that all of your providers have entries in
            /etc/iproute2/rt_tables as well as the following entries:</para>

            <simplelist>
              <member>255 local</member>

              <member>254 main</member>

              <member>253 default</member>

              <member>250 balance</member>

              <member>0 unspec</member>
            </simplelist>

            <para>Without these entries, the firewall will fail to
            start.</para>
          </caution>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">VERBOSE_MESSAGES=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.0.9. When Yes (the default), messages
          produced by the ?INFO and ?WARNING directives include the filename
          and linenumber of the directive. When set to No, that additional
          information is omitted. The setting may be overridden on a directive
          by directive basis by following ?INFO or ?WARNING with '!' (no
          intervening white space).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">VERBOSITY=</emphasis>[<emphasis>number</emphasis>]</term>

        <listitem>
          <para>Shorewall has traditionally been very noisy (produced lots of
          output). You may set the default level of verbosity using the
          VERBOSITY OPTION.</para>

          <para>Values are:</para>

          <simplelist>
            <member>0 - Silent. You may make it more verbose using the -v
            option</member>

            <member>1 - Major progress messages displayed</member>

            <member>2 - All progress messages displayed (pre Shorewall-3.2.0
            behavior)</member>
          </simplelist>

          <para>If not specified, then 2 is assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">WARNOLDCAPVERSION=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.12. When set to <emphasis
          role="bold">Yes</emphasis> (the default), the compiler issues a
          warning when it finds a capabilities file that doesn't specify all
          of the capabilities supported by the compiler. When
          WARNOLDCAPVERSION is set to <emphasis role="bold">No</emphasis>, no
          warning is issued.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">WORKAROUNDS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 4.6.11. Over time, there have been a number
          of changes in Shorewall that work around defects in other products
          such as iptables and ipset. When WORKAROUNDS=Yes, these workarounds
          are enabled; when WORKAROUNDS=No, they are disabled. If not
          specified or if specified as empty, WORKAROUNDS=Yes is
          assumed.</para>

          <warning>
            <para>Do not set WORKAROUNDS=Yes if you need to be able to use
            Shorewall-generated scripts (such as created by the
            <command>save</command> command) built by Shorewall 4.4.7 or
            older.</para>
          </warning>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">ZERO_MARKS=</emphasis>[<emphasis
        role="bold">Yes</emphasis>|<emphasis role="bold">No</emphasis>]</term>

        <listitem>
          <para>Added in Shorewall 5.0.12, this is a workaround for an issue
          where packet marks are not zeroed by the kernel. It should be set to
          No (the default) unless you find that incoming packets are being
          mis-routed for no apparent reasons.</para>

          <caution>
            <para>Do not set this option to Yes if you have IPSEC software
            running on the firewall system.</para>
          </caution>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">ZONE_BITS</emphasis>=[<replaceable>number</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.26. When non-zero, enables automatic
          packet marking by source zone and determines the number of bits in
          the 32-bit packet mark to be used for the zone mark. Default value
          is 0.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis
        role="bold">ZONE2ZONE</emphasis>=[<option>2</option>|<option>-</option>]</term>

        <listitem>
          <para>Added in Shorewall 4.4.4. This option determines how Shorewall
          constructs chain names involving zone names and/or 'all'. Beginning
          with Shorewall 4.6.0, the default is '-' (e.g., fw-net); prior to
          that release, the default was '2' (e.g., fw2net).</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>FILES</title>

    <para>/etc/shorewall/shorewall.conf</para>

    <para>/etc/shorewall6/shorewall6.conf</para>
  </refsect1>

  <refsect1>
    <title>See ALSO</title>

    <para>shorewall(8)</para>
  </refsect1>
</refentry>