Testing the Kamailio Outbound Module - sr-users

29 Jan 2026


      Hi, team
# Testing the Kamailio Outbound Module
Kamailio version: 6.0.5
OS: Debian 12
Kamailio IP: 192.168.149.18, Port: 5060
FreeSWITCH (REGISTRAR) IP: 192.168.149.18, Port: 6666
MicroSIP IP: 192.168.149.35, transport protocol: TCP
## Signaling Flows
MicroSIP => REGISTER => Kamailio => FreeSWITCH, this is OK
MicroSIP => INVITE => Kamailio => FreeSWITCH, this is OK also
However, executing `fs_cli -x 'show registrations as xml'` on FreeSWITCH returns the following:
```xml
<result row_count="1">
  <row row_id="1">
    <reg_user>1001</reg_user>
    <realm>192.168.149.18</realm>
    <token>992b228842f841fda057da1883e5317a</token>
    <url>sofia/internal/sip:1001@192.168.149.35:49676;transport=TCP;ob;fs_path=%3Csip%3A192.168.149.18%3Blr%3E</url>
    <expires>1769678856</expires>
    <network_ip>192.168.149.18</network_ip>
    <network_port>5060</network_port>
    <network_proto>tcp</network_proto>
    <hostname>debian</hostname>
    <metadata></metadata>
  </row>
</result>
```
Command executed:
`fs_cli -x 'originate user/1001 &park'`
The INVITE message is as follows:
```
INVITE sip:1001@192.168.149.35:59527;transport=TCP;ob SIP/2.0
Via: SIP/2.0/UDP 192.168.149.18:6666;rport;branch=z9hG4bK0mU9ryZD57S0p
Route: sip:192.168.149.18;lr
Max-Forwards: 70
From: sip:0000000000@192.168.149.18;tag=97mDae4gQHXFa
To: sip:1001@192.168.149.35:59527;transport=TCP;ob
Call-ID: a59d2625-7790-123f-979c-0800279269e8
CSeq: 110284145 INVITE
Contact: sip:mod_sofia@192.168.149.18:6666
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
Supported: outbound, path, replaces
Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer
Content-Type: application/sdp
Content-Disposition: session
Content-Length: 764
X-FS-Support: update_display,send_info
Remote-Party-ID: sip:0000000000@192.168.149.18;party=calling;screen=yes;privacy=off
```
...
However, the log shows "client to registrar" instead of "registrar to client".
What is the reason for this?
The contents of kamailio.cfg are as follows:
```
#!KAMAILIO
#
# Edge proxy configuration
#
listen=tcp:192.168.149.18:5060
listen=udp:192.168.149.18:5060
#!subst "/REGISTRAR_IP/192.168.149.18/"
#!subst "/REGISTRAR_PORT/6666/"
#!substdef "/FLOW_TIMER/20/"
####### Global Parameters #########
auto_aliases=no
debug=2
log_stderror=no
log_facility=LOG_LOCAL0
log_prefix="{$mt $hdr(CSeq) $ci} "
fork=yes
children=4
alias="example.com"
#mpath="/usr/lib64/kamailio/modules"
tcp_connection_lifetime=30 # FLOW_TIMER + 10
force_rport=yes
####### 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 "textops.so"
loadmodule "siputils.so"
loadmodule "stun.so"
# ----------------- setting module-specific parameters ---------------
# ----- 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();
    	$du = "sip:REGISTRAR_IP:REGISTRAR_PORT";
    } else {
    	if (is_method("INVITE|SUBSCRIBE"))
    		record_route();
if (@via[2] == "") {
    		# From client so route to registrar...
    		xinfo("client to registrar\n");
    		if ($rU == $null) {
    			sl_send_reply("484", "Address Incomplete");
    			exit;
    		}
    		remove_hf("Route");
    		$du = "sip:REGISTRAR_IP:REGISTRAR_PORT";
    	} else {
    		# From registrar so route using "Route:" headers...
    		xinfo("registrar to client\n");
    		if (!loose_route()) {
    			switch($rc) {
    			case -2:
    				sl_send_reply("403", "Forbidden");
    				exit;
    			default:
    				xlog("L_ERR", "in request_route\n");
    				sl_reply_error();
    				exit;
    			}
    		}
t_on_failure("FAIL_OUTBOUND");
    	}
    }
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");
    }
}
```