[SR-Users] Re: How to correctly generate a 181 Call is being forwarded reply?

[Patrick Karton via sr-users]

You can send a 181 but no put a to-tag in it with jsonrpc fonction like this.

 if (is_method("INVITE") && !has_totag() && t_newtran()){

  # transaction must have been created

  $var(jsRPCCode) = 181;

  $var(jsRPCText) = "Call is being forwarded";

  $var(jsRPCTotag) = ""; # don't put to-tag in 181

  $var(jsRPCHeaders) = "";

  $var(jsRPCBody) = "";

         if ( !jsonrpc_exec('{"jsonrpc": "2.0",

                                      "method": "tm.reply_callid",

                                       "params": [$var(jsRPCCode),

                                          "$var(jsRPCText)",

                                          "$ci", "$cs", "$var(jsRPCTotag)", "$var(jsRPCHeaders)", "$var(jsRPCBody)"]}') || $jsonrpl(code) != 200 )

                    xlog("JSONRPC[ERROR][tm.reply_callid] : $jsonrpl(body)\n");

 }

Le 1 déc. 2025 20:00, Patrick Karton <patrickar...@hotmail.com> a écrit :

Loose_route() does not check transaction but route headers if any.

You are trying to do b2bua operations with kamailio by sending 181 through it (hence it will create a to-tag that does not belong to no one and will never be used after).

It's typically a kind of action you can't/shouldn't/must not do in kamailio.

Le 1 déc. 2025 15:14, Benoit Panizzon via sr-users <sr-users@lists.kamailio.org> a écrit :

Hi again

> I don't seem to get it working as expected - still trying to figure out
> what and where the call fails.

I think I have found what goes wrong.

A => B => CFW => C

C has MIN-SE: 900
A is initially sending Sestion-Timer: 600

Without 181 reply:

C replies with 422 Timer too Small Min-SE: 900
This 422 Reply has a ToTag.

A re-initiates the call with a larger session timer, that INVITE has NO
ToTag - new transaction. The Calls succeeds.

Now I repeat the same, but I send a 181 message back to A BEFORE A
receives the 422 from C. That 181 has a ToTag.

Now when A re-initiates the INVITE, it includes the ToTag received in
the 181 and loose_route fails as there is no such transaction.

Is A misbehaving by including a ToTag when it should not? Should the 181
reply not contain a ToTag?

I again tried all variants

* sl_send_reply() generates ToTag
* send_reply() generates ToTag
* t_reply() does not send the reply.

Mit freundlichen Grüssen

-Benoît Panizzon-
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