shorewall_code/Shorewall/manpages/shorewall-mangle.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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<refentry>
  <refmeta>
    <refentrytitle>shorewall-mangle</refentrytitle>

    <manvolnum>5</manvolnum>

    <refmiscinfo>Configuration Files</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>mangle</refname>

    <refpurpose>Shorewall Packet marking/mangling rules file</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>/etc/shorewall[6]/mangle</command>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>This file was introduced in Shorewall 4.6.0 and replaces <ulink
    url="shorewall-tcrules.html">shorewall-tcrules(5)</ulink>. This
    file is only processed by the compiler if:</para>

    <para>Entries in this file cause packets to be marked as a means of
    classifying them for traffic control or policy routing.</para>

    <important>
      <para>Unlike rules in the <ulink
      url="shorewall-rules.html">shorewall-rules</ulink>(5) file,
      evaluation of rules in this file will continue after a match. So the
      final mark for each packet will be the one assigned by the LAST tcrule
      that matches.</para>

      <para>If you use multiple internet providers with the 'track' option, in
      /etc/shorewall/providers be sure to read the restrictions at <ulink
      url="../MultiISP.html">https://shorewall.org/MultiISP.html</ulink>.</para>
    </important>

    <para>The columns in the file are as follows (where the column name is
    followed by a different name in parentheses, the different name is used in
    the alternate specification syntax).</para>

    <variablelist>
      <varlistentry>
        <term><emphasis role="bold">ACTION</emphasis> -
        <replaceable>command</replaceable>[(<replaceable>parameters</replaceable>)][:<replaceable>chain-designator</replaceable>]</term>

        <listitem>
          <para>The <replaceable>chain-designator </replaceable>indicates the
          Netfilter chain that the entry applies to and may be one of the
          following:</para>

          <variablelist>
            <varlistentry>
              <term>P</term>

              <listitem>
                <para>PREROUTING chain.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>F</term>

              <listitem>
                <para>FORWARD chain.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>T</term>

              <listitem>
                <para>POSTROUTING chain.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>I</term>

              <listitem>
                <para>INPUT chain.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>NP</term>

              <listitem>
                <para>PREROUTING chain in the nat table.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>NI</term>

              <listitem>
                <para>INPUT chain in the nat table.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>NO</term>

              <listitem>
                <para>OUTPUT chain in the nat table.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>NT</term>

              <listitem>
                <para>POSTROUTING chain in the nat table.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>The nat table designators were added in Shorewall 5.2.1. When
          a nat table designator is given, only the CONNMARK, MARK, SAVE and
          RESTORE commands may be used.</para>

          <para>Unless otherwise specified for the particular
          <replaceable>command</replaceable>, the default chain is PREROUTING
          when MARK_IN_FORWARD_CHAIN=No in <ulink
          url="shorewall.conf.html">shorewall.conf(5)</ulink>, and
          FORWARD when MARK_IN_FORWARD_CHAIN=Yes.</para>

          <para>A <replaceable>chain-designator</replaceable> may not be
          specified if the SOURCE or DEST columns begin with '$FW'. When the
          SOURCE is $FW, the generated rule is always placed in the OUTPUT
          chain. If DEST is '$FW', then the rule is placed in the INPUT chain.
          Additionally, a <replaceable>chain-designator</replaceable> may not
          be specified in an action body.</para>

          <para>Where a command takes parameters, those parameters are
          enclosed in parentheses ("(....)") and separated by commas.</para>

          <para>The <replaceable>command</replaceable> may be one of the
          following.</para>

          <variablelist>
            <varlistentry>
              <term><emphasis
              role="bold"><replaceable>action</replaceable>[([<replaceable>param</replaceable>[,...])]</emphasis></term>

              <listitem>
                <para>Added in Shorewall 5.0.7.
                <replaceable>action</replaceable> must be an action declared
                with the <option>mangle</option> option in <ulink
                url="manpages/shorewall-actions.html">shorewall-actions(5)</ulink>.
                If the action accepts parameters, they are specified as a
                comma-separated list within parentheses following the
                <replaceable>action</replaceable> name.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">ADD(<replaceable>ipset</replaceable>:<replaceable>flags</replaceable>)</emphasis></term>

              <listitem>
                <para>Added in Shorewall 4.6.7. Causes addresses and/or port
                numbers to be added to the named
                <replaceable>ipset</replaceable>. The
                <replaceable>flags</replaceable> specify the address or tuple
                to be added to the set and must match the type of ipset
                involved. For example, for an iphash ipset, either the SOURCE
                or DESTINATION address can be added using
                <replaceable>flags</replaceable> <emphasis
                role="bold">src</emphasis> or <emphasis
                role="bold">dst</emphasis> respectively (see the -A command in
                ipset (8)).</para>

                <para>ADD is non-terminating. Even if a packet matches the
                rule, it is passed on to the next rule.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">CHECKSUM</emphasis></term>

              <listitem>
                <para>Compute and fill in the checksum in a packet that lacks
                a checksum. This is particularly useful if you need to work
                around old applications, such as dhcp clients, that do not
                work well with checksum offloads, but you don't want to
                disable checksum offload in your device.</para>

                <para>Requires 'Checksum Target' support in your kernel and
                iptables.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">CLASSIFY(<replaceable>classid</replaceable>)</emphasis></term>

              <listitem>
                <para>A classification Id (classid) is of the form
                <emphasis>major</emphasis>:<emphasis>minor</emphasis> where
                <emphasis>major</emphasis> and <emphasis>minor</emphasis> are
                integers. Corresponds to the 'class' specification in these
                traffic shaping modules:</para>

                <programlisting>       atm
       cbq
       dsmark
       pfifo_fast
       htb
       prio</programlisting>

                <para>Classification occurs in the POSTROUTING chain except
                when the <emphasis role="bold">SOURCE</emphasis> is <emphasis
                role="bold">$FW</emphasis>[:<emphasis>address</emphasis>] in
                which case classification occurs in the OUTPUT chain.</para>

                <para>When using Shorewall's built-in traffic shaping tool,
                the <emphasis>major</emphasis> class is the device number (the
                first device in <ulink
                url="shorewall-tcdevices.html">shorewall-tcdevices</ulink>(5)
                is major class 1, the second device is major class 2, and so
                on) and the <emphasis>minor</emphasis> class is the class's
                MARK value in <ulink
                url="shorewall-tcclasses.html">shorewall-tcclasses</ulink>(5)
                preceded by the number 1 (MARK 1 corresponds to minor class
                11, MARK 5 corresponds to minor class 15, MARK 22 corresponds
                to minor class 122, etc.).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">?COMMENT</emphasis></term>

              <listitem>
                <para>The rest of the line will be attached as a comment to
                the Netfilter rule(s) generated by the following entries. The
                comment will appear delimited by "/* ... */" in the output of
                <command>shorewall show mangle</command></para>

                <para>To stop the comment from being attached to further
                rules, simply include ?COMMENT on a line by itself.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">CONMARK({mark|range})</emphasis></term>

              <listitem>
                <para>Identical to MARK with the exception that the mark is
                assigned to connection to which the packet belongs is marked
                rather than to the packet itself.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">CONTINUE</emphasis></term>

              <listitem>
                <para>Don't process any more marking rules in the
                table.</para>

                <para>Currently, CONTINUE may not be used with
                <emphasis>exclusion</emphasis> (see the SOURCE and DEST
                columns below); that restriction will be removed when
                iptables/Netfilter provides the necessary support.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">DEL(<replaceable>ipset</replaceable>:<replaceable>flags</replaceable>)</emphasis></term>

              <listitem>
                <para>Added in Shorewall 4.6.7. Causes an entry to be deleted
                from the named <replaceable>ipset</replaceable>. The
                <replaceable>flags</replaceable> specify the address or tuple
                to be deleted from the set and must match the type of ipset
                involved. For example, for an iphash ipset, either the SOURCE
                or DESTINATION address can be deleted using
                <replaceable>flags</replaceable> <emphasis
                role="bold">src</emphasis> or <emphasis
                role="bold">dst</emphasis> respectively (see the -D command in
                ipset (8)).</para>

                <para>DEL is non-terminating. Even if a packet matches the
                rule, it is passed on to the next rule.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">DIVERT</emphasis></term>

              <listitem>
                <para>Two DIVERT rule should precede the TPROXY rule and
                should select DEST PORT tcp 80 and SOURCE PORT tcp 80
                respectively (assuming that tcp port 80 is being proxied).
                DIVERT avoids sending packets to the TPROXY target once a
                socket connection to Squid3 has been established by TPROXY.
                DIVERT marks the packet with a unique mark and exempts it from
                any rules that follow.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">DIVERTHA</emphasis></term>

              <listitem>
                <para>Added in Shorewall 5.0.4. To setup the HAProxy
                configuration described at <ulink
                url="http://www.loadbalancer.org/blog/setting-up-haproxy-with-transparent-mode-on-centos-6-x">http://www.loadbalancer.org/blog/setting-up-haproxy-with-transparent-mode-on-centos-6-x</ulink>,
                place this entry in <ulink
                url="shorewall-providers.html">shorewall-providers(5)</ulink>:</para>

                <programlisting>#NAME    NUMBER   MARK    DUPLICATE  INTERFACE GATEWAY         OPTIONS               COPY
TProxy   1        -       -          lo        -               tproxy</programlisting>

                <para>and use this DIVERTHA entry:</para>

                <programlisting>#ACTION         SOURCE          DEST            PROTO   DPORT   SPORT   USER    TEST    LENGTH  TOS   CONNBYTES         HELPER    PROBABILITY DSCP
DIVERTHA        -               -               tcp</programlisting>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">DROP</emphasis></term>

              <listitem>
                <para>Causes matching packets to be discarded.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">DSCP</emphasis>(<replaceable>dscp</replaceable>)</term>

              <listitem>
                <para>Sets the <firstterm>Differentiated Services Code
                Point</firstterm> field in the IP header. The
                <replaceable>dscp</replaceable> value may be given as an even
                number (hex or decimal) or as the name of a DSCP class. Valid
                class names and their associated hex numeric values
                are:</para>

                <programlisting>    CS0  =&gt; 0x00
    CS1  =&gt; 0x08
    CS2  =&gt; 0x10
    CS3  =&gt; 0x18
    CS4  =&gt; 0x20
    CS5  =&gt; 0x28
    CS6  =&gt; 0x30
    CS7  =&gt; 0x38
    BE   =&gt; 0x00
    AF11 =&gt; 0x0a
    AF12 =&gt; 0x0c
    AF13 =&gt; 0x0e
    AF21 =&gt; 0x12
    AF22 =&gt; 0x14
    AF23 =&gt; 0x16
    AF31 =&gt; 0x1a
    AF32 =&gt; 0x1c
    AF33 =&gt; 0x1e
    AF41 =&gt; 0x22
    AF42 =&gt; 0x24
    AF43 =&gt; 0x26
    EF   =&gt; 0x2e</programlisting>

                <para>To indicate more than one class, add their hex values
                together and specify the result. By default, DSCP rules are
                placed in the POSTROUTING chain.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">ECN</emphasis></term>

              <listitem>
                <para>Added in Shorewall 5.0.6 as an alternative to entries in
                <ulink
                url="shorewall-ecn.html">shorewall-ecn(5)</ulink>.
                If a PROTO is specified, it must be 'tcp' (6). If no PROTO is
                supplied, TCP is assumed. This action causes all ECN bits in
                the TCP header to be cleared.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">IMQ</emphasis>(<replaceable>number</replaceable>)</term>

              <listitem>
                <para>Specifies that the packet should be passed to the IMQ
                identified by <replaceable>number</replaceable>. Requires IMQ
                Target support in your kernel and iptables.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">INLINE</emphasis>[(<replaceable>action</replaceable>)]</term>

              <listitem>
                <para>Allows you to place your own ip[6]tables matches at the
                end of the line following a semicolon (";") (deprecated) or
                two semicolons (";;") (preferred since Shoreall 5.0.0). If an
                <replaceable>action</replaceable> is specified, the compiler
                proceeds as if that <replaceable>action</replaceable> had been
                specified in this column. If no action is specified, then you
                may include your own jump ("-j
                <replaceable>target</replaceable>
                [<replaceable>option</replaceable>] ...") after any matches
                specified at the end of the rule. If the target is not one
                known to Shorewall, then it must be defined as a builtin
                action in <ulink
                url="shorewall-actions.html">shorewall-actions</ulink>
                (5).</para>

                <para>The following rules are equivalent:</para>

                <programlisting>2:P                   eth0              -         tcp 22
INLINE(MARK(2)):P     eth0              -         tcp 22
INLINE(MARK(2)):P     eth0              -                 ;; -p tcp
INLINE                eth0              -         tcp 22  ;; -j MARK --set-mark 2
INLINE                eth0              -                 ;; -p tcp -j MARK --set-mark 2
</programlisting>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">IPMARK</emphasis></term>

              <listitem>
                <para>Assigns a mark to each matching packet based on the
                either the source or destination IP address. By default, it
                assigns a mark value equal to the low-order 8 bits of the
                source address. Default values are:</para>

                <simplelist>
                  <member>src</member>

                  <member><emphasis>mask1</emphasis> = 0xFF</member>

                  <member><emphasis>mask2</emphasis> = 0x00</member>

                  <member><emphasis>shift</emphasis> = 0</member>
                </simplelist>

                <para>'src' and 'dst' specify whether the mark is to be based
                on the source or destination address respectively. The
                selected address is first shifted to the right by
                <emphasis>shift</emphasis> bits. The result is then LANDed
                with <emphasis>mask1</emphasis> then LORed with
                <emphasis>ma<emphasis>s</emphasis>k2</emphasis>.</para>

                <para>In a sense, the IPMARK target is more like an IPCLASSIFY
                target in that the mark value is later interpreted as a class
                ID. A packet mark is 32 bits wide; so is a class ID. The
                &lt;major&gt; class occupies the high-order 16 bits and the
                &lt;minor&gt; class occupies the low-order 16 bits. So the
                class ID 1:4ff (remember that class IDs are always in hex) is
                equivalent to a mark value of 0x104ff. Remember that Shorewall
                uses the interface number as the &lt;major&gt; number where
                the first interface in tcdevices has &lt;major&gt; number 1,
                the second has &lt;major&gt; number 2, and so on.</para>

                <para>The IPMARK target assigns a mark to each matching packet
                based on the either the source or destination IP address. By
                default, it assigns a mark value equal to the low-order 8 bits
                of the source address. The syntax is as follows:</para>

                <blockquote>
                  <para><option>IPMARK</option>[([{<option>src</option>|<option>dst</option>}][,[<replaceable>mask1</replaceable>][,[<replaceable>mask2</replaceable>][,[<replaceable>shift</replaceable>]]]])]</para>
                </blockquote>

                <para>Default values are:</para>

                <simplelist>
                  <member><option>src</option></member>

                  <member><replaceable>mask1</replaceable> = 0xFF</member>

                  <member><replaceable>mask2</replaceable> = 0x00</member>

                  <member><replaceable>shift</replaceable> = 0</member>
                </simplelist>

                <para><option>src</option> and <option>dst</option> specify
                whether the mark is to be based on the source or destination
                address respectively. The selected address is first shifted
                right by <replaceable>shift</replaceable>, then LANDed with
                <replaceable>mask1</replaceable> and then LORed with
                <replaceable>mask2</replaceable>. The
                <replaceable>shift</replaceable> argument is intended to be
                used primarily with IPv6 addresses.</para>

                <para>Example:</para>

                <blockquote>
                  <para>IPMARK(src,0xff,0x10100)</para>

                  <simplelist>
                    <member>Suppose that the source IP address is 192.168.4.3
                    = 0xc0a80403; then</member>

                    <member>0xc0a80403 &gt;&gt; 0 = 0xc0a80403</member>

                    <member>0xc0a80403 LAND 0xFF = 0x03</member>

                    <member>0x03 LOR 0x10100 = 0x10103 or class ID
                    1:103</member>
                  </simplelist>
                </blockquote>

                <para>It is important to realize that, while class IDs are
                composed of a <replaceable>major</replaceable> and a
                <replaceable>minor</replaceable> value, the set of values must
                be unique. That is, the same numeric value cannot be used as
                both a <replaceable>major</replaceable> and a
                <replaceable>minor</replaceable> number for the same interface
                unless class nesting occurs (which is not currently possible
                with Shorewall). You should keep this in mind when deciding
                how to map IP addresses to class IDs.</para>

                <para>For example, suppose that your internal network is
                192.168.1.0/29 (host IP addresses 192.168.1.1 - 192.168.1.6).
                Your first notion might be to use IPMARK(src,0xFF,0x10000) so
                as to produce class IDs 1:1 through 1:6. But 1:1 is an invalid
                class ID since the <replaceable>major</replaceable> and
                <replaceable>minor</replaceable> classes are equal. So you
                might choose instead to use IPMARK(src,0xFF,0x10100) as in the
                example above so that all of your
                <replaceable>minor</replaceable> classes will have a value
                &gt; 256.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">IP6TABLES({<replaceable>target</replaceable>
              [<replaceable>option</replaceable> ...])</emphasis></term>

              <listitem>
                <para>IPv6 only.</para>

                <para>This action allows you to specify an iptables target
                with options (e.g., 'IP6TABLES(MARK --set-xmark 0x01/0xff)'.
                If the target is not one recognized by Shorewall, the
                following error message will be issued:</para>

                <simplelist>
                  <member>ERROR: Unknown target
                  (<replaceable>target</replaceable>)</member>
                </simplelist>

                <para>This error message may be eliminated by adding the
                <replaceable>target</replaceable> as a builtin action in
                <ulink
                url="shorewall-actions.html">shorewall-actions(5)</ulink>.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">IPTABLES({<replaceable>target</replaceable>
              [<replaceable>option</replaceable> ...])</emphasis></term>

              <listitem>
                <para>IPv4 only.</para>

                <para>This action allows you to specify an iptables target
                with options (e.g., 'IPTABLES(MARK --set-xmark 0x01/0xff)'. If
                the target is not one recognized by Shorewall, the following
                error message will be issued:</para>

                <simplelist>
                  <member>ERROR: Unknown target
                  (<replaceable>target</replaceable>)</member>
                </simplelist>

                <para>This error message may be eliminated by adding the
                <replaceable>target</replaceable> as a builtin action in
                <ulink
                url="shorewall-actions.html">shorewall-actions(5)</ulink>.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">MARK({<replaceable>mark</replaceable>|<replaceable>range</replaceable>})</emphasis></term>

              <listitem>
                <para>where <replaceable>mark</replaceable> is a packet mark
                value.</para>

                <para>Normally will set the mark value. If preceded by a
                vertical bar ("|"), the mark value will be logically ORed with
                the current mark value to produce a new mark value. If
                preceded by an ampersand ("&amp;"), will be logically ANDed
                with the current mark value to produce a new mark
                value.</para>

                <para>Both "|" and "&amp;" require Extended MARK Target
                support in your kernel and iptables.</para>

                <para>The mark value may be optionally followed by "/" and a
                mask value (used to determine those bits of the connection
                mark to actually be set). When a mask is specified, the result
                of logically ANDing the mark value with the mask must be the
                same as the mark value.</para>

                <para>A mark <replaceable>range</replaceable> is a pair of
                integers separated by a dash ("-").</para>

                <para>May be optionally followed by a slash ("/") and a mask
                and requires the <firstterm>Statistics Match</firstterm>
                capability in iptables and kernel. Marks in the specified
                range are assigned to packets on a round-robin fashion.</para>

                <para>When a mask is specified, the result of logically ANDing
                each mark value with the mask must be the same as the mark
                value. The least significant bit in the mask is used as an
                increment. For example, if '0x200-0x400/0xff00' is specified,
                then the assigned mark values are 0x200, 0x300 and 0x400 in
                equal proportions. If no mask is specified, then ( 2 **
                MASK_BITS ) - 1 is assumed (MASK_BITS is set in <ulink
                url="shorewall.conf.html">shorewall.conf</ulink>(5)).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">NFLOG</emphasis>[(<emphasis>nflog-parameters</emphasis>)]</term>

              <listitem>
                <para>Added in Shorewall 5.0.9. Logs matching packets using
                NFLOG. The <replaceable>nflog-parameters</replaceable> are a
                comma-separated list of up to 3 numbers:</para>

                <itemizedlist>
                  <listitem>
                    <para>The first number specifies the netlink group
                    (0-65535). If omitted (e.g., NFLOG(,0,10)) then a value of
                    0 is assumed.</para>
                  </listitem>

                  <listitem>
                    <para>The second number specifies the maximum number of
                    bytes to copy. If omitted, 0 (no limit) is assumed.</para>
                  </listitem>

                  <listitem>
                    <para>The third number specifies the number of log
                    messages that should be buffered in the kernel before they
                    are sent to user space. The default is 1.</para>
                  </listitem>
                </itemizedlist>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">RESTORE</emphasis>[(<emphasis>mask</emphasis>)]</term>

              <listitem>
                <para>Restore the packet's mark from the connection's mark
                using the supplied mask if any. Your kernel and iptables must
                include CONNMARK support.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">SAME[(<replaceable>timeout</replaceable>)]</emphasis></term>

              <listitem>
                <para>Some websites run applications that require multiple
                connections from a client browser. Where multiple 'balanced'
                providers are configured, this can lead to problems when some
                of the connections are routed through one provider and some
                through another. The SAME target allows you to work around
                that problem. SAME may be used in the PREROUTING and OUTPUT
                chains. When used in PREROUTING, it causes matching
                connections from an individual local system to all use the
                same provider. For example: <programlisting>#ACTION           SOURCE         DEST         PROTO      DPORT
SAME:P            192.168.1.0/24 0.0.0.0/0    tcp        80,443</programlisting>
                If a host in 192.168.1.0/24 attempts a connection on TCP port
                80 or 443 and it has sent a packet on either of those ports in
                the last five minutes then the new connection will use the
                same provider as the connection over which that last packet
                was sent.</para>

                <para>When used in the OUTPUT chain, it causes all matching
                connections to an individual remote system to all use the same
                provider. For example:<programlisting>#ACTION           SOURCE         DEST         PROTO      DPORT
SAME              $FW            0.0.0.0/0    tcp        80,443</programlisting>The
                optional <replaceable>timeout</replaceable> parameter was
                added in Shorewall 4.6.7 and specifies a number of seconds .
                When not specified, a value of 300 seconds (5 minutes) is
                assumed. If the firewall attempts a connection on TCP port 80
                or 443 and it has sent a packet on either of those ports in
                the last <replaceable>timeout</replaceable> seconds to the
                same remote system then the new connection will use the same
                provider as the connection over which that last packet was
                sent.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">SAVE[(<emphasis><replaceable>mask</replaceable>)</emphasis>]
              </emphasis></term>

              <listitem>
                <para>Save the packet's mark to the connection's mark using
                the supplied mask if any. Your kernel and iptables must
                include CONNMARK support.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">TCPMSS</emphasis>([<replaceable>mss</replaceable>[,<replaceable>ipsec</replaceable>]])</term>

              <listitem>
                <para>Added in Shorewall 5.1.9. This target only applies to
                TCP traffic and alters the MSS value in SYN packets. It may be
                used in the FORWARD and POSTROUTING chains; the default is
                FORWARD.</para>

                <para>The <replaceable>mss</replaceable> parameter may be
                either <option>pmtu</option> or an integer in the range
                500:65533. The value <option>pmtu</option> automatically
                clamps the MSS value to (path_MTU - 40 for IPv4; -60 for
                IPv6). This may not function as desired where asymmetric
                routes with differing path MTU exist — the kernel uses the
                path MTU which it would use to send packets from itself to the
                source and destination IP addresses. Prior to Linux 2.6.25,
                only the path MTU to the destination IP address was considered
                by this option; subsequent kernels also consider the path MTU
                to the source IP address. If an integer is given, the MSS
                option is set to the specified value. If the MSS of the packet
                is already lower than <replaceable>mss</replaceable>, it will
                not be increased (from Linux 2.6.25 onwards) to avoid more
                problems with hosts relying on a proper MSS. If
                <replaceable>mss</replaceable> is omitted,
                <option>pmtu</option> is assumed.</para>

                <para>The <replaceable>ipsec</replaceable> parameter
                determines whether the rule applies to IPSEC traffic
                (<option>ipsec</option> is passed), non-IPSEC traffic
                (<option>none</option> is passed) or both
                (<option>all</option> is passed). If omitted,
                <option>all</option> is assumed.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">TOS</emphasis>(<replaceable>tos</replaceable>[/<replaceable>mask</replaceable>])</term>

              <listitem>
                <para>Sets the <firstterm>Type of Service</firstterm> field in
                the IP header. The <replaceable>tos</replaceable> value may be
                given as an number (hex or decimal) or as the name of a TOS
                type. Valid type names and their associated hex numeric values
                are:</para>

                <programlisting>Minimize-Delay       =&gt; 0x10,
Maximize-Throughput  =&gt; 0x08,
Maximize-Reliability =&gt; 0x04,
Minimize-Cost        =&gt; 0x02,
Normal-Service       =&gt; 0x00</programlisting>

                <para>To indicate more than one class, add their hex values
                together and specify the result.</para>

                <para>When <replaceable>tos</replaceable> is given as a
                number, it may be optionally followed by '/' and a
                <replaceable>mask</replaceable>. When no
                <replaceable>mask</replaceable> is given, the value 0xff is
                assumed. When <replaceable>tos</replaceable> is given as a
                type name, the <replaceable>mask</replaceable> 0x3f is
                assumed.</para>

                <para>The action performed is to zero out the bits specified
                by the <replaceable>mask</replaceable>, then set the bits
                specified by <replaceable>tos</replaceable>.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">TPROXY</emphasis>([<replaceable>port</replaceable>[,<replaceable>address</replaceable>]])</term>

              <listitem>
                <para>Transparently redirects a packet without altering the IP
                header. Requires a tproxy provider to be defined in <ulink
                url="shorewall-providers.html">shorewall-providers</ulink>(5).</para>

                <para>There are three parameters to TPROXY - neither is
                required:</para>

                <itemizedlist>
                  <listitem>
                    <para><replaceable>port</replaceable> - the port on which
                    the proxy server is listening. If omitted, the original
                    destination port.</para>
                  </listitem>

                  <listitem>
                    <para><replaceable>address</replaceable> - a local (to the
                    firewall) IP address on which the proxy server is
                    listening. If omitted, the IP address of the interface on
                    which the request arrives.</para>
                  </listitem>
                </itemizedlist>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis role="bold">TTL</emphasis>([<emphasis
              role="bold">-</emphasis>|<emphasis
              role="bold">+</emphasis>]<replaceable>number</replaceable>)</term>

              <listitem>
                <para>If <emphasis role="bold">+</emphasis> is included,
                packets matching the rule will have their TTL incremented by
                <replaceable>number</replaceable>. Similarly, if <emphasis
                role="bold">-</emphasis> is included, matching packets have
                their TTL decremented by <replaceable>number</replaceable>. If
                neither <emphasis role="bold">+</emphasis> nor <emphasis
                role="bold">-</emphasis> is given, the TTL of matching packets
                is set to <replaceable>number</replaceable>. The valid range
                of values for <replaceable>number</replaceable> is
                1-255.</para>
              </listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SOURCE -
        {-|<replaceable>source-spec</replaceable>[,...]}</emphasis></term>

        <listitem>
          <para>where <replaceable>source-spec</replaceable> is one of:</para>

          <variablelist>
            <varlistentry>
              <term>[!]<replaceable>interface</replaceable></term>

              <listitem>
                <para>where <replaceable>interface</replaceable> is the
                logical name of an <replaceable>interface</replaceable>
                defined in <ulink
                url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5).
                Matches packets entering the firewall from the named
                interface. May not be used in CLASSIFY rules or in rules using
                the :T chain qualifier.</para>

                <para>Beginning with Shorweall 5.2.1, the
                <replaceable>interface</replaceable> may be preceded with '!'
                which matches all interfaces except the one specified.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>]</term>

              <listitem>
                <para>where <replaceable>address</replaceable> is:</para>

                <blockquote>
                  <para>A host or network IP address.</para>

                  <para>The name of an ipset preceded by a plus sign
                  ("+").</para>

                  <para>A MAC address in Shorewall format (preceded by a tilde
                  ("~") and using dash ("-") as a separator (e.g.,
                  ~00-A0-C9-15-39-78).</para>
                </blockquote>

                <para>Matches traffic whose source IP address matches one of
                the listed addresses and that does not match an address listed
                in the <replaceable>exclusion</replaceable> (see <ulink
                url="shorewall-exclusion.html">shorewall-exclusion</ulink>(5)).</para>

                <para><emphasis role="bold">This form will not match traffic
                that originates on the firewall itself unless either
                &lt;major&gt;&lt;minor&gt; or the :T chain qualifier is used
                in the ACTION column.</emphasis></para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>[!]<replaceable>interface</replaceable>:<replaceable>address</replaceable>,[...][<replaceable>exclusion</replaceable>]</term>

              <listitem>
                <para>This form combines the preceding two forms and matches
                when both the incoming interface and source IP address
                match.</para>

                <para>Beginning with Shorweall 5.2.1, the
                <replaceable>interface</replaceable> may be preceded with '!'
                which matches all interfaces except the one specified.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>[!]<replaceable>interface</replaceable>:<replaceable>exclusion</replaceable></term>

              <listitem>
                <para>This form matches packets arriving through the named
                <replaceable>interface</replaceable> and whose source IP
                address does not match any of the addresses in the
                <replaceable>exclusion</replaceable>.</para>

                <para>Beginning with Shorweall 5.2.1, the
                <replaceable>interface</replaceable> may be preceded with '!'
                which matches all interfaces except the one specified.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>$FW</term>

              <listitem>
                <para>Matches packets originating on the firewall system. May
                not be used with a chain qualifier (:P, :F, etc.) in the
                ACTION column.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>$FW:<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>]</term>

              <listitem>
                <para>where <replaceable>address</replaceable> is as above
                (MAC addresses are not permitted). Matches packets originating
                on the firewall and whose source IP address matches one of the
                listed addresses and does not match any address listed in the
                <replaceable>exclusion</replaceable>. May not be used with a
                chain qualifier (:P, :F, etc.) in the ACTION column.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>$FW:<replaceable>exclusion</replaceable></term>

              <listitem>
                <para>Matches traffic originating on the firewall, provided
                that the source IP address does not match any address listed
                in the <replaceable>exclusion</replaceable>.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>Beginning with Shorewall 5.1.0, multiple
          <replaceable>source_spec</replaceable>s, separated by commas, may be
          given provided that the following alternative forms are used:</para>

          <blockquote>
            <para>(<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>])</para>

            <para><replaceable>interface</replaceable>:(<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>])</para>

            <para><replaceable>interface</replaceable>:(<replaceable>exclusion</replaceable>)</para>

            <para>$FW:(<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>])</para>

            <para>$FW:(<replaceable>exclusion</replaceable>)</para>
          </blockquote>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DEST -
        {-|<replaceable>dest-spec</replaceable>[,...]}</emphasis></term>

        <listitem>
          <para>where <replaceable>dest-spec</replaceable> is one of:</para>

          <variablelist>
            <varlistentry>
              <term><replaceable>interface</replaceable></term>

              <listitem>
                <para>where <replaceable>interface</replaceable> is the
                logical name of an interface defined in <ulink
                url="shorewall-interfaces.html">shorewall-interfaces</ulink>(5).
                Matches packets leaving the firewall through the named
                interface. May not be used in the PREROUTING chain (:P in the
                mark column or no chain qualifier and MARK_IN_FORWARD_CHAIN=No
                in <ulink
                url="shorewall.conf">shorewall.conf</ulink>
                (5)).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>]</term>

              <listitem>
                <para>where <replaceable>address</replaceable> is:</para>

                <blockquote>
                  <para>A host or network IP address.</para>

                  <para>The name of an ipset preceded by a plus sign
                  ("+").</para>

                  <para>A MAC address in Shorewall format (preceded by a tilde
                  ("~") and using dash ("-") as a separator (e.g.,
                  ~00-A0-C9-15-39-78).</para>
                </blockquote>

                <para>Matches traffic whose destination IP address matches one
                of the listed addresses and that does not match an address
                listed in the <replaceable>exclusion</replaceable> (see <ulink
                url="shorewall-exclusion.html">shorewall-exclusion</ulink>(5)).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><replaceable>interface</replaceable>:<replaceable>address</replaceable>,[...][<replaceable>exclusion</replaceable>]</term>

              <listitem>
                <para>This form combines the preceding two forms and matches
                when both the outgoing interface and destination IP address
                match. May not be used in the PREROUTING chain (:P in the mark
                column or no chain qualifier and MARK_IN_FORWARD_CHAIN=No in
                <ulink url="shorewall.conf">shorewall.conf</ulink>
                (5)).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><replaceable>interface</replaceable>:<replaceable>exclusion</replaceable></term>

              <listitem>
                <para>This form matches packets leaving through the named
                <replaceable>interface</replaceable> and whose destination IP
                address does not match any of the addresses in the
                <replaceable>exclusion</replaceable>. May not be used in the
                PREROUTING chain (:P in the mark column or no chain qualifier
                and MARK_IN_FORWARD_CHAIN=No in <ulink
                url="shorewall.conf">shorewall.conf</ulink>
                (5)).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>$FW</term>

              <listitem>
                <para>Matches packets originating on the firewall system. May
                not be used with a chain qualifier (:P, :F, etc.) in the
                ACTION column.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>$FW:<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>]</term>

              <listitem>
                <para>where <replaceable>address</replaceable> is as above
                (MAC addresses are not permitted). Matches packets destined
                for the firewall and whose destination IP address matches one
                of the listed addresses and does not match any address listed
                in the <replaceable>exclusion</replaceable>. May not be used
                with a chain qualifier (:P, :F, etc.) in the ACTION
                column.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>$FW:<replaceable>exclusion</replaceable></term>

              <listitem>
                <para>Matches traffic destined for the firewall, provided that
                the destination IP address does not match any address listed
                in the <replaceable>exclusion</replaceable>.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>Beginning with Shorewall 5.1.0, multiple
          <replaceable>dest_spec</replaceable>s, separated by commas, may be
          given provided that the following alternative forms are used:</para>

          <blockquote>
            <para>(<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>])</para>

            <para><replaceable>interface</replaceable>:(<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>])</para>

            <para><replaceable>interface</replaceable>:(<replaceable>exclusion</replaceable>)</para>

            <para>$FW:(<replaceable>address</replaceable>[,...][<replaceable>exclusion</replaceable>])</para>

            <para>$FW:(<replaceable>exclusion</replaceable>)</para>
          </blockquote>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">PROTO</emphasis> - {<emphasis
        role="bold">-</emphasis>|<emphasis
        role="bold">{tcp:[!]syn</emphasis>|<emphasis
        role="bold">ipp2p</emphasis>|<emphasis
        role="bold">ipp2p:udp</emphasis>|<emphasis
        role="bold">ipp2p:all</emphasis>|<emphasis>protocol-number</emphasis>|<emphasis>protocol-name</emphasis>|<emphasis
        role="bold">all}[,...]}</emphasis></term>

        <listitem>
          <para>See <ulink
          url="shorewall-rules.html">shorewall-rules(5)</ulink> for
          details.</para>

          <para>Beginning with Shorewall 4.5.12, this column can accept a
          comma-separated list of protocols.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DPORT</emphasis>- {<emphasis
        role="bold">-</emphasis>|<emphasis>port-name-number-or-range</emphasis>[<emphasis
        role="bold">,</emphasis><emphasis>port-name-number-or-range</emphasis>]...|+<replaceable>ipset</replaceable>}</term>

        <listitem>
          <para>Optional destination Ports. A comma-separated list of Port
          names (from services(5)), <emphasis>port number</emphasis>s or
          <emphasis>port range</emphasis>s; if the protocol is <emphasis
          role="bold">icmp</emphasis>, this column is interpreted as the
          destination icmp-type(s). ICMP types may be specified as a numeric
          type, a numeric type and code separated by a slash (e.g., 3/4), or a
          typename. See <ulink
          url="../configuration_file_basics.htm#ICMP">https://shorewall.org/configuration_file_basics.htm#ICMP</ulink>.</para>

          <para>If the protocol is <emphasis role="bold">ipp2p</emphasis>,
          this column is interpreted as an ipp2p option without the leading
          "--" (example <emphasis role="bold">bit</emphasis> for bit-torrent).
          If no PORT is given, <emphasis role="bold">ipp2p</emphasis> is
          assumed.</para>

          <para>An entry in this field requires that the PROTO column specify
          icmp (1), tcp (6), udp (17), sctp (132) or udplite (136). Use '-' if
          any of the following field is supplied.</para>

          <para>Beginning with Shorewall 4.6.0, an
          <replaceable>ipset</replaceable> name can be specified in this
          column. This is intended to be used with
          <firstterm>bitmap:port</firstterm> ipsets.</para>

          <para>This column was formerly named DEST PORT(S).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SPORT</emphasis> - {<emphasis
        role="bold">-</emphasis>|<emphasis>port-name-number-or-range</emphasis>[<emphasis
        role="bold">,</emphasis><emphasis>port-name-number-or-range</emphasis>]...|+<replaceable>ipset</replaceable>}</term>

        <listitem>
          <para>Optional source port(s). If omitted, any source port is
          acceptable. Specified as a comma-separated list of port names, port
          numbers or port ranges.</para>

          <para>An entry in this field requires that the PROTO column specify
          tcp (6), udp (17), sctp (132) or udplite (136). Use '-' if any of
          the following fields is supplied.</para>

          <para>Beginning with Shorewall 4.5.15, you may place '=' in this
          column, provided that the DPORT column is non-empty. This causes the
          rule to match when either the source port or the destination port in
          a packet matches one of the ports specified in DEST PORTS(S). Use of
          '=' requires multi-port match in your iptables and kernel.</para>

          <para>Beginning with Shorewall 4.6.0, an
          <replaceable>ipset</replaceable> name can be specified in this
          column. This is intended to be used with
          <firstterm>bitmap:port</firstterm> ipsets.</para>

          <para>This column was formerly labelled SOURCE PORT(S).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">USER</emphasis> - [<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 optional column may only be non-empty if the SOURCE is
          the firewall itself.</para>

          <para>When this column is non-empty, the rule applies 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">TEST</emphasis> - [<emphasis
        role="bold">!</emphasis>]<emphasis>value</emphasis>[/<emphasis>mask</emphasis>][<emphasis
        role="bold">:C</emphasis>]</term>

        <listitem>
          <para>Optional - 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">LENGTH</emphasis> -
        [<emphasis>length</emphasis>|[<emphasis>min</emphasis>]<emphasis
        role="bold">:</emphasis>[<emphasis>max</emphasis>]]</term>

        <listitem>
          <para>Optional - packet payload length. This field, if present allow
          you to match the length of a packet payload (Layer 4 data ) against
          a specific value or range of values. You must have iptables length
          support for this to work. A range is specified in the form
          <emphasis>min</emphasis>:<emphasis>max</emphasis> where either
          <emphasis>min</emphasis> or <emphasis>max</emphasis> (but not both)
          may be omitted. If <emphasis>min</emphasis> is omitted, then 0 is
          assumed; if <emphasis>max</emphasis> is omitted, than any packet
          that is <emphasis>min</emphasis> or longer will match.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">TOS</emphasis> -
        <emphasis>tos</emphasis></term>

        <listitem>
          <para>Type of service. Either a standard name, or a numeric value to
          match.</para>

          <programlisting>         <emphasis role="bold">Minimize-Delay</emphasis> (16)
         <emphasis role="bold">Maximize-Throughput</emphasis> (8)
         <emphasis role="bold">Maximize-Reliability</emphasis> (4)
         <emphasis role="bold">Minimize-Cost</emphasis> (2)
         <emphasis role="bold">Normal-Service</emphasis> (0)</programlisting>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">CONNBYTES</emphasis> -
        [!]<emphasis>min</emphasis>:[<emphasis>max</emphasis>[:{<emphasis
        role="bold">O</emphasis>|<emphasis role="bold">R</emphasis>|<emphasis
        role="bold">B</emphasis>}[:{<emphasis
        role="bold">B</emphasis>|<emphasis role="bold">P</emphasis>|<emphasis
        role="bold">A</emphasis>}]]]</term>

        <listitem>
          <para>Optional connection Bytes; defines a byte or packet range that
          the connection must fall within in order for the rule to
          match.</para>

          <para>A packet matches if the the packet/byte count is within the
          range defined by <emphasis>min</emphasis> and
          <emphasis>max</emphasis> (unless ! is given in which case, a packet
          matches if the packet/byte count is not within the range).
          <emphasis>min</emphasis> is an integer which defines the beginning
          of the byte/packet range. <emphasis>max</emphasis> is an integer
          which defines the end of the byte/packet range; if omitted, only the
          beginning of the range is checked. The first letter gives the
          direction which the range refers to:<blockquote>
              <para><emphasis role="bold">O</emphasis> - The original
              direction of the connection.</para>

              <para>- The opposite direction from the original
              connection.</para>

              <para><emphasis role="bold">B</emphasis> - The total of both
              directions.</para>
            </blockquote></para>

          <para>If omitted, <emphasis role="bold">B</emphasis> is
          assumed.</para>

          <para>The second letter determines what the range refers
          to.<blockquote>
              <para><emphasis role="bold">B</emphasis> - Bytes</para>

              <para><emphasis role="bold">P</emphasis> - Packets</para>

              <para><emphasis role="bold">A</emphasis> - Average packet
              size.</para>
            </blockquote>If omitted, <emphasis role="bold">B</emphasis> is
          assumed.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">HELPER -
        </emphasis><emphasis>helper</emphasis></term>

        <listitem>
          <para>Names a Netfilter protocol <firstterm>helper</firstterm>
          module such as <option>ftp</option>, <option>sip</option>,
          <option>amanda</option>, etc. A packet will match if it was accepted
          by the named helper module.</para>

          <para>Example: Mark all FTP data connections with mark
          4:<programlisting>#ACTION   SOURCE    DEST      PROTO   DPORT      SPORT   USER TEST LENGTH TOS CONNBYTES HELPER
4:T       0.0.0.0/0 0.0.0.0/0 TCP     -          -       -    -    -      -   -         ftp</programlisting></para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">PROBABILITY</emphasis> -
        [<replaceable>probability</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.0. 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 &lt;
          <replaceable>probability</replaceable> &lt;= 1 and may be expressed
          at up to 8 decimal points of precision.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DSCP -</emphasis>
        [[!]<replaceable>dscp</replaceable>]</term>

        <listitem>
          <para>Added in Shorewall 4.5.1. When non-empty, match packets whose
          <firstterm>Differentiated Service Code Point</firstterm> field
          matches the supplied value (when '!' is given, the rule matches
          packets whose DSCP field does not match the supplied value). The
          <replaceable>dscp</replaceable> value may be given as an even number
          (hex or decimal) or as the name of a DSCP class. Valid class names
          and their associated hex numeric values are:</para>

          <programlisting>    CS0  =&gt; 0x00
    CS1  =&gt; 0x08
    CS2  =&gt; 0x10
    CS3  =&gt; 0x18
    CS4  =&gt; 0x20
    CS5  =&gt; 0x28
    CS6  =&gt; 0x30
    CS7  =&gt; 0x38
    BE   =&gt; 0x00
    AF11 =&gt; 0x0a
    AF12 =&gt; 0x0c
    AF13 =&gt; 0x0e
    AF21 =&gt; 0x12
    AF22 =&gt; 0x14
    AF23 =&gt; 0x16
    AF31 =&gt; 0x1a
    AF32 =&gt; 0x1c
    AF33 =&gt; 0x1e
    AF41 =&gt; 0x22
    AF42 =&gt; 0x24
    AF43 =&gt; 0x26
    EF   =&gt; 0x2e</programlisting>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">STATE</emphasis> -- {<emphasis
        role="bold">NEW</emphasis>|<emphasis
        role="bold">RELATED</emphasis>|<emphasis
        role="bold">ESTABLISHED</emphasis>|<emphasis
        role="bold">INVALID</emphasis>} [,...]</term>

        <listitem>
          <para>The rule will only match if the packet's connection is in one
          of the listed states.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">TIME</emphasis> -
        <emphasis>timeelement</emphasis>[&amp;<emphasis>timeelement</emphasis>...]</term>

        <listitem>
          <para>Added in Shorewall 4.6.2.</para>

          <para>May be used to limit the rule to a particular time period each
          day, to particular days of the week or month, or to a range defined
          by dates and times. Requires time match support in your kernel and
          ip6tables.</para>

          <para><replaceable>timeelement</replaceable> may be:</para>

          <variablelist>
            <varlistentry>
              <term>timestart=<replaceable>hh</replaceable>:<replaceable>mm</replaceable>[:<replaceable>ss</replaceable>]</term>

              <listitem>
                <para>Defines the starting time of day.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>timestop=<replaceable>hh</replaceable>:<replaceable>mm</replaceable>[:<replaceable>ss</replaceable>]</term>

              <listitem>
                <para>Defines the ending time of day.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>contiguous</term>

              <listitem>
                <para>Added in Shoreawll 5.0.12. When <emphasis
                role="bold">timestop</emphasis> is smaller than <emphasis
                role="bold">timestart</emphasis> value, match this as a single
                time period instead of distinct intervals.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>utc</term>

              <listitem>
                <para>Times are expressed in Greenwich Mean Time.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>localtz</term>

              <listitem>
                <para>Deprecated by the Netfilter team in favor of <emphasis
                role="bold">kerneltz</emphasis>. Times are expressed in Local
                Civil Time (default).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>kerneltz</term>

              <listitem>
                <para>Added in Shorewall 4.5.2. Times are expressed in Local
                Kernel Time (requires iptables 1.4.12 or later).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>weekdays=ddd[,ddd]...</term>

              <listitem>
                <para>where <replaceable>ddd</replaceable> is one of
                <option>Mon</option>, <option>Tue</option>,
                <option>Wed</option>, <option>Thu</option>,
                <option>Fri</option>, <option>Sat</option> or
                <option>Sun</option></para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>monthdays=dd[,dd],...</term>

              <listitem>
                <para>where <replaceable>dd</replaceable> is an ordinal day of
                the month</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>datestart=<replaceable>yyyy</replaceable>[-<replaceable>mm</replaceable>[-<replaceable>dd</replaceable>[<option>T</option><replaceable>hh</replaceable>[:<replaceable>mm</replaceable>[:<replaceable>ss</replaceable>]]]]]</term>

              <listitem>
                <para>Defines the starting date and time.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>datestop=<replaceable>yyyy</replaceable>[-<replaceable>mm</replaceable>[-<replaceable>dd</replaceable>[<option>T</option><replaceable>hh</replaceable>[:<replaceable>mm</replaceable>[:<replaceable>ss</replaceable>]]]]]</term>

              <listitem>
                <para>Defines the ending date and time.</para>
              </listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SWITCH -
        [!]<replaceable>switch-name</replaceable>[={0|1}]</emphasis></term>

        <listitem>
          <para>Added in Shorewall 5.1.0 and allows enabling and disabling the
          rule without requiring <command>shorewall reload</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 &gt;
            /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 &gt;
            /proc/net/nf_condition/<replaceable>switch-name</replaceable></command></member>
          </simplelist>

          <para>Switch settings are retained over <command>shorewall
          reload</command>.</para>

          <para>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>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Example</title>

    <variablelist>
      <varlistentry>
        <term>IPv4 Example 1:</term>

        <listitem>
          <para>Mark all ICMP echo traffic with packet mark 1. Mark all peer
          to peer traffic with packet mark 4.</para>

          <para>This is a little more complex than otherwise expected. Since
          the ipp2p module is unable to determine all packets in a connection
          are P2P packets, we mark the entire connection as P2P if any of the
          packets are determined to match.</para>

          <para>We assume packet/connection mark 0 means unclassified.</para>

          <programlisting>       #ACTION    SOURCE    DEST         PROTO   DPORT         SPORT   USER    TEST
       MARK(1):T  0.0.0.0/0 0.0.0.0/0    icmp    echo-request
       MARK(1):T  0.0.0.0/0 0.0.0.0/0    icmp    echo-reply
       RESTORE:T  0.0.0.0/0 0.0.0.0/0    all     -             -       -       0
       CONTINUE:T 0.0.0.0/0 0.0.0.0/0    all     -             -       -       !0
       MARK(4):T  0.0.0.0/0 0.0.0.0/0   ipp2p:all
       SAVE:T     0.0.0.0/0 0.0.0.0/0   all     -             -       -       !0</programlisting>

          <para>If a packet hasn't been classified (packet mark is 0), copy
          the connection mark to the packet mark. If the packet mark is set,
          we're done. If the packet is P2P, set the packet mark to 4. If the
          packet mark has been set, save it to the connection mark.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>IPv4 Example 2:</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/mangle:

       #ACTION            SOURCE         DEST         PROTO   DPORT         SPORT   USER    TEST
       CONNMARK(1-3):F    192.168.1.0/24 eth0 ; state=NEW

/etc/shorewall/snat:

       #ACTION          SOURCE              DEST     ...
       SNAT(1.1.1.1)    eth0:192.168.1.0/24 - { mark=1:C }
       SNAT(1.1.1.3)    eth0:192.168.1.0/24 - { mark=2:C }
       SNAT(1.1.1.4)    eth0:192.168.1.0/24 - { mark=3:C }</programlisting>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>IPv6 Example 1:</term>

        <listitem>
          <para>Mark all ICMP echo traffic with packet mark 1. Mark all peer
          to peer traffic with packet mark 4.</para>

          <para>This is a little more complex than otherwise expected. Since
          the ipp2p module is unable to determine all packets in a connection
          are P2P packets, we mark the entire connection as P2P if any of the
          packets are determined to match.</para>

          <para>We assume packet/connection mark 0 means unclassified.</para>

          <programlisting>       #ACTION    SOURCE    DEST         PROTO   DPORT         SPORT   USER    TEST
       MARK(1):T  ::/0      ::/0         icmp    echo-request
       MARK(1):T  ::/0      ::/0         icmp    echo-reply
       RESTORE:T  ::/0      ::/0         all     -             -       -       0
       CONTINUE:T ::/0      ::/0         all     -             -       -       !0
       MARK(4):T  ::/0      ::/0         ipp2p:all
       SAVE:T     ::/0      ::/0         all     -             -       -       !0</programlisting>

          <para>If a packet hasn't been classified (packet mark is 0), copy
          the connection mark to the packet mark. If the packet mark is set,
          we're done. If the packet is P2P, set the packet mark to 4. If the
          packet mark has been set, save it to the connection mark.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>FILES</title>

    <para>/etc/shorewall/mangle</para>

    <para>/etc/shorewall6/mangle</para>
  </refsect1>

  <refsect1>
    <title>See ALSO</title>

    <para><ulink
    url="../traffic_shaping.htm">https://shorewall.org/traffic_shaping.htm</ulink></para>

    <para><ulink
    url="../MultiISP.html">https://shorewall.org/MultiISP.html</ulink></para>

    <para><ulink
    url="../PacketMarking.html">https://shorewall.org/PacketMarking.html</ulink></para>

    <para><ulink
    url="../configuration_file_basics.htm#Pairs">https://shorewall.org/configuration_file_basics.htm#Pairs</ulink></para>

    <para>shorewall(8)</para>
  </refsect1>
</refentry>