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<?xml version="1.0" encoding="iso-8859-1"?> <!-- -*-html-helper-*- -->
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<title>nss-mdns @PACKAGE_VERSION@</title>
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<h1><a name="top">nss-mdns @PACKAGE_VERSION@</a></h1>
<p><i>Copyright 2004 Lennart Poettering <@PACKAGE_BUGREPORT@></i></p>
<ul class="toc">
<li><a href="#license">License</a></li>
<li><a href="#news">News</a></li>
<li><a href="#overview">Overview</a></li>
<li><a href="#status">Status</a></li>
<li><a href="#documentation">Documentation</a></li>
<li><a href="#requirements">Requirements</a></li>
<li><a href="#installation">Installation</a></li>
<li><a href="#acks">Acknowledgements</a></li>
<li><a href="#download">Download</a></li>
</ul>
<h2><a name="license">License</a></h2>
<p>This program is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.</p>
<p>This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.</p>
<p>You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.</p>
<h2><a name="news">News</a></h2>
<div class="news-date">Fri Dec 17 2004: </div> <p class="news-text"><a
href="@PACKAGE_URL@nss-mdns-0.2.tar.gz">Version 0.2</a>
released. Changes include: send mDNS queries on every interface that
supports multicasts, instead of only the one with the default route,
making <tt>nss-mdns</tt> more robust on multi-homed hosts; gcc 2.95
compatiblity.</p>
<div class="news-date">Mon Dec 6 2004: </div> <p class="news-text"><a
href="@PACKAGE_URL@nss-mdns-0.1.tar.gz">Version 0.1</a> released</p>
<h2><a name="overview">Overview</a></h2>
<p><tt>nss-mdns</tt> is a plugin for the GNU Name Service
Switch (NSS) functionality of the GNU C Library (<tt>glibc</tt>)
providing host name resolution via <a
href="http://www.multicastdns.org/">Multicast DNS</a> (aka
<i>Zeroconf</i>, aka <i>Apple Rendezvous</i>), effectively allowing
name resolution by common Unix/Linux programs in the ad-hoc mDNS domain <tt>.local</tt>.</p>
<p><tt>nss-mdns</tt> provides client functionality only, which
means that you have to run a mDNS responder daemon seperately
from <tt>nss-mdns</tt> if you want to register the local host name via
mDNS (e.g. <a href="http://www.porchdogsoft.com/products/howl/">HOWL</a>).</p>
<p><tt>nss-mdns</tt> is very lightweight (22 KByte stripped binary <tt>.so</tt> compiled with
<tt>-DNDEBUG=1</tt> on i386, <tt>gcc</tt> 3.3), has no dependencies besides the <tt>glibc</tt> and requires only minimal
configuration.</p>
<h2><a name="status">Status</a></h2>
<p>It works!</p>
<p>While <tt>nss-mdns</tt> supports resolving IPv6 addresses it does
so via IPv4 multicasts only.</p>
<h2><a name="documentation">Documentation</a></h2>
<p>After compiling and installing <tt>nss-mdns</tt> you'll find three
new NSS modules in <tt>/lib</tt>:</p>
<ul><li><tt>libnss_mdns.so.2</tt></li>
<li><tt>libnss_mdns4.so.2</tt></li>
<li><tt>libnss_mdns6.so.2</tt></li></ul> <p><tt>libnss_mdns.so.2</tt>
resolves both IPv6 and IPv4 addresses, <tt>libnss_mdns4.so.2</tt> only
IPv4 addresses and <tt>libnss_mdns6.so.2</tt> only IPv6 addresses. Due
to the fact that most mDNS responders only register local IPv4
addresses via mDNS, most people will want to use
<tt>libnss_mdns4.so.2</tt> exclusively. Using
<tt>libnss_mdns.so.2</tt> or <tt>libnss_mdns6.so.2</tt> in such a
situation causes long timeouts when resolving hosts since most modern
Unix/Linux applications check for IPv6 addresses first, followed by a
lookup for IPv4.</p>
<p>To activate one of the NSS modules you have to edit
<tt>/etc/nsswitch.conf</tt> and add <tt>mdns4</tt>
(resp. <tt>mdns</tt>, <tt>mdns6</tt>) to the line starting with "<tt>hosts:</tt>". On Debian this looks like this:</p>
<pre># /etc/nsswitch.conf
passwd: compat
group: compat
shadow: compat
hosts: files dns <b>mdns4</b>
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis</pre>
<p>That's it. You should now be able to resolve hosts from the
<tt>.local</tt> domain with all your applications. For a quick check
use <tt>glibc</tt>'s <tt>getent</tt> tool:
<pre>$ getent hosts <i>foo</i>.local
192.168.50.4 foo.local</pre>
<p>Replace <i>foo</i> whith a host name that has been registered with an mDNS responder.</p>
<p>Due to some traffic suppression algorithms in mDNS responders
repeated mDNS resolutions are slowed down. Consider installing <tt>glibc</tt>'s name
service cache daemon <tt>nscd</tt> to work around this limitation.</p>
<p>When doing troubleshooting for <tt>nss-mdns</tt>, don't forget to
disable <tt>nscd</tt> for getting sensible results.</p>
<p>If you run a firewall, don't forget to allow UDP traffic from and to port 5353
from and to the the mDNS multicast address <tt>224.0.0.251</tt>.</p>
<h2><a name="requirements">Requirements</a></h2>
<p>Currently, <tt>nss-mdns</tt> is tested on Linux only. A fairly modern <tt>glibc</tt> installation with development headers (2.0 or newer) is required. Not
suprisingly <tt>nss-mdns</tt> requires a kernel compiled with IPv4
multicasting support enabled.</p>
<p><tt>nss-mdns</tt> was developed and tested on Debian GNU/Linux
"testing" from December 2004, it should work on most other Linux
distributions (and maybe Unix versions) since it uses GNU autoconf and
GNU libtool for source code configuration and shared library
management. <tt>nss-mdns</tt> has been tested exclusively against the
HOWL mDNS responder daemon.</p>
<h2><a name="installation">Installation</a></h2>
<p>As this package is made with the GNU autotools you should run
<tt>./configure</tt> inside the distribution directory for configuring
the source tree. After that you should run <tt>make</tt> for
compilation and <tt>make install</tt> (as root) for installation of
<tt>nss-mdns</tt>.</p>
<h2><a name="acks">Acknowledgements</a></h2>
<p>Nothing here yet.</p>
<h2><a name="download">Download</a></h2>
<p>The newest release is always available from <a href="@PACKAGE_URL@">@PACKAGE_URL@</a></p>
<p>The current release is <a href="@PACKAGE_URL@nss-mdns-@PACKAGE_VERSION@.tar.gz">@PACKAGE_VERSION@</a></p>
<p>Get <tt>nss-mdns</tt>'s development sources from the <a href="http://subversion.tigris.org/">Subversion</a> <a href="svn://seth.intheinter.net/nss-mdns">repository</a> (<a href="http://0pointer.de/cgi-bin/viewcvs.cgi/?root=nss-mdns">viewcvs</a>): </p>
<pre>svn checkout svn://seth.intheinter.net/nss-mdns/trunk nss-mdns</pre>
<p>If you want to be notified whenever I release a new version of this software use the subscription feature of <a href="http://freshmeat.net/projects/nss-mdns/">Freshmeat</a>.</p>
<hr/>
<address class="grey">Lennart Poettering <@PACKAGE_BUGREPORT@>, December 2004</address>
<div class="grey"><i>$Id$</i></div>
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