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News

2003-09-19 Version 1.1.8b1-par7 has been released. Latest "maintenance" release by Paul Rombouts. Besides fixing a number of bugs I have reworked some of the code for adding and removing entries in the cache in an effort to improve efficiency and stability.
More details can be found in the ChangeLog.
2003-07-28 Version 1.1.8b1-par6 has been released. "maintenance" release by Paul Rombouts. In addition to some further code cleanup, the documentation has been revised.
2003-07-10 Version 1.1.8b1-par5 has been released. A troublesome allocation size error has been discovered in Thomas Moestl's code. In practice this bug only wastes memory but it could also potentially lead to memory corruption. Upgrading is recommended. More details can be found in the ChangeLog.
2003-06-30 Version 1.1.8b1-par4 has been released. Due to incompatibilities between various implementations of the pthread library on Linux systems, problems can occur with signal handling in pdnsd. The usual symptom is failure by pdnsd to save the cache to disk, and /var/cache/pdnsd/pdnsd.cache remaining empty. If you experience this kind of trouble, try reconfiguring with different values for the new --with-thread-lib option. The allowable values are described in the documentation.
2003-04-07 pdnsd is no longer maintained by Thomas Moestl: I have not had time to maintain pdnsd for quite a while now, and have been very slow to respond to issues, or did not respond at all. It is time that I officially announce that pdnsd is no longer actively maintained; I apologize to all those who reported bugs or asked questions without receiving any reply. However, Paul A. Rombouts has published a patch set against the last released version at http://www.phys.uu.nl/~rombouts/pdnsd.html, which cleans up a lot of code fixes many bugs.
2002-07-19 Documentation update. Please note that pdnsd should never be installed with setuid or setgid attributes, as it is not always possible to give up all privileges due to operating system restrictions. While this was never intended and I don't think that anybody would actually do this, the documentation was updated to explicitely mention this to avoid misunderstandings.
2002-01-15 Version 1.1.7a has been released. This fixes a reversed test in an assertion that would cause pdnsd to termintate when the ping uptest was used. No other changes were made.
2002-01-15 Version 1.1.7 has been released. This fixes some problems that might be remotely exploitable to gain access as the user pdnsd runs as (an unprivileged user by default). To do this, an attacker needs to control a name server that is queried by pdnsd, and send a malicious reply to such a query.
Upgrading is strongly recommended!
There are also minor bug fixes and stability improvements.

About pdnsd

pdnsd is a proxy dns server with permanent caching (the cache contents are written to hard disk on exit) that is designed to cope with unreacheable or down dns servers (for example in dial-in networking).
Since version 1.1.0, pdnsd supports negative cacheing.

It is licensed under the GNU General Public License (GPL, also available in html and translated into various languages.). This, in short, means that the sources are distributed togehter with the program, and that you are free to modify the sources and redistribute them as long as you also license them under the GPL. You do not need to pay anything for pdnsd. It also means that there is ABSOLUTELY NO WARRANTY for pdnsd or any part of it. For details, please read the GPL.

pdnsd can be used with applications that do dns lookups, eg on startup, and can't be configured to change that behaviour, to prevent the often minute-long hangs (or even crashes) that result from stalled dns queries. Some Netscape Navigator versions for Unix, for example, expose this behaviour.

pdnsd is configurable via a file and supports run-time configuration using the program pdnsd-ctl that comes with pdnsd. This allows you to set the status flags of servers that pdnsd knows (to influence which servers pdnsd will query), and the addition, deletion and invalidation of DNS records in pdnsd's cache.
Parallel name server queries are supported. This is a technique that allows querying several servers at the same time so that very slow or unavailable servers will not block the answer for one timeout interval.
Since version 1.0.0, pdnsd has full IPv6 support.

There is also a limited support for local zone records, intended for defining 1.0.0.127.in-addr.arpa. and localhost. , since some clients request that information and it must be served even if the cached servers are not available or do not serve these records. pdnsd may also read your /etc/hosts file (this file is normally used by your local resolver and usually contains information for localhost as well as for your machines FQDN) and serve its contents.

pdnsd was started on Linux, and has since been ported to FreeBSD. 90% of the source code should be easily portable to POSIX- and BSD-compatible systems, provided that those systems support the POSIX threads (pthreads). The rest might need OS-specific rewrites.

Currently, pdnsd is only compileable by gcc. This should be easy to fix, but I just do not have documentation for other compilers. If you are not able or do not want to use gcc, I would recommend you just try to do the minor changes.

pdnsd must be started as root in some cases (raw sockets are needed for icmp echoes for the option uptest=ping, and the default port is 53, this must be >1024 to allow non-root execution). However, pdnsd can be configured to change it's user and group id to those of a non-privileged user after opening the sockets needed for this.

The server should support the full standard dns queries following the rfcs 1034 and 1035. As of version 1.0.0, the rfc compliance has been improved again, and pdnsd is now believed (or hoped?) to be fully rfc-compatible. It completely follows rfc 2181 (except for one minor issue in the FreeBSD port, see the documentation). It does not support the following features, of which most are marked optional, experimental or obsolete in these rfcs:

The following record types, that are extensions to the original DNS standard, are supported for caching at a compile time option (if you do not need them, you do not need to compile support for them into pdnsd and save cache and executable space): There are FreeBSD and OpenBSD ports available for pdnsd (ports/net/pdnsd for both). Thanks go to Roman Shterenzon for the FreeBSD port Sebastian Stark for the OpenBSD one!

If you have questions left, you should take a look into the FAQ.
Bugfixes, patches and compatability fixes for other OSs are very welcome!

Features in detail

This section describes some of pdnsds features in detail. Most of the options are set in the config file. For more information on the configuration file, see the documenation page.


Uptests

pdnsd provides several methods to test whether a remote dns server should be regarded available (so that pdnsd can query it), in addition to the obvious "p.d." definition (the server is always regarded available). These tests are:

Local Records ("Zones")

As mentioned above, there are only very basic local record types (ie the record types that you may use in record declarations in your local configuration for records that pdnsd shall serve in addion to the cached ones). They are organized roughly in zones but have not complete zone declarations, so I generally do not use the term "zone" for them, but rather "local records". These are the local record types pdnsd can understand: You can specify these records in the configuration file.
You may "source" a file in a format like that used in the /etc/hosts file, that means that pdnsd reads this file, extracts addresses and domain names from it and automatically generates A records for name to address mapping, PTR records for address to name mapping and NS records (name server specifiation) for each entry in the file.
Records can also be changed dynamically at run time.
A script contributed by Marko Stolle makes pdnsd usable in a DHCP setup using this feature.

System requirements

As mentioned, pdnsd currently runs under Linux and FreeBSD. Other BSD flavours may or may not work (feedback is very welcome!). The system and software requirements under Linux are: The system requirements under FreeBSD are: The common software requirements for all supported systems are:

Download

If you want to download pdnsd, please visit the download page.

Authors

pdnsd was written by Thomas Moestl <tmoestl@gmx.net>
Note added by Paul Rombouts: I have revised the code and added a few new features. See README.par and the ChangeLog in the source directory (or /usr/share/doc/pdnsd-<version> if you have installed an RPM) for more details. If you have questions about my modifications, you can find my email address at the end of README.par.

Daniel Smolik has contributed RedHat RPM's.
Torben Janssen contributed start scripts for Red Hat Linux.
Soenke J. Peters contributed patches and suggestions for Red Hat compatability.
Wolfgang Ocker has contributed the code and documentation for the server_ip option.
Markus Mohr contributed a Debian rc script.
Nikita V. Youschenko contributed extensions to the "if" uptest.
Lyonel Vincent extended the serve_aliases option to support an arbitrary number of aliases.
Sourav K. Mandal wrote the autoconf scripts and contributed many fixes and suggestions.
Stephan Boettcher contributed the SCHEME= option.
Ron Yorston contributed the uptest for Linux ppp dial-on-demand devices.
Alexandre Nunes fixed some bugs in the autoconf files.
Sverker Wiberg contributed fixes for IPv6.
Carsten Block contributed configure-able rc scripts.
Olaf Kirch contributed a security fix for the run_as code.
Paul Wagland contributed various patches for bind9-compatability and other issues.
Roman Shterenzon contributed patches and lots of helpful hints for FreeBSD compatability.
Bernd Leibing has contributed spec file fixes.
Michael Wiedmann has contributed the pdnsd-ctl.8 man page.
Marko Stolle has contributed the contrib/pdnsd_update.pl script that makes pdnsd usable in a DHCP setup.
P.J. Bostley has contributed patches to get pdnsd working on alpha properly.
Christian Engstler contributed patches for SuSE compatability.
Bjoern Fischer contributed code to make pdnsd leave the case of names in the cache unchanged.
Marko Stolle contributed the contrib/pdnsd_update.pl script that makes pdnsd usable in a DHCP setup.
Andrew M. Bishop contributed the support for the label server option and the pdnsd-ctl interface for using it.
Frank Elsner contributed rc script fixes.
Andreas Steinmetz contributed the code for query_port_start and query_port_end options.

Special thanks to Bert Frederiks for letting me do a late-night debugging run on his machine to spot obscure bugs!

Thanks to the following persons for reporting bugs and being helpful:
Kevin A. Burton,
Joachim Dorner,
Stefan Erhardt,
Mike Hammer,
Jonathan Hudson,
Byrial Jensen,
Patrick Loschmidt,
James MacLean,
Fraser McCrossan,
Michael Müller,
Erich Reitz,
Brian Schroeder,
Milan P. Stanic,
Michael Steiner,
Norbert Steinl,
Markus Storm,
Michael Ströder,
Alan Swanson,
Eelco Vriezekolk

Links

Well, this is the obligatory link section.

http://www.gnu.org
The GNU homepage
http://freshmeat.net
freshmeat - huge free software index
http://www.freebsd.org
The FreeBSD project


Thomas Moestl

Last revised: 19 Sep 2003 by Paul Rombouts