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<sect1 id="bind9.library">
<title>BIND 9 DNS Library Support</title>
<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). In addition to
all major DNS-related APIs BIND 9 is currently using, the export
libraries provide the following features:</para>
<itemizedlist>
<listitem>
<para>The newly created "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 new "IRS" (Information Retrieval System) library.
It provides an interface to parse the traditional resolv.conf
file and more advanced, DNS-specific configuration file for
the rest of this package (see the description for the
dns.conf file below).</para>
</listitem>
<listitem>
<para>As part of the IRS library, newly implemented standard
address-name mapping functions, getaddrinfo() and
getnameinfo(), 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
getaddrinfo() 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>
<sect2>
<title>Prerequisite</title>
<para>GNU make is required to build the export libraries (other
part of BIND 9 can still be built with other types of make). In
the reminder of this document, "make" means GNU make. Note that
in some platforms you may need to invoke a different command name
than "make" (e.g. "gmake") to indicate it's GNU make.</para>
</sect2>
<sect2>
<title>Compilation</title>
<screen>
$ <userinput>./configure --enable-exportlib <replaceable>[other flags]</replaceable></userinput>
$ <userinput>make</userinput>
</screen>
<para>
This will create (in addition to usual BIND 9 programs) and a
separate set of libraries under the lib/export directory. For
example, <filename>lib/export/dns/libdns.a</filename> is the archive file of the
export version of the BIND 9 DNS library. Sample application
programs using the libraries will also be built under the
lib/export/samples directory (see below).</para>
</sect2>
<sect2>
<title>Installation</title>
<screen>
$ <userinput>cd lib/export</userinput>
$ <userinput>make install</userinput>
</screen>
<para>
This will install library object files under the directory
specified by the --with-export-libdir configure option (default:
EPREFIX/lib/bind9), and header files under the directory
specified by the --with-export-includedir configure option
(default: PREFIX/include/bind9).
Root privilege is normally required.
"<command>make install</command>" at the top directory will do the
same.
</para>
<para>
To see how to build your own
application after the installation, see
<filename>lib/export/samples/Makefile-postinstall.in</filename>.</para>
</sect2>
<sect2>
<title>Known Defects/Restrictions</title>
<itemizedlist>
<listitem>
<!-- TODO: what about AIX? -->
<para>Currently, win32 is not supported for the export
library. (Normal BIND 9 application can be built as
before).</para>
</listitem>
<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>The client module and the IRS library currently do not
support DNSSEC validation using DLV (the underlying modules
can handle it, but there is no tunable interface to enable
the feature).</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 "debug" and "ndots".</para>
</listitem>
</itemizedlist>
</sect2>
<sect2>
<title>The dns.conf File</title>
<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 name
of statement for <filename>named.conf</filename>. (See
<xref linkend="trusted-keys" /> for details.)</para>
</sect2>
<sect2>
<title>Sample Applications</title>
<para>Some sample application programs using this API are
provided for reference. The following is a brief description of
these applications.
</para>
<sect3>
<title>sample: a simple stub resolver utility</title>
<para>
It 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" (as 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>
</sect3>
<sect3>
<title>sample-async: a simple stub resolver, working asynchronously</title>
<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.examle.net
ns.xxx.example
</literallayout>
</listitem>
</varlistentry>
</variablelist>
</sect3>
<sect3>
<title>sample-request: a simple DNS transaction client</title>
<para>
It 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>
</sect3>
<sect3>
<title>sample-gai: getaddrinfo() and getnameinfo() test code</title>
<para>
This is a test program
to check getaddrinfo() and getnameinfo() behavior. It takes a
host name as an argument, calls getaddrinfo() with the given host
name, and calls getnameinfo() with the resulting IP addresses
returned by getaddrinfo(). If the dns.conf file exists and
defines a trust anchor, the underlying resolver will act as a
validating resolver, and getaddrinfo()/getnameinfo() will fail
with an EAI_INSECUREDATA error when DNSSEC validation fails.
</para>
<para>
Usage: sample-gai hostname
</para>
</sect3>
<sect3>
<title>sample-update: a simple dynamic update client program</title>
<para>
It 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>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.</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>
</sect3>
<sect3>
<title>nsprobe: domain/name server checker in terms of RFC 4074</title>
<para>
It 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 the "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>
</sect3>
</sect2>
<sect2>
<title>Library References</title>
<para>As of this writing, there is no formal "manual" of the
libraries, except this document, header files (some of them
provide pretty detailed explanations), and sample application
programs.</para>
</sect2>
</sect1>
<!-- $Id: libdns.xml,v 1.3 2010-02-03 23:49:07 tbox Exp $ -->
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