[reSIProcate] terminating a non-responsive or misbehaving dialog/dialogset in DUM

["Justin Matthews" <jmatthewsr@xxxxxxxxx>]

Hi,

A UA is sending an invalid cseq number in a 200Ok response to a re-INVITE.
DUM is consuming this response as a 200OK to the initial INVITE and ACK'ing
the 200.  When trying to end the dialogset & dialog, the invitesession state
gets stuck in WaitingToTerminate because the 200 is never received:

Bad UA          resip/dum
1)  reINVITE (cseq=2) <-
2) 200  (cseq = 1)->
3) ACK <-

There is code in invitesession::end()  where if the state is
WaitingToTerminate, the invitesession will send a BYE and transition to
Terminated (note there is a comment from Scott <slg> about why that code is
there).  This is good because if Bad UA doesn't respond, then a 408 is
expected from the stack and this will destroy the
invitesession/dialog/dialogset.

So to destroy my session I can call end once and then have some timeout
value occur and if the session is not terminated, call end again and it is
then guaranteed to be terminated.?  

Questions/Comments:

1) Would it be bad if this type of functionality is exposed to the dialogset
(dialogset::end) as well (calling end twice)
2) Are there any other scenarios similar to this one that anyone can think
of that would not be solved by calling end twice?
3) Is this problem really just the only known exception that will cause a
session to stay active and can be solved in another way?

Thanks!

-justin