Outbound Module
 
 Peter Dunkley
 
    Crocodile RCS Ltd
 

    Copyright © 2012 Crocodile RCS Ltd

      __________________________________________________________________
 
    Table of Contents
 
    1. Admin Guide
 
         1. Overview

 
               1.1. Edge Proxy Keep-Alives (STUN)
               1.2. Flow Timer
 

         2. Dependencies
 
               2.1. Kamailio Modules
               2.2. External Libraries or Applications
 
         3. Parameters

               3.1. force_outbound_flag (integer)

         4. Functions
         5. MI Commands
 

    List of Examples
 

    1.1. Edge Proxy Configuration
    1.2. Registrar Configuration
    1.3. Set force_outbound_flag parameter

 Chapter 1. Admin Guide
 
    Table of Contents
 
    1. Overview

 
         1.1. Edge Proxy Keep-Alives (STUN)
         1.2. Flow Timer
 

    2. Dependencies
 
         2.1. Kamailio Modules
         2.2. External Libraries or Applications
 
    3. Parameters

         3.1. force_outbound_flag (integer)

    4. Functions
    5. MI Commands
 
 1. Overview
 

    1.1. Edge Proxy Keep-Alives (STUN)
    1.2. Flow Timer
 
    This module provides C-API functions to enable Kamailio to be used as
    an outbound Edge Proxy (see RFC 5626 section 5).
 
    The path and rr will bind to this module if it is loaded before they
    are.
 
 1.1. Edge Proxy Keep-Alives (STUN)
 
    Outbound Edge Proxies MUST support STUN NAT keep-alives on their SIP

    UDP ports. Kamailio supports this though the “stun” module.

 
 1.2. Flow Timer
 
    The maximum interval at which a User Agent must send a keep-alive may
    be specified by the Registrar using the Flow-Timer: header in 2xx
    responses to REGISTERs.
 
    When using TCP or TLS as the SIP transport care should be taken to set

    the “tcp_connection_lifetime” on the Edge Proxy to a value slightly

    larger than the interval the Registrar is using for flow timer. Setting

    “tcp_connection_lifetime” to less than the interval could cause

    connections to be lost, and setting it to a value much larger than the
    interval will keep connections open far longer than is required (which
    is wasteful).
 
    Application-layer keep-alives are optional when the underlying
    transport already has a keep-alive mechanism. The WebSocket transport
    has a transport-layer keep-alive. When using the WebSocket transport

    the “keepalive_timeout” should be set to a value a little greater than

    the Registrar flow timer interval and a little less than the

    “tcp_connection_lifetime”.

    Example 1.1. Edge Proxy Configuration

 #!KAMAILIO
 #
 # Edge proxy configuration
 #
 
 #!subst "/REGISTRAR_IP/192.168.122.3/"
 #!subst "/REGISTRAR_PORT/5060/"
 #!substdef "/FLOW_TIMER/20/"
 
 ####### Global Parameters #########
 
 debug=2
 log_stderror=no
 log_facility=LOG_LOCAL0
 fork=yes
 children=4
 alias="example.com"
 mpath="/usr/lib64/kamailio/modules"
 tcp_connection_lifetime=30 # FLOW_TIMER + 10
 
 
 ####### Modules Section ########
 
 loadmodule "tm.so"
 loadmodule "sl.so"

 loadmodule "outbound.so"
 loadmodule "rr.so"
 loadmodule "path.so"

 loadmodule "pv.so"
 loadmodule "maxfwd.so"
 loadmodule "xlog.so"
 loadmodule "sanity.so"
 loadmodule "ctl.so"
 loadmodule "mi_rpc.so"
 loadmodule "mi_fifo.so"
 loadmodule "textops.so"
 loadmodule "siputils.so"

 loadmodule "stun.so"

 # ----------------- setting module-specific parameters ---------------

 # ----- mi_fifo params -----
 modparam("mi_fifo", "fifo_name", "/tmp/kamailio_fifo")

 # ----- tm params -----
 modparam("tm", "failure_reply_mode", 3)
 
 # ----- rr params -----
 modparam("rr", "append_fromtag", 0)
 
 
 ####### Routing Logic ########
 
 request_route {
         route(REQINIT);
 
         if (is_method("CANCEL")) {
                 if (t_check_trans()) {
                         route(RELAY);

                 }

                 exit;
         }
 
         route(WITHINDLG);
 
         t_check_trans();

         if (is_method("REGISTER")) {
                 remove_hf("Route");

                 add_path();

                 $du = "sip:REGISTRAR_IP:REGISTRAR_PORT";
         } else {
                 if (is_method("INVITE|SUBSCRIBE"))
                         record_route();
 
                 if ($si == "REGISTRAR_IP" && $sp == "REGISTRAR_PORT") {
                         if (!loose_route()) {
                                 switch($rc) {
                                 case -2:
                                         sl_send_reply("403", "Forbidden");
                                         exit;
                                 default:
                                         sl_reply_error();
                                         exit;
                                 }
                         }
 
                         t_on_failure("FAIL_OUTBOUND");
                 } else {
                         if ($rU == $null) {
                                 sl_send_reply("484", "Address Incomplete");
                                 exit;
                         }
                         remove_hf("Route");
                         $du = "sip:REGISTRAR_IP:REGISTRAR_PORT";

                 }
         }

 
         route(RELAY);

 }
 
 route[RELAY] {
         if (!t_relay()) {

                 sl_reply_error();

         }
         exit;
 }

 
 route[REQINIT] {
         if (!mf_process_maxfwd_header("10")) {
                 sl_send_reply("483","Too Many Hops");
                 exit;
         }
 
         if(!sanity_check("1511", "7"))
         {
                 xlog("Malformed SIP message from $si:$sp\n");
                 exit;
         }
 }
 

 route[WITHINDLG] {
         if (has_totag()) {
                 if (!loose_route()) {
                         switch($rc) {
                         case -2:
                                 sl_send_reply("403", "Forbidden");
                                 exit;

                         default:

                                 if (is_method("ACK")) {

                                         if ( t_check_trans() ) {
                                                 route(RELAY);

                                                 exit;
                                         } else {
                                                 exit;
                                         }
                                 }

                                 sl_send_reply("404","Not Found");

                         }
                 } else {

                         if (is_method("NOTIFY")) {
                                 record_route();
                         }

                         route(RELAY);
                 }
                 exit;
         }

 }

 onreply_route {
         if (!t_check_trans()) {
                 drop;
         }
 

         if ($rm == "REGISTER" && $rs >= 200 && $rs <= 299) {
                 remove_hf("Flow-Timer");

                 if ($(hdr(Require)[*])=~"outbound")
                         insert_hf("Flow-Timer: FLOW_TIMER\r\n", "Call-ID");
         }
 }
 

 failure_route[FAIL_OUTBOUND]{

         if (t_branch_timeout() || !t_branch_replied()) {
                 send_reply("430", "Flow Failed");
         }
 }
 

    Example 1.2. Registrar Configuration

 ...

 loadmodule "tm.so"
 ...

 loadmodule "registrar.so"
 ...

 modparam("tm", "contacts_avp", "tm_contacts")
 modparam("tm", "contact_flows_avp", "tm_contact_flows")
 ...
 modparam("registrar", "use_path", 1)
 modparam("registrar", "path_mode", 2)

 modparam("registrar", "outbound_mode", 2)

 ...
 route[LOCATION] {
 ...
         if (!lookup("location")) {
                 $var(rc) = $rc;
                 route(TOVOICEMAIL);
                 t_newtran();
                 switch ($var(rc)) {
                         case -1:
                         case -3:
                                 send_reply("404", "Not Found");
                                 exit;
                         case -2:
                                 send_reply("405", "Method Not Allowed");
                                 exit;
                 }
         }
 
         if (!t_load_contacts()) {
                 send_reply("500", "Server Internal Error");
                 exit;
         }
 
         if (!t_next_contacts()) {
                 send_reply("500", "Server Internal Error");
                 exit;
         }
 

         t_on_failure("FAIL_OUTBOUND");

 ...
 }
 ...
 failure_route[FAIL_OUTBOUND] {
         if (t_check_status("408|430")) {
                 if (!t_next_contact_flows() && !t_next_contacts()) {
                         send_reply("500", "Server Internal Error");
                         exit;
                 }
         } else if (!t_next_contacts()) {
                 send_reply("500", "Server Internal Error");
                 exit;
         }
 

         t_on_failure("FAIL_OUTBOUND");
         route(RELAY);

 }

 ...

 
 2. Dependencies
 
    2.1. Kamailio Modules
    2.2. External Libraries or Applications
 
 2.1. Kamailio Modules
 

    The following modules must be loaded before this module:
      * None

 
 2.2. External Libraries or Applications
 
    The following libraries must be installed before running Kamailio with
    this module loaded:
      * OpenSSL.
 
 3. Parameters
 

    3.1. force_outbound_flag (integer)

 3.1. force_outbound_flag (integer)

    A flag which, if set for a request, will force path and rr to add flow
    tokens to Path: and Record-Route: headers regardless of the request
    contents.

 
    Default value is -1.
 

    Example 1.3. Set force_outbound_flag parameter

 ...

 modparam("outbound", "force_outbound_flag", 1)

 ...

 4. Functions
 

    None

 
 5. MI Commands
 

    None