src/modules/nathelper/doc/nathelper_admin.xml
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 <!-- Module User's Guide -->
 
 <chapter>
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 	<title>&adminguide;</title>
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 	<section>
 	<title>Overview</title>
 	<para>
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 		This is a module to help with &nat; traversal and reuse
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 		of <acronym>TCP</acronym> connections. In particular,
 		it helps symmetric &ua;s that don't advertise they are symmetric
 		and are not able to determine their public address.
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 	</para>
 	<para>
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 		The function <function>fix_nated_contact()</function> rewrites the <quote>Contact</quote>
 		header field with request's source address:port pair. The function
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 		<function>fix_nated_sdp()</function> adds the active direction indication
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 		to &sdp; (flag 0x01) and updates the source &ip; address too (flag 0x02). The function
 		<function>fix_nated_register()</function> exports exports the request's source
 		address:port into an AVP to be used during <function>save()</function> and should
 		be used for <quote>REGISTER</quote> requests.
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 	</para>
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         <para>
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 		Note: <function>fix_nated_contact</function> changes the <quote>Contact</quote>
 		header, thus it breaks the RFC. Although usually this is not an issue, it may
 		cause problems with strict SIP clients.  An alternative is to use
 		<function>add_contact_alias()</function> that together with
 		the <function>handle_ruri_alias()</function> is standards conforming and also
 		supports reuse of TCP/TLS connections.
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 	</para>
 	</section>
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 	<section>
 	<title>NAT pinging types</title>
 	<para>
 		Currently, the nathelper module supports two types of NAT pings:
 	</para>
 	<itemizedlist>
 		<listitem>
 			<para>
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 			<emphasis>UDP packet</emphasis> - 4 bytes (zero filled) UDP 
 			packets are sent to the contact address.
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 			</para>
 			<itemizedlist>
 				<listitem>
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 				<para><emphasis>Advantages:</emphasis> low bandwidth traffic,
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 				easy to generate by &kamailio;;
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 				</para>
 				</listitem>
 				<listitem>
 				<para><emphasis>Disadvantages:</emphasis> unidirectional 
 				traffic through NAT (inbound - from outside to inside); As 
 				many NATs do update the bind timeout only on outbound traffic,
 				the bind may expire and closed.
 				</para>
 				</listitem>
 			</itemizedlist>
 		</listitem>
 		<listitem>
 			<para>
 			<emphasis>SIP request</emphasis> - a stateless SIP request is 
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 			sent to the UDP contact address.
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 			</para>
 			<itemizedlist>
 				<listitem>
 				<para><emphasis>Advantages:</emphasis> bidirectional traffic
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 				through NAT, since each PING request from &kamailio; (inbound 
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 				traffic) will force the SIP client to generate a SIP reply 
 				(outbound traffic) - the NAT bind will be surely kept open.
 				</para>
 				</listitem>
 				<listitem>
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 				<para><emphasis>Disadvantages:</emphasis> higher bandwidth 
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 				traffic, more expensive (as time) to generate by &kamailio;;
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 				</para>
 				</listitem>
 			</itemizedlist>
 		</listitem>
 	</itemizedlist>
 	</section>
 
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 	<section>
 	<title>Dependencies</title>
 	<section>
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 		<title>&kamailio; Modules</title>
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 		<para>
 		The following modules must be loaded before this module:
 			<itemizedlist>
 			<listitem>
 			<para>
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 				<emphasis>usrloc</emphasis> module - only if the NATed 
 				contacts are to be pinged.
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 			</para>
 			</listitem>
 			</itemizedlist>
 		</para>
 	</section>
 	<section>
 		<title>External Libraries or Applications</title>
 		<para>
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 		The following libraries or applications must be installed before 
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 		running &kamailio; with this module loaded:
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 			<itemizedlist>
 			<listitem>
 			<para>
 				<emphasis>None</emphasis>.
 			</para>
 			</listitem>
 			</itemizedlist>
 		</para>
 	</section>
 	</section>
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 	<section>
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 	<title>Parameters</title>
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 	<section id="nathelper.p.force_socket">
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 		<title><varname>force_socket</varname> (string)</title>
 		<para>
 		Socket to be used when sending NAT pings for UDP communication.
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 		If no one specified, the OS will choose a socket.
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 		</para>
 		<para>
 		<emphasis>
 			Default value is <quote>NULL</quote>.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>force_socket</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
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 modparam("nathelper", "force_socket", "127.0.0.1:5060")
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 ...
 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.natping_interval">
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 		<title><varname>natping_interval</varname> (integer)</title>
 		<para>
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 		Period of time in seconds between sending the NAT pings to all 
 		currently registered &ua;s to keep their &nat; bindings alive. 
 		Value of 0 disables this functionality.
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 		</para>
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 		<note><para>
 		Enabling the NAT pinging functionality will force the module to
 		bind itself to USRLOC module.
 		</para></note>
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 		<para>
 		<emphasis>
 			Default value is 0.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>natping_interval</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "natping_interval", 10)
 ...
 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.ping_nated_only">
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 		<title><varname>ping_nated_only</varname> (integer)</title>
 		<para>
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 		If this parameter is set to 1 then only contacts that have
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 		the behind NAT <quote>nat_bflag</quote> flag in user location
 		database set will get ping.
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 		</para>
 		<para>
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 		If it is 0 and sipping_bflag is not set, then the 4-bytes UDP ping
 		is sent to all contacts. If it is 0 and sipping_bflag parameter
 		is set, then SIP-request-based pinging is sent to all contacts.
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 		</para>
 		<para>
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 		<emphasis>
 			Default value is 0.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>ping_nated_only</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "ping_nated_only", 1)
 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.natping_processes">
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 		<title><varname>natping_processes</varname> (integer)</title>
 		<para>
 		How many timer processes should be created by the module for the
 		exclusive task of sending the NAT pings.
 		</para>
 		<para>
 		<emphasis>
 			Default value is 1.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>natping_processes</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "natping_processes", 3)
 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.natping_socket">
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 		<title><varname>natping_socket</varname> (string)</title>
 		<para>
 		Spoof the natping's source-ip to this address. Works only for IPv4.
 		</para>
 		<para>
 		<emphasis>
 			Default value is NULL.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>natping_socket</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "natping_socket", "192.168.1.1:5006")
 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.received_avp">
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 		<title><varname>received_avp</varname> (str)</title>
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 		<para>
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 		The name of the Attribute-Value-Pair (AVP) used to store the URI 
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 		containing the received IP, port, and protocol. The URI is created 
 		by fix_nated_register function of nathelper module and the attribute 
 		is then used by the registrar to store the received parameters. Do 
 		not forget to change the value of corresponding parameter in
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 		registrar module if you change the value of this parameter.
 		</para>
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 		<note>
 		<para>
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 		You must set this parameter if you use <function>fix_nated_register</function>. In such
 		case you must set the parameter with same name in the <quote>registrar</quote>
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 		module to same value.
 		</para>
 		</note>
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 		<para>
 		<emphasis>
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 			Default value is "NULL" (disabled).
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 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>received_avp</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
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 modparam("nathelper", "received_avp", "$avp(i:42)")
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 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.sipping_bflag">
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 		<title><varname>sipping_bflag</varname> (integer)</title>
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 		<para>
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 		Which branch flag should be used by the module to identify NATed 
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 		contacts for which it should perform NAT ping via a SIP request 
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 		instead of dummy UDP packet.
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 		</para>
 		<para>
 		<emphasis>
 			Default value is -1 (disabled).
 		</emphasis>
 		</para>
 		<example>
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 		<title>Set <varname>sipping_bflag</varname> parameter</title>
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 		<programlisting format="linespecific">
 ...
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 modparam("nathelper", "sipping_bflag", 7)
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 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.sipping_from">
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 		<title><varname>sipping_from</varname> (string)</title>
 		<para>
 		The parameter sets the SIP URI to be used in generating the SIP
 		requests for NAT ping purposes. To enable the SIP request pinging
 		feature, you have to set this parameter. The SIP request pinging 
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 		will be used only for requests marked so.
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 		</para>
 		<para>
 		<emphasis>
 			Default value is <quote>NULL</quote>.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>sipping_from</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "sipping_from", "sip:pinger@siphub.net")
 ...
 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.sipping_method">
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 		<title><varname>sipping_method</varname> (string)</title>
 		<para>
 		The parameter sets the SIP method to be used in generating the SIP
 		requests for NAT ping purposes.
 		</para>
 		<para>
 		<emphasis>
 			Default value is <quote>OPTIONS</quote>.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>sipping_method</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "sipping_method", "INFO")
 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.natping_disable_bflag">
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 		<title><varname>natping_disable_bflag</varname> (integer)</title>
 		<para>
 		What branch flag should be used by the module to disable NAT pings
 		on a per-registration basis. If the given flag is set for a
 		particular registration, then no NAT pings will be sent at all,
 		regardless of any other conditions.
 		</para>
 		<para>
 		<emphasis>
 			Default value is -1 (disabled).
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>natping_disable_bflag</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "natping_disable_bflag", 8)
 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.nortpproxy_str">
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 		<title><varname>nortpproxy_str</varname> (string)</title>
 		<para>
 		The parameter sets the SDP attribute used by nathelper to mark
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 		the packet SDP that information have already been mangled.
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 		</para>
 		<para>
 		If empty string, no marker will be added or checked.
 		</para>
 		<note><para>
 		The string must be a complete SDP line, including the EOH (\r\n).
 		</para></note>
 		<para>
 		<emphasis>
 			Default value is <quote>a=nortpproxy:yes\r\n</quote>.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>nortpproxy_str</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "nortpproxy_str", "a=sdpmangled:yes\r\n")
 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.keepalive_timeout">
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 		<title><varname>keepalive_timeout</varname> (int)</title>
 		<para>
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 		The parameter sets the interval in seconds after which a natted
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 		contact is removed from location table if it does not reply to SIP
 		keepalives (usually OPTIONS ping requests).
 		</para>
 		<para>
 		The features is available only for UDP contacts that are stored in memory
 		(not working for db only mode for usrloc module).
 		</para>
 		<para>
 		Keepalives are sent stateless, not using TM module. The value of this
 		parameter has to be few times higher than natping_interval.
 		</para>
 		<para>
 		<emphasis>
 			Default value is <quote>0</quote> (feature disabled).
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>keepalive_timeout</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "keepalive_timeout", 120)
 ...
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 </programlisting>
 		</example>
 	</section>
 	<section id="nathelper.p.udpping_from_path">
 		<title><varname>udpping_from_path</varname> (int)</title>
 		<para>
 		Enable sending UDP pings (keepalives) using raw socket from Path
 		address.
 		</para>
 		<para>
 		<emphasis>
 			Default value is <quote>0</quote> (feature disabled).
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>udpping_from_path</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "udpping_from_path", 1)
 ...
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 </programlisting>
 		</example>
 	</section>
 	<section id="nathelper.p.append_sdp_oldmediaip">
 		<title><varname>append_sdp_oldmediaip</varname> (int)</title>
 		<para>
 		The parameter controls if oldmediaip field should be appended to the SDP.
 		</para>
 		<para>
 		<emphasis>
 			Default value is <quote>1</quote> (feature enabled).
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>append_sdp_oldmediaip</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "append_sdp_oldmediaip", 1)
 ...
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 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.p.filter_server_id">
 		<title><varname>filter_server_id</varname> (int)</title>
 		<para>
 		Filter contacts by <quote>server_id</quote> core parameter.
 		Use this parameter to limit pinging. When set to <quote>1</quote>,
 		only proxy instances which send packets are those where core server_id
 		matches server_id saved in usrloc.
 		<emphasis>
 			Default value is <quote>0</quote> (disabled).
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>filter_server_id</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "filter_server_id", 1)
 ...
 </programlisting>
 		</example>
 	</section>
 
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 	<section id="nathelper.p.nat_addr_mode">
 		<title><varname>nat_addr_mode</varname> (int)</title>
 		<para>
 			If set to 0, only default private net addresses are checked by
 			nat_uac_test(). If set to 1, other reserved net addresses are
 			checked by nat_uac_test() as well.
 		</para>
 		<para>Default private net addresses are:</para>
 		<itemizedlist>
 			<listitem>
 				<para>10.0.0.0/8</para>
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 			</listitem>
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 			<listitem>
 				<para>172.16.0.0/12</para>
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 			</listitem>
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 			<listitem>
 				<para>192.168.0.0/16</para>
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 			</listitem>
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 			<listitem>
 				<para>100.64.0.0/10 - RFC6598 - Carrier Grade NAT</para>
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 			</listitem>
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 			<listitem>
 				<para>192.0.0.0/29 - RFC7335 - IPv4 Service Continuity Prefix</para>
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 			</listitem>
 		</itemizedlist>
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 		<para>Reserved net addresses are:</para>
 		<itemizedlist>
 			<listitem>
 				<para>192.0.0.0/24 - RFC7335 - IETF Protocol Assignments</para>
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 			</listitem>
 		</itemizedlist>
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 		<para>
 		<emphasis>
 			Default value is <quote>1</quote>.
 		</emphasis>
 		</para>
 		<example>
 		<title>Set <varname>nat_addr_mode</varname> parameter</title>
 		<programlisting format="linespecific">
 ...
 modparam("nathelper", "nat_addr_mode", 0)
 ...
 </programlisting>
 		</example>
 	</section>
 
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 	</section>
 
 
 	<section>
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 	<title>Functions</title>
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 	<section id="nathelper.f.fix_nated_contact">
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 		<title>
 		<function moreinfo="none">fix_nated_contact()</function>
 		</title>
 		<para>
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 		Rewrites the <quote>Contact</quote> header to contain the request's source 
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 		address:port.
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 		</para>
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 		<para>
 		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE.
 		</para>
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 		<example>
 		<title><function>fix_nated_contact</function> usage</title>
 		<programlisting format="linespecific">
 ...
 if (search("User-Agent: Cisco ATA.*") {fix_nated_contact();};
 ...
 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.f.fix_nated_sdp">
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 		<title>
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 		<function moreinfo="none">fix_nated_sdp(flags [, ip_address])</function>
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 		</title>
 		<para>
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 		Alters the SDP information in order to facilitate NAT traversal. What
 		changes to be performed may be controlled via the 
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 		<quote>flags</quote> parameter. Return value is -1 if error occurred,
 		1 if ip's were replaced, 2 if no ip's were replaced.
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 		</para>
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 		<para>Meaning of the parameters is as follows:</para>
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 		<itemizedlist>
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 			<listitem><para>
 			<emphasis>flags</emphasis> - the value may be a bitwise OR of 
 			the following flags:
 			</para>
 			<itemizedlist>
 				<listitem>
 					<para><emphasis>0x01</emphasis> - adds 
 					<quote>a=direction:active</quote> SDP line;
 					</para>
 				</listitem>
 				<listitem>
 					<para><emphasis>0x02</emphasis> - rewrite media
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 					&ip; address (c=) with source address of the message
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 					or the provided IP address. (a=rtcp) param will be rewritten if exists. (the provided IP address take
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 					precedence over the source address).</para>
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 				</listitem>
 				<listitem>
 					<para><emphasis>0x04</emphasis> - adds 
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 						<quote>a=nortpproxy:yes</quote> SDP line;</para>
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 				</listitem>
 				<listitem>
 					<para><emphasis>0x08</emphasis> - rewrite IP from
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 					origin description (o=) with source address of the message
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 					or the provided IP address. (a=rtcp) param will be rewritten if exists. (the provided IP address take
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 					precedence over the source address).</para>
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 				</listitem>
 			</itemizedlist>
 			</listitem>
 			<listitem><para>
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 			<emphasis>ip_address</emphasis> - IP to be used for rewriting SDP.
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 			If not specified, the received signalling IP will be used. The
 			parameter allows pseudo-variables usage. NOTE: For the IP to be
 			used, you need to use 0x02 or 0x08 flags, otherwise it will have
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 			no effect. Must be IPv4 address family.
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 			</para>
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 			</listitem>
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 		</itemizedlist>
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 		<para>
ac1ffec9
 		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, 
 		FAILURE_ROUTE, BRANCH_ROUTE.
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 		</para>
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 		<example>
 		<title><function>fix_nated_sdp</function> usage</title>
 		<programlisting format="linespecific">
 ...
 if (search("User-Agent: Cisco ATA.*") {fix_nated_sdp("3");};
 ...
 </programlisting>
 		</example>
 	</section>
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 	<section id="nathelper.f.add_rcv_param">
31ccf6a2
 		<title>
6b2b32a3
 		<function moreinfo="none">add_rcv_param([flag])</function>,
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 		</title>
 		<para>
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 		Add a received parameter to the <quote>Contact</quote> header fields
57bd759e
 		(available for all transports) or to the Contact URI (available only
 		for UDP traffic).
 		</para>
 		<para>
 		The parameter will contain the URI created from the
 		source IP, port, and protocol (if different than UDP) of the packet
 		containing the SIP message. The parameter can be then processed by
 		another registrar. This is useful, for example, when replicating register
 		messages using <function>t_replicate</function> function to another registrar.
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 		</para>
fc3be13b
 		<para>Meaning of the parameters is as follows:</para>
 		<itemizedlist>
 			<listitem><para>
 			<emphasis>flag</emphasis> - flags to indicate if the parameter
 			should be added to Contact URI or Contact header. If the flag is
 			non-zero, the parameter will be added to the Contact URI. If not
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 			used or equal to zero, the parameter will go to the Contact
fc3be13b
 			header.
 			</para></listitem>
 		</itemizedlist>
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 		<para>
 		This function can be used from REQUEST_ROUTE.
 		</para>
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 		<example>
 		<title><function>add_rcv_paramer</function> usage</title>
 		<programlisting format="linespecific">
 ...
fc3be13b
 add_rcv_param(); # add the parameter to the Contact header
 ....
0c4b0f77
 add_rcv_param("1"); # add the parameter to the Contact URI
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 ...
 </programlisting>
 		</example>
 	</section>
f4111c41
 	<section id="nathelper.f.fix_nated_register">
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 		<title>
 		<function moreinfo="none">fix_nated_register()</function>
 		</title>
 		<para>
ac1ffec9
 		The function creates a URI consisting of the source IP, port, and 
 		protocol and stores the URI in an Attribute-Value-Pair. The URI will 
 		be appended as "received" parameter to Contact in 200 OK and 
c2e74aa2
 		registrar will store it in the received column in the location table.
b8146430
 		</para>
 		<para>
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 		Note: You have to set the <quote>received_avp</quote> parameter of the
 		nathelper module and the registrar module (both module parameters must
 		have the same value) to use this function.
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 		</para>
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 		<para>
 		This function can be used from REQUEST_ROUTE.
 		</para>
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 		<example>
 		<title><function>fix_nated_register</function> usage</title>
 		<programlisting format="linespecific">
 ...
 fix_nated_register();
 ...
 </programlisting>
 		</example>
 	</section>
f4111c41
 	<section id="nathelper.f.nat_uac_test">
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 		<title>
 			<function>nat_uac_test(flags)</function>
 		</title>
 		<para>
 			Tries to guess if client's request originated behind a nat.
 			The parameter determines what heuristics is used.
 		</para>
 		<para>Meaning of the flags is as follows:</para>
 		<itemizedlist>
 			<listitem><para>
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 			<emphasis>1</emphasis> -  The <quote>Contact</quote> header field is searched 
 			for occurrence of RFC1918 or RFC6598 addresses.
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 			</para></listitem>
 			<listitem><para>
 			<emphasis>2</emphasis> -  the "received" test is used: address
f4111c41
 			in the <quote>Via</quote> header is compared against source
f327fbb8
 			IP address of signaling. If the <quote>Via</quote> header contains
 			no port, it uses the default SIP port 5060
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 			</para></listitem>
 			<listitem><para>
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 			<emphasis>4</emphasis> -  The Top Most <quote>Via</quote> is searched 
 			for occurrence of RFC1918 or RFC6598 addresses
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 			</para></listitem>
 			<listitem><para>
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 			<emphasis>8</emphasis> -  The SDP is searched for occurrence of 
 			RFC1918 or RFC6598 addresses
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 			</para></listitem>
 			<listitem><para>
f327fbb8
 			<emphasis>16</emphasis> -  Test if the source port is different from the port
 			in the <quote>Via</quote> header. If the <quote>Via</quote> header contains
 			no port, it uses the default SIP port 5060
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 			</para></listitem>
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 			<listitem><para>
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 			<emphasis>32</emphasis> -  Test if the source IP address of
 			signaling is a RFC1918 or RFC6598 address
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 			</para></listitem>
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 			<listitem><para>
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 			<emphasis>64</emphasis> -  Test if the source connection of
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 			signaling is a WebSocket
 			</para></listitem>
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 			<listitem><para>
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 			<emphasis>128</emphasis> -  Test if the <quote>Contact</quote> header
 			URI port differs from the source port of the request (Warning: this is
 			might be legal or even intended combination in non NATted scenarios)
bf3acaf0
 			</para></listitem>
26d25b1c
 			<listitem><para>
ce3bfaa8
 			<emphasis>256</emphasis> -  Test if the SDP connection address is different
 			from source IP address. It will work also with multiple connection address
 			lines.
 			</para></listitem>
fb0bb3f4
 			<listitem><para>
 			<emphasis>512</emphasis> -  Test if the target addresses are different
 			or over websocket. For requests, it compares host and port in R-URI ($rU)
 			and D-URI ($du). For replies, it compares host and port in 2nd Via
 			with received and rport parameters.
 			</para></listitem>
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 			</itemizedlist>
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 		<para>
 		All flags can be bitwise combined, the test returns true if any of 
 		the tests identified a NAT.
 		</para>
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 		<para>
 		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
 		</para>
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 		<example>
 		<title><function>nat_uac_test</function> usage</title>
 		<programlisting format="linespecific">
 ...
 if(nat_uac_test("19")) {
     rtpproxy_manage("co");
 }
 ...
 </programlisting>
 		</example>
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 	</section>
a8544418
 
f4111c41
 	<section id="nathelper.f.is_rfc1918">
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 		<title>
 		<function>is_rfc1918(ip_address)</function>
 		</title>
 		<para>
048448f0
 			Determines if the address in the parameter is an rfc1918 or rfc6598 address.
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 			The parameter allows pseudo-variables usage.
 		</para>
 		<para>
 		This function can be used from ANY_ROUTE.
 		</para>
2aa7683d
 		<example>
 		<title><function>is_rfc1918</function> usage</title>
 		<programlisting format="linespecific">
 ...
 if(is_rfc1918("$rd")) {
     # domain in r-uri is private address
 }
 ...
 </programlisting>
 		</example>
411de126
 	</section>
 
f4111c41
 	<section id="nathelper.f.add_contact_alias">
a8544418
 		<title>
c4b4ec30
 		<function moreinfo="none">add_contact_alias([ip_addr, port, proto])</function>
a8544418
 		</title>
 		<para>
c04f9554
 		Adds an <quote>;alias=ip~port~transport</quote> parameter to
 		the contact URI containing either received ip, port, and
 		transport protocol or those given as parameters.  If called
 		without parameters, <quote>;alias</quote> parameter is
93c81f53
 		only added if received ip, port, or transport protocol differs
         from that in contact URI.
a8544418
 		</para>
 		<para>
 		This function can be used from
 		REQUEST_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE, and LOCAL_ROUTE.
 		</para>
 		<example>
 		<title><function>add_contact_alias</function> usage</title>
 		<programlisting format="linespecific">
 ...
     if (!is_present_hf("Record-Route")) {
c4b4ec30
         if (!add_contact_alias("$var(src_ip)", "$Rp", "tcp")) {
a8544418
             xlog("L_ERR", "Error in aliasing contact $ct\n");
             send_reply("400", "Bad request");
             exit;
         };
     };
 ...
 		</programlisting>
 		</example>
d77df08a
 	</section>
3ea3950b
 
f4111c41
 	<section id="nathelper.f.handle_ruri_alias">
a8544418
 		<title>
9c060a66
 		<function moreinfo="none">handle_ruri_alias([mode])</function>
a8544418
 		</title>
 		<para>
f4111c41
 		Checks if the Request URI has an <quote>alias</quote>
 		parameter and if so, removes it and sets the <quote>$du</quote> based
9c060a66
 		on its value. Note that this means that routing of request is based on
 		<quote>;alias</quote> parameter value of the Request URI rather than
f4111c41
 		the Request URI itself. If you call <function>handle_ruri_alias()</function>
 		on a request, make sure that you screen the alias parameter value of
9c060a66
 		Request URI the same way as you would screen the Request URI itself.
 		</para>
 		<para>
 		The optional parameter mode can be 0 to consume first alias parameter,
 		otherwise it consumes the last alias parameter. If the parameter mode is
 		not provided, it consumes the first parameter.
7bb718bb
 		</para>
 		<para>
f4111c41
 		Returns <emphasis>1</emphasis> if <quote>;alias</quote> parameter was
 		found and <quote>$du</quote> was set and the <quote>$ru</quote> rewritten,
 		<emphasis>2</emphasis> if the alias parameter was not found and
 		nothing was done, or <emphasis>-1</emphasis> in case of error.
7e19a002
 		</para>
 		<para>
a8544418
 		This function can be used from
 		REQUEST_ROUTE, BRANCH_ROUTE, and LOCAL_ROUTE.
 		</para>
 		<example>
 		<title><function>handle_ruri_alias</function> usage</title>
 		<programlisting format="linespecific">
 ...
     if ($du == "") {
         handle_ruri_alias();
         switch ($rc) {
         case -1:
             xlog("L_ERR", "Failed to handle alias of R-URI $ru\n");
             send_reply("400", "Bad request");
             exit;
         case 1:
             xlog("L_INFO", "Routing in-dialog $rm from $fu to $du\n");
             break;
         case 2:
             xlog("L_INFO", "Routing in-dialog $rm from $fu to $ru\n");
             break;
          };
     };
 ...
 		</programlisting>
 		</example>
 	</section>
 
a41cb60d
 	<section id="nathelper.set_contact_alias">
 		<title>
3c02c11d
 		<function moreinfo="none">set_contact_alias([trim])</function>
a41cb60d
 		</title>
 		<para>
f4111c41
 		Adds an <quote>;alias=ip~port~transport</quote> parameter to the
 		contact URI containing the received ip, port, and transport protocol.
 		The new contact URI is immediately visible to other modules in the
 		way the <function>fix_nated_contact()</function> does it.
a41cb60d
 		</para>
3c02c11d
 		<para>Meaning of parameters:</para>
 		<itemizedlist>
 			<listitem>
 				<para>
 					<emphasis>trim</emphasis> - by default, set_contact_alias() will not detect and trim an
 					already existing alias parameter. If this optional parameter is set to "1", set_contact_alias()
 					will trim the existing alias before adding a new one.
 				</para>
 			</listitem>
 		</itemizedlist>
a41cb60d
 		<para>
 		This function can be used from
 		REQUEST_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE, and FAILURE_ROUTE.
 		</para>
 		<example>
 		<title><function>set_contact_alias</function> usage</title>
 		<programlisting format="linespecific">
 ...
     if (!is_present_hf("Record-Route")) {
         if (!set_contact_alias()) {
             xlog("L_ERR", "Error in aliasing contact $ct\n");
             send_reply("400", "Bad request");
             exit;
         };
     };
 ...
 		</programlisting>
 		</example>
 	</section>
28cfa397
 		<section id="nathelper.set_alias_to_pv">
46b713d3
 		<title>
28cfa397
 		<function moreinfo="none">set_alias_to_pv(target_avp)</function>
46b713d3
 		</title>
 		<para>
 		Reads <quote>;alias=ip~port~transport</quote> from Contact header then
0cc8a34d
 		writes to target pseudo-variable as a sip uri.
46b713d3
 		</para>
 		<para>
 		This function can be used from
 		REQUEST_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE, and FAILURE_ROUTE.
 		</para>
 		<example>
28cfa397
 		<title><function>set_alias_to_pv</function> usage</title>
46b713d3
 		<programlisting format="linespecific">
 ...
28cfa397
 		set_alias_to_pv("$avp(aliasuri)");
46b713d3
 ...
 		</programlisting>
 		</example>
 	</section>
a41cb60d
 
a8544418
 	</section>
 
 	<section>
 		<title>Exported Pseudo Variables</title>
 		<section>
 			<title><function moreinfo="none">$rr_count</function></title>
 			<para>
 			Number of Record Routes in received SIP request
 			or reply.
 			</para>
 		<example>
 		<title>$rr_count usage</title>
 		<programlisting format="linespecific">
 ...
     $avp(rr_count) = $rr_count;
 ...
 		</programlisting>
 		</example>
 	        </section>
 
 		<section>
 			<title><function moreinfo="none">$rr_top_count</function></title>
 			<para>
 			If topmost Record Route in received SIP request
 			or reply is a double Record Route, value of
 			$rr_top_count is 2.  If it a single Record
 			Route, value of $rr_top_count 
 			is 1.  If there is no Record Route(s), value of
 			$rr_top_count is 0.
 			</para>
 		<example>
 		<title>$rr_top_count usage</title>
 		<programlisting format="linespecific">
 ...
     if ($rr_count == $avp(rr_count) + $rr_top_count) {
         route(ADD_CONTACT_ALIAS);
     };
 ...
 		</programlisting>
 		</example>
 	        </section>
 
 	</section>
568b75ab
 
 	<section>
c3ab9ba3
 		<title>RPC Commands</title>
 		<section id="nathelper.r.enable_ping">
 			<title><function moreinfo="none">nathelper.enable_ping</function></title>
568b75ab
 			<para>
c3ab9ba3
 			Enables natping if parameter value different than 0.
568b75ab
 			Disables natping if parameter value is 0.
 			</para>
 			<para>
 			The function takes only one parameter - a number in decimal format.
 			</para>
 			<example>
c3ab9ba3
 			<title><function moreinfo="none">nathelper.enable_ping</function> usage</title>
568b75ab
 			<programlisting format="linespecific">
 ...
c3ab9ba3
 $ &kamcmd; nathelper.enable_ping 1
568b75ab
 ...
 			</programlisting>
 			</example>
 		</section>
 
d77df08a
 	</section>
568b75ab
 
b2ef844b
 	<section>
 		<title>Selects</title>
 
f4111c41
 		<section id="nathelper.s.rewrite_contact">
b2ef844b
 		<title>@nathelper.rewrite_contact[n]</title>
 		<para>
 			Get n-th Contact value with IP:Port rewritten to source ip:port. N is counted from 1.
 		    Only IP:port is rewritten, remaining part are left unchanged. Full nameaddr is supported.
 		</para>
 		<example>
 			<title>@nathelper.rewrite_contact usage</title>
 			<programlisting>
 ...
 $c = @nathelper.rewrite_contact[1];
 ...
 $c2 = @nathelper.rewrite_contact[1].nameaddr.uri;
 			</programlisting>
 		</example>
 		</section>
 
 	</section>
 
31ccf6a2
 </chapter>