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    1 
    2                                  nss-mdns 0.10
    3 
    4    Copyright 2004-2007 Lennart Poettering <mzaffzqaf (at) 0pointer (dot)
    5    de>
    6      * [1]License
    7      * [2]News
    8      * [3]Overview
    9      * [4]Current Status
   10      * [5]Documentation
   11      * [6]Requirements
   12      * [7]Installation
   13      * [8]Acknowledgements
   14      * [9]Download
   15 
   16 License
   17 
   18    This program is free software; you can redistribute it and/or modify
   19    it under the terms of the GNU Lesser General Public License as
   20    published by the Free Software Foundation; either version 2 of the
   21    License, or (at your option) any later version.
   22 
   23    This program is distributed in the hope that it will be useful, but
   24    WITHOUT ANY WARRANTY; without even the implied warranty of
   25    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   26    Lesser General Public License for more details.
   27 
   28    You should have received a copy of the GNU Lesser General Public
   29    License along with this program; if not, write to the Free Software
   30    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   31 
   32 News
   33 
   34    Sat May 12 2007:
   35 
   36    [10]Version 0.10 released. Changes include: Ported to FreeBSD;
   37    alignment fixes for SPARC.
   38 
   39    Mon Jan 1 2007:
   40 
   41    [11]Version 0.9 released. Changes include: Make most shared library
   42    symbols private to not conflict with any symbols of the program we're
   43    loaded into. Fix a potential endless loop in the mDNS packet parsing
   44    code.
   45 
   46    Please note that due to security reasons from this release on the
   47    minimal mDNS stack included in nss-mdns (dubbed "legacy") is no longer
   48    built by default. Thus, nss-mdns will not work unless [12]Avahi is
   49    running! That makes Avahi essentially a hard dependency of nss-mdns.
   50    Pass --enable-legacy to reenable the mini mDNS stack again. Please
   51    note as well that this release does not honour /etc/resolv.conf domain
   52    search lists by default anymore. It created a lot of problems and was
   53    never recommended anyway. You may reenable this functionality by
   54    passing --enable-search-domains.
   55 
   56    Sat Apr 29 2006:
   57 
   58    [13]Version 0.8 released. Changes include: Build time option to
   59    disable "legacy unicast" mDNS requests, i.e. resolve exclusively with
   60    Avahi; build a special _minimal flavour of the shared objects to
   61    minimize unnecessary name lookup timeouts; fix IPv6 resolving when
   62    using Avahi.
   63 
   64    Please note that starting with nss-mdns 0.8 we encourage you to use a
   65    different /etc/nsswitch.conf configuration line. See below for more
   66    information!
   67 
   68    Sat Nov 19 2005:
   69 
   70    [14]Version 0.7 released. Changes include: Portability patch for ARM
   71    from Philipp Zabel; make sure not to print any messages to STDERR;
   72    deal with OOM situations properly; if multiple addresses are assigned
   73    to the same interface make sure to send a query packet only once;
   74    other cleanups
   75 
   76    Sun Aug 21 2005:
   77 
   78    [15]Version 0.6 released. Changes include: honour search list in
   79    /etc/resolv.conf; try to contact [16]Avahi for resolving.
   80 
   81    Sat Jun 4 2005:
   82 
   83    [17]Version 0.5 released. Changes include: only lookup hostnames
   84    ending in .local; add support for a configuration file
   85    (/etc/mdns.allow) to allow lookups for other names.
   86 
   87    Sun May 15 2005:
   88 
   89    [18]Version 0.4 released. Changes include: small portability fix for
   90    big endian architectures; send "legacy unicast" packets instead of
   91    normal mDNS packets (this should reduce traffic and improve response
   92    time)
   93 
   94    Jan Sun 16 2005:
   95 
   96    [19]Version 0.3 released. Changes include: add Debianization; use
   97    ip6.arpa instead of ip6.int for reverse IPv6 lookups.
   98 
   99    Fri Dec 17 2004:
  100 
  101    [20]Version 0.2 released. Changes include: send mDNS queries on every
  102    interface that supports multicasts, instead of only the one with the
  103    default route, making nss-mdns more robust on multi-homed hosts; gcc
  104    2.95 compatiblity.
  105 
  106    Mon Dec 6 2004:
  107 
  108    [21]Version 0.1 released
  109 
  110 Overview
  111 
  112    nss-mdns is a plugin for the GNU Name Service Switch (NSS)
  113    functionality of the GNU C Library (glibc) providing host name
  114    resolution via [22]Multicast DNS (aka Zeroconf, aka Apple Rendezvous,
  115    aka Apple Bonjour), effectively allowing name resolution by common
  116    Unix/Linux programs in the ad-hoc mDNS domain .local.
  117 
  118    nss-mdns provides client functionality only, which means that you have
  119    to run a mDNS responder daemon seperately from nss-mdns if you want to
  120    register the local host name via mDNS. I recommend [23]Avahi.
  121 
  122    nss-mdns is very lightweight (9 KByte stripped binary .so compiled
  123    with -DNDEBUG=1 -Os on i386, gcc 4.0), has no dependencies besides the
  124    glibc and requires only minimal configuration.
  125 
  126    By default nss-mdns tries to contact a running [24]avahi-daemon for
  127    resolving host names and addresses and making use of its superior
  128    record cacheing. Optionally nss-mdns can be compiled with a mini mDNS
  129    stack that can be used to resolve host names without a local Avahi
  130    installation. Both Avahi support and this mini mDNS stack are
  131    optional, however at least one of them needs to be enabled. If both
  132    are enabled a connection to Avahi is tried first, and if that fails
  133    the mini mDNS stack is used.
  134 
  135 Current Status
  136 
  137    It works!
  138 
  139    If the mini MDNS stack is used, nss-mdns supports resolving IPv6
  140    addresses but does so via IPv4 multicasts only. If Avahi is used for
  141    resolving IPv6 is supported properly.
  142 
  143 Documentation
  144 
  145    After compiling and installing nss-mdns you'll find six new NSS
  146    modules in /lib:
  147      * libnss_mdns.so.2
  148      * libnss_mdns4.so.2
  149      * libnss_mdns6.so.2
  150      * libnss_mdns_minimal.so.2
  151      * libnss_mdns4_minimal.so.2
  152      * libnss_mdns6_minimal.so.2
  153 
  154    libnss_mdns.so.2 resolves both IPv6 and IPv4 addresses,
  155    libnss_mdns4.so.2 only IPv4 addresses and libnss_mdns6.so.2 only IPv6
  156    addresses. Due to the fact that most mDNS responders only register
  157    local IPv4 addresses via mDNS, most people will want to use
  158    libnss_mdns4.so.2 exclusively. Using libnss_mdns.so.2 or
  159    libnss_mdns6.so.2 in such a situation causes long timeouts when
  160    resolving hosts since most modern Unix/Linux applications check for
  161    IPv6 addresses first, followed by a lookup for IPv4.
  162 
  163    libnss_mdns{4,6,}_minimal.so (new in version 0.8) is mostly identical
  164    to the versions without _minimal. However, they differ in one way. The
  165    minimal versions will always deny to resolve host names that don't end
  166    in .local or addresses that aren't in the range 169.254.x.x (the range
  167    used by [25]IPV4LL/APIPA/RFC3927.) Combining the _minimal and the
  168    normal NSS modules allows us to make mDNS authoritative for Zeroconf
  169    host names and addresses (and thus creating no extra burden on DNS
  170    servers with always failing requests) and use it as fallback for
  171    everything else.
  172 
  173    To activate one of the NSS modules you have to edit /etc/nsswitch.conf
  174    and add mdns4 and mdns4_minimal (resp. mdns, mdns6) to the line
  175    starting with "hosts:". On Debian this looks like this:
  176 # /etc/nsswitch.conf
  177 
  178 passwd:         compat
  179 group:          compat
  180 shadow:         compat
  181 
  182 hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4
  183 networks:       files
  184 
  185 protocols:      db files
  186 services:       db files
  187 ethers:         db files
  188 rpc:            db files
  189 
  190 netgroup:       nis
  191 
  192    That's it. You should now be able to resolve hosts from the .local
  193    domain with all your applications. For a quick check use glibc's
  194    getent tool:
  195 $ getent hosts foo.local
  196 192.168.50.4    foo.local
  197 
  198    Replace foo whith a host name that has been registered with an mDNS
  199    responder. (Don't try to use the tools host or nslookup for these
  200    tests! They bypass the NSS and thus nss-mdns and issue their DNS
  201    queries directly.)
  202 
  203    If you run a firewall, don't forget to allow UDP traffic to the the
  204    mDNS multicast address 224.0.0.251 on port 5353.
  205 
  206    Please note: The line above makes nss-mdns authoritative for the
  207    .local domain. If you have a unicast DNS domain with the same name you
  208    will no longer be able to resolve hosts from it. mDNS and a unicast
  209    DNS domain named .local are inherently incompatible. Please contact
  210    your local admistrator and ask him to move to a different domain name
  211    since .local is to be used exclusively for Zeroconf technology.
  212    [26]Further information.
  213 
  214    Starting with version 0.5, nss-mdns has a simple configuration file
  215    /etc/mdns.allow for enabling name lookups via mDNS in other domains
  216    than .local. The file contains valid domain suffixes, seperated by
  217    newlines. Empty lines are ignored as are comments starting with #. To
  218    enable mDNS lookups of all names, regardless of the domain suffix add
  219    a line consisting of * only (similar to nss-mdns mode of operation of
  220    versions <= 0.4):
  221 # /etc/mdns.allow
  222 *
  223 
  224    If the configuration file is absent or unreadable nss-mdns behaves as
  225    if a configuration file with the following contents is read:
  226 # /etc/mdns.allow
  227 .local.
  228 .local
  229 
  230    i.e. only hostnames ending with .local are resolved via mDNS.
  231 
  232    If the configuration file is existent but empty, mDNS name lookups are
  233    disabled completely. Please note that usually mDNS is not used for
  234    anything but .local, hence you usually don't want to touch this file.
  235 
  236 Requirements
  237 
  238    Currently, nss-mdns is tested on Linux only. A fairly modern glibc
  239    installation with development headers (2.0 or newer) is required. Not
  240    suprisingly nss-mdns requires a kernel compiled with IPv4 multicasting
  241    support enabled. [27]Avahi is recommended for its superior cacheing
  242    capabilities and for security reasons. Unless you compile nss-mdns
  243    with --enable-legacy Avahi is a hard dependency when nss-mdns is used,
  244    however not a build-time requirement.
  245 
  246    nss-mdns was developed and tested on Debian GNU/Linux "testing" from
  247    December 2004, it should work on most other Linux distributions (and
  248    maybe Unix versions) since it uses GNU autoconf and GNU libtool for
  249    source code configuration and shared library management.
  250 
  251 Installation
  252 
  253    As this package is made with the GNU autotools you should run
  254    ./configure inside the distribution directory for configuring the
  255    source tree. After that you should run make for compilation and make
  256    install (as root) for installation of nss-mdns.
  257 
  258 Acknowledgements
  259 
  260    SHIROYAMA Takayuki, Anand Kumria and Bastien Nocera, Sjoerd Simons for
  261    patches.
  262 
  263    Sean Meiners for search list support.
  264 
  265    Philipp Zabel for ARM support.
  266 
  267    Bruce M Simpson for porting it to FreeBSD.
  268 
  269 Download
  270 
  271    The newest release is always available from
  272    [28]http://0pointer.de/lennart/projects/nss-mdns/
  273 
  274    The current release is [29]0.10
  275 
  276    Get nss-mdns's development sources from the [30]Subversion
  277    [31]repository ([32]viewcvs):
  278 svn checkout svn://svn.0pointer.de/nss-mdns/trunk nss-mdns
  279 
  280    You may find an up to date Debian package of nss-mdns on the
  281    [33]Debian package repository. Many other distributions ship it, too.
  282 
  283    If you want to be notified whenever I release a new version of this
  284    software use the subscription feature of [34]Freshmeat.
  285      _________________________________________________________________
  286 
  287 
  288     Lennart Poettering <mzaffzqaf (at) 0pointer (dot) de>, May 2007
  289 
  290    $Id: README.html.in 116 2007-05-12 14:54:24Z lennart $
  291 
  292 References
  293 
  294    1. README#license
  295    2. README#news
  296    3. README#overview
  297    4. README#status
  298    5. README#documentation
  299    6. README#requirements
  300    7. README#installation
  301    8. README#acks
  302    9. README#download
  303   10. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.10.tar.gz
  304   11. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.9.tar.gz
  305   12. http://avahi.org/
  306   13. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.8.tar.gz
  307   14. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.7.tar.gz
  308   15. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.6.tar.gz
  309   16. http://avahi.org/
  310   17. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.5.tar.gz
  311   18. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.4.tar.gz
  312   19. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.3.tar.gz
  313   20. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.2.tar.gz
  314   21. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.1.tar.gz
  315   22. http://www.multicastdns.org/
  316   23. http://avahi.org/
  317   24. http://avahi.org/
  318   25. http://files.zeroconf.org/rfc3927.txt
  319   26. http://avahi.org/wiki/AvahiAndUnicastDotLocal
  320   27. http://avahi.org/
  321   28. http://0pointer.de/lennart/projects/nss-mdns/
  322   29. http://0pointer.de/lennart/projects/nss-mdns/nss-mdns-0.10.tar.gz
  323   30. http://subversion.tigris.org/
  324   31. svn://svn.0pointer.de/nss-mdns
  325   32. http://0pointer.de/cgi-bin/viewcvs.cgi/?root=nss-mdns
  326   33. http://packages.debian.org/libnss-mdns
  327   34. http://freshmeat.net/projects/nss-mdns/