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379 lines
17 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
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<article>
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<!--$Id$-->
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<articleinfo>
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<title>Shorewall Traffic Accounting</title>
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<authorgroup>
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<author>
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<firstname>Tom</firstname>
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<surname>Eastep</surname>
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</author>
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</authorgroup>
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<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
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<copyright>
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<year>2003-2009</year>
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<holder>Thomas M. Eastep</holder>
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</copyright>
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<legalnotice>
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<para>Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version
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1.2 or any later version published by the Free Software Foundation; with
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no Invariant Sections, with no Front-Cover, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled
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<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
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License</ulink></quote>.</para>
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</legalnotice>
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</articleinfo>
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<caution>
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<para><emphasis role="bold">This article applies to Shorewall 4.0 and
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later. If you are running a version of Shorewall earlier than Shorewall
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4.0.0 then please see the documentation for that
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release</emphasis>.</para>
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</caution>
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<section id="Basics">
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<title>Accounting Basics</title>
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<para>Shorewall accounting rules are described in the file
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<filename><filename>/etc/shorewall/accounting</filename></filename>. By
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default, the accounting rules are placed in a chain called
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<quote>accounting</quote> and can thus be displayed using
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<quote>shorewall[-lite] show -x accounting</quote>. All traffic passing
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into, out of, or through the firewall traverses the accounting chain
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including traffic that will later be rejected by interface options such as
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<quote>tcpflags</quote> and <quote>maclist</quote>.</para>
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<para>The columns in the accounting file are as follows:</para>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">ACTION </emphasis>- What to do when a
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match is found. Possible values are:</para>
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<itemizedlist>
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<listitem>
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<para>COUNT- Simply count the match and continue trying to match
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the packet with the following accounting rules</para>
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</listitem>
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<listitem>
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<para>DONE- Count the match and don't attempt to match any
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following accounting rules.</para>
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</listitem>
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<listitem>
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<para><emphasis><chain></emphasis> - The name of a chain;
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Shorewall will create the chain automatically if it doesn't
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already exist. A jump to this chain will be generated from the
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chain specified by the CHAIN column. If the name of the chain is
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followed by <quote>:COUNT</quote> then a COUNT rule matching this
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entry will automatically be added to <chain>. Chain names
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must start with a letter, must be composed of letters and digits,
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and may contain underscores (<quote>_</quote>) and periods
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(<quote>.</quote>). Beginning with Shorewall version 1.4.8, chain
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names may also contain embedded dashes (<quote>-</quote>) and are
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not required to start with a letter.</para>
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</listitem>
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<listitem>
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<para>COMMENT - (Shorewall-perl only) - The remainder of the line
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is treated as a comment which is <ulink
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url="configuration_file_basics.htm#COMMENT">attached to subsequent
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rules</ulink> until another COMMENT line is found or until the end
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of the file is reached. To stop adding comments to rules, use a
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line with only the word COMMENT.</para>
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</listitem>
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</itemizedlist>
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</listitem>
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<listitem>
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<para><emphasis role="bold">CHAIN</emphasis> - The name of the chain
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where the accounting rule is to be added. If empty or <quote>-</quote>
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then the <quote>accounting</quote> chain is assumed (see <link
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linkend="Bridge">below</link> for exceptions).</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">SOURCE</emphasis> - Packet Source. The
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name of an interface, an address (host or net), or an interface name
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followed by <quote>:</quote> and a host or net address.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">DESTINATION</emphasis> - Packet
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Destination. Format the same as the SOURCE column.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">PROTOCOL</emphasis> - A protocol name
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(from <filename>/etc/protocols</filename>), a protocol number or
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<quote>ipp2p</quote>. For <quote>ipp2p</quote>, your kernel and
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iptables must have ipp2p match support from <ulink
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url="http://www.netfilter.org">Netfilter
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Patch_o_matic_ng</ulink>.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">DEST PORT</emphasis> - Destination Port
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number. Service name from <filename>/etc/services</filename> or port
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number. May only be specified if the protocol is TCP or UDP (6 or 17).
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If the PROTOCOL is <quote>ipp2p</quote>, then this column is
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interpreted as an ipp2p option without the leading <quote>--</quote>
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(default <quote>ipp2p</quote>). For a list of value ipp2p options, as
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root type <command>iptables -m ipp2p --help</command>.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">SOURCE PORT</emphasis>- Source Port
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number. Service name from /etc/services or port number. May only be
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specified if the protocol is TCP or UDP (6 or 17).</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">USER/GROUP</emphasis> - This column may
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only be non-empty if the CHAIN is OUTPUT. The column may
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contain:</para>
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<programlisting>[!][<user name or number>][:<group name or number>][+<program name>]</programlisting>
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<para>When this column is non-empty, the rule applies only if the
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program generating the output is running under the effective
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<user> and/or <group> specified (or is NOT running under
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that id if <quote>!</quote> is given).</para>
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<para>Examples:</para>
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<simplelist>
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<member>joe #program must be run by joe</member>
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<member>:kids #program must be run by a member of the
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<quote>kids</quote> group.</member>
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<member>!:kids #program must not be run by a member of the
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<quote>kids</quote> group</member>
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<member>+upnpd #program named upnpd (This feature was removed from
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Netfilter in kernel version 2.6.14).</member>
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</simplelist>
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</listitem>
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<listitem>
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<para><emphasis role="bold">MARK</emphasis> - Only count packets with
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particular mark values. <programlisting>[!]<value>[/<mask>][:C]</programlisting>
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Defines a test on the existing packet or connection mark. The rule
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will match only if the test returns true.</para>
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<para>If you don’t want to define a test but need to specify anything
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in the following columns, place a <quote>-</quote> in this
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field.<simplelist>
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<member>! — Inverts the test (not equal)</member>
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<member><value> — Value of the packet or connection
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mark.</member>
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<member><mask> — A mask to be applied to the mark before
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testing.</member>
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<member>:C — Designates a connection mark. If omitted, the packet
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mark’s value is tested. This option is only supported by
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Shorewall-perl.</member>
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</simplelist></para>
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</listitem>
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</itemizedlist>
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<para>In all columns except ACTION and CHAIN, the values <quote>-</quote>,
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<quote>any</quote> and <quote>all</quote> are treated as
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wild-cards.</para>
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<para>The accounting rules are evaluated in the Netfilter
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<quote>filter</quote> table. This is the same environment where the
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<quote>rules</quote> file rules are evaluated and in this environment,
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DNAT has already occurred in inbound packets and SNAT has not yet occurred
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on outbound packets.</para>
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<para>Accounting rules are not stateful -- each rule only handles traffic
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in one direction. For example, if eth0 is your Internet interface, and you
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have a web server in your DMZ connected to eth1, then to count HTTP
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traffic in both directions requires two rules:</para>
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<programlisting> #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
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# PORT PORT
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DONE - eth0 eth1 tcp 80
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DONE - eth1 eth0 tcp - 80</programlisting>
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<para>Associating a counter with a chain allows for nice reporting. For
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example:</para>
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<programlisting> #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
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# PORT PORT
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web:COUNT - eth0 eth1 tcp 80
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web:COUNT - eth1 eth0 tcp - 80
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web:COUNT - eth0 eth1 tcp 443
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web:COUNT - eth1 eth0 tcp - 443
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DONE web</programlisting>
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<para>Now <command>shorewall show web</command> (or
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<command>shorewall-lite show web</command> for Shorewall Lite users) will
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give you a breakdown of your web traffic:</para>
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<programlisting> [root@gateway shorewall]# shorewall show web
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Shorewall-1.4.6-20030821 Chain web at gateway.shorewall.net - Wed Aug 20 09:48:56 PDT 2003
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Counters reset Wed Aug 20 09:48:00 PDT 2003
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Chain web (4 references)
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pkts bytes target prot opt in out source destination
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11 1335 tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
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18 1962 tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:80
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0 0 tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
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0 0 tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:443
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29 3297 RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
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[root@gateway shorewall]#</programlisting>
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<para>Here is a slightly different example:</para>
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<programlisting> #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
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# PORT PORT
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web - eth0 eth1 tcp 80
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web - eth1 eth0 tcp - 80
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web - eth0 eth1 tcp 443
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web - eth1 eth0 tcp - 443
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COUNT web eth0 eth1
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COUNT web eth1 eth0</programlisting>
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<para>Now <command>shorewall show web</command> (or
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<command>shorewall-lite show web</command> for Shorewall Lite users)
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simply gives you a breakdown by input and output:</para>
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<programlisting> [root@gateway shorewall]# shorewall show accounting web
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Shorewall-1.4.6-20030821 Chains accounting web at gateway.shorewall.net - Wed Aug 20 10:27:21 PDT 2003
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Counters reset Wed Aug 20 10:24:33 PDT 2003
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Chain accounting (3 references)
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pkts bytes target prot opt in out source destination
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8767 727K web tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
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0 0 web tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:443</programlisting>
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<programlisting>
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11506 13M web tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:80
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0 0 web tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:443
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Chain web (4 references)
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pkts bytes target prot opt in out source destination
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8767 727K all -- eth0 eth1 0.0.0.0/0 0.0.0.0/0
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11506 13M all -- eth1 eth0 0.0.0.0/0 0.0.0.0/0
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[root@gateway shorewall]#</programlisting>
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<para>Here's how the same example would be constructed on an HTTP server
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with only one interface (eth0).</para>
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<caution>
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<para>READ THE ABOVE CAREFULLY -- IT SAYS <emphasis
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role="bold">SERVER</emphasis>. If you want to account for web browsing,
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you have to reverse the rules below.</para>
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</caution>
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<programlisting> #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
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# PORT PORT
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web - eth0 - tcp 80
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web - - eth0 tcp - 80
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web - eth0 - tcp 443
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web - - eth0 tcp - 443
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COUNT web eth0
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COUNT web - eth0</programlisting>
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<para>Note that with only one interface, only the SOURCE (for input rules)
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or the DESTINATION (for output rules) is specified in each rule.</para>
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<para>Here's the output:</para>
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<programlisting> [root@mail shorewall]# shorewall show accounting web Shorewall-1.4.7
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Chains accounting web at mail.shorewall.net - Sun Oct 12 10:27:21 PDT 2003
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Counters reset Sat Oct 11 08:12:57 PDT 2003
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Chain accounting (3 references)
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pkts bytes target prot opt in out source destination
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8767 727K web tcp -- eth0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
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11506 13M web tcp -- * eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:80
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0 0 web tcp -- eth0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
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0 0 web tcp -- * eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:443
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Chain web (4 references)
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pkts bytes target prot opt in out source destination
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8767 727K all -- eth0 * 0.0.0.0/0 0.0.0.0/0
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11506 13M all -- * eth0 0.0.0.0/0 0.0.0.0/0
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[root@mail shorewall]#</programlisting>
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<para>For an example of integrating Shorewall Accounting with MRTG, see
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<ulink
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url="http://www.nightbrawler.com/code/shorewall-stats/">http://www.nightbrawler.com/code/shorewall-stats/</ulink>.</para>
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</section>
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<section id="Bridge">
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<title>Accounting with Bridges</title>
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<para>The structure of the accounting rules changes slightly when there
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are <ulink url="bridge-Shorewall-perl.html">bridges</ulink> defined in the
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Shorewall configuration. Because of the restrictions imposed by Netfilter
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in kernel 2.6.21 and later, output accounting rules must be segregated
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from forwarding and input rules. To accomplish this separation,
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Shorewall-perl creates two accounting chains:</para>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">accounting</emphasis> - for input and
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forwarded traffic.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">accountout</emphasis> - for output
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traffic.</para>
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</listitem>
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</itemizedlist>
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<para>If the CHAIN column contains <quote>-</quote>, then:</para>
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<itemizedlist>
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<listitem>
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<para>If the SOURCE column in a rule includes the name of the firewall
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zone (e.g., $FW), then the default chain to insert the rule into is
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<emphasis role="bold">accountout</emphasis> only.</para>
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</listitem>
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<listitem>
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<para>Otherwise, if the DEST in the rule is <emphasis
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role="bold">any</emphasis> or <emphasis role="bold">all</emphasis> or
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0.0.0.0/0, then the rule is added to both <emphasis
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role="bold">accounting</emphasis> and <emphasis
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role="bold">accountout</emphasis>.</para>
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</listitem>
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<listitem>
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<para>Otherwise, the rule is added to <emphasis
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role="bold">accounting</emphasis> only.</para>
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</listitem>
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</itemizedlist>
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</section>
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|
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<section id="Collectd">
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<title>Integrating Shorewall Accounting with Collectd</title>
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|
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<para>Sergiusz Pawlowicz has written a nice article that shows how to
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integrate Shorewall Accounting with collectd to produce nice graphs of
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traffic activity. The article may be found at <ulink
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url="http://collectd.org/wiki/index.php/Plugin:IPTables">http://collectd.org/wiki/index.php/Plugin:IPTables</ulink>.</para>
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</section>
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</article>
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