[adns] / README.html

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<h1>GNU adns</h1>

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

<p>

adns is a resolver library for C (and C++) programs.  In contrast with
the existing 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 sanity
checks eg 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>

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 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.

</ul>

<h2>Forthcoming:</h2>

A native Perl interface is in the works, thanks to Tony Finch.

<p>

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.

</ul>

(Technical note: 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>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>.

<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, &c.
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 beta version</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 (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>.
<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>

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>Copyright and licensing</h2>

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