[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>,
<li>A mirror of my CVS 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>.
</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>

There is a <a href="http://adns.jgaa.com/">port to MS Visual Studio 6
C++</a> by Jarle Aase.

<h2>Copyright and licensing</h2>

<kbd>adns</kbd> is Copyright 1997-2001 Ian Jackson, Copyright
1999-2000 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)1996-2001 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">
ea5ac657	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
d0ac9ea0	166	FTP</A> and <A href="http://www.chiark.greenend.org.uk/~ian/adns/ftp/">HTTP</A>,
630bf698	167	<li>A mirror of my CVS repository is available via rsync from
	168	<code>rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns</code>
	169	(use FTP first to find your way around), or via
	170	<A href="http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/">cvsweb</A>.
	171	</ul>
	172
ea5ac657	173	You can also access the project CVS repositories:
	174	<ul>
	175	<li>A mirror of the source code repository is available via rsync from
	176	<code>rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns</code>
	177	(use FTP first to find your way around), or via
	178	<A href="http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/">cvsweb</A>.
	179	<li>This web page is maintained in
	180	<A href="http://savannah.gnu.org/">Savannah</A>,
	181	where you can browse the
	182	<A href="http://savannah.gnu.org/cgi-bin/viewcvs/software/adns/?cvsroot=www.gnu.org">webpage CVS</A>.
	183	</ul>
	184
630bf698	185	adns is also available from the
	186	<A href="http://www.gnu.org/">GNU Project</A> FTP servers and their
	187	<A href="http://www.gnu.org/order/ftp.html">mirrors</A>.
	188
b6922f88	189	<h2>Technical note</h2>
	190
	191	adns requires a real nameserver like
	192	<A href="http://www.isc.org/view.cgi?/products/BIND/index.phtml">BIND</A>
	193	or
	194	<A href="http://www.dents.org/">Dents</A> running on
	195	the same system or a nearby one, which must be willing to provide
	196	`recursive service'. I.e., adns is a `stub resolver'. All properly
	197	configured UN*X and GNU systems will already have such nameserver(s);
	198	they are usually listed in /etc/resolv.conf.
	199
4fde3e92	200	<h2>References and related projects</h2>
	201
	202	There is a <a href="http://adns.jgaa.com/">port to MS Visual Studio 6
	203	C++</a> by Jarle Aase.
	204
630bf698	205	<h2>Copyright and licensing</h2>
630bf698	206
ea5ac657	207	<kbd>adns</kbd> is Copyright 1997-2001 Ian Jackson, Copyright
b6922f88	208	1999-2000 Tony Finch, and Copyright (C) 1991 Massachusetts Institute
b6922f88	209	of Technology.
630bf698	210
	211	<p>
	212
	213	<kbd>adns</kbd> is free software; you can redistribute it and/or modify
	214	it under the terms of the GNU General Public License as published by
	215	the Free Software Foundation; either version 2 of the License, or (at
	216	your option) any later version.
	217
	218	<p>
	219
	220	This program and documentation is distributed in the hope that it will
	221	be useful, but <em>without any warranty</em>; without even the implied
	222	warranty of <em>merchantability</em> or <em>fitness for a particular
	223	purpose</em>. See the
	224	<A href="http://www.chiark.greenend.org.uk/~ian/COPYING.txt">GNU
	225	General Public License</A> for more details.
	226
	227	<p>
	228
	229	You should have received a copy of the GNU General Public License
	230	along with <kbd>adns</kbd>, or one should be available above; if not,
	231	write to the
	232	<A href="http://www.fsf.org/">Free Software Foundation</A>,
	233	59 Temple Place - Suite 330, Boston, MA 02111-1307, USA,
	234	or email <code>adns-maint@chiark.greenend.org.uk</code>.
	235
	236	<p>
	237
	238	<hr>
	239	<A href="http://www.chiark.greenend.org.uk/">Ian Jackson</A> /
	240	<A href="mailto:adns-maint@chiark.greenend.org.uk"><tt>adns-maint@chiark.greenend.org.uk</tt></A>;
	241	more <A href="http://www.chiark.greenend.org.uk/~ian/software/">free
	242	software</A> by me.
	243	<p>
	244
	245	<A href="http://www.gnu.org/">GNU home page</A>;
	246	<A href="http://www.chiark.greenend.org.uk/">chiark home page</A>;
	247	<A href="/">site or mirror home page</A>
	248	<p>
	249
ea5ac657	250	This web page is Copyright (C)1996-2001 Ian Jackson. See the
630bf698	251	<A href="http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html">Copyright/acknowledgements</A>.
	252	<p>
	253
	254	Use any browser -
	255	<A href="http://www.anybrowser.org/campaign/">Campaign for a non-browser-specific WWW</A>
	256
	257	</body>
	258	</html>