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[adns] / README
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44d8654a 1
4f3f9880 2 adns
3
44d8654a 4 Advanced, easy to use, asynchronous-capable DNS client library.
4f3f9880 5
44d8654a 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
4f3f9880 20 an easy-to-use form, without getting in the way.
44d8654a 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
4f3f9880 31 favour of supplied configuration, etc.
44d8654a 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.
4f3f9880 36
44d8654a 37Forthcoming:
4f3f9880 38
44d8654a 39 I hope that future versions may also have the following features:
4f3f9880 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.
44d8654a 43 * Limited caching behaviour.
44 * IPv6 support.
4f3f9880 45
44d8654a 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.)
4f3f9880 51
52Feedback
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
57Mailinglists
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
69Download
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
78Copyright 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
108References
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/