shorewall_code/docs/Shorewall-init.xml

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  <articleinfo>
    <title>Shorewall Init</title>

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

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

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

    <copyright>
      <year>2010</year>

      <holder>Thomas M. Eastep</holder>
    </copyright>

    <legalnotice>
      <para>Permission is granted to copy, distribute and/or modify this
      document under the terms of the GNU Free Documentation License, Version
      1.2 or any later version published by the Free Software Foundation; with
      no Invariant Sections, with no Front-Cover, and with no Back-Cover
      Texts. A copy of the license is included in the section entitled
      <quote><ulink url="GnuCopyright.htm">GNU Free Documentation
      License</ulink></quote>.</para>
    </legalnotice>
  </articleinfo>

  <section>
    <title>Introduction</title>

    <para>The Shorewall init scripts released from shorewall.net and by most
    distributions start Shorewall after networking. This allows Shorewall to
    detect the network configuration and taylor itself accordingly. It is
    possible to start Shorewall prior to networking but doing so limits the
    set of Shorewall features that can be used.</para>

    <para>When Shorewall starts after networking, there is the possibility of
    unwanted connections being accepted between the time that an interface
    comes up and the time that Shorewall has finished starting up. Also,
    Shorewall has had no means of reacting when interfaces are brought up and
    down.</para>

    <para>Beginning with Shorewall 4.4.10, a new package, <firstterm>Shorewall
    Init</firstterm>, is available. Shorewall Init serves two purposes:</para>

    <orderedlist>
      <listitem>
        <para>It can 'close' the firewall before the network interfaces are
        brought up during boot.</para>
      </listitem>

      <listitem>
        <para>It can change the firewall state as the result of interfaces
        being brought up or taken down.</para>
      </listitem>
    </orderedlist>

    <para>These two features can be controlled independently. Shorewall Init
    can be used together with any combination of the other Shorewall packages.
    Shorewall-init works on RedHat-based, SuSE-based and Debian-based
    distributions.</para>
  </section>

  <section id="Close">
    <title>Closing the Firewall before the Network Interfaces are brought
    up</title>

    <para>When Shorewall-init is first installed, it does nothing until you
    configure it.</para>

    <para>The configuration file is <filename>/etc/default/shorewall-init
    </filename>on Debian-based systems and
    <filename>/etc/sysconfig/shorewall-init</filename> otherwise. There are
    two settings in the file:</para>

    <variablelist>
      <varlistentry>
        <term>PRODUCTS</term>

        <listitem>
          <para>Lists the Shorewall packages that you want to integrate with
          Shorewall-init.</para>

          <para>Example: PRODUCTS="shorewall shorewall6"</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>IFUPDOWN</term>

        <listitem>
          <para>When set to 1, enables integration with NetworkManager and the
          ifup/ifdown scripts.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>To close your firewall before networking starts:</para>

    <orderedlist numeration="loweralpha">
      <listitem>
        <para>In the Shorewall-init configuration file, set PRODUCTS to the
        firewall products installed on your system.</para>
      </listitem>

      <listitem>
        <para>Be sure that your current firewall script(s) (normally in
        <filename>/var/lib/&lt;product&gt;/firewall</filename>) is(are)
        compiled with the 4.4.10 compiler.</para>

        <para>Shorewall and Shorewall6 users can execute these
        commands:</para>

        <simplelist>
          <member>shorewall compile</member>

          <member><command>shorewall6 compile</command></member>
        </simplelist>

        <para>Shorewall-lite and Shorewall6-lite users can execute these
        commands on the administrative system:</para>

        <simplelist>
          <member><command>shorewall export
          <replaceable>firewall-name-or-ip-address</replaceable></command></member>

          <member><command>shorewall6 export
          <replaceable>firewall-name-or-ip-address</replaceable></command></member>
        </simplelist>
      </listitem>
    </orderedlist>

    <para>That's all that is required.</para>
  </section>

  <section id="NM">
    <title>Integration with NetworkManager and ifup/ifdown Scripts</title>

    <para>To integrate with NetworkManager and ifup/ifdown, additional steps
    are required. You probably don't want to enable this feature if you run a
    link status monitor like swping or LSM.</para>

    <orderedlist numeration="loweralpha">
      <listitem>
        <para>In the Shorewall-init configuration file, set IFUPDOWN=1.</para>
      </listitem>

      <listitem>
        <para>In your Shorewall interfaces file(s), set the
        <option>required</option> option on any interfaces that must be up in
        order for the firewall to start. At least one interface must have the
        <option>required</option> or <option>optional</option> option if you
        perform the next optional step.</para>
      </listitem>

      <listitem>
        <para>Optional) -- If you have specified at least one
        <option>required</option> or <option>optional</option> interface, you
        can then disable automatic firewall startup at boot time. On Debian
        systems, set startup=0 in
        <filename>/etc/default/<replaceable>product</replaceable></filename>.
        On other systems, use your service startup configuration tool
        (chkconfig, insserv, ...) to disable startup.</para>

        <warning>
          <para>If your system uses Upstart as it's system initialization
          daemon, you should not disable startup. Upstart is standard on
          recent Ubuntu and Fedora releases and is optional on Debian.</para>
        </warning>
      </listitem>
    </orderedlist>

    <para>The following actions occur when an interface comes up:</para>

    <informaltable>
      <tgroup cols="3">
        <tbody>
          <row>
            <entry><emphasis role="bold">FIREWALL STATE</emphasis></entry>

            <entry><emphasis role="bold">INTERFACE</emphasis></entry>

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

          <row>
            <entry>Any</entry>

            <entry>Required</entry>

            <entry>start</entry>
          </row>

          <row>
            <entry>stopped</entry>

            <entry>Optional</entry>

            <entry>start</entry>
          </row>

          <row>
            <entry>started</entry>

            <entry>Optional</entry>

            <entry>enable</entry>
          </row>

          <row>
            <entry>started</entry>

            <entry>Any</entry>

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

    <para>The following actions occur when an interface goes down:</para>

    <informaltable>
      <tgroup cols="3">
        <tbody>
          <row>
            <entry><emphasis role="bold">FIREWALL STATE</emphasis></entry>

            <entry><emphasis role="bold">INTERFACE</emphasis></entry>

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

          <row>
            <entry>Any</entry>

            <entry>Required</entry>

            <entry>stop</entry>
          </row>

          <row>
            <entry>stopped</entry>

            <entry>Optional</entry>

            <entry>start</entry>
          </row>

          <row>
            <entry>started</entry>

            <entry>Optional</entry>

            <entry>disable</entry>
          </row>

          <row>
            <entry>started</entry>

            <entry>Any</entry>

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

    <para>For optional interfaces, the
    <filename>/var/lib/<replaceable>product</replaceable>/<replaceable>interface</replaceable>.state</filename>
    files are maintained to reflect the state of the interface so that they
    may be used by the standard <firstterm>isusable</firstterm> script. Please
    note that the action is carried out using the current compiled script; the
    configuration is not recompiled.</para>

    <para>A new option has been added to <filename>shorewall.conf</filename>
    and <filename>shorewall6.conf</filename>. The REQUIRE_INTERFACE option
    determines the outcome when an attempt to start/restart/restore/refresh
    the firewall is made and none of the optional interfaces are available.
    With REQUIRE_INTERFACE=No (the default), the operation is performed. If
    REQUIRE_INTERFACE=Yes, then the operation fails and the firewall is placed
    in the stopped state. This option is suitable for a laptop with both
    ethernet and wireless interfaces. If either come up, the firewall starts.
    If neither comes up, the firewall remains in the stopped state.</para>

    <para>Similarly, if an optional interface goes down and there are no
    optional interfaces remaining in the up state, then the firewall is
    stopped.</para>

    <para>On Debian-based systems, during system shutdown the firewall is
    opened prior to network shutdown (<command>/etc/init.d/shorewall
    stop</command> performs a 'clear' operation rather than a 'stop'). This is
    required by Debian standards. You can change this default behavior by
    setting SAFESTOP=1 in <filename>/etc/default/shorewall</filename>
    (<filename>/etc/default/shorewall6</filename>, ...).</para>
  </section>
</article>