<html><head><title>adns - advanced, alternative, asynchronous resolver</title>
<!--
- Note to GNU webmasters and others who might edit this page: This
- file is maintained in GNU CVS, and also served on the author's 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.
+ Note: this file is maintained in Ian Jackson's private CVS.
- If you check in a change, please inform
- webmaster@chiark.greenend.org.uk.
+ 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. In contrast with
-the existing interfaces, gethostbyname et al and libresolv, it has the
-following features:
+adns is a resolver library for C (and C++) programs, and a collection
+of useful DNS resolver utilities. In contrast with the existing
+interfaces, gethostbyname et al and libresolv, it has the following
+features:
<ul>
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.
+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
</ul>
+<h2>DNS utility programs</h2>
+
adns also comes with a number of utility programs for use from the
command line and in scripts:
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.
+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/usage/adnsresfilter_usage.text">usage
+message</A> for a summary of its capabilities.
</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>
+<h2>Technical note</h2>
-(Technical note: adns requires a real nameserver like
+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.)
+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>.
+adns.h header file</A>, and the usage messages for the programs should
+be sufficient.
<h2>Feedback</h2>
~ianmdlvl / adns.git / blobdiff