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@@ -1386,51 +1386,132 @@ tor_escape_str_for_pt_args(const char *string, const char *chars_to_escape)
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* Time
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* ===== */
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+#define TOR_USEC_PER_SEC 1000000
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+
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+/** Return the difference between start->tv_sec and end->tv_sec.
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+ * Returns INT64_MAX on overflow and underflow.
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+ */
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+static int64_t
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+tv_secdiff_impl(const struct timeval *start, const struct timeval *end)
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+{
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+ const int64_t s = (int64_t)start->tv_sec;
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+ const int64_t e = (int64_t)end->tv_sec;
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+
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+ /* This may not be the most efficient way of implemeting this check,
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+ * but it's easy to see that it's correct and doesn't overflow */
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+
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+ if (s > 0 && e < INT64_MIN + s) {
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+ /* s is positive: equivalent to e - s < INT64_MIN, but without any
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+ * overflow */
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+ return INT64_MAX;
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+ } else if (s < 0 && e > INT64_MAX + s) {
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+ /* s is negative: equivalent to e - s > INT64_MAX, but without any
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+ * overflow */
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+ return INT64_MAX;
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+ }
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+
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+ return e - s;
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+}
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+
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/** Return the number of microseconds elapsed between *start and *end.
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+ * Returns LONG_MAX on overflow and underflow.
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*/
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long
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tv_udiff(const struct timeval *start, const struct timeval *end)
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{
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- long udiff;
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- long secdiff = end->tv_sec - start->tv_sec;
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+ /* Sanity check tv_usec */
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+ if (start->tv_usec > TOR_USEC_PER_SEC || start->tv_usec < 0) {
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+ log_warn(LD_GENERAL, "comparing times on microsecond detail with bad "
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+ "start tv_usec: " I64_FORMAT " microseconds",
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+ I64_PRINTF_ARG(start->tv_usec));
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+ return LONG_MAX;
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+ }
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- /* end->tv_usec - start->tv_usec can be up to 1 second */
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- if (labs(secdiff)+1 > LONG_MAX/1000000) {
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+ if (end->tv_usec > TOR_USEC_PER_SEC || end->tv_usec < 0) {
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+ log_warn(LD_GENERAL, "comparing times on microsecond detail with bad "
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+ "end tv_usec: " I64_FORMAT " microseconds",
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+ I64_PRINTF_ARG(end->tv_usec));
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+ return LONG_MAX;
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+ }
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+
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+ /* Some BSDs have struct timeval.tv_sec 64-bit, but time_t (and long) 32-bit
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+ */
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+ int64_t udiff;
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+ const int64_t secdiff = tv_secdiff_impl(start, end);
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+
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+ /* end->tv_usec - start->tv_usec can be up to 1 second either way */
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+ if (secdiff > (int64_t)(LONG_MAX/1000000 - 1) ||
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+ secdiff < (int64_t)(LONG_MIN/1000000 + 1)) {
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log_warn(LD_GENERAL, "comparing times on microsecond detail too far "
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- "apart: %ld seconds", secdiff);
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+ "apart: " I64_FORMAT " seconds", I64_PRINTF_ARG(secdiff));
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return LONG_MAX;
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}
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- udiff = secdiff*1000000L + (end->tv_usec - start->tv_usec);
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- return udiff;
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+ /* we'll never get an overflow here, because we check that both usecs are
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+ * between 0 and TV_USEC_PER_SEC. */
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+ udiff = secdiff*1000000 + ((int64_t)end->tv_usec - (int64_t)start->tv_usec);
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+
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+ if (udiff > (int64_t)LONG_MAX || udiff < (int64_t)LONG_MIN) {
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+ return LONG_MAX;
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+ } else {
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+ return (long)udiff;
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+ }
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}
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/** Return the number of milliseconds elapsed between *start and *end.
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+ * If the tv_usec difference is 500, rounds away from zero.
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+ * Returns LONG_MAX on overflow and underflow.
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*/
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long
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tv_mdiff(const struct timeval *start, const struct timeval *end)
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{
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- long mdiff;
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- long secdiff = end->tv_sec - start->tv_sec;
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+ /* Sanity check tv_usec */
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+ if (start->tv_usec > TOR_USEC_PER_SEC || start->tv_usec < 0) {
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+ log_warn(LD_GENERAL, "comparing times on millisecond detail with bad "
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+ "start tv_usec: " I64_FORMAT " microseconds",
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+ I64_PRINTF_ARG(start->tv_usec));
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+ return LONG_MAX;
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+ }
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+
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+ if (end->tv_usec > TOR_USEC_PER_SEC || end->tv_usec < 0) {
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+ log_warn(LD_GENERAL, "comparing times on millisecond detail with bad "
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+ "end tv_usec: " I64_FORMAT " microseconds",
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+ I64_PRINTF_ARG(end->tv_usec));
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+ return LONG_MAX;
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+ }
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- /* end->tv_usec - start->tv_usec can be up to 1 second,
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- * but the mdiff calculation adds another temporary second */
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- if (labs(secdiff)+2 > LONG_MAX/1000) {
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+ /* Some BSDs have struct timeval.tv_sec 64-bit, but time_t (and long) 32-bit
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+ */
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+ int64_t mdiff;
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+ const int64_t secdiff = tv_secdiff_impl(start, end);
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+
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+ /* end->tv_usec - start->tv_usec can be up to 1 second either way, but the
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+ * mdiff calculation may add another temporary second for rounding.
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+ * Whether this actually causes overflow depends on the compiler's constant
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+ * folding and order of operations. */
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+ if (secdiff > (int64_t)(LONG_MAX/1000 - 2) ||
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+ secdiff < (int64_t)(LONG_MIN/1000 + 1)) {
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log_warn(LD_GENERAL, "comparing times on millisecond detail too far "
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- "apart: %ld seconds", secdiff);
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+ "apart: " I64_FORMAT " seconds", I64_PRINTF_ARG(secdiff));
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return LONG_MAX;
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}
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/* Subtract and round */
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- mdiff = secdiff*1000L +
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+ mdiff = secdiff*1000 +
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/* We add a million usec here to ensure that the result is positive,
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* so that the round-towards-zero behavior of the division will give
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* the right result for rounding to the nearest msec. Later we subtract
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* 1000 in order to get the correct result.
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- */
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- ((long)end->tv_usec - (long)start->tv_usec + 500L + 1000000L) / 1000L
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+ * We'll never get an overflow here, because we check that both usecs are
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+ * between 0 and TV_USEC_PER_SEC. */
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+ ((int64_t)end->tv_usec - (int64_t)start->tv_usec + 500 + 1000000) / 1000
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- 1000;
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- return mdiff;
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+
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+ if (mdiff > (int64_t)LONG_MAX || mdiff < (int64_t)LONG_MIN) {
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+ return LONG_MAX;
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+ } else {
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+ return (long)mdiff;
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+ }
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}
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/**
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