[asterisk-dev] [Code Review] Call pickup race leaves orphaned channels or crashes.

[Alec Davis]

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/branches/1.8/main/channel.c
<https://reviewboard.asterisk.org/r/1400/#comment8218>

    should setting a channel to a ZOMBIE also be done in features.c:set_kill_chan_tech(... ) and any where else before chan->tech->hangup(chan) is called?


- Alec


On Aug. 29, 2011, 6:51 p.m., rmudgett wrote:
> 
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> (Updated Aug. 29, 2011, 6:51 p.m.)
> 
> 
> Review request for Asterisk Developers, Alec Davis and irroot.
> 
> 
> Summary
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> 
> Attempting to pickup a call that has been forked to multiple extensions by two users either crashes or fails a masquerade with a "bad things may happen" message.
> 
> This is the scenario that is causing all the grief:
> 1) Pickup target is selected
> 2) target is marked as being picked up in ast_do_pickup()
> 3) target is unlocked by ast_do_pickup()
> 4) app dial or queue gets a chance to hang up losing calls and calls ast_hangup() on target
> 5) SINCE A MASQUERADE HAS NOT BEEN SETUP YET BY ast_do_pickup() with ast_channel_masquerade(), ast_hangup() completes successfully and the channel is no longer in the channels container.
> 6) ast_do_pickup() then calls ast_channel_masquerade() to schedule the masquerade on the dead channel.
> 7) ast_do_pickup() then calls ast_do_masquerade() on the dead channel
> 8) bad things happen while doing the masquerade and in the process ast_do_masquerade() puts the dead channel back into the channels container
> 9) The "orphaned" channel is visible in the channels list if a crash does not happen.
> 
> This patch does the following:
> 1) ast_hangup() sets the zombie flag on a successfully hung-up channel and does not release the channel lock until that has happened.
> 2) __ast_channel_masquerade() is fixed to not setup a masquerade if either channel is a zombie.
> 
> 
> This addresses bugs ASTERISK-18222 and ASTERISK-18273.
>     https://issues.asterisk.org/jira/browse/ASTERISK-18222
>     https://issues.asterisk.org/jira/browse/ASTERISK-18273
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> 
> Diffs
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>   /branches/1.8/main/channel.c 333893 
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> Diff: https://reviewboard.asterisk.org/r/1400/diff
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> 
> Testing
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> Replicated the crash in ASTERISK-18222 with PickupChan() and *8 methods.
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> With the patch, the crash no longer happens and the new message of attempting to masquerade into a dead channel is output.
> 
> 
> Thanks,
> 
> rmudgett
> 
>

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