SC_KEEPALIVE
if (sc->sc_flags & SC_KEEPALIVE) {
sc->sc_flags |= SC_KEEPALIVE;
sc->sc_flags &= ~SC_KEEPALIVE;
sc->sc_flags |= SC_KEEPALIVE;
if ((sc->sc_flags & SC_KEEPALIVE) != 0) {
sc->sc_flags &= ~SC_KEEPALIVE;
sc->sc_flags &= ~SC_KEEPALIVE;