cfgutils Module

Henning Westerholt

   1und1 Internet AG
   <henning.westerholt@1und1.de>

Carsten Bock

   BASIS AudioNet GmbH

Elena-Ramona Modroiu

   rosdev.ro
   <ramona@rosdev.ro>

Jiri Kuthan

   <jiri@iptel.org>

Edited by

Daniel-Constantin Mierla

   <miconda@gmail.com>

   Copyright © 2007, 2008, 2004 1und1 Internet AG, BASIS AudioNet GmbH,
   Elena-Ramona Modroiu, FhG FOKUS
     __________________________________________________________________

   Table of Contents

   1. Admin Guide

        1. Overview
        2. Dependencies
        3. Parameters

              3.1. initial_probability (string)
              3.2. hash_file (string)
              3.3. initial_gflags (integer)
              3.4. lock_set_size (integer)

        4. Functions

              4.1. rand_event()
              4.2. rand_set_prob(probabiltiy)
              4.3. rand_reset_prob()
              4.4. rand_get_prob()
              4.5. sleep(time)
              4.6. usleep(time)
              4.7. abort()
              4.8. pkg_status()
              4.9. pkg_summary()
              4.10. shm_status()
              4.11. shm_summary()
              4.12. set_gflag(flag)
              4.13. reset_gflag(flag)
              4.14. is_gflag(flag)
              4.15. lock(key)
              4.16. unlock(key)
              4.17. core_hash(string1, string2, size)

        5. MI Commands

              5.1. rand_set_prop
              5.2. rand_reset_prob
              5.3. rand_get_prob
              5.4. check_config_hash
              5.5. get_config_hash
              5.6. set_gflag
              5.7. reset_gflag
              5.8. is_gflag
              5.9. get_gflags

        6. Exported pseudo-variables

              6.1. $RANDOM

   List of Examples

   1.1. initial_probability parameter usage
   1.2. hash_file parameter usage
   1.3. initial parameter usage
   1.4. lock_set_size parameter usage
   1.5. rand_event() usage
   1.6. rand_set_prob() usage
   1.7. rand_reset_prob() usage
   1.8. rand_get_prob() usage
   1.9. sleep usage
   1.10. usleep usage
   1.11. abort usage
   1.12. pkg_status usage
   1.13. pkg_summary usage
   1.14. shm_status usage
   1.15. shm_summary usage
   1.16. set_gflag() usage
   1.17. reset_gflag() usage
   1.18. is_gflag() usage
   1.19. lock() usage
   1.20. unlock() usage
   1.21. core_hash() usage
   1.22. rand_set_prob usage
   1.23. rand_reset_prob usage
   1.24. rand_get_prob usage
   1.25. check_config_hash usage
   1.26. get_config_hash usage
   1.27. set_gflag usage
   1.28. reset_gflag usage
   1.29. is_gflag usage
   1.30. get_gflags usage
   1.31. RANDOM pseudo-variable usage

Chapter 1. Admin Guide

   Table of Contents

   1. Overview
   2. Dependencies
   3. Parameters

        3.1. initial_probability (string)
        3.2. hash_file (string)
        3.3. initial_gflags (integer)
        3.4. lock_set_size (integer)

   4. Functions

        4.1. rand_event()
        4.2. rand_set_prob(probabiltiy)
        4.3. rand_reset_prob()
        4.4. rand_get_prob()
        4.5. sleep(time)
        4.6. usleep(time)
        4.7. abort()
        4.8. pkg_status()
        4.9. pkg_summary()
        4.10. shm_status()
        4.11. shm_summary()
        4.12. set_gflag(flag)
        4.13. reset_gflag(flag)
        4.14. is_gflag(flag)
        4.15. lock(key)
        4.16. unlock(key)
        4.17. core_hash(string1, string2, size)

   5. MI Commands

        5.1. rand_set_prop
        5.2. rand_reset_prob
        5.3. rand_get_prob
        5.4. check_config_hash
        5.5. get_config_hash
        5.6. set_gflag
        5.7. reset_gflag
        5.8. is_gflag
        5.9. get_gflags

   6. Exported pseudo-variables

        6.1. $RANDOM

1. Overview

   Useful extensions for the server configuration.

   The cfgutils module can be used to introduce randomness to the
   behaviour of the server. It provides setup functions and the
   "rand_event" function. This function return either true or false,
   depending on a random value and a specified probability. E.g. if you
   set via fifo or script a probability value of 5%, then 5% of all calls
   to rand_event will return true. The pseudovariable "$RANDOM" could be
   used to introduce random values e.g. into a SIP reply.

   The benefit of this module is the probability of the decision can be
   manipulated by external applications such as web interface or command
   line tools. The probability must be specified as percent value, ranging
   from 0 to 100.

   The module exports commands to FIFO server that can be used to change
   the global settings via FIFO interface. The FIFO commands are:
   "set_prob", "reset_prob" and "get_prob".

   This module can be used for simple load-shedding, e.g. reply 5% of the
   Invites with a 503 error and a adequate random Retry-After value.

   The module provides as well functions to delay the execution of the
   server. The functions "sleep" and "usleep" could be used to let the
   server wait a specific time interval.

   It can also hash the config file used from the server with a (weak)
   cryptographic hash function on startup. This value is saved and can be
   later compared to the actual hash, to detect modifications of this file
   after the server start. This functions are available as the FIFO
   commands "check_config_hash" and "get_config_hash".

   The gflags functionality (global flags) keeps a bitmap of flags in
   shared memory and may be used to change behaviour of server based on
   value of the flags. Example:
        if (is_gflag("1")) {
                t_relay("udp:10.0.0.1:5060");
        } else {
                t_relay("udp:10.0.0.2:5060");
        }

   The benefit of this is the value of the switch flags can be manipulated
   by external applications such as web interface or command line tools.
   The size of bitmap is 32.

   The module exports external commands that can be used to change the
   global flags via Management Interface. The MI commands are:
   "set_gflag", "reset_gflag" and "is_gflag".

2. Dependencies

   The module depends on the following modules (in the other words the
   listed modules must be loaded before this module):
     * none

3. Parameters

   3.1. initial_probability (string)
   3.2. hash_file (string)
   3.3. initial_gflags (integer)
   3.4. lock_set_size (integer)

3.1. initial_probability (string)

   The initial value of the probability.

   Default value is "10".

   Example 1.1. initial_probability parameter usage
modparam("cfgutils", "initial_probability", 15)

3.2. hash_file (string)

   The config file name for that a hash value should be calculated on
   startup.

   There is no default value, is no parameter is given the hash
   functionality is disabled.

   Example 1.2. hash_file parameter usage
modparam("cfgutils", "hash_file", "/etc/kamailio/kamailio.cfg")

3.3. initial_gflags (integer)

   The initial value of global flags bitmap.

   Default value is "0".

   Example 1.3. initial parameter usage
modparam("cfgutils", "initial_gflags", 15)

3.4. lock_set_size (integer)

   Size of lock set - the value is used as power of two to compute the
   size of lock array.

   Default value is "0" - no lock set created.

   Example 1.4. lock_set_size parameter usage
modparam("cfgutils", "lock_set_size", 4)

4. Functions

   4.1. rand_event()
   4.2. rand_set_prob(probabiltiy)
   4.3. rand_reset_prob()
   4.4. rand_get_prob()
   4.5. sleep(time)
   4.6. usleep(time)
   4.7. abort()
   4.8. pkg_status()
   4.9. pkg_summary()
   4.10. shm_status()
   4.11. shm_summary()
   4.12. set_gflag(flag)
   4.13. reset_gflag(flag)
   4.14. is_gflag(flag)
   4.15. lock(key)
   4.16. unlock(key)
   4.17. core_hash(string1, string2, size)

4.1. rand_event()

   Return true or false, depending on a random value and a probability
   value.

   Example 1.5. rand_event() usage
...
if (rand_event()) {
  append_to_reply("Retry-After: 120\n");
  sl_send_reply("503", "Try later");
  exit;
};
# normal message processing follows
...

4.2. rand_set_prob(probabiltiy)

   Set the "probability" of the decision.

   "probability" can have a value from the range 0..100.

   Example 1.6. rand_set_prob() usage
...
rand_set_prob("4");
...

4.3. rand_reset_prob()

   Reset the probability back to the inital value.

   Example 1.7. rand_reset_prob() usage
...
rand_reset_prob();
...

4.4. rand_get_prob()

   Return the current probability setting, e.g. for logging purposes.

   Example 1.8. rand_get_prob() usage
...
rand_get_prob();

4.5. sleep(time)

   Waits "time" seconds.

   Meaning of the parameters is as follows:
     * time - Time to wait in seconds.

   This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
   FAILURE_ROUTE, BRANCH_ROUTE.

   Example 1.9. sleep usage
...
sleep("1");
...

4.6. usleep(time)

   Waits "time" micro-seconds.

   Meaning of the parameters is as follows:
     * time - Time to wait in micro-seconds (1/1000000 of a second).

   This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
   FAILURE_ROUTE, BRANCH_ROUTE.

   Example 1.10. usleep usage
...
# wait 5 miliseconds
usleep("5000");
...

4.7. abort()

   Debugging function that aborts the server. Depending on the
   configuration of the server a core dump will be created.

   This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
   FAILURE_ROUTE, BRANCH_ROUTE.

   Example 1.11. abort usage
...
abort();
...

4.8. pkg_status()

   Debugging function that dumps the status for the private (PKG) memory.
   This information is logged to the default log facility, depending on
   the general log level and the memlog setting. You need to compile the
   server with activated memory debugging to get detailed informations.

   This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
   FAILURE_ROUTE, BRANCH_ROUTE.

   Example 1.12. pkg_status usage
...
pkg_status();
...

4.9. pkg_summary()

   Debugging function that dumps the summary for the private (PKG) memory
   usage. This information is logged to the default log facility,
   depending on the general log level and the memlog setting. You need to
   compile the server with activated memory debugging to get detailed
   informations.

   This function can be used from ANY_ROUTE.

   Example 1.13. pkg_summary usage
...
pkg_summary();
...

4.10. shm_status()

   Debugging function that dumps the status for the shared (SHM) memory.
   This information is logged to the default log facility, depending on
   the general log level and the memlog setting. You need to compile the
   server with activated memory debugging to get detailed informations.

   This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
   FAILURE_ROUTE, BRANCH_ROUTE.

   Example 1.14. shm_status usage
...
shm_status();
...

4.11. shm_summary()

   Debugging function that dumps the summary for the shared (SHM) memory
   usage. This information is logged to the default log facility,
   depending on the general log level and the memlog setting. You need to
   compile the server with activated memory debugging to get detailed
   informations.

   This function can be used from ANY_ROUTE.

   Example 1.15. shm_summary usage
...
shm_summary();
...

4.12. set_gflag(flag)

   Set the bit at the position "flag" in global flags.

   "flag" can have a value in the range of 0..31.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE,
   ONREPLY_ROUTE, BRANCH_ROUTE and LOCAL_ROUTE.

   Example 1.16. set_gflag() usage
...
set_gflag("4");
...

4.13. reset_gflag(flag)

   Reset the bit at the position "flag" in global flags.

   "flag" can have a value in the range of 0..31.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE,
   ONREPLY_ROUTE, BRANCH_ROUTE and LOCAL_ROUTE.

   Example 1.17. reset_gflag() usage
...
reset_gflag("4");
...

4.14. is_gflag(flag)

   Check if bit at the position "flag" in global flags is set.

   "flag" can have a value in the range of 0..31.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE,
   ONREPLY_ROUTE, BRANCH_ROUTE and LOCAL_ROUTE.

   Example 1.18. is_gflag() usage
...
if(is_gflag("4"))
{
        log("global flag 4 is set\n");
} else {
        log("global flag 4 is not set\n");
};
...

4.15. lock(key)

   Lock the key. Can be used to syncronize operations in config file, a
   hash id is computed over the key and appropriate lock is set in the
   lock array controlled by parameter "lock_set_size". Do not use lock()
   after another lock() unless you are sure the keys hit different array
   entries.

   "key" can be static string or string with PVs.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE,
   ONREPLY_ROUTE, BRANCH_ROUTE and LOCAL_ROUTE.

   Example 1.19. lock() usage
...
lock("$rU");
...

4.16. unlock(key)

   Unlock the key.

   "key" can be static string or string with PVs.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE,
   ONREPLY_ROUTE, BRANCH_ROUTE and LOCAL_ROUTE.

   Example 1.20. unlock() usage
...
unlock("$rU");
...

4.17. core_hash(string1, string2, size)

   Exported function that enables the core_hash() function to be used from
   the configuration file.

   This is a quick and simple hash function and it is not
   cryptographically secure. This function should not be used for any
   security related purposes.

   Parameters:
     * "string1" first string to hash
     * "string2" (optional) second string to hash (set to "" if not
       needed)
     * "size" size of the hash space (used as a power of 2)

   This function can be used from ANY_ROUTE.

   Example 1.21. core_hash() usage
...
core_hash("$ci", "", 4);
...

5. MI Commands

   5.1. rand_set_prop
   5.2. rand_reset_prob
   5.3. rand_get_prob
   5.4. check_config_hash
   5.5. get_config_hash
   5.6. set_gflag
   5.7. reset_gflag
   5.8. is_gflag
   5.9. get_gflags

   Functions that check or change some global flags accepts one parameter
   which is the flag bitmap/mask specifing the corresponding flags. It is
   not possible to specify directly the flag position that should be
   changed as in the functions available in the routing script.

5.1. rand_set_prop

   Set the probability value to the given parameter. The parameter should
   be a percent value.

   The parameter value must be a number from 0 to 100.

   Example 1.22. rand_set_prob usage
...
$ kamctl fifo rand_set_prob 10
...

5.2. rand_reset_prob

   Reset the probability value to the inital start value.

   This command don't need a parameter.

   Example 1.23. rand_reset_prob usage
...
$ kamctl fifo rand_reset_prob
...

5.3. rand_get_prob

   Return the actual probability setting.

   The function return the actual probability value.

   Example 1.24. rand_get_prob usage
...
$ kamctl fifo get_prob
The actual probability is 50 percent.
...

5.4. check_config_hash

   Check if the actual config file hash is identical to the stored one.

   The function returns 200 OK if the hash values are identical, 400 if
   there are not identical, 404 if no file for hashing has been configured
   and 500 on errors. Additional a short text message is printed.

   Example 1.25. check_config_hash usage
...
$ kamctl fifo check_config_hash
The actual config file hash is identical to the stored one.
...

5.5. get_config_hash

   Return the stored config file hash.

   The function returns 200 OK and the hash value on success or 404 if no
   file for hashing has been configured.

   Example 1.26. get_config_hash usage
...
$ kamctl fifo get_config_hash
1580a37104eb4de69ab9f31ce8d6e3e0
...

5.6. set_gflag

   Set the value of some flags (specified by bitmask) to 1.

   The parameter value must be a bitmask in decimal or hexadecimal format.
   The bitmask has a 32 bit size.

   Example 1.27. set_gflag usage
...
$ kamctl fifo set_gflag 1
$ kamctl fifo set_gflag 0x3
...

5.7. reset_gflag

   Reset the value of some flags to 0.

   The parameter value must be a bitmask in decimal or hexadecimal format.
   The bitmask has a 32 bit size.

   Example 1.28. reset_gflag usage
...
$ kamctl fifo reset_gflag 1
$ kamctl fifo reset_gflag 0x3
...

5.8. is_gflag

   Returns true if the all the flags from the bitmask are set.

   The parameter value must be a bitmask in decimal or hexadecimal format.
   The bitmask has a 32 bit size.

   The function returns TRUE if all the flags from the set are set and
   FALSE if at least one is not set.

   Example 1.29. is_gflag usage
...
$ kamctl fifo set_gflag 1024
$ kamctl fifo is_gflag 1024
TRUE
$ kamctl fifo is_gflag 1025
TRUE
$ kamctl fifo is_gflag 1023
FALSE
$ kamctl fifo set_gflag 0x10
$ kamctl fifo is_gflag 1023
TRUE
$ kamctl fifo is_gflag 1007
FALSE
$ kamctl fifo is_gflag 16
TRUE
...

5.9. get_gflags

   Return the bitmap with all flags. The function gets no parameters and
   returns the bitmap in hexadecimal and decimal format.

   Example 1.30. get_gflags usage
...
$ kamctl fifo get_gflags
0x3039
12345
...

6. Exported pseudo-variables

   6.1. $RANDOM

6.1. $RANDOM

   Returns a random value from the [0 - 2^31) range.

   Example 1.31. RANDOM pseudo-variable usage
...
if (rand_event()) {
  $avp(i:10) = ($RANDOM / 16777216); # 2^24
  if ($avp(i:10) < 10) {
     $avp(i:10) = 10;
  }
  append_to_reply("Retry-After: $avp(i:10)\n");
  sl_send_reply("503", "Try later");
  exit;
};
# normal message processing follows
