Out of dialog REFER requests

[wakamoleguy]

It is possible to receive REFER requests as initial, out-of-dialog requests. Some phone systems use this mechanism for third party call control behavior of some kind. At the moment, SIP.js will reject the request with 405 Method Not Allowed.

I believe this would be possible to implement similarly to our MESSAGE handling. That is, we add a ua.on('refer', callback) event. If the application defines such a callback, call it. Otherwise, reject with 405.

As for the actual behavior of the REFER, check RFC 3515. It should be similar to in-dialog REFER, although we probably don't want to provide the convenience method. Doing so would encourage applications to implement this behavior without prompting the user. Per the RFC, the user SHOULD be prompted for permission.

[josephfrazier]

I'm taking a crack at this over at joseph-onsip:oodREFER

[josephfrazier]

Alright, I've gotten this to the point where the UA, upon receiving an out-of-dialog REFER, will first reply with 202, then (theoretically) send a NOTIFY with 603 or 100, depending on whether a 'refer' listener is present on the UA. This is analogous to the way in-dialog REFERs are handled.

However, the NOTIFY portion of things doesn't yet work, because the NOTIFY needs to be sent in the dialog established by the 202, but I haven't been able to make that work, so I'm unassigning myself for now.

[egreenmachine]

Can you try out #459? I think that I have addressed this issue there. You will need to enable allowOutOfDialogRefer on the UA. Any user that uses this feature should implement some security to validate the out of dialog refer, otherwise it could be used maliciously.

• Due to the age of this issue, if we do not hear any feedback on this we will close it once we merge the pull request.