shorewall_code/docs/Docker.xml

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  <articleinfo>
    <title>Docker Support</title>

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

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

      <author>
        <surname>J Cliff Armstrong</surname>
      </author>
    </authorgroup>

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

    <copyright>
      <year>2016</year>

      <year>2020</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>Shorewall 5.0.5 and Earlier</title>

    <para>Both Docker and Shorewall assume that they 'own' the iptables
    configuration. This leads to problems when Shorewall is restarted or
    reloaded, because it drops all of the rules added by Docker. Fortunately,
    the extensibility features in Shorewall allow users to <ulink
    url="https://blog.discourse.org/2015/11/shorewalldocker-two-great-tastes-that-taste-great-together/#">create
    their own solution</ulink> for saving the Docker-generated rules before
    these operations and restoring them afterwards.</para>
  </section>

  <section>
    <title>Shorewall 5.0.6 and Later</title>

    <para>Beginning with Shorewall 5.0.6, Shorewall has native support for
    simple Docker configurations. This support is enabled by setting
    DOCKER=Yes in shorewall.conf. With this setting, the generated script
    saves the Docker-created ruleset before executing a
    <command>stop</command>, <command>start</command>,
    <command>restart</command> or <command>reload</command> operation and
    restores those rules along with the Shorewall-generated ruleset.</para>

    <important>
      <para>Shorewall currently doesn't support Docker Swarm mode.</para>
    </important>

    <warning>
      <para>On Debian and Debian-derived systems, <command>systemctl restart
      shorewall</command> will lose Docker rules. You can work around this
      issue using a method provided by J Cliff Armstrong:</para>

      <para>Type as root:</para>

      <programlisting><command>systemctl edit shorewall.service</command></programlisting>

      <para>This will open the default terminal editor to a blank file in
      which you can paste the following:</para>

      <programlisting>[Service]
# reset ExecStop
ExecStop=
# set ExecStop to "stop" instead of "clear"
ExecStop=/sbin/shorewall $OPTIONS stop
</programlisting>

      <para> Then type <command>systemctl daemon-reload </command>to activate
      the changes. This change will survive future updates of the shorewall
      package from apt repositories. The override file itself will be saved to
      `/etc/systemd/system/shorewall.service.d/`. </para>
    </warning>

    <para>This support assumes that the default Docker bridge (docker0) is
    being used. It is recommended that this bridge be defined to Shorewall in
    <ulink
    url="manpages/shorewall-interfaces.html">shorewall-interfaces(8)</ulink>.
    As shown below, you can control inter-container communication using the
    <option>bridge</option> and <option>routeback</option> options. If docker0
    is not defined to Shorewall, then Shorewall will save and restore the
    FORWARD chain rules involving that interface.</para>

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

    <programlisting>DOCKER=Yes</programlisting>

    <para><filename>/etc/shorewall/zones</filename>:</para>

    <programlisting>#ZONE         TYPE        OPTIONS
dock          ipv4        #'dock' is just an example -- call it anything you like</programlisting>

    <para><filename>/etc/shorewall/policy</filename>:</para>

    <programlisting>#SOURCE        DEST        POLICY         LEVEL
dock           $FW         REJECT
dock           all         ACCEPT</programlisting>

    <para><filename>/etc/shorewall/interfaces</filename>:</para>

    <programlisting>#ZONE          INTERFACE        OPTIONS
dock           docker0          bridge   #Allow ICC (bridge implies routeback=1)</programlisting>

    <para>or</para>

    <programlisting>#ZONE          INTERFACE        OPTIONS
dock           docker0          bridge,routeback=0   #Disallow ICC</programlisting>
  </section>
</article>