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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 | /* vi: set sw=4 ts=4: */ /* * The Rdate command will ask a time server for the RFC 868 time * and optionally set the system time. * * by Sterling Huxley <sterling@europa.com> * * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ //config:config RDATE //config: bool "rdate (5.6 kb)" //config: default y //config: help //config: The rdate utility allows you to synchronize the date and time of your //config: system clock with the date and time of a remote networked system using //config: the RFC868 protocol, which is built into the inetd daemon on most //config: systems. //applet:IF_RDATE(APPLET(rdate, BB_DIR_USR_SBIN, BB_SUID_DROP)) //kbuild:lib-$(CONFIG_RDATE) += rdate.o //usage:#define rdate_trivial_usage //usage: "[-s/-p] HOST" //usage:#define rdate_full_usage "\n\n" //usage: "Set and print time from HOST using RFC 868\n" //usage: "\n -s Only set system time" //usage: "\n -p Only print time" #include "libbb.h" enum { RFC_868_BIAS = 2208988800UL }; static void socket_timeout(int sig UNUSED_PARAM) { bb_simple_error_msg_and_die("timeout connecting to time server"); } static time_t askremotedate(const char *host) { uint32_t nett; int fd; /* Timeout for dead or inaccessible servers */ alarm(10); signal(SIGALRM, socket_timeout); fd = create_and_connect_stream_or_die(host, bb_lookup_std_port("time", "tcp", 37)); if (safe_read(fd, &nett, 4) != 4) /* read time from server */ bb_error_msg_and_die("%s: %s", host, "short read"); if (ENABLE_FEATURE_CLEAN_UP) close(fd); /* Convert from network byte order to local byte order. * RFC 868 time is seconds since 1900-01-01 00:00 GMT. * RFC 868 time 2,208,988,800 corresponds to 1970-01-01 00:00 GMT. * Subtract the RFC 868 time to get Linux epoch. */ nett = ntohl(nett) - RFC_868_BIAS; if (sizeof(time_t) > 4) { /* Now we have 32-bit lsb of a wider time_t * Imagine that nett = 0x00000001, * current time cur = 0x123ffffffff. * Assuming our time is not some 40 years off, * remote time must be 0x12400000001. * Need to adjust our time by (int32_t)(nett - cur). */ time_t cur = time(NULL); int32_t adjust = (int32_t)(nett - (uint32_t)cur); return cur + adjust; } /* This is not going to work, but what can we do */ return (time_t)nett; } int rdate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int rdate_main(int argc UNUSED_PARAM, char **argv) { time_t remote_time; unsigned flags; flags = getopt32(argv, "^" "sp" "\0" "-1"); remote_time = askremotedate(argv[optind]); /* Manpages of various Unixes are confusing. What happens is: * (no opts) set and print time * -s: set time ("do not print the time") * -p: print time ("do not set, just print the remote time") * -sp: print time (that's what we do, not sure this is right) */ if (!(flags & 2)) { /* no -p (-s may be present) */ if (time(NULL) == remote_time) bb_simple_error_msg("current time matches remote time"); else { struct timeval ts; ts.tv_sec = remote_time; ts.tv_usec = 0; xsettimeofday(&ts); } } if (flags != 1) /* not lone -s */ printf("%s", ctime(&remote_time)); return EXIT_SUCCESS; } |