Presence Module

Anca-Maria Vamanu

Voice Sistem SRL

Edited by

Ovidiu Sas

Edited by

Anca-Maria Vamanu

Revision History
Revision $Revision: 8742 $$Date: 2012-02-22 18:34:34 +0100 (Wed, 22 Feb 2012) $

Table of Contents

1. Admin Guide
1.1. Overview
1.2. Dependencies
1.2.1. OpenSIPS 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. expires_offset (int)
1.3.8. max_expires_subscribe (int)
1.3.9. max_expires_publish (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. waiting_subs_daysno (int)
1.3.16. mix_dialog_presence (int)
1.3.17. bla_presentity_spec (str)
1.3.18. bla_fix_remote_target (int)
1.3.19. notify_offline_body (int)
1.4. Exported Functions
1.4.1. handle_publish(char* sender_uri)
1.4.2. handle_subscribe(char* force_active)
1.5. Exported MI Functions
1.5.1. refreshWatchers
1.5.2. cleanup
1.5.3. pres_phtable_list
1.5.4. subs_phtable_list
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
2.16. contains_presence

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 expires_offset parameter
1.8. Set max_expires_subscribe parameter
1.9. Set max_expires_publish 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 waiting_subs_daysno parameter
1.16. Set mix_dialog_presence parameter
1.17. Set bla_presentity_spec parameter
1.18. Set bla_fix_remote_target parameter
1.19. Set notify_offline_body parameter
1.20. handle_publish usage
1.21. handle_subscribe usage
2.1. presence_api_t structure

Chapter 1. Admin Guide

1.1. Overview

The modules handles PUBLISH and SUBSCRIBE messages and generates NOTIFY messages in a general, event independent way. It allows registering events to it from other OpenSIPS modules. Events that can currently be added to it are: presence, presence.winfo, dialog;sla from presence_xml module and message-summary from presence_mwi module.

The modules uses database storage. It has later been improved with memory caching operations to improve performance. The Subscribe dialog information are stored in memory and are periodically updated in database, while for Publish only the presence or absence of stored info for a certain resource is maintained in memory to avoid unnecessary, costly db operations. It is possible to configure 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 more machines using the same database.

The module can also work only with the functionality of a library, with no message processing and generation, but used only for the exported functions. This mode of operation is enabled if the db_url parameter is not set to any value.

The server follows the specifications in: RFC3265, RFC3856, RFC3857, RFC3858.

1.2. Dependencies

1.2.1. OpenSIPS Modules

The following modules must be loaded before this module:

  • a database module.

  • signaling.

1.2.2. External Libraries or Applications

  • libxml-dev.

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 information are 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 are 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 at which to clean the expired subscription dialogs.

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. expires_offset (int)

The extra time to store a subscription/publication.

Default value is “0”.

Example 1.7. Set expires_offset parameter

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

1.3.8. max_expires_subscribe (int)

The the maximum admissible expires value for SUBSCRIBE messages.

Default value is “3600”.

Example 1.8. Set max_expires_subscribe parameter

modparam("presence", "max_expires_subscribe", 3600)

1.3.9. max_expires_publish (int)

The the maximum admissible expires value for PUBLISH messages.

Default value is “3600”.

Example 1.9. Set max_expires_publish parameter

modparam("presence", "max_expires_publish", 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 machines using the same database.

Example 1.11. Set fallback2db parameter

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

1.3.12. subs_htable_size (int)

The size of the 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 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. waiting_subs_daysno (int)

The number of days to keep the record of a subscription in server database if the subscription is in pending or waiting state (no authorization policy was defined for it or the target user did not register sice the subscription and was not informed about it).

Default value is “3” days. Maximum accepted value is 30 days.

Example 1.15. Set waiting_subs_daysno parameter

modparam("presence", "waiting_subs_daysno", 2)

1.3.16. mix_dialog_presence (int)

This module parameter enables a very nice feature in the presence server - generating presence information from dialogs state. If this parameter is set, the presence server will tell you if a buddy is in a call even if his phone did not send a presence Publish with this information. You will need to load the dialoginfo modules, presence_dialoginfo, pua_dialoginfo, dialog and pua.

Default value is “0”.

Example 1.16. Set mix_dialog_presence parameter

modparam("presence", "mix_dialog_presence", 1)

1.3.17. bla_presentity_spec (str)

By default the presentity uri for BLA subscribes (event=dialog;sla) is computed from contact username + from domain. In some cases though, this way of computing the presentity might not be right ( for example if you have a SBC in front that masquerades the contact). So we added this parameter that allows defining a custom uri to be used as presentity uri for BLA subscribes. You should set this parameter to the name of a pseudovariable and then set this pseudovariable to the desired URI before calling the function handle_subscribe.

Default value is “NULL”.

Example 1.17. Set bla_presentity_spec parameter

modparam("presence", "bla_presentity_spec", "$var(bla_pres)")

1.3.18. bla_fix_remote_target (int)

Polycom has a bug in the bla implementation. It inserts the remote IP contact in the Notify body and when a phone picks up a call put on hold by another phone in the same BLA group, it sends an Invite directly to the remote IP. OpenSIPS BLA server tries to prevent this by replacing the IP contact with the domain, when this is possible.

In some cases(configurations) however this is not desirable, so this parameter was introduced to disable this behaviour when needed.

Default value is “1”.

Example 1.18. Set bla_fix_remote_target parameter

modparam("presence", "bla_fix_remote_target", 0)

1.3.19. notify_offline_body (int)

If this parameter is set, when no published info is found for a user, the presence server will generate a dummy body with status 'closed' and use it when sending Notify, instead of notifying with no body.

Default value is “0”.

Example 1.19. Set notify_offline_body parameter

modparam("presence", "notify_offline_body", 1)

1.4. Exported Functions

1.4.1.  handle_publish(char* sender_uri)

The function handles PUBLISH requests. It stores and updates published information in database and 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 1.20. handle_publish usage

		if($hdr(Sender)!= NULL)

1.4.2.  handle_subscribe(char* force_active)

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

It can take one parameter meaningful when you use a configuration with privacy rules enabled (force_active parameter in presence_xml module not set). Supposing that you have a means to tell that the contact the Subscribe message is destined to( the presentity) can not upload an xcap document with it's privacy rules, you can tell the presence server to consider that subscription allowed(with Subscription-Status:active) by calling handle_subscribe function with the string parameter "1".

	if(uri =~ "")

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 1.21. 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:


1.5.3.  pres_phtable_list

Lists all the presentity records.

Name: pres_phtable_list


MI FIFO Command Format:


1.5.4.  subs_phtable_list

Lists all the subscription records.

Name: subs_phtable_list


MI FIFO Command Format:


1.6. Installation

The module requires 3 table in OpenSIPS database: presentity, active_watchers and watchers tables. The SQL syntax to create them can be found in presence-create.sql script in the database directories in the opensips/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 OpenSIPS modules.

2.1.  bind_presence(presence_api_t* api)

This function binds the presence modules and fills the structure with the exported functions that represent functions adding events in presence module and functions specific for Subscribe processing.

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;
	pres_contains_presence_t contains_presence;

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)

2.16.  contains_presence

Field type:

typedef int (*pres_contains_presence_t)(str* pres_uri);

This function searches is a presence uri has published any presence information. It return 1 if a record is found, -1 otherwise.