Presence Module

Anca-Maria Vamanu

Edited by

Anca-Maria Vamanu

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. db_url(str)
1.3.2. presentity_table(str)
1.3.3. active_watchers_table(str)
1.3.4. watchers_table(str)
1.3.5. clean_period (int)
1.3.6. db_update_period (int)
1.3.7. to_tag_pref (str)
1.3.8. expires_offset (int)
1.3.9. max_expires (int)
1.3.10. server_address (str)
1.3.11. fallback2db (int)
1.3.12. subs_htable_size (int)
1.3.13. pres_htable_size (int)
1.3.14. enable_sphere_check (int)
1.3.15. timeout_rm_subs (int)
1.4. Exported Functions
1.4.1. handle_publish(char* sender_uri)
1.4.2. handle_subscribe()
1.5. Exported MI Functions
1.5.1. refreshWatchers
1.5.2. cleanup
1.6. Installation
2. Developer Guide
2.1. bind_presence(presence_api_t* api)
2.2. add_event
2.3. get_rules_doc
2.4. get_auth_status
2.5. apply_auth_nbody
2.6. agg_nbody
2.7. free_body
2.8. aux_body_processing
2.9. aux_free_body
2.10. evs_publ_handl
2.11. evs_subs_handl
2.12. contains_event
2.13. get_event_list
2.14. update_watchers_status
2.15. get_sphere

List of Examples

1.1. Set db_url parameter
1.2. Set presentity_table parameter
1.3. Set active_watchers_table parameter
1.4. Set watchers_table parameter
1.5. Set clean_period parameter
1.6. Set db_update_period parameter
1.7. Set to_tag_pref parameter
1.8. Set expires_offset parameter
1.9. Set max_expires parameter
1.10. Set server_address parameter
1.11. Set fallback2db parameter
1.12. Set subs_htable_size parameter
1.13. Set pres_htable_size parameter
1.14. Set enable_sphere_check parameter
1.15. Set timeout_rm_subs parameter
1.16. handle_publish usage
1.17. handle_subscribe usage
2.1. presence_api_t structure

Chapter 1. Admin Guide

1.1. Overview

The Presence module implements the core functionality of SIP event notification. It handles PUBLISH and SUBSCRIBE messages and generates NOTIFY messages in a general, event independent way. It is extensible and allows registering events to it from other Kamailio modules. Supported SIP event packages are presence, presence.winfo, dialog;sla from the presence_xml module and message-summary from the presence_mwi module.

The module uses database storage and memory caching (to improve performance). The SIP SUBSCRIBE dialog information is stored in memory and is periodically updated in the database, while for PUBLISH only the presence or absence of stored info for a certain resource is maintained in memory to avoid unnecessary, costly database operations. It is possible to enable database lookups on cache misses by configuring a fallback to database mode (by setting module parameter "fallback2db"). In this mode, in case a searched record is not found in cache, the search is continued in database. This is useful for an architecture in which processing and memory load might be divided on several Kamailio instances, maybe on different servers using the same database.

The module implements several API functions, that can be used by other modules. In fact, it can be used only as a resource module, or "library". This mode of operation is enabled if the db_url parameter is not set to any value.

The Kamailio Presence module implements the specifications in: RFC3265, RFC3856, RFC3857, RFC3858.

1.2. Dependencies

1.2.1. Kamailio Modules

The following modules must be loaded before this module:

  • a database module.

  • sl.

  • tm.

1.2.2. External Libraries or Applications

  • libxml.

1.3. Exported Parameters

1.3.1. db_url(str)

The database url.

If set, the module is a fully operational presence server. Otherwise, it is used as a 'library', for its exported functions.

Default value is “NULL”.

Example 1.1. Set db_url parameter

modparam("presence", "db_url", 

1.3.2. presentity_table(str)

The name of the db table where PUBLISH presence information is stored.

Default value is “presentity”.

Example 1.2. Set presentity_table parameter

modparam("presence", "presentity_table", "presentity")

1.3.3. active_watchers_table(str)

The name of the db table where active subscription information is stored.

Default value is “active_watchers”.

Example 1.3. Set active_watchers_table parameter

modparam("presence", "active_watchers_table", "active_watchers")

1.3.4. watchers_table(str)

The name of the db table where subscription states are stored.

Default value is “watchers”.

Example 1.4. Set watchers_table parameter

modparam("presence", "watchers_table", "watchers")

1.3.5. clean_period (int)

The period in seconds between checks if there are expired messages stored in database.

Default value is “100”. A zero or negative value disables this activity.

Example 1.5. Set clean_period parameter

modparam("presence", "clean_period", 100)

1.3.6. db_update_period (int)

The period at which to synchronize cached subscriber info with the database.

Default value is “100”. A zero or negative value disables synchronization.

Example 1.6. Set db_update_period parameter

modparam("presence", "db_update_period", 100)

1.3.7. to_tag_pref (str)

The prefix used when generating to_tag when sending replies for SUBSCRIBE requests.

Default value is “10”.

Example 1.7. Set to_tag_pref parameter

modparam("presence", "to_tag_pref", 'pres')

1.3.8. expires_offset (int)

The value in seconds that should be subtracted from the expires value when sending a 200OK for a publish. It is used for forcing the client cu send an update before the old publish expires.

Default value is “0”.

Example 1.8. Set expires_offset parameter

modparam("presence", "expires_offset", 10)

1.3.9. max_expires (int)

The the maximum admissible expires value for PUBLISH/SUBSCRIBE message (in seconds).

Default value is “3600”.

Example 1.9. Set max_expires parameter

modparam("presence", "max_expires", 3600)

1.3.10. server_address (str)

The presence server address which will become the value of Contact header filed for 200OK replies to Subscribe and Publish and in Notify messages.

Example 1.10. Set server_address parameter

modparam("presence", "server_address", "sip:")

1.3.11. fallback2db (int)

Setting this parameter enables a fallback to db mode of operation. In this mode, in case a searched record is not found in cache, the search is continued in database. Useful for an architecture in which processing and memory load might be divided on more servers using the same database. During runtime, the database is kept up2date regardless of the parameter's value.

Example 1.11. Set fallback2db parameter

modparam("presence", "fallback2db", 1)

1.3.12. subs_htable_size (int)

The size of the in-memory hash table to store subscription dialogs. This parameter will be used as the power of 2 when computing table size.

Default value is “9 (512)”.

Example 1.12. Set subs_htable_size parameter

modparam("presence", "subs_htable_size", 11)

1.3.13. pres_htable_size (int)

The size of the in-memory hash table to store publish records. This parameter will be used as the power of 2 when computing table size.

Default value is “9 (512)”.

Example 1.13. Set pres_htable_size parameter

modparam("presence", "pres_htable_size", 11)

1.3.14. enable_sphere_check (int)

This parameter is a flag that should be set if permission rules include sphere checking. The sphere information is expected to be present in the RPID body published by the presentity. The flag is introduced as this check requires extra processing that should be avoided if this feature is not supported by the clients.

Default value is “0 ”.

Example 1.14. Set enable_sphere_check parameter

modparam("presence", "enable_sphere_check", 1)

1.3.15. timeout_rm_subs (int)

This parameter is a flag that should be set if subscriptions should be removed from the active_watchers when a NOTIFY times out. RFC3265 section 3.2.2 defines this behaviour as a SHOULD, so by default it is on. Disabling this will keep subscriptions active on unreliable networks.

Default value is “1”.

Example 1.15. Set timeout_rm_subs parameter

modparam("presence", "timeout_rm_subs", 0)

1.4. Exported Functions

1.4.1.  handle_publish(char* sender_uri)

Handles PUBLISH requests by storing and updating published information in memory cach and database, then calls functions to send NOTIFY messages when changes in the published information occur. It takes one argument -> sender_uri. The parameter was added for enabling BLA implementation. If present, Notification of a change in published state is not sent to the respective uri even though a subscription exists. It should be taken from the Sender header. It was left at the decision of the administrator whether or not to transmit the content of this header as parameter for handle_publish, to prevent security problems.

This function can be used from REQUEST_ROUTE.

Return code:

  • 1 - if success.

  • -1 - if error.

The module sends an appropriate stateless reply in all cases.

Example 1.16. handle_publish usage

		if($hdr(Sender)!= NULL)

1.4.2.  handle_subscribe()

The function which handles SUBSCRIBE requests. It stores or updates information in memory and database and calls functions to send Notify messages when a SUBSCRIBE which initiate a dialog is received

This function can be used from REQUEST_ROUTE.

Return code:

  • 1 - if success.

  • -1 - if error.

The module sends an appropriate stateless reply in all cases.

Example 1.17. handle_subscribe usage


1.5. Exported MI Functions

1.5.1.  refreshWatchers

Triggers sending Notify messages to watchers if a change in watchers authorization or in published state occurred.

Name: refreshWatchers


  • presentity_uri : the uri of the user who made the change and whose watchers should be informed

  • event : the event package

  • refresh type : it distinguishes between the two different types of events that can trigger a refresh:

    • a change in watchers authentication: refresh type= 0 ;

    • a statical update in published state (either through direct update in db table or by modifying the pidf manipulation document, if pidf_manipulation parameter is set): refresh type!= 0.

MI FIFO Command Format:


1.5.2.  cleanup

Manually triggers the cleanup functions for watchers and presentity tables. Useful if you have set clean_period to zero or less.

Name: cleanup


MI FIFO Command Format:


1.6. Installation

The module requires 3 tables in the Kamailio database: "presentity", "active_watchers" and "watchers". The SQL syntax to create them can be found in presence-create.sql script in the database directories in the kamailio/scripts folder. You can also find the complete database documentation on the project webpage,

Chapter 2. Developer Guide

The module provides the following functions that can be used in other Kamailio modules.

2.1.  bind_presence(presence_api_t* api)

This function binds the presence modules and fills the structure with one exported function -> add_event, which when called adds a new event to be handled by presence.

Example 2.1. presence_api_t structure

typedef struct presence_api {
	add_event_t add_event;
	contains_event_t contains_event;
	search_event_t search_event;
	get_event_list_t get_event_list;
	update_watchers_t update_watchers_status;
	/* subs hash table handling functions */
	new_shtable_t new_shtable;
	destroy_shtable_t destroy_shtable;
	insert_shtable_t insert_shtable;
	search_shtable_t search_shtable;
	delete_shtable_t delete_shtable;
	update_shtable_t update_shtable;
	/* function to duplicate a subs structure*/
	mem_copy_subs_t  mem_copy_subs;
	/* function used for update in database*/
	update_db_subs_t update_db_subs;
	/* function to extract dialog information from a
	SUBSCRIBE message */
	extract_sdialog_info_t extract_sdialog_info;
	/* function to request sphere defition for a presentity */
	pres_get_sphere_t get_sphere;


2.2.  add_event

Field type:

typedef int (*add_event_t)(pres_ev_t* event);

This function receives as a parameter a structure with event specific information and adds it to presence event list.

The structure received as a parameter:

typedef struct pres_ev
	str name;
	event_t* evp;
	str content_type;
	int default_expires;
	int type;
	int etag_not_new;
	 *  0 - the standard mechanism (allocating new etag
			for each Publish)
	 *  1 - allocating an etag only
			for an initial Publish 
	int req_auth;
	get_rules_doc_t* get_rules_doc;
	apply_auth_t*  apply_auth_nbody;
	is_allowed_t*  get_auth_status;
	/* an agg_body_t function should be registered
	 * if the event permits having multiple published
	 * states and requires an aggregation of the information
	 * otherwise, this field should be NULL and the last
	 * published state is taken when constructing Notify msg
	agg_nbody_t* agg_nbody;
	publ_handling_t  * evs_publ_handl;
	subs_handling_t  * evs_subs_handl;
	free_body_t* free_body;
    /* sometimes it is necessary that a module make changes for a body for each
     * active watcher (e.g. setting the "version" parameter in an XML document.
     * If a module registers the aux_body_processing callback, it gets called for
     * each watcher. It either gets the body received by the PUBLISH, or the body
     * generated by the agg_nbody function.
     * The module can deceide if it makes a copy of the original body, which is then
     * manipulated, or if it works directly in the original body. If the module makes a
     * copy of the original body, it also has to register the aux_free_body() to
     * free this "per watcher" body.
    aux_body_processing_t* aux_body_processing;
    free_body_t* aux_free_body;
	struct pres_ev* wipeer;			
	struct pres_ev* next;

2.3.  get_rules_doc

Filed type:

typedef int (get_rules_doc_t)(str* user, str* domain, str** rules_doc);

This function returns the authorization rules document that will be used in obtaining the status of the subscription and processing the notified body. A reference to the document should be put in the auth_rules_doc of the subs_t structure given as a parameter to the functions described bellow.

2.4.  get_auth_status

This filed is a function to be called for a subscription request to return the state for that subscription according to authorization rules. In the auth_rules_doc field of the subs_t structure received as a parameter should contain the rules document of the presentity in case, if it exists.

It is called only if the req_auth field is not 0.

Filed type:

typedef int (is_allowed_t)(struct subscription* subs);

2.5.  apply_auth_nbody

This parameter should be a function to be called for an event that requires authorization, when constructing final body. The authorization document is taken from the auth_rules_doc field of the subs_t structure given as a parameter. It is called only if the req_auth field is not 0.

Filed type:

typedef int (apply_auth_t)(str* , struct subscription*, str** );

2.6.  agg_nbody

If present, this field marks that the events requires aggregation of states. This function receives a body array and should return the final body. If not present, it is considered that the event does not require aggregation and the most recent published information is used when constructing Notifies.

Filed type:

typedef str* (agg_nbody_t)(str* pres_user, str* pres_domain, 
str** body_array, int n, int off_index);

2.7.  free_body

This field must be field in if subsequent processing is performed on the info from database before being inserted in Notify message body(if agg_nbody or apply_auth_nbody fields are filled in). It should match the allocation function used when processing the body.

Filed type:

typedef void(free_body_t)(char* body);

2.8.  aux_body_processing

This field must be set if the module needs to manipulate the NOTIFY body for each watcher. E.g. if the XML body includes a 'version' parameter which will be increased for each NOTIFY, on a "per watcher" basis. The module can either allocate a new buffer for the new body an return it (aux_free_body function must be set too) or it manipualtes the original body directly and returns NULL.

Filed type:

typedef str* (aux_body_processing_t)(struct subscription *subs, str* body);

2.9.  aux_free_body

This field must be set if the module registers the aux_body_processing function and allocates memory for the new modified body. Then, this function will be used to free the pointer returned by the aux_body_processing function. If the module does use the aux_body_processing, but does not allocate new memory, but manipulates directly the original body buffer, then the aux_body_processing must return NULL and this field should not be set.

Filed type:

typedef void(free_body_t)(char* body);

2.10.  evs_publ_handl

This function is called when handling Publish requests. Most contain body correctness check.

typedef int (publ_handling_t)(struct sip_msg*);

2.11.  evs_subs_handl

It is not compulsory. Should contain event specific handling for Subscription requests.

Filed type:

typedef int (subs_handling_t)(struct sip_msg*);

2.12.  contains_event

Field type:

typedef pres_ev_t* (*contains_event_t)(str* name,
event_t* parsed_event);

The function parses the event name received as a parameter and searches the result in the list. It returns the found event or NULL, if not found. If the second argument is an allocated event_t* structure it fills it with the result of the parsing.

2.13.  get_event_list

Field type:

typedef int (*get_event_list_t) (str** ev_list);

This function returns a string representation of the events registered in presence module.( used for Allowed-Events header).

2.14.  update_watchers_status

Field type:

typedef int (*update_watchers_t)(str pres_uri, pres_ev_t* ev,
str* rules_doc);

This function is an external command that can be used to announce a change in authorization rules for a presentity. It updates the stored status and sends a Notify to the watchers whose status has changes. (used by presence_xml module when notified through an MI command of a change in an xcap document).

2.15.  get_sphere

Field type:

typedef char* (*pres_get_sphere_t)(str* pres_uri);

This function searches for a sphere definition in the published information if this has type RPID. If not found returns NULL. (the return value is allocated in private memory and should be freed)