Bug 25733: Avoid assert failure if all circuits time out.

Prior to #23100, we were not counting HS circuit build times in our
calculation of the timeout. This could lead to a condition where our timeout
was set too low, based on non HS circuit build times, and then we would
abandon all HS circuits, storing no valid timeouts in the histogram.

This commit avoids the assert.
This commit is contained in:
Mike Perry 2018-04-16 22:49:27 +00:00
parent c5899d5cf3
commit 35e7902116
2 changed files with 22 additions and 2 deletions

4
changes/bug25733 Normal file
View File

@ -0,0 +1,4 @@
o Minor bugfixes (Assert crash):
- Avoid an assert in the circuit build timeout code if we fail to
allow any circuits to actually complete. Fixes bug 25733;
bugfix on 0.2.2.2-alpha.

View File

@ -767,11 +767,23 @@ circuit_build_times_get_xm(circuit_build_times_t *cbt)
histogram[nth_max_bin[n]]); histogram[nth_max_bin[n]]);
} }
/* The following assert is safe, because we don't get called when we /* bin_counts can become zero if all of our last CBT_NCIRCUITS_TO_OBSERVE
* haven't observed at least CBT_MIN_MIN_CIRCUITS_TO_OBSERVE circuits. */ * circuits were abandoned before they completed. This shouldn't happen,
* though. We should have reset/re-learned a lower timeout first. */
if (bin_counts == 0) {
ret = 0;
log_warn(LD_CIRC,
"No valid circuit build time data out of %d times, %u modes, "
"have_timeout=%d, %lfms", cbt->total_build_times, num_modes,
cbt->have_computed_timeout, cbt->timeout_ms);
goto done;
}
tor_assert(bin_counts > 0); tor_assert(bin_counts > 0);
ret /= bin_counts; ret /= bin_counts;
done:
tor_free(histogram); tor_free(histogram);
tor_free(nth_max_bin); tor_free(nth_max_bin);
@ -1057,6 +1069,10 @@ circuit_build_times_update_alpha(circuit_build_times_t *cbt)
* and less frechet-like. */ * and less frechet-like. */
cbt->Xm = circuit_build_times_get_xm(cbt); cbt->Xm = circuit_build_times_get_xm(cbt);
/* If Xm came back 0, then too many circuits were abandoned. */
if (cbt->Xm == 0)
return 0;
tor_assert(cbt->Xm > 0); tor_assert(cbt->Xm > 0);
for (i=0; i< CBT_NCIRCUITS_TO_OBSERVE; i++) { for (i=0; i< CBT_NCIRCUITS_TO_OBSERVE; i++) {