| 1 | |
| 2 | adns |
| 3 | |
| 4 | Advanced, easy to use, asynchronous-capable DNS client library. |
| 5 | |
| 6 | adns is a resolver library for C (and C++) programs. In contrast with |
| 7 | the existing interfaces, gethostbyname et al and libresolv, it has the |
| 8 | following features: |
| 9 | * It is reasonably easy to use for simple programs which just want |
| 10 | to translate names to addresses, look up MX records, etc. |
| 11 | * It can be used in an asynchronous, non-blocking, manner. Many |
| 12 | queries can be handled simultaneously. |
| 13 | * Responses are decoded automatically into a natural representation |
| 14 | for a C program - there is no need to deal with DNS packet |
| 15 | formats. |
| 16 | * Sanity checking (eg, name syntax checking, reverse/forward |
| 17 | correspondence, CNAME pointing to CNAME) is performed |
| 18 | automatically. |
| 19 | * Time-to-live, CNAME and other similar information is returned in |
| 20 | an easy-to-use form, without getting in the way. |
| 21 | * There is no global state in the library; resolver state is an |
| 22 | opaque data structure which the client creates explicitly. A |
| 23 | program can have several instances of the resolver. |
| 24 | * Errors are reported to the application in a way that distinguishes |
| 25 | the various causes of failure properly. |
| 26 | * Understands conventional resolv.conf, but this can overridden by |
| 27 | environment variables. |
| 28 | * Flexibility. For example, the application can tell adns to: ignore |
| 29 | environment variables (for setuid programs), disable sanity checks |
| 30 | eg to return arbitrary data, override or ignore resolv.conf in |
| 31 | favour of supplied configuration, etc. |
| 32 | * Believed to be correct ! For example, will correctly back off to |
| 33 | TCP in case of long replies or queries, or to other nameservers if |
| 34 | several are available. It has sensible handling of bad responses |
| 35 | etc. |
| 36 | |
| 37 | Forthcoming: |
| 38 | |
| 39 | I hope that future versions may also have the following features: |
| 40 | * The library will be useable by threads in a multithreaded program |
| 41 | in a natural way. It will multiplex many threads' queries through |
| 42 | a single query socket. |
| 43 | * Limited caching behaviour. |
| 44 | * IPv6 support. |
| 45 | |
| 46 | (Technical note: adns requires a real nameserver like BIND running on |
| 47 | the same system or a nearby one, which must be willing to provide |
| 48 | `recursive service'. I.e., adns is a `stub resolver'. All properly |
| 49 | configured UN*X and GNU systems will already have such nameserver(s); |
| 50 | they are usually listed in /etc/resolv.conf.) |
| 51 | |
| 52 | Feedback |
| 53 | |
| 54 | If you are subscribed to adns-discuss please send bug reports there; |
| 55 | otherwise mail them to adns-bugreports@chiark.greenend.org.uk. |
| 56 | |
| 57 | Mailinglists |
| 58 | |
| 59 | I have set up mailinglists adns-announce and adns-discuss. The |
| 60 | announcements list is moderated and will contain only announcements of |
| 61 | important bugs, new versions, &c. The bug reports address mentioned |
| 62 | above is also a mailing list; feel free to subscribe to it. |
| 63 | |
| 64 | There are [1]archives and subscription web pages, or you can subscribe |
| 65 | by sending mail containing the word `subscribe' to |
| 66 | adns-announce-REQUEST@chiark.greenend.org.uk or |
| 67 | adns-discuss-REQUEST@chiark.greenend.org.uk. |
| 68 | |
| 69 | Download |
| 70 | |
| 71 | Available for download from [2]chiark.greenend.org.uk are: |
| 72 | * The [3]current pre-release version as a gzipped tarfile. |
| 73 | * All released versions are also available via [4]anonymous FTP. |
| 74 | |
| 75 | adns is also available from the GNU Project FTP servers and their |
| 76 | mirrors. |
| 77 | |
| 78 | Copyright and licensing |
| 79 | |
| 80 | adns is Copyright 1997-1999 Ian Jackson. |
| 81 | |
| 82 | adns is free software; you can redistribute it and/or modify it under |
| 83 | the terms of the GNU General Public License as published by the Free |
| 84 | Software Foundation; either version 2 of the License, or (at your |
| 85 | option) any later version. |
| 86 | |
| 87 | This program and documentation is distributed in the hope that it will |
| 88 | be useful, but without any warranty; without even the implied warranty |
| 89 | of merchantability or fitness for a particular purpose. See the [5]GNU |
| 90 | General Public License for more details. |
| 91 | |
| 92 | You should have received a copy of the GNU General Public License |
| 93 | along with adns, or one should be available above; if not, write to |
| 94 | the [6]Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
| 95 | MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. |
| 96 | _________________________________________________________________ |
| 97 | |
| 98 | [7]Ian Jackson / [8]adns-maint@chiark.greenend.org.uk; more [9]free |
| 99 | software by me. |
| 100 | |
| 101 | [10]GNU home page; [11]site or mirror home page |
| 102 | |
| 103 | This web page is Copyright (C)1996-1999 Ian Jackson. See the |
| 104 | [12]Copyright/acknowledgements. |
| 105 | |
| 106 | Use any browser - [13]Campaign for a non-browser-specific WWW |
| 107 | |
| 108 | References |
| 109 | |
| 110 | 1. http://www.chiark.greenend.org.uk/mailman/listinfo |
| 111 | 2. http://www.chiark.greenend.org.uk/ |
| 112 | 3. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz |
| 113 | 4. ftp://ftp.chiark.greenend.org.uk/users/ian/userv/ |
| 114 | 5. http://www.chiark.greenend.org.uk/~ian/COPYING.txt |
| 115 | 6. http://www.fsf.org/ |
| 116 | 7. http://www.chiark.greenend.org.uk/ |
| 117 | 8. mailto:adns-maint@chiark.greenend.org.uk |
| 118 | 9. http://www.chiark.greenend.org.uk/~ian/software/ |
| 119 | 10. http://www.gnu.org/ |
| 120 | 11. http://www.chiark.greenend.org.uk/ |
| 121 | 12. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html |
| 122 | 13. http://www.anybrowser.org/campaign/ |