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

<chapter>

	<title>&adminguide;</title>

	<section>
	<title>Overview</title>
	<para>
		This module hides the SIP routing headers that show topology details.
		It is not affected by the server being transaction stateless or
		stateful. The script interpreter gets the SIP messages decoded,
		so all existing functionality is preserved.
	</para>
	<para>
		The module is transparent for the configuration writer. It only needs to be
		loaded (tune the parameters if needed). The SIP server can be restarted
		without affecting ongoing calls - once it is up, can encode/decode
		topology details, thus no call will be lost.
	</para>
	<para>
		By using same mask_key, many SIP servers can decode the message,
		for example, applicable for servers behind load balancers.
	</para>
	</section>
	<section>
	<title>Dependencies</title>
	<section>
		<title>&kamailio; Modules</title>
		<para>
		The following modules must be loaded before this module:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>rr module</emphasis> - server must perform record
				routing to ensure in-dialog requests are encoded/decoded.
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>
	<section>
		<title>External Libraries or Applications</title>
		<para>
		The following libraries or applications must be installed before running
		&kamailio; with this module loaded:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>None</emphasis>. In the future the module can be
				enhanced to use a stronger encryption algorithm.
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>
	</section>
	<section>
	<title>Parameters</title>
	<section id="topoh.p.mask_key">
		<title><varname>mask_key</varname> (str)</title>
		<para>
		Keyword to mask the headers.
		</para>
		<para>
		<emphasis>
			Default value is "_static_value_".
		</emphasis>
		</para>
		<example>
		<title>Set <varname>mask_key</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "mask_key", "some secret here")
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.mask_ip">
		<title><varname>mask_ip</varname> (str)</title>
		<para>
		IP address to be used in masked headers to build valid
		SIP URIs. Can be any IP address, even a private-space or non-existing
		IP address (e.g., 192.168.1.1, 127.0.0.2), including the SIP server
		address, but must not be an address potentially used by clients.
		It is not used at all for SIP routing.
		</para>
		<para>
		<emphasis>
			Default value is "127.0.0.8".
		</emphasis>
		</para>
		<example>
		<title>Set <varname>mask_ip</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "mask_ip", "192.168.0.1")
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.mask_callid">
		<title><varname>mask_callid</varname> (integer)</title>
		<para>
			Whether to encode the Call-id: header. Some SIP extensions include
			the Call-id in the SIP message payload or header, so it is safe to
			not encode Call-id in such cases. Well-known extensions such as
			call transfer or conference join will be added to work with encoded
			Call-id.
		</para>
		<para>
			NOTE: if you are using dialog module to terminate calls and this
			parameter is enabled, you must set the dialog module parameter
			'lreq_callee_headers' to include the header: 'TH: dlh\r\n'.
		</para>
		<para>
		<emphasis>
			Default value is 0 (do not mask).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>mask_callid</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "mask_callid", 1)
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.uparam_name">
		<title><varname>uparam_name</varname> (str)</title>
		<para>
		Name of URI parameter where to store encoded value.
		</para>
		<para>
		<emphasis>
			Default value is "line".
		</emphasis>
		</para>
		<example>
		<title>Set <varname>uparam_name</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "uparam_name", "myparam")
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.uparam_prefix">
		<title><varname>uparam_prefix</varname> (str)</title>
		<para>
		Prefix to be added in encoded URI parameters.
		</para>
		<para>
		<emphasis>
			Default value is "sr-".
		</emphasis>
		</para>
		<example>
		<title>Set <varname>uparam_prefix</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "uparam_prefix", "xyz")
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.vparam_name">
		<title><varname>vparam_name</varname> (str)</title>
		<para>
		Name of Via: parameter used to store encoded value.
		</para>
		<para>
		<emphasis>
			Default value is "branch".
		</emphasis>
		</para>
		<example>
		<title>Set <varname>vparam_name</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "vparam_name", "myv")
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.vparam_prefix">
		<title><varname>vparam_prefix</varname> (str)</title>
		<para>
		Prefix to be added in encoded Via: parameters.
		</para>
		<para>
		<emphasis>
			Default value is "z9hG4bKsr-".
		</emphasis>
		</para>
		<example>
		<title>Set <varname>vparam_prefix</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "vparam_prefix", "xyz")
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.callid_prefix">
		<title><varname>callid_prefix</varname> (str)</title>
		<para>
		Prefix to be added in encoded Call-ID: headers.
		</para>
		<para>
		<emphasis>
			Default value is "!!:".
		</emphasis>
		</para>
		<example>
		<title>Set <varname>callid_prefix</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "callid_prefix", "***")
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.sanity_checks">
		<title><varname>sanity_checks</varname> (integer)</title>
		<para>
			If set to 1, topoh module will bind to sanity module in order
			to perform sanity checks over received SIP request. Default
			sanity checks are done. It is useful to check if received request
			is well formatted before proceeding to encoding/decoding.
		</para>
		<para>
		<emphasis>
			Default value is 0 (do not bind to sanity module).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>sanity_checks</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "sanity_checks", 1)
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.uri_prefix_checks">
		<title><varname>uri_prefix_checks</varname> (integer)</title>
		<para>
			If set to 1, topoh module will check if URIs to be decoded match
			the expected prefix composed from mask IP and parameter name prefix.
			It can make the topoh processing safer by avoiding to try decoding
			URIs which were not encoded previously by topoh.
		</para>
		<para>
			Note: do not enable this option if you have SIP devices that can
			alter the URI values it takes from Contact or Record-Route headers
			(like adding port 5060 when no port is in received URIs, or
			that introduces new parameters at an unknown position).
		</para>
		<para>
		<emphasis>
			Default value is 0.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>uri_prefix_checks</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "uri_prefix_checks", 1)
...
</programlisting>
		</example>
	</section>
	<section id="topoh.p.event_callback">
		<title><varname>event_callback</varname> (str)</title>
		<para>
			The name of the function in the KEMI configuration file (embedded
			scripting language such as Lua, Python, ...) to be executed instead
			of event_route[...] blocks.
		</para>
		<para>
			The function receives a string parameter with the name of the event.
		</para>
		<para>
		<emphasis>
			Default value is 'empty' (no function is executed for events).
		</emphasis>
		</para>
		<example>
		<title>Set <varname>event_callback</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("topoh", "event_callback", "ksr_topoh_event")
...
-- event callback function implemented in Lua
function ksr_topoh_event(evname)
	KSR.info("===== topoh module triggered event: " .. evname .. "\n");
	return 1;
end
...
</programlisting>
		</example>
	</section>
	</section>

	<section>
	<title>Event Routes</title>
	<section>
		<title>event_route[topoh:msg-outgoing]</title>
		<para>
		It is executed before doing topology hiding processing for an outgoing
		SIP message. If 'drop' is executed inside the event route, then the
		module skips doing the topology hiding.
		</para>
		<para>
		Inside the event route the variables $sndto(ip), $sndto(port) and
		$sndto(proto) point to the destination. The SIP message is not the one
		to be sent out, but an internally generated one at startup, to avoid
		reparsing the outgoing SIP message for the cases when topology hiding
		is not wanted.
		</para>
		<example>
		<title>Usage of event_route[topoh:msg-outgoing]</title>
		<programlisting format="linespecific">
...
event_route[topoh:msg-outgoing] {
  if($sndto(ip)=="10.1.1.10") {
    drop;
  }
}
...
</programlisting>
		</example>
	</section>
	</section>
</chapter>

