release/src/router/busybox/util-linux/rdate.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * The Rdate command will ask a time server for the RFC 868 time
   4  *  and optionally set the system time.
   5  *
   6  * by Sterling Huxley <sterling@europa.com>
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   9 */
  10
  11 //usage:#define rdate_trivial_usage
  12 //usage:       "[-sp] HOST"
  13 //usage:#define rdate_full_usage "\n\n"
  14 //usage:       "Get and possibly set the system date and time from a remote HOST\n"
  15 //usage:     "\n        -s      Set the system date and time (default)"
  16 //usage:     "\n        -p      Print the date and time"
  17
  18 #include "libbb.h"
  19
  20 enum { RFC_868_BIAS = 2208988800UL };
  21
  22 static void socket_timeout(int sig UNUSED_PARAM)
  23 {
  24         bb_error_msg_and_die("timeout connecting to time server");
  25 }
  26
  27 static time_t askremotedate(const char *host)
  28 {
  29         uint32_t nett;
  30         int fd;
  31
  32         /* Add a timeout for dead or inaccessible servers */
  33         alarm(10);
  34         signal(SIGALRM, socket_timeout);
  35
  36         fd = create_and_connect_stream_or_die(host, bb_lookup_port("time", "tcp", 37));
  37
  38         if (safe_read(fd, (void *)&nett, 4) != 4)    /* read time from server */
  39                 bb_error_msg_and_die("%s did not send the complete time", host);
  40         close(fd);
  41
  42         /* convert from network byte order to local byte order.
  43          * RFC 868 time is the number of seconds
  44          * since 00:00 (midnight) 1 January 1900 GMT
  45          * the RFC 868 time 2,208,988,800 corresponds to 00:00  1 Jan 1970 GMT
  46          * Subtract the RFC 868 time to get Linux epoch
  47          */
  48
  49         return ntohl(nett) - RFC_868_BIAS;
  50 }
  51
  52 int rdate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  53 int rdate_main(int argc UNUSED_PARAM, char **argv)
  54 {
  55         time_t remote_time;
  56         unsigned long flags;
  57
  58         opt_complementary = "-1";
  59         flags = getopt32(argv, "sp");
  60
  61         remote_time = askremotedate(argv[optind]);
  62
  63         if ((flags & 2) == 0) {
  64                 time_t current_time;
  65
  66                 time(&current_time);
  67                 if (current_time == remote_time)
  68                         bb_error_msg("current time matches remote time");
  69                 else
  70                         if (stime(&remote_time) < 0)
  71                                 bb_perror_msg_and_die("can't set time of day");
  72         }
  73
  74         if ((flags & 1) == 0)
  75                 printf("%s", ctime(&remote_time));
  76
  77         return EXIT_SUCCESS;
  78 }