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616 lines
24 KiB
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616 lines
24 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
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<refentry>
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<refmeta>
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<refentrytitle>shorewall6-masq</refentrytitle>
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<manvolnum>5</manvolnum>
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<refmiscinfo>Configuration Files</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>snat</refname>
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<refpurpose>Shorewall6 SNAT/Masquerade definition file</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>/etc/shorewall6/snat</command>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>This file is used to define dynamic NAT (Masquerading) and to define
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Source NAT (SNAT). While still supported, its use is deprecated in favor
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of <ulink url="shorewall6-snat.html">shorewall6-snat</ulink>(5) which was
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introduced in Shorewall 5.0.14.</para>
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<warning>
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<para>The entries in this file are order-sensitive. The first entry that
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matches a particular connection will be the one that is used.</para>
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</warning>
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<warning>
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<para>If you have more than one ISP link, adding entries to this file
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will <emphasis role="bold">not</emphasis> force connections to go out
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through a particular link. You must use entries in <ulink
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url="/manpages6/shorewall6-rtrules.html">shorewall6-rtrules</ulink>(5)
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or PREROUTING entries in <ulink
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url="/manpages6/shorewall6-tcrules.html">shorewall-tcrules</ulink>(5) to
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do that.</para>
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</warning>
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<para>The columns in the file are as follows.</para>
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<variablelist>
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<varlistentry>
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<term><emphasis role="bold">ACTION</emphasis></term>
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<listitem>
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<para>Defines the type of rule to generate. Choices are:</para>
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<variablelist>
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<varlistentry>
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<term><emphasis
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role="bold">MASQUERADE</emphasis>[+][([<replaceable>lowport</replaceable>-<replaceable>highport</replaceable>][<option>random</option>])]</term>
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<listitem>
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<para>Causes matching outgoing packages to have their source
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IP address set to the primary IP address of the interface
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specified in the DEST column. if
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<replaceable>lowport</replaceable>-<replaceable>highport</replaceable>
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is given, that port range will be used to assign a source
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port. If option <option>random</option> is used then port
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mapping will be randomized. MASQUERADE should only be used
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when the DEST interface has a dynamic IP address. Otherwise,
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SNAT should be used and should specify the interface's static
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address.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis
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role="bold">SNAT</emphasis>[+]([<emphasis>address-or-address-range</emphasis>][:<emphasis>lowport</emphasis><emphasis
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role="bold">-</emphasis><emphasis>highport</emphasis>][<emphasis
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role="bold">:random</emphasis>][:<option>persistent</option>]|<emphasis
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role="bold">detect</emphasis>|</term>
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<listitem>
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<para>If you specify an address here, matching packets will
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have their source address set to that address. If
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ADD_SNAT_ALIASES is set to Yes or yes in <ulink
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url="shorewall6.conf.html">shorewall6.conf</ulink>(5) then
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Shorewall will automatically add this address to the INTERFACE
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named in the first column.</para>
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<para>You may also specify a range of up to 256 IP addresses
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if you want the SNAT address to be assigned from that range in
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a round-robin fashion by connection. The range is specified by
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<emphasis>first.ip.in.range</emphasis>-<emphasis>last.ip.in.range</emphasis>.
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You may follow the port range with<emphasis role="bold">
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:random</emphasis> in which case assignment of ports from the
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list will be random. <emphasis role="bold">random</emphasis>
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may also be specified by itself in this column in which case
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random local port assignments are made for the outgoing
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connections.</para>
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<para>Example: 206.124.146.177-206.124.146.180</para>
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<para>You may follow the port range (or <emphasis
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role="bold">:random</emphasis>) with <emphasis
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role="bold">:persistent</emphasis>. This is only useful when
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an address range is specified and causes a client to be given
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the same source/destination IP pair. This feature replaces the
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SAME modifier which was removed from Shorewall in version
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4.4.0.</para>
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<para>You may also use the special value
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<option>detect</option> which causes Shorewall to determine
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the IP addresses configured on the interface named in the DEST
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column and substitute them in this column.</para>
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<para>Finally, you may also specify a comma-separated list of
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ranges and/or addresses in this column.</para>
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<para>DNS Names names are not allowed.</para>
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<para>Normally, Netfilter will attempt to retain the source
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port number. You may cause netfilter to remap the source port
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by following an address or range (if any) by ":" and a port
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range with the format
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<emphasis>lowport</emphasis>-<emphasis>highport</emphasis>. If
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this is done, you must specify "tcp", "udp", "dccp" or "stcp"
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in the PROTO column.</para>
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<para>Example:</para>
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<programlisting> [2001:470:a:787::2]:5000-6000</programlisting>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>CONTINUE[+]</term>
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<listitem>
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<para>Causes matching packets to be exempted from any
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following rules in the file.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis
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role="bold"><replaceable>action</replaceable></emphasis>[+][(<replaceable>parameter</replaceable>,...)]</term>
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<listitem>
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<para>where <replaceable>action</replaceable> is an action
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declared in <ulink
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url="shorewall6-actions.html">shorewall6-actions(5)</ulink>
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with the <option>nat</option> option. See <ulink
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url="/Actions.html">www.shorewall.net/Actions.html</ulink> for
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further information.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>Normally Masq/SNAT rules are evaluated after those for
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one-to-one NAT (defined in <ulink
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url="/manpages6/shorewall6-nat.html">shorewall6-nat</ulink>(5)). If
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you want the rule to be applied before one-to-one NAT rules, follow
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the action name with "+": This feature should only be required if
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you need to insert rules in this file that preempt entries in <ulink
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url="/manpages6/shorewall6-nat.html">shorewall6-nat</ulink>(5).</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">SOURCE</emphasis> (Optional) -
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[<emphasis>interface</emphasis>|<emphasis>address</emphasis>[<emphasis
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role="bold">,</emphasis><emphasis>address</emphasis>...][<emphasis>exclusion</emphasis>]]</term>
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<listitem>
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<para>Set of hosts that you wish to SNAT; one or more host or
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network addresses separated by comma. You may use ipset names
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preceded by a plus sign (+) to specify a set of hosts.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">DEST</emphasis> -
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{<emphasis>interface</emphasis>|[<emphasis
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role="bold">:</emphasis>[<emphasis>dest-address</emphasis>[<emphasis
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role="bold">,</emphasis><emphasis>dest-address</emphasis>]...[<emphasis>exclusion</emphasis>]]|?COMMENT}</term>
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<listitem>
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<para>Outgoing <emphasis>interface</emphasis>. This is usually your
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internet interface.</para>
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<para>The <replaceable>interface</replaceable> must match an entry
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in <ulink
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url="/manpages6/shorewall6-interfaces.html">shorewall6-interfaces</ulink>(5).
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Shorewall allows loose matches to wildcard entries in <ulink
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url="/manpages6/shorewall6-interfaces.html">shorewall6-interfaces</ulink>(5).
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For example, <filename class="devicefile">ppp0</filename> in this
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file will match a <ulink
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url="/manpages6/shorewall6-interfaces.html">shorewall6-interfaces</ulink>(5)
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entry that defines <filename
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class="devicefile">ppp+</filename>.</para>
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<para>Where <ulink url="/4.4/MultiISP.html#Shared">more that one
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internet provider share a single interface</ulink>, the provider is
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specified by including the provider name or number in
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parentheses:</para>
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<programlisting> eth0(Avvanta)</programlisting>
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<para>In that case, you will want to specify the interface's address
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for that provider as the SNAT parameter.</para>
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<para>The interface may be qualified by adding the character ":"
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followed by a comma-separated list of destination host or subnet
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addresses to indicate that you only want to change the source IP
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address for packets being sent to those particular destinations.
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Exclusion is allowed (see <ulink
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url="/manpages6/shorewall6-exclusion.html">shorewall6-exclusion</ulink>(5))
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as are ipset names preceded by a plus sign '+'.</para>
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<para>Comments may be attached to Netfilter rules generated from
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entries in this file through the use of ?COMMENT lines. These lines
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begin with ?COMMENT; the remainder of the line is treated as a
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comment which is attached to subsequent rules until another ?COMMENT
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line is found or until the end of the file is reached. To stop
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adding comments to rules, use a line containing only
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?COMMENT.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">PROTO</emphasis> (Optional) - {<emphasis
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role="bold">-</emphasis>|[!]{<emphasis>protocol-name</emphasis>|<emphasis>protocol-number</emphasis>}[,...]|+<replaceable>ipset</replaceable>}</term>
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<listitem>
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<para>If you wish to restrict this entry to a particular protocol
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then enter the protocol name (from protocols(5)) or number
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here.</para>
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<para>Beginning with Shorewall 4.5.12, this column can accept a
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comma-separated list of protocols.</para>
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<para>Beginning with Shorewall 4.6.0, an
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<replaceable>ipset</replaceable> name can be specified in this
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column. This is intended to be used with
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<firstterm>bitmap:port</firstterm> ipsets.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">DPORT</emphasis> (Optional) -
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{-|[!]<emphasis>port-name-or-number</emphasis>[,<emphasis>port-name-or-number</emphasis>]...|+<replaceable>ipset</replaceable>}</term>
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<listitem>
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<para>If the PROTO column specifies TCP (6), UDP (17), DCCP (33),
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SCTP (132) or UDPLITE (136) then you may list one or more port
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numbers (or names from services(5)) or port ranges separated by
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commas.</para>
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<para>Port ranges are of the form
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<emphasis>lowport</emphasis>:<emphasis>highport</emphasis>.</para>
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<para>Beginning with Shorewall 4.6.0, an
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<replaceable>ipset</replaceable> name can be specified in this
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column. This is intended to be used with
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<firstterm>bitmap:port</firstterm> ipsets.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">IPSEC</emphasis> (Optional) -
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[<emphasis>option</emphasis>[<emphasis
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role="bold">,</emphasis><emphasis>option</emphasis>]...]</term>
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<listitem>
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<para>If you specify a value other than "-" in this column, you must
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be running kernel 2.6 and your kernel and iptables must include
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policy match support.</para>
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<para>Comma-separated list of options from the following. Only
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packets that will be encrypted via an SA that matches these options
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will have their source address changed.</para>
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<variablelist>
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<varlistentry>
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<term><emphasis
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role="bold">reqid=</emphasis><emphasis>number</emphasis></term>
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<listitem>
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<para>where <emphasis>number</emphasis> is specified using
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setkey(8) using the 'unique:<emphasis>number</emphasis> option
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for the SPD level.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">spi=</emphasis><number></term>
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<listitem>
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<para>where <emphasis>number</emphasis> is the SPI of the SA
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used to encrypt/decrypt packets.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">proto=</emphasis><emphasis
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role="bold">ah</emphasis>|<emphasis
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role="bold">esp</emphasis>|<emphasis
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role="bold">ipcomp</emphasis></term>
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<listitem>
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<para>IPSEC Encapsulation Protocol</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis
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role="bold">mss=</emphasis><emphasis>number</emphasis></term>
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<listitem>
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<para>sets the MSS field in TCP packets</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">mode=</emphasis><emphasis
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role="bold">transport</emphasis>|<emphasis
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role="bold">tunnel</emphasis></term>
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<listitem>
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<para>IPSEC mode</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis
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role="bold">tunnel-src=</emphasis><emphasis>address</emphasis>[/<emphasis>mask</emphasis>]</term>
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<listitem>
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<para>only available with mode=tunnel</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis
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role="bold">tunnel-dst=</emphasis><emphasis>address</emphasis>[/<emphasis>mask</emphasis>]</term>
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<listitem>
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<para>only available with mode=tunnel</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">strict</emphasis></term>
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<listitem>
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<para>Means that packets must match all rules.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">next</emphasis></term>
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<listitem>
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<para>Separates rules; can only be used with strict</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">yes</emphasis></term>
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<listitem>
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<para>When used by itself, causes all traffic that will be
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encrypted/encapsulated to match the rule.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">MARK</emphasis> - [<emphasis
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role="bold">!</emphasis>]<emphasis>value</emphasis>[/<emphasis>mask</emphasis>][<emphasis
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role="bold">:C</emphasis>]</term>
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<listitem>
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<para>Defines a test on the existing packet or connection mark. The
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rule will match only if the test returns true.</para>
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<para>If you don't want to define a test but need to specify
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anything in the following columns, place a "-" in this field.</para>
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<variablelist>
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<varlistentry>
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<term>!</term>
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<listitem>
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<para>Inverts the test (not equal)</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis>value</emphasis></term>
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<listitem>
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<para>Value of the packet or connection mark.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis>mask</emphasis></term>
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<listitem>
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<para>A mask to be applied to the mark before testing.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">:C</emphasis></term>
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<listitem>
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<para>Designates a connection mark. If omitted, the packet
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mark's value is tested.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><emphasis role="bold">USER</emphasis> (Optional) - [<emphasis
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role="bold">!</emphasis>][<emphasis>user-name-or-number</emphasis>][<emphasis
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role="bold">:</emphasis><emphasis>group-name-or-number</emphasis>][<emphasis
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role="bold">+</emphasis><emphasis>program-name</emphasis>]</term>
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|
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<listitem>
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<para>Only locally-generated connections will match if this column
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is non-empty.</para>
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<para>When this column is non-empty, the rule matches only if the
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program generating the output is running under the effective
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<emphasis>user</emphasis> and/or <emphasis>group</emphasis>
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specified (or is NOT running under that id if "!" is given).</para>
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|
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<para>Examples:</para>
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|
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<variablelist>
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<varlistentry>
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<term>joe</term>
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|
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<listitem>
|
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<para>program must be run by joe</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>:kids</term>
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|
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<listitem>
|
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<para>program must be run by a member of the 'kids'
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group</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>!:kids</term>
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<listitem>
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<para>program must not be run by a member of the 'kids'
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group</para>
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</listitem>
|
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</varlistentry>
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<varlistentry>
|
|
<term>+upnpd</term>
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|
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<listitem>
|
|
<para>#program named upnpd</para>
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|
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<important>
|
|
<para>The ability to specify a program name was removed from
|
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Netfilter in kernel version 2.6.14.</para>
|
|
</important>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
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</listitem>
|
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</varlistentry>
|
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|
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<varlistentry>
|
|
<term><emphasis role="bold">SWITCH -
|
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[!]<replaceable>switch-name</replaceable>[={0|1}]</emphasis></term>
|
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|
|
<listitem>
|
|
<para>Added in Shorewall 4.5.1 and allows enabling and disabling the
|
|
rule without requiring <command>shorewall restart</command>.</para>
|
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|
|
<para>The rule is enabled if the value stored in
|
|
<filename>/proc/net/nf_condition/<replaceable>switch-name</replaceable></filename>
|
|
is 1. The rule is disabled if that file contains 0 (the default). If
|
|
'!' is supplied, the test is inverted such that the rule is enabled
|
|
if the file contains 0.</para>
|
|
|
|
<para>Within the <replaceable>switch-name</replaceable>, '@0' and
|
|
'@{0}' are replaced by the name of the chain to which the rule is a
|
|
added. The <replaceable>switch-name</replaceable> (after '@...'
|
|
expansion) must begin with a letter and be composed of letters,
|
|
decimal digits, underscores or hyphens. Switch names must be 30
|
|
characters or less in length.</para>
|
|
|
|
<para>Switches are normally <emphasis role="bold">off</emphasis>. To
|
|
turn a switch <emphasis role="bold">on</emphasis>:</para>
|
|
|
|
<simplelist>
|
|
<member><command>echo 1 >
|
|
/proc/net/nf_condition/<replaceable>switch-name</replaceable></command></member>
|
|
</simplelist>
|
|
|
|
<para>To turn it <emphasis role="bold">off</emphasis> again:</para>
|
|
|
|
<simplelist>
|
|
<member><command>echo 0 >
|
|
/proc/net/nf_condition/<replaceable>switch-name</replaceable></command></member>
|
|
</simplelist>
|
|
|
|
<para>Switch settings are retained over <command>shorewall
|
|
restart</command>.</para>
|
|
|
|
<para>Beginning with Shorewall 4.5.10, when the
|
|
<replaceable>switch-name</replaceable> is followed by
|
|
<option>=0</option> or <option>=1</option>, then the switch is
|
|
initialized to off or on respectively by the
|
|
<command>start</command> command. Other commands do not affect the
|
|
switch setting.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">ORIGDEST</emphasis> - [<emphasis
|
|
role="bold">-</emphasis>|<emphasis>address</emphasis>[,<emphasis>address</emphasis>]...[<emphasis>exclusion</emphasis>]|<emphasis>exclusion</emphasis>]</term>
|
|
|
|
<listitem>
|
|
<para>(Optional) This column may be included and may contain one or
|
|
more addresses (host or network) separated by commas. Address ranges
|
|
are not allowed. When this column is supplied, rules are generated
|
|
that require that the original destination address matches one of
|
|
the listed addresses. It is useful for specifying that SNAT should
|
|
occur only for connections that were acted on by a DNAT when they
|
|
entered the firewall.</para>
|
|
|
|
<para>This column was formerly labelled ORIGINAL DEST.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">PROBABILITY</emphasis> -
|
|
[<replaceable>probability</replaceable>]</term>
|
|
|
|
<listitem>
|
|
<para>Added in Shorewall 5.0.0. When non-empty, requires the
|
|
<firstterm>Statistics Match</firstterm> capability in your kernel
|
|
and ip6tables and causes the rule to match randomly but with the
|
|
given <replaceable>probability</replaceable>. The
|
|
<replaceable>probability</replaceable> is a number 0 <
|
|
<replaceable>probability</replaceable> <= 1 and may be expressed
|
|
at up to 8 decimal points of precision.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Examples</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>Example 1:</term>
|
|
|
|
<listitem>
|
|
<para>You have a simple 'masquerading' setup where eth0 connects to
|
|
a DSL or cable modem and eth1 connects to your local network with
|
|
subnet 2001:470:b:787::0/64</para>
|
|
|
|
<para>Your entry in the file will be:</para>
|
|
|
|
<programlisting> #ACTION SOURCE DEST
|
|
MASQUERADE 2001:470:b:787::0/64 eth0</programlisting>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>Example 2:</term>
|
|
|
|
<listitem>
|
|
<para>Your sit1 interface has two public IP addresses:
|
|
2001:470:a:227::1 and 2001:470:b:227::1. You want to use the
|
|
iptables statistics match to masquerade outgoing connections evenly
|
|
between these two addresses.</para>
|
|
|
|
<programlisting>/etc/shorewall/snat:
|
|
|
|
#ACTION SOURCE DEST
|
|
SNAT(2001:470:a:227::1) ::/0 sit1 { probability=0.50 }
|
|
SNAT(2001:470:a:227::2) ::/0 sit</programlisting>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>FILES</title>
|
|
|
|
<para>/etc/shorewall6/snat</para>
|
|
</refsect1>
|
|
</refentry>
|