shorewall_code/manpages/shorewall-tcrules.xml

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

    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>tcrules</refname>

    <refpurpose>Shorewall Packet Marking rules file</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>/etc/shorewall/tcrules</command>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <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="http://shorewall.net/MultiISP.html">http://shorewall.net/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">MARK/CLASSIFY</emphasis> (mark) -
        <replaceable>mark</replaceable></term>

        <listitem>
          <para>Where <replaceable>mark</replaceable> may assume one of the
          following values.</para>

          <orderedlist numeration="arabic">
            <listitem>
              <para>A mark <emphasis>value</emphasis> which is an integer in
              the range 1-255.</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; neither may be used with connection
              marks (see below).</para>

              <para>May optionally be followed by <emphasis
              role="bold">:P</emphasis>, <emphasis
              role="bold">:F</emphasis>,<emphasis role="bold">:T</emphasis> or
              <emphasis role="bold">:I</emphasis> where<emphasis role="bold">
              :P</emphasis> indicates that marking should occur in the
              PREROUTING chain, <emphasis role="bold">:F</emphasis> indicates
              that marking should occur in the FORWARD chain, <emphasis
              role="bold">:I </emphasis>indicates that marking should occur in
              the INPUT chain (added in Shorewall 4.4.13), and <emphasis
              role="bold">:T</emphasis> indicates that marking should occur in
              the POSTROUTING chain. If neither <emphasis
              role="bold">:P</emphasis>, <emphasis role="bold">:F</emphasis>
              nor <emphasis role="bold">:T</emphasis> follow the mark value
              then the chain is determined as follows:</para>

              <para>- If the SOURCE is <emphasis
              role="bold">$FW</emphasis>[<emphasis
              role="bold">:</emphasis><emphasis>address-or-range</emphasis>[,<emphasis>address-or-range</emphasis>]...],
              then the rule is inserted into the OUTPUT chain. When
              HIGH_ROUTE_MARKS=Yes, only high mark values may be assigned
              there. Packet marking rules for traffic shaping of packets
              originating on the firewall must be coded in the POSTROUTING
              chain (see below).</para>

              <para>- Otherwise, the chain is determined by the setting of
              MARK_IN_FORWARD_CHAIN in <ulink
              url="shorewall.conf.html">shorewall.conf</ulink>(5).</para>

              <para>Please note that <emphasis role="bold">:I</emphasis> is
              included for completeness and affects neither traffic shaping
              nor policy routing.</para>

              <para>If your kernel and iptables include CONNMARK support then
              you can also mark the connection rather than the packet.</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). The mark and optional mask are then
              followed by one of:</para>

              <variablelist>
                <varlistentry>
                  <term><emphasis role="bold">C</emphasis></term>

                  <listitem>
                    <para>Mark the connection in the chain determined by the
                    setting of MARK_IN_FORWARD_CHAIN</para>
                  </listitem>
                </varlistentry>

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

                  <listitem>
                    <para>Mark the connection in the FORWARD chain</para>
                  </listitem>
                </varlistentry>

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

                  <listitem>
                    <para>Mark the connection in the PREROUTING chain.</para>
                  </listitem>
                </varlistentry>

                <varlistentry>
                  <term>CT</term>

                  <listitem>
                    <para>Mark the connecdtion in the POSTROUTING chain</para>
                  </listitem>
                </varlistentry>

                <varlistentry>
                  <term>CI</term>

                  <listitem>
                    <para>Mark the connection in the INPUT chain. This option
                    is included for completeness and has no applicability to
                    traffic shaping or policy routing.</para>
                  </listitem>
                </varlistentry>
              </variablelist>

              <para><emphasis role="bold">Special considerations for If
              HIGH_ROUTE_MARKS=Yes in <ulink
              url="shorewall.conf.html">shorewall.conf</ulink>(5</emphasis>).</para>

              <para>If HIGH_ROUTE_MARKS=Yes, then you may also specify a value
              in the range 0x0100-0xFF00 with the low-order byte being zero.
              Such values may only be used in the PREROUTING chain (value
              followed by <emphasis role="bold">:P</emphasis> or you have set
              MARK_IN_FORWARD_CHAIN=No in <ulink
              url="shorewall.conf.html">shorewall.conf</ulink>(5) and have not
              followed the value with <option>:F</option>) or the OUTPUT chain
              (SOURCE is <emphasis role="bold">$FW</emphasis>). With
              HIGH_ROUTE_MARKS=Yes, non-zero mark values less that 256 are not
              permitted. Shorewall prohibits non-zero mark values less that
              256 in the OUTPUT chain when HIGH_ROUTE_MARKS=Yes. While earlier
              versions allow such values in the OUTPUT chain, it is strongly
              recommended that with HIGH_ROUTE_MARKS=Yes, you use the
              POSTROUTING chain to apply traffic shaping
              marks/classification.</para>
            </listitem>

            <listitem>
              <para>A classification Id (classid) 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>

              <para>Beginning with Shorewall 4.4.27, the classid may be
              optionally followed by ':' and a capital letter designating the
              chain where classification is to occur.</para>

              <variablelist>
                <varlistentry>
                  <term>F</term>

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

                <varlistentry>
                  <term>T</term>

                  <listitem>
                    <para>POSTROUTING chain (default).</para>
                  </listitem>
                </varlistentry>
              </variablelist>
            </listitem>

            <listitem>
              <para><emphasis
              role="bold">RESTORE</emphasis>[/<emphasis>mask</emphasis>] --
              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>

              <para>As in 1) above, may be followed by <emphasis
              role="bold">:P</emphasis> or <emphasis
              role="bold">:F</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis
              role="bold">SAVE</emphasis>[/<emphasis>mask</emphasis>] -- 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>

              <para>As in 1) above, may be followed by <emphasis
              role="bold">:P</emphasis> or <emphasis
              role="bold">:F</emphasis></para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">CONTINUE</emphasis> Don't process
              any more marking rules ‒in the table.</para>

              <para>As in 1) above, may be followed by <emphasis
              role="bold">:P</emphasis> or <emphasis
              role="bold">:F</emphasis>. 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>

            <listitem>
              <para><emphasis role="bold">SAME</emphasis> 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>#MARK/            SOURCE         DEST         PROTO      DEST
#CLASSIFY                                                PORT(S)
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>#MARK/            SOURCE         DEST         PROTO      DEST
#CLASSIFY                                                PORT(S)
SAME              $FW            0.0.0.0/0    tcp        80,443</programlisting>
              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 five
              minutes 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>

            <listitem>
              <para><emphasis role="bold">COMMENT</emphasis> -- 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>

            <listitem>
              <para><emphasis role="bold">IPMARK</emphasis> ‒ 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 0x0x10100 = 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
              chose instent 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>

            <listitem>
              <para><emphasis
              role="bold">TPROXY</emphasis>(<replaceable>mark</replaceable>[/<replaceable>mask</replaceable>][,[<replaceable>port</replaceable>][,[<replaceable>address</replaceable>]]])</para>

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

              <para>There are three parameters to TPROXY - only the first
              (mark) is required:</para>

              <itemizedlist>
                <listitem>
                  <para><replaceable>mark</replaceable> - the MARK value
                  corresponding to the local provider in <ulink
                  url="shorewall-providers.html">shorewall-providers</ulink>(5).</para>
                </listitem>

                <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>

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

              <para>Added in Shorewall 4.4.24. May be option followed by
              <emphasis role="bold">:F</emphasis> but the resulting rule is
              always added to the FORWARD chain. 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>
          </orderedlist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SOURCE</emphasis> - {<emphasis
        role="bold">-</emphasis>|{<emphasis>interface</emphasis>|<emphasis
        role="bold">$FW</emphasis>}|[{<emphasis>interface</emphasis>|<emphasis
        role="bold">$FW</emphasis>}:]<emphasis>address-or-range</emphasis>[<emphasis
        role="bold">,</emphasis><emphasis>address-or-range</emphasis>]...}[<emphasis>exclusion</emphasis>]</term>

        <listitem>
          <para>May be:</para>

          <orderedlist>
            <listitem>
              <para>An interface name - matches traffic entering the firewall
              on the specified interface. May not be used in classify rules or
              in rules using the :T chain qualifier.</para>
            </listitem>

            <listitem>
              <para>A comma-separated list of host or network IP addresses or
              MAC addresses. <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 MARK column.</emphasis></para>

              <para>Examples:<simplelist>
                  <member>0.0.0.0/0</member>
                </simplelist></para>

              <para><simplelist>
                  <member>192.168.1.0/24, 172.20.4.0/24</member>
                </simplelist></para>
            </listitem>

            <listitem>
              <para>An interface name followed by a colon (":") followed by a
              comma-separated list of host or network IP addresses or MAC
              addresses. May not be used in classify rules or in rules using
              the :T chain qualifier.</para>
            </listitem>

            <listitem>
              <para>$FW optionally followed by a colon (":") and a
              comma-separated list of host or network IP addresses. Matches
              packets originating on the firewall. May not be used with a
              chain qualifier (:P, :F, etc.) in the MARK column.</para>
            </listitem>
          </orderedlist>

          <para>MAC addresses must be prefixed with "~" and use "-" as a
          separator.</para>

          <para>Example: ~00-A0-C9-15-39-78</para>

          <para>You may exclude certain hosts from the set already defined
          through use of an <emphasis>exclusion</emphasis> (see <ulink
          url="shorewall-exclusion.html">shorewall-exclusion</ulink>(5)).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">DEST</emphasis> - {<emphasis
        role="bold">-</emphasis>|{<emphasis>interface</emphasis>|$FW}|[<emphasis>{interface</emphasis>|$FW}:]<emphasis>address-or-range</emphasis>[<emphasis
        role="bold">,</emphasis><emphasis>address-or-range</emphasis>]...}[<emphasis>exclusion</emphasis>]</term>

        <listitem>
          <para>May be:</para>

          <orderedlist>
            <listitem>
              <para>An interface name. 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="manpages/shorewall.conf">shorewall.conf</ulink> (5)). The
              interface name may be optionally followed by a colon (":") and
              an IP address list.</para>
            </listitem>

            <listitem>
              <para>A comma-separated list of host or network IP addresses.
              The list may include ip address ranges if your kernel and
              iptables include iprange support.</para>
            </listitem>

            <listitem>
              <para>Beginning with Shorewall 4.4.13, $FW may be specified by
              itself or qualified by an address list. This causes marking to
              occur in the INPUT chain.</para>
            </listitem>
          </orderedlist>

          <para>You may exclude certain hosts from the set already defined
          through use of an <emphasis>exclusion</emphasis> (see <ulink
          url="shorewall-exclusion.html">shorewall-exclusion</ulink>(5)).</para>
        </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>Protocol - <emphasis role="bold">ipp2p</emphasis> requires
          ipp2p match support in your kernel and iptables.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">PORT(S)</emphasis> (dport) - [<emphasis
        role="bold">-</emphasis>|<emphasis>port-name-number-or-range</emphasis>[<emphasis
        role="bold">,</emphasis><emphasis>port-name-number-or-range</emphasis>]...]</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 numberic type and code separated by a slash (e.g., 3/4), or
          a typename. See <ulink
          url="http://www.shorewall.net/configuration_file_basics.htm#ICMP">http://www.shorewall.net/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>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">SOURCE PORT(S)</emphasis> (sport) -
        [<emphasis
        role="bold">-</emphasis>|<emphasis>port-name-number-or-range</emphasis>[<emphasis
        role="bold">,</emphasis><emphasis>port-name-number-or-range</emphasis>]...]</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>
        </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 Length. This field, if present allow you to
          match the length of a packet 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 Netfiler 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. You can also append "-" and a port
          number to the helper module name (e.g., <emphasis
          role="bold">ftp-21</emphasis>) to specify the port number that the
          original connection was made on.</para>

          <para>Example: Mark all FTP data connections with mark
          4:<programlisting>#MARK/    SOURCE    DEST      PROTO   PORT(S)    SOURCE  USER TEST LENGTH TOS CONNBYTES HELPER
#CLASSIFY                                        PORT(S)
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> -
        [probability]</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>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Example</title>

    <variablelist>
      <varlistentry>
        <term>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>       #MARK/     SOURCE    DEST         PROTO   PORT(S)       SOURCE  USER    TEST
       #CLASSIFY                                               PORT(S)
       1:T        0.0.0.0/0 0.0.0.0/0    icmp    echo-request
       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
       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 classifed (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/tcrules</para>
  </refsect1>

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

    <para><ulink
    url="http://shorewall.net/traffic_shaping.htm">http://shorewall.net/traffic_shaping.htm</ulink></para>

    <para><ulink
    url="http://shorewall.net/MultiISP.html">http://shorewall.net/MultiISP.html</ulink></para>

    <para><ulink
    url="http://shorewall.net/PacketMarking.html">http://shorewall.net/PacketMarking.html</ulink></para>

    <para><ulink
    url="http://shorewall.net/configuration_file_basics.htm#Pairs">http://shorewall.net/configuration_file_basics.htm#Pairs</ulink></para>

    <para>shorewall(8), shorewall-accounting(5), shorewall-actions(5),
    shorewall-blacklist(5), shorewall-ecn(5), shorewall-exclusion(5),
    shorewall-hosts(5), shorewall_interfaces(5), shorewall-ipsets(5),
    shorewall-maclist(5), shorewall-masq(5), shorewall-nat(5),
    shorewall-netmap(5), shorewall-params(5), shorewall-policy(5),
    shorewall-providers(5), shorewall-proxyarp(5), shorewall-rtrules(5),
    shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5),
    shorewall-secmarks(5), shorewall-tcclasses(5), shorewall-tcdevices(5),
    shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)</para>
  </refsect1>
</refentry>