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