Copyright 2004 Lennart Poettering <@PACKAGE_BUGREPORT@>
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.
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.
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.
Version 0.2 released. Changes include: send mDNS queries on every interface that supports multicasts, instead of only the one with the default route, making nss-mdns more robust on multi-homed hosts; gcc 2.95 compatiblity.
Version 0.1 released
nss-mdns is a plugin for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc) providing host name resolution via Multicast DNS (aka Zeroconf, aka Apple Rendezvous), effectively allowing name resolution by common Unix/Linux programs in the ad-hoc mDNS domain .local.
nss-mdns provides client functionality only, which means that you have to run a mDNS responder daemon seperately from nss-mdns if you want to register the local host name via mDNS (e.g. HOWL).
nss-mdns is very lightweight (22 KByte stripped binary .so compiled with -DNDEBUG=1 on i386, gcc 3.3), has no dependencies besides the glibc and requires only minimal configuration.
It works!
While nss-mdns supports resolving IPv6 addresses it does so via IPv4 multicasts only.
After compiling and installing nss-mdns you'll find three new NSS modules in /lib:
libnss_mdns.so.2 resolves both IPv6 and IPv4 addresses, libnss_mdns4.so.2 only IPv4 addresses and libnss_mdns6.so.2 only IPv6 addresses. Due to the fact that most mDNS responders only register local IPv4 addresses via mDNS, most people will want to use libnss_mdns4.so.2 exclusively. Using libnss_mdns.so.2 or libnss_mdns6.so.2 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.
To activate one of the NSS modules you have to edit /etc/nsswitch.conf and add mdns4 (resp. mdns, mdns6) to the line starting with "hosts:". On Debian this looks like this:
# /etc/nsswitch.conf passwd: compat group: compat shadow: compat hosts: files dns mdns4 networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis
That's it. You should now be able to resolve hosts from the .local domain with all your applications. For a quick check use glibc's getent tool:
$ getent hosts foo.local 192.168.50.4 foo.local
Replace foo whith a host name that has been registered with an mDNS responder.
Due to some traffic suppression algorithms in mDNS responders repeated mDNS resolutions are slowed down. Consider installing glibc's name service cache daemon nscd to work around this limitation.
When doing troubleshooting for nss-mdns, don't forget to disable nscd for getting sensible results.
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 224.0.0.251.
Currently, nss-mdns is tested on Linux only. A fairly modern glibc installation with development headers (2.0 or newer) is required. Not suprisingly nss-mdns requires a kernel compiled with IPv4 multicasting support enabled.
nss-mdns 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. nss-mdns has been tested exclusively against the HOWL mDNS responder daemon.
As this package is made with the GNU autotools you should run ./configure inside the distribution directory for configuring the source tree. After that you should run make for compilation and make install (as root) for installation of nss-mdns.
Nothing here yet.
The newest release is always available from @PACKAGE_URL@
The current release is @PACKAGE_VERSION@
Get nss-mdns's development sources from the Subversion repository (viewcvs):
svn checkout svn://seth.intheinter.net/nss-mdns/trunk nss-mdns
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