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Fix serious bugs in per-bufferevent rate-limiting code

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Our old code was too zealous about deleting the refill events that
would actually make connections able to read or write again after
they had run out of bandwidth.  Under some circumstances, this could
cause a bufferevent to never actually refill one of its
rate-limiting buckets.

Also, the code treated setting a per-connection rate-limit on a
connection that already had a group-limit as if it were changing the
limit on a connection whose allocation had already run out.

This patch fixes both of those problems.
This commit is contained in:
Nick Mathewson 2010-10-12 13:46:14 -04:00
parent 819b171572
commit 34d64f8a34
1 changed files with 45 additions and 20 deletions
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65
bufferevent_ratelim.c
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@ -543,15 +543,19 @@ bufferevent_set_rate_limit(struct bufferevent *bev,
struct bufferevent_rate_limit *rlim; struct bufferevent_rate_limit *rlim;
struct timeval now; struct timeval now;
ev_uint32_t tick; ev_uint32_t tick;
int reinit = 0, suspended = 0;
/* XXX reference-count cfg */ /* XXX reference-count cfg */
BEV_LOCK(bev); BEV_LOCK(bev);
if (cfg == NULL) { if (cfg == NULL) {
if (bevp->rate_limiting) { if (bevp->rate_limiting) {
bevp->rate_limiting->cfg = NULL; rlim = bevp->rate_limiting;
rlim->cfg = NULL;
bufferevent_unsuspend_read(bev, BEV_SUSPEND_BW); bufferevent_unsuspend_read(bev, BEV_SUSPEND_BW);
bufferevent_unsuspend_write(bev, BEV_SUSPEND_BW); bufferevent_unsuspend_write(bev, BEV_SUSPEND_BW);
if (event_initialized(&rlim->refill_bucket_event))
event_del(&rlim->refill_bucket_event);
} }
r = 0; r = 0;
goto done; goto done;
@ -561,29 +565,48 @@ bufferevent_set_rate_limit(struct bufferevent *bev,
tick = ev_token_bucket_get_tick(&now, cfg); tick = ev_token_bucket_get_tick(&now, cfg);
if (bevp->rate_limiting && bevp->rate_limiting->cfg == cfg) { if (bevp->rate_limiting && bevp->rate_limiting->cfg == cfg) {
; /* no-op */
} else if (bevp->rate_limiting) { r = 0;
bevp->rate_limiting->cfg = cfg; goto done;
ev_token_bucket_init(&bevp->rate_limiting->limit, cfg, tick, 1); }
if (bevp->rate_limiting->limit.read_limit > 0) if (bevp->rate_limiting == NULL) {
bufferevent_unsuspend_read(bev, BEV_SUSPEND_BW);
else
bufferevent_suspend_read(bev, BEV_SUSPEND_BW);
if (bevp->rate_limiting->limit.write_limit > 0)
bufferevent_unsuspend_write(bev, BEV_SUSPEND_BW);
else
bufferevent_suspend_write(bev, BEV_SUSPEND_BW);
} else {
rlim = mm_calloc(1, sizeof(struct bufferevent_rate_limit)); rlim = mm_calloc(1, sizeof(struct bufferevent_rate_limit));
if (!rlim) if (!rlim)
goto done; goto done;
rlim->cfg = cfg;
ev_token_bucket_init(&rlim->limit, cfg, tick, 0);
evtimer_assign(&rlim->refill_bucket_event, bev->ev_base,
_bev_refill_callback, bevp);
bevp->rate_limiting = rlim; bevp->rate_limiting = rlim;
} else {
rlim = bevp->rate_limiting;
} }
reinit = rlim->cfg != NULL;
rlim->cfg = cfg;
ev_token_bucket_init(&rlim->limit, cfg, tick, reinit);
if (reinit) {
EVUTIL_ASSERT(event_initialized(&rlim->refill_bucket_event));
event_del(&rlim->refill_bucket_event);
}
evtimer_assign(&rlim->refill_bucket_event, bev->ev_base,
_bev_refill_callback, bevp);
if (rlim->limit.read_limit > 0) {
bufferevent_unsuspend_read(bev, BEV_SUSPEND_BW);
} else {
bufferevent_suspend_read(bev, BEV_SUSPEND_BW);
suspended=1;
}
if (rlim->limit.write_limit > 0) {
bufferevent_unsuspend_write(bev, BEV_SUSPEND_BW);
} else {
bufferevent_suspend_write(bev, BEV_SUSPEND_BW);
suspended = 1;
}
if (suspended)
event_add(&rlim->refill_bucket_event, &cfg->tick_timeout);
r = 0; r = 0;
done: done:
BEV_UNLOCK(bev); BEV_UNLOCK(bev);
return r; return r;
@ -856,7 +879,8 @@ bufferevent_decrement_read_limit(struct bufferevent *bev, ev_ssize_t decr)
&bevp->rate_limiting->cfg->tick_timeout) < 0) &bevp->rate_limiting->cfg->tick_timeout) < 0)
r = -1; r = -1;
} else if (old_limit <= 0 && new_limit > 0) { } else if (old_limit <= 0 && new_limit > 0) {
event_del(&bevp->rate_limiting->refill_bucket_event); if (!(bevp->write_suspended & BEV_SUSPEND_BW))
event_del(&bevp->rate_limiting->refill_bucket_event);
bufferevent_unsuspend_read(bev, BEV_SUSPEND_BW); bufferevent_unsuspend_read(bev, BEV_SUSPEND_BW);
} }
@ -884,7 +908,8 @@ bufferevent_decrement_write_limit(struct bufferevent *bev, ev_ssize_t decr)
&bevp->rate_limiting->cfg->tick_timeout) < 0) &bevp->rate_limiting->cfg->tick_timeout) < 0)
r = -1; r = -1;
} else if (old_limit <= 0 && new_limit > 0) { } else if (old_limit <= 0 && new_limit > 0) {
event_del(&bevp->rate_limiting->refill_bucket_event); if (!(bevp->read_suspended & BEV_SUSPEND_BW))
event_del(&bevp->rate_limiting->refill_bucket_event);
bufferevent_unsuspend_write(bev, BEV_SUSPEND_BW); bufferevent_unsuspend_write(bev, BEV_SUSPEND_BW);
} }