| 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 should be useable by threads in a multithreaded |
| 41 | program in a natural way. It should multiplex many threads' |
| 42 | queries through a single query socket. |
| 43 | * IPv6 support. |
| 44 | * Some kind of awareness of DNSSEC. |
| 45 | * Possibly some very limited caching behaviour. |
| 46 | |
| 47 | (Technical note: adns requires a real nameserver like BIND or [1]Dents |
| 48 | running on the same system or a nearby one, which must be willing to |
| 49 | provide `recursive service'. I.e., adns is a `stub resolver'. All |
| 50 | properly configured UN*X and GNU systems will already have such |
| 51 | nameserver(s); they are usually listed in /etc/resolv.conf.) |
| 52 | |
| 53 | Documentation |
| 54 | |
| 55 | I'm afraid there is no manual yet. However, competent C programmers |
| 56 | should be able to use the library based on the commented [2]adns.h |
| 57 | header file (from version 0.3). |
| 58 | |
| 59 | Feedback |
| 60 | |
| 61 | I'd be pleased if you would let me know if you're using my library in |
| 62 | your project, and what you think of it. |
| 63 | |
| 64 | If you are subscribed to adns-discuss please send feedback, including |
| 65 | bug reports, there; otherwise send mail to |
| 66 | adns-bugreports@chiark.greenend.org.uk. If you'd prefer that your |
| 67 | message wasn't forwarded to the adns-bugreports list, send it to |
| 68 | adns-maint@chiark.greendend.org.uk. |
| 69 | |
| 70 | Mailinglists |
| 71 | |
| 72 | I have set up mailinglists adns-announce and adns-discuss. The |
| 73 | announcements list is moderated and will contain only announcements of |
| 74 | important bugs, new versions, &c. The bug reports address mentioned |
| 75 | above is also a mailing list; feel free to subscribe to it. |
| 76 | |
| 77 | There are [3]archives and subscription web pages, or you can subscribe |
| 78 | by sending mail containing the word `subscribe' to |
| 79 | adns-announce-REQUEST@chiark.greenend.org.uk or |
| 80 | adns-discuss-REQUEST@chiark.greenend.org.uk. |
| 81 | |
| 82 | Download |
| 83 | |
| 84 | Available for download from [4]chiark.greenend.org.uk are: |
| 85 | * The [5]current pre-release version as a gzipped tarfile. |
| 86 | * [6]adns.h API header file with comments (currently there is no |
| 87 | manual, sorry). |
| 88 | * All versions released so far are also available via [7]anonymous |
| 89 | FTP. |
| 90 | |
| 91 | adns is also available from the [8]GNU Project FTP servers and their |
| 92 | [9]mirrors. |
| 93 | |
| 94 | Copyright and licensing |
| 95 | |
| 96 | adns is Copyright 1997-1999 Ian Jackson. |
| 97 | |
| 98 | adns is free software; you can redistribute it and/or modify it under |
| 99 | the terms of the GNU General Public License as published by the Free |
| 100 | Software Foundation; either version 2 of the License, or (at your |
| 101 | option) any later version. |
| 102 | |
| 103 | This program and documentation is distributed in the hope that it will |
| 104 | be useful, but without any warranty; without even the implied warranty |
| 105 | of merchantability or fitness for a particular purpose. See the |
| 106 | [10]GNU General Public License for more details. |
| 107 | |
| 108 | You should have received a copy of the GNU General Public License |
| 109 | along with adns, or one should be available above; if not, write to |
| 110 | the [11]Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
| 111 | MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. |
| 112 | _________________________________________________________________ |
| 113 | |
| 114 | [12]Ian Jackson / [13]adns-maint@chiark.greenend.org.uk; more [14]free |
| 115 | software by me. |
| 116 | |
| 117 | [15]GNU home page; [16]chiark home page; [17]site or mirror home page |
| 118 | |
| 119 | This web page is Copyright (C)1996-1999 Ian Jackson. See the |
| 120 | [18]Copyright/acknowledgements. |
| 121 | |
| 122 | Use any browser - [19]Campaign for a non-browser-specific WWW |
| 123 | |
| 124 | References |
| 125 | |
| 126 | 1. http://www.dents.org/ |
| 127 | 2. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.0.3.txt |
| 128 | 3. http://www.chiark.greenend.org.uk/mailman/listinfo |
| 129 | 4. http://www.chiark.greenend.org.uk/~ian/adns/ |
| 130 | 5. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz |
| 131 | 6. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.0.3.txt |
| 132 | 7. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/ |
| 133 | 8. http://www.gnu.org/ |
| 134 | 9. http://www.gnu.org/order/ftp.html |
| 135 | 10. http://www.chiark.greenend.org.uk/~ian/COPYING.txt |
| 136 | 11. http://www.fsf.org/ |
| 137 | 12. http://www.chiark.greenend.org.uk/ |
| 138 | 13. mailto:adns-maint@chiark.greenend.org.uk |
| 139 | 14. http://www.chiark.greenend.org.uk/~ian/software/ |
| 140 | 15. http://www.gnu.org/ |
| 141 | 16. http://www.chiark.greenend.org.uk/ |
| 142 | 17. http://www.chiark.greenend.org.uk/ |
| 143 | 18. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html |
| 144 | 19. http://www.anybrowser.org/campaign/ |