path: root/util-linux/rdate.c (plain)
blob: 51d5eb6ae2d342d7bd96e54ac89a336f20f4b0f9

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	//config:config RDATE
11	//config: bool "rdate"
12	//config: default y
13	//config: help
14	//config: The rdate utility allows you to synchronize the date and time of your
15	//config: system clock with the date and time of a remote networked system using
16	//config: the RFC868 protocol, which is built into the inetd daemon on most
17	//config: systems.
18
19	//applet:IF_RDATE(APPLET(rdate, BB_DIR_USR_SBIN, BB_SUID_DROP))
20
21	//kbuild:lib-$(CONFIG_RDATE) += rdate.o
22
23	//usage:#define rdate_trivial_usage
24	//usage: "[-sp] HOST"
25	//usage:#define rdate_full_usage "\n\n"
26	//usage: "Get and possibly set system time from a remote HOST\n"
27	//usage: "\n -s Set system time (default)"
28	//usage: "\n -p Print time"
29
30	#include "libbb.h"
31	#include <android.h>
32
33
34	enum { RFC_868_BIAS = 2208988800UL };
35
36	static void socket_timeout(int sig UNUSED_PARAM)
37	{
38	bb_error_msg_and_die("timeout connecting to time server");
39	}
40
41	static time_t askremotedate(const char *host)
42	{
43	uint32_t nett;
44	int fd;
45
46	/* Add a timeout for dead or inaccessible servers */
47	alarm(10);
48	signal(SIGALRM, socket_timeout);
49
50	fd = create_and_connect_stream_or_die(host, bb_lookup_port("time", "tcp", 37));
51
52	if (safe_read(fd, &nett, 4) != 4) /* read time from server */
53	bb_error_msg_and_die("%s: %s", host, "short read");
54	if (ENABLE_FEATURE_CLEAN_UP)
55	close(fd);
56
57	/* Convert from network byte order to local byte order.
58	* RFC 868 time is the number of seconds
59	* since 00:00 (midnight) 1 January 1900 GMT
60	* the RFC 868 time 2,208,988,800 corresponds to 00:00 1 Jan 1970 GMT
61	* Subtract the RFC 868 time to get Linux epoch.
62	*/
63
64	return ntohl(nett) - RFC_868_BIAS;
65	}
66
67	int rdate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
68	int rdate_main(int argc UNUSED_PARAM, char **argv)
69	{
70	time_t remote_time;
71	unsigned flags;
72
73	opt_complementary = "-1";
74	flags = getopt32(argv, "sp");
75
76	remote_time = askremotedate(argv[optind]);
77
78	if (!(flags & 2)) { /* no -p (-s may be present) */
79	time_t current_time;
80
81	time(&current_time);
82	if (current_time == remote_time)
83	bb_error_msg("current time matches remote time");
84	else
85	if (stime(&remote_time) < 0)
86	bb_perror_msg_and_die("can't set time of day");
87	}
88
89	if (flags != 1) /* not lone -s */
90	printf("%s", ctime(&remote_time));
91
92	return EXIT_SUCCESS;
93	}
94