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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:18:56 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:18:56 +0000 |
commit | b7c15c31519dc44c1f691e0466badd556ffe9423 (patch) | |
tree | f944572f288bab482a615e09af627d9a2b6727d8 /src/util/sane_time.c | |
parent | Initial commit. (diff) | |
download | postfix-b7c15c31519dc44c1f691e0466badd556ffe9423.tar.xz postfix-b7c15c31519dc44c1f691e0466badd556ffe9423.zip |
Adding upstream version 3.7.10.upstream/3.7.10
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/util/sane_time.c')
-rw-r--r-- | src/util/sane_time.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/src/util/sane_time.c b/src/util/sane_time.c new file mode 100644 index 0000000..cc86de2 --- /dev/null +++ b/src/util/sane_time.c @@ -0,0 +1,127 @@ +/*++ +/* NAME +/* sane_time 3 +/* SUMMARY +/* time(2) with backward time jump protection. +/* SYNOPSIS +/* #include <sane_time.h> +/* +/* time_t sane_time(void) +/* +/* DESCRIPTION +/* This module provides time(2) like call for applications +/* which need monotonically increasing time function rather +/* than the real exact time. It eliminates the need for various +/* workarounds all over the application which would handle +/* potential problems if time suddenly jumps backward. +/* Instead we choose to deal with this problem inside this +/* module and let the application focus on its own tasks. +/* +/* sane_time() returns the current timestamp as obtained from +/* time(2) call, at least most of the time. In case this routine +/* detects that time has jumped backward, it keeps returning +/* whatever timestamp it returned before, until this timestamp +/* and the time(2) timestamp become synchronized again. +/* Additionally, the returned timestamp is slowly increased to +/* prevent the faked clock from freezing for too long. +/* SEE ALSO +/* time(2) get current time +/* DIAGNOSTICS +/* Warning message is logged if backward time jump is detected. +/* LICENSE +/* .ad +/* .fi +/* The Secure Mailer license must be distributed with this software. +/* AUTHOR(S) +/* Patrik Rak +/* Modra 6 +/* 155 00, Prague, Czech Republic +/*--*/ + +/* System library. */ + +#include <sys_defs.h> + +/* Utility library. */ + +#include <msg.h> + +/* Application-specific. */ + +#include "sane_time.h" + +/* + * How many times shall we slow down the real clock when recovering from + * time jump. + */ +#define SLEW_FACTOR 2 + +/* sane_time - get current time, protected against time warping */ + +time_t sane_time(void) +{ + time_t now; + static time_t last_time, last_real; + long delta; + static int fraction; + static int warned; + + now = time((time_t *) 0); + + if ((delta = now - last_time) < 0 && last_time != 0) { + if ((delta = now - last_real) < 0) { + msg_warn("%sbackward time jump detected -- slewing clock", + warned++ ? "another " : ""); + } else { + delta += fraction; + last_time += delta / SLEW_FACTOR; + fraction = delta % SLEW_FACTOR; + } + } else { + if (warned) { + warned = 0; + msg_warn("backward time jump recovered -- back to normality"); + fraction = 0; + } + last_time = now; + } + last_real = now; + + return (last_time); +} + +#ifdef TEST + + /* + * Proof-of-concept test program. Repeatedly print current system time and + * time returned by sane_time(). Meanwhile, try stepping your system clock + * back and forth to see what happens. + */ + +#include <stdlib.h> +#include <msg_vstream.h> +#include <iostuff.h> /* doze() */ + +int main(int argc, char **argv) +{ + int delay = 1000000; + time_t now; + + msg_vstream_init(argv[0], VSTREAM_ERR); + + if (argc == 2 && (delay = atol(argv[1]) * 1000) > 0) + /* void */ ; + else if (argc != 1) + msg_fatal("usage: %s [delay in ms (default 1 second)]", argv[0]); + + for (;;) { + now = time((time_t *) 0); + vstream_printf("real: %s", ctime(&now)); + now = sane_time(); + vstream_printf("fake: %s\n", ctime(&now)); + vstream_fflush(VSTREAM_OUT); + doze(delay); + } +} + +#endif |