app_lua Module

Daniel-Constantin Mierla

Edited by

Daniel-Constantin Mierla

Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
3. Parameters
3.1. load (string)
3.2. register (string)
3.3. reload (boolean)
4. Functions
4.1. lua_dofile(path)
4.2. lua_dostring(script)
4.3. lua_run(func [, params])
4.4. lua_runstring(script)
5. RPC Commands
5.1. app_lua.list
5.2. app_lua.reload
5.3. app_lua.api_list
6. Example of usage

List of Examples

1.1. Build against LuaJIT libraries
1.2. Set load parameter
1.3. Set register parameter
1.4. Set reload parameter
1.5. lua_dofile usage
1.6. lua_dostring usage
1.7. lua_run usage
1.8. lua_runstring usage

Chapter 1. Admin Guide

1. Overview

This module allows executing Lua scripts from config file. It exports a set of functions to Lua in order to access the current processed SIP message. These functions are within Lua module 'sr'.

Lua ( is a fast and easy to embed scripting language. Exported API from SIP router to Lua is documented in the dokuwiki.

The module has two Lua contexts:

  • first is used for functions lua_dofile() and lua_dostring().

  • second is used for function lua_run() and parameter 'load'. Therefore lua_run() cannot execute functions from scripts loaded via lua_dofile() in config. This is kind of caching mode, avoiding reading file every time, but you must be sure you do not have someting that is executed by default and requires access to SIP message.

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • none.

2.2. External Libraries or Applications

The following libraries or applications must be installed before running Kamailio with this module loaded:

  • liblua5.1-dev - Lua devel library.

This module can be compiled against LuaJIT compiler (instead of standard Lua). Then this library is needed:

  • libluajit-5.1-dev - LuaJIT devel library.

To enable that, LUAJIT variable has to be set.

Example 1.1. Build against LuaJIT libraries

E.g: $ LUAJIT="yes" make modules modules=modules/app_lua

(Warning: LuaJIT version is 5.1, so scripts prepared for higher Lua versions may not work with LuaJIT)

3. Parameters

3.1. load (string)

Set the path to the Lua script to be loaded at startup. Then you can use lua_run(function, params) to execute a function from the script at runtime.

Default value is null.

Example 1.2. Set load parameter

modparam("app_lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")

3.2. register (string)

NOTE: Since Kamailio v5.0, KEMI exports are available in Lua script under KSR module. These exports cover most of the modules, a lot more that those listed next. The KEMI exports are the recommended to be used, the old 'sr' module might be obsoleted soon. To read more about KEMI exports and available KSR submodules, see:

Use this parameter to register optional Kamailio submodules to Lua. Available submodules are:

  • alias_db - register functions from alias_db module under 'sr.alias_db'.

  • auth - register functions from auth module under 'sr.auth'.

  • auth_db - register functions from auth_db module under 'sr.auth_db'.

  • dispatcher - register functions from dispatcher module under 'sr.dispatcher'.

  • maxfwd - register functions from maxfwd module under 'sr.maxfwd'.

  • msilo - register functions from msilo module under 'sr.msilo'.

  • presence - register functions from presence module under 'sr.presence'.

  • presence_xml - register functions from presence_xml module under 'sr.presence_xml'.

  • pua_usrloc - register functions from pua_usrloc module under 'sr.pua_usrloc'.

  • registrar - register functions from registrar module under 'sr.registrar'.

  • rls - register functions from rls module under 'sr.rls'.

  • rr - register functions from rr module under 'sr.rr'.

  • sanity - register functions from sanity module under 'sr.sanity'.

  • sdpops - register functions from sdpops module under 'sr.sdpops'.

  • siputils - register functions from siputils module under 'sr.siputils'.

  • sl - register functions from sl module under ''.

  • sqlops - register functions from sqlops module under 'sr.sqlops'.

  • textops - register functions from textops module under 'sr.textops'.

  • tm - register functions from tm module under ''.

  • xhttp - register functions from xhttp module under 'sr.xhttp'.

Note that 'sr', 'sr.hdr' and 'sr.pv' modules are always registered to Lua.

Default value is null.

Example 1.3. Set register parameter

modparam("app_lua", "register", "sl")

3.3. reload (boolean)

If reload is 1 enables the ability to reload the scripts using the RPC app_lua.reload command.

Default value is 0 (off).

Example 1.4. Set reload parameter

modparam("app_lua", "reload", 1)

4. Functions

4.1.  lua_dofile(path)

Execute the Lua script stored in 'path'. The parameter can be a string with pseudo-variables evaluated at runtime.

Example 1.5. lua_dofile usage


4.2.  lua_dostring(script)

Execute the Lua script stored in parameter. The parameter can be a string with pseudo-variables.

Example 1.6. lua_dostring usage

if(!lua_dostring("sr.log([[err]], [[----------- Hello World from $fU\n]])"))
    xdbg("SCRIPT: failed to execute lua script!\n");

4.3.  lua_run(func [, params])

Execute the Lua function 'func' giving 'params' as parameters. There can be up to 3 string parameters after 'func' (overall, max 4 params, first is the function). The function must exist in the Lua script loaded at startup via parameter 'load'. Parameters can be strings with pseudo-variables that are evaluated at runtime.

Example 1.7. lua_run usage

if(!lua_run("sr_append_fu_to_reply")) {
    xdbg("SCRIPT: failed to execute lua function!\n");
lua_run("lua_func1", "$rU");
lua_run("lua_func2", "$rU", "2");
lua_run("lua_func3", "$rU", "2", "$si");

4.4.  lua_runstring(script)

Execute the Lua script stored in parameter. The parameter can be a string with pseudo-variables. The script is executed in Lua context specific to loaded Lua files at startup.

Example 1.8. lua_runstring usage

if(!lua_runstring("sr.log([[err]], [[----------- Hello World from $fU\n]])"))
    xdbg("SCRIPT: failed to execute lua script!\n");

5. RPC Commands

5.1.  app_lua.list

Lists the id and path for every script loaded by the load parameter.

Name: app_lua.list

Parameters: none


    kamcmd app_lua.list

5.2.  app_lua.reload

Marks the need to reload the selected script. The actual reload is done by every working process when the next call to lua_run function is executed. If no parameter is added all the scripts are selected to be reloaded.

Name: app_lua.reload

Parameters: id


    kamcmd app_lua.reload 0

5.3.  app_lua.api_list

Lists the exported KEMI functions that can be used inside Lua scripts.

Name: app_lua.api_list

Parameters: none


    kamcmd app_lua.api_list

6. Example of usage

Create your Lua script and stored on file system, say: '/usr/local/etc/kamailio/lua/myscript.lua'.

function sr_append_fu_to_reply()
	sr.hdr.append_to_reply("P-From: " .. sr.pv.get("$fu") .. "\r\n");

Load the script via parameter 'load' and execute function via lua_run(...).

modparam("app_lua", "load", "/usr/local/etc/kamailio/lua/myscript.lua")
route {
        xdbg("SCRIPT: failed to execute lua function!\n");