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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<title>Appendix D. BIND 9 DNS Library Support</title>
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<tr><th colspan="3" align="center">Appendix D. BIND 9 DNS Library Support</th></tr>
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<div class="appendix">
<div class="titlepage"><div><div><h1 class="title">
<a name="Bv9ARM.ch12"></a>BIND 9 DNS Library Support</h1></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<dl class="toc">
<dt><span class="section"><a href="Bv9ARM.ch12.html#bind9.library">BIND 9 DNS Library Support</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="Bv9ARM.ch12.html#id-1.13.2.5">Installation</a></span></dt>
<dt><span class="section"><a href="Bv9ARM.ch12.html#id-1.13.2.6">Known Defects/Restrictions</a></span></dt>
<dt><span class="section"><a href="Bv9ARM.ch12.html#id-1.13.2.7">The dns.conf File</a></span></dt>
<dt><span class="section"><a href="Bv9ARM.ch12.html#id-1.13.2.8">Sample Applications</a></span></dt>
<dt><span class="section"><a href="Bv9ARM.ch12.html#id-1.13.2.9">Library References</a></span></dt>
</dl></dd>
</dl>
</div>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="bind9.library"></a>BIND 9 DNS Library Support</h2></div></div></div>
<p>
This version of BIND 9 "exports" its internal libraries so
that they can be used by third-party applications more easily (we
call them "export" libraries in this document). Certain library
functions are altered from specific BIND-only behavior to more generic
behavior when used by other applications; to enable this generic behavior,
the calling program initializes the libraries by calling
<span class="command"><strong>isc_lib_register()</strong></span>.
</p>
<p>
In addition to DNS-related APIs that are used within BIND 9, the
libraries provide the following features:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The "DNS client" module. This is a higher level API that
provides an interface to name resolution, single DNS transaction
with a particular server, and dynamic update. Regarding name
resolution, it supports advanced features such as DNSSEC validation
and caching. This module supports both synchronous and asynchronous
mode.
</p>
</li>
<li class="listitem">
<p>
The "IRS" (Information Retrieval System) library. It provides an
interface to parse the traditional <code class="filename">resolv.conf</code>
file and more advanced, DNS-specific configuration file for the
rest of this package (see the description for the
<code class="filename">dns.conf</code> file below).
</p>
</li>
<li class="listitem">
<p>
As part of the IRS library, the standard address-name
mapping functions, <span class="command"><strong>getaddrinfo()</strong></span> and
<span class="command"><strong>getnameinfo()</strong></span>, are provided. They use the
DNSSEC-aware validating resolver backend, and could use other
advanced features of the BIND 9 libraries such as caching. The
<span class="command"><strong>getaddrinfo()</strong></span> function resolves both A
and AAAA RRs concurrently when the address family is
unspecified.
</p>
</li>
<li class="listitem">
<p>
An experimental framework to support other event
libraries than BIND 9's internal event task system.
</p>
</li>
</ul></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.13.2.5"></a>Installation</h3></div></div></div>
<pre class="screen">
$ <strong class="userinput"><code>make install</code></strong>
</pre>
<p>
Normal installation of BIND will also install library object
and header files. Root privilege is normally required.
</p>
<p>
To see how to build your own application after the installation, see
<code class="filename">lib/samples/Makefile-postinstall.in</code>.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.13.2.6"></a>Known Defects/Restrictions</h3></div></div></div>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The "fixed" RRset order is not (currently) supported in the export
library. If you want to use "fixed" RRset order for, e.g.
<span class="command"><strong>named</strong></span> while still building the export library
even without the fixed order support, build them separately:
</p>
<pre class="screen">
$ <strong class="userinput"><code>./configure --enable-fixed-rrset <em class="replaceable"><code>[other flags, but not --enable-exportlib]</code></em></code></strong>
$ <strong class="userinput"><code>make</code></strong>
$ <strong class="userinput"><code>./configure --enable-exportlib <em class="replaceable"><code>[other flags, but not --enable-fixed-rrset]</code></em></code></strong>
$ <strong class="userinput"><code>cd lib/export</code></strong>
$ <strong class="userinput"><code>make</code></strong>
</pre>
<p>
</p>
</li>
<li class="listitem">
<p>
RFC 5011 is not supported in the validating stub resolver of the
export library. In fact, it is not clear whether it should: trust
anchors would be a system-wide configuration which would be managed
by an administrator, while the stub resolver will be used by
ordinary applications run by a normal user.
</p>
</li>
<li class="listitem">
<p>
Not all common <code class="filename">/etc/resolv.conf</code> options are
supported in the IRS library. The only available options in this
version are <span class="command"><strong>debug</strong></span> and <span class="command"><strong>ndots</strong></span>.
</p>
</li>
</ul></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.13.2.7"></a>The dns.conf File</h3></div></div></div>
<p>
The IRS library supports an "advanced" configuration file related to
the DNS library for configuration parameters that would be beyond the
capability of the <code class="filename">resolv.conf</code> file.
Specifically, it is intended to provide DNSSEC related configuration
parameters. By default the path to this configuration file is
<code class="filename">/etc/dns.conf</code>. This module is very experimental
and the configuration syntax or library interfaces may change in
future versions. Currently, only the <span class="command"><strong>trusted-keys</strong></span>
statement is supported, whose syntax is the same as the same
statement in <code class="filename">named.conf</code>. (See
<a class="xref" href="Bv9ARM.ch06.html#trusted-keys" title="trusted-keys Statement Grammar">the section called “<span class="command"><strong>trusted-keys</strong></span> Statement Grammar”</a> for details.)
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.13.2.8"></a>Sample Applications</h3></div></div></div>
<p>
Some sample application programs using this API are provided for
reference. The following is a brief description of these
applications.
</p>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="id-1.13.2.8.3"></a>sample: a simple stub resolver utility</h4></div></div></div>
<p>
Sends a query of a given name (of a given optional RR type) to a
specified recursive server and prints the result as a list of RRs.
It can also act as a validating stub resolver if a trust anchor is
given via a set of command line options.
</p>
<p>
Usage: sample [options] server_address hostname
</p>
<p>
Options and Arguments:
</p>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">-t RRtype</span></dt>
<dd>
<p>
specify the RR type of the query. The default is the A RR.
</p>
</dd>
<dt><span class="term">[-a algorithm] [-e] -k keyname -K keystring</span></dt>
<dd>
<p>
specify a command-line DNS key to validate the answer. For
example, to specify the following DNSKEY of example.com:
</p>
<div class="literallayout"><p><br>
example.com. 3600 IN DNSKEY 257 3 5 xxx<br>
</p></div>
<p>
specify the options as follows:
</p>
<pre class="screen">
<strong class="userinput"><code>-e -k example.com -K "xxx"</code></strong>
</pre>
<p>
-e means that this key is a zone's "key signing key" (also known
as "secure entry point").
When -a is omitted rsasha1 will be used by default.
</p>
</dd>
<dt><span class="term">-s domain:alt_server_address</span></dt>
<dd>
<p>
specify a separate recursive server address for the specific
"domain". Example: -s example.com:2001:db8::1234
</p>
</dd>
<dt><span class="term">server_address</span></dt>
<dd>
<p>
an IP(v4/v6) address of the recursive server to which queries
are sent.
</p>
</dd>
<dt><span class="term">hostname</span></dt>
<dd>
<p>
the domain name for the query
</p>
</dd>
</dl></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="id-1.13.2.8.4"></a>sample-async: a simple stub resolver, working asynchronously</h4></div></div></div>
<p>
Similar to "sample", but accepts a list
of (query) domain names as a separate file and resolves the names
asynchronously.</p>
<p>
Usage: sample-async [-s server_address] [-t RR_type] input_file</p>
<p>
Options and Arguments:
</p>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">-s server_address</span></dt>
<dd>
an IPv4 address of the recursive server to which queries are sent.
(IPv6 addresses are not supported in this implementation)
</dd>
<dt><span class="term">-t RR_type</span></dt>
<dd>
specify the RR type of the queries. The default is the A
RR.
</dd>
<dt><span class="term">input_file</span></dt>
<dd>
a list of domain names to be resolved. each line consists of a
single domain name. Example:
<div class="literallayout"><p><br>
www.example.com<br>
mx.example.net<br>
ns.xxx.example<br>
</p></div>
</dd>
</dl></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="id-1.13.2.8.5"></a>sample-request: a simple DNS transaction client</h4></div></div></div>
<p>
Sends a query to a specified server, and prints the response with
minimal processing. It doesn't act as a "stub resolver": it stops
the processing once it gets any response from the server, whether
it's a referral or an alias (CNAME or DNAME) that would require
further queries to get the ultimate answer. In other words, this
utility acts as a very simplified <span class="command"><strong>dig</strong></span>.
</p>
<p>
Usage: sample-request [-t RRtype] server_address hostname
</p>
<p>
Options and Arguments:
</p>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">-t RRtype</span></dt>
<dd>
<p>
specify the RR type of the queries. The default is the A RR.
</p>
</dd>
<dt><span class="term">server_address</span></dt>
<dd>
<p>
an IP(v4/v6) address of the recursive server to which
the query is sent.
</p>
</dd>
<dt><span class="term">hostname</span></dt>
<dd>
<p>
the domain name for the query
</p>
</dd>
</dl></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="id-1.13.2.8.6"></a>sample-gai: getaddrinfo() and getnameinfo() test code</h4></div></div></div>
<p>
This is a test program to check <span class="command"><strong>getaddrinfo()</strong></span> and
<span class="command"><strong>getnameinfo()</strong></span> behavior. It takes a host name as an
argument, calls <span class="command"><strong>getaddrinfo()</strong></span> with the given host
name, and calls <span class="command"><strong>getnameinfo()</strong></span> with the resulting
IP addresses returned by <span class="command"><strong>getaddrinfo()</strong></span>. If the
dns.conf file exists and defines a trust anchor, the underlying
resolver will act as a validating resolver, and
<span class="command"><strong>getaddrinfo()</strong></span>/<span class="command"><strong>getnameinfo()</strong></span>
will fail with an EAI_INSECUREDATA error when DNSSEC validation
fails.
</p>
<p>
Usage: sample-gai hostname
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="id-1.13.2.8.7"></a>sample-update: a simple dynamic update client program</h4></div></div></div>
<p>
Accepts a single update command as a command-line argument, sends
an update request message to the authoritative server, and shows
the response from the server. In other words, this is a simplified
<span class="command"><strong>nsupdate</strong></span>.
</p>
<p>
Usage: sample-update [options] (add|delete) "update data"
</p>
<p>
Options and Arguments:
</p>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">-a auth_server</span></dt>
<dd>
<p>
An IP address of the authoritative server that has authority
for the zone containing the update name. This should
normally be the primary authoritative server that accepts
dynamic updates. It can also be a secondary server that is
configured to forward update requests to the primary server.
</p>
</dd>
<dt><span class="term">-k keyfile</span></dt>
<dd>
<p>
A TSIG key file to secure the update transaction. The
keyfile format is the same as that for the nsupdate utility.
</p>
</dd>
<dt><span class="term">-p prerequisite</span></dt>
<dd>
<p>
A prerequisite for the update (only one prerequisite can be
specified). The prerequisite format is the same as that is
accepted by the nsupdate utility.
</p>
</dd>
<dt><span class="term">-r recursive_server</span></dt>
<dd>
<p>
An IP address of a recursive server that this utility will
use. A recursive server may be necessary to identify the
authoritative server address to which the update request is
sent.
</p>
</dd>
<dt><span class="term">-z zonename</span></dt>
<dd>
<p>
The domain name of the zone that contains
</p>
</dd>
<dt><span class="term">(add|delete)</span></dt>
<dd>
<p>
Specify the type of update operation. Either "add" or
"delete" must be specified.
</p>
</dd>
<dt><span class="term">"update data"</span></dt>
<dd>
<p>
Specify the data to be updated. A typical example of the
data would look like "name TTL RRtype RDATA".
</p>
</dd>
</dl></div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
In practice, either -a or -r must be specified. Others can be
optional; the underlying library routine tries to identify the
appropriate server and the zone name for the update.
</p>
</div>
<p>
Examples: assuming the primary authoritative server of the
dynamic.example.com zone has an IPv6 address 2001:db8::1234,
</p>
<pre class="screen">
$ <strong class="userinput"><code>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key add "foo.dynamic.example.com 30 IN A 192.168.2.1"</code></strong></pre>
<p>
adds an A RR for foo.dynamic.example.com using the given key.
</p>
<pre class="screen">
$ <strong class="userinput"><code>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com 30 IN A"</code></strong></pre>
<p>
removes all A RRs for foo.dynamic.example.com using the given key.
</p>
<pre class="screen">
$ <strong class="userinput"><code>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com"</code></strong></pre>
<p>
removes all RRs for foo.dynamic.example.com using the given key.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="id-1.13.2.8.8"></a>nsprobe: domain/name server checker in terms of RFC 4074</h4></div></div></div>
<p>
Checks a set of domains to see the name servers of the domains
behave correctly in terms of RFC 4074. This is included in the set
of sample programs to show how the export library can be used in a
DNS-related application.
</p>
<p>
Usage: nsprobe [-d] [-v [-v...]] [-c cache_address] [input_file]
</p>
<p>
Options
</p>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">-d</span></dt>
<dd>
<p>
Run in "debug" mode. With this option nsprobe will dump
every RRs it receives.
</p>
</dd>
<dt><span class="term">-v</span></dt>
<dd>
<p>
Increase verbosity of other normal log messages. This can be
specified multiple times.
</p>
</dd>
<dt><span class="term">-c cache_address</span></dt>
<dd>
<p>
Specify an IP address of a recursive (caching) name server.
nsprobe uses this server to get the NS RRset of each domain
and the A and/or AAAA RRsets for the name servers. The
default value is 127.0.0.1.
</p>
</dd>
<dt><span class="term">input_file</span></dt>
<dd>
<p>
A file name containing a list of domain (zone) names to be
probed. when omitted the standard input will be used. Each
line of the input file specifies a single domain name such as
"example.com". In general this domain name must be the apex
name of some DNS zone (unlike normal "host names" such as
"www.example.com"). nsprobe first identifies the NS RRsets
for the given domain name, and sends A and AAAA queries to
these servers for some "widely used" names under the zone;
specifically, adding "www" and "ftp" to the zone name.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="id-1.13.2.9"></a>Library References</h3></div></div></div>
<p>
As of this writing, there is no formal "manual" for the libraries,
except this document, header files (some of which provide pretty
detailed explanations), and sample application programs.
</p>
</div>
</div>
</div>
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<td width="40%" align="left" valign="top">Appendix C. General <acronym class="acronym">DNS</acronym> Reference Information </td>
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<p xmlns:db="http://docbook.org/ns/docbook" style="text-align: center;">BIND 9.11.3b1 (Extended Support Version)</p>
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