Improve stress resistance #18
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Hydradancer sets the endpoints status to
NAKwhile sending data to Facedancer, to avoid buffering packets (which means Facedancer is in sync with the USB2 controller).I was setting the data toggles in advance (after each successful transfer), thinking the
NAKstatus on the endpoint was enough to prevent the controller from saving data.Since I was having issues with duplicated data/weird buffers (correct transfer length but wrong data, too much or too little data), I created a test
test_usb_stress_test_delayedwhich reproduces the delayed change of endpoint status toACKwith a timer and was able to reproduce the issue.Turns out, not setting the toggle in advance worked and seemingly keeps the USB2 controller from messing up its internal FIFO. Setting
NAKon the endpoint should have been enough but that's not how it works apparently.I've been able to delay each OUT transfer in the stress test by 1ms, which confirmed this works and also fixed the issue in Hydradancer.