shorewall_code/Shorewall-docs2/traffic_shaping.xml

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  <articleinfo>
    <title>Traffic Shaping/Control</title>

    <authorgroup>
      <author>
        <firstname>Tom</firstname>

        <surname>Eastep</surname>
      </author>
    </authorgroup>

    <pubdate>2004-02-11</pubdate>

    <copyright>
      <year>2001-2004</year>

      <holder>Thomas M. Eastep</holder>
    </copyright>

    <legalnotice>
      <para>Permission is granted to copy, distribute and/or modify this
      document under the terms of the GNU Free Documentation License, Version
      1.2 or any later version published by the Free Software Foundation; with
      no Invariant Sections, with no Front-Cover, and with no Back-Cover
      Texts. A copy of the license is included in the section entitled
      <quote><ulink url="GnuCopyright.htm">GNU Free Documentation License</ulink></quote>.</para>
    </legalnotice>
  </articleinfo>

  <section>
    <title>Introduction</title>

    <para>Shorewall has limited support for traffic shaping/control. In order
    to use traffic shaping under Shorewall, it is essential that you get a
    copy of the <ulink url="http://ds9a.nl/lartc">Linux Advanced Routing and
    Shaping HOWTO</ulink>, version 0.3.0 or later. It is also necessary to be
    running Linux Kernel 2.4.18 or later. Shorewall traffic shaping support
    consists of the following:</para>

    <itemizedlist>
      <listitem>
        <para>A new <emphasis role="bold">TC_ENABLED</emphasis> parameter in
        /etc/shorewall.conf.</para>
      </listitem>

      <listitem>
        <para>A new <emphasis role="bold">CLEAR_TC</emphasis> parameter in
        /etc/shorewall.conf (Added in Shorewall 1.3.13). When Traffic Shaping
        is enabled (TC_ENABLED=Yes), the setting of this variable determines
        whether Shorewall clears the traffic shaping configuration during
        Shorewall [re]start and Shorewall stop.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">/etc/shorewall/tcrules</emphasis> - A file
        where you can specify firewall marking of packets. The firewall mark
        value may be used to classify packets for traffic shaping/control.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">/etc/shorewall/tcstart </emphasis>- A
        user-supplied file that is sourced by Shorewall during <quote>shorewall
        start</quote> and which you can use to define your traffic shaping
        disciplines and classes. I have provided a <ulink
        url="ftp://ftp.shorewall.net/pub/shorewall/cbq">sample</ulink> that
        does table-driven CBQ shaping but if you read the traffic shaping
        sections of the HOWTO mentioned above, you can probably code your own
        faster than you can learn how to use my sample. I personally use
        <ulink url="http://luxik.cdi.cz/%7Edevik/qos/htb/">HTB</ulink> (see
        below). HTB support may eventually become an integral part of
        Shorewall since HTB is a lot simpler and better-documented than CBQ.
        As of 2.4.20, HTB is a standard part of the kernel but iproute2 must
        be patched in order to use it.</para>

        <para>In tcstart, when you want to run the <quote>tc</quote> utility,
        use the run_tc function supplied by shorewall if you want tc errors to
        stop the firewall.</para>

        <para>You can generally use off-the-shelf traffic shaping scripts by
        simply copying them to /etc/shorewall/tcstart. I use <ulink
        url="http://lartc.org/wondershaper/">The Wonder Shaper </ulink>(HTB
        version) that way (i.e., I just copied wshaper.htb to
        /etc/shorewall/tcstart and modified it according to the Wonder Shaper
        README). <emphasis role="bold">WARNING</emphasis>: If you use use
        Masquerading or SNAT (i.e., you only have one external IP address)
        then listing internal hosts in the NOPRIOHOSTSRC variable in the
        wshaper[.htb] script won&#39;t work. Traffic shaping occurs after SNAT
        has already been applied so when traffic shaping happens, all outbound
        traffic will have as a source address the IP addresss of your
        firewall&#39;s external interface.</para>
      </listitem>

      <listitem>
        <para><emphasis role="bold">/etc/shorewall/tcclear</emphasis> - A
        user-supplied file that is sourced by Shorewall when it is clearing
        traffic shaping. This file is normally not required as Shorewall&#39;s
        method of clearing qdisc and filter definitions is pretty general.</para>
      </listitem>
    </itemizedlist>

    <para>Shorewall allows you to start traffic shaping when Shorewall itself
    starts or it allows you to bring up traffic shaping when you bring up your
    interfaces.</para>

    <para>To start traffic shaping when Shorewall starts:</para>

    <orderedlist>
      <listitem>
        <para>Set TC_ENABLED=Yes and CLEAR_TC=Yes</para>
      </listitem>

      <listitem>
        <para>Supply an /etc/shorewall/tcstart script to configure your
        traffic shaping rules.</para>
      </listitem>

      <listitem>
        <para>Optionally supply an /etc/shorewall/tcclear script to stop
        traffic shaping. That is usually unnecessary.</para>
      </listitem>

      <listitem>
        <para>If your tcstart script uses the <quote>fwmark</quote>
        classifier, you can mark packets using entries in
        /etc/shorewall/tcrules.</para>
      </listitem>
    </orderedlist>

    <para>To start traffic shaping when you bring up your network interfaces,
    you will have to arrange for your traffic shaping configuration script to
    be run at that time. How you do that is distribution dependent and will
    not be covered here. You then should:</para>

    <orderedlist>
      <listitem>
        <para>Set TC_ENABLED=Yes and CLEAR_TC=No</para>
      </listitem>

      <listitem>
        <para>Do not supply /etc/shorewall/tcstart or /etc/shorewall/tcclear
        scripts.</para>
      </listitem>

      <listitem>
        <para>If your tcstart script uses the <quote>fwmark</quote>
        classifier, you can mark packets using entries in
        /etc/shorewall/tcrules.</para>
      </listitem>
    </orderedlist>
  </section>

  <section>
    <title>Kernel Configuration</title>

    <para>This screen shot show how I&#39;ve configured QoS in my Kernel:<graphic
    align="center" fileref="images/QoS.png" /></para>
  </section>

  <section>
    <title>/etc/shorewall/tcrules</title>

    <para>The fwmark classifier provides a convenient way to classify packets
    for traffic shaping. The /etc/shorewall/tcrules file provides a means for
    specifying these marks in a tabular fashion.</para>

    <para>Normally, packet marking occurs in the PREROUTING chain before any
    address rewriting takes place. This makes it impossible to mark inbound
    packets based on their destination address when SNAT or Masquerading are
    being used. Beginning with Shorewall 1.3.12, you can cause packet marking
    to occur in the FORWARD chain by using the MARK_IN_FORWARD_CHAIN option in
    shorewall.conf.</para>

    <para>Columns in the file are as follows:</para>

    <itemizedlist>
      <listitem>
        <para>MARK - Specifies the mark value is to be assigned in case of a
        match. This is an integer in the range 1-255. Beginning with Shorewall
        version 1.3.14, this value may be optionally followed by
        <quote>:</quote> and either <quote>F</quote> or <quote>P</quote> to
        designate that the marking will occur in the FORWARD or PREROUTING
        chains respectively. If this additional specification is omitted, the
        chain used to mark packets will be determined by the setting of the
        MARK_IN_FORWARD_CHAIN option in shorewall.conf.</para>
      </listitem>

      <listitem>
        <para>SOURCE - The source of the packet. If the packet originates on
        the firewall, place <quote>fw</quote> in this column. Otherwise, this
        is a comma-separated list of interface names, IP addresses, MAC
        addresses in Shorewall Format and/or Subnets.</para>

        <para>Examples <programlisting>    eth0
    192.168.2.4,192.168.1.0/24</programlisting></para>
      </listitem>

      <listitem>
        <para>DEST -- Destination of the packet. Comma-separated list of IP
        addresses and/or subnets.</para>
      </listitem>

      <listitem>
        <para>PROTO - Protocol - Must be the name of a protocol from
        /etc/protocol, a number or <quote>all</quote></para>
      </listitem>

      <listitem>
        <para>PORT(S) - Destination Ports. A comma-separated list of Port
        names (from /etc/services), port numbers or port ranges (e.g., 21:22);
        if the protocol is <quote>icmp</quote>, this column is interpreted as
        the destination icmp type(s).</para>
      </listitem>

      <listitem>
        <para>CLIENT PORT(S) - (Optional) Port(s) used by the client. If
        omitted, any source port is acceptable. Specified as a comma-separate
        list of port names, port numbers or port ranges.</para>
      </listitem>

      <listitem>
        <para>USER (Added in Shorewall version 1.4.10) - (Optional) This
        column may only be non-empty if the SOURCE is the firewall itself.
        When this column is non-empty, the rule applies only if the program
        generating the output is running under the effective user and/or
        group. It may contain :</para>

        <para>[&#60;user name or number&#62;]:[&#60;group name or number&#62;]</para>

        <para>The colon is optionnal when specifying only a user.</para>

        <para>Examples : john: / john / :users / john:users</para>
      </listitem>
    </itemizedlist>

    <example>
      <title></title>

      <para>All packets arriving on eth1 should be marked with 1. All packets
      arriving on eth2 and eth3 should be marked with 2. All packets
      originating on the firewall itself should be marked with 3.</para>

      <programlisting>#MARK   SOURCE    DESTINATION    PROTOCOL   USER/GROUP
1       eth1      0.0.0.0/0      all
2       eth2      0.0.0.0/0      all
2       eth3      0.0.0.0/0      all
3       fw        0.0.0.0/0      all</programlisting>
    </example>

    <example>
      <title></title>

      <para>All GRE (protocol 47) packets not originating on the firewall and
      destined for 155.186.235.151 should be marked with 12.</para>

      <programlisting>#MARK   SOURCE    DESTINATION     PROTOCOL   USER/GROUP
12      0.0.0.0/0 155.182.235.151 47</programlisting>
    </example>

    <example>
      <title></title>

      <para>All SSH packets originating in 192.168.1.0/24 and destined for
      155.186.235.151 should be marked with 22.</para>

      <programlisting>#MARK   SOURCE         DESTINATION     PROTOCOL   USER/GROUP
22      192.168.1.0/24 155.182.235.151 tcp        22</programlisting>
    </example>
  </section>

  <section>
    <title>My Current Setup</title>

    <para>I am currently using the HTB version of <ulink
    url="http://lartc.org/wondershaper/">The Wonder Shaper </ulink>(I just
    copied wshaper.htb to /etc/shorewall/tcstart and modified it as shown in
    the Wondershaper README). WonderShaper DOES NOT USE THE
    /etc/shorewall/tcrules file.</para>
  </section>

  <section>
    <title>My Old Setup</title>

    <para>I have also run with the following set of hand-crafted rules in my
    <emphasis role="bold">/etc/shorewall/tcstart</emphasis> file.</para>

    <blockquote>
      <programlisting>run_tc qdisc add dev eth0 root handle 1: htb default 30

run_tc class add dev eth0 parent 1: classid 1:1 htb rate 384kbit burst 15k
echo <quote>   Added Top Level Class -- rate 384kbit</quote>

run_tc class add dev eth0 parent 1:1 classid 1:10 htb rate 140kbit ceil 384kbit burst 15k prio 1
run_tc class add dev eth0 parent 1:1 classid 1:20 htb rate 224kbit ceil 384kbit burst 15k prio 0
run_tc class add dev eth0 parent 1:1 classid 1:30 htb rate 20kbit  ceil 384kbit burst 15k quantum 1500 prio 1
echo <quote>   Added Second Level Classes -- rates 140kbit, 224kbit, 20kbit</quote>

run_tc qdisc add dev eth0 parent 1:10 pfifo limit 5run_tc qdisc add dev eth0 parent 1:20 pfifo limit 10
run_tc qdisc add dev eth0 parent 1:30 pfifo limit 5
echo <quote>   Enabled PFIFO on Second Level Classes</quote>

run_tc filter add dev eth0 protocol ip parent 1:0 prio 1 handle 1 fw classid 1:10
run_tc filter add dev eth0 protocol ip parent 1:0 prio 0 handle 2 fw classid 1:20
run_tc filter add dev eth0 protocol ip parent 1:0 prio 1 handle 3 fw classid 1:30
echo <quote>   Defined fwmark filters</quote>
</programlisting>
    </blockquote>

    <para>My tcrules file that went with this tcstart file is shown in Example
    1 above. When I was using these rules:</para>

    <orderedlist>
      <listitem>
        <para>I wanted to allow up to 140kbits/second for traffic outbound
        from my DMZ (eth1 -- note that the ceiling is set to 384kbit so
        outbound DMZ traffic can use all available bandwidth if there is no
        traffic from the local systems or from my laptop or firewall).</para>
      </listitem>

      <listitem>
        <para>My laptop (which at that time connected via eth3) and local
        systems (eth2) could use up to 224kbits/second.</para>
      </listitem>

      <listitem>
        <para>My firewall could use up to 20kbits/second.</para>
      </listitem>
    </orderedlist>

    <para>Once www.shorewall.net was moved off-site, I no longer needed these
    shaping rules and The Wonder Shaper does all that I now require.</para>
  </section>
</article>