Zabbix

/*

** Copyright (C) 2001-2025 Zabbix SIA

**

** This program is free software: you can redistribute it and/or modify it under the terms of

** the GNU Affero General Public License as published by the Free Software Foundation, version 3.

**

** This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;

** without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

** See the GNU Affero General Public License for more details.

**

** You should have received a copy of the GNU Affero General Public License along with this program.

** If not, see <https://www.gnu.org/licenses/>.

**/

​

#include "ntp.h"

#include "../sysinfo.h"

​

#include "zbxcomms.h"

#include "zbxtime.h"

​

#define NTP_SCALE       4294967296.0    /* 2^32, of course! */

​

#define NTP_PACKET_SIZE     48      /* without authentication */

#define NTP_OFFSET_ORIGINATE    24      /* offset of originate timestamp */

#define NTP_OFFSET_TRANSMIT 40      /* offset of transmit timestamp */

​

#define NTP_VERSION     3       /* the current version */

​

#define NTP_MODE_CLIENT     3       /* NTP client request */

#define NTP_MODE_SERVER     4       /* NTP server response */

​

typedef struct

{

    unsigned char   version;

    unsigned char   mode;

    double      transmit;

}

ntp_data;

​

static void make_packet(ntp_data *data)

{

    data->version = NTP_VERSION;

    data->mode = NTP_MODE_CLIENT;

    data->transmit = zbx_current_time();

}

​

static void pack_ntp(const ntp_data *data, unsigned char *request, int length)

{

    /* Pack the essential data into an NTP packet, bypassing struct layout  */

    /* and endian problems. Note that it ignores fields irrelevant to SNTP. */

​

    memset(request, 0, length);

​

    request[0] = (data->version << 3) | data->mode;

​

    double  d = data->transmit / NTP_SCALE;

​

    for (int i = 0; i < 8; i++)

    {

        int k = (int)(d *= 256.0);

​

        if (k >= 256)

            k = 255;