[OpenSER-Devel] [ openser-Feature Requests-1968908 ] Allow "append_branch" in FAILURE_ROUTE if best reply is 6XX

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Feature Requests item #1968908, was opened at 2008-05-21 18:31
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Category: core
Group: ver devel
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Iñaki Baz (ibc_sf)
Assigned to: Nobody/Anonymous (nobody)
Summary: Allow "append_branch" in FAILURE_ROUTE if best reply is 6XX

Initial Comment:
Actually OpenSer doesn't allow "append_branch" in FAILURE ROUTE if the best negative reply received is a 6XX. It's done in this way to be RFC 3261 compliant since 6XX means "global failure and no further forking is allowed".

In this way if we implement a voicemail forwarding system based of FAILURE ROUTE it just will work if the called user rejected the call with a 4XX code (480, 486...) but if it used a 6XX then OpenSer won't create a new branch to forward the INVITE to the voicemail. Also note that some UA's use 4XX and others 6XX to reject a call.


But I'm really not sure that OpenSer would break the RFC 3261 if it allows creating a new branch **AFTER** choosing the best response even if it was a 6XX:

FAILURE_ROUTE is executed when all the branches have finished, all of them with a negative response. Then the "best" response is chosen by OpenSer and its code is what we can see if we run:
  t_check_status("XXX")
in FAILURE_ROUTE.

So, I don't think that using "append_branch()" into FAILURE_ROUTE is anti-RFC3261, the steps are:

- OpenSer receives an INVITE and forks it to the user locations.
- OpenSer receives a 480, 486 and 603.
- It chooses 603 as best response.
- It runs the FAILURE_ROUTE in which a "append_branch" is executed.
- The INVITE is forwarded to a media server.

The new branch has been created **AFTER** choosing the best response from "real" branches. The FAILURE_ROUTE is part of our proxy logic, so IMHO those steps are not anti-RFC3261 at all.


So I propose that OpenSer can generate a new branch in FAILURE ROUTE even if the best response was a 6XX.

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