Improve ratelimit message to list true interval.

Previous message would say "N messages in the last T seconds", but
would give an inaccurate number for N.

We now give an accurate number, rounded up to the nearest 60 seconds.

Closes #19431.

2 files changed, 16 insertions, 4 deletions

diff --git a/src/lib/log/ratelim.c b/src/lib/log/ratelim.c
index ac401fb398..8dfaee3384 100644
--- a/src/lib/log/ratelim.c
+++ b/src/lib/log/ratelim.c
@@ -11,6 +11,7 @@
 #include "lib/log/ratelim.h"
 #include "lib/malloc/malloc.h"
 #include "lib/string/printf.h"
+#include "lib/intmath/muldiv.h"
 
 /** If the rate-limiter <b>lim</b> is ready at <b>now</b>, return the number
  * of calls to rate_limit_is_ready (including this one!) since the last time
@@ -42,19 +43,24 @@ rate_limit_log(ratelim_t *lim, time_t now)
 {
   int n;
   if ((n = rate_limit_is_ready(lim, now))) {
+    time_t started_limiting = lim->started_limiting;
+    lim->started_limiting = 0;
     if (n == 1) {
       return tor_strdup("");
     } else {
       char *cp=NULL;
       const char *opt_over = (n >= RATELIM_TOOMANY) ? "over " : "";
-      /* XXXX this is not exactly correct: the messages could have occurred
-       * any time between the old value of lim->allowed and now. */
+      unsigned difference = (unsigned)(now - started_limiting);
+      difference = round_to_next_multiple_of(difference, 60);
       tor_asprintf(&cp,
                    " [%s%d similar message(s) suppressed in last %d seconds]",
-                   opt_over, n-1, lim->rate);
+                   opt_over, n-1, (int)difference);
       return cp;
     }
   } else {
+    if (lim->started_limiting == 0) {
+      lim->started_limiting = now;
+    }
     return NULL;
   }
 }
diff --git a/src/lib/log/ratelim.h b/src/lib/log/ratelim.h
index e9b55d40dc..9e202028cf 100644
--- a/src/lib/log/ratelim.h
+++ b/src/lib/log/ratelim.h
@@ -40,13 +40,19 @@
    </pre>
  */
 typedef struct ratelim_t {
+  /** How many seconds must elapse between log messages? */
   int rate;
+  /** When did this limiter last allow a message to appear? */
   time_t last_allowed;
+  /** When did this limiter start suppressing messages? */
+  time_t started_limiting;
+  /** How many messages has this limiter suppressed since it last allowed
+   * one to appear? */
   int n_calls_since_last_time;
 } ratelim_t;
 
 #ifndef COCCI
-#define RATELIM_INIT(r) { (r), 0, 0 }
+#define RATELIM_INIT(r) { (r), 0, 0, 0 }
 #endif
 #define RATELIM_TOOMANY (16*1000*1000)