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			BIND-9 DNS Library Support

This version of BIND9 "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 BIND9 is currently using, the export libraries
provide the following features:

- 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.
- 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).
- 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 BIND9 libraries such as caching.  The
  getaddrinfo() function resolves both A and AAAA RRs concurrently
  (when the address family is unspecified).
- An experimental framework to support other event libraries than
  BIND9's internal event task system.

* Prerequisite

GNU make is required to build the export libraries (other part of
BIND9 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.

* Compilation

1. ./configure --enable-exportlib [other flags]
2. make

This will create (in addition to usual BIND9 programs) and a separate
set of libraries under the lib/export directory.  For example,
lib/export/dns/libdns.a is the archive file of the export version of
the BIND9 DNS library.

Sample application programs using the libraries will also be built
under the lib/export/samples directory (see below).

* Installation

1. cd lib/export
2. make install (root privilege is normally required)
   (make install at the top directory will do the same)

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
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the --with-export-includedir configure option (default:
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PREFIX/include/bind9).

To see how to build your own application after the installation, see
lib/export/samples/Makefile-postinstall.in

* Known Defects/Restrictions

- Currently, win32 is not supported for the export library.  (Normal
  BIND9 application can be built as before).
- The "fixed" RRset order is not (currently) supported in the export
  library.  If you want to use "fixed" RRset order for, e.g. named
  while still building the export library even without the fixed
  order support, build them separately:
  % ./configure --enable-fixed-rrset [other flags, but not --enable-exportlib]
  % make (this doesn't have to be make)
  % ./configure --enable-exportlib [other flags, but not --enable-fixed-rrset]
  % cd lib/export
  % make
- 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).
- RFC5011 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.
- Not all common /etc/resolv.conf options are supported in the IRS library.
  The only available options in this version are "debug" and "ndots".

* The dns.conf File

The IRS library supports an "advanced" configuration file related to
the DNS library for configuration parameters that would be beyond the
capability of the resolv.conf file.  Specifically, it is intended to
provide DNSSEC related configuration parameters.

By default the path to this configuration file is /etc/dns.conf.

This module is very experimental and the configuration syntax or
library interfaces may change in future versions.  Currently, only the
'trusted-keys' statement is supported, whose syntax is the same as the
same name of statement for named.conf.

* Sample Applications

Some sample application programs using this API are provided for
reference.  The following is a brief description of these
applications.

- sample: a simple stub resolver utility.

  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.

  Usage: sample [options] server_address hostname

  Options and Arguments:
  -t RRtype
	specify the RR type of the query.  The default is the A RR.
  [-a algorithm] [-e] -k keyname -K keystring
	specify a command-line DNS key to validate the answer.  For
	example, to specify the following DNSKEY of example.com:
		example.com. 3600 IN DNSKEY 257 3 5 xxx
        specify the options as follows:
	  -e -k example.com -K "xxx"
	-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.
  -s domain:alt_server_address
	specify a separate recursive server address for the specific
	"domain".  Example: -s example.com:2001:db8::1234
  server_address
	an IP(v4/v6) address of the recursive server to which queries
	are sent.
  hostname
	the domain name for the query

- sample-async: a simple stub resolver, working asynchronously.

  Similar to "sample", but accepts a list of (query) domain names as a
  separate file and resolves the names asynchronously.

  Usage: sample-async [-s server_address] [-t RR_type] input_file
  Options and Arguments:
  -s server_address
	an IPv4 address of the recursive server to which queries are
	sent.  (IPv6 addresses are not supported in this implementation)
  -t RR_type
	specify the RR type of the queries.  The default is the A RR.
  input_file
	a list of domain names to be resolved.  each line consists of a
	single domain name.  Example:
  	www.example.com
	mx.examle.net
	ns.xxx.example

- sample-request: a simple DNS transaction client.

  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 dig.

  Usage: sample-request [-t RRtype] server_address hostname
  Options and Arguments:
  -t RRtype
	specify the RR type of the queries.  The default is the A RR.
  server_address
	an IP(v4/v6) address of the recursive server to which the query is
	sent.
  hostname
	the domain name for the query

- sample-gai: getaddrinfo() and getnameinfo() test code.

  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.

  Usage: sample-gai hostname

- sample-update: a simple dynamic update client program

  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
  nsupdate.

  Usage: sample-update [options] (add|delete) "update data"
  Options and Arguments:
  -a auth_server
	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.
  -k keyfile
	A TSIG key file to secure the update transaction.  The keyfile
	format is the same as that for the nsupdate utility.
  -p prerequisite
	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.
  -r recursive_server
	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.
  -z zonename
	The domain name of the zone that contains
  (add|delete)
	Specify the type of update operation.  Either "add" or "delete"
	must be specified.
  "update data"
	Specify the data to be updated.  A typical example of the data
	would look like "name TTL RRtype RDATA".

   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.

   Examples: assuming the primary authoritative server of the
   dynamic.example.com zone has an IPv6 address 2001:db8::1234,
   + sample-update -a sample-update -k Kxxx.+nnn+mmmm.key add "foo.dynamic.example.com 30 IN A 192.168.2.1"
     adds an A RR for foo.dynamic.example.com using the given key.
   + sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com 30 IN A"
     removes all A RRs for foo.dynamic.example.com using the given key.
   + sample-update -a sample-update -k Kxxx.+nnn+mmmm.key delete "foo.dynamic.example.com"
     removes all RRs for foo.dynamic.example.com using the given key.

- nsprobe: domain/name server checker in terms of RFC4074.

  It checks a set of domains to see the name servers of the domains
  behave correctly in terms of RFC4074.  This is included in the set
  of sample programs to show how the export library can be used in a
  DNS-related application.

  Usage: nsprobe [-d] [-v [-v...]] [-c cache_address] [input_file]
  Options
  -d
	run in the "debug" mode.  with this option nsprobe will dump
	every RRs it receives.
  -v
	increase verbosity of other normal log messages.  This can be
	specified multiple times
  -c cache_address
	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.
  input_file
	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.

* Library References

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.

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; $Id: README.libdns,v 1.3 2009/09/15 19:12:03 jinmei Exp $