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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/4354/">https://reviewboard.asterisk.org/r/4354/</a>
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<p style="margin-top: 0;">On January 19th, 2015, 4:24 p.m. CST, <b>Matt Jordan</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/4354/diff/1/?file=70757#file70757line460" style="color: black; font-weight: bold; text-decoration: underline;">/branches/13/include/asterisk/bridge.h</a>
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">enum ast_bridge_join_flags {</pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"> * good idea to access the swap channel on return or for the caller to keep a</span></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"> * reference to it.</span></pre></td>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Why is it not a good idea for the caller to have their own reference, if they bump the reference to cover the stealing by this function?
That is, why is the following unsafe:
swap = ast_channel_find(...);
ast_channel_ref(swap);
ast_bridge_join(bridge, chan, swap);
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<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">If you do that then the swap channel will linger in the stasis cache until chan comes out of the bridging system; which is likely long after the swap channel has been hung up. Remember ast_bridge_join() is blocking.</pre>
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<p style="margin-top: 0;">On January 19th, 2015, 4:24 p.m. CST, <b>Matt Jordan</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/4354/diff/1/?file=70760#file70760line1601" style="color: black; font-weight: bold; text-decoration: underline;">/branches/13/main/bridge.c</a>
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">int ast_bridge_join(struct ast_bridge *bridge,</pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="n">ao2_t_cleanup</span><span class="p">(</span><span class="n">bridge_channel</span><span class="o">-></span><span class="n">swap</span><span class="p">,</span> <span class="s">"Bridge complete: join failed"</span><span class="p">);</span></pre></td>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">I don't think the join actually failed here. This should just get called when bridge_channel_internal_join returns, which could occur when the channel was released from the bridge. If I'm wrong, feel free to disregard :-)</pre>
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<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">If bridge_channel->swap is non-NULL here then the join really did fail and the unref is logged to REF_DEBUG as a result of join failure. If it is NULL then there is no unref and no corresponding REF_DEBUG log entry. ao2_cleanup() is a conditional unref. bridge_channel_internal_join() is blocking so bridge_channel->swap cannot still have a ref if the channel successfully joined.</pre>
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<p>- rmudgett</p>
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<p>On January 19th, 2015, 2:31 p.m. CST, rmudgett wrote:</p>
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<div>Review request for Asterisk Developers.</div>
<div>By rmudgett.</div>
<p style="color: grey;"><i>Updated Jan. 19, 2015, 2:31 p.m.</i></p>
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<b style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Bugs: </b>
<a href="https://issues.asterisk.org/jira/browse/ASTERISK-24649">ASTERISK-24649</a>
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<b style="color: #575012; font-size: 10pt;">Repository: </b>
Asterisk
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">When code imparts a channel into a bridge to swap with another channel, a ref needs to be held on the swap channel to ensure that it cannot dissapear before finding it in the bridge.
* The ast_bridge_join() swap channel parameter now always steals a ref for the swap channel. This is the only change to the bridge framework's public API semantics.
* bridge_channel_internal_join() now requires the bridge_channel->swap channel to pass in a ref.</pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">The testsutite masquerade super test and the --tags=transfer tests still pass.</pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>/branches/13/main/bridge_channel.c <span style="color: grey">(430794)</span></li>
<li>/branches/13/main/bridge.c <span style="color: grey">(430794)</span></li>
<li>/branches/13/include/asterisk/bridge_internal.h <span style="color: grey">(430794)</span></li>
<li>/branches/13/include/asterisk/bridge_channel_internal.h <span style="color: grey">(430794)</span></li>
<li>/branches/13/include/asterisk/bridge.h <span style="color: grey">(430794)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/4354/diff/" style="margin-left: 3em;">View Diff</a></p>
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