87 lines
1.9 KiB
C
87 lines
1.9 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* The Rdate command will ask a time server for the RFC 868 time
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* and optionally set the system time.
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*
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* by Sterling Huxley <sterling@europa.com>
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*
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* Licensed under GPL v2 or later, see file License for details.
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*/
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <stdio.h>
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#include <string.h>
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#include <time.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <signal.h>
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#include "busybox.h"
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static const int RFC_868_BIAS = 2208988800UL;
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static void socket_timeout(int sig)
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{
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bb_error_msg_and_die("timeout connecting to time server");
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}
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static time_t askremotedate(const char *host)
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{
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unsigned long nett;
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struct sockaddr_in s_in;
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int fd;
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bb_lookup_host(&s_in, host);
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s_in.sin_port = bb_lookup_port("time", "tcp", 37);
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/* Add a timeout for dead or inaccessible servers */
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alarm(10);
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signal(SIGALRM, socket_timeout);
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fd = xconnect_tcp_v4(&s_in);
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if (safe_read(fd, (void *)&nett, 4) != 4) /* read time from server */
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bb_error_msg_and_die("%s did not send the complete time", host);
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close(fd);
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/* convert from network byte order to local byte order.
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* RFC 868 time is the number of seconds
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* since 00:00 (midnight) 1 January 1900 GMT
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* the RFC 868 time 2,208,988,800 corresponds to 00:00 1 Jan 1970 GMT
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* Subtract the RFC 868 time to get Linux epoch
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*/
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return(ntohl(nett) - RFC_868_BIAS);
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}
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int rdate_main(int argc, char **argv)
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{
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time_t remote_time;
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unsigned long flags;
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opt_complementary = "-1";
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flags = getopt32(argc, argv, "sp");
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remote_time = askremotedate(argv[optind]);
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if ((flags & 2) == 0) {
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time_t current_time;
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time(¤t_time);
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if (current_time == remote_time)
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bb_error_msg("current time matches remote time");
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else
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if (stime(&remote_time) < 0)
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bb_perror_msg_and_die("cannot set time of day");
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}
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if ((flags & 1) == 0)
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printf("%s", ctime(&remote_time));
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return EXIT_SUCCESS;
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}
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