RES_USEVC
_res.options |= RES_STAYOPEN | RES_USEVC;
_res.options &= ~(RES_STAYOPEN | RES_USEVC);
case RES_USEVC: return "usevc";
v_circuit = (statp->options & RES_USEVC) || buflen > PACKETSZ;
if ((v_circuit && (statp->options & RES_USEVC) == 0U) ||