110 lines
3.1 KiB
C
110 lines
3.1 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 GPLv2 or later, see file LICENSE in this source tree.
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*/
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//config:config RDATE
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//config: bool "rdate (6 kb)"
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//config: default y
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//config: help
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//config: The rdate utility allows you to synchronize the date and time of your
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//config: system clock with the date and time of a remote networked system using
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//config: the RFC868 protocol, which is built into the inetd daemon on most
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//config: systems.
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//applet:IF_RDATE(APPLET(rdate, BB_DIR_USR_SBIN, BB_SUID_DROP))
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//kbuild:lib-$(CONFIG_RDATE) += rdate.o
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//usage:#define rdate_trivial_usage
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//usage: "[-s/-p] HOST"
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//usage:#define rdate_full_usage "\n\n"
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//usage: "Set and print time from HOST using RFC 868\n"
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//usage: "\n -s Only set system time"
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//usage: "\n -p Only print time"
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#include "libbb.h"
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enum { RFC_868_BIAS = 2208988800UL };
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static void socket_timeout(int sig UNUSED_PARAM)
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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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uint32_t nett;
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int fd;
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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 = create_and_connect_stream_or_die(host, bb_lookup_port("time", "tcp", 37));
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if (safe_read(fd, &nett, 4) != 4) /* read time from server */
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bb_error_msg_and_die("%s: %s", host, "short read");
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if (ENABLE_FEATURE_CLEAN_UP)
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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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nett = ntohl(nett) - RFC_868_BIAS;
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if (sizeof(time_t) > 4) {
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/* Now we have 32-bit lsb of a wider time_t
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* Imagine that nett = 0x00000001,
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* current time cur = 0x123ffffffff.
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* Assuming our time is not some 40 years off,
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* remote time must be 0x12400000001.
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* Need to adjust out time by (int32_t)(nett - cur).
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*/
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time_t cur = time(NULL);
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int32_t adjust = (int32_t)(nett - (uint32_t)cur);
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return cur + adjust;
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}
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/* This is not going to work, but what can we do */
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return (time_t)nett;
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}
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int rdate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int rdate_main(int argc UNUSED_PARAM, char **argv)
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{
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time_t remote_time;
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unsigned flags;
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opt_complementary = "-1";
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flags = getopt32(argv, "sp");
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remote_time = askremotedate(argv[optind]);
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/* Manpages of various Unixes are confusing. What happens is:
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* (no opts) set and print time
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* -s: set time ("do not print the time")
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* -p: print time ("do not set, just print the remote time")
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* -sp: print time (that's what we do, not sure this is right)
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*/
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if (!(flags & 2)) { /* no -p (-s may be present) */
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if (time(NULL) == 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("can't set time of day");
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}
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if (flags != 1) /* not lone -s */
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printf("%s", ctime(&remote_time));
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return EXIT_SUCCESS;
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}
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