
                                   GNU adns
                                       
   Advanced, easy to use, asynchronous-capable DNS client library and
   utilities.
   
   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:
     * It is reasonably easy to use for simple programs which just want
       to translate names to addresses, look up MX records, etc.
     * It can be used in an asynchronous, non-blocking, manner. Many
       queries can be handled simultaneously.
     * Responses are decoded automatically into a natural representation
       for a C program - there is no need to deal with DNS packet
       formats.
     * Sanity checking (eg, name syntax checking, reverse/forward
       correspondence, CNAME pointing to CNAME) is performed
       automatically.
     * Time-to-live, CNAME and other similar information is returned in
       an easy-to-use form, without getting in the way.
     * 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.
     * Errors are reported to the application in a way that distinguishes
       the various causes of failure properly.
     * Understands conventional resolv.conf, but this can overridden by
       environment variables.
     * 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.
     * 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.
       
   adns also comes with a number of utility programs for use from the
   command line and in scripts:
     * adnslogres is a much faster version of Apache's logresolv program.
     * adnsresfilter 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.
     * adnshost 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.
       
Forthcoming:

   A native Perl interface is in the works, thanks to Tony Finch.
   
   I hope that future versions may also have the following features:
     * 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.
     * IPv6 support.
     * Some kind of awareness of DNSSEC.
     * Possibly some very limited caching behaviour.
       
   (Technical note: adns requires a real nameserver like [1]BIND or
   [2]Dents 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.)
   
Documentation

   I'm afraid there is no manual yet. However, competent C programmers
   should be able to use the library based on the [3]commented adns.h
   header file.
   
Feedback

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

   I have set up mailinglists adns-announce and adns-discuss. 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.
   
   There are [4]archives and subscription web pages, or you can subscribe
   by sending mail containing the word `subscribe' to
   adns-announce-REQUEST@chiark.greenend.org.uk or
   adns-discuss-REQUEST@chiark.greenend.org.uk.
   
Download

   Available for download from [5]chiark.greenend.org.uk are:
     * The [6]current beta version as a gzipped tarfile.
     * [7]adns.h API header file with comments (currently there is no
       manual, sorry).
     * All versions released so far are also available via [8]anonymous
       FTP.
     * A mirror of my CVS repository is available via rsync from
       rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns (use FTP
       first to find your way around), or via [9]cvsweb.
       
   adns is also available from the [10]GNU Project FTP servers and their
   [11]mirrors.
   
Copyright and licensing

   adns is Copyright 1997-1999 Ian Jackson and Copyright 1999 Tony Finch.
   
   adns 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.
   
   This program and documentation is distributed in the hope that it will
   be useful, but without any warranty; without even the implied warranty
   of merchantability or fitness for a particular purpose. See the
   [12]GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with adns, or one should be available above; if not, write to
   the [13]Free Software Foundation, 59 Temple Place - Suite 330, Boston,
   MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk.
     _________________________________________________________________
   
   [14]Ian Jackson / [15]adns-maint@chiark.greenend.org.uk; more [16]free
   software by me.
   
   [17]GNU home page; [18]chiark home page; [19]site or mirror home page
   
   This web page is Copyright (C)1996-1999 Ian Jackson. See the
   [20]Copyright/acknowledgements.
   
   Use any browser - [21]Campaign for a non-browser-specific WWW

References

   1. http://www.isc.org/view.cgi?/products/BIND/index.phtml
   2. http://www.dents.org/
   3. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt
   4. http://www.chiark.greenend.org.uk/mailman/listinfo
   5. http://www.chiark.greenend.org.uk/~ian/adns/
   6. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz
   7. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt
   8. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/
   9. http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/
  10. http://www.gnu.org/
  11. http://www.gnu.org/order/ftp.html
  12. http://www.chiark.greenend.org.uk/~ian/COPYING.txt
  13. http://www.fsf.org/
  14. http://www.chiark.greenend.org.uk/
  15. mailto:adns-maint@chiark.greenend.org.uk
  16. http://www.chiark.greenend.org.uk/~ian/software/
  17. http://www.gnu.org/
  18. http://www.chiark.greenend.org.uk/
  19. http://www.chiark.greenend.org.uk/
  20. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html
  21. http://www.anybrowser.org/campaign/
