[asterisk-dev] [Code Review] Prevent NewChannel manager event when channel is created solely for variable substitution purposes

[Tilghman Lesher]

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Ship it!


- Tilghman


On 2010-03-31 13:59:29, Mark Michelson wrote:
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> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/601/
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> 
> (Updated 2010-03-31 13:59:29)
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> Review request for Asterisk Developers.
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> Summary
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> Issue 16957 was opened because there were NewChannel events being fired which did not have a matching Hangup event. In this particular example, the NewChannel events were being sent due to an unavailable device when attempting an originate action. ast_pbx_outgoing_cdr_failed() created a new channel solely for variable substitution, leading to a NewChannel event. Rather than calling ast_hangup on the channel, ast_channel_free was called instead.
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> My solution for this is to make a slight alteration to ast_channel_alloc_ap() such that we determine whether to send a NewChannel manager event based on whether the channel technology is one that is registered. Technologies such as "Bogus" as used by the manager and "Substitution" as used by voicemail will not result in NewChannel events. My understanding is that an Asterisk administrator would not care about these channels since they are not "proper" channels but rather a mechanism of convenience for the Asterisk developer to facilitate variable substitution.
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> An alternate solution, proposed by Atis Lezdins, is instead to backport ast_dummy_channel_alloc() from trunk to all affected branches. I am certainly open to this idea; however, I don't feel it is right for me to make such a decision on my own and would like feedback from other developers on the matter. The main advantage to ast_dummy_channel_alloc() is that it is a lightweight channel allocation mechanism designed specifically for facilitating variable substitution. The only drawback I can think of is that this would require touching more code. Anyway, tell me what you think.
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> This addresses bug 16957.
>     https://issues.asterisk.org/view.php?id=16957
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> Diffs
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>   /branches/1.6.1/main/channel.c 255505 
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> Diff: https://reviewboard.asterisk.org/r/601/diff
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> Testing
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> I used the AMI GetVar action like so:
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> Action: GetVar
> Channel:
> Variable: CALLERID(name)
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> Doing so without the patch caused a NewChannel event to be generated. Doing so with the patch caused no such NewChannel event to be generated. I also made sure that NewChannel events were emitted when SIP channels placed calls.
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> Thanks,
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> Mark
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>