                                    GNU adns

   Advanced, easy to use, asynchronous-capable DNS client library and
   utilities.

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

C library

   In contrast with the standard 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 and
       RRDATA formats.
     * Sanity checking (eg, name syntax checking, reverse/forward
       correspondence, CNAME pointing to CNAME) is performed automatically
       by default.
     * 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.
     * adns 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 hostname
       syntax sanity checks 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.

DNS utility programs

   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 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 [1]adnshost
       usage message for a summary of its capabilities.

Documentation

   I'm afraid there is no manual yet. However, competent C programmers
   should be able to use the library based on the [2]commented adns.h
   header file, and the usage messages for the programs should be
   sufficient.

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.

   Bug reports should be reported to the [3]GNU Debbugs. Send an email to
   submit@debbugs.gnu.org and at the top of your email, in a paragraph of
   its own, write the single line
Package: adns

   Your bug report will be published via to the adns-discuss list.

   Feedback and discussion takes place on the adns-discuss list. You can
   mail me privately at ijackson@chiark.greenend.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, etc.

   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.

Documentation

     * [5]adns.h API header file with documentation comments
     * [6]usage message for adnshost

Download and source code

     * The [7]current release as a gzipped tarfile.
     * [8]Previous versions and other files (including OpenPGP
       signatures).
     * [9]master git (version control) repository browser.

   adns is also available from the [10]GNU Project FTP servers and their
   [11]mirrors.

Installation note

   adns requires a real nameserver like BIND running on the same system or
   a nearby one, which must be willing to provide `recursive service'.
   I.e., adns is a `stub resolver'.

   adns requires that your real nameserver is on the same machine, or
   connected via a secure network, so that an attacker cannot fake the
   replies to adns's queries.

References and related projects

     * [12]Python bindings by Andy Dustman.
     * [13]liboop event loop library has a built-in binding for adns.
     * [14]port to MS Visual Studio 6 C++ by Jarle Aase.

Copyright and licensing

   adns is Copyright 1997-2000,2003,2006,2014-2016,2020 Ian Jackson,
   Copyright 2014 Mark Wooding, Copyright 1999-2000,2003,2006 Tony Finch,
   and Copyright 1991 Massachusetts Institute of Technology.

   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 3 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 [15]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
   [16]Free Software Foundation or email ijackson@chiark.greenend.org.uk.
     __________________________________________________________________

   Ian Jackson / ijackson@chiark.greenend.org.uk.

   [17]GNU home page; [18]chiark home page; [19]site or mirror home page

   This web page is Copyright (C)1996-2005,2014-2016 Ian Jackson. See the
   [20]Copyright/acknowledgements.

References

   1. http://www.chiark.greenend.org.uk/~ian/adns/docs/adnshost.txt
   2. http://www.chiark.greenend.org.uk/~ian/adns/docs/adns.h.txt
   3. http://debbugs.gnu.org/
   4. http://www.chiark.greenend.org.uk/mailman/listinfo
   5. http://www.chiark.greenend.org.uk/~ian/adns/docs/adns.h.txt
   6. http://www.chiark.greenend.org.uk/~ian/adns/docs/adnshost.txt
   7. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz
   8. http://www.chiark.greenend.org.uk/~ian/adns/ftp/
   9. http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git/adns.git/
  10. http://www.gnu.org/
  11. http://www.gnu.org/order/ftp.html
  12. http://code.google.com/p/adns-python
  13. http://www.lysator.liu.se/liboop/
  14. http://adns.jgaa.com/
  15. http://www.chiark.greenend.org.uk/~ian/adns/docs/COPYING.txt
  16. http://www.fsf.org/
  17. http://www.gnu.org/
  18. http://www.chiark.greenend.org.uk/
  19. file:///
  20. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html
