Hi Kamailio list,

I hope you are all well?

I am looking for some assistance on a specific error I am trying to work around.

Kamailio 5.5.3 - Ubuntu 20.04

Kemi Python script (but I think this is more default failure_route behaviour)

Dispatcher module which hunts to a group of FreeSWITCH that I have configured to send 503 responses on.

My scenario is fairly simple, I am trying to respond back to a carrier for huntable responses (503 specifically) by calling a failure route below:

def ksr_failure_manage(self, msg):

    if KSR.tm.t_any_timeout()>0 :

        self.ksr_send_reply_clear_rtpengine(msg, 503, "Timeout to destination")

        KSR.err("Timeout to Invite for %s from IP %s" % (KSR.pv.get("$ci"),KSR.pv.get("$si")))

        return 1

    else:

        self.ksr_send_reply_clear_rtpengine(msg, 503, "Unknown error failover to next node")

        KSR.err("Failed but not timeout for %s from IP %s" % (KSR.pv.get("$ci"),KSR.pv.get("$si")))

        return 1

This works and a 503 with the correct message is sent if the invite doesn't get a response after 2 seconds. (My specific test case here)

# Timers for call setup 2 minutes for any 1xx provisional response received

# If no invite response received in 2 seconds end the call as per failure route.

        KSR.tm.t_set_fr(120000, 2000)

        self.ksr_route_relay(msg)

        KSR.tm.t_on_failure("ksr_failure_manage")

        return -255

The issue is after a few more milliseconds after my initial 503 a 408 is sent. Also after the failover if the carrier tries the same Kamailio again it gets a 500 rather than a 408.

408:

500:

My steps to get around this have been to change the default tm code to 503 below, but this has not changed the default response and the above behaviour unfortunately:

# ----- tm params -----

# auto-discard branches from previous serial forking leg

modparam("tm", "failure_reply_mode", 3)

# setting default reason code and response for general errors to allow failover.

modparam("tm", "default_code", 503)

modparam("tm", "default_reason", "Unknown reason try next node")

My question is: How can I make sure my failure route is the final response here. Or if I cannot make sure of this, how can I change the default mapped response to be a consistent SIP response (503 specifically)

Many thanks in advance as I am scratching my head on this one a bit.

John.