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

<chapter>
	
	<title>&adminguide;</title>
	
	<section>
	<title>Overview</title>
	<para>This module implements a WebSocket (RFC 6455) server and provides
	connection establishment (handshaking), management (including
	connection keep-alive), and framing for the SIP and MSRP WebSocket
	sub-protocols (draft-ietf-sipcore-sip-websocket and
	draft-pd-msrp-websocket).</para>
	<para>The module supports WebSockets (ws) and secure WebSockets (wss)
	</para>
	</section>

	<section>
	<title>How it works</title>
	<section>
	<title>Initiating a connection</title>
	<para>A WebSocket connection is initiated with an HTTP GET.  The
	<emphasis>xhttp</emphasis> module is used to handle this GET and
	call the <xref linkend="ws_handle_handshake"/> exported function.
	</para>
	<para><emphasis>event_route[xhttp:request]</emphasis> should perform
	some validation of the HTTP headers before calling
	<xref linkend="ws_handle_handshake"/>.  The event_route can also be
	used to make sure the HTTP GET has the correct URI, perform HTTP
	authentication on the WebSocket connection, and check the
	<emphasis>Origin</emphasis> header (RFC 6454) to ensure a
	browser-based SIP UA or MSRP client has been downloaded from the
	correct location.</para>
	<example>
	<title>event_route[xhttp:request]</title>
	<programlisting><![CDATA[
...
loadmodule "sl.so"
loadmodule "xhttp.so"
loadmodule "msrp.so"  # Only required if using MSRP over WebSockets
loadmodule "websocket.so"
...
event_route[xhttp:request] {
        set_reply_close();
        set_reply_no_connect();

        if ($Rp != 80
#!ifdef WITH_TLS
            && $Rp != 443
#!endif
        ) {

                xlog("L_WARN", "HTTP request received on $Rp\n");
                xhttp_reply("403", "Forbidden", "", "");
                exit;
        }

        xlog("L_DBG", "HTTP Request Received\n");

        if ($hdr(Upgrade)=~"websocket"
                        && $hdr(Connection)=~"Upgrade"
                        && $rm=~"GET") {

                # Validate Host - make sure the client is using the correct
                # alias for WebSockets
                if ($hdr(Host) == $null || !is_myself("sip:" + $hdr(Host))) {
                        xlog("L_WARN", "Bad host $hdr(Host)\n");
                        xhttp_reply("403", "Forbidden", "", "");
                        exit;
                }

                # Optional... validate Origin - make sure the client is from an
                # authorised website.  For example,
                #
                # if ($hdr(Origin) != "http://communicator.MY_DOMAIN"
                #     && $hdr(Origin) != "https://communicator.MY_DOMAIN") {
                #       xlog("L_WARN", "Unauthorised client $hdr(Origin)\n");
                #       xhttp_reply("403", "Forbidden", "", "");
                #       exit;
                # }

                # Optional... perform HTTP authentication

                # ws_handle_handshake() exits (no further configuration file
                # processing of the request) when complete.
                if (ws_handle_handshake())
		{
			# Optional... cache some information about the
			# successful connection
			exit;
		}
        }

        xhttp_reply("404", "Not found", "", "");
}
...
]]></programlisting>
	</example>
	</section>

	<section>
	<title>SIP message routing</title>
	<para>SIP over WebSockets uses invalid URIs in routing headers
	(Contact:, Record-Route:, and Via:) because a JavaScript stack running
	in a browser has no way to determine the local address from which the
	WebSocket connection is made.  This means that the routing headers
	cannot be used for request or response routing in the normal manner.
	</para>
	<para>draft-ietf-sipcore-sip-websocket states that SIP WebSocket
	Clients and the SIP registrar should implement Outbound (RFC 5626) and
	Path (RFC 3327) to enable requests and responses to be correctly
	routed.  However, &kamailio; does not currently support Outbound and
	it may not be possible to guarantee all SIP WebSocket clients will
	support Outbound and Path.</para>
	<para>The <emphasis>nathelper</emphasis> module functions
	(<emphasis>nat_uac_test()</emphasis>, 
	<emphasis>fix_nated_register()</emphasis>,
	<emphasis>add_contact_alias()</emphasis>, and
	<emphasis>handle_ruri_alias()</emphasis>) and the Kamailio core
	<emphasis>force_rport()</emphasis> can be used to ensure correct
	routing of SIP WebSocket requests without using Outbound and Path.
	</para>
	<example>
	<title>WebSocket SIP Routing</title>
	<programlisting><![CDATA[
...
loadmodule "sl.so"
loadmodule "tm.so"
...
loadmodule "websocket.so"
...
request_route {

        # per request initial checks
        route(REQINIT);

        if (nat_uac_test(64)) {
                # Do NAT traversal stuff for requests from a WebSocket
                # connection - even if it is not behind a NAT!
                # This won't be needed in the future if Kamailio and the
                # WebSocket client support Outbound and Path.
                force_rport();
                if (is_method("REGISTER"))
                        fix_nated_register();
                else {
                        if (!add_contact_alias()) {
                                xlog("L_ERR", "Error aliasing contact <$ct>\n");
                                sl_send_reply("400", "Bad Request");
                                exit;
                        }
                }
        }

        if (!is_method("REGISTER"))
                t_on_reply("WS_REPLY");
...
# Handle requests within SIP dialogs
route[WITHINDLG] {
        if (has_totag()) {
                # sequential request withing a dialog should
                # take the path determined by record-routing
                if (loose_route()) {
                        if ($du == "") {
                                if (!handle_ruri_alias()) {
                                        xlog("L_ERR", "Bad alias <$ru>\n");
                                        sl_send_reply("400", "Bad Request");
                                        exit;
                                }
                        }
                        route(RELAY);
                } else {
                        if ( is_method("ACK") ) {
...
onreply_route[WS_REPLY] {
        if (nat_uac_test(64)) {
                # Do NAT traversal stuff for replies to a WebSocket connection
		# - even if it is not behind a NAT!
                # This won't be needed in the future if Kamailio and the
		# WebSocket client support Outbound and Path.
                add_contact_alias();
        }
}
...
]]></programlisting>
	</example>

	</section>

	<section>
	<title>MSRP message routing</title>
	<para>MSRP over WebSocket clients create invalid local URIs for use in
	Path headers (From-Path: and To-Path:) because a JavaScript stack
	running in a browser has no way to determine the local address from
	which the WebSocket connection is made.  This is OK because MSRP over
	WebSocket clients MUST use an MSRP relay and it is the MSRP relay's
	responsibility to select the correct connection to the client based on
	the MSRP URIs that it has created (and maintains a mapping for).</para>
	</section>

	</section>

	<section>
	<title>Dependencies</title>
	<section>
		<title>&kamailio; Modules</title>
		<para>
		The following module must be loaded before this module:
		<itemizedlist>
		<listitem>
		<para><emphasis>sl</emphasis>.</para>
		</listitem>
		</itemizedlist>
		</para>
		<para>
		The following modules are required to make proper use of this
		module:
		<itemizedlist>
		<listitem>
		<para><emphasis>nathelper</emphasis>.</para>
		</listitem>
		<listitem>
		<para><emphasis>tm</emphasis>.</para>
		</listitem>
		<listitem>
		<para><emphasis>xhttp</emphasis>.</para>
		</listitem>
		</itemizedlist>
		</para>
		<para>
		The following module is required to use the secure WebSocket
		(wss) scheme:
		<itemizedlist>
		<listitem>
		<para><emphasis>tls</emphasis>.</para>
		</listitem>
		</itemizedlist>
		</para>
		<para>
		The following module is required to support MSRP over
		WebSockets:
		<itemizedlist>
		<listitem>
		<para><emphasis>msrp</emphasis>.</para>
		</listitem>
		</itemizedlist>
		</para>
	</section>

	<section>
		<title>External Libraries or Applications</title>
		<para>
		The following libraries must be installed before running
		&kamailio; with this module loaded:
		<itemizedlist>
		<listitem>
		<para><emphasis>OpenSSL</emphasis>.</para>
		</listitem>
		<listitem>
		<para><emphasis>GNU libunistring</emphasis>.</para>
		</listitem>
		</itemizedlist>
		</para>
	</section>
	</section>


	<section>
	<title>Parameters</title>
	<section>
		<title><varname>keepalive_mechanism</varname> (integer)</title>
		<para>The keep-alive mechanism to use for WebSocket connections.
		</para>
		<note><para>If <emphasis>nathelper</emphasis> is only being used
		for WebSocket connections then <emphasis>nathelper NAT
		pinging</emphasis> is not required.  If
		<emphasis>nathelper</emphasis> is used for WebSocket connections
		and TCP/TLS aliasing/NAT-traversal then WebSocket keep-alives
		are not required.</para></note>
		<para>
		<itemizedlist>
		<listitem><para> 0 - no WebSocket keep-alives</para></listitem>
		<listitem><para> 1 - Ping WebSocket
		keep-alives</para></listitem>
		<listitem><para> 2 - Pong WebSocket
		keep-alives</para></listitem>
		</itemizedlist>
		</para>
		<para><emphasis>Default value is 1.</emphasis></para>
		<example>
		<title>Set <varname>keepalive_mechanism</varname>
		parameter</title>
		<programlisting format="linespecific">
...
modparam("websocket", "keepalive_mechanism", 0)
...
</programlisting>
		</example>
	</section>

	<section>
		<title><varname>keepalive_timeout</varname> (integer)</title>
		<para>The time (in seconds) after which to send a keep-alive on
		idle WebSocket connections.</para>
		<para><emphasis>Default value is 180.</emphasis></para>
		<example>
		<title>Set <varname>keepalive_timeout</varname>
		parameter</title>
		<programlisting format="linespecific">
...
modparam("websocket", "keepalive_timeout", 30)
...
</programlisting>
		</example>
	</section>

	<section>
		<title><varname>keepalive_processes</varname> (integer)</title>
		<para>The number of processes to start to perform WebSocket
		connection keep-alives.</para>
		<para><emphasis>Default value is 1.</emphasis></para>
		<example>
		<title>Set <varname>keepalive_processes</varname>
		parameter</title>
		<programlisting format="linespecific">
...
modparam("websocket", "keepalive_processes", 2)
...
</programlisting>
		</example>
	</section>

	<section>
		<title><varname>keepalive_interval</varname> (integer)</title>
		<para>The number of seconds between each keep-alice process run
		</para>
		<para><emphasis>Default value is 1.</emphasis></para>
		<example>
		<title>Set <varname>keepalive_interval</varname>
		parameter</title>
		<programlisting format="linespecific">
...
modparam("websocket", "keepalive_interval", 2)
...
</programlisting>
		</example>
	</section>

	<section>
		<title><varname>ping_application_data</varname> (string)</title>
		<para>The application data to use in keep-alive Ping and Pong
		frames.</para>
		<para><emphasis>Default value is &kamailio; Server: header
		content</emphasis></para>
		<example>
		<title>Set <varname>ping_application_data</varname>
		parameter</title>
		<programlisting format="linespecific">
...
modparam("websocket", "ping_application_data", "WebSockets rock")
...
</programlisting>
		</example>
	</section>

	<section>
		<title><varname>sub_protocols</varname> (integer)</title>
		<para>A bitmap that allows you to control the sub-protocols
		supported by the WebSocket server.</para>
		<itemizedlist>
		<listitem><para>
		<emphasis>1</emphasis> - sip (draft-ietf-sipcore-sip-websocket)
		</para></listitem>
		<listitem><para>
		<emphasis>2</emphasis> - msrp (draft-pd-msrp-websocket) -
		msrp.so must be loaded before websocket.so
		</para></listitem>
		</itemizedlist>
		<para><emphasis>Default value is 1 when msrp.so is not loaded
		 3 when msrp.so is loaded.</emphasis></para>
		<example>
		<title>Set <varname>sub_protocols</varname>
		parameter</title>
		<programlisting format="linespecific">
...
modparam("websocket", "sub_protocols", 2)
...
</programlisting>
		</example>
	</section>

	</section>

	<section>
	<title>Functions</title>
	<section id="ws_handle_handshake">
		<title>
		<function moreinfo="none">ws_handle_handshake()</function>
		</title>
		<para>This function checks an HTTP GET request for the required
		headers and values, and (if successful) upgrades the connection
		from HTTP to WebSocket.</para>
		<para>This function can be used from ANY_ROUTE (but will only
		work in <emphasis>event_route[xhttp:request]</emphasis>).</para>
		<note><para>This function returns 0, stopping all further
		processing of the request, when there is a problem.</para></note>
		<example>
		<title><function>ws_handle_handshake</function> usage</title>
		<programlisting format="linespecific">
...
ws_handle_handshake();
...
</programlisting>
		</example>
	</section>
	</section>

	<section>
	<title>MI Commands</title>
	<section>
		<title><function moreinfo="none">ws.dump</function></title>
		<para>Provides the details of the first 50 WebSocket
		connections.</para>
		<para>Name: <emphasis>ws.dump</emphasis></para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem>
				<para>order (optional) -
				<quote>id_hash</quote>,
				<quote>used_desc</quote>, or
				<quote>used_asc</quote>.</para>
			</listitem>
		</itemizedlist>
		<note><para>If no parameter is provided id_hash order is
		used.</para></note>
		<para>MI FIFO Command Format:</para>
		<programlisting  format="linespecific">
			:ws.dump:fifo_reply
			used_asc
			_empty_line_
</programlisting>
	</section>

	<section>
		<title><function moreinfo="none">ws.close</function></title>
		<para>Starts the close handshake for the specified
		WebSocket connection.</para>
		<para>Name: <emphasis>ws.close</emphasis></para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem>
				<para>id - WebSocket connection ID.</para>
			</listitem>
		</itemizedlist>
		<para>MI FIFO Command Format:</para>
		<programlisting  format="linespecific">
			:ws.close:fifo_reply
			1
			_empty_line_
</programlisting>
	</section>

	<section>
		<title><function moreinfo="none">ws.ping</function></title>
		<para>Sends a Ping frame on the specified WebSocket
		connection.</para>
		<para>Name: <emphasis>ws.ping</emphasis></para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem>
				<para>id - WebSocket connection ID.</para>
			</listitem>
		</itemizedlist>
		<para>MI FIFO Command Format:</para>
		<programlisting  format="linespecific">
			:ws.ping:fifo_reply
			1
			_empty_line_
</programlisting>
	</section>

	<section>
		<title><function moreinfo="none">ws.pong</function></title>
		<para>Sends a Pong frame on the specified WebSocket
		connection.</para>
		<para>Name: <emphasis>ws.pong</emphasis></para>
		<para>Parameters:</para>
		<itemizedlist>
			<listitem>
				<para>id - WebSocket connection ID.</para>
			</listitem>
		</itemizedlist>
		<para>MI FIFO Command Format:</para>
		<programlisting  format="linespecific">
			:ws.pong:fifo_reply
			1
			_empty_line_
</programlisting>
	</section>

	<section>
		<title><function moreinfo="none">ws.disable</function></title>
		<para>Disables WebSockets preventing new connections from
		being established.</para>
		<para>Name: <emphasis>ws.disable</emphasis></para>
		<para>Parameters: <emphasis>none</emphasis></para>
		<para>MI FIFO Command Format:</para>
		<programlisting  format="linespecific">
			:ws.disable:fifo_reply
			_empty_line_
</programlisting>
	</section>

	<section>
		<title><function moreinfo="none">ws.enable</function></title>
		<para>Enables WebSockets allowing new connections to be
		established.</para>
		<note><para>WebSockets are enabled at start-up.</para></note>
		<para>Name: <emphasis>ws.enable</emphasis></para>
		<para>Parameters: <emphasis>none</emphasis></para>
		<para>MI FIFO Command Format:</para>
		<programlisting  format="linespecific">
			:ws.enable:fifo_reply
			_empty_line_
</programlisting>
	</section>

	</section>

	<section>
	<title>Event routes</title>
	<section>
		<title>
		<function moreinfo="none">websocket:closed</function>
		</title>
		<para>
			When defined, the module calls
			event_route[websocket:closed] when a connection
			closes.  The connection may be identified using the
			the $si and $sp pseudo-variables.
		</para>
		<programlisting format="linespecific">
...
event_route[websocket:closed] {
	xlog("L_INFO", "WebSocket connection from $si:$sp has closed\n");
}
...
		</programlisting>
	</section>

	</section>	
</chapter>

