src/lib/log/ratelim.c

   1 /* Copyright (c) 2003-2004, Roger Dingledine
   2  * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   3  * Copyright (c) 2007-2021, The Tor Project, Inc. */
   4 /* See LICENSE for licensing information */
   5
   6 /**
   7  * \file ratelim.c
   8  * \brief Summarize similar messages that would otherwise flood the logs.
   9  **/
  10
  11 #include "lib/log/ratelim.h"
  12 #include "lib/malloc/malloc.h"
  13 #include "lib/string/printf.h"
  14 #include "lib/intmath/muldiv.h"
  15
  16 /** If the rate-limiter <b>lim</b> is ready at <b>now</b>, return the number
  17  * of calls to rate_limit_is_ready (including this one!) since the last time
  18  * rate_limit_is_ready returned nonzero.  Otherwise return 0.
  19  * If the call number hits <b>RATELIM_TOOMANY</b> limit, drop a warning
  20  * about this event and stop counting. */
  21 static int
  22 rate_limit_is_ready(ratelim_t *lim, time_t now)
  23 {
  24   if (lim->rate + lim->last_allowed <= now) {
  25     int res = lim->n_calls_since_last_time + 1;
  26     lim->last_allowed = now;
  27     lim->n_calls_since_last_time = 0;
  28     return res;
  29   } else {
  30     if (lim->n_calls_since_last_time <= RATELIM_TOOMANY) {
  31       ++lim->n_calls_since_last_time;
  32     }
  33
  34     return 0;
  35   }
  36 }
  37
  38 /** If the rate-limiter <b>lim</b> is ready at <b>now</b>, return a newly
  39  * allocated string indicating how many messages were suppressed, suitable to
  40  * append to a log message.  Otherwise return NULL. */
  41 char *
  42 rate_limit_log(ratelim_t *lim, time_t now)
  43 {
  44   int n;
  45   if ((n = rate_limit_is_ready(lim, now))) {
  46     time_t started_limiting = lim->started_limiting;
  47     lim->started_limiting = 0;
  48     if (n == 1) {
  49       return tor_strdup("");
  50     } else {
  51       char *cp=NULL;
  52       const char *opt_over = (n >= RATELIM_TOOMANY) ? "over " : "";
  53       unsigned difference = (unsigned)(now - started_limiting);
  54       difference = round_to_next_multiple_of(difference, 60);
  55       tor_asprintf(&cp,
  56                    " [%s%d similar message(s) suppressed in last %d seconds]",
  57                    opt_over, n-1, (int)difference);
  58       return cp;
  59     }
  60   } else {
  61     if (lim->started_limiting == 0) {
  62       lim->started_limiting = now;
  63     }
  64     return NULL;
  65   }
  66 }