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

[rmudgett]

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This is an automatically generated e-mail. To reply, visit:
https://reviewboard.asterisk.org/r/1400/
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(Updated Aug. 30, 2011, 2:28 p.m.)


Review request for Asterisk Developers, Alec Davis and irroot.


Changes
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Fix chan_agent abuse of the ZOMBIE flag that the patch makes no longer work.


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


Diffs (updated)
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  /branches/1.8/channels/chan_agent.c 333945 
  /branches/1.8/main/channel.c 333945 

Diff: https://reviewboard.asterisk.org/r/1400/diff


Testing
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Replicated the crash in ASTERISK-18222 with PickupChan() and *8 methods.

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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