Lua binding to net-snmp library
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README

LuaSNMP 
=======


* LuaSNMP
  -------
  
  LuaSNMP is a binding to the netsnmp library.

  LuaSNMP is basically an update to the LuaMan library developed by
  Michele E. Lima and Ana Lucia de Moura (ana@telemidia.puc-rio.br).

  LuaSNMP requires the net-snmp library version 5.6 or later. The netsnmp library
  can be downloaded from 
          http://sourceforge.net/projects/net-snmp/
  See "* LuaSNMP under MS Windows" below for details on issues when using LuaSNMP
  with Microsoft Windows.

  You must have Lua version 5.1, 5.2 or 5.3 to use it.
  Lua can be downloaded from its home page:
	  http://www.tecgraf.puc-rio.br/lua/

* Documentation
  -------------

  The original LuaMan documentation (up to version 2.3) can be reached
  from its home page:
	  http://www.telemidia.puc-rio.br/~ana/luaman/
	
  An updated documentation comes with the LuaSNMP distribution in the doc
  sub-directory.
	

* Legal matters
  -------------

  LuaSNMP is licensed under the MIT license.


* Installation
  ------------

  Note, that the makefile configuration defines Lua 5.2 as the default Lua version.
  In order to build LuaSNMP for other Lua versions you either have to change
  the variables V and LV in the makefile configuration file config or specify
  the destined Lua version in the command line, e.g. make V=53 LV=5.3.

  In order to build LuaSNMP on a Linux, Unix or Cygwin/Mingw based
  POSIX like system:
  

  1. Make sure you have Lua (version 5.1 or later).

  2. LuaSNMP comes with a makefile and a simple config file to adopt
     the make process to your target system.

     Compiler Flags:

     USE_SNMPTRAPD
	Use the netsnmp standard utility snmptrapd as trap-sink daemon.
        See * Trap-sink Daemon below for details.

  3. Configure the make environment

     The file config adopts the make environment automatically to suit your
     platform.

  4. Compile the package

     Type 
	make or make LV=5.3 or make LV=5.1

     If make succeeds you get for Linux/MacOS (Windows):

     * a Lua extension library "snmp.so.1.0" (core.dll) in the src sub-directory.
     * a copy "core.so" (core.dll) of the same Lua extension library in ./snmp

  5. Type
       make install or make LV=5.3 install or make LV=5.1 install

     as user root in order to install all relevant
     files in standard places. The directory /usr/local is the default
     install prefix.


     
* Trap-sink Daemon
  ----------------
  LuaSNMP supports the following trap-sink daemons:

  snmptrapd 

     It is recommended to use this daemon, as it fully supports SNMP
     INFORM requests. Add the following line to your
     /etc/snmp/snmptrapd.conf file in order to get notified by 
     snmptrapd:

	  traphandle default PATH-TO-LUA/lua \
	             PATH-TO-LUASNMP/trapd.lua [TRAPDPORT] [LOGFILE] [LOGLEVEL]

     This instructs snmptrapd to execute the trapd.lua script, which will then
     in fact notify your luasnmp session about traps and informs using standard
     UDP datagrams on a user configurable port TRAPDPORT (6000 is used by default).
     
     Note, that 'trapd.lua' is a normal Lua script, that requires it's environment
     correctly set, which typically happens by inheritance of the environment of the
     shell that starts snmptrapd. In particular 'trapd.lua' requires the following
     standard environment variables (examples):

     For Lua 5.0:
     LUA_INIT=@/usr/local/share/lua/5.0/compat-5.1.lua
	Only required for Lua 5.0 as Lua 5.1 does not require compat-5.1.lua.

     For Lua 5.1:
     LUA_INIT="require 'luarocks.require'"
        Let Lua find modules installed via luarocks.

     LUA_PATH="./?.lua;./?/?.lua;/usr/local/share/lua/5.x/?.lua;/usr/local/share/lua/5.0/?/?.lua;/usr/local/share/lua/5.x/?/init.lua"
	Tell Lua where to find Lua modules (required). Note that luarocks path
	is not included here. With the corresponding setting of the LUA_INIT environment
	variable modules are first searched in the luarocks module repository and
	then inthe PATH given via LUA_PATH.

     LUA_CPATH="./?.so;./l?.so;/usr/local/lib/lua/5.0/?.so;/usr/local/lib/lua/5.0/l?.so"
	Tell Lua where to find C modules (required). See LUA_PATH concerning module
	search order when luarocks is installed.

     You may also want to write data from the last received trap into a logfile:
     just provide the full path of the logfile as second argument.

     The third argument defines the level of logging used. See module LuaLogging
     for details.     

     Note, that you have to set the compiler switch USE_SNMPTRAPD when
     you compile the luasnmp package.


* Trap log message format
  ---------------------
     In order to have the trapd.lua script work properly snmptrapfmt must be configured
     with the following format setting:
       SUBST=\#\ \
       NODEFMT=ip
       VARFMT="#[%s] %n (%t) : %v" 
       LOGFMT="$x#$A#$e#$G#$S#$T$*"
     This ensure that the log message can be interpreted by the trapd script.

* Environment Variables
  ---------------------

  The following environment variables are needed for using LuaSNMP:

  LUASNMP_TRAPDPORT: Defines the port number to use on UDB socket between
                        snmptrapd and the trapd.lua script.
  LUASNMP_TRAPDPORT: Defines the port used by trapd.lua to capture events
                     from NET-SNMP's snmptrapd.
  LUASNMP_MIBDIRS:   Directory to find extra MIBs for LuaSNMP usage. Same functionality as
                     the MIBDIRS environment variable of NET-SNMP.
  MIBDIRS:           LuaSNMP searches in the path given by MIBDIRS for MIBs.
  SNMPCONFPATH:      LuaSNMP respects the standard NET-SNMP configuration path variable.

  
* NetSNMP configuration files
  ---------------------------

  NetSNMP uses a bunch of configuration files at various places. Here is a list of them
  with some personal notes.

  /etc/snmp/snmpd.conf 	  Main agent configuration containing site specific agent definitions
  			  that do not contain any secrete information.
			  (Note, that the temmplate file provided violates this recommendation,
			  simply remove the createUser directives)
			  template: etc/snmpd.conf

  /var/lib/snmp/snmpd.conf	  Automatic generated configuration entries, mainly encrypted user
  				  information
			  	  template: none

  /usr/share/snmp/snmpd.conf	User specific configuration: which user is allowed to work
  				how on which part of the MIBtree (rwuser directive)
				template: etc/share_snmpd.conf

  /etc/snmp/snmp.conf	  Default User and Password. Eases SNMP3 commands.
  			  template: etc/etc_snmp.conf

  $(HOME)/.snmp/snmp.conf Defaults per user
  			  template: etc/snmp.conf

  
* SNMPv3 Considerations
  ---------------------

  Generally, LuaSNMP has the same prerequisits as the NetSNMP library to get 
  SNMP version 3 to work. Nevertheless, here are some useful hints to get the
  test script test.lua into operation for version 3.

  1. Copy the template configuration files:
     etc/snmpd.conf    		to     /etc/snmpd.conf
     etc/snmptrapd.conf		to     /etc/snmptrapd.conf
       You should adopt/select the line configuring the trapd.lua script execution
       to use the correct path to the Lua executable
     etc/snmp.conf              to     $(HOME)/.snmp/snmp.conf

  2. Stop the SNMP daemon.

  3. Create SNMP v3 users using the net-snmp-config command as follows:
     	    net-snmp-config --create-snmpv3-user -a "leuwer2006" leuwer
     	    net-snmp-config --create-snmpv3-user -a "ronja2006" ronja
     (The users shown are those used in test.lua.)

     This adds createUser directives to /var/lib/snmpd.conf which are replaced
     by encrypted keys during snmpd startup.
     
     If the way via net-snmp-config tool is missing or fails do it by hand and
     add the following into /var/lib/snmp/snmpd.conf

     createUser leuwer MD5 leuwer2006 DES leuwer2006
     createUser ronja  MD5 ronja2006 DES ronja2006

     You may choose SHA instead of MD5 and AES or AES128 instead of DES.    

  4. Create a file /usr/share/snmp/snmpd.conf and add the following lines
     rwuser leuwer
     rwuser ronja
     Note that the template named in 1) already contains these lines.

  5. Start the SNMP daemon

* LuaSNMP on MS Windows
  ---------------------

  - Compilation
	LuaSNMP does not compile against the development files that come with
    	the net-snmp installer package. It compiles without problems
	against the configured and installed net-snmp 5.3.0.1 source package.

  - Agents 
	The provided test script test.lua works fine against the net-snmp agent
	snmpd built under cygwin.
	Read requests work fine against Microsoft's SNMP agent. I have taken no
	effort so far to configure the agent for write-access as well.

  - Trap Forwarding
	Forwarding using the traphandle directive works fine for SNMP version 1,
	version 2c and version 3. 

  - MIB Loading
    Neither snmpd nor the applications load default libs without setting the
    MIBDIRS environment variable. At least this is what I observed in my net-snmp
    installation und Cygwin. 
    Workaround: Set MIBDIRS in your .bashrc file, e.g.:
    	export MIBDIRS=/usr/local/share/snmp/mibs

  - The distribution comes with a shell script etc/snmpdwin32.sh which automatically
    installs / starts / stops /removes the daemons as Windows services. It also
    cares for the correct environment in order to use Lua as language for the
    trap handle script. The script currently doesn't configure the services to start
    automatically during startup. Hence you will have to start them manually using
       snmpdwin32.sh start

  - The script etc/snmpdstart provides an alternative to windows services. It starts
    the agent and the trap daemon as background processes.


* Comments and bug reports
  ------------------------

  Please send your comments and bug reports to the Lua mailing list.

April 2006 (Dec 2008, July 2009, March 2010, Jan 2016)

Have fun.
herbert.leuwer@gmx.de