XCAP_Client Module

Anca-Maria Vamanu

   Voice Sistem SRL

Edited by

Anca-Maria Vamanu

   Copyright © 2007 Voice Sistem SRL
     __________________________________________________________________

   Table of Contents

   1. Admin Guide

        1. Overview
        2. Dependencies

              2.1. Kamailio Modules
              2.2. External Libraries or Applications

        3. Parameters

              3.1. db_url(str)
              3.2. xcap_table(str)
              3.3. periodical_query(int)
              3.4. query_period(int)

        4. RPC Commands

              4.1. xcap_client.refreshXcapDoc

        5. Remarks

   2. Developer Guide

        1. bind_xcap_api(xcap_api_t* api)
        2. get_elem
        3. register_xcb

   List of Examples

   1.1. Set db_url parameter
   1.2. Set xcap_table parameter
   1.3. Set periodical_query parameter
   1.4. Set query_period parameter
   2.1. xcap_api structure

Chapter 1. Admin Guide

   Table of Contents

   1. Overview
   2. Dependencies

        2.1. Kamailio Modules
        2.2. External Libraries or Applications

   3. Parameters

        3.1. db_url(str)
        3.2. xcap_table(str)
        3.3. periodical_query(int)
        3.4. query_period(int)

   4. RPC Commands

        4.1. xcap_client.refreshXcapDoc

   5. Remarks

1. Overview

   The module is a XCAP client for Kamailio that can be used by other
   modules. It fetches XCAP elements, either documents or part of them, by
   sending HTTP GET requests to an XCAP server. It also offers support for
   conditional queries. It uses the libcurl library as a client-side HTTP
   transfer library.

   The module offers a XCAP client interface with general functions that
   allow requesting for a specific element from a XCAP server. In addition
   to that it also offers the service of storing and updating the
   documents it receives. In this case only an initial request to the
   module is required - xcapGetNewDoc - which is like a request to the
   module to handle from that point on the referenced document so as to
   promise that the newest version will always be present in database.

   The update method is also configurable, either through periodical
   queries, applicable to any kind of XCAP server or with a management
   command that should be sent by the server upon an update.

   The module is currently used by the “presence_xml” module, if the
   'integrated_xcap_server' parameter is not set.

2. Dependencies

   2.1. Kamailio Modules
   2.2. External Libraries or Applications

2.1. Kamailio Modules

   The module is not dependent of any Kamailio module.

2.2. External Libraries or Applications

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

3. Parameters

   3.1. db_url(str)
   3.2. xcap_table(str)
   3.3. periodical_query(int)
   3.4. query_period(int)

3.1. db_url(str)

   The database url.

   Default value is “mysql://kamailio:kamailiorw@localhost/kamailio”.

   Example 1.1. Set db_url parameter
...
modparam("xcap_client", "db_url", "dbdriver://username:password@dbhost/dbname")
...

3.2. xcap_table(str)

   The name of the db table where XCAP documents are stored.

   Default value is “xcap”.

   Example 1.2. Set xcap_table parameter
...
modparam("xcap_client", "xcap_table", "xcaps")
...

3.3. periodical_query(int)

   A flag to disable periodical query as an update method for the
   documents the module is responsible for. It could be disabled when the
   XCAP server is capable to send the exported management command when a
   change occurs or when another module in Kamailio handles updates.

   To disable it set this parameter to 0.

   Default value is “1”.

   Example 1.3. Set periodical_query parameter
...
modparam("xcap_client", "periodical_query", 0)
...

3.4. query_period(int)

   Should be set if periodical query is not disabled. Represents the time
   interval the XCAP servers should be queried for an update.

   To disable it set this parameter to 0.

   Default value is “100”.

   Example 1.4. Set query_period parameter
...
modparam("xcap_client", "query_period", 50)
...

4. RPC Commands

   4.1. xcap_client.refreshXcapDoc

4.1.  xcap_client.refreshXcapDoc

   Management command that should be sent by an XCAP server when a stored
   document changes.

   Name: xcap_client.refreshXcapDoc

   Parameters:
     * document uri: the uri of the document
     * xcap server port: the port of the xcap server

   RPC Command Example:
...
# execute in a single line command
kamcmd xcap_client.refreshXcapDoc
     /xcap-root/resource-lists/users/eyebeam/buddies-resource-list.xml 8000
...

5. Remarks

   Note: libcurl leak in CentOS 6 - this module uses libcurl library and
   in case if you are using CentOS 6, be aware that standard
   libcurl-7.19.7-52 has a memory leak. To fix this memory, install
   libcurl from city-fan repository. More details at:
   https://www.digitalocean.com/community/questions/how-to-upgrade-curl-in
   -centos6

Chapter 2. Developer Guide

   Table of Contents

   1. bind_xcap_api(xcap_api_t* api)
   2. get_elem
   3. register_xcb

   The module exports a number of functions that allow selecting and
   retrieving an element from an xcap server and also registering a
   callback to be called when the management command refreshXcapDoc is
   received and the document in question is retrieved.

1.  bind_xcap_api(xcap_api_t* api)

   This function allows binding the needed functions.

   Example 2.1. xcap_api structure
...
typedef struct xcap_api {

        /* xcap node selection and retrieving functions*/
        xcap_get_elem_t get_elem;
        xcap_nodeSel_init_t int_node_sel;
        xcap_nodeSel_add_step_t add_step;
        xcap_nodeSel_add_terminal_t add_terminal;
        xcap_nodeSel_free_t free_node_sel;
        xcapGetNewDoc_t getNewDoc; /* an initial request for the module
        to fetch this document that does not exist in xcap db table
        and handle its update*/

        /* function to register a callback to document changes*/
        register_xcapcb_t register_xcb;
}xcap_api_t;
...

2.  get_elem

   Field type:
...
typedef char* (*xcap_get_elem_t)(char* xcap_root,
xcap_doc_sel_t* doc_sel, xcap_node_sel_t* node_sel);
...

   This function sends a HTTP request and gets the specified information
   from the xcap server.

   The parameters signification:
     * xcap_root- the XCAP server address;
     * doc_sel- structure with document selection info;
Parameter type:
...
typedef struct xcap_doc_sel
{
        str auid; /* application defined Unique ID*/
        int type; /* the type of the path segment
                                after the AUID  which must either
                                be GLOBAL_TYPE (for "global") or
                                USERS_TYPE (for "users") */
        str xid; /* the XCAP User Identifier
                                if type is USERS_TYPE */
        str filename;
}xcap_doc_sel_t;
...
     * node_sel- structure with node selection info;
Parameter type:
...
typedef struct xcap_node_sel
{
        step_t* steps;
        step_t* last_step;
        int size;
        ns_list_t* ns_list;
        ns_list_t* last_ns;
        int ns_no;

}xcap_node_sel_t;

typedef struct step
{
        str val;
        struct step* next;
}step_t;

typedef struct ns_list
{
        int name;
        str value;
        struct ns_list* next;
}ns_list_t;
...
       The node selector is represented like a list of steps that will be
       represented in the path string separated by '/' signs. The
       namespaces for the nodes are stored also in a list, as an
       association of name and value, where the value is to be included in
       the respective string val field of the step.
       To construct the node structure the following functions in the
       xcap_api structure should be used: 'int_node_sel', 'add_step' and
       if needed, 'add_terminal'.
       If the intention is to retrieve the whole document this argument
       must be NULL.

3.  register_xcb

   Field type:
...
typedef int (*register_xcapcb_t)(int types, xcap_cb f);
...

   - 'types' parameter can have a combined value of PRES_RULES,
   RESOURCE_LIST, RLS_SERVICES and PIDF_MANIPULATION.

   -the callback function has type :
...
typedef int (xcap_cb)(int doc_type, str xid, char* doc);
...
