Presence Module

Anca-Maria Vamanu

   voice-system.ro

Edited by

Anca-Maria Vamanu

   Copyright © 2006 voice-system.ro
   Revision History
   Revision $Revision: 5939 $ $Date: 2009-07-21 10:45:05 +0300
                              (Tue, 21 Jul 2009) $
     __________________________________________________________

   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)

        1.4. 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

        1.6. 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 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. handle_publish usage
   1.17. 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",
        "mysql://opensips:opensipsrw@192.168.2.132/opensips")
...

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 value that should be subtracted from the expires value to
   be inserted in the Expires header of 200OK replies for Publish
   and Subscribe messages and expires parameter for Notifies'
   Subscription-Status header. It is used for forcing the client
   cu send an update before the dialog expires.

   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:10.10.10.10:5060")
...

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)
...

1.4. 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 1.16. handle_publish usage
...
        if(is_method("PUBLISH"))
        {
                if($hdr(Sender)!= NULL)
                        handle_publish("$hdr(Sender)");
                else
                        handle_publish();
                t_release();
        }
...

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".
   Ex:
        if(uri =~ "kphone@opensips.org")
                handle_subscribe("1");

   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
...
if(method=="SUBSCRIBE")
    handle_subscribe();
...

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

   Parameters:
     * 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:
                :refreshWatchers:fifo_reply
                sip:11@192.168.2.132
                presence
                1
                _empty_line_

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

   Parameters:none.emphasis>

   MI FIFO Command Format:
                :cleanup:fifo_reply
                _empty_line_

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,
   http://www.opensips.org/html/docs/db/db-schema-devel.html.

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;

}presence_api_t;
...

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 bo
dy for each
         * active watcher (e.g. setting the "version" parameter in an XM
L document.
         * If a module registers the aux_body_processing callback, it ge
ts 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 bod
y, 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_fr
ee_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;

}pres_ev_t;
...

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* bod
y);
..

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)
