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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
<article>
<!--$Id$-->
<articleinfo>
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<title>Issues when Upgrading to Shorewall 4.4 (Upgrading from Debian Lenny
to Squeeze)</title>
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<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2009</year>
<year>2010</year>
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<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>Debian Lenny includes Shorewall version 4.0.15 while Squeeze
includes Shorewall 4.4. Because there are significant differences between
the two product versions, some users may experience upgrade issues. This
article outlines those issues and offers advice for dealing with
them.</para>
<note>
<para>Although this article is targeted specifically at Lenny -&gt;
Squeeze upgrades, it should be useful to any Shorewall-shell user
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upgrading to Shorewall 4.4.x. Footnotes are used to flag areas where
non-Debian users may experience different results.</para>
</note>
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</section>
<section id="Packages">
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<title>Packaging Differences</title>
<para>The first key difference between Shorewall 4.0 and Shorewall 4.4 is
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in the packaging<footnote>
<para>Most distributions use a similar packaging structure. Note,
however, that the 'shorewall' package in Simon Mater's RPMs for
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RedHat/Fedora/CentOS is like the Lenny shorewall-common
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package.</para>
</footnote>. In Lenny, there are six Shorewall packages:</para>
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<orderedlist>
<listitem>
<para>shorewall-common — Contains the basic components needed to
create an IPv4 firewall.</para>
</listitem>
<listitem>
<para>shorewall-shell — The legacy Shorewall configuration compiler
written in Bourne shell.</para>
</listitem>
<listitem>
<para>shorewall — A transitional package that depends on
shorewall-common and shorewall-shell. Installing this package installs
both shorewall-common and shorewall-shell.</para>
</listitem>
<listitem>
<para>shorewall-perl — A re-implementation of the Shorewall
configuration compiler in Perl. This compiler has many advantages over
the shell-based compiler:</para>
<itemizedlist>
<listitem>
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<para>The compiler is much faster</para>
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</listitem>
<listitem>
<para>The compiler does a much better job of validating the
configuration, thus avoiding run-time errors.</para>
</listitem>
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<listitem>
<para>The compiler produces better and more consistent diagnostic
messages.</para>
</listitem>
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<listitem>
<para>The compiler produces a script that runs much faster and
that does not reject/drop connections during start/restart.</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>shorewall-lite — A small package that can run scripts generated
by shorewall-shell or shorewall-perl. Allows centralized firewall
administration.</para>
</listitem>
<listitem>
<para>shorewall-doc — Documentation.</para>
</listitem>
</orderedlist>
<para>In Squeeze, there are six slightly different packages:</para>
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<orderedlist>
<listitem>
<para>shorewall — Contains everything needed to create an IPv4
firewall. It combines the former shorewall-common and shorewall-perl
packages.</para>
</listitem>
<listitem>
<para>shorewall6 — Depends on shorewall. Adds those components needed
to create an IPv6 firewall.</para>
</listitem>
<listitem>
<para>shorewall-lite — Same as in Lenny; only runs IPv4 firewall
scripts.</para>
</listitem>
<listitem>
<para>shorewall6-lite — Similar to shorewall-lite, except that it only
runs IPv6 firewall scripts.</para>
</listitem>
<listitem>
<para>shorewall-init — Allows the firewall to be closed before
interfaces are brought up and also allows the firewall to react to
interfaces coming up and going down.</para>
</listitem>
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<listitem>
<para>shorewall-doc — Documentation.</para>
</listitem>
</orderedlist>
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<warning>
<para>Do not purge the old packages (shorewall-common, shorewall-shell
and shorewall-perl) until after the new shorewall package has been
installed.</para>
</warning>
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<para>The key change in Squeeze that may produce upgrade issues is that
Squeeze does not include the shell-based configuration compiler. As a
consequence, unless you are already using Shorewall-perl on Lenny, an
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upgrade from Lenny to Squeeze will mean that you will be switching from
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the old shell-based compiler to the new Perl-based compiler<footnote>
<para>Note that Perl is a required package on Debian. If you are
running an embedded distribution which does not include Perl and it is
not feasible to install Perl on your firewall, then you should
consider installing Shorewall on another system in your network (may
be a <trademark>Windows</trademark> system running
<trademark>Cygwin</trademark> or an <trademark>Apple</trademark>
<trademark>MacIntosh</trademark> running OS X) and installing
Shorewall-lite on your firewall.</para>
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</footnote>. While the two compilers are highly compatible, there are
some differences. Those differences are detailed in the following
sections.</para>
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</section>
<section id="Issues">
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<title>Issues Most Likely to Cause Problems or Concerns</title>
<section id="conf">
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<title>shorewall.conf</title>
<para>As always, when upgrading from one major release of Shorewall to
another, the installer will prompt you about replacing your existing
<filename>shorewall.conf</filename> with the updated one from the
package. Shorewall is designed with the assumption that users will never
replace shorewall.conf and retaining your existing file will always
produce upward-compatible behavior.</para>
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<para>That having been said, there are a few settings that you may have
in your shorewall.conf that will cause compilation warning or error
messages after the upgrade.</para>
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<variablelist>
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<varlistentry>
<term>BLACKLISTNEWONLY</term>
<listitem>
<para>If you have BLACKLISTNEWONLY=No together with
FASTACCEPT=Yes, you will receive this error:</para>
<para><emphasis role="bold">ERROR: BLACKLISTNEWONLY=No may not be
specified with FASTACCEPT=Yes</emphasis></para>
<para>To eliminate the error, reverse the setting of one of the
options.</para>
<note>
<para>This combination never worked correctly in earlier
versions -- to duplicate the earlier behavior, you will want to
set BLACKLISTNEWONLY=Yes.</para>
</note>
</listitem>
</varlistentry>
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<varlistentry>
<term>BRIDGING</term>
<listitem>
<para>If you have set this option to Yes, you will receive the
following error:</para>
<para><emphasis role="bold">ERROR: BRIDGING=Yes is not supported
by Shorewall 4.4.x</emphasis></para>
<para>You should not be receiving this error if you are upgrading
from Lenny since BRIDGING=Yes did not work in that release
either<footnote>
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<para>If you are upgrading from a release using a kernel
earlier than 2.6.20, then BRIDGING=Yes did work correctly with
Shorewall-shell.</para>
</footnote>. If you have a bridge configuration where you want
to control connections through the bridge, you will want to visit
<ulink
url="http://www.shorewall.net/bridge-Shorewall-perl.html">http://www.shorewall.net/bridge-Shorewall-perl.html</ulink><footnote>
<para>Kernel 2.6.20 or later is required.</para>
</footnote>.</para>
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</listitem>
</varlistentry>
<varlistentry>
<term>DELAYBLACKLISTLOAD</term>
<listitem>
<para>If you have set this option to Yes, you will receive the
following warning:</para>
<para><emphasis role="bold">WARNING: DELAYBLACKLIST=Yes is not
supported by Shorewall 4.4.x</emphasis></para>
<para>To eliminate the warning, set DELAYBLACKLISTLOAD=No or
remove the setting altogether.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>DYNAMIC_ZONES</term>
<listitem>
<para>If you have set this option to Yes, you will receive the
following warning:</para>
<para><emphasis role="bold">WARNING: DYNAMIC_ZONES=Yes is not
supported by Shorewall 4.4.x</emphasis></para>
<para>To eliminate the warning, set DYNAMIC_ZONES=No or remove the
setting altogether. See <ulink url="Dynamic.html">this
article</ulink> to learn how to set up Dynamic Zones under
Shorewall 4.4.</para>
</listitem>
</varlistentry>
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<varlistentry id="FW">
<term>FW</term>
<listitem>
<para>If a setting for FW appears in your shorewall.conf file, you
will receive this warning:</para>
<para><emphasis role="bold">WARNING: Unknown configuration option
(FW) ignored.</emphasis></para>
<para>Remove the setting from the file and modify your
<filename>/etc/shorewall/zones</filename> file as described <link
linkend="zones">below</link>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>IPSECFILE</term>
<listitem>
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<para>If you have specified IPSECFILE=ipsec or IPSECFILE= or if
you do not have a setting for IPSECFILE, then you will receive the
following error:</para>
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<para><emphasis role="bold">ERROR: IPSECFILE=ipsec is not
supported by Shorewall 4.4.x</emphasis></para>
<para>To eliminate the warning, you will need to:</para>
<orderedlist>
<listitem>
<para>Set IPSECFILE=zones</para>
</listitem>
<listitem>
<para>Modify your <filename>/etc/shorewall/zones</filename>
file as described <link linkend="zones">below</link>.</para>
</listitem>
</orderedlist>
</listitem>
</varlistentry>
<varlistentry>
<term>PKTTYPE</term>
<listitem>
<para>The PKTTYPE option is ignored by Shorewall-perl.
Shorewall-perl will use Address type match if it is available;
otherwise, it will behave as if PKTTYPE=No had been
specified.</para>
</listitem>
</varlistentry>
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<varlistentry>
<term>RFC1918_LOG_LEVEL</term>
<listitem>
<para>If you have specified any setting for this option, you will
receive the following warning:</para>
<para><emphasis role="bold">WARNING: RFC1918_LOG_LEVEL=value
ignored. The 'norfc1918' interface/host option is no longer
supported.</emphasis></para>
<para>To eliminate the warning, set RFC1918_LOG_LEVEL= or simply
remove the setting altogether.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>RFC1918_STRICT</term>
<listitem>
<para>If you have set this option to Yes, you will receive the
following warning:</para>
<para><emphasis role="bold">WARNING: RFC1918_STRICT=Yes is not
supported by Shorewall 4.4.x</emphasis></para>
<para>To eliminate the warning, set RFC1918_STRICT=No or remove
the setting altogether.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>SAVE_IPSETS</term>
<listitem>
<para>Shorewall 4.4.0-4.4.5 will issue a warning if you set
SAVE_IPSETS=Yes in <filename>shorewall.conf</filename>:</para>
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<para><emphasis role="bold">WARNING SAVE_IPSETS=Yes is not
supported by Shorewall 4.4.x</emphasis></para>
<para>To eliminate this message, you will need to set
SAVE_IPSETS=No or remove the setting altogether.</para>
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<para>See <link linkend="ipsets">below</link> for additional
information regarding ipsets in Shorewall 4.4.</para>
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</listitem>
</varlistentry>
<varlistentry>
<term>SHOREWALL_COMPILER</term>
<listitem>
<para>If you have specified SHOREWALL_COMPILER=shell, you will
receive the following warning message:</para>
<para><emphasis role="bold">WARNING: SHOREWALL_COMPILER=shell
ignored. Shorewall-shell support has been removed in this
release</emphasis></para>
<para>To eliminate the warning, set SHOREWALL_COMPILER=perl or
simply remove the setting altogether.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>USE_ACTIONS</term>
<listitem>
<para>If you have set this option to No, you will receive the
following warning:</para>
<para><emphasis role="bold">WARNING: USE_ACTIONS=No is not
supported by Shorewall 4.4.x</emphasis></para>
<para>To eliminate the warning, set USE_ACTIONS=Yes or remove the
setting altogether.</para>
</listitem>
</varlistentry>
</variablelist>
</section>
<section id="zones">
<title>/etc/shorewall/zones</title>
<para>If the column headings in your /etc/shorewall/zones file look like
this:</para>
<programlisting>#ZONE DISPLAY COMMENTS
net Net The big bad net
loc Local The local LAN</programlisting>
<para>then you are using the original zones file format that has been
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deprecated since Shorewall 3.0.</para>
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<para>You will need to convert to the new file format which has the
following headings:</para>
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<programlisting>#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS</programlisting>
<para>You will need to add an entry for your firewall zone. The default
name for the firewall zone is 'fw' but may have been overriden in your
old configuration using <link linkend="FW">the FW option in
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<filename>shorewall.conf</filename></link>.</para>
<programlisting>#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall</programlisting>
<para>The remainder of your zones will have type 'ipv4' unless they are
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mentioned in your /etc/shorewall/ipsec file (see <link
linkend="ipsec">below</link>).</para>
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<programlisting>#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall
net ipv4 # The big bad net
loc ipv4 # The local LAN</programlisting>
</section>
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<section id="ipsec">
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<title>/etc/shorewall/ipsec</title>
<para>This file is no longer used -- its specifications are now included
in <filename>/etc/shorewall/zones</filename>.</para>
<para>Take this example:</para>
<programlisting>#ZONE IPSEC OPTIONS IN OUT
# ONLY OPTIONS OPTIONS
ipsec1 Yes
ipsec2 No</programlisting>
<para>This would translate to the following entries in
<filename>/etc/shorewall/zones</filename>:</para>
<programlisting>#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
ipsec1 ipsec4
ipsec2 ipv4</programlisting>
<para>Any OPTIONS, IN OPTIONS and OUT OPTIONS should simply be copied
from <filename>/etc/shorewall/ipsec</filename> to
<filename>/etc/shorewall/zones</filename>.</para>
</section>
<section id="interfaces">
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<title>/etc/shorewall/interfaces</title>
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<para>The BROADCAST column is essentially unused in Squeeze. If it
contains anything except 'detect' or '-', then you will receive this
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warning<footnote>
<para>Users whose kernel and/or iptables do not include Address Type
Match Support can continue to list broadcast addresses in this
column; no warning will be issued.</para>
</footnote>:</para>
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<blockquote>
<para><emphasis role="bold">WARNING: Shorewall no longer uses
broadcast addresses in rule generation when Address Type Match is
available</emphasis></para>
</blockquote>
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<para>To eliminate the warning, replace the contents of the BROADCAST
column with '-' or 'detect'.</para>
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<para>The 'norfc1918' option has been removed. If you specify the
option, you will receive the following warning:</para>
<blockquote>
<para><emphasis role="bold">WARNING: Support for the norfc1918
interface option has been removed from Shorewall</emphasis></para>
</blockquote>
<para>To eliminate the warning, simply remove the 'norfc1918' option
from the OPTIONS list. You may wish to consider NULL_ROUTE_RFC1918=Yes
as a replacement (see <ulink
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url="manpages/shorewall.conf.html">shorewall.conf</ulink> (5)).</para>
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</section>
<section id="hosts">
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<title>/etc/shorewall/hosts</title>
<para>The 'norfc1918' option has been removed. If you specify the
option, you will receive the following warning:</para>
<blockquote>
<para><emphasis role="bold">WARNING: The 'norfc1918' option is no
longer supported</emphasis></para>
</blockquote>
<para>To eliminate the warning, simply remove the 'norfc1918' option
from the OPTIONS list. You may wish to consider NULL_ROUTE_RFC1918=Yes
as a replacement (see <ulink
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url="manpages/shorewall.conf.html">shorewall.conf</ulink> (5)).</para>
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</section>
<section id="policy">
<title>/etc/shorewall/policy</title>
<para>Shorewall 4.4 detects dead policy file entries that result when an
entry is masked by an earlier more general entry.</para>
<para>Example:</para>
<programlisting>#SOURCE DEST POLICY LOG LEVEL
all all REJECT info
loc net ACCEPT</programlisting>
<para>Shorewall-shell silently accepted the above even though the
loc-&gt;net policy is useless. Shorewall-perl generates a fatal
compilation error:</para>
<blockquote>
<para><emphasis role="bold">ERROR: Policy "loc net ACCEPT" duplicates
earlier policy "all all REJECT"</emphasis></para>
</blockquote>
</section>
<section id="masq">
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<title>/etc/shorewall/masq</title>
<para>There is a long tradition of specifying an interface name in the
SOURCE column of this file.</para>
<para>Masquerading/SNAT occurs in the Netfilter POSTROUTING chain where
an incoming interface may not be specified in iptables rules.
Consequently, while processing the <command>shorewall start</command>
and <command>shorewall restart</command> commands, the generated script
must examine the firewall's main routing table to determine those
networks that are routed out of the interface; the script then adds a
MASQUERADE/SNAT rule for connections from each of those networks. This
additional processing requires the named interface to be up and
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configured when Shorewall starts or restarts.</para>
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<para>Users often complain that Shorewall fails to start at boot time
because a VPN interface that is named as a masq SOURCE isn't up and
configured during boot.</para>
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<para>To emphasize this restriction, if an interface is named in the
SOURCE column of one or more entries, a single warning is issued as
follows:</para>
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<blockquote>
<para><emphasis role="bold">WARNING: Using an interface as the masq
SOURCE requires the interface to be up and configured when Shorewall
starts/restarts</emphasis></para>
</blockquote>
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<para>To suppress this warning, replace the interface name with the list
of networks that are routed out of the interface.</para>
<para>Example.</para>
<para>Existing entry:</para>
<programlisting>#INTERFACE SOURCE ADDRESS PROTO PORT(S) IPSEC MARK USER/
# GROUP
eth0 eth1</programlisting>
<para>Current routing configuration:</para>
<programlisting>gateway:~# ip route ls dev eth1
<emphasis role="bold">172.20.1.0/24</emphasis> proto kernel scope link src 172.20.1.254
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224.0.0.0/4 scope link
gateway:~#
</programlisting>
<para>Replacement entry:</para>
<programlisting>#INTERFACE SOURCE ADDRESS PROTO PORT(S) IPSEC MARK USER/
# GROUP
eth0 <emphasis role="bold">172.20.1.0/24</emphasis></programlisting>
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<para>Note that no entry is included for 224.0.0.0/4 since that is the
multicast IP range and there should never be any packets with a SOURCE
IP address in that network.</para>
</section>
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<section id="rules">
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<title>/etc/shorewall/rules</title>
<para>If you include a destination zone in a 'nonat' rule, Shorewall
issues the following warning:</para>
<blockquote>
<para><emphasis role="bold">WARNING: Destination zone (zonename)
ignored.</emphasis></para>
</blockquote>
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<para>Nonat rules include:</para>
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<blockquote>
<simplelist>
<member>DNAT-</member>
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<member>REDIRECT-</member>
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<member>NONAT</member>
</simplelist>
</blockquote>
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<para>To eliminate the warning, remove the DEST zone.</para>
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<para>Example.</para>
<para>Before:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/ MARK CONNLIMIT TIME
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# PORT(S) PORT(S) DEST LIMIT GROUP
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NONAT loc net tcp 80</programlisting>
<para>After:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/ MARK CONNLIMIT TIME
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# PORT(S) PORT(S) DEST LIMIT GROUP
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NONAT loc - tcp 80</programlisting>
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<para>Shorewall 4.4 versions prior to 4.4.19 do not support icmp type
lists in the DEST PORT(S) column. Only a single ICMP type may be listed.
If you have a shell variable with a list of ICMP types that you use in a
rule, you can work around this limitation as follows. Replace this
rule:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/ MARK CONNLIMIT TIME
# PORT(S) PORT(S) DEST LIMIT GROUP
ACCEPT z1 z2 icmp $ITYPES</programlisting>
<para>with:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/ MARK CONNLIMIT TIME
# PORT(S) PORT(S) DEST LIMIT GROUP
BEGIN SHELL
for type in $ITYPES; do
ACCEPT z1 z2 icmp $type
done
END SHELL</programlisting>
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</section>
<section id="routestopped">
<title>/etc/shorewall/routestopped</title>
<para>The 'critical' option is no longer needed and hence is no longer
supported. If you have critical hosts defined, you will receive this
warning:</para>
<blockquote>
<para><emphasis role="bold">WARNING: The 'critical' option is no
longer supported (or needed)</emphasis></para>
</blockquote>
<para>To suppress the warning, simply remove the option.</para>
<para>Shorewall 4.4 also treats the <filename>routestopped</filename>
file differently from earlier releases. Previously, the
<filename>routestopped</filename> file was parsed during
<command>shorewall stop</command> processing so that changes made to the
file while Shorewall was running would be applied at the next
<command>stop</command>. This is no longer the case -- the
<filename>routestopped</filename> file is processed during compilation
just like the rest of the configuration files so that when
<command>shorewall stop</command> is issued, the firewall will pass
traffic based on the contents of the <filename>routestopped</filename>
file at the last <command>start</command> or
<command>restart</command>.</para>
<para>If you change the <filename>routestopped</filename> file and now
want to stop the firewall, you can run this sequence of commands:</para>
<programlisting><command>shorewall compile
shorewall stop</command></programlisting>
</section>
<section id="tos">
<title>/etc/shorewall/tos</title>
<para>The <filename>/etc/shorewall/tos</filename> file now has
zone-independent SOURCE and DEST columns as do all other files except
the rules and policy files.</para>
<para>The SOURCE column may be one of the following:</para>
<simplelist>
<member>[<command>all</command>:]&lt;<replaceable>address</replaceable>&gt;[,...]</member>
<member>[<command>all</command>:]&lt;<replaceable>interface</replaceable>&gt;[:&lt;<replaceable>address</replaceable>&gt;[,...]]</member>
<member><command>$FW</command>[:&lt;<replaceable>address</replaceable>&gt;[,...]]</member>
</simplelist>
<para>The DEST column may be one of the following:</para>
<simplelist>
<member>[<command>all</command>:]&lt;<replaceable>address</replaceable>&gt;[,...]</member>
<member>[<command>all</command>:]&lt;<replaceable>interface</replaceable>&gt;[:&lt;<replaceable>address</replaceable>&gt;[,...]]</member>
</simplelist>
<para>This is a permanent change. The old zone-based rules have never
worked right and this is a good time to replace them. We have tried to
make the new syntax cover the most common cases without requiring change
to existing files. In particular, it will handle the
<filename>tos</filename> file released with Shorewall 1.4 and
earlier.</para>
</section>
<section id="extension">
<title>Extension Scripts</title>
<para>With the shell-based compiler, all extension scripts were copied
into the compiled script and executed at run-time. In some cases, this
approach doesn't work with Shorewall Perl because (almost) the entire
rule set is built by the compiler. As a result, Shorewall-perl runs some
extension scripts at compile-time rather than at run-time. Because the
compiler is written in Perl, these extension scripts from earlier
versions will no longer work.</para>
<para>The following table summarizes when the various extension scripts
are run:<informaltable align="left" frame="none">
<tgroup cols="3">
<tbody>
<row>
<entry><emphasis role="bold">Compile-time (Must be written in
Perl)</emphasis></entry>
<entry><emphasis role="bold">Run-time</emphasis></entry>
<entry><emphasis role="bold">Eliminated</emphasis></entry>
</row>
<row>
<entry>initdone</entry>
<entry>clear</entry>
<entry>continue</entry>
</row>
<row>
<entry>maclog</entry>
<entry>init</entry>
<entry></entry>
</row>
<row>
<entry>Per-chain (including those associated with
actions)</entry>
<entry>start</entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry>started</entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry>stop</entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry>stopped</entry>
<entry></entry>
</row>
<row>
<entry></entry>
<entry>tcclear</entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</informaltable></para>
<para>Compile-time extension scripts are executed using the Perl 'eval
`cat &lt;file&gt;`' mechanism. Be sure that each script returns a 'true'
value; otherwise, the Shorewall-perl compiler will assume that the
script failed and will abort the compilation.</para>
<para>When a script is invoked, the <emphasis
role="bold">$chainref</emphasis> scalar variable will usually hold a
reference to a chain table entry.</para>
<simplelist>
<member><emphasis role="bold">$chainref-&gt;{name}</emphasis> contains
the name of the chain</member>
<member><emphasis role="bold">$chainref-&gt;{table}</emphasis> holds
the table name</member>
</simplelist>
<para>To add a rule to the chain:</para>
<simplelist>
<member>add_rule $chainref,
<replaceable>the-rule</replaceable></member>
</simplelist>
<para>Where</para>
<simplelist>
<member><replaceable>the rule</replaceable> is a scalar argument
holding the rule text. Do not include "-A
<replaceable>chain-name</replaceable>"</member>
</simplelist>
<para>Example:</para>
<simplelist>
<member>add_rule $chainref, '-j ACCEPT';</member>
</simplelist>
<para>To insert a rule into the chain:</para>
<simplelist>
<member>insert_rule $chainref, <replaceable>rulenum</replaceable>,
<replaceable>the-rule</replaceable></member>
</simplelist>
<para>The log_rule_limit function works like it does in the shell
compiler with three exceptions:</para>
<itemizedlist>
<listitem>
<para>You pass the chain reference rather than the name of the
chain.</para>
</listitem>
<listitem>
<para>The commands are 'add' and 'insert' rather than '-A' and
'-I'.</para>
</listitem>
<listitem>
<para>There is only a single "pass as-is to iptables" argument (so
you must quote that part</para>
</listitem>
</itemizedlist>
<para>Example:</para>
<programlisting> log_rule_limit
'info' ,
$chainref ,
$chainref-&gt;{name},
'DROP' ,
'', #Limit
'' , #Log tag
'add'
'-p tcp '; </programlisting>
<para>Here is an example of an actual initdone script used with
Shorewall 3.4:<programlisting>run_iptables -t mangle -I PREROUTING -p esp -j MARK --set-mark 0x50
run_iptables -t filter -I INPUT -p udp --dport 1701 -m mark --mark 0x50 -j ACCEPT
run_iptables -t filter -I OUTPUT -p udp --sport 1701 -j ACCEPT
</programlisting></para>
<para>Here is the corresponding script used with Shorewall
4.4:<programlisting>use Shorewall::Chains;
insert_rule $mangle_table-&gt;{PREROUTING}, 1, "-p esp -j MARK --set-mark 0x50";
insert_rule $filter_table-&gt;{INPUT}, 1, "-p udp --dport 1701 -m mark --mark 0x50 -j ACCEPT";
insert_rule $filter_table-&gt;{OUTPUT}, 1, "-p udp --sport 1701 -j ACCEPT";
1;</programlisting></para>
<para>The initdone script is unique because the $chainref variable is
not set before the script is called. The above script illustrates how
the $mangle_table, $filter_table, and $nat_table references can be used
to add or insert rules in arbitrary chains.</para>
</section>
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<section id="ipsets">
<title>Ipsets</title>
<para>Shorewall 4.4 insists that ipset names begin with a letter and be
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composed of alphanumeric characters, underscores (_) and dashes (-).
When used in a Shorewall configuration file, the name must be preceded
by a plus sign (+) as with the shell-based compiler.</para>
<para>Shorewall 4.4.6 re-introduced SAVE_IPSETS=Yes with slightly
different semantics:</para>
<itemizedlist>
<listitem>
<para>The contents of the ipsets are saved during processing of the
<command>stop</command> command in addition to during processing of
the <command>save</command> command.</para>
</listitem>
<listitem>
<para>The contents of the ipsets are restored during processing of
the <command>start</command> command in addition to during
processing of the <command>restore</command> command. When
<command>restore</command> is being run when Shorewall is not in the
stopped state (such as when it is run to recover from a failed
<command>start</command>, <command>restart</command> or
<command>refresh</command>) ipsets are not restored.</para>
</listitem>
<listitem>
<para>Specifying an ipset in <ulink
url="manpages/shorewall-routestopped.html">shorewall-routestopped
</ulink>(5) is prohibited when SAVE_IPSETS=Yes.</para>
</listitem>
</itemizedlist>
</section>
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<section id="SimpleTC">
<title>Simple Traffic Shaping</title>
<para>If you find that output bandwidth is extremely limited, it is
likely due to TCP Segmentation Offload (TSO) and/or Generic Segmentation
Offload (GSO) being enabled in the network adapter. To verify that,
install the <firstterm>ethtool</firstterm> package and use the -k
command:</para>
<programlisting>root@gateway:~# ethtool -k eth1
Offload parameters for eth1:
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp-segmentation-offload: <emphasis role="bold">on</emphasis>
udp-fragmentation-offload: off
generic-segmentation-offload: <emphasis role="bold">on</emphasis>
generic-receive-offload: off
large-receive-offload: off
ntuple-filters: off
receive-hashing: off
root@gateway:~#</programlisting>
<para>If that is the case, you can correct the problem by adjusting the
<replaceable>minburst</replaceable> setting in
/etc/shorewall/tcinterfaces. We suggest starting at 10-12kb and adjust
as necessary. Example:</para>
<programlisting>#INTERFACE TYPE IN-BANDWIDTH OUT-BANDWIDTH
eth0 External 50mbit:200kb 5.0mbit:100kb:200ms:100mbit:<emphasis
role="bold">10kb</emphasis>
</programlisting>
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<para>Alternatively, you can turn off TSO and GSO using this command in
<filename>/etc/shorewall/init</filename>:</para>
<programlisting><emphasis role="bold">ethtool -k eth<emphasis>N</emphasis> tso off gso off</emphasis></programlisting>
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</section>
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</section>
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<section id="Additional">
<title>Additional Sources of Information</title>
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<para>The following articles provide additional information.</para>
<itemizedlist>
<listitem>
<para><ulink url="Shorewall-perl.html#Incompatibilities">Shorewall
Perl Incompatibilities</ulink></para>
</listitem>
<listitem>
<para><ulink url="upgrade_issues.htm">Upgrade Issues</ulink></para>
</listitem>
</itemizedlist>
</section>
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</article>