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 GPL v2 or later, see file License for details.
   9 */
  10
  11 #include "libbb.h"
  12
  13 enum { RFC_868_BIAS = 2208988800UL };
  14
  15 static void socket_timeout(int sig UNUSED_PARAM)
  16 {
  17         bb_error_msg_and_die("timeout connecting to time server");
  18 }
  19
  20 static time_t askremotedate(const char *host)
  21 {
  22         uint32_t nett;
  23         int fd;
  24
  25         /* Add a timeout for dead or inaccessible servers */
  26         alarm(10);
  27         signal(SIGALRM, socket_timeout);
  28
  29         fd = create_and_connect_stream_or_die(host, bb_lookup_port("time", "tcp", 37));
  30
  31         if (safe_read(fd, (void *)&nett, 4) != 4)    /* read time from server */
  32                 bb_error_msg_and_die("%s did not send the complete time", host);
  33         close(fd);
  34
  35         /* convert from network byte order to local byte order.
  36          * RFC 868 time is the number of seconds
  37          * since 00:00 (midnight) 1 January 1900 GMT
  38          * the RFC 868 time 2,208,988,800 corresponds to 00:00  1 Jan 1970 GMT
  39          * Subtract the RFC 868 time to get Linux epoch
  40          */
  41
  42         return ntohl(nett) - RFC_868_BIAS;
  43 }
  44
  45 int rdate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  46 int rdate_main(int argc UNUSED_PARAM, char **argv)
  47 {
  48         time_t remote_time;
  49         unsigned long flags;
  50
  51         opt_complementary = "-1";
  52         flags = getopt32(argv, "sp");
  53
  54         remote_time = askremotedate(argv[optind]);
  55
  56         if ((flags & 2) == 0) {
  57                 time_t current_time;
  58
  59                 time(&current_time);
  60                 if (current_time == remote_time)
  61                         bb_error_msg("current time matches remote time");
  62                 else
  63                         if (stime(&remote_time) < 0)
  64                                 bb_perror_msg_and_die("cannot set time of day");
  65         }
  66
  67         if ((flags & 1) == 0)
  68                 printf("%s", ctime(&remote_time));
  69
  70         return EXIT_SUCCESS;
  71 }