A socket EVFILT_READ knote whose NOTE_LOWAT mark is below 1 is now always ready and reports the bytes in the receive buffer, 0 when it is empty, because FreeBSD 11.4 filt_soread returns kn_data >= kn_sdata and the bytes available are never negative. This holds for level-triggered and EV_CLEAR knotes and when EV_ADD changes the mark of an existing knote. A listening socket ignores the mark, as filt_solisten does. An EVFILT_WRITE mark below 1 still throws.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
