mirror of
https://gitlab.com/shorewall/code.git
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be924ff765
Also removes deprecated Shorewall6/configfiles/masq Signed-off-by: Tuomo Soini <tis@foobar.fi> Signed-off-by: Tom Eastep <teastep@shorewall.net>
839 lines
34 KiB
XML
839 lines
34 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>shorewall-snat</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>Shorewall 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/shorewall[6]/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). It superseded <ulink
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url="shorewall-masq.html">shorewall-masq</ulink>(5) in Shorewall
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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="shorewall-rtrules.html">shorewall-rtrules</ulink>(5) or
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PREROUTING entries in <ulink
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url="shorewall-mangle.html">shorewall-mangle</ulink>(5) to do
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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. Beginning with Shorewall
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5.1.9, with the exception of NFLOG and ULOG, the action may be
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followed by a colon (":") and a <replaceable>log level</replaceable>
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(see <ulink
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url="shorewall-logging.html">shorewall-logging(5)</ulink>).</para>
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<para>Choices for ACTION are:</para>
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<variablelist>
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<varlistentry>
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<term><emphasis
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role="bold"><replaceable>action</replaceable></emphasis>[+][(<replaceable>parameter</replaceable>,...)][:<replaceable>level</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="shorewall-actions.html">shorewall-actions(5)</ulink>
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with the <option>nat</option> option. See <ulink
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url="../Actions.html">https://shorewall.org/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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<varlistentry>
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<term><emphasis
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role="bold">CONTINUE</emphasis>[+]:<replaceable>level</replaceable></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">LOG:<replaceable>level</replaceable></emphasis></term>
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<listitem>
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<para>Added in Shorewall 5.1.9. Simply log the packet and
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continue with the next rule.</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">MASQUERADE[+]</emphasis>[([<replaceable>lowport</replaceable>[-<replaceable>highport</replaceable>]][<option>random</option>])][:<replaceable>level</replaceable>]</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 only <replaceable>lowport</replaceable> is given,
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that port will be assigned, if possible. If option
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<option>random</option> is used then port mapping will be
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randomized. MASQUERADE should only be used when the DEST
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interface has a dynamic IP address. Otherwise, SNAT should be
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used and should specify the interface's static 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">NFLOG</emphasis>[(<replaceable>nflog-parameters</replaceable>)]</term>
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<listitem>
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<para>Added in Shorewall 5.1.9. Queues matching packets to a
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back end logging daemon via a netlink socket then continues to
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the next rule. See <ulink
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url="shorewall-logging.html">shorewall-logging(5)</ulink>.</para>
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<para>The <replaceable>nflog-parameters</replaceable> are a
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comma-separated list of up to 3 numbers:</para>
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<itemizedlist>
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<listitem>
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<para>The first number specifies the netlink group
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(0-65535). If omitted (e.g., NFLOG(,0,10)) then a value of
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0 is assumed.</para>
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</listitem>
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<listitem>
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<para>The second number specifies the maximum number of
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bytes to copy. If omitted, 0 (no limit) is assumed.</para>
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</listitem>
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<listitem>
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<para>The third number specifies the number of log
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messages that should be buffered in the kernel before they
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are sent to user space. The default is 1.</para>
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</listitem>
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</itemizedlist>
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<para>NFLOG is similar to<emphasis role="bold">
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LOG:NFLOG</emphasis>[(<replaceable>nflog-parameters</replaceable>)],
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except that the log level is not changed when this ACTION is
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used in an action or macro body and the invocation of that
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action or macro specifies a log level.</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>)[:<replaceable>level</replaceable>]</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="shorewall.conf.html">shorewall.conf</ulink>(5)
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then Shorewall will automatically add this address to the
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INTERFACE named in the first column (IPv4 only).</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.</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>Examples:</para>
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<programlisting> 192.0.2.4:5000-6000
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:4000-5000</programlisting>
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<para>You may also specify a single port number, which will be
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assigned to the outgoing connection, if possible.</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">ULOG</emphasis>[(<replaceable>ulog-parameters</replaceable>)]</term>
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<listitem>
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<para>IPv4 only. Added in Shorewall 5.1.9. Queues matching
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packets to a back end logging daemon via a netlink socket then
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continues to the next rule. See <ulink
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url="shorewall-logging.html">shorewall-logging(5)</ulink>.</para>
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<para>Similar to<emphasis role="bold">
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LOG:ULOG</emphasis>[(<replaceable>ulog-parameters</replaceable>)],
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except that the log level is not changed when this ACTION is
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used in an action or macro body and the invocation of that
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action or macro specifies a log level.</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="shorewall-nat.html">shorewall-nat</ulink>(5)). If you
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want the rule to be applied before one-to-one NAT rules, follow the
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action name with "+": This feature should only be required if you
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need to insert rules in this file that preempt entries in <ulink
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url="shorewall-nat.html">shorewall-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 masquerade. You can specify this
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as an <emphasis>address</emphasis> (net or host) or as an
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<emphasis>interface</emphasis>. Unless you want to perform SNAT in
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the INPUT chain (see DEST below), if you give the name of an
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interface (deprecated), the interface must be up before you start
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the firewall and the Shorewall rules compiler will warn you of that
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fact. (Shorewall will use your main routing table to determine the
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appropriate addresses to masquerade).</para>
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<para>The preferred way to specify the SOURCE is to supply one or
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more host or network addresses separated by comma. You may use ipset
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names 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>digit][,</emphasis><emphasis>interface</emphasis>[<emphasis
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role="bold">:</emphasis><emphasis>digit</emphasis>]]...|$FW}[<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>]]</term>
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<listitem>
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<para>Outgoing <emphasis>interface</emphasis>s and destination
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networks. Multiple interfaces may be listed when the ACTION is
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MASQUERADE, but this is usually just your internet interface. If
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ADD_SNAT_ALIASES=Yes in <ulink
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url="shorewall.conf.html">shorewall.conf</ulink>(5), you
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may add ":" and a <emphasis>digit</emphasis> to indicate that you
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want the alias added with that name (e.g., eth0:0). This will allow
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the alias to be displayed with ifconfig. <emphasis role="bold">That
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is the only use for the alias name; it may not appear in any other
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place in your Shorewall configuration.</emphasis></para>
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<para>Beginning with Shorewall 5.1.12, SNAT may be performed in the
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nat table's INPUT chain by specifying $FW rather than one or more
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interfaces. </para>
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<para>Each interface must match an entry in <ulink
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url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5).
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Shorewall allows loose matches to wildcard entries in <ulink
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url="shorewall-interfaces.html">shorewall-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="shorewall-interfaces.html">shorewall-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="shorewall-exclusion.html">shorewall-exclusion</ulink>(5))
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as are ipset names preceded by a plus sign '+';</para>
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<para>If you wish to inhibit the action of ADD_SNAT_ALIASES for this
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entry then include the ":" but omit the digit:</para>
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<programlisting> eth0(Avvanta):
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eth2::192.0.2.32/27</programlisting>
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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 here. See
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<ulink
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url="shorewall-rules.html">shorewall-rules(5)</ulink> for
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details.</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">PORT</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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|
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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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|
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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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|
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<listitem>
|
|
<para>IPSEC Encapsulation Protocol</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis
|
|
role="bold">mss=</emphasis><emphasis>number</emphasis></term>
|
|
|
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<listitem>
|
|
<para>sets the MSS field in TCP packets</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">mode=</emphasis><emphasis
|
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role="bold">transport</emphasis>|<emphasis
|
|
role="bold">tunnel</emphasis></term>
|
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|
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<listitem>
|
|
<para>IPSEC mode</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis
|
|
role="bold">tunnel-src=</emphasis><emphasis>address</emphasis>[/<emphasis>mask</emphasis>]</term>
|
|
|
|
<listitem>
|
|
<para>only available with mode=tunnel</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis
|
|
role="bold">tunnel-dst=</emphasis><emphasis>address</emphasis>[/<emphasis>mask</emphasis>]</term>
|
|
|
|
<listitem>
|
|
<para>only available with mode=tunnel</para>
|
|
</listitem>
|
|
</varlistentry>
|
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|
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<varlistentry>
|
|
<term><emphasis role="bold">strict</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Means that packets must match all rules.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">next</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Separates rules; can only be used with strict</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">yes</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>When used by itself, causes all traffic that will be
|
|
encrypted/encapsulated to match the rule.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">MARK</emphasis> - [<emphasis
|
|
role="bold">!</emphasis>]<emphasis>value</emphasis>[/<emphasis>mask</emphasis>][<emphasis
|
|
role="bold">:C</emphasis>]</term>
|
|
|
|
<listitem>
|
|
<para>Defines a test on the existing packet or connection mark. The
|
|
rule will match only if the test returns true.</para>
|
|
|
|
<para>If you don't want to define a test but need to specify
|
|
anything in the following columns, place a "-" in this field.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>!</term>
|
|
|
|
<listitem>
|
|
<para>Inverts the test (not equal)</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis>value</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Value of the packet or connection mark.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis>mask</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>A mask to be applied to the mark before testing.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">:C</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Designates a connection mark. If omitted, the packet
|
|
mark's value is tested.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">USER</emphasis> (Optional) - [<emphasis
|
|
role="bold">!</emphasis>][<emphasis>user-name-or-number</emphasis>][<emphasis
|
|
role="bold">:</emphasis><emphasis>group-name-or-number</emphasis>][<emphasis
|
|
role="bold">+</emphasis><emphasis>program-name</emphasis>]</term>
|
|
|
|
<listitem>
|
|
<para>This column was formerly labelled USER/GROUP.</para>
|
|
|
|
<para>Only locally-generated connections will match if this column
|
|
is non-empty.</para>
|
|
|
|
<para>When this column is non-empty, the rule matches only if the
|
|
program generating the output is running under the effective
|
|
<emphasis>user</emphasis> and/or <emphasis>group</emphasis>
|
|
specified (or is NOT running under that id if "!" is given).</para>
|
|
|
|
<para>Examples:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>joe</term>
|
|
|
|
<listitem>
|
|
<para>program must be run by joe</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>:kids</term>
|
|
|
|
<listitem>
|
|
<para>program must be run by a member of the 'kids'
|
|
group</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>!:kids</term>
|
|
|
|
<listitem>
|
|
<para>program must not be run by a member of the 'kids'
|
|
group</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>+upnpd</term>
|
|
|
|
<listitem>
|
|
<para>#program named upnpd</para>
|
|
|
|
<important>
|
|
<para>The ability to specify a program name was removed from
|
|
Netfilter in kernel version 2.6.14.</para>
|
|
</important>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><emphasis role="bold">SWITCH -
|
|
[!]<replaceable>switch-name</replaceable>[={0|1}]</emphasis></term>
|
|
|
|
<listitem>
|
|
<para>Added in Shorewall 4.5.1 and allows enabling and disabling the
|
|
rule without requiring <command>shorewall restart</command>.</para>
|
|
|
|
<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) Added in Shorewall 4.5.6. 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>IPv4 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 192.168.0.0/24.</para>
|
|
|
|
<para>Your entry in the file will be:</para>
|
|
|
|
<programlisting> #ACTION SOURCE DEST
|
|
MASQUERADE 192.168.0.0/24 eth0</programlisting>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>IPv4 Example 2:</term>
|
|
|
|
<listitem>
|
|
<para>You add a router to your local network to connect subnet
|
|
192.168.1.0/24 which you also want to masquerade. You then add a
|
|
second entry for eth0 to this file:</para>
|
|
|
|
<programlisting> #ACTION SOURCE DEST
|
|
MASQUERADE 192.168.0.0/24 eth0
|
|
MASQUERADE 192.168.1.0/24 eth0</programlisting>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>IPv4 Example 3:</term>
|
|
|
|
<listitem>
|
|
<para>You want all outgoing traffic from 192.168.1.0/24 through eth0
|
|
to use source address 206.124.146.176 which is NOT the primary
|
|
address of eth0. You want 206.124.146.176 to be added to eth0 with
|
|
name eth0:0.</para>
|
|
|
|
<programlisting> #ACTION SOURCE DEST
|
|
SNAT(206.124.146.176) 192.168.1.0/24 eth0:0</programlisting>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>IPv4 Example 4:</term>
|
|
|
|
<listitem>
|
|
<para>You want all outgoing SMTP traffic entering the firewall from
|
|
172.20.1.0/29 to be sent from eth0 with source IP address
|
|
206.124.146.177. You want all other outgoing traffic from
|
|
172.20.1.0/29 to be sent from eth0 with source IP address
|
|
206.124.146.176.</para>
|
|
|
|
<programlisting> #INTERFACE SOURCE ADDRESS PROTO DPORT
|
|
eth0 172.20.1.0/29 206.124.146.177 tcp smtp
|
|
eth0 172.20.1.0/29 206.124.146.176</programlisting>
|
|
|
|
<programlisting> #ACTION SOURCE DEST PROTO PORT
|
|
SNAT(206.124.146.177) 172.20.1.0/29 eth0 tcp smtp
|
|
SNAT(206.124.146.176) 172.20.1.0/29 eth0</programlisting>
|
|
|
|
<warning>
|
|
<para>The order of the above two rules is significant!</para>
|
|
</warning>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>IPv4 Example 5:</term>
|
|
|
|
<listitem>
|
|
<para>Connections leaving on eth0 and destined to any host defined
|
|
in the ipset <emphasis>myset</emphasis> should have the source IP
|
|
address changed to 206.124.146.177.</para>
|
|
|
|
<programlisting> #ACTION SOURCE DEST
|
|
SNAT(206.124.146.177) - eth0:+myset[dst]</programlisting>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>IPv4 Example 6:</term>
|
|
|
|
<listitem>
|
|
<para>SNAT outgoing connections on eth0 from 192.168.1.0/24 in
|
|
round-robin fashion between addresses 1.1.1.1, 1.1.1.3, and 1.1.1.9
|
|
(Shorewall 4.5.9 and later).</para>
|
|
|
|
<programlisting>/etc/shorewall/tcrules:
|
|
|
|
#ACTION SOURCE DEST PROTO DPORT SPORT USER TEST
|
|
1-3:CF 192.168.1.0/24 eth0 ; state=NEW
|
|
|
|
/etc/shorewall/snat:
|
|
|
|
#ACTION SOURCE DEST
|
|
SNAT(1.1.1.1) 192.168.1.0/24 eth0 { mark=1:C }
|
|
SNAT(1.1.1.3) 192.168.1.0/24 eth0 { mark=2:C }
|
|
SNAT(1.1.1.9) 192.168.1.0/24 eth0 { mark=3:C }</programlisting>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>IPv6 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>IPv6 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/shorewall/snat</para>
|
|
|
|
<para>/etc/shorewall6/snat</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See ALSO</title>
|
|
|
|
<para><ulink
|
|
url="../configuration_file_basics.htm#Pairs">https://shorewall.org/configuration_file_basics.htm#Pairs</ulink></para>
|
|
|
|
<para>shorewall(8)</para>
|
|
</refsect1>
|
|
</refentry>
|