I was looking into the crash reported in ASTERISK-26718 and I have uploaded two
changes into gerrit to fix the symptom[1] and hopefully address the cause[2] as
well. It would be nice if anyone with a better understanding of stasis and the
bridging code can provide feedback.
The crash appears to happen because the stasis control app is unlinked/deleted
before the registered after bridge callback is called on the channel which is
then following a dangling pointer (use after free). This can happen if
imparting the call back to the dial bridge fails.
When imparting fails I am now calling ast_bridge_discard_after_callback to
cancel the outstanding callback and the crash vanishes. It prints more error
messages of having failed to impart the channel but doesn't crash anymore.
Having fixed the symptom/crash I tried to understand the cause. The log message
already provides a lot of details:
WARNING[5290][C-00000a96] bridge.c: Channel PJSIP/ic_proxy_endpoint-00000a95
has a PBX thread and cannot be imparted into bridge
4c35dd9c-4f74-4fdb-af35-261dfd875c04
My attempt is to "park" the pbx in the stasis control. I have placed it the
depart_channel function before calling add_to_dial_bridge. This makes the
warning disappear (and I didn't hit the assert) in my manual tests. Is this the
right fix and the right place to fix it? Should it be moved into
add_to_dial_bridge?
looking forward to get your feedback
holger
[1] https://gerrit.asterisk.org/c/asterisk/+/11254
[2] https://gerrit.asterisk.org/c/asterisk/+/11255
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