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

<chapter>
	<chapterinfo>
	<revhistory>
		<revision>
		<revnumber>$Revision: 1827 $</revnumber>
		<date>$Date: 2007-03-12 17:22:53 +0200 (Mon, 12 Mar 2007) $</date>
		</revision>
	</revhistory>
	</chapterinfo>
	<title>User's Guide</title>
	
	<section>
	<title>Overview</title>
	<para>The module contains record routing logic</para>
	</section>


	<section id="RR-dialog-id">
	<title>Dialog support</title>
	<para>&ser; is basically <emphasis>only</emphasis> a transaction statefull 
	proxy, without any dialog support build in. There are many features/services
	which actually requires a dialog awareness, like storing the information in 
	the dialog creation stage, information which will be used during the whole 
	dialog existence.
	</para>
	<para>
	The most urging example is NAT traversal, in dealing with the within the 
	dialog INVITEs (re-INVITEs). When processing the initial INVITE, the proxy 
	detects if the caller or callee is behind some NAT and fixes the signalling 
	and media parts - since not all the detection mechanism are available for 
	within the dialog requests (like usrloc), to be able to fix correspondingly 
	the sequential requests, the proxy must remember that the original request 
	was NAT processed. There are many other cases where dialog awareness fixes 
	or helps.
	</para>
	<para>
	The solution is to store additional dialog-related information in the 
	routing set (Record-Route/Route headers), headers which show up in all 
	sequential requests. So any information added to the Record-Route header
	will be found (with no direction dependencies) in Route header 
	(corresponding to the proxy address).
	</para>
	<para>
	As storage container, the parameters of the Record-Route / Route header
	will be used - Record-Route parameters mirroring are reinforced by 
	RFC 3261 (see 12.1.1 UAS behavior).
	</para>
	<para>
	For this purpose, the modules offers the following functions:
	</para>
	<itemizedlist>
		<listitem>
			<para>add_rr_param() - see <xref linkend="add-rr-param-id">
			</para>
		</listitem>
		<listitem>
			<para>check_route_param() - see 
				<xref linkend="check-route-param-id">
			</para>
		</listitem>
	</itemizedlist>
	<example>
		<title>Dialog support in RR module</title>
		<programlisting format="linespecific">
  
UAC                       OpenSER PROXY                          UAS

---- INVITE ------&gt;       record_route()          ----- INVITE ----&gt;
                     add_rr_param(";foo=true")

--- reINVITE -----&gt;        loose_route()          ---- reINVITE ---&gt;
                    check_route_param(";foo=true")

&lt;-- reINVITE ------        loose_route()          &lt;--- reINVITE ----
                    check_route_param(";foo=true")

&lt;------ BYE -------        loose_route()          &lt;----- BYE -------
                    check_route_param(";foo=true")
  
</programlisting>
		</example>
	</section>


	<section>
	<title>Dependencies</title>
	<section>
		<title>&ser; Modules</title>
		<para>
		The following modules must be loaded before this module:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>No dependencies on other &ser; modules</emphasis>.
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>

	<section>
		<title>External Libraries or Applications</title>
		<para>
		The following libraries or applications must be installed before running
		&ser; with this module loaded:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>None</emphasis>.
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>
	</section>


	<section>
	<title>Exported Parameters</title>
	<section>
		<title><varname>enable_full_lr</varname> (integer)</title>
		<para>
		If set to 1 then <quote>;lr=on</quote> instead of just 
		<quote>;lr</quote> will be used. This is to overcome problems with 
		broken &ua;s which strip <quote>;lr</quote> parameter when generating 
		Route header fields from Record-Route (<quote>;lr=on</quote> seems 
		to help).
		</para>
		<para>
		<emphasis>
			Default value is 0 (no).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>enable_full_lr</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rr", "enable_full_lr", 1)
...
</programlisting>
		</example>
	</section>

	<section id="append-fromtag-id">
		<title><varname>append_fromtag</varname> (integer)</title>
		<para>
		If turned on, request's from-tag is appended to record-route; that's 
		useful for understanding whether subsequent requests (such as BYE) come 
		from caller (route's from-tag==BYE's from-tag) or callee 
		(route's from-tag==BYE's to-tag)
		</para>
		<para>
		<emphasis>
			Default value is 1 (yes).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>append_fromtag</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rr", "append_fromtag", 0)
...
</programlisting>
		</example>
	</section>

	<section>
		<title><varname>enable_double_rr</varname> (integer)</title>
		<para>
		There are some situations when the server needs to insert two 
		Record-Route header fields instead of one. For example when using 
		two disconnected networks or doing cross-protocol forwarding from 
		UDP->TCP. This parameter enables inserting of 2
		Record-Routes. The server will later remove both of them.
		</para>
		<para>
		<emphasis>
			Default value is 1 (yes).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>enable_double_rr</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rr", "enable_double_rr", 0)
...
</programlisting>
		</example>
	</section>

	<section>
		<title><varname>add_username</varname> (integer)</title>
		<para>
		If set to a non 0 value (which means yes), the username part will
		be also added in the Record-Route URI.
		</para>
		<para>
		<emphasis>
			Default value is 0 (no).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>add_username</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("rr", "add_username", 1)
...
</programlisting>
		</example>
	</section>
	</section>


	<section>
	<title>Exported Functions</title>
	<section id="loose-route-id">
		<title>
		<function moreinfo="none">loose_route()</function>
		</title>
		<para>
		The function performs routing of SIP requests which contain a route 
		set. The name is a little bit confusing, as this function also routes 
		requests which are in the <quote>strict router</quote> format.
		</para>
		<para>
		This function is usually used to route in-dialog requests (like ACK, 
		BYE, reINVITE). Nevertheless also out-of-dialog requests can have a 
		<quote>pre-loaded route set</quote> and my be routed with loose_route. 
		It also takes care of translating between strict-routers and 
		loose-router.
		</para>
		<para>
		The loose_route function analyzes the Route: headers in the requests. 
		If there is no Route: header, the function returns FALSE and routing 
		should be done with normal lookup functions. If a Route: header is 
		found, the function returns 1 and behaves as described in section 
		16.12 of RFC 3261. There is only one exception: If the request is 
		out-of-dialog (no to-tag) and there is only one Route: header 
		indicating the local proxy, then the Route: header is removed and 
		the function returns FALSE.
		</para>
		<para>
		Make sure your loose_routing function can't be used by attackers to 
		bypass proxy authorization.
		</para>
		<para>
		The loose_routing topic is very complex. See the RFC3261 for more 
		details (grep for <quote>route set</quote> is a good starting point in 
		this comprehensive RFC).
		</para>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>loose_route</function> usage</title>
		<programlisting format="linespecific">
...
loose_route();
...
</programlisting>
		</example>
	</section>

	<section id="record-route-id">
		<title>
		<function moreinfo="none">record_route()</function> and 
		<function moreinfo="none">record_route(string)</function>
		</title>
		<para>
		The function adds a new Record-Route header field. The header field 
		will be inserted in the message before any other Record-Route header 
		fields.
		</para>
		<para>
		If any string is passed as parameter, it will be appended as URI
		parameter to the Record-Route header. The string must follow the 
		<quote>;name=value</quote> scheme and it may contain pseudo-variables.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, BRANCH_ROUTE and 
		FAILURE_ROUTE.
		</para>
		<example>
		<title><function>record_route</function> usage</title>
		<programlisting format="linespecific">
...
record_route();
...
</programlisting>
		</example>
	</section>

	<section>
		<title>
		<function moreinfo="none">record_route_preset(string)</function>
		</title>
		<para>
		This function will put the string into Record-Route, don't use 
		unless you know what you are doing.
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
		<listitem>
			<para>
			<emphasis>string</emphasis> - String to be inserted into the 
				header field; it may contain pseudo-variables.
			</para>
		</listitem>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE, BRANCH_ROUTE and 
		FAILURE_ROUTE.
		</para>
		<example>
		<title><function>record_route_preset</function> usage</title>
		<programlisting format="linespecific">
...
record_route_preset("1.2.3.4:5090");
...
</programlisting>
		</example>
	</section>

	<section id="add-rr-param-id">
		<title>
		<function moreinfo="none">add_rr_param(param)</function>
		</title>
		<para>
		Adds a parameter to the Record-Route URI (param must be in 
		<quote>;name=value</quote> format. The function may be called also 
		before or after the record_route() call 
		(see <xref linkend="record-route-id">).
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
		<listitem>
			<para>
			<emphasis>param</emphasis> - String containing the URI parameter to
			be added. It must follow the <quote>;name=value</quote> scheme; it 
			may contain pseudo-variables.
			</para>
		</listitem>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE, BRANCH_ROUTE and 
		FAILURE_ROUTE.
		</para>
		<example>
		<title><function>add_rr_param</function> usage</title>
		<programlisting format="linespecific">
...
add_rr_param(";nat=yes");
...
</programlisting>
		</example>
	</section>

	<section id="check-route-param-id">
		<title>
		<function moreinfo="none">check_route_param(re)</function>
		</title>
		<para>The function checks if the URI parameters of the local Route 
		header (corresponding to the local server) matches the given regular 
		expression. It must be call after loose_route() 
		(see <xref linkend="loose-route-id">).
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
		<listitem>
			<para>
			<emphasis>re</emphasis> - regular expression to check against the
			Route URI parameters.
			</para>
		</listitem>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>check_route_param</function> usage</title>
		<programlisting format="linespecific">
...
if (check_route_param("nat=yes")) {
    setflag(6);
}
...
</programlisting>
		</example>
	</section>

	<section>
		<title>
		<function moreinfo="none">is_direction(dir)</function>
		</title>
		<para>The function checks the flow direction of the request.
		As for checking it's used the <quote>ftag</quote> Route header 
		parameter, the append_fromtag (see <xref linkend="append-fromtag-id"> 
		module parameter must be enables. Also this must be call only after 
		loose_route() (see <xref linkend="loose-route-id">).
		</para>
		<para>
		The function returns true if the <quote>dir</quote> is the same with
		the request's flow direction.
		</para>
		<para>
		The <quote>downstream</quote> (UAC to UAS) direction is relative to the
		initial request that created the dialog.
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
		<listitem>
			<para>
			<emphasis>dir</emphasis> - string containing the direction to be 
				checked. It may be <quote>upstream</quote> (from UAS to UAC) or 
				<quote>downstream</quote> (UAC to UAS).
			</para>
		</listitem>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>check_route_param</function> usage</title>
		<programlisting format="linespecific">
...
if (is_direction("upstream")) {
    xdbg("upstream request ($rm)\n");
}
...
</programlisting>
		</example>
	</section>




	</section>
</chapter>

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