IPV6_RTHDR_STRICT
if (flags != IPV6_RTHDR_LOOSE && flags != IPV6_RTHDR_STRICT)
if (flags == IPV6_RTHDR_STRICT) {
if (flags != IPV6_RTHDR_LOOSE && flags != IPV6_RTHDR_STRICT)
if (flags == IPV6_RTHDR_STRICT) {
return IPV6_RTHDR_STRICT;