PTP_CLASS_V1       39 include/linux/ptp_classify.h #define PTP_CLASS_V1_IPV4 (PTP_CLASS_V1 | PTP_CLASS_IPV4)
PTP_CLASS_V1       40 include/linux/ptp_classify.h #define PTP_CLASS_V1_IPV6 (PTP_CLASS_V1 | PTP_CLASS_IPV6) /* probably DNE */