src/timesync/timesyncd-ntp-message.h

/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once

#include "sparse-endian.h"

/* NTP protocol, packet header */
#define NTP_LEAP_PLUSSEC                1
#define NTP_LEAP_MINUSSEC               2
#define NTP_LEAP_NOTINSYNC              3
#define NTP_MODE_CLIENT                 3
#define NTP_MODE_SERVER                 4
#define NTP_FIELD_LEAP(f)               (((f) >> 6) & 3)
#define NTP_FIELD_VERSION(f)            (((f) >> 3) & 7)
#define NTP_FIELD_MODE(f)               ((f) & 7)
#define NTP_FIELD(l, v, m)              (((l) << 6) | ((v) << 3) | (m))

/*
 * "NTP timestamps are represented as a 64-bit unsigned fixed-point number,
 * in seconds relative to 0h on 1 January 1900."
 */
#define OFFSET_1900_1970        UINT64_C(2208988800)

struct ntp_ts {
        be32_t sec;
        be32_t frac;
} _packed_;

struct ntp_ts_short {
        be16_t sec;
        be16_t frac;
} _packed_;

struct ntp_msg {
        uint8_t field;
        uint8_t stratum;
        int8_t poll;
        int8_t precision;
        struct ntp_ts_short root_delay;
        struct ntp_ts_short root_dispersion;
        char refid[4];
        struct ntp_ts reference_time;
        struct ntp_ts origin_time;
        struct ntp_ts recv_time;
        struct ntp_ts trans_time;
} _packed_;