[adns] / README.html

<html><head><title>adns - advanced, alternative, asynchronous resolver</title>
<link rev="made" href="mailto:adns-maint@chiark.greenend.org.uk">
<meta name="keywords" content="adns">
</head>
<body>
<h1>GNU adns</h1>

<strong>Advanced, easy to use, asynchronous-capable DNS client
library and utilities.</strong>

<!--      Note: this file must contain portable HTML !            -->
<!--                                                              -->
<!--  It is served on the GNU site and also from my own system,   -->
<!--  under the URL http://www.chiark.greenend.org.uk/adns/       -->
<!--  Please ensure that all links continine to be correct        -->
<!--  both for www.gnu.org and chiark.                            -->
<!--                                                              -->
<!--  $Id$    -->   

<p>

adns is a resolver library for C (and C++) programs, and a collection
of useful DNS resolver utilities.


<h2>C library</h2>

In contrast with the standard interfaces, gethostbyname et al and
libresolv, it has the following features:

<ul>

<li>It is reasonably easy to use for simple programs which just want
to translate names to addresses, look up MX records, etc.

<li>It can be used in an asynchronous, non-blocking, manner.  Many
queries can be handled simultaneously.

<li>Responses are decoded automatically into a natural representation
for a C program - there is no need to deal with DNS packet formats.

<li>Sanity checking (eg, name syntax checking, reverse/forward
correspondence, CNAME pointing to CNAME) is performed automatically.

<li>Time-to-live, CNAME and other similar information is returned in
an easy-to-use form, without getting in the way.

<li>There is no global state in the library; resolver state is an
opaque data structure which the client creates explicitly.  A program
can have several instances of the resolver.

<li>Errors are reported to the application in a way that distinguishes
the various causes of failure properly.

<li>Understands conventional resolv.conf, but this can overridden by
environment variables.

<li>Flexibility.  For example, the application can tell adns to:
ignore environment variables (for setuid programs), disable hostname
syntax sanity checks to return arbitrary data, override or ignore
resolv.conf in favour of supplied configuration, etc.

<li>Believed to be correct !  For example, will correctly back off to
TCP in case of long replies or queries, or to other nameservers if
several are available.  It has sensible handling of bad responses etc.

</ul>

<h2>DNS utility programs</h2>

adns also comes with a number of utility programs for use from the
command line and in scripts:

<ul>

<li><code>adnslogres</code> is a much faster version of Apache's
logresolv program.

<li><code>adnsresfilter</code> is a filter which copies its input to
its output, replacing IP addresses by the corresponding names, without
unduly delaying the output.  For example, you can usefully pipe the
output of netstat -n, tcpdump -ln, and the like, into it.

<li><code>adnshost</code> is a general-purpose DNS lookup utility
which can be used easily in from the command line and from shell
scripts to do simple lookups.  In a more advanced mode it can be used
as a general-purpose DNS helper program for scripting languages which
can invoke and communicate with subprocesses.  See the
<A href="http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt">adnshost
usage message</A> for a summary of its capabilities.

</ul>

<h2>Forthcoming:</h2>

I hope that future versions may also have the following features:

<ul>

<li>The library should be useable by threads in a multithreaded
program in a natural way.  It should multiplex many threads' queries
through a single query socket.

<li>IPv6 support.

<li>Some kind of awareness of DNSSEC.

<li>Possibly some very limited caching behaviour.

<li>There was, at one point, a draft native Perl interface from Tony Finch.

</ul>

<h2>Documentation</h2>

I'm afraid there is no manual yet.  However, competent C programmers
should be able to use the library based on the
<A href="http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt">commented
adns.h header file</A>, and the usage messages for the programs should
be sufficient.

<h2>Feedback</h2>

I'd be pleased if you would let me know if you're using my library in
your project, and what you think of it.

<p>

If you are subscribed to <code>adns-discuss</code> please send
feedback, including bug reports, there; otherwise send mail to
<code>adns-bugreports@chiark.greenend.org.uk</code>.  If you'd prefer
that your message wasn't forwarded to the <code>adns-bugreports</code>
list, send it to <code>adns-maint@chiark.greenend.org.uk</code>.

<h2>Mailinglists</h2>

I have set up mailinglists <code>adns-announce</code> and
<code>adns-discuss</code>.  The announcements list is moderated and
will contain only announcements of important bugs, new versions, etc.
The bug reports address mentioned above is also a mailing list; feel
free to subscribe to it.

<p>

There are
<A href="http://www.chiark.greenend.org.uk/mailman/listinfo">archives
and subscription web pages</A>, or you can subscribe by sending mail
containing the word `subscribe' to
<code>adns-announce-REQUEST@chiark.greenend.org.uk</code> or
<code>adns-discuss-REQUEST@chiark.greenend.org.uk</code>.

<h2>Download</h2>

Available for download from
<A href="http://www.chiark.greenend.org.uk/~ian/adns/">chiark.greenend.org.uk</A>
are:
<ul>
<li>The <A href="http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz">current
    release</A> as a gzipped tarfile.
<li><A href="http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt">adns.h</A>
    API header file with comments, and
    <A href="http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt">usage
    message for adnshost</A> (currently there is no manual, sorry).
<li>All versions released so far are also available via
    <A href="ftp://ftp.chiark.greenend.org.uk/users/ian/adns/">anonymous
    FTP</A> and <A href="http://www.chiark.greenend.org.uk/~ian/adns/ftp/">HTTP</A>.
</ul>

You can also access the project CVS repositories:
<ul>
<li>A mirror of the source code repository is available via rsync from
    <code>rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns</code>
    (use FTP first to find your way around), or via
    <A href="http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/">cvsweb</A>.
<li>This web page is maintained in
    <A href="http://savannah.gnu.org/">Savannah</A>,
    where you can browse the
    <A href="http://savannah.gnu.org/cgi-bin/viewcvs/software/adns/?cvsroot=www.gnu.org">webpage CVS</A>.
</ul>

adns is also available from the
<A href="http://www.gnu.org/">GNU Project</A> FTP servers and their
<A href="http://www.gnu.org/order/ftp.html">mirrors</A>.

<h2>Technical note</h2>

adns requires a real nameserver like
<A href="http://www.isc.org/view.cgi?/products/BIND/index.phtml">BIND</A>
or
<A href="http://www.dents.org/">Dents</A> running on
the same system or a nearby one, which must be willing to provide
`recursive service'.  I.e., adns is a `stub resolver'.  All properly
configured UN*X and GNU systems will already have such nameserver(s);
they are usually listed in /etc/resolv.conf.

<h2>References and related projects</h2>

<ul>
<li><a href="http://code.google.com/p/adns-python">Python bindings</a>
   by Andy Dustman.
<li><a href="http://cryp.to/hsdns/">Haskell bindings</a>
   by Peter Simons.
<li><a href="http://liboop.ofb.net/ref">liboop event loop library</a>
   (by Dan Egnor) has a built-in binding for adns.
<li><a href="http://adns.jgaa.com/">port to MS Visual Studio 6 C++</a>
   by Jarle Aase.
</ul>

<h2>Copyright and licensing</h2>

<kbd>adns</kbd> is Copyright 1997-2000,2003,2006 Ian Jackson,
Copyright 1999-2000,2003,2006 Tony Finch, and Copyright (C) 1991
Massachusetts Institute of Technology.

<p>

<kbd>adns</kbd> is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

<p>

This program and documentation is distributed in the hope that it will
be useful, but <em>without any warranty</em>; without even the implied
warranty of <em>merchantability</em> or <em>fitness for a particular
purpose</em>.  See the
<A href="http://www.chiark.greenend.org.uk/~ian/COPYING.txt">GNU
General Public License</A> for more details.

<p>

You should have received a copy of the GNU General Public License
along with <kbd>adns</kbd>, or one should be available above; if not,
write to the
<A href="http://www.fsf.org/">Free Software Foundation</A>,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA,
or email <code>adns-maint@chiark.greenend.org.uk</code>.

<p>

<hr>
<A href="http://www.chiark.greenend.org.uk/">Ian Jackson</A> / 
<A href="mailto:adns-maint@chiark.greenend.org.uk"><tt>adns-maint@chiark.greenend.org.uk</tt></A>;
more <A href="http://www.chiark.greenend.org.uk/~ian/software/">free
software</A> by me.
<p>

<A href="http://www.gnu.org/">GNU home page</A>;
<A href="http://www.chiark.greenend.org.uk/">chiark home page</A>;
<A href="/">site or mirror home page</A>
<p>

This web page is Copyright (C)1996-2005 Ian Jackson.  See the
<A href="http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html">Copyright/acknowledgements</A>.
<p>

Use any browser -
<A href="http://www.anybrowser.org/campaign/">Campaign for a non-browser-specific WWW</A>

</body>
</html>
Commit	Line	Data
ea5ac657	1	<html><head><title>adns - advanced, alternative, asynchronous resolver</title>
630bf698	2	<link rev="made" href="mailto:adns-maint@chiark.greenend.org.uk">
3a68c787	3	<meta name="keywords" content="adns">
630bf698	4	</head>
	5	<body>
	6	<h1>GNU adns</h1>
	7
	8	<strong>Advanced, easy to use, asynchronous-capable DNS client
	9	library and utilities.</strong>
	10
ea5ac657	11	<!-- Note: this file must contain portable HTML ! -->
b6922f88	12	<!-- -->
	13	<!-- It is served on the GNU site and also from my own system, -->
	14	<!-- under the URL http://www.chiark.greenend.org.uk/adns/ -->
	15	<!-- Please ensure that all links continine to be correct -->
	16	<!-- both for www.gnu.org and chiark. -->
	17	<!-- -->
ea5ac657	18	<!-- $Id$ -->
b6922f88	19
630bf698	20	<p>
630bf698	21
8e5a4960	22	adns is a resolver library for C (and C++) programs, and a collection
b6922f88	23	of useful DNS resolver utilities.
	24
	25
	26	<h2>C library</h2>
	27
	28	In contrast with the standard interfaces, gethostbyname et al and
	29	libresolv, it has the following features:
630bf698	30
	31	<ul>
	32
	33	<li>It is reasonably easy to use for simple programs which just want
	34	to translate names to addresses, look up MX records, etc.
	35
	36	<li>It can be used in an asynchronous, non-blocking, manner. Many
	37	queries can be handled simultaneously.
	38
	39	<li>Responses are decoded automatically into a natural representation
	40	for a C program - there is no need to deal with DNS packet formats.
	41
	42	<li>Sanity checking (eg, name syntax checking, reverse/forward
	43	correspondence, CNAME pointing to CNAME) is performed automatically.
	44
	45	<li>Time-to-live, CNAME and other similar information is returned in
	46	an easy-to-use form, without getting in the way.
	47
	48	<li>There is no global state in the library; resolver state is an
	49	opaque data structure which the client creates explicitly. A program
	50	can have several instances of the resolver.
	51
	52	<li>Errors are reported to the application in a way that distinguishes
	53	the various causes of failure properly.
	54
	55	<li>Understands conventional resolv.conf, but this can overridden by
	56	environment variables.
	57
	58	<li>Flexibility. For example, the application can tell adns to:
8e5a4960	59	ignore environment variables (for setuid programs), disable hostname
	60	syntax sanity checks to return arbitrary data, override or ignore
	61	resolv.conf in favour of supplied configuration, etc.
630bf698	62
	63	<li>Believed to be correct ! For example, will correctly back off to
	64	TCP in case of long replies or queries, or to other nameservers if
	65	several are available. It has sensible handling of bad responses etc.
	66
	67	</ul>
	68
8e5a4960	69	<h2>DNS utility programs</h2>
8e5a4960	70
630bf698	71	adns also comes with a number of utility programs for use from the
	72	command line and in scripts:
	73
	74	<ul>
	75
	76	<li><code>adnslogres</code> is a much faster version of Apache's
	77	logresolv program.
	78
	79	<li><code>adnsresfilter</code> is a filter which copies its input to
	80	its output, replacing IP addresses by the corresponding names, without
	81	unduly delaying the output. For example, you can usefully pipe the
	82	output of netstat -n, tcpdump -ln, and the like, into it.
	83
	84	<li><code>adnshost</code> is a general-purpose DNS lookup utility
8e5a4960	85	which can be used easily in from the command line and from shell
	86	scripts to do simple lookups. In a more advanced mode it can be used
	87	as a general-purpose DNS helper program for scripting languages which
	88	can invoke and communicate with subprocesses. See the
b6922f88	89	<A href="http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt">adnshost
b6922f88	90	usage message</A> for a summary of its capabilities.
630bf698	91
	92	</ul>
	93
ea5ac657	94	<h2>Forthcoming:</h2>
	95
	96	I hope that future versions may also have the following features:
	97
	98	<ul>
	99
	100	<li>The library should be useable by threads in a multithreaded
	101	program in a natural way. It should multiplex many threads' queries
	102	through a single query socket.
	103
	104	<li>IPv6 support.
	105
	106	<li>Some kind of awareness of DNSSEC.
	107
	108	<li>Possibly some very limited caching behaviour.
	109
	110	<li>There was, at one point, a draft native Perl interface from Tony Finch.
	111
	112	</ul>
	113
630bf698	114	<h2>Documentation</h2>
	115
	116	I'm afraid there is no manual yet. However, competent C programmers
	117	should be able to use the library based on the
	118	<A href="http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt">commented
8e5a4960	119	adns.h header file</A>, and the usage messages for the programs should
8e5a4960	120	be sufficient.
630bf698	121
	122	<h2>Feedback</h2>
	123
	124	I'd be pleased if you would let me know if you're using my library in
	125	your project, and what you think of it.
	126
	127	<p>
	128
	129	If you are subscribed to <code>adns-discuss</code> please send
	130	feedback, including bug reports, there; otherwise send mail to
	131	<code>adns-bugreports@chiark.greenend.org.uk</code>. If you'd prefer
	132	that your message wasn't forwarded to the <code>adns-bugreports</code>
	133	list, send it to <code>adns-maint@chiark.greenend.org.uk</code>.
	134
	135	<h2>Mailinglists</h2>
	136
	137	I have set up mailinglists <code>adns-announce</code> and
	138	<code>adns-discuss</code>. The announcements list is moderated and
b6922f88	139	will contain only announcements of important bugs, new versions, etc.
630bf698	140	The bug reports address mentioned above is also a mailing list; feel
	141	free to subscribe to it.
	142
	143	<p>
	144
	145	There are
	146	<A href="http://www.chiark.greenend.org.uk/mailman/listinfo">archives
	147	and subscription web pages</A>, or you can subscribe by sending mail
	148	containing the word `subscribe' to
	149	<code>adns-announce-REQUEST@chiark.greenend.org.uk</code> or
	150	<code>adns-discuss-REQUEST@chiark.greenend.org.uk</code>.
	151
	152	<h2>Download</h2>
	153
	154	Available for download from
	155	<A href="http://www.chiark.greenend.org.uk/~ian/adns/">chiark.greenend.org.uk</A>
	156	are:
	157	<ul>
b6922f88	158	<li>The <A href="http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz">current
b6922f88	159	release</A> as a gzipped tarfile.
630bf698	160	<li><A href="http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt">adns.h</A>
b6922f88	161	API header file with comments, and
aa3ffb57	162	<A href="http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt">usage
b6922f88	163	message for adnshost</A> (currently there is no manual, sorry).
630bf698	164	<li>All versions released so far are also available via
630bf698	165	<A href="ftp://ftp.chiark.greenend.org.uk/users/ian/adns/">anonymous
3a68c787	166	FTP</A> and <A href="http://www.chiark.greenend.org.uk/~ian/adns/ftp/">HTTP</A>.
630bf698	167	</ul>
630bf698	168
ea5ac657	169	You can also access the project CVS repositories:
	170	<ul>
	171	<li>A mirror of the source code repository is available via rsync from
	172	<code>rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns</code>
	173	(use FTP first to find your way around), or via
	174	<A href="http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/">cvsweb</A>.
	175	<li>This web page is maintained in
	176	<A href="http://savannah.gnu.org/">Savannah</A>,
	177	where you can browse the
	178	<A href="http://savannah.gnu.org/cgi-bin/viewcvs/software/adns/?cvsroot=www.gnu.org">webpage CVS</A>.
	179	</ul>
	180
630bf698	181	adns is also available from the
	182	<A href="http://www.gnu.org/">GNU Project</A> FTP servers and their
	183	<A href="http://www.gnu.org/order/ftp.html">mirrors</A>.
	184
b6922f88	185	<h2>Technical note</h2>
	186
	187	adns requires a real nameserver like
	188	<A href="http://www.isc.org/view.cgi?/products/BIND/index.phtml">BIND</A>
	189	or
	190	<A href="http://www.dents.org/">Dents</A> running on
	191	the same system or a nearby one, which must be willing to provide
	192	`recursive service'. I.e., adns is a `stub resolver'. All properly
	193	configured UN*X and GNU systems will already have such nameserver(s);
	194	they are usually listed in /etc/resolv.conf.
	195
4fde3e92	196	<h2>References and related projects</h2>
4fde3e92	197
4f85494a	198	<ul>
1f2daabb	199	<li><a href="http://code.google.com/p/adns-python">Python bindings</a>
4f85494a	200	by Andy Dustman.
4f85494a	201	<li><a href="http://cryp.to/hsdns/">Haskell bindings</a>
217cfd38	202	by Peter Simons.
4f85494a	203	<li><a href="http://liboop.ofb.net/ref">liboop event loop library</a>
	204	(by Dan Egnor) has a built-in binding for adns.
	205	<li><a href="http://adns.jgaa.com/">port to MS Visual Studio 6 C++</a>
217cfd38	206	by Jarle Aase.
4f85494a	207	</ul>
4fde3e92	208
630bf698	209	<h2>Copyright and licensing</h2>
630bf698	210
ae8cc977	211	<kbd>adns</kbd> is Copyright 1997-2000,2003,2006 Ian Jackson,
	212	Copyright 1999-2000,2003,2006 Tony Finch, and Copyright (C) 1991
	213	Massachusetts Institute of Technology.
630bf698	214
	215	<p>
	216
	217	<kbd>adns</kbd> is free software; you can redistribute it and/or modify
	218	it under the terms of the GNU General Public License as published by
	219	the Free Software Foundation; either version 2 of the License, or (at
	220	your option) any later version.
	221
	222	<p>
	223
	224	This program and documentation is distributed in the hope that it will
	225	be useful, but <em>without any warranty</em>; without even the implied
	226	warranty of <em>merchantability</em> or <em>fitness for a particular
	227	purpose</em>. See the
	228	<A href="http://www.chiark.greenend.org.uk/~ian/COPYING.txt">GNU
	229	General Public License</A> for more details.
	230
	231	<p>
	232
	233	You should have received a copy of the GNU General Public License
	234	along with <kbd>adns</kbd>, or one should be available above; if not,
	235	write to the
	236	<A href="http://www.fsf.org/">Free Software Foundation</A>,
	237	59 Temple Place - Suite 330, Boston, MA 02111-1307, USA,
	238	or email <code>adns-maint@chiark.greenend.org.uk</code>.
	239
	240	<p>
	241
	242	<hr>
	243	<A href="http://www.chiark.greenend.org.uk/">Ian Jackson</A> /
	244	<A href="mailto:adns-maint@chiark.greenend.org.uk"><tt>adns-maint@chiark.greenend.org.uk</tt></A>;
	245	more <A href="http://www.chiark.greenend.org.uk/~ian/software/">free
	246	software</A> by me.
	247	<p>
	248
	249	<A href="http://www.gnu.org/">GNU home page</A>;
	250	<A href="http://www.chiark.greenend.org.uk/">chiark home page</A>;
	251	<A href="/">site or mirror home page</A>
	252	<p>
	253
849075a0	254	This web page is Copyright (C)1996-2005 Ian Jackson. See the
630bf698	255	<A href="http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html">Copyright/acknowledgements</A>.
	256	<p>
	257
	258	Use any browser -
	259	<A href="http://www.anybrowser.org/campaign/">Campaign for a non-browser-specific WWW</A>
	260
	261	</body>
	262	</html>