BBR_HAS_SYN
if (rsm->r_flags & BBR_HAS_SYN) {
rsm->r_flags &= ~BBR_HAS_SYN;
nrsm->r_flags &= ~BBR_HAS_SYN;
rsm->r_flags |= BBR_HAS_SYN;
if (rsm && (rsm->r_flags & BBR_HAS_SYN)) {
rsm->r_flags &= ~BBR_HAS_SYN;