exec Module

Jiri Kuthan

FhG FOKUS

Daniel-Constantin Mierla

Edited by

Jan Janak

Revision History
Revision $Revision: 4594 $$Date: 2008-08-06 12:08:33 +0200 (Wed, 06 Aug 2008) $

Table of Contents

1. Admin Guide
1.1. Overview
1.2. Dependencies
1.2.1. Kamailio Modules
1.2.2. External Libraries or Applications
1.3. Exported Parameters
1.3.1. setvars (integer)
1.3.2. time_to_kill (integer)
1.4. Exported Functions
1.4.1. exec_dset(command)
1.4.2. exec_msg(command)
1.4.3. exec_avp(command [, avplist])
1.5. Known Issues

List of Examples

1.1. Set “setvars” parameter
1.2. Set “time_to_kill” parameter
1.3. exec_dset usage
1.4. exec_msg usage
1.5. exec_avp usage

Chapter 1. Admin Guide

1.1. Overview

Exec module allows to start an external command from a Kamailio script. The commands may be any valid shell commands--the command string is passed to shell using “popen” command. Kamailio passes additionally lot of information about request in environment variables:

  • SIP_HF_<hf_name> contains value of each header field in request. If a header field occurred multiple times, values are concatenated and comma-separated. <hf_name> is in capital letters. Ff a header-field name occurred in compact form, <hf_name> is canonical.

  • SIP_TID is transaction identifier. All request retransmissions or CANCELs/ACKs associated with a previous INVITE result in the same value.

  • SIP_DID is dialog identifier, which is the same as to-tag. Initially, it is empty.

  • SIP_SRCIP is source IP address from which request came.

  • SIP_ORURI is original request URI.

  • SIP_RURI is current request URI (if unchanged, equal to original).

  • SIP_USER is userpart of current request URI.

  • SIP_OUSER is userpart of original request URI.

NOTE: The envirnment variables must be specified with double $ (e.g., $$SIP_OUSER) in the parameters given to exec functions. Otherwise they will be evaluated as Kamailio pseudo-variables, throwing errors.

1.2. Dependencies

1.2.1. Kamailio Modules

The following modules must be loaded before this module:

  • No dependencies on other Kamailio modules.

1.2.2. External Libraries or Applications

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

  • None.

1.3. Exported Parameters

1.3.1. setvars (integer)

Turn off to disable setting environment variables for executed commands.

Default value is 1.

Example 1.1. Set “setvars” parameter

...
modparam("exec", "setvars", 1)
...

1.3.2.  time_to_kill (integer)

Specifies the longest time a program is allowed to execute. If the time is exceeded, the program is killed.

Default value is 0.

Example 1.2. Set “time_to_kill” parameter

...
modparam("exec", "time_to_kill", 20)
...

1.4. Exported Functions

1.4.1.  exec_dset(command)

Executes an external command. Current URI is passed to the command as parameter. Output of the command is considered URI set (separated by lines).

Meaning of the parameters is as follows:

  • command - Command to be executed. It can include pseudo- variabes;

WARNING: if the var you are passing out has a bash special character in it, the var needs to be placed inside quotes, for example: exec_dset("print-contact.sh '$ct'");

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

Example 1.3. exec_dset usage

...
exec_dset("echo TEST > /tmp/test.txt");
exec_dset("echo TEST > /tmp/$rU.txt");
...

1.4.2.  exec_msg(command)

Executes an external command. The whole message is passed to it in input, no command-line parameters are added, output of the command is not processed.

The “examples” directory in the source tarball contains several examples that shows how to use this function.

Meaning of the parameters is as follows:

  • command - Command to be executed. It can include pseudo-variables.

WARNING: if the var you are passing out has a bash special character in it, the var needs to be placed inside quotes, for example: exec_msg("print-contact.sh '$ct'");

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

Example 1.4. exec_msg usage

...
exec_msg("echo TEST > /tmp/test.txt");
exec_msg("echo TEST > /tmp/$rU.txt");
...

1.4.3.  exec_avp(command [, avplist])

Executes an external command. Each line from output of the command is saved in an AVP from 'avplist'. If 'avplist' is missing, the AVP are named 1, 2, 3, ...

Meaning of the parameters is as follows:

  • command - Command to be executed. It can include pseudo- variabes;

  • avplist - comma separated list with AVP names to store the result in;

WARNING: if the var you are passing out has a bash special character in it, the var needs to be placed inside quotes, for example: exec_avp("print-contact.sh '$ct'");

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

Example 1.5. exec_avp usage

...
exec_avp("echo TEST");
exec_avp("echo TEST", "$avp(s:test)");
...

1.5. Known Issues

There is currently no guarantee that scripts ever return and stop blocking SIP server. (There is kill.c but it is not used along with the current mechanisms based on popen. Besides that kill.c is ugly).