maxfwd_user.sgml

sip server服务器

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

<chapter>
    <chapterinfo>
	<revhistory>
	    <revision>
		<revnumber>$Revision: 1.1 $</revnumber>
		<date>$Date: 2003/07/16 14:47:35 $</date>
	    </revision>
	</revhistory>
    </chapterinfo>
    <title>User's Guide</title>
    
    <section>
	<title>Overview</title>
	<para>
	    The module implements all the operations regarding MaX-Forward header field, like adding
	    it (if not present) or decrementing and checking the value of the existent one.
	</para>
    </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 Functions</title>
	<section>
	    <title>
		<function moreinfo="none">mf_process_maxfwd_header(max_value)</function>
	    </title>
	    <para>
		If no Max-Forward header is present in the received request, a header will be added
		having the original value equal with <quote>max_value</quote>. An OK code is
		returned by the function.
	    </para>
	    <para>
		If a Max-Forward header is already present, its value will be decremented. If after
		this operation its value will be positive non-zero, an OK code will be
		returned. Otherwise (for a zero value) an error code will be returned.  Note that an
		error code will be also returned if the &sip; message couldn't be parsed or if the
		Max-Forward header's body invalid (non numerical string or negative numerical value).
	    </para>
	    <para>Meaning of the parameters is as follows:</para>
	    <itemizedlist>
		<listitem>
		    <para><emphasis>max_value</emphasis> - Value to be added if there is no
		    Max-Forwards header field in the message.
		    </para>
		</listitem>
	    </itemizedlist>
	    <example>
		<title><function>mx_process_maxfwd_header</function> usage</title>
		<programlisting format="linespecific">
...
# initial sanity checks -- messages with
# max_forwards==0, or excessively long requests
if (!mf_process_maxfwd_header("10")) {
    sl_send_reply("483","Too Many Hops");
    break;
};
...
</programlisting>
	    </example>
	</section>
    </section>
</chapter>

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