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Scale CONSENSUS_MIN_SECONDS_BEFORE_CACHING by voting interval

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If the voting interval was short enough, the two-minutes delay
of CONSENSUS_MIN_SECONDS_BEFORE_CACHING would confuse bridges
to the point where they would assert before downloading a consensus.
It it was even shorter (<4 minutes, I think), caches would
assert too.  This patch fixes that by having replacing the
two-minutes value with MIN(2 minutes, interval/16).

Bugfix for 1141; the cache bug could occur since 0.2.0.8-alpha, so
I'm calling this a bugfix on that.  Robert Hogan diagnosed this.
Done as a patch against maint-0.2.1, since it makes it hard to
run some kinds of testing networks.
This commit is contained in:
Nick Mathewson 2010-07-31 13:48:41 -04:00
parent b958eae573
commit 6f58481335
2 changed files with 18 additions and 4 deletions
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5
changes/bug1141 Normal file
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@ -0,0 +1,5 @@
o Minor bugfixes:
- Fix an assertion failure that could occur in caches or bridge users
when using a very short voting interval on a testing network.
Diagnosed by Robert Hogan. Fixes bug 1141; bugfix on 0.2.0.8-alpha.

17
src/or/networkstatus.c
View File

@ -1132,11 +1132,21 @@ update_consensus_networkstatus_fetch_time(time_t now)
if (c) {
long dl_interval;
long interval = c->fresh_until - c->valid_after;
long min_sec_before_caching = CONSENSUS_MIN_SECONDS_BEFORE_CACHING;
time_t start;
if (min_sec_before_caching > interval/16) {
/* Usually we allow 2-minutes slop factor in case clocks get
desynchronized a little. If we're on a private network with
a crazy-fast voting interval, though, 2 minutes may be too
much. */
min_sec_before_caching = interval/16;
}
if (directory_fetches_dir_info_early(options)) {
/* We want to cache the next one at some point after this one
* is no longer fresh... */
start = c->fresh_until + CONSENSUS_MIN_SECONDS_BEFORE_CACHING;
start = c->fresh_until + min_sec_before_caching;
/* But only in the first half-interval after that. */
dl_interval = interval/2;
} else {
@ -1150,10 +1160,9 @@ update_consensus_networkstatus_fetch_time(time_t now)
* to choose the rest of the interval *after* them. */
if (directory_fetches_dir_info_later(options)) {
/* Give all the *clients* enough time to download the consensus. */
start = start + dl_interval + CONSENSUS_MIN_SECONDS_BEFORE_CACHING;
start = start + dl_interval + min_sec_before_caching;
/* But try to get it before ours actually expires. */
dl_interval = (c->valid_until - start) -
CONSENSUS_MIN_SECONDS_BEFORE_CACHING;
dl_interval = (c->valid_until - start) - min_sec_before_caching;
}
}
if (dl_interval < 1)