148 lines
6.3 KiB
Python
148 lines
6.3 KiB
Python
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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- Copyright (C) 2000-2018 Internet Systems Consortium, Inc. ("ISC")
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<html lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Chapter 5. The BIND 9 Lightweight Resolver</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
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<link rel="home" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
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<link rel="up" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
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<link rel="prev" href="Bv9ARM.ch04.html" title="Chapter 4. Advanced DNS Features">
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<link rel="next" href="Bv9ARM.ch06.html" title="Chapter 6. BIND 9 Configuration Reference">
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<div class="navheader">
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<table width="100%" summary="Navigation header">
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<tr><th colspan="3" align="center">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</th></tr>
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<tr>
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<td width="20%" align="left">
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<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a> </td>
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<th width="60%" align="center"> </th>
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<td width="20%" align="right"> <a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
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</td>
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</tr>
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</table>
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<hr>
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</div>
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<div class="chapter">
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<div class="titlepage"><div><div><h1 class="title">
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<a name="Bv9ARM.ch05"></a>Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</h1></div></div></div>
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<div class="toc">
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<p><b>Table of Contents</b></p>
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<dl class="toc">
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<dt><span class="section"><a href="Bv9ARM.ch05.html#lightweight_resolver">The Lightweight Resolver Library</a></span></dt>
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<dt><span class="section"><a href="Bv9ARM.ch05.html#lwresd">Running a Resolver Daemon</a></span></dt>
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</dl>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="lightweight_resolver"></a>The Lightweight Resolver Library</h2></div></div></div>
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<p>
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Traditionally applications have been linked with a stub resolver
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library that sends recursive DNS queries to a local caching name
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server.
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</p>
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<p>
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IPv6 once introduced new complexity into the resolution process,
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such as following A6 chains and DNAME records, and simultaneous
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lookup of IPv4 and IPv6 addresses. Though most of the complexity was
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then removed, these are hard or impossible
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to implement in a traditional stub resolver.
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</p>
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<p>
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<acronym class="acronym">BIND</acronym> 9 therefore can also provide resolution
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services to local clients
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using a combination of a lightweight resolver library and a resolver
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daemon process running on the local host. These communicate using
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a simple UDP-based protocol, the "lightweight resolver protocol"
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that is distinct from and simpler than the full DNS protocol.
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</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="lwresd"></a>Running a Resolver Daemon</h2></div></div></div>
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<p>
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To use the lightweight resolver interface, the system must
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run the resolver daemon <span class="command"><strong>lwresd</strong></span> or a
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local
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name server configured with a <span class="command"><strong>lwres</strong></span>
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statement.
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</p>
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<p>
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By default, applications using the lightweight resolver library will
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make
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UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
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The
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address can be overridden by <span class="command"><strong>lwserver</strong></span>
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lines in
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<code class="filename">/etc/resolv.conf</code>.
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</p>
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<p>
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The daemon currently only looks in the DNS, but in the future
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it may use other sources such as <code class="filename">/etc/hosts</code>,
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NIS, etc.
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</p>
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<p>
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The <span class="command"><strong>lwresd</strong></span> daemon is essentially a
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caching-only name server that responds to requests using the
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lightweight
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resolver protocol rather than the DNS protocol. Because it needs
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to run on each host, it is designed to require no or minimal
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configuration.
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Unless configured otherwise, it uses the name servers listed on
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<span class="command"><strong>nameserver</strong></span> lines in <code class="filename">/etc/resolv.conf</code>
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as forwarders, but is also capable of doing the resolution
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autonomously if
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none are specified.
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</p>
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<p>
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The <span class="command"><strong>lwresd</strong></span> daemon may also be
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configured with a
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<code class="filename">named.conf</code> style configuration file,
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in
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<code class="filename">/etc/lwresd.conf</code> by default. A name
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server may also
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be configured to act as a lightweight resolver daemon using the
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<span class="command"><strong>lwres</strong></span> statement in <code class="filename">named.conf</code>.
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</p>
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<p>
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The number of client queries that the <span class="command"><strong>lwresd</strong></span>
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daemon is able to serve can be set using the
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<code class="option">lwres-tasks</code> and <code class="option">lwres-clients</code>
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statements in the configuration.
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</p>
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</div>
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</div>
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<div class="navfooter">
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<hr>
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left">
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<a accesskey="p" href="Bv9ARM.ch04.html">Prev</a> </td>
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<td width="20%" align="center"> </td>
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<td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch06.html">Next</a>
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</td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Chapter 4. Advanced DNS Features </td>
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<td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
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<td width="40%" align="right" valign="top"> Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</td>
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</tr>
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</table>
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</div>
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<p xmlns:db="http://docbook.org/ns/docbook" style="text-align: center;">BIND 9.11.3 (Extended Support Version)</p>
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</body>
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</html>
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