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 BIND or [1]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 [2]adns.h header file (from version 0.3). 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 [3]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 [4]chiark.greenend.org.uk are: * The [5]current pre-release version as a gzipped tarfile. * [6]adns.h API header file with comments (currently there is no manual, sorry). * All versions released so far are also available via [7]anonymous FTP. adns is also available from the [8]GNU Project FTP servers and their [9]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 [10]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 [11]Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. _________________________________________________________________ [12]Ian Jackson / [13]adns-maint@chiark.greenend.org.uk; more [14]free software by me. [15]GNU home page; [16]chiark home page; [17]site or mirror home page This web page is Copyright (C)1996-1999 Ian Jackson. See the [18]Copyright/acknowledgements. Use any browser - [19]Campaign for a non-browser-specific WWW References 1. http://www.dents.org/ 2. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.0.3.txt 3. http://www.chiark.greenend.org.uk/mailman/listinfo 4. http://www.chiark.greenend.org.uk/~ian/adns/ 5. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz 6. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.0.3.txt 7. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/ 8. http://www.gnu.org/ 9. http://www.gnu.org/order/ftp.html 10. http://www.chiark.greenend.org.uk/~ian/COPYING.txt 11. http://www.fsf.org/ 12. http://www.chiark.greenend.org.uk/ 13. mailto:adns-maint@chiark.greenend.org.uk 14. http://www.chiark.greenend.org.uk/~ian/software/ 15. http://www.gnu.org/ 16. http://www.chiark.greenend.org.uk/ 17. http://www.chiark.greenend.org.uk/ 18. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html 19. http://www.anybrowser.org/campaign/