| 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 | Documentation |
| 59 | |
| 60 | I'm afraid there is no manual yet. However, competent C programmers |
| 61 | should be able to use the library based on the [2]commented adns.h |
| 62 | header file, and the usage messages for the programs should be |
| 63 | sufficient. |
| 64 | |
| 65 | Feedback |
| 66 | |
| 67 | I'd be pleased if you would let me know if you're using my library in |
| 68 | your project, and what you think of it. |
| 69 | |
| 70 | If you are subscribed to adns-discuss please send feedback, including |
| 71 | bug reports, there; otherwise send mail to |
| 72 | adns-bugreports@chiark.greenend.org.uk. If you'd prefer that your |
| 73 | message wasn't forwarded to the adns-bugreports list, send it to |
| 74 | adns-maint@chiark.greenend.org.uk. |
| 75 | |
| 76 | Mailinglists |
| 77 | |
| 78 | I have set up mailinglists adns-announce and adns-discuss. The |
| 79 | announcements list is moderated and will contain only announcements of |
| 80 | important bugs, new versions, etc. The bug reports address mentioned |
| 81 | above is also a mailing list; feel free to subscribe to it. |
| 82 | |
| 83 | There are [3]archives and subscription web pages, or you can subscribe |
| 84 | by sending mail containing the word `subscribe' to |
| 85 | adns-announce-REQUEST@chiark.greenend.org.uk or |
| 86 | adns-discuss-REQUEST@chiark.greenend.org.uk. |
| 87 | |
| 88 | Download |
| 89 | |
| 90 | Available for download from [4]chiark.greenend.org.uk are: |
| 91 | * The [5]current release as a gzipped tarfile. |
| 92 | * [6]adns.h API header file with comments, and [7]usage message for |
| 93 | adnshost (currently there is no manual, sorry). |
| 94 | * All versions released so far are also available via [8]anonymous |
| 95 | FTP and [9]HTTP, |
| 96 | * A mirror of my CVS repository is available via rsync from |
| 97 | rsync.chiark.greenend.org.uk::ftp/users/ian/cvs-pub/adns (use FTP |
| 98 | first to find your way around), or via [10]cvsweb. |
| 99 | |
| 100 | adns is also available from the [11]GNU Project FTP servers and their |
| 101 | [12]mirrors. |
| 102 | |
| 103 | Technical note |
| 104 | |
| 105 | adns requires a real nameserver like [13]BIND or [14]Dents running on |
| 106 | the same system or a nearby one, which must be willing to provide |
| 107 | `recursive service'. I.e., adns is a `stub resolver'. All properly |
| 108 | configured UN*X and GNU systems will already have such nameserver(s); |
| 109 | they are usually listed in /etc/resolv.conf. |
| 110 | |
| 111 | Copyright and licensing |
| 112 | |
| 113 | adns is Copyright 1997-2000 Ian Jackson, Copyright 1999-2000 Tony |
| 114 | Finch, and Copyright (C) 1991 Massachusetts Institute of Technology. |
| 115 | |
| 116 | adns is free software; you can redistribute it and/or modify it under |
| 117 | the terms of the GNU General Public License as published by the Free |
| 118 | Software Foundation; either version 2 of the License, or (at your |
| 119 | option) any later version. |
| 120 | |
| 121 | This program and documentation is distributed in the hope that it will |
| 122 | be useful, but without any warranty; without even the implied warranty |
| 123 | of merchantability or fitness for a particular purpose. See the |
| 124 | [15]GNU General Public License for more details. |
| 125 | |
| 126 | You should have received a copy of the GNU General Public License |
| 127 | along with adns, or one should be available above; if not, write to |
| 128 | the [16]Free Software Foundation, 59 Temple Place - Suite 330, Boston, |
| 129 | MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk. |
| 130 | _________________________________________________________________ |
| 131 | |
| 132 | [17]Ian Jackson / [18]adns-maint@chiark.greenend.org.uk; more [19]free |
| 133 | software by me. |
| 134 | |
| 135 | [20]GNU home page; [21]chiark home page; [22]site or mirror home page |
| 136 | |
| 137 | This web page is Copyright (C)1996-2000 Ian Jackson. See the |
| 138 | [23]Copyright/acknowledgements. |
| 139 | |
| 140 | Use any browser - [24]Campaign for a non-browser-specific WWW |
| 141 | |
| 142 | References |
| 143 | |
| 144 | 1. http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt |
| 145 | 2. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt |
| 146 | 3. http://www.chiark.greenend.org.uk/mailman/listinfo |
| 147 | 4. http://www.chiark.greenend.org.uk/~ian/adns/ |
| 148 | 5. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz |
| 149 | 6. http://www.chiark.greenend.org.uk/~ian/adns/adns.h.txt |
| 150 | 7. http://www.chiark.greenend.org.uk/~ian/adns/adnshost.txt |
| 151 | 8. ftp://ftp.chiark.greenend.org.uk/users/ian/adns/ |
| 152 | 9. http://www.chiark.greenend.org.uk/~ian/adns/ftp/ |
| 153 | 10. http://www.chiark.greenend.org.uk/ucgi/~ijackson/cvsweb/adns/ |
| 154 | 11. http://www.gnu.org/ |
| 155 | 12. http://www.gnu.org/order/ftp.html |
| 156 | 13. http://www.isc.org/view.cgi?/products/BIND/index.phtml |
| 157 | 14. http://www.dents.org/ |
| 158 | 15. http://www.chiark.greenend.org.uk/~ian/COPYING.txt |
| 159 | 16. http://www.fsf.org/ |
| 160 | 17. http://www.chiark.greenend.org.uk/ |
| 161 | 18. mailto:adns-maint@chiark.greenend.org.uk |
| 162 | 19. http://www.chiark.greenend.org.uk/~ian/software/ |
| 163 | 20. http://www.gnu.org/ |
| 164 | 21. http://www.chiark.greenend.org.uk/ |
| 165 | 22. file://localhost/ |
| 166 | 23. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html |
| 167 | 24. http://www.anybrowser.org/campaign/ |