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Advanced, easy to use, asynchronous-capable DNS client library and
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adns is a resolver library for C (and C++) programs, and a collection
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of useful DNS resolver utilities.
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In contrast with the standard interfaces, gethostbyname et al and
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libresolv, it has the following features:
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* It is reasonably easy to use for simple programs which just want
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to translate names to addresses, look up MX records, etc.
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* It can be used in an asynchronous, non-blocking, manner. Many
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queries can be handled simultaneously.
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* Responses are decoded automatically into a natural representation
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for a C program - there is no need to deal with DNS packet
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* Sanity checking (eg, name syntax checking, reverse/forward
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correspondence, CNAME pointing to CNAME) is performed
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* Time-to-live, CNAME and other similar information is returned in
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an easy-to-use form, without getting in the way.
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* There is no global state in the library; resolver state is an
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opaque data structure which the client creates explicitly. A
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program can have several instances of the resolver.
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* Errors are reported to the application in a way that distinguishes
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the various causes of failure properly.
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* Understands conventional resolv.conf, but this can overridden by
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environment variables.
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* Flexibility. For example, the application can tell adns to: ignore
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environment variables (for setuid programs), disable hostname
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syntax sanity checks to return arbitrary data, override or ignore
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resolv.conf in favour of supplied configuration, etc.
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* Believed to be correct ! For example, will correctly back off to
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TCP in case of long replies or queries, or to other nameservers if
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several are available. It has sensible handling of bad responses
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adns also comes with a number of utility programs for use from the
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command line and in scripts:
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* adnslogres is a much faster version of Apache's logresolv program.
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* adnsresfilter is a filter which copies its input to its output,
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replacing IP addresses by the corresponding names, without unduly
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delaying the output. For example, you can usefully pipe the output
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of netstat -n, tcpdump -ln, and the like, into it.
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* adnshost is a general-purpose DNS lookup utility which can be used
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easily in from the command line and from shell scripts to do
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simple lookups. In a more advanced mode it can be used as a
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general-purpose DNS helper program for scripting languages which
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can invoke and communicate with subprocesses. See the [1]adnshost
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usage message for a summary of its capabilities.
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I'm afraid there is no manual yet. However, competent C programmers
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should be able to use the library based on the [2]commented adns.h
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header file, and the usage messages for the programs should be
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I'd be pleased if you would let me know if you're using my library in
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your project, and what you think of it.
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If you are subscribed to adns-discuss please send feedback, including
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bug reports, there; otherwise send mail to
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adns-bugreports@chiark.greenend.org.uk. If you'd prefer that your
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message wasn't forwarded to the adns-bugreports list, send it to
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adns-maint@chiark.greenend.org.uk.
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I have set up mailinglists adns-announce and adns-discuss. The
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announcements list is moderated and will contain only announcements of
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important bugs, new versions, etc. The bug reports address mentioned
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above is also a mailing list; feel free to subscribe to it.
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There are [3]archives and subscription web pages, or you can subscribe
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by sending mail containing the word `subscribe' to
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adns-announce-REQUEST@chiark.greenend.org.uk or
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adns-discuss-REQUEST@chiark.greenend.org.uk.
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Available for download from [4]chiark.greenend.org.uk are:
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* The [5]current release as a gzipped tarfile.
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* [6]adns.h API header file with comments, and [7]usage message for
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adnshost (currently there is no manual, sorry).
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* All versions released so far are also available via [8]anonymous
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* A mirror of my CVS repository is available via rsync from
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rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns (use FTP
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first to find your way around), or via [10]cvsweb.
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adns is also available from the [11]GNU Project FTP servers and their
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adns requires a real nameserver like [13]BIND or [14]Dents running on
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the same system or a nearby one, which must be willing to provide
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`recursive service'. I.e., adns is a `stub resolver'. All properly
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configured UN*X and GNU systems will already have such nameserver(s);
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they are usually listed in /etc/resolv.conf.
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Copyright and licensing
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adns is Copyright 1997-2000 Ian Jackson, Copyright 1999-2000 Tony
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Finch, and Copyright (C) 1991 Massachusetts Institute of Technology.
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adns is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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This program and documentation is distributed in the hope that it will
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be useful, but without any warranty; without even the implied warranty
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of merchantability or fitness for a particular purpose. See the
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[15]GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with adns, or one should be available above; if not, write to
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the [16]Free Software Foundation, 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk.
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_________________________________________________________________
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[17]Ian Jackson / [18]adns-maint@chiark.greenend.org.uk; more [19]free
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[20]GNU home page; [21]chiark home page; [22]site or mirror home page
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This web page is Copyright (C)1996-2000 Ian Jackson. See the
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[23]Copyright/acknowledgements.
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Use any browser - [24]Campaign for a non-browser-specific WWW
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1. http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt
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2. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt
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3. http://www.chiark.greenend.org.uk/mailman/listinfo
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4. http://www.chiark.greenend.org.uk/~ian/adns/
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5. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz
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6. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt
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7. http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt
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8. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/
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9. http://www.chiark.greenend.org.uk/~ian/adns/ftp/
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10. http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/
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11. http://www.gnu.org/
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12. http://www.gnu.org/order/ftp.html
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13. http://www.isc.org/view.cgi?/products/BIND/index.phtml
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14. http://www.dents.org/
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15. http://www.chiark.greenend.org.uk/~ian/COPYING.txt
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16. http://www.fsf.org/
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17. http://www.chiark.greenend.org.uk/
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18. mailto:adns-maint@chiark.greenend.org.uk
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19. http://www.chiark.greenend.org.uk/~ian/software/
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20. http://www.gnu.org/
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21. http://www.chiark.greenend.org.uk/
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22. file://localhost/
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23. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html
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24. http://www.anybrowser.org/campaign/
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