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1 | |
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2 | adns |
3 | |
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4 | Advanced, easy to use, asynchronous-capable DNS client library. |
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5 | |
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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 |
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20 | an easy-to-use form, without getting in the way. |
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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 |
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31 | favour of supplied configuration, etc. |
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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. |
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36 | |
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37 | Forthcoming: |
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38 | |
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39 | I hope that future versions may also have the following features: |
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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. |
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43 | * Limited caching behaviour. |
44 | * IPv6 support. |
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45 | |
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46 | (Technical note: adns requires a real nameserver like BIND or [1]Dents |
47 | running on the same system or a nearby one, which must be willing to |
48 | provide `recursive service'. I.e., adns is a `stub resolver'. All |
49 | properly configured UN*X and GNU systems will already have such |
50 | nameserver(s); they are usually listed in /etc/resolv.conf.) |
51 | |
52 | Documentation |
53 | |
54 | I'm afraid there is no manual yet. However, competent C programmers |
55 | should be able to use the library based on the commented [2]adns.h |
56 | header file (from version 0.1). |
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57 | |
58 | Feedback |
59 | |
60 | If you are subscribed to adns-discuss please send bug reports there; |
61 | otherwise mail them to adns-bugreports@chiark.greenend.org.uk. |
62 | |
63 | Mailinglists |
64 | |
65 | I have set up mailinglists adns-announce and adns-discuss. The |
66 | announcements list is moderated and will contain only announcements of |
67 | important bugs, new versions, &c. The bug reports address mentioned |
68 | above is also a mailing list; feel free to subscribe to it. |
69 | |
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70 | There are [3]archives and subscription web pages, or you can subscribe |
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71 | by sending mail containing the word `subscribe' to |
72 | adns-announce-REQUEST@chiark.greenend.org.uk or |
73 | adns-discuss-REQUEST@chiark.greenend.org.uk. |
74 | |
75 | Download |
76 | |
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77 | Available for download from [4]chiark.greenend.org.uk are: |
78 | * The [5]current pre-release version as a gzipped tarfile. |
79 | * [6]adns.h API header file with comments (currently there is no |
80 | manual, sorry). |
81 | * All versions released so far are also available via [7]anonymous |
82 | FTP. |
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83 | |
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84 | adns is also available from the [8]GNU Project FTP servers and their |
85 | [9]mirrors. |
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86 | |
87 | Copyright and licensing |
88 | |
89 | adns is Copyright 1997-1999 Ian Jackson. |
90 | |
91 | adns is free software; you can redistribute it and/or modify it under |
92 | the terms of the GNU General Public License as published by the Free |
93 | Software Foundation; either version 2 of the License, or (at your |
94 | option) any later version. |
95 | |
96 | This program and documentation is distributed in the hope that it will |
97 | be useful, but without any warranty; without even the implied warranty |
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98 | of merchantability or fitness for a particular purpose. See the |
99 | [10]GNU General Public License for more details. |
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100 | |
101 | You should have received a copy of the GNU General Public License |
102 | along with adns, or one should be available above; if not, write to |
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103 | the [11]Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
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104 | MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. |
105 | _________________________________________________________________ |
106 | |
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107 | [12]Ian Jackson / [13]adns-maint@chiark.greenend.org.uk; more [14]free |
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108 | software by me. |
109 | |
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110 | [15]GNU home page; [16]chiark home page; [17]site or mirror home page |
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111 | |
112 | This web page is Copyright (C)1996-1999 Ian Jackson. See the |
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113 | [18]Copyright/acknowledgements. |
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114 | |
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115 | Use any browser - [19]Campaign for a non-browser-specific WWW |
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116 | |
117 | References |
118 | |
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119 | 1. http://www.dents.org/ |
120 | 2. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.0.1.txt |
121 | 3. http://www.chiark.greenend.org.uk/mailman/listinfo |
122 | 4. http://www.chiark.greenend.org.uk/~ian/adns/ |
123 | 5. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz |
124 | 6. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.0.1.txt |
125 | 7. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/ |
126 | 8. http://www.gnu.org/ |
127 | 9. http://www.gnu.org/order/ftp.html |
128 | 10. http://www.chiark.greenend.org.uk/~ian/COPYING.txt |
129 | 11. http://www.fsf.org/ |
130 | 12. http://www.chiark.greenend.org.uk/ |
131 | 13. mailto:adns-maint@chiark.greenend.org.uk |
132 | 14. http://www.chiark.greenend.org.uk/~ian/software/ |
133 | 15. http://www.gnu.org/ |
134 | 16. http://www.chiark.greenend.org.uk/ |
135 | 17. http://www.chiark.greenend.org.uk/ |
136 | 18. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html |
137 | 19. http://www.anybrowser.org/campaign/ |