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Fix crash when receiving a message that wants an ack on a closed exchange that's still alive. #8068
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…ange that's still alive. The basic scenario, with all messages requesting acks, is: 1) A sends message to B. 2) B responds to A, piggybacks ack, closes exchange. 3) A responds to B, piggybacks ack. When B receives the message, the exchange is still alive, waiting for an ack. It gets the message handed to it, processes it, queues up an ack for the message it just got. Then the stack unwinds, the exchange's refcount drops to 0 (because it's no longer waiting for an ack, so not referenced by the reliable message manager), and its destructor tries to flush the pending ack, which fails assertions due to the refcount being 0. The fix is to always immediately send a standalone ack if we have no delegate, because in that situation there won't be anything app-level to piggyback on.
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Size increase report for "esp32-example-build" from 8551b50
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Size increase report for "nrfconnect-example-build" from 8551b50
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Size increase report for "gn_qpg6100-example-build" from 8551b50
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…ange that's still alive. (project-chip#8068) The basic scenario, with all messages requesting acks, is: 1) A sends message to B. 2) B responds to A, piggybacks ack, closes exchange. 3) A responds to B, piggybacks ack. When B receives the message, the exchange is still alive, waiting for an ack. It gets the message handed to it, processes it, queues up an ack for the message it just got. Then the stack unwinds, the exchange's refcount drops to 0 (because it's no longer waiting for an ack, so not referenced by the reliable message manager), and its destructor tries to flush the pending ack, which fails assertions due to the refcount being 0. The fix is to always immediately send a standalone ack if we have no delegate, because in that situation there won't be anything app-level to piggyback on.
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The basic scenario, with all messages requesting acks, is:
When B receives the message, the exchange is still alive, waiting for
an ack. It gets the message handed to it, processes it, queues up an
ack for the message it just got. Then the stack unwinds, the
exchange's refcount drops to 0 (because it's no longer waiting for an
ack, so not referenced by the reliable message manager), and its
destructor tries to flush the pending ack, which fails assertions due
to the refcount being 0.
The fix is to always immediately send a standalone ack if we
have no delegate, because in that situation there won't be anything
app-level to piggyback on.
Problem
Crash on receiving a message. To reproduce easily:
scripts/examples/gn_build_example.sh examples/all-clusters-app/linux out/debug/standalone chip_config_network_layer_ble=false
scripts/examples/gn_build_example.sh examples/chip-tool out/debug/standalone/
./out/debug/standalone/chip-all-clusters-app
Change overview
Fix the crash by immediately flushing out the pending ack if we have no delegate (which includes when we're closed), so that we don't try to do it from our destructor.
Testing
Unit test added in the PR. Manually tested the steps above.