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GNU adns
Advanced, easy to use, asynchronous-capable DNS client library.
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.
Forthcoming:
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 commented [3]adns.h
header file (from version 0.4).
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 pre-release 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).
adns is also available from the [9]GNU Project FTP servers and their
[10]mirrors.
Copyright and licensing
adns is Copyright 1997-1999 Ian Jackson.
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
[11]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 [12]Free Software Foundation, 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk.
_________________________________________________________________
[13]Ian Jackson / [14]adns-maint@chiark.greenend.org.uk; more [15]free
software by me.
[16]GNU home page; [17]chiark home page; [18]site or mirror home page
This web page is Copyright (C)1996-1999 Ian Jackson. See the
[19]Copyright/acknowledgements.
Use any browser - [20]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.0.4.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.0.5.txt
8. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/
9. http://www.gnu.org/
10. http://www.gnu.org/order/ftp.html
11. http://www.chiark.greenend.org.uk/~ian/COPYING.txt
12. http://www.fsf.org/
13. http://www.chiark.greenend.org.uk/
14. mailto:adns-maint@chiark.greenend.org.uk
15. http://www.chiark.greenend.org.uk/~ian/software/
16. http://www.gnu.org/
17. http://www.chiark.greenend.org.uk/
18. http://www.chiark.greenend.org.uk/
19. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html
20. http://www.anybrowser.org/campaign/
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