File: ntp.h

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/*
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
 * Copyright (C) Richard P. Curnow  1997-2003
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 * 
 * 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
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 * 
 **********************************************************************

  =======================================================================

  Header file containing common NTP bits and pieces
  */

#ifndef GOT_NTP_H
#define GOT_NTP_H

#include "sysincl.h"

#include "hash.h"

typedef struct {
  uint32_t hi;
  uint32_t lo;
} NTP_int64;

typedef uint32_t NTP_int32;

/* The NTP protocol version that we support */
#define NTP_VERSION 4

/* Maximum stratum number (infinity) */
#define NTP_MAX_STRATUM 16

/* The minimum valid length of an extension field */
#define NTP_MIN_EXTENSION_LENGTH 16

/* The maximum assumed length of all extension fields in received
   packets (RFC 5905 doesn't specify a limit on length or number of
   extension fields in one packet) */
#define NTP_MAX_EXTENSIONS_LENGTH 1024

/* The minimum and maximum supported length of MAC */
#define NTP_MIN_MAC_LENGTH (4 + 16)
#define NTP_MAX_MAC_LENGTH (4 + MAX_HASH_LENGTH)

/* The maximum length of MAC in NTPv4 packets which allows deterministic
   parsing of extension fields (RFC 7822) */
#define NTP_MAX_V4_MAC_LENGTH (4 + 20)

/* Type definition for leap bits */
typedef enum {
  LEAP_Normal = 0,
  LEAP_InsertSecond = 1,
  LEAP_DeleteSecond = 2,
  LEAP_Unsynchronised = 3
} NTP_Leap;

typedef enum {
  MODE_UNDEFINED = 0,
  MODE_ACTIVE = 1,
  MODE_PASSIVE = 2,
  MODE_CLIENT = 3,
  MODE_SERVER = 4,
  MODE_BROADCAST = 5
} NTP_Mode;

typedef struct {
  uint8_t lvm;
  uint8_t stratum;
  int8_t poll;
  int8_t precision;
  NTP_int32 root_delay;
  NTP_int32 root_dispersion;
  NTP_int32 reference_id;
  NTP_int64 reference_ts;
  NTP_int64 originate_ts;
  NTP_int64 receive_ts;
  NTP_int64 transmit_ts;

  /* Optional extension fields, we don't send packets with them yet */
  /* uint8_t extensions[] */

  /* Optional message authentication code (MAC) */
  NTP_int32 auth_keyid;
  uint8_t auth_data[NTP_MAX_MAC_LENGTH - 4];
} NTP_Packet;

#define NTP_NORMAL_PACKET_LENGTH (int)offsetof(NTP_Packet, auth_keyid)

/* The buffer used to hold a datagram read from the network */
typedef struct {
  NTP_Packet ntp_pkt;
  uint8_t extensions[NTP_MAX_EXTENSIONS_LENGTH];
} NTP_Receive_Buffer;

/* Macros to work with the lvm field */
#define NTP_LVM_TO_LEAP(lvm) (((lvm) >> 6) & 0x3)
#define NTP_LVM_TO_VERSION(lvm) (((lvm) >> 3) & 0x7)
#define NTP_LVM_TO_MODE(lvm) ((lvm) & 0x7)
#define NTP_LVM(leap, version, mode) \
  ((((leap) << 6) & 0xc0) | (((version) << 3) & 0x38) | ((mode) & 0x07))

/* Special NTP reference IDs */
#define NTP_REFID_UNSYNC 0x0UL
#define NTP_REFID_LOCAL 0x7F7F0101UL /* 127.127.1.1 */
#define NTP_REFID_SMOOTH 0x7F7F01FFUL /* 127.127.1.255 */

#endif /* GOT_NTP_H */