[asterisk-dev] [Code Review] Fix broken redirect out of MeetMe() as well as the deeper issue at hand

[Russell Bryant]

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https://reviewboard.asterisk.org/r/1082/
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Review request for Asterisk Developers.


Summary
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Mantis issue #18585 reports that a channel redirect out of MeetMe() stopped working properly.  This issue includes a patch that resolves the issue by removing a call to ast_check_hangup() from app_meetme.c.  I left that in my patch, as it doesn't need to be there.  However, the rest of the patch fixes this problem with or without the change to app_meetme.

The key difference between what happens before and after this patch is the effect of the END_OF_Q control frame.  After END_OF_Q is hit in ast_read(), ast_read() will return NULL.  With the ast_check_hangup() removed, app_meetme sees this which causes it to exit as intended.  Checking ast_check_hangup() caused app_meetme to exit earlier in the process, and the target of the redirect saw the condition where ast_read() returned NULL.

Removing ast_check_hangup() works around the issue in app_meetme, but doesn't solve the issue if another application did the same thing.  There are also other edge cases where if an application finishes at the same time that a redirect happens, the target of the redirect will think that the channel hung up.  So, I made some changes in pbx.c to resolve it at a deeper level.  There are already places that unset the SOFTHANGUP_ASYNCGOTO flag in an attempt to abort the hangup process.  My patch extends this to remove the END_OF_Q frame from the channel's read queue, making the "abort hangup" more complete. 


This addresses bug 18585.
    https://issues.asterisk.org/view.php?id=18585


Diffs
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  /branches/1.8/apps/app_meetme.c 303102 
  /branches/1.8/main/pbx.c 303102 

Diff: https://reviewboard.asterisk.org/r/1082/diff


Testing
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I replicated the bug easily.  I verified that removing ast_check_hangup() fixes the issue and determined why it fixes it.  I also verified that the issue is resolved with the pbx.c changes, both with and without ast_check_hangup() still used in app_meetme.


Thanks,

Russell

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