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238 lines
11 KiB
XML
238 lines
11 KiB
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/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>2004-04-19</pubdate>
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<copyright>
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<year>2003-2004</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 License</ulink></quote>.</para>
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</legalnotice>
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</articleinfo>
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<para>Shorewall Traffic Accounting support was added in Shorewall release
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1.4.7.</para>
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<para>Shorewall accounting rules are described in the file
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/etc/shorewall/accounting. By default, the accounting rules are placed in a
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chain called <quote>accounting</quote> and can thus be displayed using
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<quote>shorewall show accounting</quote>. All traffic passing into, out of
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or through the firewall traverses the accounting chain including traffic
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that will later be rejected by interface options such as <quote>tcpflags</quote>
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and <quote>maclist</quote>. If your kernel doesn't support the
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connection tracking match extension (Kernel 2.4.21) then some traffic
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rejected under <quote>norfc1918</quote> will not traverse the accounting
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chain.</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 match
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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 the
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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 to
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jump to. Shorewall will create the chain automatically. If the name
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of the chain is followed by <quote>:COUNT</quote> then a COUNT rule
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matching this rule will automatically be added to <chain>.
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Chain names must start with a letter, must be composed of letters
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and digits, and may contain underscores (<quote>_</quote>) and
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periods (<quote>.</quote>). Beginning with Shorewall version 1.4.8,
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chain names man also contain embedded dashes (<quote>-</quote>) and
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are not required to start with a letter.</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.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">SOURCE</emphasis> - Packet Source. The name
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of an interface, an address (host or net) or an interface name followed
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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 Destination
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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 (from
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<filename>/etc/protocols</filename>) or a protocol number.</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).</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">SOURCE PORT</emphasis>- Source Port number.
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Service name from /etc/services or port number. May only be specified if
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the protocol is TCP or UDP (6 or 17).</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>,<quote>any</quote>
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and <quote>all</quote> are treated as wild-cards.</para>
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<para>The accounting rules are evaluated in the Netfilter <quote>filter</quote>
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table. This is the same environment where the <quote>rules</quote> file
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rules are evaluated and in this environment, DNAT has already occurred in
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inbound packets and SNAT has not yet occurred on outbound ones.</para>
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<para>Accounting rules are not stateful -- each rule only handles traffic in
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one direction. For example, if eth0 is your internet interface and you have
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a web server in your DMZ connected to eth1 then to count HTTP traffic in
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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 <quote>shorewall show web</quote> will give you a breakdown of
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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 <quote>shorewall show web</quote> simply gives you a breakdown by
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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
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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 role="bold">SERVER</emphasis>.
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If you want to account for web browsing, you have to reverse the rules
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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 url="http://www.nightbrawler.com/code/shorewall-stats/">http://www.nightbrawler.com/code/shorewall-stats/</ulink>.</para>
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</article>
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