Hello,
actually you are wrong that you think it is a wrong to tag. The entity that generates the final reply sets the to-tag (e.g.,to be able to match ack). Even here where you talk about the serial forking, you are going to face the case of different to-tag values for each branch sent out and replied. But also think about parallel forking, that timed out with many active branches, which to-tag to use?!?
So think that kamailio itself is the branch of the incoming request, and can create many outgoing branches. If it generates a final reply, it does it to the incoming branch. It is not forwarding (sending back) a reply from an outgoing branch.
Obviously, being open source, one can code a specific behaviour for some specific needs, but is not SIP specs compliant. If the upstream cannot deal with different to-tags, it won't really work with serial/parallel forking anyhow.
As a side remark, seeing the comments, if route(ROUTE_ELEMENT_FINAL_FAILURE) is used only in failure_route, then transaction is always defined there, because failure_route is executed only in the transaction context. Anyhow, if you are using in many places, not knowing if transaction was created, you can use send_reply() to avoid any test in the config.
Cheers, Daniel
On 11.12.20 11:04, Ivan Ribakov wrote:
Hi all,
I’m trying to implement following routing behaviour:
- ingress INVITE is sequentially forked to 1 or more endpoints
- under certain conditions sequential forking may be stopped and
pre-defined error returned to the caller
Here’s is part of the config responsible for handling errors:
failure_route[ROUTE_ELEMENT_FINAL_FAILURE_HELPER] { route(ROUTE_ELEMENT_FINAL_FAILURE); } route[ROUTE_ELEMENT_FINAL_FAILURE] { # We need to check if the error happens before the first egress, because T-state is not defined yet so we can not use t_reply if ($var(before_first_egress) == 0) { t_reply("$var(sipCode)", "$var(sipMessage)"); } else { sl_send_reply("$var(sipCode)", "$var(sipMessage)"); } }
Here is a simple scenario where delivering call to first endpoint times out after receiving 180 Ringing (using custom fr_inv_timer value) where:
- .33 is caller
- .208 is Kamailio
- .138 is callee
Notice that 504 is retransmitted by Kamailio. Here is a comparison of 180 and 504 returned by Kamailio:
As can be seen, 180 was proxied from the callee and has callee’s to-tag (tag=CALLEE1), however 504 that was generated by Kamailio using t_reply() has a different to-tag (presumably generated by Kamailio).
How can I tell Kamailio not to generate new to-tag but to use the last one that proxied back to the caller?
Thanks in advance for any help!
Regards, Ivan
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