path: root/doc/arm/libdns.xml

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<section xmlns:db="http://docbook.org/ns/docbook" version="5.0" xml:id="bind9.library">
  <info>
    <title>BIND 9 DNS Library Support</title>
  </info>
  <para>
    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
    <command>isc_lib_register()</command>.
  </para>
  <para>
    In addition to DNS-related APIs that are used within BIND 9, the
    libraries provide the following features:
  </para>
  <itemizedlist>
    <listitem>
      <para>
	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.
      </para>
    </listitem>
    <listitem>
      <para>
	The "IRS" (Information Retrieval System) library.  It provides an
	interface to parse the traditional <filename>resolv.conf</filename>
	file and more advanced, DNS-specific configuration file for the
	rest of this package (see the description for the
	<filename>dns.conf</filename> file below).
      </para>
    </listitem>
    <listitem>
      <para>
	As part of the IRS library, the standard address-name
	mapping functions, <command>getaddrinfo()</command> and
	<command>getnameinfo()</command>, 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
	<command>getaddrinfo()</command> function resolves both A
	and AAAA RRs concurrently when the address family is
	unspecified.
      </para>
    </listitem>
    <listitem>
      <para>
	An experimental framework to support other event
	libraries than BIND 9's internal event task system.
      </para>
    </listitem>
  </itemizedlist>
  <section>
    <info>
      <title>Installation</title>
    </info>
    <screen>
$ <userinput>make install</userinput>
    </screen>
    <para>
      Normal installation of BIND will also install library object
      and header files.  Root privilege is normally required.
    </para>
    <para>
      To see how to build your own application after the installation, see
      <filename>lib/samples/Makefile-postinstall.in</filename>.
    </para>
  </section>
  <section>
    <info>
      <title>Known Defects/Restrictions</title>
    </info>
    <itemizedlist>
      <listitem>
        <para>
	The "fixed" RRset order is not (currently) supported in the export
	library. If you want to use "fixed" RRset order for, e.g.
	<command>named</command> while still building the export library
	even without the fixed order support, build them separately:
      <screen>
$ <userinput>./configure --enable-fixed-rrset <replaceable>[other flags, but not --enable-exportlib]</replaceable></userinput>
$ <userinput>make</userinput>
$ <userinput>./configure --enable-exportlib <replaceable>[other flags, but not --enable-fixed-rrset]</replaceable></userinput>
$ <userinput>cd lib/export</userinput>
$ <userinput>make</userinput>
</screen>
      </para>
      </listitem>
      <listitem>
        <para>
	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.
      </para>
      </listitem>
      <listitem>
        <para>
	Not all common <filename>/etc/resolv.conf</filename> options are
	supported in the IRS library. The only available options in this
	version are <command>debug</command> and <command>ndots</command>.
      </para>
      </listitem>
    </itemizedlist>
  </section>
  <section>
    <info>
      <title>The dns.conf File</title>
    </info>
    <para>
      The IRS library supports an "advanced" configuration file related to
      the DNS library for configuration parameters that would be beyond the
      capability of the <filename>resolv.conf</filename> file.
      Specifically, it is intended to provide DNSSEC related configuration
      parameters. By default the path to this configuration file is
      <filename>/etc/dns.conf</filename>.  This module is very experimental
      and the configuration syntax or library interfaces may change in
      future versions. Currently, only the <command>trusted-keys</command>
      statement is supported, whose syntax is the same as the same
      statement in <filename>named.conf</filename>. (See
      <xref linkend="trusted-keys"/> for details.)
    </para>
  </section>
  <section>
    <info>
      <title>Sample Applications</title>
    </info>
    <para>
      Some sample application programs using this API are provided for
      reference. The following is a brief description of these
      applications.
    </para>
    <section>
      <info>
        <title>sample: a simple stub resolver utility</title>
      </info>
      <para>
	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.
      </para>
      <para>
	Usage: sample [options] server_address hostname
      </para>
      <para>
	Options and Arguments:
      </para>
      <variablelist>
        <varlistentry>
          <term>-t RRtype</term>
          <listitem>
            <para>
	      specify the RR type of the query.  The default is the A RR.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>[-a algorithm] [-e] -k keyname -K keystring</term>
          <listitem>
            <para>
	      specify a command-line DNS key to validate the answer.  For
	      example, to specify the following DNSKEY of example.com:
	      <literallayout>
	              example.com. 3600 IN DNSKEY 257 3 5 xxx
	      </literallayout>
	      specify the options as follows:
	      <screen>
<userinput>-e -k example.com -K "xxx"</userinput>
	      </screen>
	      -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.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>-s domain:alt_server_address</term>
          <listitem>
            <para>
	       specify a separate recursive server address for the specific
	       "domain".  Example: -s example.com:2001:db8::1234
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>server_address</term>
          <listitem>
            <para>
	      an IP(v4/v6) address of the recursive server to which queries
	      are sent.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>hostname</term>
          <listitem>
            <para>
	      the domain name for the query
	</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section>
      <info>
        <title>sample-async: a simple stub resolver, working asynchronously</title>
      </info>
      <para>
      Similar to "sample", but accepts a list
      of (query) domain names as a separate file and resolves the names
      asynchronously.</para>
      <para>
	Usage: sample-async [-s server_address] [-t RR_type] input_file</para>
      <para>
     Options and Arguments:
      </para>
      <variablelist>
        <varlistentry>
          <term>-s server_address</term>
          <listitem>
       an IPv4 address of the recursive server to which queries are sent.
      (IPv6 addresses are not supported in this implementation)
      </listitem>
        </varlistentry>
        <varlistentry>
          <term>-t RR_type</term>
          <listitem>
      specify the RR type of the queries. The default is the A
      RR.
      </listitem>
        </varlistentry>
        <varlistentry>
          <term>input_file</term>
	  <listitem>
	    a list of domain names to be resolved. each line consists of a
	    single domain name. Example:
      <literallayout>
      www.example.com
      mx.example.net
      ns.xxx.example
      </literallayout>
	  </listitem>
	</varlistentry>
      </variablelist>
    </section>
    <section>
      <info>
        <title>sample-request: a simple DNS transaction client</title>
      </info>
      <para>
	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 <command>dig</command>.
      </para>
      <para>
	Usage: sample-request [-t RRtype] server_address hostname
      </para>
      <para>
	Options and Arguments:
      </para>
      <variablelist>
        <varlistentry>
          <term>-t RRtype</term>
          <listitem>
	    <para>
	      specify the RR type of the queries. The default is the A RR.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>server_address</term>
          <listitem>
	    <para>
	      an IP(v4/v6) address of the recursive server to which
	      the query is sent.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>hostname</term>
          <listitem>
	    <para>
	      the domain name for the query
	    </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section>
      <info>
        <title>sample-gai: getaddrinfo() and getnameinfo() test code</title>
      </info>
      <para>
	This is a test program to check <command>getaddrinfo()</command> and
	<command>getnameinfo()</command> behavior. It takes a host name as an
	argument, calls <command>getaddrinfo()</command> with the given host
	name, and calls <command>getnameinfo()</command> with the resulting
	IP addresses returned by <command>getaddrinfo()</command>. If the
	dns.conf file exists and defines a trust anchor, the underlying
	resolver will act as a validating resolver, and
	<command>getaddrinfo()</command>/<command>getnameinfo()</command>
	will fail with an EAI_INSECUREDATA error when DNSSEC validation
	fails.
      </para>
      <para>
	Usage: sample-gai hostname
      </para>
    </section>
    <section>
      <info>
        <title>sample-update: a simple dynamic update client program</title>
      </info>
      <para>
	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
	<command>nsupdate</command>.
      </para>
      <para>
	Usage: sample-update [options] (add|delete) "update data"
      </para>
      <para>
	Options and Arguments:
      </para>
      <variablelist>
        <varlistentry>
          <term>-a auth_server</term>
          <listitem>
	    <para>
	      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.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>-k keyfile</term>
          <listitem>
	    <para>
	      A TSIG key file to secure the update transaction.  The
	      keyfile format is the same as that for the nsupdate utility.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>-p prerequisite</term>
          <listitem>
	    <para>
	      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.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>-r recursive_server</term>
          <listitem>
	    <para>
	      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.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>-z zonename</term>
          <listitem>
	    <para>
	      The domain name of the zone that contains
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>(add|delete)</term>
          <listitem>
	    <para>
	      Specify the type of update operation.  Either "add" or
	      "delete" must be specified.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
	  <term>"update data"</term>
          <listitem>
	    <para>
	      Specify the data to be updated.  A typical example of the
	      data would look like "name TTL RRtype RDATA".
	    </para>
          </listitem>
        </varlistentry>
      </variablelist>
      <note>
	<simpara>
	  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.
	</simpara>
      </note>
      <para>
	Examples: assuming the primary authoritative server of the
	dynamic.example.com zone has an IPv6 address 2001:db8::1234,
      </para>
      <screen>
$ <userinput>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key add "foo.dynamic.example.com 30 IN A 192.168.2.1"</userinput></screen>
      <para>
	adds an A RR for foo.dynamic.example.com using the given key.
      </para>
      <screen>
$ <userinput>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com 30 IN A"</userinput></screen>
      <para>
	removes all A RRs for foo.dynamic.example.com using the given key.
      </para>
      <screen>
$ <userinput>sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com"</userinput></screen>
      <para>
	removes all RRs for foo.dynamic.example.com using the given key.
      </para>
    </section>
    <section>
      <info>
        <title>nsprobe: domain/name server checker in terms of RFC 4074</title>
      </info>
      <para>
	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.
      </para>
      <para>
	Usage: nsprobe [-d] [-v [-v...]] [-c cache_address] [input_file]
      </para>
      <para>
	Options
      </para>
      <variablelist>
        <varlistentry>
          <term>-d</term>
          <listitem>
	    <para>
	      Run in "debug" mode.  With this option nsprobe will dump
	      every RRs it receives.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>-v</term>
          <listitem>
	    <para>
	      Increase verbosity of other normal log messages.  This can be
	      specified multiple times.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>-c cache_address</term>
          <listitem>
	    <para>
	      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.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>input_file</term>
          <listitem>
	    <para>
	      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.
	    </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
  </section>
  <section>
    <info>
      <title>Library References</title>
    </info>
    <para>
      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.
    </para>
  </section>
</section>