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Prefer measured bandwidths over advertised when computing things for votes on a dirauth

This commit is contained in:
Andrea Shepard 2013-02-27 19:43:50 -08:00
parent 9bc05c30d7
commit b5a164bde4
2 changed files with 201 additions and 8 deletions
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3
changes/bug8273 Normal file
View File

@ -0,0 +1,3 @@
o Critical bugfixes:
- When dirserv.c computes flags and thresholds, use measured bandwidths
in preference to advertised ones.

206
src/or/dirserv.c
View File

@ -85,6 +85,14 @@ static const signed_descriptor_t *get_signed_descriptor_by_fp(
time_t publish_cutoff);
static was_router_added_t dirserv_add_extrainfo(extrainfo_t *ei,
const char **msg);
static void dirserv_cache_measured_bw(measured_bw_line_t *parsed_line,
time_t as_of);
static void dirserv_clear_measured_bw_cache(void);
static void dirserv_expire_measured_bw_cache(time_t now);
static int dirserv_get_measured_bw_cache_size(void);
static int dirserv_query_measured_bw_cache(char *node_id, long *bw_out,
time_t *as_of_out);
static uint32_t dirserv_get_bandwidth_for_router(routerinfo_t *ri);
/************** Measured Bandwidth parsing code ******/
#define MAX_MEASUREMENT_AGE (3*24*60*60) /* 3 days */
@ -1824,7 +1832,7 @@ dirserv_thinks_router_is_unreliable(time_t now,
}
}
if (need_capacity) {
uint32_t bw = router_get_advertised_bandwidth(router);
uint32_t bw = dirserv_get_bandwidth_for_router(router);
if (bw < fast_bandwidth)
return 1;
}
@ -1883,7 +1891,7 @@ router_counts_toward_thresholds(const node_t *node, time_t now,
{
return node->ri && router_is_active(node->ri, node, now) &&
!digestmap_get(omit_as_sybil, node->ri->cache_info.identity_digest) &&
(router_get_advertised_bandwidth(node->ri) >=
(dirserv_get_bandwidth_for_router(node->ri) >=
ABSOLUTE_MIN_BW_VALUE_TO_CONSIDER);
}
@ -1947,7 +1955,7 @@ dirserv_compute_performance_thresholds(routerlist_t *rl,
uptimes[n_active] = (uint32_t)real_uptime(ri, now);
mtbfs[n_active] = rep_hist_get_stability(id, now);
tks [n_active] = rep_hist_get_weighted_time_known(id, now);
bandwidths[n_active] = bw = router_get_advertised_bandwidth(ri);
bandwidths[n_active] = bw = dirserv_get_bandwidth_for_router(ri);
total_bandwidth += bw;
if (node->is_exit && !node->is_bad_exit) {
total_exit_bandwidth += bw;
@ -2046,6 +2054,165 @@ dirserv_compute_performance_thresholds(routerlist_t *rl,
tor_free(wfus);
}
/** Measured bandwidth cache entry */
typedef struct mbw_cache_entry_s {
long mbw;
time_t as_of;
} mbw_cache_entry_t;
/** Measured bandwidth cache - keys are identity_digests, values are
* mbw_cache_entry_t *. */
static digestmap_t *mbw_cache = NULL;
/** Store a measured bandwidth cache entry when reading the measured
* bandwidths file. */
static void
dirserv_cache_measured_bw(measured_bw_line_t *parsed_line, time_t as_of)
{
mbw_cache_entry_t *e = NULL;
tor_assert(parsed_line);
/* Allocate a cache if we need */
if (!mbw_cache) mbw_cache = digestmap_new();
/* Check if we have an existing entry */
e = digestmap_get(mbw_cache, parsed_line->node_id);
/* If we do, we can re-use it */
if (e) {
/* Check that we really are newer, and update */
if (as_of > e->as_of) {
e->mbw = parsed_line->bw;
e->as_of = as_of;
}
} else {
/* We'll have to insert a new entry */
e = tor_malloc(sizeof(*e));
e->mbw = parsed_line->bw;
e->as_of = as_of;
digestmap_set(mbw_cache, parsed_line->node_id, e);
}
}
/** Clear and free the measured bandwidth cache */
static void
dirserv_clear_measured_bw_cache(void)
{
if (mbw_cache) {
/* Free the map and all entries */
digestmap_free(mbw_cache, tor_free_);
mbw_cache = NULL;
}
}
/** Scan the measured bandwidth cache and remove expired entries */
static void
dirserv_expire_measured_bw_cache(time_t now)
{
digestmap_iter_t *itr = NULL;
const char *k = NULL;
void *e_v = NULL;
mbw_cache_entry_t *e = NULL;
int rmv;
if (mbw_cache) {
/* Start iterating */
itr = digestmap_iter_init(mbw_cache);
while (!digestmap_iter_done(itr)) {
rmv = 0;
digestmap_iter_get(itr, &k, &e_v);
e = (mbw_cache_entry_t *)e_v;
if (e) {
/* Check for expiration and remove if so */
if (now - e->as_of > MAX_MEASUREMENT_AGE) {
tor_free(e);
rmv = 1;
}
} else {
/* Weird; remove it and complain */
log_warn(LD_BUG, "Saw NULL entry in measured bandwidth cache");
rmv = 1;
}
/* Advance, or remove and advance */
if (rmv) {
itr = digestmap_iter_next_rmv(mbw_cache, itr);
} else {
itr = digestmap_iter_next(mbw_cache, itr);
}
}
/* Check if we cleared the whole thing and free if so */
if (digestmap_size(mbw_cache) == 0) {
digestmap_free(mbw_cache, tor_free_);
mbw_cache = 0;
}
}
}
/** Get the current size of the measured bandwidth cache */
static int
dirserv_get_measured_bw_cache_size(void)
{
if (mbw_cache) return digestmap_size(mbw_cache);
else return 0;
}
/** Query the cache by identity digest, return value indicates whether
* we found it. */
static int
dirserv_query_measured_bw_cache(char *node_id, long *bw_out,
time_t *as_of_out)
{
mbw_cache_entry_t *v = NULL;
int rv = 0;
if (mbw_cache && node_id) {
v = digestmap_get(mbw_cache, node_id);
if (v) {
/* Found something */
rv = 1;
if (bw_out) *bw_out = v->mbw;
if (as_of_out) *as_of_out = v->as_of;
}
}
return rv;
}
/** Get the best estimate of a router's bandwidth for dirauth purposes,
* preferring measured to advertised values if available. */
static uint32_t
dirserv_get_bandwidth_for_router(routerinfo_t *ri)
{
uint32_t bw = 0;
/*
* Yeah, measured bandwidths in measured_bw_line_t are (implicitly
* signed) longs and the ones router_get_advertised_bandwidth() returns
* are uint32_t.
*/
long mbw = 0;
if (ri) {
/*
* * First try to see if we have a measured bandwidth; don't bother with
* as_of_out here, on the theory that a stale measured bandwidth is still
* better to trust than an advertised one.
*/
if (dirserv_query_measured_bw_cache(ri->cache_info.identity_digest,
&mbw, NULL)) {
/* Got one! */
bw = (uint32_t)mbw;
} else {
/* If not, fall back to advertised */
bw = router_get_advertised_bandwidth(ri);
}
}
return bw;
}
/** Give a statement of our current performance thresholds for inclusion
* in a vote document. */
char *
@ -2327,8 +2494,8 @@ compare_routerinfo_by_ip_and_bw_(const void **a, const void **b)
else if (!first_is_running && second_is_running)
return 1;
bw_first = router_get_advertised_bandwidth(first);
bw_second = router_get_advertised_bandwidth(second);
bw_first = dirserv_get_bandwidth_for_router(first);
bw_second = dirserv_get_bandwidth_for_router(second);
if (bw_first > bw_second)
return -1;
@ -2468,7 +2635,7 @@ set_routerstatus_from_routerinfo(routerstatus_t *rs,
int listbaddirs, int vote_on_hsdirs)
{
const or_options_t *options = get_options();
uint32_t routerbw = router_get_advertised_bandwidth(ri);
uint32_t routerbw = dirserv_get_bandwidth_for_router(ri);
memset(rs, 0, sizeof(routerstatus_t));
@ -2670,8 +2837,9 @@ dirserv_read_measured_bandwidths(const char *from_file,
char line[256];
FILE *fp = tor_fopen_cloexec(from_file, "r");
int applied_lines = 0;
time_t file_time;
time_t file_time, now;
int ok;
if (fp == NULL) {
log_warn(LD_CONFIG, "Can't open bandwidth file at configured location: %s",
from_file);
@ -2695,7 +2863,8 @@ dirserv_read_measured_bandwidths(const char *from_file,
return -1;
}
if ((time(NULL) - file_time) > MAX_MEASUREMENT_AGE) {
now = time(NULL);
if ((now - file_time) > MAX_MEASUREMENT_AGE) {
log_warn(LD_DIRSERV, "Bandwidth measurement file stale. Age: %u",
(unsigned)(time(NULL) - file_time));
fclose(fp);
@ -2709,12 +2878,17 @@ dirserv_read_measured_bandwidths(const char *from_file,
measured_bw_line_t parsed_line;
if (fgets(line, sizeof(line), fp) && strlen(line)) {
if (measured_bw_line_parse(&parsed_line, line) != -1) {
/* Also cache the line for dirserv_get_bandwidth_for_router() */
dirserv_cache_measured_bw(&parsed_line, file_time);
if (measured_bw_line_apply(&parsed_line, routerstatuses) > 0)
applied_lines++;
}
}
}
/* Now would be a nice time to clean the cache, too */
dirserv_expire_measured_bw_cache(now);
fclose(fp);
log_info(LD_DIRSERV,
"Bandwidth measurement file successfully read. "
@ -2778,6 +2952,14 @@ dirserv_generate_networkstatus_vote_obj(crypto_pk_t *private_key,
if (!contact)
contact = "(none)";
/*
* Do this so dirserv_compute_performance_thresholds() and
* set_routerstatus_from_routerinfo() see up-to-date bandwidth info.
*/
if (options->V3BandwidthsFile) {
dirserv_read_measured_bandwidths(options->V3BandwidthsFile, NULL);
}
/* precompute this part, since we need it to decide what "stable"
* means. */
SMARTLIST_FOREACH(rl->routers, routerinfo_t *, ri, {
@ -2841,6 +3023,14 @@ dirserv_generate_networkstatus_vote_obj(crypto_pk_t *private_key,
if (options->V3BandwidthsFile) {
dirserv_read_measured_bandwidths(options->V3BandwidthsFile,
routerstatuses);
} else {
/*
* No bandwidths file; clear the measured bandwidth cache in case we had
* one last time around.
*/
if (dirserv_get_measured_bw_cache_size() > 0) {
dirserv_clear_measured_bw_cache();
}
}
v3_out = tor_malloc_zero(sizeof(networkstatus_t));