| 1 | |
| 2 | GNU adns |
| 3 | |
| 4 | Advanced, easy to use, asynchronous-capable DNS client library and |
| 5 | utilities. |
| 6 | |
| 7 | adns is a resolver library for C (and C++) programs, and a collection |
| 8 | of useful DNS resolver utilities. |
| 9 | |
| 10 | C library |
| 11 | |
| 12 | In contrast with the standard interfaces, gethostbyname et al and |
| 13 | libresolv, it has the following features: |
| 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 |
| 25 | an easy-to-use form, without getting in the way. |
| 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 |
| 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. |
| 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. |
| 41 | |
| 42 | DNS utility programs |
| 43 | |
| 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 |
| 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 |
| 55 | can invoke and communicate with subprocesses. See the [1]adnshost |
| 56 | usage message for a summary of its capabilities. |
| 57 | |
| 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. |
| 69 | |
| 70 | Documentation |
| 71 | |
| 72 | I'm afraid there is no manual yet. However, competent C programmers |
| 73 | should be able to use the library based on the [2]commented adns.h |
| 74 | header file, and the usage messages for the programs should be |
| 75 | sufficient. |
| 76 | |
| 77 | Feedback |
| 78 | |
| 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. |
| 81 | |
| 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 |
| 86 | adns-maint@chiark.greenend.org.uk. |
| 87 | |
| 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 |
| 92 | important bugs, new versions, etc. The bug reports address mentioned |
| 93 | above is also a mailing list; feel free to subscribe to it. |
| 94 | |
| 95 | There are [3]archives and subscription web pages, or you can subscribe |
| 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. |
| 99 | |
| 100 | Download |
| 101 | |
| 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 |
| 105 | adnshost (currently there is no manual, sorry). |
| 106 | * All versions released so far are also available via [8]anonymous |
| 107 | FTP and [9]HTTP. |
| 108 | |
| 109 | You can also access the project CVS repositories: |
| 110 | * A mirror of the source code repository is available via rsync from |
| 111 | rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns (use FTP |
| 112 | first to find your way around), or via [10]cvsweb. |
| 113 | * This web page is maintained in [11]Savannah, where you can browse |
| 114 | the [12]webpage CVS. |
| 115 | |
| 116 | adns is also available from the [13]GNU Project FTP servers and their |
| 117 | [14]mirrors. |
| 118 | |
| 119 | Technical note |
| 120 | |
| 121 | adns requires a real nameserver like [15]BIND or [16]Dents running on |
| 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. |
| 126 | |
| 127 | References and related projects |
| 128 | |
| 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 | |
| 135 | Copyright and licensing |
| 136 | |
| 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. |
| 140 | |
| 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. |
| 145 | |
| 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 |
| 148 | of merchantability or fitness for a particular purpose. See the |
| 149 | [21]GNU General Public License for more details. |
| 150 | |
| 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 |
| 153 | the [22]Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
| 154 | MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. |
| 155 | _________________________________________________________________ |
| 156 | |
| 157 | [23]Ian Jackson / [24]adns-maint@chiark.greenend.org.uk; more [25]free |
| 158 | software by me. |
| 159 | |
| 160 | [26]GNU home page; [27]chiark home page; [28]site or mirror home page |
| 161 | |
| 162 | This web page is Copyright (C)1996-2005 Ian Jackson. See the |
| 163 | [29]Copyright/acknowledgements. |
| 164 | |
| 165 | Use any browser - [30]Campaign for a non-browser-specific WWW |
| 166 | |
| 167 | References |
| 168 | |
| 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 |
| 175 | 7. http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt |
| 176 | 8. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/ |
| 177 | 9. http://www.chiark.greenend.org.uk/~ian/adns/ftp/ |
| 178 | 10. http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/ |
| 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/ |
| 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/ |