如何用C语言将NTP时间转换为Unix纪元时间(Linux)
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我已经尝试了几个月来创建一个基于RFC5905的简单SNTP单客户端/服务器.最后我设法让它工作至少我认为它工作正常,但当我尝试针对真正的NTP服务器测试我的代码时(例如0.se.pool.ntp.org:123)我收到的时间戳需要重新计算.我已经尝试了几种不同的方法,但无论是现在3天,但无论我什么都没试过.
有谁知道如何将NTP时间戳转换为Unix纪元时间戳？
执行服务器的语法,例如./server 127.0.0.1:5000和客户端,例如./client 127.0.0.1:5000
针对真实NTP服务器执行客户端的语法,例如./client 0.se.pool.ntp.org:123
工作代码示例客户端：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <time.h>
#include <math.h>
#include <sys/timeb.h>
#include <inttypes.h>
#include <limits.h>
#include <assert.h>
#define UNIX_EPOCH 2208988800UL /* 1970 - 1900 in seconds */
typedef struct client_packet client_packet;
struct client_packet {
uint8_t client_li_vn_mode;
uint8_t client_stratum;
uint8_t client_poll;
uint8_t client_precision;
uint32_t client_root_delay;
uint32_t client_root_dispersion;
uint32_t client_reference_identifier;
uint32_t client_reference_timestamp_sec;
uint32_t client_reference_timestamp_microsec;
uint32_t client_originate_timestamp_sec;
uint32_t client_originate_timestamp_microsec;
uint32_t client_receive_timestamp_sec;
uint32_t client_receive_timestamp_microsec;
uint32_t client_transmit_timestamp_sec;
uint32_t client_transmit_timestamp_microsec;
}__attribute__((packed));
typedef struct server_send server_send;
struct server_send {
uint8_t server_li_vn_mode;
uint8_t server_stratum;
uint8_t server_poll;
uint8_t server_precision;
uint32_t server_root_delay;
uint32_t server_root_dispersion;
char server_reference_identifier[4];
uint32_t server_reference_timestamp_sec;
uint32_t server_reference_timestamp_microsec;
uint32_t server_originate_timestamp_sec;
uint32_t server_originate_timestamp_microsec;
uint32_t server_receive_timestamp_sec;
uint32_t server_receive_timestamp_microsec;
uint32_t server_transmit_timestamp_sec;
uint32_t server_transmit_timestamp_microsec;
}__attribute__((packed));
/* Linux man page bind() */
#define handle_error(msg) \
do {perror(msg); exit(EXIT_FAILURE);} while (0)
uint32_t ClockGetTime() {
struct timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
return (uint32_t)ts.tv_sec * 1000000LL + (uint32_t)ts.tv_nsec / 1000LL;
}
int main(int argc, char *argv[]) {
int sockfd , numbytes;
struct addrinfo hints, *servinfo, *p;
int rv;
client_packet memsend;
server_send memrcv;
memset( &memsend , 0 , sizeof memsend );
memset( &memrcv , 0 , sizeof memrcv );
char IP[16]; /* IP = 15 digits 1 extra for \0 null terminating character string */
char PORT_STR[6]; /* Port = 5 digits MAX 1 extra for \0 null terminating character string */
memset(IP , '\0' , sizeof(IP));
memset(PORT_STR , '\0' , sizeof(PORT_STR));
strcpy(IP, strtok(argv[1], ":"));
strcpy(PORT_STR, strtok(NULL, ":"));
memset( &hints , 0 , sizeof hints );
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
if ( ( rv = getaddrinfo( IP , PORT_STR , &hints , &servinfo ) ) != 0 ) {
fprintf( stderr , "getaddrinfo: %s\n" , gai_strerror(rv) );
return 1;
}
// loop through all the results and make a socket
for( p = servinfo; p != NULL; p = p->ai_next ) {
if ( ( sockfd = socket( p->ai_family , p->ai_socktype , p->ai_protocol ) ) == -1 ) {
handle_error( "socket" );
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "Error while binding socket\n");
return 2;
}
memsend.client_li_vn_mode = 0b00100011;
memsend.client_stratum = 0;
memsend.client_poll = 0;
memsend.client_precision = 0;
memsend.client_root_delay = 0;
memsend.client_root_dispersion = 0;
memsend.client_reference_identifier = 0;
memsend.client_reference_timestamp_sec = 0;
memsend.client_reference_timestamp_microsec = 0;
memsend.client_receive_timestamp_sec = 0;
memsend.client_receive_timestamp_microsec = 0;
time_t time_originate_sec = time(NULL);
memsend.client_originate_timestamp_sec = time_originate_sec;
memsend.client_originate_timestamp_microsec = ClockGetTime();
memsend.client_transmit_timestamp_sec = memsend.client_originate_timestamp_sec;
memsend.client_transmit_timestamp_microsec = memsend.client_originate_timestamp_microsec;
if ( ( numbytes = sendto( sockfd, &memsend , sizeof memsend , 0 ,
p->ai_addr , p->ai_addrlen ) ) == -1 ) {
handle_error("sendto");
exit(1);
}
if ( ( numbytes = recvfrom( sockfd , &memrcv , sizeof memrcv , 0 ,
(struct sockaddr *) &p->ai_addr, &p->ai_addrlen ) ) == -1 ) {
handle_error( "recvfrom" );
exit(1);
}
time_t time_rcv_sec = time(NULL);
uint32_t client_rcv_timestamp_sec = time_rcv_sec;
uint32_t client_rcv_timestamp_microsec = ClockGetTime();
freeaddrinfo(servinfo);
char Identifier[5];
memset(Identifier , '\0' , sizeof Identifier);
memcpy(Identifier , memrcv.server_reference_identifier , sizeof memrcv.server_reference_identifier);
printf("\t Reference Identifier \t %"PRIu32" \t\t\t %s\n",memsend.client_reference_identifier,Identifier);
printf("\t Reference Timestamp \t %"PRIu32".%"PRIu32" \t\t\t %"PRIu32".%"PRIu32"\n",memsend.client_reference_timestamp_sec,memsend.client_reference_timestamp_microsec,memrcv.server_reference_timestamp_sec,memrcv.server_reference_timestamp_microsec);
printf("\t Originate Timestamp \t %"PRIu32".%"PRIu32" \t %"PRIu32".%"PRIu32"\n",memsend.client_originate_timestamp_sec,memsend.client_originate_timestamp_microsec,memrcv.server_originate_timestamp_sec,memrcv.server_originate_timestamp_microsec);
printf("\t Receive Timestamp \t %"PRIu32".%"PRIu32" \t %"PRIu32".%"PRIu32"\n",client_rcv_timestamp_sec,client_rcv_timestamp_microsec,memrcv.server_receive_timestamp_sec,memrcv.server_receive_timestamp_microsec);
printf("\t Transmit Timestamp \t %"PRIu32".%"PRIu32" \t %"PRIu32".%"PRIu32"\n\n",memsend.client_transmit_timestamp_sec,memsend.client_transmit_timestamp_microsec,memrcv.server_transmit_timestamp_sec,memrcv.server_transmit_timestamp_microsec);
close(sockfd);
return 0;
}
服务器代码示例：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <time.h>
#include <math.h>
#include <sys/timeb.h>
#include <inttypes.h>
#include <limits.h>
#define TRUE 1
typedef struct client_send client_send;
struct client_send {
uint8_t client_li_vn_mode;
uint8_t client_startum;
uint8_t client_poll;
uint8_t client_precision;
uint32_t client_root_delay;
uint32_t client_root_dispersion;
uint32_t client_reference_identifier;
uint32_t client_reference_timestamp_sec;
uint32_t client_reference_timestamp_microsec;
uint32_t client_originate_timestamp_sec;
uint32_t client_originate_timestamp_microsec;
uint32_t client_receive_timestamp_sec;
uint32_t client_receive_timestamp_microsec;
uint32_t client_transmit_timestamp_sec;
uint32_t client_transmit_timestamp_microsec;
}__attribute__((packed));
typedef struct server_packet server_packet;
struct server_packet {
uint8_t server_li_vn_mode;
uint8_t server_startum;
uint8_t server_poll;
uint8_t server_precision;
uint32_t server_root_delay;
uint32_t server_root_dispersion;
char server_reference_identifier[4];
uint32_t server_reference_timestamp_sec;
uint32_t server_reference_timestamp_microsec;
uint32_t server_originate_timestamp_sec;
uint32_t server_originate_timestamp_microsec;
uint32_t server_receive_timestamp_sec;
uint32_t server_receive_timestamp_microsec;
uint32_t server_transmit_timestamp_sec;
uint32_t server_transmit_timestamp_microsec;
}__attribute__((packed));
/* Linux man page bind() */
#define handle_error(msg) \
do {perror(msg); exit(EXIT_FAILURE);} while (0)
uint32_t ClockGetTime() {
struct timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
return (uint32_t)ts.tv_sec * 1000000LL + (uint32_t)ts.tv_nsec / 1000LL;
}
unsigned long int precision() {
struct timespec res;
if ( clock_getres( CLOCK_REALTIME, &res) == -1 ) {
perror( "clock get resolution" );
return EXIT_FAILURE;
}
return res.tv_nsec / 1000;
}
void *get_in_addr(struct sockaddr *sa) {
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(int argc, char *argv[]) {
server_packet send_mem;
client_send rcv_mem;
/* Empty structs */
memset( &send_mem , 0 , sizeof send_mem );
memset( &rcv_mem , 0 , sizeof rcv_mem );
char s[INET_ADDRSTRLEN];
struct addrinfo hints, *servinfo, *p;
struct sockaddr_storage their_addr;
socklen_t addr_len;
int get, numbytes;
int sockfd;
char IP[16];
char PORT_STR[6];
memset(IP , '\0' , sizeof(IP));
memset(PORT_STR , '\0' , sizeof(PORT_STR));
strcpy(IP, strtok(argv[1], ":"));
strcpy(PORT_STR, strtok(NULL, ":"));
memset( &hints , 0 , sizeof hints );
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
hints.ai_flags = AI_PASSIVE;
hints.ai_protocol = IPPROTO_UDP;
if ( ( get = getaddrinfo( NULL , PORT_STR , &hints , &servinfo ) ) != 0) {
fprintf( stderr , "getaddrinfo: %s\n" , gai_strerror(get) );
return 1;
}
for( p = servinfo; p != NULL; p = p->ai_next ) {
if ( ( sockfd = socket( p->ai_family , p->ai_socktype ,
p->ai_protocol ) ) == -1 ) {
handle_error("socket");
continue;
}
if ( bind( sockfd , p->ai_addr , p->ai_addrlen ) == -1 ) {
close(sockfd);
handle_error("bind");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "Not able to bind socket\n");
return 2;
}
freeaddrinfo(servinfo);
printf("\nServer is up and running: waiting to recv msg at port: %s...\n",
PORT_STR);
while(TRUE) {
time_t t_ref_sec = time(NULL);
unsigned long int Ref_epoc_sec = t_ref_sec;
send_mem.server_reference_timestamp_sec = Ref_epoc_sec;
unsigned long int t_ref_nanosec = ClockGetTime();
send_mem.server_reference_timestamp_microsec = t_ref_nanosec;
addr_len = sizeof(their_addr);
if ((numbytes = recvfrom(sockfd, &rcv_mem , sizeof rcv_mem , 0,
(struct sockaddr *)&their_addr, &addr_len)) == -1) {
handle_error("recvfrom");
exit(1);
}
time_t t_rcv_sec = time(NULL);
send_mem.server_receive_timestamp_sec = t_rcv_sec;
send_mem.server_receive_timestamp_microsec = ClockGetTime();
printf("Peer address: %s\n",
inet_ntop(their_addr.ss_family,
get_in_addr((struct sockaddr *)&their_addr),
s, sizeof(s)));
printf("Peer port: %i\n",p->ai_socktype);
send_mem.server_li_vn_mode = 0b00100100;
send_mem.server_startum = 0b00000001;
send_mem.server_poll = 0b00000110;
send_mem.server_precision = precision();
send_mem.server_root_delay = 0;
send_mem.server_root_dispersion = 0;
memcpy( send_mem.server_reference_identifier , "LOCL" ,
sizeof send_mem.server_reference_identifier );
send_mem.server_originate_timestamp_sec = rcv_mem.client_originate_timestamp_sec;
send_mem.server_originate_timestamp_microsec = rcv_mem.client_originate_timestamp_microsec;
time_t t_send_sec = time(NULL);
send_mem.server_transmit_timestamp_sec = t_send_sec;
send_mem.server_transmit_timestamp_microsec = ClockGetTime();
if ( sendto( sockfd, &send_mem , sizeof send_mem , 0 ,
(struct sockaddr *) &their_addr , addr_len ) == -1 ) {
handle_error("sendto");
exit(1);
}
}
close(sockfd);
return 0;
}
使用服务器和客户端时打印输出的样本.
Reference Identifier 0 LOCL
Reference Timestamp 0.0 1426637081.3564398733
Originate Timestamp 1426637087.3570333925 1426637087.3570333925
Receive Timestamp 1426637087.3570334078 1426637087.3570334003
Transmit Timestamp 1426637087.3570333925 1426637087.3570334046
我在探测真正的NTP服务器时打印输出的样本(例如0.se.pool.ntp.org:123).
Reference Identifier 0 ?$?
Reference Timestamp 0.0 3879449560.3503094062
Originate Timestamp 1426637090.3573978972 1426637090.3573978972
Receive Timestamp 1426637090.3573992772 2722083800.781009125
Transmit Timestamp 1426637090.3573978972 2722083800.937312997
预期的输出将类似于我之前发布的打印输出.
提前感谢大家花时间和精力帮助我.
更新相关问题但不接近我正在寻找的答案How to write a NTP client? [closed].
解决方法:
将NTP时间戳转换为Unix时间戳(struct timeval)涉及两个需要解决的问题.
一个是两个时代之间的偏移. Unix使用位于1/1 / 1970-00：00h(UTC)的时期,NTP使用1/1 / 1900-00：00h.这导致相当于70年的偏移(以秒为单位)(两个日期之间有17个闰年,因此偏移量为
(70*365 + 17)*86400 = 2208988800
从NTP时间减去以获得Unix struct timeval.
第二个是struct timeval使用1/1000000秒作为亚秒分数的单位,NTP使用1/2 ^ 32秒作为分数时间的单位.要从NTP转换为struct timeval,可以将小数部分除以2 ^ 32(这很容易,它是右移)然后乘以1000000.为了解决这个问题,我们必须使用64位算术,因为数字介于两者之间0和2 ^ 32所以,最好的是：
>从NTP转换为struct timeval将小数部分字段(NTP时间戳的右32位)复制到uint64_t变量并将其乘以1000000,然后将其右移32位以获得正确的值.您必须考虑到NTP时间戳是按网络字节顺序排列的,因此您可能需要进行一些调整才能使用这些数字进行操作.
>要从struct timeval转换,将unix时间的tv_usec字段复制到uint64_t,然后将其移位32位,然后将其除以1000000并转换为网络字节顺序(最有意义的字节优先)
以下代码示例说明了这一点.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <stdint.h>
#include <getopt.h>
#define OFFSET 2208988800ULL
void ntp2tv(uint8_t ntp[8], struct timeval *tv)
{
uint64_t aux = 0;
uint8_t *p = ntp;
int i;
/* we get the ntp in network byte order, so we must
* convert it to host byte order. */
for (i = 0; i < sizeof ntp / 2; i++) {
aux <<= 8;
aux |= *p++;
} /* for */
/* now we have in aux the NTP seconds offset */
aux -= OFFSET;
tv->tv_sec = aux;
/* let's go with the fraction of second */
aux = 0;
for (; i < sizeof ntp; i++) {
aux <<= 8;
aux |= *p++;
} /* for */
/* now we have in aux the NTP fraction (0..2^32-1) */
aux *= 1000000; /* multiply by 1e6 */
aux >>= 32; /* and divide by 2^32 */
tv->tv_usec = aux;
} /* ntp2tv */
void tv2ntp(struct timeval *tv, uint8_t ntp[8])
{
uint64_t aux = 0;
uint8_t *p = ntp + sizeof ntp;
int i;
aux = tv->tv_usec;
aux <<= 32;
aux /= 1000000;
/* we set the ntp in network byte order */
for (i = 0; i < sizeof ntp/2; i++) {
*--p = aux & 0xff;
aux >>= 8;
} /* for */
aux = tv->tv_sec;
aux += OFFSET;
/* let's go with the fraction of second */
for (; i < sizeof ntp; i++) {
*--p = aux & 0xff;
aux >>= 8;
} /* for */
} /* ntp2tv */
size_t print_tv(struct timeval *t)
{
return printf("%ld.%06ld\n", t->tv_sec, t->tv_usec);
}
size_t print_ntp(uint8_t ntp[8])
{
int i;
int res = 0;
for (i = 0; i < sizeof ntp; i++) {
if (i == sizeof ntp / 2)
res += printf(".");
res += printf("%02x", ntp[i]);
} /* for */
res += printf("\n");
return res;
} /* print_ntp */
int main(int argc, char *argv[])
{
struct timeval t;
uint8_t ntp[8];
gettimeofday(&t, NULL);
printf("tv2ntp\n");
tv2ntp(&t, ntp);
printf("tv : "); print_tv(&t);
printf("ntp: "); print_ntp(ntp);
printf("ntp2tv\n");
ntp2tv(ntp, &t);
printf("tv : "); print_tv(&t);
printf("ntp: "); print_ntp(ntp);
}
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