[sr-dev] [tracker] Task opened: handle dialog tracking properly when non-failing 4xx responses are involved

[sip-router]

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User who did this - Timo Reimann (tr) 

Attached to Project - sip-router
Summary - handle dialog tracking properly when non-failing 4xx responses are involved
Task Type - Bug Report
Category - dialog
Status - Assigned
Assigned To - Timo Reimann
Operating System - All
Severity - Medium
Priority - Normal
Reported Version - Development
Due in Version - Undecided
Due Date - Undecided
Details - When a dialog is tracked that returns a response containing any of the  response codes defined in section 8.1.3.5 of RFC 3261[1], the standard requires (according to section 8.1.1.4[2]) that the dialog must *not* be considered as a failure. A typical example call flow involves client authentication:

INVITE(no-auth) -> 407 -> ACK -> INVITE(auth) -> ...

If the dialog is already tracked at the unauthenticated INVITE the module will consider the dialog to have failed on routing of the 407 message. Instead, it should facilitate "reusing" the dialog once the authenticated INVITE arrives and tracking the call properly.

A suggested fix is to adjust the state machine to exclude the set of non-failing 4xx return codes from constituting a DLG_STATE_FAILED state and continue tracking when the authenticated INVITE is parsed. Caution must be taken in conjunction with the spiral detection code to implement this properly.


[1] http://tools.ietf.org/html/rfc3261#section-8.1.3.5
[2] http://tools.ietf.org/html/rfc3261#section-8.1.1.4

More information can be found at the following URL:
http://sip-router.org/tracker/index.php?do=details&task_id=146

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