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/* Copyright (c) 2018-2019, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file voting_schedule.c
* \brief This file contains functions that are from the directory authority
* subsystem related to voting specifically but used by many part of
* tor. The full feature is built as part of the dirauth module.
**/
#define VOTING_SCHEDULE_PRIVATE
#include "feature/dircommon/voting_schedule.h"
#include "core/or/or.h"
#include "app/config/config.h"
#include "feature/nodelist/networkstatus.h"
#include "feature/nodelist/networkstatus_st.h"
/* =====
* Vote scheduling
* ===== */
/** Return the start of the next interval of size <b>interval</b> (in
* seconds) after <b>now</b>, plus <b>offset</b>. Midnight always
* starts a fresh interval, and if the last interval of a day would be
* truncated to less than half its size, it is rolled into the
* previous interval. */
time_t
voting_schedule_get_start_of_next_interval(time_t now, int interval,
int offset)
{
struct tm tm;
time_t midnight_today=0;
time_t midnight_tomorrow;
time_t next;
tor_gmtime_r(&now, &tm);
tm.tm_hour = 0;
tm.tm_min = 0;
tm.tm_sec = 0;
if (tor_timegm(&tm, &midnight_today) < 0) {
// LCOV_EXCL_START
log_warn(LD_BUG, "Ran into an invalid time when trying to find midnight.");
// LCOV_EXCL_STOP
}
midnight_tomorrow = midnight_today + (24*60*60);
next = midnight_today + ((now-midnight_today)/interval + 1)*interval;
/* Intervals never cross midnight. */
if (next > midnight_tomorrow)
next = midnight_tomorrow;
/* If the interval would only last half as long as it's supposed to, then
* skip over to the next day. */
if (next + interval/2 > midnight_tomorrow)
next = midnight_tomorrow;
next += offset;
if (next - interval > now)
next -= interval;
return next;
}
/* Populate and return a new voting_schedule_t that can be used to schedule
* voting. The object is allocated on the heap and it's the responsibility of
* the caller to free it. Can't fail. */
static voting_schedule_t *
get_voting_schedule(const or_options_t *options, time_t now, int severity)
{
int interval, vote_delay, dist_delay;
time_t start;
time_t end;
networkstatus_t *consensus;
voting_schedule_t *new_voting_schedule;
new_voting_schedule = tor_malloc_zero(sizeof(voting_schedule_t));
consensus = networkstatus_get_live_consensus(now);
if (consensus) {
interval = (int)( consensus->fresh_until - consensus->valid_after );
vote_delay = consensus->vote_seconds;
dist_delay = consensus->dist_seconds;
/* Note down the consensus valid after, so that we detect outdated voting
* schedules in case of skewed clocks etc. */
new_voting_schedule->live_consensus_valid_after = consensus->valid_after;
} else {
interval = options->TestingV3AuthInitialVotingInterval;
vote_delay = options->TestingV3AuthInitialVoteDelay;
dist_delay = options->TestingV3AuthInitialDistDelay;
}
tor_assert(interval > 0);
if (vote_delay + dist_delay > interval/2)
vote_delay = dist_delay = interval / 4;
start = new_voting_schedule->interval_starts =
voting_schedule_get_start_of_next_interval(now,interval,
options->TestingV3AuthVotingStartOffset);
end = voting_schedule_get_start_of_next_interval(start+1, interval,
options->TestingV3AuthVotingStartOffset);
tor_assert(end > start);
new_voting_schedule->fetch_missing_signatures = start - (dist_delay/2);
new_voting_schedule->voting_ends = start - dist_delay;
new_voting_schedule->fetch_missing_votes =
start - dist_delay - (vote_delay/2);
new_voting_schedule->voting_starts = start - dist_delay - vote_delay;
{
char tbuf[ISO_TIME_LEN+1];
format_iso_time(tbuf, new_voting_schedule->interval_starts);
tor_log(severity, LD_DIR,"Choosing expected valid-after time as %s: "
"consensus_set=%d, interval=%d",
tbuf, consensus?1:0, interval);
}
return new_voting_schedule;
}
#define voting_schedule_free(s) \
FREE_AND_NULL(voting_schedule_t, voting_schedule_free_, (s))
/** Frees a voting_schedule_t. This should be used instead of the generic
* tor_free. */
static void
voting_schedule_free_(voting_schedule_t *voting_schedule_to_free)
{
if (!voting_schedule_to_free)
return;
tor_free(voting_schedule_to_free);
}
voting_schedule_t voting_schedule;
/* Using the time <b>now</b>, return the next voting valid-after time. */
time_t
voting_schedule_get_next_valid_after_time(void)
{
time_t now = approx_time();
bool need_to_recalculate_voting_schedule = false;
/* This is a safe guard in order to make sure that the voting schedule
* static object is at least initialized. Using this function with a zeroed
* voting schedule can lead to bugs. */
if (tor_mem_is_zero((const char *) &voting_schedule,
sizeof(voting_schedule))) {
need_to_recalculate_voting_schedule = true;
goto done; /* no need for next check if we have to recalculate anyway */
}
/* Also make sure we are not using an outdated voting schedule. If we have a
* newer consensus, make sure we recalculate the voting schedule. */
const networkstatus_t *ns = networkstatus_get_live_consensus(now);
if (ns && ns->valid_after != voting_schedule.live_consensus_valid_after) {
log_info(LD_DIR, "Voting schedule is outdated: recalculating (%d/%d)",
(int) ns->valid_after,
(int) voting_schedule.live_consensus_valid_after);
need_to_recalculate_voting_schedule = true;
}
done:
if (need_to_recalculate_voting_schedule) {
voting_schedule_recalculate_timing(get_options(), approx_time());
voting_schedule.created_on_demand = 1;
}
return voting_schedule.interval_starts;
}
/** Set voting_schedule to hold the timing for the next vote we should be
* doing. All type of tor do that because HS subsystem needs the timing as
* well to function properly. */
void
voting_schedule_recalculate_timing(const or_options_t *options, time_t now)
{
voting_schedule_t *new_voting_schedule;
/* get the new voting schedule */
new_voting_schedule = get_voting_schedule(options, now, LOG_INFO);
tor_assert(new_voting_schedule);
/* Fill in the global static struct now */
memcpy(&voting_schedule, new_voting_schedule, sizeof(voting_schedule));
voting_schedule_free(new_voting_schedule);
}
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