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

<chapter>
    <chapterinfo>
	<revhistory>
	    <revision>
		<revnumber>$Revision: 1.1 $</revnumber>
		<date>$Date: 2003/07/14 21:03:05 $</date>
	    </revision>
	</revhistory>
    </chapterinfo>
    <title>User's Guide</title>
    
    <section>
	<title>Overview</title>
	<para>
	    Domain module implements checks that based on domain table determine if a host part of
	    an <acronym>URI</acronym> is <quote>local</quote> or not.  A <quote>local</quote> domain
	    is one that the proxy is responsible for.
	</para>
	<para>
	    Domain module operates in caching or non-caching mode depending on value of module
	    parameter <parameter moreinfo="none">db_mode</parameter>. In caching mode domain module
	    reads the contents of domain table into cache memory when the module is loaded.  After
	    that domain table is re-read only when module is given domain_reload fifo command.  Any
	    changes in domain table must thus be followed by domain_reload command in order to
	    reflect them in module behavior. In non-caching mode domain module always queries domain
	    table in the database.
	</para>
	<para>
	    Caching is implemented using a hash table. The size of the hash table is given by
	    HASH_SIZE constant defined in domain_mod.h. Its <quote>factory default</quote> value is
	    128.
	</para>
    </section>
    <section>
	<title>Dependencies</title>
	<para>
	    The module depends on the following modules (in the other words the listed modules
	    must be loaded before this module):
	    <itemizedlist>
		<listitem>
		    <para><emphasis>database</emphasis> -- Any database module</para>
		</listitem>
	    </itemizedlist>
	</para>
    </section>
    <section>
	<title>Exported Parameters</title>
	<section>
	    <title><varname>db_url</varname> (string)</title>
	    <para>
		This is <acronym>URL</acronym> of the database to be used.
	    </para>
	    <para>
		Default value is <quote>sql://serro:47serro11@localhost/ser</quote>
	    </para>
	    <example>
		<title>Setting db_url parameter</title>
		<programlisting format="linespecific">
modparam("domain", "db_url", "sql://ser:pass@db_host/ser")
</programlisting>
	    </example>
	</section>
	<section>
	    <title><varname>db_mode</varname> (integer)</title>
	    <para>
		Database mode. 0 means non-caching, 1 means caching.
	    </para>
	    <para>
		Default value is 0 (non-caching).
	    </para>
	    <example>
		<title>nonce_expire example</title>
		<programlisting format="linespecific">
modparam("domain", "db_mode", 1)   # Use chaching
</programlisting>
	    </example>
	</section>
	<section>
	    <title><varname>domain_table</varname> (string)</title>
	    <para>
		Name of table containing names of local domains that the proxy is responsible for.
		Local users must have in their sip uri a host part that is equal to one of these
		domains.
	    </para>
	    <para>
		Default value is <quote>domain</quote>.
	    </para>
	    <example>
		<title>Setting domain_table parameter</title>
		<programlisting format="linespecific">
modparam("domain", "domain_table", "new_name")
</programlisting>
	    </example>
	</section>
	<section>
	    <title><varname>domain_column</varname> (string)</title>
	    <para>
		Name of column containing domains in domain table.
	    </para>
	    <para>
		Default value is <quote>domain</quote>.
	    </para>
	    <example>
		<title>Setting domain_column parameter</title>
		<programlisting format="linespecific">
modparam("domain", "domain_column", "domain_col")
</programlisting>
	    </example>
	</section>
	
    </section>
    <section>
	<title>Exported Functions</title>
	<section>
	    <title><function moreinfo="none">is_from_local()</function></title>
	    <para>
		Checks based on domain table if host part of From header uri is
		one of the local domains that the proxy is responsible for
	    </para>
	    <example>
		<title>is_from_local usage</title>
		<programlisting format="linespecific">
...
if (is_from_local()) {
    ...
};
...
</programlisting>
	    </example>
	</section>
    </section>
    <section>
	<title><acronym>FIFO</acronym> Commands</title>
	<section>
	    <title><function moreinfo="none">domain_reload</function></title>
	    <para>
		Causes domain module to re-read the contents of domain table
		into cache memory.
	    </para>
	</section>
	<section>
	    <title><function moreinfo="none">domain_dump</function></title>
	    <para>
		Causes domain module to dump hash indexes and domain names in
		its cache memory.
	    </para>
	</section>
    </section>
    <section>
	<title>Known Limitations</title>
	<para>
	    There is an unlikely race condition on domain list update.  If a process uses a table,
	    which is reloaded at the same time twice through <acronym>FIFO</acronym>, the second
	    reload will delete the original table still in use by the process.
	</para>
    </section>
</chapter>

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