PRCF_RED
$$ = PRCF_RED;
$$ = PRCF_RED|PRCF_ECN;
if (opts->flags & PRCF_RED)
if (flags & PRCF_RED) {
if (flags & (PRCF_RED|PRCF_RIO)) {
if (flags & PRCF_RED) {
flags |= PRCF_RED;
if ((flags & PRCF_ECN) && (flags & (PRCF_RED|PRCF_RIO)) == 0)
flags |= PRCF_RED;