b2b_logic_admin.xml

<!-- Module User's Guide -->

<chapter>
	
	<title>&adminguide;</title>
	
	<section id="overview" xreflabel="Overview">
	<title>Overview</title>
	<para>
		The B2BUA implementation in OpenSIPS is separated in two layers:
			<itemizedlist>
			<listitem>
		a lower one(coded in b2b_entities module)- which implements the basic functions of a UAS and UAC
			</listitem>
			<listitem>
		an upper one - which represents the logic engine of B2BUA, responsible of actually
			implementing the B2BUA services using the functions offered by the low level.
			</listitem>
	</itemizedlist>
	This module is a B2BUA upper level implementation that can be used with b2b_entities
	module to have B2BUA that can be configured to provide some PBX services.
	The B2B services are coded in an XML scenario document. The b2b_logic module
	examines this document and uses the functions provided by the b2b_entities
	module to achieve the actions specified in the document and enable the service.
	</para>
	<para>
		A scenario can be instantiated in two ways:
		<itemizedlist>
			<listitem>
				from the script - at the receipt of a initial message
			</listitem>
			<listitem>
				with a extern command (MI) command - the server will connect two 
				end points in a session(Third Party Call Control).
			</listitem>
		</itemizedlist>
	</para>
	<para>
	High Availability for B2B sessions can be achieved by enabling the clustering support
	offered by the the lower <emphasis>b2b_entities</emphasis> module (by setting the
	<ulink url="https://opensips.org/docs/modules/3.1.x/b2b_entities.html#param_cluster_id">
	cluster_id</ulink> modparam from <emphasis>b2b_entities</emphasis>).
	</para>
	</section>

	<section id="dependencies" xreflabel="Dependencies">
	<title>Dependencies</title>
	<section>
		<title>&osips; Modules</title>
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>b2b_entities, a db module</emphasis>
			</para>
			</listitem>
			</itemizedlist>
	</section>
	
	<section>
		<title>External Libraries or Applications</title>
		<para>
		The following libraries or applications must be installed before running
		&osips; with this module loaded:
		</para>
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>libxml2-dev</emphasis>
			</para>
			</listitem>
			</itemizedlist>
	</section>
	</section>

	<section id="exported_parameters" xreflabel="Exported Parameters">
		<title>Exported Parameters</title>
	<section id="param_hash_size" xreflabel="hash_size">
		<title><varname>hash_size</varname> (int)</title>
		<para>
			The size of the hash table that stores the scenario instatiation entities.
		</para>
		<para>
		<emphasis>Default value is <quote>9</quote>
		</emphasis>
		 (512 records).
		</para>
		<example>
		<title>Set <varname>server_hsize</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "hash_size", 10)
...
	</programlisting>
		</example>
	</section>

	<section id="param_script_scenario" xreflabel="script_scenario">
		<title><varname>script_scenario</varname> (str)</title>
		<para>
			This parameter should be set with the path of a document
			that contains a scenario that can be instantiated from the
			script at the receipt of an initial message.
		</para>
		<para>
		This parameter can be set more than once.
		</para>
		<example>
		<title>Set <varname>script_scenario</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "script_scenario", "/usr/local/opensips/scripts/b2b_prepaid.xml")
...
	</programlisting>
		</example>
	</section>

	<section id="param_extern_scenario" xreflabel="extern_scenario">
		<title><varname>extern_scenario</varname> (str)</title>
		<para>
			This parameter should be set with the path of a document
			that contains a scenario that can be instantiated with an MI command.
		</para>
		<para>
		This parameter can be set more than once.
		</para>
		<example>
		<title>Set <varname>script_scenario</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "extern_scenario", "/usr/local/opensips/scripts/b2b_marketing.xml")
...
	</programlisting>
		</example>
	</section>

	<section id="param_cleanup_period" xreflabel="cleanup_period">
		<title><varname>cleanup_period</varname> (int)</title>
		<para>
			The time interval at which to search for an hanged b2b context.
			A scenario is considered expired if the duration of a session exceeds the
			lifetime specified in the scenario.
			At that moment, BYE is sent in all the dialogs from that context and the
			context is deleted.
		</para>
		<para>
		<emphasis>Default value is <quote>100</quote>.</emphasis>
		</para>
		<example>
		<title>Set <varname>cleanup_period</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "cleanup_period", 60)
...
	</programlisting>
		</example>
	</section>

	<section id="param_custom_headers_regexp" xreflabel="custom_headers_regexp">
		<title><varname>custom_headers_regexp</varname> (str)</title>
		<para>
		Regexp to search SIP header by names that should be passed
		from the dialog of one side to the other side. There are a number
		of headers that are passed by default. They are: 
		<itemizedlist>
			<listitem>Content-Type</listitem>
			<listitem>Supported</listitem>
			<listitem>Allow</listitem>
			<listitem>Proxy-Require</listitem>
			<listitem>Session-Expires</listitem>
			<listitem>Min-SE</listitem>
			<listitem>Require</listitem>
			<listitem>RSeq</listitem>
		</itemizedlist>
		If you wish some other headers to be passed also you should define them
		by setting this parameter.
		</para>
		<para>
		It can be in forms like "regexp", "/regexp/" and "/regexp/flags".
		</para>
		<para>Meaning of the flags is as follows:</para>
		<itemizedlist>
			<listitem><para>
			<emphasis>i</emphasis> - Case insensitive search.
			</para></listitem>
			<listitem><para>
			<emphasis>e</emphasis> - Use extended regexp.
			</para></listitem>
		</itemizedlist>
		<para>
		<emphasis>Default value is <quote>NULL</quote>.</emphasis>
		</para>
		<example>
		<title>Set <varname></varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "custom_headers_regexp", "/^x-/i")
...
	</programlisting>
		</example>
	</section>

	<section id="param_custom_headers" xreflabel="custom_headers">
		<title><varname>custom_headers</varname> (str)</title>
		<para>
		A list of SIP header names delimited by ';' that should be passed
		from the dialog of one side to the other side. There are a number
		of headers that are passed by default. They are: 
		<itemizedlist>
			<listitem>Max-Forwards (it is decreased by 1)</listitem>
			<listitem>Content-Type</listitem>
			<listitem>Supported</listitem>
			<listitem>Allow</listitem>
			<listitem>Proxy-Require</listitem>
			<listitem>Session-Expires</listitem>
			<listitem>Min-SE</listitem>
			<listitem>Require</listitem>
			<listitem>RSeq</listitem>
		</itemizedlist>
		If you wish some other headers to be passed also you should define them
		by setting this parameter.
		</para>
		<para>
		<emphasis>Default value is <quote>NULL</quote>.</emphasis>
		</para>
		<example>
		<title>Set <varname></varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "custom_headers", "User-Agent;Date")
...
	</programlisting>
		</example>
	</section>

	<section id="param_use_init_sdp" xreflabel="use_init_sdp">
		<title><varname>use_init_sdp</varname> (int)</title>
		<para>
		This parameter modifies the behaviour of the B2BUA when bridging
		and a provisional media uri is set. For playing media while the callee
		answers (that is connecting the caller to a media server), the bridging
		with the callee must start by sending an Invite to it. The correct way
		is to send an Invite without a body in this case, but it has been observed
		that not many gateways support this. So, the solution is to use the sdp
		received in the first Invite from the caller and put it as the body for this
		invite. By setting this parameter, this behavior is enabled.
		You can also set use_init_sdp per scenario and overwrite this global value.
		</para>
		<para>
		<emphasis>Default value is <quote>0</quote>.</emphasis>
		</para>
		<example>
		<title>Set <varname></varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "use_init_sdp", 1)
...
	</programlisting>
		</example>
	</section>
	<section id="param_db_url" xreflabel="db_url">
		<title><varname>db_url</varname> (str)</title>
		<para>
			Database URL.
		</para>
		<example>
		<title>Set <varname>db_url</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "db_url", "mysql://opensips:opensipsrw@127.0.0.1/opensips")
...
	</programlisting>
		</example>
	</section>
	<section id="param_update_period" xreflabel="update_period">
		<title><varname>update_period</varname> (int)</title>
		<para>
			The time interval at which to update the info in database.
		</para>
		<para>
		<emphasis>Default value is <quote>100</quote>.</emphasis>
		</para>
		<example>
		<title>Set <varname>update_period</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "update_period", 60)
...
	</programlisting>
		</example>
	</section>
	<section id="param_max_duration" xreflabel="max_duration">
		<title><varname>max_duration</varname> (int)</title>
		<para>
			The maximum duration of a call.
		</para>
		<para>
		<emphasis>Default value is <quote>12 * 3600 (12 hours)</quote>.</emphasis>
		</para>
		<para>If you set it to 0, there will be no limitation.</para>
		<example>
		<title>Set <varname>max_duration</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "max_duration", 7200)
...
	</programlisting>
		</example>
	</section>

	<section id="param_b2bl_from_spec_param" xreflabel="b2bl_from_spec_param">
		<title><varname>b2bl_from_spec_param</varname> (string)</title>
		<para>
			The name of the pseudo variable for storing the new
			<quote>From</quote> header.
			The PV must be set before calling <quote>b2b_init_request</quote>.
		</para>
		<para>
		<emphasis>Default value is <quote>NULL</quote> (disabled).</emphasis>
		</para>
		<example>
		<title>Set <varname>b2bl_from_spec_param</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "b2bl_from_spec_param", "$var(b2bl_from)")
...
route{
	...
	# setting the From header
	$var(b2bl_from) = "\"Call ID\" &lt;sip:user@opensips.org&gt;";
	...
	b2b_init_request("top hiding");
	...
}
	</programlisting>
		</example>
	</section>

	<section id="param_server_address" xreflabel="server_address">
		<title><varname>server_address</varname> (str)</title>
		<para>
			The IP address of the machine that will be used as Contact in
			the generated messages. This is compulsory only when using external
			scenarios. For the script scenarios, if it is not set, it is constructed
			dynamically from the socket where the initiating request was received.
			This socket will be used to send all the requests, replies for that
			scenario instantiation.
		</para>
		<example>
		<title>Set <varname>server_address</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "server_address", "sip:sa@10.10.10.10:5060")
...
	</programlisting>
		</example>
	</section>

	<section id="param_init_callid_hdr" xreflabel="init_callid_hdr">
		<title><varname>init_callid_hdr</varname> (str)</title>
		<para>
			The module offers the possibility to insert the original callid in a header
			in the generated Invites. If you want this, set this parameter to the name
			of the header in which to insert the original callid.
		</para>
		<example>
		<title>Set <varname>init_callid_hdr</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "init_callid_hdr", "Init-CallID")
...
	</programlisting>
		</example>
	</section>
	<section id="param_db_mode" xreflabel="db_mode">
		<title><varname>db_mode</varname> (int)</title>
		<para>
			The B2B modules have support for the 3 type of database storage
		</para>
		<para>
		<itemizedlist>
				<listitem>NO DB STORAGE - set this parameter to 0</listitem>
				<listitem>WRITE THROUGH (synchronous write in database) - set this parameter to 1</listitem>
				<listitem>WRITE BACK (update in db from time to time) - set this parameter to 2</listitem>
		</itemizedlist>
		</para>
		<para>
		<emphasis>Default value is <quote>2</quote> (WRITE BACK).</emphasis>
		</para>
		<example>
		<title>Set <varname>db_mode</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "db_mode", 1)
...
	</programlisting>
		</example>
	</section>

	<section id="param_db_table" xreflabel="db_table">
		<title><varname>db_table</varname> (str)</title>
		<para>
			Name of the database table to be used
		</para>
		<para>
		<emphasis>Default value is <quote>b2b_logic</quote> </emphasis>
		</para>
		<example>
		<title>Set <varname>db_table</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "db_table", "some_table_name")
...
	</programlisting>
		</example>
	</section>

	<section id="param_b2bl_th_init_timeout" xreflabel="b2bl_th_init_timeout">
		<title><varname>b2bl_th_init_timeout</varname> (int)</title>
		<para>
			Call setup timeout for topology hiding scenario.
		</para>
		<para>
		<emphasis>Default value is <quote>60</quote> </emphasis>
		</para>
		<example>
		<title>Set <varname>b2bl_th_init_timeout</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("b2b_logic", "b2bl_th_init_timeout", 60)
...
	</programlisting>
		</example>
	</section>

	</section>

	<section id="exported_functions" xreflabel="exported_functions">
		<title>Exported Functions</title>
	<section id="func_b2b_init_request" xreflabel="b2b_init_request()">
		<title>
		<function moreinfo="none">b2b_init_request(flags, [scenario_param1],
			[scenario_param2], [scenario_param3], [scenario_param4])</function>
		</title>
		<para>
			This is the function that must be called by the script writer
			on an initial INVITE for which a B2B scenario must be instantiated.
			It is up to the script writer to decide which are the criteria to decide
			for which messages certain scenarios must be instantiated.
		</para>
		<para>
			The first parameter is the identifier for the scenario and possible flags.
			This is defined in the XML document as an attribute of the root node
			or "top hiding" for internal topology hiding scenario.
			It can be passed as "scenario" or "scenario_name/flags".
			Then it can take at most 4 other parameters that represent the parameters for
			the xml scenario. The expected number of parameters is also specified as an attribute
			in the root node of the XML scenario.
		</para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem><para>
				<emphasis>flags (string)</emphasis> - meaning of the flags is as follows:
				<itemizedlist>
					<listitem><para>
					<emphasis>t[nn]</emphasis> -  Call setup timeout for topology hiding scenario.
					Example: t300.
					</para></listitem>
					<listitem><para>
					<emphasis>a</emphasis> -  Transparent authentication. In this mode b2b passes your 401
					or 407 authentication request to destination server.
					</para></listitem>
					<listitem><para>
					<emphasis>p</emphasis> -  Preserve To: header.
					</para></listitem>
				</itemizedlist>
			</para></listitem>
			<listitem><para>
				<emphasis>scenario_param1 (string, optional)</emphasis>
			</para></listitem>
			<listitem><para>
				<emphasis>scenario_param2 (string, optional)</emphasis>
			</para></listitem>
			<listitem><para>
				<emphasis>scenario_param3 (string, optional)</emphasis>
			</para></listitem>
			<listitem><para>
				<emphasis>scenario_param4 (string, optional)</emphasis>
			</para></listitem>
		</itemizedlist>
	<note><para>
		If you have a multi interface setup and want to chance the outbound interface,
		it is mandatory to use the "force_send_socket()" core function before passing
		control to b2b function. If you do not do it, the requests may be correctly routed,
		but the SIP pacakge may be invalid (as Contact, Via, etc).
	</para></note>
		<example>
			<title><function>b2b_init_request</function> usage</title>
		<programlisting format="linespecific">
...
if(is_method("INVITE") &amp;&amp; !has_totag() &amp;&amp; prepaid_user())
   b2b_init_request("prepaid", "sip:320@opensips.org:5070",
      "sip:321@opensips.org:5070"));
...
	</programlisting>
		</example>
	</section>
	<section id="func_b2b_bridge_request" xreflabel="b2b_bridge_request()">
		<title>
		<function moreinfo="none">b2b_bridge_request(b2bl_key,entity_no)</function>
		</title>
		<para>
			This function will bridge an initial INVITE with one of the
			particapnts from an existing b2b dialog.
		</para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem><para>
				<emphasis>b2bl_key (string)</emphasis> - a string that
				contains the b2b_logic key. The key can also be in the form
				of <emphasis>callid;from-tag;to-tag</emphasis>.
			</para></listitem>
			<listitem><para>
				<emphasis>entity_no (int)</emphasis> - an integer that
				holds the entity of the entity/participant to bridge.
			</para></listitem>
		</itemizedlist>
		<example>
			<title><function>b2b_bridge_request</function> usage</title>
		<programlisting format="linespecific">
...
modparam("b2b_entities", "script_req_route", "b2b_request")
...
route[b2b_request]
{
   # incoming requests from the B2B entities
   ...
   if ($ci~="^B2B") { #keep this aligned with b2b_key_prefix
      # request coming from the UAC side;
      # the Call-ID carries the B2B key ID
      if (is_method("BYE") {
         $var(entity) = 1;
         b2b_bridge_request($ci,$var(entity));
      }
   }
   ...
}
...
		</programlisting>
		</example>
	</section>

</section>

<section id="exported_mi_functions" xreflabel="Exported MI Functions">
	<title>Exported MI Functions</title>
	<section id="mi_b2b_trigger_scenario" xreflabel="b2b_trigger_scenario">
		<title>
		<function moreinfo="none">b2b_trigger_scenario</function>
		</title>
		<para>
		This command instantiates a B2B scenario.
		</para>
		<para>
		Name: <emphasis>b2b_trigger_scenario</emphasis>
		</para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem>
				<para><emphasis>senario_id</emphasis> : the id of the scenario to be instantiated.
				</para>
			</listitem>
			<listitem>
				<para><emphasis>scenario_params</emphasis> - array of at least 2 scenario parameters</para>
			</listitem>
		</itemizedlist>
		<para>
		MI FIFO Command Format:
		</para>
	<programlisting  format="linespecific">
	opensips-cli -x mi b2b_trigger_scenario marketing sip:bob@opensips.org sip:322@opensips.org:5070 sip:alice@opensips.org
		</programlisting>
	</section>

	<section id="mi_b2b_bridge" xreflabel="b2b_bridge">
		<title>
		<function moreinfo="none">b2b_bridge</function>
		</title>
		<para>
			This command can be used by an external application to tell B2BUA to bridge a
			call party from an on going dialog to another destination. By default the caller
			is bridged to the new uri and BYE is set to the callee. You can instead bridge
			the callee if you send 1 as the third parameter.
		</para>
		<para>
		Name: <emphasis>b2b_bridge</emphasis>
		</para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem>
				<para><emphasis>dialog_id</emphasis> : the <emphasis>b2b_logic key</emphasis>, or the
				<emphasis>callid;from-tag;to-tag</emphasis> of the ongoing dialog.
				</para>
			</listitem>
			<listitem>
				<para><emphasis>new_uri</emphasis> - the uri of the new destination</para>
			</listitem>
			<listitem>
				<para><emphasis>flag</emphasis> (optional) - used to specify that the callee must be bridged to the new destination. If not present the caller will be bridged. Possible values are
				'0' or '1'.</para>
			</listitem>
			<listitem>
				<para><emphasis>prov_media_uri</emphasis> (optional) - the uri of a media server able to play 
					provisional media starting from the beginning of the bridging scenario
					to the end of it. It is optional. If not present, no other entity will be
					envolved in the bridging scenario</para>
			</listitem>
		</itemizedlist>
		<para>MI FIFO Command Format:</para>
	<programlisting  format="linespecific">
	opensips-cli -x mi b2b_bridge 1020.30 sip:alice@opensips.org
	</programlisting>
		<para>opensips-cli Command Format:</para>
	<programlisting  format="linespecific">
	opensips-cli -x mi b2b_bridge 1020.30 sip:alice@opensips.org
	</programlisting>
	</section>

	<section id="mi_b2b_list" xreflabel="b2b_list">
		<title>
		<function moreinfo="none">b2b_list</function>
		</title>
		<para>
			This command can be used to list the internals of b2b_logic entities.
		</para>
		<para>
		Name: <emphasis>b2b_list</emphasis>
		</para>
		<para>Parameters: <emphasis>none</emphasis></para>
		<itemizedlist>
		</itemizedlist>
		<para>MI FIFO Command Format:</para>
	<programlisting  format="linespecific">
	opensips-cli -x mi b2b_list
	</programlisting>
	</section>

	<section id="mi_b2b_terminate_call" xreflabel="b2b_terminate_call">
		<title>
		<function moreinfo="none">b2b_terminate_call</function>
		</title>
		<para>
			Terminates an ongoing B2B session.
		</para>
		<para>
		Name: <emphasis>b2b_terminate_call</emphasis>
		</para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem>
				<para><emphasis>key</emphasis> : the <emphasis>b2b_logic key</emphasis>
				or the <emphasis>callid;from-tag;to-tag</emphasis> of
				one of call legs of the ongoing session.
				</para>
			</listitem>
		</itemizedlist>
		<para>MI FIFO Command Format:</para>
	<programlisting  format="linespecific">
	opensips-cli -x mi b2b_terminate_call 159.0
	</programlisting>
	</section>

</section>

<section id="exported_pseudo_variables">
	<title>Exported Pseudo-Variables</title>

	<section id="b2b_logic.key" xreflabel="$b2b_logic.key">
	<title>
		<varname>$b2b_logic.key</varname>
	</title>
	<para>
		This is a read-only variable that returns the b2b_logic key of the
		ongoing B2B session.
	</para>
	<para>
		The variable can be used in request route, local_route
		and in the custom B2B request and reply routes defined through the
		<emphasis>b2b_entities</emphasis> module.
	</para>
	<example>
	<title><varname>$b2b_logic.key</varname> usage</title>
	<programlisting format="linespecific">
...
local_route {
   ...
   if ($b2b_logic.key) {
      xlog("request belongs to B2B session: $b2b_logic.key\n");
      ...
   }
   ...
}
...
	</programlisting>
	</example>
	</section>

	<section id="b2b_logic.entity" xreflabel="$b2b_logic.entity">
	<title>
		<varname>$b2b_logic.entity(field)[idx]</varname>
	</title>
	<para>
		This is a read-only variable that returns information about the
		entities(dialogs) involved in the ongoing B2B session.
	</para>
	<para>
		The available entity information is:
		<itemizedlist>
			<listitem><para>
				the Call-ID of the dialog, accessible by using the
				<emphasis>callid</emphasis> subname;
			</para></listitem>
			<listitem><para>
				the entity key, accessible by using the
				<emphasis>key</emphasis> subname or no subname at all.
			</para></listitem>
		</itemizedlist>
	</para>
	<para>
		The index is used to select which entity from the B2B session to refer
		to. The only possible values are <emphasis>0</emphasis> or <emphasis>1
		</emphasis> and correspond to the positions of the entities
		in the scenario. Initially, this depends on the order of the entities in
		the <emphasis>init</emphasis> section of the scenario file. In the case
		of the internal topology hiding scenario, <emphasis>0</emphasis> is the
		caller and <emphasis>1</emphasis> is the callee. When a further bridge
		action happens, the bridged entity is always placed on the <emphasis>0
		</emphasis> index and the new entity on <emphasis>1</emphasis>.
	</para>
	<para>
		If no index is provided, the variable will refer to the entity(dialog)
		which the current SIP message belongs to.
	</para>
	<para>
		The variable can be used in request route, local_route
		and in the custom B2B request and reply routes defined through the
		<emphasis>b2b_entities</emphasis> module.
	</para>
	<example>
	<title><varname>$b2b_logic.entity</varname> usage</title>
	<programlisting format="linespecific">
...
modparam("b2b_entities", "script_request_route", "b2b_request")
...
route[b2b_request] {
   ...
   xlog("received request for entity: $b2b_logic.entity\n");
   ...
   if ($rm == "BYE" &amp;&amp; $b2b_logic.entity == $(b2b_logic.entity[1]))
      xlog("Disconnecting callee\n")
   ...
}
...
	</programlisting>
	</example>
	</section>

	<section id="b2b_logic.ctx" xreflabel="$b2b_logic.ctx">
	<title>
		<varname>$b2b_logic.ctx(key)</varname>
	</title>
	<para>
		This is a read-write variable that provides access to a custom
		Key-Value storage(of string values) in the context of the ongoing
		B2B session.
	</para>
	<para>
		The variable can be used in request route, local_route
		and in the custom B2B request and reply routes defined through the
		<emphasis>b2b_entities</emphasis> module. In the main request route
		the variable can be used for storing a new context value even before
		instantiating the scenario with <emphasis>b2b_init_request()</emphasis>.
	</para>
	<para>
		Setting the variable to <emphasis>NULL</emphasis> will delete the value
		at the given key.
	</para>
	<example>
	<title><varname>$b2b_logic.ctx</varname> usage</title>
	<programlisting format="linespecific">
...
modparam("b2b_entities", "script_reply_route", "b2b_reply")
...
route {
   ...
   b2b_init_request("prepaid", "sip:alice@127.0.0.1");

   $b2b_logic.ctx(my_extra_info) = "my_value";
   ...
}
...
route[b2b_reply] {
   ...
   xlog("my info: $b2b_logic.ctx(my_extra_info)\n");
   ...
}
...
	</programlisting>
	</example>
	</section>

</section>

</chapter>