155 lines
4.8 KiB
XML
155 lines
4.8 KiB
XML
<!-- WSDG Chapter Works -->
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<!-- $Id$ -->
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<chapter id="ChapterWorks">
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<title>How Wireshark Works</title>
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<section id="ChWorksIntro">
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<title>Introduction</title>
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<para>
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This chapter will give you a short overview, how Wireshark is working.
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</para>
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</section>
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<section id="ChWorksOverview">
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<title>Overview</title>
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<para>
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The following will give you a simplified overview of Wiresharks function blocks:
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<figure id="ChWorksFigOverview">
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<title>
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<application>Wireshark</application> function blocks.
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</title>
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<graphic entityref="WiresharkFunctionBlocks" format="PNG"/>
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</figure>
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</para>
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<para>
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The function blocks in more detail:
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<variablelist>
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<varlistentry><term><command>GTK 1/2</command></term>
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<listitem>
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<para>
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Handling of all user input/output (all windows, dialogs and such).
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Source code can be found in the <filename>gtk</filename> directory.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry><term><command>Core</command></term>
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<listitem>
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<para>
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Main "glue code" that holds the other blocks together, source
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code can be found in the root directory.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry><term><command>Epan</command></term>
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<listitem>
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<para>
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Ethereal Packet ANalyzer (XXX - is this correct?) the packet
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analyzing engine, source code can be found in the
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<filename>epan</filename> directory.
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</para>
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<itemizedlist>
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<listitem>
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<para>
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Protocol-Tree - Keep data of the capture file protocol information.
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</para>
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</listitem>
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<listitem>
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<para>
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Dissectors - The various protocol dissectors in
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<filename>epan/dissectors</filename>.
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</para>
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</listitem>
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<listitem>
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<para>
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Plugins - Some of the protocol dissectors are implemented as plugins, source
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code at <filename>plugins</filename>.
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</para>
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</listitem>
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<listitem>
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<para>
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Display-Filters - the display filter engine at
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<filename>epan/dfilter</filename>.
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</para>
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</listitem>
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</itemizedlist>
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</listitem>
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</varlistentry>
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<varlistentry><term><command>Capture</command></term>
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<listitem>
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<para>
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Capture engine.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry><term><command>Wiretap</command></term>
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<listitem>
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<para>
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The wiretap library is used to read/write capture files in libpcap
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and a lot of other file formats, the source code is in the
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<filename>wiretap</filename> directory.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>Win-/libpcap (not part of the Wireshark package)</command></term>
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<listitem>
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<para>
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The platform dependant packet capture library, including the capture
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filter engine. That's the reason why we still have different display
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and capture filter syntax, as two different filtering engines used.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</section>
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<section id="ChWorksCapturePackets">
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<title>Capturing packets</title>
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<para>
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Capturing will take packets from a network adapter, and save them to a file
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on your harddisk.
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</para>
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<para>
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To hide all the lowlevel machine dependant details from
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Wireshark, the libpcap/WinPcap (see <xref linkend="ChLibsPcap"/>) library
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is used. This library provides a general purpose interface to capture
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packets from a lot of different network interface types (Ethernet,
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Token Ring, ...).
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</para>
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</section>
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<section id="ChWorksCaptureFiles">
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<title>Capture Files</title>
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<para>
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Wireshark can read and write capture files in it's natural file format, the
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libpcap format, which is used by many other network capturing tools,
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e.g. tcpdump. In addition to this, as one of it's strengths,
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Wireshark can read/write files in many different file formats of other
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network capturing tools. The wiretap library, developed together with
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Wireshark, provides a general purpose interface to read/write all the file
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formats. If you need to add another capture file format, this is the place
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to start.
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</para>
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</section>
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<section id="ChWorksDissectPackets">
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<title>Dissect packets</title>
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<para>
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While Wireshark is loading packets from a file, each packet is dissected.
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Wireshark tries to detect what kind of packet it is and getting as much
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information from it as possible. In this run, only the information showed
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in the packet list pane is needed though.
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</para>
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<para>
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As the user selects a specific packet in the packet list pane, this packet
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will be dissected again. This time, Wireshark tries to
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get every single piece of information and put it into
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the packet details pane then.
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</para>
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</section>
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</chapter>
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<!-- End of WSDG Chapter Works -->
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