nathelper_user.sgml

性能优秀的SIP Proxy

...
</programlisting>
		</example>
	</section>
	</section>


	<section>
	<title>Exported Functions</title>
	<section>
		<title>
		<function moreinfo="none">fix_nated_contact()</function>
		</title>
		<para>
		Rewrites Contact <acronym>HF</acronym> to contain request's source 
		address:port.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE.
		</para>
		<example>
		<title><function>fix_nated_contact</function> usage</title>
		<programlisting format="linespecific">
...
if (search("User-Agent: Cisco ATA.*") {fix_nated_contact();};
...
</programlisting>
		</example>
	</section>
	<section>
		<title>
		<function moreinfo="none">fix_nated_sdp(flags)</function>
		<function moreinfo="none">fix_nated_sdp(flags,IP)</function>
		</title>
		<para>
		Alters the SDP information in orer to facilitate NAT traversal. What
		changes to be performed may be controled via the 
		<quote>flags</quote> paramter.
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
			<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
					&ip; address (c=) with source address of the message
					or the provided IP address (the provide IP address take
					precedence over the source address).
				</listitem>
				<listitem>
					<para><emphasis>0x04</emphasis> - adds 
					<quote>a=nortpproxy:yes</quote> SDP line;
				</listitem>
				<listitem>
					<para><emphasis>0x08</emphasis> - rewrite IP from
					origin description (o=) with source address of the message
					or the provided IP address (the provide IP address take
					precedence over the source address).
				</listitem>
			</itemizedlist>
			</listitem>
			<listitem><para>
			<emphasis>IP</emphasis> - IP to be used for rewritting SDP. 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 no effect.
			</para>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, 
		FAILURE_ROUTE, BRANCH_ROUTE.
		</para>
		<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>
	<section>
		<title>
		<function moreinfo="none">force_rtp_proxy()</function>
		</title>
		<para>
		Rewrites &sdp; body to ensure that media is passed through 
		an &rtp; proxy.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, 
		FAILURE_ROUTE, BRANCH_ROUTE.
		</para>
		<example>
		<title><function>force_rtp_proxy</function> usage</title>
		<programlisting format="linespecific">
...
if (search("User-Agent: Cisco ATA.*") {force_rtp_proxy();};
...
</programlisting>
		</example>
	</section>
	<section>
		<title>
		<function moreinfo="none">force_rtp_proxy(flags)</function>
		</title>
		<para>
		Same as force_rtp_proxy, but forces additional flags.
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
		<listitem>
			<para>
			<emphasis>flags</emphasis> - flags to turn on some features.
			</para>
			<itemizedlist>
				<listitem><para>
				<emphasis>a</emphasis> - flags that UA from which message is
				received doesn't support symmetric RTP.
				</para></listitem>
				<listitem><para>
				<emphasis>l</emphasis> - force <quote>lookup</quote>, that is,
				only rewrite SDP when corresponding session is already exists 
				in the RTP proxy. Only makes sense for SIP requests, replies 
				are always processed in <quote>lookup</quote> mode.
				</para></listitem>
				<listitem><para>
				<emphasis>i</emphasis> - flags that message is received from 
				UA in the LAN (internal network). Only makes sense when 
				RTP proxy is running in the bridge mode.
				</para></listitem>
				<listitem><para>
				<emphasis>e</emphasis> - flags that message is received from 
				UA in the WAN (external network). Only makes sense when RTP 
				proxy is running in the bridge mode.
				</para></listitem>
				<listitem><para>
				<emphasis>f</emphasis> - instructs nathelper to ignore marks 
				inserted by another nathelper in transit to indicate that the 
				session is already goes through another proxy. Allows creating 
				chain of proxies.
				</para></listitem>
				<listitem><para>
				<emphasis>r</emphasis> - flags that IP address in SDP should 
				be trusted. Without this flag, nathelper ignores address in 
				the SDP and uses source address of the SIP message as media 
				address which is passed to the RTP proxy.
				</para></listitem>
				<listitem><para>
				<emphasis>o</emphasis> - flags that IP from the origin 
				description (o=) should be also changed.
				</para></listitem>
				<listitem><para>
				<emphasis>c</emphasis> - flags to change the session-level 
				SDP connection (c=) IP if media-description also includes 
				connection information.
				</para></listitem>
				<listitem><para>
				<emphasis>s</emphasis> - flags to swap creation with 
				confirmation between requests and replies. By default, a 
				request creates the RTP session and a reply confirms it. If
				swapped, a reply will create the RTP session and a request
				will confirm it.
				</para></listitem>
			</itemizedlist>
		</listitem>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, 
		FAILURE_ROUTE, BRANCH_ROUTE.
		</para>
		<example>
		<title><function>force_rtp_proxy</function> usage</title>
		<programlisting format="linespecific">
...
if (src_ip=1.2.3.4) {force_rtp_proxy("i");};
...
</programlisting>
		</example>
	</section>
	<section>
		<title>
		<function moreinfo="none">force_rtp_proxy(flags, ip_address)</function>
		</title>
		<para>
		Same as force_rtp_proxy(flags), but it may force a new SDP IP address.
		</para>
		<para>Meaning of the parameters is as follows:</para>
		<itemizedlist>
			<listitem><para>
			<emphasis>flags</emphasis> - flags to turn on some features.
			</para></listitem>
			<listitem><para>
			<emphasis>ip_address</emphasis> - new SDP IP address.
			</para></listitem>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
		</para>
		<example>
		<title><function>force_rtp_proxy</function> usage</title>
		<programlisting format="linespecific">
...
if (search("User-Agent: Cisco ATA.*") {force_rtp_proxy("","1.2.3.4");};
...
</programlisting>
		</example>
	</section>
	<section>
		<title>
		<function moreinfo="none">unforce_rtp_proxy()</function>
		</title>
		<para>
		Tears down the RTPProxy session for the current call.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
		</para>
		<example>
		<title><function>unforce_rtp_proxy</function> usage</title>
		<programlisting format="linespecific">
...
unforce_rtp_proxy();
...
</programlisting>
		</example>
	</section>
	<section>
		<title>
		<function moreinfo="none">add_rcv_param()</function>,
		<function moreinfo="none">add_rcv_param(flag)</function>
		</title>
		<para>
		Add received parameter to Contact header fields or Contact URI.
		The parameter will 
		contain URI created from the source IP, port, and protocol 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 t_replicate function to
		another registrar.
		</para>
		<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
			used or equal to zero, the parameter will go to the Contact 
			header.
			</para></listitem>
		</itemizedlist>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>add_rcv_paramer</function> usage</title>
		<programlisting format="linespecific">
...
add_rcv_param(); # add the parameter to the Contact header
....
add_rcv_param("1"); # add the paramter to the Contact URI
...
</programlisting>
		</example>
	</section>
	<section>
		<title>
		<function moreinfo="none">fix_nated_register()</function>
		</title>
		<para>
		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 
		registrar will store it in the user location database.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>fix_nated_register</function> usage</title>
		<programlisting format="linespecific">
...
fix_nated_register();
...
</programlisting>
		</example>
	</section>
	<section>
		<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>
			<emphasis>1</emphasis> -  Contact header field is searched 
			for occurrence of RFC1918 addresses.
			</para></listitem>
			<listitem><para>
			<emphasis>2</emphasis> -  the "received" test is used: address
			in Via is compared against source IP address of signaling
			</para></listitem>
			<listitem><para>
			<emphasis>4</emphasis> -  Top Most VIA is searched 
			for occurrence of RFC1918 addresses
			</para></listitem>
			<listitem><para>
			<emphasis>8</emphasis> -  SDP is searched for occurrence of 
			RFC1918 addresses
			</para></listitem>
			<listitem><para>
			<emphasis>16</emphasis> -  test if the source port is different
			from the port in Via 
			</para></listitem>
		</itemizedlist>
		<para>
		All flags can be bitwise combined, the test returns true if any of 
		the tests identified a NAT.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE.
		</para>
	</section>
</chapter>

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