As of #1613, we can randomly skip packet numbers, especially early in a connection. This causes a few extra ACKs to be sent at unpredictable times. This causes tests which count the number of ACKs sent in an interval to fail. We should modify such tests to use a reordering threshold greater than 1 to prevent these extra ACKs from being sent, or perhaps expose the number of skipped packets to allow them to account for the induced ACKs.
PendingAcks::reordering_thresholddefaults to 1. This causes an ACK to be sent immediately when a packet number is skipped:https://github.com/quinn-rs/quinn/blob/8076ffe94d38813ce0220af9d3438e7bfb5e8429/quinn-proto/src/connection/spaces.rs#L607-L609
As of #1613, we can randomly skip packet numbers, especially early in a connection. This causes a few extra ACKs to be sent at unpredictable times. This causes tests which count the number of ACKs sent in an interval to fail. We should modify such tests to use a reordering threshold greater than 1 to prevent these extra ACKs from being sent, or perhaps expose the number of skipped packets to allow them to account for the induced ACKs.