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1 | |
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2 | GNU adns |
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3 | |
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4 | Advanced, easy to use, asynchronous-capable DNS client library and |
5 | utilities. |
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6 | |
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7 | adns is a resolver library for C (and C++) programs, and a collection |
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8 | of useful DNS resolver utilities. |
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9 | |
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10 | C library |
11 | |
12 | In contrast with the standard interfaces, gethostbyname et al and |
13 | libresolv, it has the following features: |
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14 | * It is reasonably easy to use for simple programs which just want |
15 | to translate names to addresses, look up MX records, etc. |
16 | * It can be used in an asynchronous, non-blocking, manner. Many |
17 | queries can be handled simultaneously. |
18 | * Responses are decoded automatically into a natural representation |
19 | for a C program - there is no need to deal with DNS packet |
20 | formats. |
21 | * Sanity checking (eg, name syntax checking, reverse/forward |
22 | correspondence, CNAME pointing to CNAME) is performed |
23 | automatically. |
24 | * Time-to-live, CNAME and other similar information is returned in |
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25 | an easy-to-use form, without getting in the way. |
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26 | * There is no global state in the library; resolver state is an |
27 | opaque data structure which the client creates explicitly. A |
28 | program can have several instances of the resolver. |
29 | * Errors are reported to the application in a way that distinguishes |
30 | the various causes of failure properly. |
31 | * Understands conventional resolv.conf, but this can overridden by |
32 | environment variables. |
33 | * Flexibility. For example, the application can tell adns to: ignore |
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34 | environment variables (for setuid programs), disable hostname |
35 | syntax sanity checks to return arbitrary data, override or ignore |
36 | resolv.conf in favour of supplied configuration, etc. |
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37 | * Believed to be correct ! For example, will correctly back off to |
38 | TCP in case of long replies or queries, or to other nameservers if |
39 | several are available. It has sensible handling of bad responses |
40 | etc. |
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41 | |
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42 | DNS utility programs |
43 | |
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44 | adns also comes with a number of utility programs for use from the |
45 | command line and in scripts: |
46 | * adnslogres is a much faster version of Apache's logresolv program. |
47 | * adnsresfilter is a filter which copies its input to its output, |
48 | replacing IP addresses by the corresponding names, without unduly |
49 | delaying the output. For example, you can usefully pipe the output |
50 | of netstat -n, tcpdump -ln, and the like, into it. |
51 | * adnshost is a general-purpose DNS lookup utility which can be used |
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52 | easily in from the command line and from shell scripts to do |
53 | simple lookups. In a more advanced mode it can be used as a |
54 | general-purpose DNS helper program for scripting languages which |
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55 | can invoke and communicate with subprocesses. See the [1]adnshost |
56 | usage message for a summary of its capabilities. |
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57 | |
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58 | Forthcoming: |
59 | |
60 | I hope that future versions may also have the following features: |
61 | * The library should be useable by threads in a multithreaded |
62 | program in a natural way. It should multiplex many threads' |
63 | queries through a single query socket. |
64 | * IPv6 support. |
65 | * Some kind of awareness of DNSSEC. |
66 | * Possibly some very limited caching behaviour. |
67 | * There was, at one point, a draft native Perl interface from Tony |
68 | Finch. |
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69 | |
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70 | Documentation |
71 | |
72 | I'm afraid there is no manual yet. However, competent C programmers |
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73 | should be able to use the library based on the [2]commented adns.h |
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74 | header file, and the usage messages for the programs should be |
75 | sufficient. |
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76 | |
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77 | Feedback |
78 | |
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79 | I'd be pleased if you would let me know if you're using my library in |
80 | your project, and what you think of it. |
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81 | |
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82 | If you are subscribed to adns-discuss please send feedback, including |
83 | bug reports, there; otherwise send mail to |
84 | adns-bugreports@chiark.greenend.org.uk. If you'd prefer that your |
85 | message wasn't forwarded to the adns-bugreports list, send it to |
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86 | adns-maint@chiark.greenend.org.uk. |
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87 | |
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88 | Mailinglists |
89 | |
90 | I have set up mailinglists adns-announce and adns-discuss. The |
91 | announcements list is moderated and will contain only announcements of |
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92 | important bugs, new versions, etc. The bug reports address mentioned |
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93 | above is also a mailing list; feel free to subscribe to it. |
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94 | |
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95 | There are [3]archives and subscription web pages, or you can subscribe |
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96 | by sending mail containing the word `subscribe' to |
97 | adns-announce-REQUEST@chiark.greenend.org.uk or |
98 | adns-discuss-REQUEST@chiark.greenend.org.uk. |
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99 | |
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100 | Download |
101 | |
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102 | Available for download from [4]chiark.greenend.org.uk are: |
103 | * The [5]current release as a gzipped tarfile. |
104 | * [6]adns.h API header file with comments, and [7]usage message for |
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105 | adnshost (currently there is no manual, sorry). |
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106 | * All versions released so far are also available via [8]anonymous |
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107 | FTP and [9]HTTP. |
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108 | |
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109 | You can also access the project CVS repositories: |
110 | * A mirror of the source code repository is available via rsync from |
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111 | rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns (use FTP |
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112 | first to find your way around), or via [10]cvsweb. |
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113 | * This web page is maintained in [11]Savannah, where you can browse |
114 | the [12]webpage CVS. |
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115 | |
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116 | adns is also available from the [13]GNU Project FTP servers and their |
117 | [14]mirrors. |
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118 | |
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119 | Technical note |
120 | |
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121 | adns requires a real nameserver like [15]BIND or [16]Dents running on |
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122 | the same system or a nearby one, which must be willing to provide |
123 | `recursive service'. I.e., adns is a `stub resolver'. All properly |
124 | configured UN*X and GNU systems will already have such nameserver(s); |
125 | they are usually listed in /etc/resolv.conf. |
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126 | |
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127 | References and related projects |
128 | |
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129 | * [17]Python bindings by Andy Dustman. |
130 | * [18]Haskell bindings by Peter Simons. |
131 | * [19]liboop event loop library (by Dan Egnor) has a built-in |
132 | binding for adns. |
133 | * [20]port to MS Visual Studio 6 C++ by Jarle Aase. |
134 | |
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135 | Copyright and licensing |
136 | |
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137 | adns is Copyright 1997-2000,2003,2006 Ian Jackson, Copyright |
138 | 1999-2000,2003,2006 Tony Finch, and Copyright (C) 1991 Massachusetts |
139 | Institute of Technology. |
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140 | |
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141 | adns is free software; you can redistribute it and/or modify it under |
142 | the terms of the GNU General Public License as published by the Free |
143 | Software Foundation; either version 2 of the License, or (at your |
144 | option) any later version. |
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145 | |
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146 | This program and documentation is distributed in the hope that it will |
147 | be useful, but without any warranty; without even the implied warranty |
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148 | of merchantability or fitness for a particular purpose. See the |
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149 | [21]GNU General Public License for more details. |
150 | |
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151 | You should have received a copy of the GNU General Public License |
152 | along with adns, or one should be available above; if not, write to |
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153 | the [22]Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
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154 | MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. |
155 | _________________________________________________________________ |
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156 | |
157 | [23]Ian Jackson / [24]adns-maint@chiark.greenend.org.uk; more [25]free |
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158 | software by me. |
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159 | |
160 | [26]GNU home page; [27]chiark home page; [28]site or mirror home page |
161 | |
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162 | This web page is Copyright (C)1996-2005 Ian Jackson. See the |
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163 | [29]Copyright/acknowledgements. |
164 | |
165 | Use any browser - [30]Campaign for a non-browser-specific WWW |
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166 | |
167 | References |
168 | |
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169 | 1. http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt |
170 | 2. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt |
171 | 3. http://www.chiark.greenend.org.uk/mailman/listinfo |
172 | 4. http://www.chiark.greenend.org.uk/~ian/adns/ |
173 | 5. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz |
174 | 6. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt |
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175 | 7. http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt |
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176 | 8. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/ |
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177 | 9. http://www.chiark.greenend.org.uk/~ian/adns/ftp/ |
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178 | 10. http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/ |
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179 | 11. http://savannah.gnu.org/ |
180 | 12. http://savannah.gnu.org/cgi-bin/viewcvs/software/adns/?cvsroot=www.gnu.org |
181 | 13. http://www.gnu.org/ |
182 | 14. http://www.gnu.org/order/ftp.html |
183 | 15. http://www.isc.org/view.cgi?/products/BIND/index.phtml |
184 | 16. http://www.dents.org/ |
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185 | 17. http://dustman.net/andy/python/adns-python |
186 | 18. http://cryp.to/hsdns/ |
187 | 19. http://liboop.ofb.net/ref |
188 | 20. http://adns.jgaa.com/ |
189 | 21. http://www.chiark.greenend.org.uk/~ian/COPYING.txt |
190 | 22. http://www.fsf.org/ |
191 | 23. http://www.chiark.greenend.org.uk/ |
192 | 24. mailto:adns-maint@chiark.greenend.org.uk |
193 | 25. http://www.chiark.greenend.org.uk/~ian/software/ |
194 | 26. http://www.gnu.org/ |
195 | 27. http://www.chiark.greenend.org.uk/ |
196 | 28. file://localhost/ |
197 | 29. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html |
198 | 30. http://www.anybrowser.org/campaign/ |