// SetLinkFeaturesPostUp configures link features on t based on select TS_TUN_
// environment variables and OS feature tests. Callers should ensure t is
// up prior to calling, otherwise OS feature tests may be inconclusive.
func (t *Wrapper) SetLinkFeaturesPostUp() {
    if t.isTAP || runtime.GOOS == "android" {
        return
    }
    if groDev, ok := t.tdev.(tun.GRODevice); ok {
        if envknob.Bool("TS_TUN_DISABLE_UDP_GRO") {
            groDev.DisableUDPGRO()
        }
        if envknob.Bool("TS_TUN_DISABLE_TCP_GRO") {
            groDev.DisableTCPGRO()
        }
        err := probeTCPGRO(groDev)
        if errors.Is(err, unix.EINVAL) {
            groDev.DisableTCPGRO()
            groDev.DisableUDPGRO()
            t.logf("disabled TUN TCP & UDP GRO due to GRO probe error: %v", err)
        }
    }
}