[asterisk-dev] [Code Review] Don't miss control frames if a call is answered and hung up very quickly

[David Vossel]

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Here's an odd case I imagined for this change...

There is a comment around where the HANGUP control frame causes the softhangup flag to be set on the channel in __ast_read() that reads, "Make sure we always return NULL in the future." A HANGUP control frame will result in ast_read returning NULL, but since the HANGUP frame results in the softhangup flag being set, if there were any frames after the HANGUP in the queue they could still be read even after the HANGUP frame came through, which makes this comment invalid after this change.  Whether this matters or not I have no idea.



- David


On 2010-06-23 14:24:05, Terry Wilson wrote:
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> (Updated 2010-06-23 14:24:05)
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> Review request for Asterisk Developers and Russell Bryant.
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> Summary
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> When an outgoing call is answered and hung up by the far end *very* quickly, we may not read any frames and therefor end up with a call that displays the wrong disposition/DIALSTATUS. The reason is because ast_queue_hangup() immediately sets the _softhangup flag on the channel and then queues the HANGUP control frame, but __ast_read refuses to read any frames if ast_check_hangup() indicates that a hangup request has been made (which it will if _softhangup is set). So, we end up losing control frames.
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> This change makes __ast_read continue to read frames even if a soft hangup has been requested. I believe this should be safe as we actually check farther down in __ast_read for HANGUP frames and return NULL just like we would have if we skipped the read via the goto done statement, and we don't call into any of the channel tech callbacks unless the readq is empty.
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> This addresses bug 16946.
>     https://issues.asterisk.org/view.php?id=16946
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> Diffs
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>   /trunk/main/channel.c 272124 
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> Diff: https://reviewboard.asterisk.org/r/740/diff
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> Testing
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> I have verified via sipp that when placing an outbound call that is answered and immediately hung up that the call shows up as answered (where it doesn't w/o the patch). I have also run the testsuite and verified that all tests continue to pass.
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> Thanks,
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> Terry
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>