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WebSocket Module
Peter Dunkley
Crocodile RCS Ltd
Copyright © 2012-2013 Crocodile RCS Ltd
__________________________________________________________________
Table of Contents
1. Admin Guide
1. Overview
2. How it works
2.1. Initiating a connection
2.2. SIP message routing
2.3. MSRP message routing
3. Dependencies
3.1. Kamailio Modules
3.2. External Libraries or Applications
4. Parameters
4.1. keepalive_mechanism (integer)
4.2. keepalive_timeout (integer)
4.3. keepalive_processes (integer)
4.4. keepalive_interval (integer)
4.5. ping_application_data (string)
4.6. sub_protocols (integer)
4.7. cors_mode (integer)
4.8. verbose_list (int)
4.9. event_callback (str)
4.10. timer_interval (integer)
4.11. rm_delay_interval (integer)
5. Functions
5.1. ws_handle_handshake()
5.2. ws_close([status, reason[, connection_id]])
6. RPC Commands
6.1. ws.dump
6.2. ws.close
6.3. ws.ping
6.4. ws.pong
6.5. ws.disable
6.6. ws.enable
7. Event routes
7.1. websocket:closed
8. Exported Pseudo Variables
8.1. $ws_conid
List of Examples
1.1. event_route[xhttp:request]
1.2. WebSocket SIP Routing
1.3. Set keepalive_mechanism parameter
1.4. Set keepalive_timeout parameter
1.5. Set keepalive_processes parameter
1.6. Set keepalive_interval parameter
1.7. Set ping_application_data parameter
1.8. Set sub_protocols parameter
1.9. Set cors_mode parameter
1.10. Set verbose_list parameter
1.11. Set event_callback parameter
1.12. Set timer_intervalparameter
1.13. Set rm_delay_intervalparameter
1.14. ws_handle_handshake usage
1.15. ws_close usage
1.16. event_route[websocket:closed] usage
1.17. $ws_conid usage
Chapter 1. Admin Guide
Table of Contents
1. Overview
2. How it works
2.1. Initiating a connection
2.2. SIP message routing
2.3. MSRP message routing
3. Dependencies
3.1. Kamailio Modules
3.2. External Libraries or Applications
4. Parameters
4.1. keepalive_mechanism (integer)
4.2. keepalive_timeout (integer)
4.3. keepalive_processes (integer)
4.4. keepalive_interval (integer)
4.5. ping_application_data (string)
4.6. sub_protocols (integer)
4.7. cors_mode (integer)
4.8. verbose_list (int)
4.9. event_callback (str)
4.10. timer_interval (integer)
4.11. rm_delay_interval (integer)
5. Functions
5.1. ws_handle_handshake()
5.2. ws_close([status, reason[, connection_id]])
6. RPC Commands
6.1. ws.dump
6.2. ws.close
6.3. ws.ping
6.4. ws.pong
6.5. ws.disable
6.6. ws.enable
7. Event routes
7.1. websocket:closed
8. Exported Pseudo Variables
8.1. $ws_conid
1. Overview
This module implements a WebSocket (RFC 6455) server and provides
connection establishment (handshaking), management (including
connection keep-alive), and framing for the SIP and MSRP WebSocket
sub-protocols (RFC 7118 and RFC 7977).
The module supports WebSockets (ws) and secure WebSockets (wss)
transports
2. How it works
2.1. Initiating a connection
2.2. SIP message routing
2.3. MSRP message routing
2.1. Initiating a connection
A WebSocket connection is initiated with an HTTP GET. The xhttp module
is used to handle this GET and call the Section 5.1, “
ws_handle_handshake() ” exported function.
event_route[xhttp:request] should perform some validation of the HTTP
headers before calling Section 5.1, “ ws_handle_handshake() ”. The
event_route can also be used to make sure the HTTP GET has the correct
URI, perform HTTP authentication on the WebSocket connection, and check
the Origin header (RFC 6454) to ensure a browser-based SIP UA or MSRP
client has been downloaded from the correct location.
Example 1.1. event_route[xhttp:request]
...
loadmodule "sl.so"
loadmodule "xhttp.so"
loadmodule "msrp.so" # Only required if using MSRP over WebSockets
loadmodule "websocket.so"
...
event_route[xhttp:request] {
set_reply_close();
set_reply_no_connect();
if ($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 $hdr(Origin)\n");
# xhttp_reply("403", "Forbidden", "", "");
# exit;
# }
# Optional... perform HTTP authentication
# ws_handle_handshake() exits (no further configuration file
# processing of the request) when complete in case of failure.
if (ws_handle_handshake())
{
# Optional... cache some information about the
# successful connection
exit;
}
}
xhttp_reply("404", "Not found", "", "");
}
...
2.2. SIP message routing
SIP over WebSockets uses invalid URIs in routing headers (Contact:,
Record-Route:, and Via:) because a JavaScript stack running in a
browser has no way to determine the local address from which the
WebSocket connection is made. This means that the routing headers
cannot be used for request or response routing in the normal manner.
RFC 7118 - The WebSocket Protocol as a Transport for the Session
Initiation Protocol - states that SIP WebSocket Clients and the SIP
registrar should implement SIP Outbound (RFC 5626) and Path header
support (RFC 3327) to enable requests and responses to be correctly
routed. Kamailio has a module called "Outbound" for this functionality.
The nathelper module functions (nat_uac_test(), fix_nated_register(),
add_contact_alias(), and handle_ruri_alias()) and the Kamailio core
force_rport() can be used to ensure correct routing of SIP WebSocket
requests without using Outbound and Path.
Example 1.2. WebSocket SIP Routing
...
loadmodule "sl.so"
loadmodule "tm.so"
...
loadmodule "websocket.so"
...
request_route {
# per request initial checks
route(REQINIT);
if (nat_uac_test(64)) {
# Do NAT traversal stuff for requests from a WebSocket
# connection - even if it is not behind a NAT!
# This won't be needed in the future if Kamailio and the
# WebSocket client support Outbound and Path.
force_rport();
if (is_method("REGISTER"))
fix_nated_register();
else {
if (!add_contact_alias()) {
xlog("L_ERR", "Error aliasing contact <$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();
}
}
...
2.3. MSRP message routing
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).
3. Dependencies
3.1. Kamailio Modules
3.2. External Libraries or Applications
3.1. Kamailio Modules
The following module must be loaded before this module:
* sl.
* tm.
The following modules are required to make proper use of this module:
* nathelper or outbound.
* xhttp.
The following module is required to use the secure WebSocket (wss)
scheme:
* tls.
The following module is required to support MSRP over WebSockets:
* msrp.
3.2. External Libraries or Applications
The following libraries must be installed before running Kamailio with
this module loaded:
* OpenSSL.
* GNU libunistring.
4. Parameters
4.1. keepalive_mechanism (integer)
4.2. keepalive_timeout (integer)
4.3. keepalive_processes (integer)
4.4. keepalive_interval (integer)
4.5. ping_application_data (string)
4.6. sub_protocols (integer)
4.7. cors_mode (integer)
4.8. verbose_list (int)
4.9. event_callback (str)
4.10. timer_interval (integer)
4.11. rm_delay_interval (integer)
4.1. keepalive_mechanism (integer)
The keep-alive mechanism to use for WebSocket connections.
Note
If nathelper is only being used for WebSocket connections then
nathelper NAT pinging is not required. If nathelper is used for
WebSocket connections and TCP/TLS aliasing/NAT-traversal then WebSocket
keep-alives are not required.
* 0 - no WebSocket keep-alives
* 1 - Ping WebSocket keep-alives
* 2 - Pong WebSocket keep-alives
Default value is 1.
Example 1.3. Set keepalive_mechanism parameter
...
modparam("websocket", "keepalive_mechanism", 0)
...
4.2. keepalive_timeout (integer)
The time (in seconds) after which to send a keep-alive on idle
WebSocket connections.
Default value is 180.
Example 1.4. Set keepalive_timeout parameter
...
modparam("websocket", "keepalive_timeout", 30)
...
4.3. keepalive_processes (integer)
The number of processes to start to perform WebSocket connection
keep-alives.
Default value is 1.
Example 1.5. Set keepalive_processes parameter
...
modparam("websocket", "keepalive_processes", 2)
...
4.4. keepalive_interval (integer)
The number of seconds between each keep-alive process run
Default value is 1.
Example 1.6. Set keepalive_interval parameter
...
modparam("websocket", "keepalive_interval", 2)
...
4.5. ping_application_data (string)
The application data to use in keep-alive Ping and Pong frames.
Default value is Kamailio Server: header content
Example 1.7. Set ping_application_data parameter
...
modparam("websocket", "ping_application_data", "WebSockets rock")
...
4.6. sub_protocols (integer)
A bitmap that allows you to control the sub-protocols supported by the
WebSocket server.
* 1 - sip (RFC 7118)
* 2 - msrp (RFC 7977) - the msrp module must be loaded before the
websocket module
Default value is 1 when msrp module is not loaded, 3 when msrp module
is loaded.
Example 1.8. Set sub_protocols parameter
...
modparam("websocket", "sub_protocols", 2)
...
4.7. cors_mode (integer)
This parameter lets you set the "Cross-origin resource sharing"
behaviour of the WebSocket server.
* 0 - Do not add an "Access-Control-Allow-Origin:" header to the
response accepting the WebSocket handshake.
* 1 - Add a "Access-Control-Allow-Origin: *" header to the response
accepting the WebSocket handshake.
* 2 - Add a "Access-Control-Allow-Origin:" header containing the same
body as the "Origin:" header from the request to the response
accepting the WebSocket handshake. If there is no "Origin:" header
in the request no header will be added to the response.
Default value is 0.
Example 1.9. Set cors_mode parameter
...
modparam("websocket", "cors_mode", 2)
...
4.8. verbose_list (int)
Allows to enable/disable the printing of debug messages when getting
the list of websocket connections. If enabled, it prints debug messages
every second for ping operations.
Default value is 0 (disabled).
Example 1.10. Set verbose_list parameter
...
modparam("websocket", "verbose_list", 1)
...
4.9. event_callback (str)
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 specific for websocket module.
The function has one string parameter, the value is the name of the
event_route block, respectively "websocket:closed".
Default value is 'empty' (no function is executed for events).
Example 1.11. Set event_callback parameter
...
modparam("websocket", "event_callback", "ksr_websocket_event")
...
-- event callback function implemented in Lua
function ksr_websocket_event(evname)
KSR.info("===== websocket module triggered event: " .. evname .. "\n");
return 1;
end
...
4.10. timer_interval (integer)
The number of seconds between each timer process run
Default value is 1.
Example 1.12. Set timer_intervalparameter
...
modparam("websocket", "timer_interval", 5)
...
4.11. rm_delay_interval (integer)
The number of seconds to wait before destroying the websocket
connection once put in remove state.
Default value is 5.
Example 1.13. Set rm_delay_intervalparameter
...
modparam("websocket", "rm_delay_interval", 2)
...
5. Functions
5.1. ws_handle_handshake()
5.2. ws_close([status, reason[, connection_id]])
5.1. ws_handle_handshake()
This function checks an HTTP GET request for the required headers and
values, and (if successful) upgrades the connection from HTTP to
WebSocket.
This function can be used from ANY_ROUTE (but will only work in
event_route[xhttp:request]).
Note
This function returns 0, stopping all further processing of the
request, when there is a problem. Otherwise, it returns 1 (or positive
number) in case of success.
Example 1.14. ws_handle_handshake usage
...
ws_handle_handshake();
...
5.2. ws_close([status, reason[, connection_id]])
This function closes a WebSocket connection.
The function returns -1 if there is an error and 1 if it succeeds.
The meaning of the parameters is as follows:
* status - an integer indicating the reason for closure.
* reason - a string describing the reason for closure.
* connection_id - the connection to close. If not specified the
connection the current message arrived on will be closed.
Note
status and reason values SHOULD correspond to the definitions in
section 7.4 of RFC 6455. If these parameters are not used the defaults
of "1000" and "Normal closure" will be used.
This function can be used from ANY_ROUTE.
Example 1.15. ws_close usage
...
ws_close(4000, "Because I say so");
...
6. RPC Commands
6.1. ws.dump
6.2. ws.close
6.3. ws.ping
6.4. ws.pong
6.5. ws.disable
6.6. ws.enable
6.1. ws.dump
Provides the details of the first 50 WebSocket connections.
Name: ws.dump
Parameters:
* order (optional) - “id_hash”, “used_desc”, or “used_asc”.
Note
If no parameter is provided id_hash order is used.
RPC Command Usage:
...
kamcmd ws.dump used_asc
...
6.2. ws.close
Starts the close handshake for the specified WebSocket connection.
Name: ws.close
Parameters:
* id - WebSocket connection ID.
RPC Command Usage:
...
kamcmd ws.close: 1
...
6.3. ws.ping
Sends a Ping frame on the specified WebSocket connection.
Name: ws.ping
Parameters:
* id - WebSocket connection ID.
RPC Command Usage:
...
kamcmd ws.ping 1
...
6.4. ws.pong
Sends a Pong frame on the specified WebSocket connection.
Name: ws.pong
Parameters:
* id - WebSocket connection ID.
RPC Command Usage:
...
kamcmd ws.pong 1
...
6.5. ws.disable
Disables WebSockets preventing new connections from being established.
Name: ws.disable
Parameters: none
RPC Command Usage:
...
kamcmd ws.disable
...
6.6. ws.enable
Enables WebSockets allowing new connections to be established.
Note
WebSockets are enabled at start-up.
Name: ws.enable
Parameters: none
RPC Command Format:
...
kamcmd ws.enable
...
7. Event routes
7.1. websocket:closed
7.1. websocket:closed
When defined, the module calls event_route[websocket:closed] when a
connection closes. The connection may be identified using the $si
and $sp pseudo-variables.
Example 1.16. event_route[websocket:closed] usage
...
event_route[websocket:closed] {
xlog("L_INFO", "WebSocket connection from $si:$sp has closed\n");
}
...
8. Exported Pseudo Variables
8.1. $ws_conid
8.1. $ws_conid
Connection id of closed websocket connection. Can only be used in
websocket:closed event route.
Example 1.17. $ws_conid usage
...
event_route[websocket:closed] {
xlog("L_INFO", "WebSocket connection with id $ws_conid has closed\n");
}
...