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r16195@catbus: nickm | 2007-10-26 18:48:52 -0400

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base "Guard" flag on WFU rather than MTBF.  Note an issue in the TODO. Roger: thoughts?


svn:r12219
This commit is contained in:
Nick Mathewson 2007-10-26 22:50:42 +00:00
parent 2c1d7cf674
commit 8fa7071121
4 changed files with 38 additions and 13 deletions
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3
ChangeLog
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@ -4,6 +4,9 @@ Changes in version 0.2.0.10-alpha - 2007-1?-??
it, it had no AES, and it hasn't seen any security patches since 2004.
o Minor features:
- Directory authorities now decide whether routers are stable enough to
be guards based not on their MTBF or their uptime, but on their
fractional uptime: the fraction of the time that they are online.
- Clients new hold circuitless TLS connections open for 1.5 times
MaxCircuitDirtiness, since it is likely that they'll need to build
a circuit over them within that timeframe. Previously, they held them

6
doc/TODO
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@ -27,7 +27,11 @@ Things we'd like to do in 0.2.0.x:
o Bump up OR the "connection timeout" value to be 1.5
circuit dirtiness interval.
o Document this in tor-spec
- base Guard flag on WFU rather than or in addition to MTBF
o base Guard flag on WFU rather than on MTBF.
o Change guard calculation
o Change dir-spec.txt
- What should we do about hosts that have been up for only 1 hour,
but have been up for 100% of that one hour?
D 118 if feasible and obvious
D Maintain a skew estimate and use ftime consistently.
- 105+TLS, if possible.

15
doc/spec/dir-spec.txt
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@ -990,11 +990,16 @@ $Id$
"Fast" -- A router is 'Fast' if it is active, and its bandwidth is
either in the top 7/8ths for known active routers or at least 100KB/s.
"Guard" -- A router is a possible 'Guard' if it is 'Stable' and its
bandwidth is either at least the median for known active routers or
at least 250KB/s. If the total bandwidth of active non-BadExit Exit
servers is less than one third of the total bandwidth of all active
servers, no Exit is listed as a Guard.
"Guard" -- A router is a possible 'Guard' if its Weighted Fractional
Uptime is at least the median for known active routers, and its bandwidth
is either at least the median for known active routers or at least
250KB/s. If the total bandwidth of active non-BadExit Exit servers is less
than one third of the total bandwidth of all active servers, no Exit is
listed as a Guard.
To calculate weighted fractional uptime, compute the fraction
of time that the router is up in any given day, weighting so that
downtime and uptime in the past counts less.
"Authority" -- A router is called an 'Authority' if the authority
generating the network-status document believes it is an authority.

19
src/or/dirserv.c
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@ -1474,6 +1474,7 @@ should_generate_v2_networkstatus(void)
static uint32_t stable_uptime = 0; /* start at a safe value */
static double stable_mtbf = 0.0;
static int enough_mtbf_info = 0;
static double guard_wfu = 0.0;
static uint32_t fast_bandwidth = 0;
static uint32_t guard_bandwidth_including_exits = 0;
static uint32_t guard_bandwidth_excluding_exits = 0;
@ -1536,7 +1537,7 @@ dirserv_compute_performance_thresholds(routerlist_t *rl)
{
int n_active, n_active_nonexit;
uint32_t *uptimes, *bandwidths, *bandwidths_excluding_exits;
double *mtbfs;
double *mtbfs, *wfus;
time_t now = time(NULL);
/* initialize these all here, in case there are no routers */
@ -1554,6 +1555,7 @@ dirserv_compute_performance_thresholds(routerlist_t *rl)
bandwidths_excluding_exits =
tor_malloc(sizeof(uint32_t)*smartlist_len(rl->routers));
mtbfs = tor_malloc(sizeof(double)*smartlist_len(rl->routers));
wfus = tor_malloc(sizeof(double)*smartlist_len(rl->routers));
SMARTLIST_FOREACH(rl->routers, routerinfo_t *, ri, {
if (router_is_active(ri, now)) {
@ -1562,6 +1564,7 @@ dirserv_compute_performance_thresholds(routerlist_t *rl)
ri->is_exit = exit_policy_is_general_exit(ri->exit_policy);
uptimes[n_active] = real_uptime(ri, now);
mtbfs[n_active] = rep_hist_get_stability(id, now);
wfus [n_active] = rep_hist_get_weighted_fractional_uptime(id, now);
bandwidths[n_active] = bw = router_get_advertised_bandwidth(ri);
total_bandwidth += bw;
if (ri->is_exit && !ri->is_bad_exit) {
@ -1577,6 +1580,7 @@ dirserv_compute_performance_thresholds(routerlist_t *rl)
if (n_active) {
stable_uptime = median_uint32(uptimes, n_active);
stable_mtbf = median_double(mtbfs, n_active);
guard_wfu = median_double(wfus, n_active);
fast_bandwidth = find_nth_uint32(bandwidths, n_active, n_active/8);
/* Now bandwidths is sorted. */
if (fast_bandwidth < ROUTER_REQUIRED_MIN_BANDWIDTH)
@ -1591,6 +1595,7 @@ dirserv_compute_performance_thresholds(routerlist_t *rl)
median_uint32(bandwidths_excluding_exits, n_active_nonexit);
}
/*XXXX020 Log the other stuff too. */
log(LOG_INFO, LD_DIRSERV,
"Cutoffs: %lus uptime, %lu b/s fast, %lu or %lu b/s guard.",
(unsigned long)stable_uptime,
@ -1600,6 +1605,7 @@ dirserv_compute_performance_thresholds(routerlist_t *rl)
tor_free(uptimes);
tor_free(mtbfs);
tor_free(wfus);
tor_free(bandwidths);
tor_free(bandwidths_excluding_exits);
}
@ -1823,12 +1829,19 @@ set_routerstatus_from_routerinfo(routerstatus_t *rs,
rs->is_unnamed = (naming && (name_status & FP_UNNAMED)) ? 1 : 0;
}
rs->is_valid = ri->is_valid;
rs->is_possible_guard = rs->is_fast && rs->is_stable &&
if (rs->is_fast &&
(!rs->is_exit || exits_can_be_guards) &&
(router_get_advertised_bandwidth(ri) >= BANDWIDTH_TO_GUARANTEE_GUARD ||
router_get_advertised_bandwidth(ri) >=
(exits_can_be_guards ? guard_bandwidth_including_exits :
guard_bandwidth_excluding_exits));
guard_bandwidth_excluding_exits))) {
double wfu = rep_hist_get_weighted_fractional_uptime(
ri->cache_info.identity_digest, now);
rs->is_possible_guard = (wfu >= guard_wfu) ? 1 : 0;
} else {
rs->is_possible_guard = 0;
}
rs->is_bad_exit = listbadexits && ri->is_bad_exit;
/* 0.1.1.9-alpha is the first version to support fetch by descriptor
* hash. */