Don't send piggybacked acks when they are not needed. #7958
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We used to set a persistent flag on reliable message contexts that would cause them to send piggyback acks with all responses after that point. Stop doing that. Also simplify the handling of the IsAckPending state. It gets set to true when we set a pending ack id, gets set to false when someone takes that ack id from us (e.g. to send the ack). This ensures that SendStandaloneAckMessage() clears the IsAckPending() state (which it already did, but that was not very obvious). Fixes project-chip#7339
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With project-chip#7958 merged, this should not be a problem.
bzbarsky-apple
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Jun 29, 2021
With project-chip#7958 merged, this should not be a problem.
bzbarsky-apple
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Jun 29, 2021
With project-chip#7958 merged, this should not be a problem. Prospectively re-enabling for WriteClient too, though that code is not used yet.
bzbarsky-apple
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With project-chip#7958 merged, this should not be a problem. Prospectively re-enabling for WriteClient too, though that code is not used yet.
woody-apple
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With #7958 merged, this should not be a problem. Prospectively re-enabling for WriteClient too, though that code is not used yet.
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Sep 23, 2021
) We used to set a persistent flag on reliable message contexts that would cause them to send piggyback acks with all responses after that point. Stop doing that. Also simplify the handling of the IsAckPending state. It gets set to true when we set a pending ack id, gets set to false when someone takes that ack id from us (e.g. to send the ack). This ensures that SendStandaloneAckMessage() clears the IsAckPending() state (which it already did, but that was not very obvious). Fixes project-chip#7339
nikita-s-wrk
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Sep 23, 2021
With project-chip#7958 merged, this should not be a problem. Prospectively re-enabling for WriteClient too, though that code is not used yet.
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We used to set a persistent flag on reliable message contexts that
would cause them to send piggyback acks with all responses after that
point. Stop doing that.
Also simplify the handling of the IsAckPending state. It gets set to
true when we set a pending ack id, gets set to false when someone
takes that ack id from us (e.g. to send the ack). This ensures that
SendStandaloneAckMessage() clears the IsAckPending() state (which it
already did, but that was not very obvious).
Fixes #7339
Problem
We are sending acks when we don't need to (and arguably should not), and causing duplicate acks to appear on the other side, which can cause problems.
Change overview
Ensure that we only send an ack when we actually have an ack pending.
Testing
New unit tests were added to cover the failure modes I was aware of that were caused by this problem. Existing unit tests were run and pass.