sntp.h

网络时间同步协议的实现

#include <stdio.h>
#include <sys/types.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <wait.h>
#include <signal.h>
#include <pthread.h>
#include <time.h>
#include <arpa/inet.h>
#define TIME_PORT  123
#define MAXLINE    255
#define MAX_SNTP_SERVER  3

typedef struct
{
  unsigned int Seconds;		/* Since 00:00:00 Jan 01 1900 */
  unsigned int Fraction;
} NTP_TIMESTAMP;

typedef struct
{
  char Control;
  char Stratum;
  char Poll;
  char Precision;

  unsigned int RootDelay;
  unsigned int RootDispersion;
  unsigned int ReferenceIdentifier;

  NTP_TIMESTAMP ReferenceTimestamp;
  NTP_TIMESTAMP OriginateTimestamp;
  NTP_TIMESTAMP ReceiveTimestamp;
  NTP_TIMESTAMP TransmitTimestamp;

  unsigned int KeyIdentifier;	/* Optional */
  char MessageDigest[16];	/* Optional */
} NTP_PACKET;

#define NTP_PACKET_MINLEN       48	/* Packet size - optional fields */

#define NTP_LI_NOLEAP           0x00
#define NTP_LI_61SECS           0x40
#define NTP_LI_59SECS           0x80
#define NTP_LI_ALARM            0xC0

#define NTP_VERSION_GET(pkt)    ((((pkt)->Control)>>3)&0x7)
#define NTP_VERSION_SET(ver)    (((ver)&0x7)<<3)

#define NTP_MODE_RESERVED       0
#define NTP_MODE_SYMACTIVE      1	/* Symmetric Active */
#define NTP_MODE_SYMPASSIVE     2	/* Symmetric Passive */
#define NTP_MODE_CLIENT         3
#define NTP_MODE_SERVER         4
#define NTP_MODE_BROADCAST      5
#define NTP_MODE_NTPCTRL        6	/* Reserved for NTP control message */
#define NTP_MODE_PRIVATE        7	/* Reserved for private use */
#define NTP_MODE_GET(pkt)       (((pkt)->Control)&0x7)
#define NTP_MODE_SET(mode)      ((mode)&0x7)


#define TIME_BASEDIFF           ((((unsigned int)70*365 + 17) * 24*3600))
#define TIME_NTP_TO_LOCAL(t)	((t)-TIME_BASEDIFF)
#define TIME_LOCAL_TO_NTP(t)	((t)+TIME_BASEDIFF)

struct sntp_srv_s
{
  struct sockaddr_in addr;
  int stratum;
  int version;
  unsigned int timestamp;
};

#define SNTP_WAITPERIOD        10 	/* Wait period in seconds */
#define SNTP_UPDATEPERIOD      (30*60)	/* Update period in seconds */