Adding upstream version 1.0.18.upstream/1.0.18upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1089 insertions, 0 deletions

diff --git a/libevent/bufferevent_ratelim.c b/libevent/bufferevent_ratelim.c
new file mode 100644
index 0000000..2587496
--- /dev/null
+++ b/libevent/bufferevent_ratelim.c
@@ -0,0 +1,1089 @@
+/*
+ * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
+ * Copyright (c) 2002-2006 Niels Provos <provos@citi.umich.edu>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include "evconfig-private.h"
+
+#include <sys/types.h>
+#include <limits.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "event2/event.h"
+#include "event2/event_struct.h"
+#include "event2/util.h"
+#include "event2/bufferevent.h"
+#include "event2/bufferevent_struct.h"
+#include "event2/buffer.h"
+
+#include "ratelim-internal.h"
+
+#include "bufferevent-internal.h"
+#include "mm-internal.h"
+#include "util-internal.h"
+#include "event-internal.h"
+
+int
+ev_token_bucket_init_(struct ev_token_bucket *bucket,
+    const struct ev_token_bucket_cfg *cfg,
+    ev_uint32_t current_tick,
+    int reinitialize)
+{
+	if (reinitialize) {
+		/* on reinitialization, we only clip downwards, since we've
+		   already used who-knows-how-much bandwidth this tick.  We
+		   leave "last_updated" as it is; the next update will add the
+		   appropriate amount of bandwidth to the bucket.
+		*/
+		if (bucket->read_limit > (ev_int64_t) cfg->read_maximum)
+			bucket->read_limit = cfg->read_maximum;
+		if (bucket->write_limit > (ev_int64_t) cfg->write_maximum)
+			bucket->write_limit = cfg->write_maximum;
+	} else {
+		bucket->read_limit = cfg->read_rate;
+		bucket->write_limit = cfg->write_rate;
+		bucket->last_updated = current_tick;
+	}
+	return 0;
+}
+
+int
+ev_token_bucket_update_(struct ev_token_bucket *bucket,
+    const struct ev_token_bucket_cfg *cfg,
+    ev_uint32_t current_tick)
+{
+	/* It's okay if the tick number overflows, since we'll just
+	 * wrap around when we do the unsigned substraction. */
+	unsigned n_ticks = current_tick - bucket->last_updated;
+
+	/* Make sure some ticks actually happened, and that time didn't
+	 * roll back. */
+	if (n_ticks == 0 || n_ticks > INT_MAX)
+		return 0;
+
+	/* Naively, we would say
+		bucket->limit += n_ticks * cfg->rate;
+
+		if (bucket->limit > cfg->maximum)
+			bucket->limit = cfg->maximum;
+
+	   But we're worried about overflow, so we do it like this:
+	*/
+
+	if ((cfg->read_maximum - bucket->read_limit) / n_ticks < cfg->read_rate)
+		bucket->read_limit = cfg->read_maximum;
+	else
+		bucket->read_limit += n_ticks * cfg->read_rate;
+
+
+	if ((cfg->write_maximum - bucket->write_limit) / n_ticks < cfg->write_rate)
+		bucket->write_limit = cfg->write_maximum;
+	else
+		bucket->write_limit += n_ticks * cfg->write_rate;
+
+
+	bucket->last_updated = current_tick;
+
+	return 1;
+}
+
+static inline void
+bufferevent_update_buckets(struct bufferevent_private *bev)
+{
+	/* Must hold lock on bev. */
+	struct timeval now;
+	unsigned tick;
+	event_base_gettimeofday_cached(bev->bev.ev_base, &now);
+	tick = ev_token_bucket_get_tick_(&now, bev->rate_limiting->cfg);
+	if (tick != bev->rate_limiting->limit.last_updated)
+		ev_token_bucket_update_(&bev->rate_limiting->limit,
+		    bev->rate_limiting->cfg, tick);
+}
+
+ev_uint32_t
+ev_token_bucket_get_tick_(const struct timeval *tv,
+    const struct ev_token_bucket_cfg *cfg)
+{
+	/* This computation uses two multiplies and a divide.  We could do
+	 * fewer if we knew that the tick length was an integer number of
+	 * seconds, or if we knew it divided evenly into a second.  We should
+	 * investigate that more.
+	 */
+
+	/* We cast to an ev_uint64_t first, since we don't want to overflow
+	 * before we do the final divide. */
+	ev_uint64_t msec = (ev_uint64_t)tv->tv_sec * 1000 + tv->tv_usec / 1000;
+	return (unsigned)(msec / cfg->msec_per_tick);
+}
+
+struct ev_token_bucket_cfg *
+ev_token_bucket_cfg_new(size_t read_rate, size_t read_burst,
+    size_t write_rate, size_t write_burst,
+    const struct timeval *tick_len)
+{
+	struct ev_token_bucket_cfg *r;
+	struct timeval g;
+	if (! tick_len) {
+		g.tv_sec = 1;
+		g.tv_usec = 0;
+		tick_len = &g;
+	}
+	if (read_rate > read_burst || write_rate > write_burst ||
+	    read_rate < 1 || write_rate < 1)
+		return NULL;
+	if (read_rate > EV_RATE_LIMIT_MAX ||
+	    write_rate > EV_RATE_LIMIT_MAX ||
+	    read_burst > EV_RATE_LIMIT_MAX ||
+	    write_burst > EV_RATE_LIMIT_MAX)
+		return NULL;
+	r = mm_calloc(1, sizeof(struct ev_token_bucket_cfg));
+	if (!r)
+		return NULL;
+	r->read_rate = read_rate;
+	r->write_rate = write_rate;
+	r->read_maximum = read_burst;
+	r->write_maximum = write_burst;
+	memcpy(&r->tick_timeout, tick_len, sizeof(struct timeval));
+	r->msec_per_tick = (tick_len->tv_sec * 1000) +
+	    (tick_len->tv_usec & COMMON_TIMEOUT_MICROSECONDS_MASK)/1000;
+	return r;
+}
+
+void
+ev_token_bucket_cfg_free(struct ev_token_bucket_cfg *cfg)
+{
+	mm_free(cfg);
+}
+
+/* Default values for max_single_read & max_single_write variables. */
+#define MAX_SINGLE_READ_DEFAULT 16384
+#define MAX_SINGLE_WRITE_DEFAULT 16384
+
+#define LOCK_GROUP(g) EVLOCK_LOCK((g)->lock, 0)
+#define UNLOCK_GROUP(g) EVLOCK_UNLOCK((g)->lock, 0)
+
+static int bev_group_suspend_reading_(struct bufferevent_rate_limit_group *g);
+static int bev_group_suspend_writing_(struct bufferevent_rate_limit_group *g);
+static void bev_group_unsuspend_reading_(struct bufferevent_rate_limit_group *g);
+static void bev_group_unsuspend_writing_(struct bufferevent_rate_limit_group *g);
+
+/** Helper: figure out the maximum amount we should write if is_write, or
+    the maximum amount we should read if is_read.  Return that maximum, or
+    0 if our bucket is wholly exhausted.
+ */
+static inline ev_ssize_t
+bufferevent_get_rlim_max_(struct bufferevent_private *bev, int is_write)
+{
+	/* needs lock on bev. */
+	ev_ssize_t max_so_far = is_write?bev->max_single_write:bev->max_single_read;
+
+#define LIM(x)						\
+	(is_write ? (x).write_limit : (x).read_limit)
+
+#define GROUP_SUSPENDED(g)			\
+	(is_write ? (g)->write_suspended : (g)->read_suspended)
+
+	/* Sets max_so_far to MIN(x, max_so_far) */
+#define CLAMPTO(x)				\
+	do {					\
+		if (max_so_far > (x))		\
+			max_so_far = (x);	\
+	} while (0);
+
+	if (!bev->rate_limiting)
+		return max_so_far;
+
+	/* If rate-limiting is enabled at all, update the appropriate
+	   bucket, and take the smaller of our rate limit and the group
+	   rate limit.
+	 */
+
+	if (bev->rate_limiting->cfg) {
+		bufferevent_update_buckets(bev);
+		max_so_far = LIM(bev->rate_limiting->limit);
+	}
+	if (bev->rate_limiting->group) {
+		struct bufferevent_rate_limit_group *g =
+		    bev->rate_limiting->group;
+		ev_ssize_t share;
+		LOCK_GROUP(g);
+		if (GROUP_SUSPENDED(g)) {
+			/* We can get here if we failed to lock this
+			 * particular bufferevent while suspending the whole
+			 * group. */
+			if (is_write)
+				bufferevent_suspend_write_(&bev->bev,
+				    BEV_SUSPEND_BW_GROUP);
+			else
+				bufferevent_suspend_read_(&bev->bev,
+				    BEV_SUSPEND_BW_GROUP);
+			share = 0;
+		} else {
+			/* XXXX probably we should divide among the active
+			 * members, not the total members. */
+			share = LIM(g->rate_limit) / g->n_members;
+			if (share < g->min_share)
+				share = g->min_share;
+		}
+		UNLOCK_GROUP(g);
+		CLAMPTO(share);
+	}
+
+	if (max_so_far < 0)
+		max_so_far = 0;
+	return max_so_far;
+}
+
+ev_ssize_t
+bufferevent_get_read_max_(struct bufferevent_private *bev)
+{
+	return bufferevent_get_rlim_max_(bev, 0);
+}
+
+ev_ssize_t
+bufferevent_get_write_max_(struct bufferevent_private *bev)
+{
+	return bufferevent_get_rlim_max_(bev, 1);
+}
+
+int
+bufferevent_decrement_read_buckets_(struct bufferevent_private *bev, ev_ssize_t bytes)
+{
+	/* XXXXX Make sure all users of this function check its return value */
+	int r = 0;
+	/* need to hold lock on bev */
+	if (!bev->rate_limiting)
+		return 0;
+
+	if (bev->rate_limiting->cfg) {
+		bev->rate_limiting->limit.read_limit -= bytes;
+		if (bev->rate_limiting->limit.read_limit <= 0) {
+			bufferevent_suspend_read_(&bev->bev, BEV_SUSPEND_BW);
+			if (event_add(&bev->rate_limiting->refill_bucket_event,
+				&bev->rate_limiting->cfg->tick_timeout) < 0)
+				r = -1;
+		} else if (bev->read_suspended & BEV_SUSPEND_BW) {
+			if (!(bev->write_suspended & BEV_SUSPEND_BW))
+				event_del(&bev->rate_limiting->refill_bucket_event);
+			bufferevent_unsuspend_read_(&bev->bev, BEV_SUSPEND_BW);
+		}
+	}
+
+	if (bev->rate_limiting->group) {
+		LOCK_GROUP(bev->rate_limiting->group);
+		bev->rate_limiting->group->rate_limit.read_limit -= bytes;
+		bev->rate_limiting->group->total_read += bytes;
+		if (bev->rate_limiting->group->rate_limit.read_limit <= 0) {
+			bev_group_suspend_reading_(bev->rate_limiting->group);
+		} else if (bev->rate_limiting->group->read_suspended) {
+			bev_group_unsuspend_reading_(bev->rate_limiting->group);
+		}
+		UNLOCK_GROUP(bev->rate_limiting->group);
+	}
+
+	return r;
+}
+
+int
+bufferevent_decrement_write_buckets_(struct bufferevent_private *bev, ev_ssize_t bytes)
+{
+	/* XXXXX Make sure all users of this function check its return value */
+	int r = 0;
+	/* need to hold lock */
+	if (!bev->rate_limiting)
+		return 0;
+
+	if (bev->rate_limiting->cfg) {
+		bev->rate_limiting->limit.write_limit -= bytes;
+		if (bev->rate_limiting->limit.write_limit <= 0) {
+			bufferevent_suspend_write_(&bev->bev, BEV_SUSPEND_BW);
+			if (event_add(&bev->rate_limiting->refill_bucket_event,
+				&bev->rate_limiting->cfg->tick_timeout) < 0)
+				r = -1;
+		} else if (bev->write_suspended & BEV_SUSPEND_BW) {
+			if (!(bev->read_suspended & BEV_SUSPEND_BW))
+				event_del(&bev->rate_limiting->refill_bucket_event);
+			bufferevent_unsuspend_write_(&bev->bev, BEV_SUSPEND_BW);
+		}
+	}
+
+	if (bev->rate_limiting->group) {
+		LOCK_GROUP(bev->rate_limiting->group);
+		bev->rate_limiting->group->rate_limit.write_limit -= bytes;
+		bev->rate_limiting->group->total_written += bytes;
+		if (bev->rate_limiting->group->rate_limit.write_limit <= 0) {
+			bev_group_suspend_writing_(bev->rate_limiting->group);
+		} else if (bev->rate_limiting->group->write_suspended) {
+			bev_group_unsuspend_writing_(bev->rate_limiting->group);
+		}
+		UNLOCK_GROUP(bev->rate_limiting->group);
+	}
+
+	return r;
+}
+
+/** Stop reading on every bufferevent in <b>g</b> */
+static int
+bev_group_suspend_reading_(struct bufferevent_rate_limit_group *g)
+{
+	/* Needs group lock */
+	struct bufferevent_private *bev;
+	g->read_suspended = 1;
+	g->pending_unsuspend_read = 0;
+
+	/* Note that in this loop we call EVLOCK_TRY_LOCK_ instead of BEV_LOCK,
+	   to prevent a deadlock.  (Ordinarily, the group lock nests inside
+	   the bufferevent locks.  If we are unable to lock any individual
+	   bufferevent, it will find out later when it looks at its limit
+	   and sees that its group is suspended.)
+	*/
+	LIST_FOREACH(bev, &g->members, rate_limiting->next_in_group) {
+		if (EVLOCK_TRY_LOCK_(bev->lock)) {
+			bufferevent_suspend_read_(&bev->bev,
+			    BEV_SUSPEND_BW_GROUP);
+			EVLOCK_UNLOCK(bev->lock, 0);
+		}
+	}
+	return 0;
+}
+
+/** Stop writing on every bufferevent in <b>g</b> */
+static int
+bev_group_suspend_writing_(struct bufferevent_rate_limit_group *g)
+{
+	/* Needs group lock */
+	struct bufferevent_private *bev;
+	g->write_suspended = 1;
+	g->pending_unsuspend_write = 0;
+	LIST_FOREACH(bev, &g->members, rate_limiting->next_in_group) {
+		if (EVLOCK_TRY_LOCK_(bev->lock)) {
+			bufferevent_suspend_write_(&bev->bev,
+			    BEV_SUSPEND_BW_GROUP);
+			EVLOCK_UNLOCK(bev->lock, 0);
+		}
+	}
+	return 0;
+}
+
+/** Timer callback invoked on a single bufferevent with one or more exhausted
+    buckets when they are ready to refill. */
+static void
+bev_refill_callback_(evutil_socket_t fd, short what, void *arg)
+{
+	unsigned tick;
+	struct timeval now;
+	struct bufferevent_private *bev = arg;
+	int again = 0;
+	BEV_LOCK(&bev->bev);
+	if (!bev->rate_limiting || !bev->rate_limiting->cfg) {
+		BEV_UNLOCK(&bev->bev);
+		return;
+	}
+
+	/* First, update the bucket */
+	event_base_gettimeofday_cached(bev->bev.ev_base, &now);
+	tick = ev_token_bucket_get_tick_(&now,
+	    bev->rate_limiting->cfg);
+	ev_token_bucket_update_(&bev->rate_limiting->limit,
+	    bev->rate_limiting->cfg,
+	    tick);
+
+	/* Now unsuspend any read/write operations as appropriate. */
+	if ((bev->read_suspended & BEV_SUSPEND_BW)) {
+		if (bev->rate_limiting->limit.read_limit > 0)
+			bufferevent_unsuspend_read_(&bev->bev, BEV_SUSPEND_BW);
+		else
+			again = 1;
+	}
+	if ((bev->write_suspended & BEV_SUSPEND_BW)) {
+		if (bev->rate_limiting->limit.write_limit > 0)
+			bufferevent_unsuspend_write_(&bev->bev, BEV_SUSPEND_BW);
+		else
+			again = 1;
+	}
+	if (again) {
+		/* One or more of the buckets may need another refill if they
+		   started negative.
+
+		   XXXX if we need to be quiet for more ticks, we should
+		   maybe figure out what timeout we really want.
+		*/
+		/* XXXX Handle event_add failure somehow */
+		event_add(&bev->rate_limiting->refill_bucket_event,
+		    &bev->rate_limiting->cfg->tick_timeout);
+	}
+	BEV_UNLOCK(&bev->bev);
+}
+
+/** Helper: grab a random element from a bufferevent group.
+ *
+ * Requires that we hold the lock on the group.
+ */
+static struct bufferevent_private *
+bev_group_random_element_(struct bufferevent_rate_limit_group *group)
+{
+	int which;
+	struct bufferevent_private *bev;
+
+	/* requires group lock */
+
+	if (!group->n_members)
+		return NULL;
+
+	EVUTIL_ASSERT(! LIST_EMPTY(&group->members));
+
+	which = evutil_weakrand_range_(&group->weakrand_seed, group->n_members);
+
+	bev = LIST_FIRST(&group->members);
+	while (which--)
+		bev = LIST_NEXT(bev, rate_limiting->next_in_group);
+
+	return bev;
+}
+
+/** Iterate over the elements of a rate-limiting group 'g' with a random
+    starting point, assigning each to the variable 'bev', and executing the
+    block 'block'.
+
+    We do this in a half-baked effort to get fairness among group members.
+    XXX Round-robin or some kind of priority queue would be even more fair.
+ */
+#define FOREACH_RANDOM_ORDER(block)			\
+	do {						\
+		first = bev_group_random_element_(g);	\
+		for (bev = first; bev != LIST_END(&g->members); \
+		    bev = LIST_NEXT(bev, rate_limiting->next_in_group)) { \
+			block ;					 \
+		}						 \
+		for (bev = LIST_FIRST(&g->members); bev && bev != first; \
+		    bev = LIST_NEXT(bev, rate_limiting->next_in_group)) { \
+			block ;						\
+		}							\
+	} while (0)
+
+static void
+bev_group_unsuspend_reading_(struct bufferevent_rate_limit_group *g)
+{
+	int again = 0;
+	struct bufferevent_private *bev, *first;
+
+	g->read_suspended = 0;
+	FOREACH_RANDOM_ORDER({
+		if (EVLOCK_TRY_LOCK_(bev->lock)) {
+			bufferevent_unsuspend_read_(&bev->bev,
+			    BEV_SUSPEND_BW_GROUP);
+			EVLOCK_UNLOCK(bev->lock, 0);
+		} else {
+			again = 1;
+		}
+	});
+	g->pending_unsuspend_read = again;
+}
+
+static void
+bev_group_unsuspend_writing_(struct bufferevent_rate_limit_group *g)
+{
+	int again = 0;
+	struct bufferevent_private *bev, *first;
+	g->write_suspended = 0;
+
+	FOREACH_RANDOM_ORDER({
+		if (EVLOCK_TRY_LOCK_(bev->lock)) {
+			bufferevent_unsuspend_write_(&bev->bev,
+			    BEV_SUSPEND_BW_GROUP);
+			EVLOCK_UNLOCK(bev->lock, 0);
+		} else {
+			again = 1;
+		}
+	});
+	g->pending_unsuspend_write = again;
+}
+
+/** Callback invoked every tick to add more elements to the group bucket
+    and unsuspend group members as needed.
+ */
+static void
+bev_group_refill_callback_(evutil_socket_t fd, short what, void *arg)
+{
+	struct bufferevent_rate_limit_group *g = arg;
+	unsigned tick;
+	struct timeval now;
+
+	event_base_gettimeofday_cached(event_get_base(&g->master_refill_event), &now);
+
+	LOCK_GROUP(g);
+
+	tick = ev_token_bucket_get_tick_(&now, &g->rate_limit_cfg);
+	ev_token_bucket_update_(&g->rate_limit, &g->rate_limit_cfg, tick);
+
+	if (g->pending_unsuspend_read ||
+	    (g->read_suspended && (g->rate_limit.read_limit >= g->min_share))) {
+		bev_group_unsuspend_reading_(g);
+	}
+	if (g->pending_unsuspend_write ||
+	    (g->write_suspended && (g->rate_limit.write_limit >= g->min_share))){
+		bev_group_unsuspend_writing_(g);
+	}
+
+	/* XXXX Rather than waiting to the next tick to unsuspend stuff
+	 * with pending_unsuspend_write/read, we should do it on the
+	 * next iteration of the mainloop.
+	 */
+
+	UNLOCK_GROUP(g);
+}
+
+int
+bufferevent_set_rate_limit(struct bufferevent *bev,
+    struct ev_token_bucket_cfg *cfg)
+{
+	struct bufferevent_private *bevp = BEV_UPCAST(bev);
+	int r = -1;
+	struct bufferevent_rate_limit *rlim;
+	struct timeval now;
+	ev_uint32_t tick;
+	int reinit = 0, suspended = 0;
+	/* XXX reference-count cfg */
+
+	BEV_LOCK(bev);
+
+	if (cfg == NULL) {
+		if (bevp->rate_limiting) {
+			rlim = bevp->rate_limiting;
+			rlim->cfg = NULL;
+			bufferevent_unsuspend_read_(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;
+		goto done;
+	}
+
+	event_base_gettimeofday_cached(bev->ev_base, &now);
+	tick = ev_token_bucket_get_tick_(&now, cfg);
+
+	if (bevp->rate_limiting && bevp->rate_limiting->cfg == cfg) {
+		/* no-op */
+		r = 0;
+		goto done;
+	}
+	if (bevp->rate_limiting == NULL) {
+		rlim = mm_calloc(1, sizeof(struct bufferevent_rate_limit));
+		if (!rlim)
+			goto done;
+		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);
+	}
+	event_assign(&rlim->refill_bucket_event, bev->ev_base,
+	    -1, EV_FINALIZE, 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;
+
+done:
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+struct bufferevent_rate_limit_group *
+bufferevent_rate_limit_group_new(struct event_base *base,
+    const struct ev_token_bucket_cfg *cfg)
+{
+	struct bufferevent_rate_limit_group *g;
+	struct timeval now;
+	ev_uint32_t tick;
+
+	event_base_gettimeofday_cached(base, &now);
+	tick = ev_token_bucket_get_tick_(&now, cfg);
+
+	g = mm_calloc(1, sizeof(struct bufferevent_rate_limit_group));
+	if (!g)
+		return NULL;
+	memcpy(&g->rate_limit_cfg, cfg, sizeof(g->rate_limit_cfg));
+	LIST_INIT(&g->members);
+
+	ev_token_bucket_init_(&g->rate_limit, cfg, tick, 0);
+
+	event_assign(&g->master_refill_event, base, -1, EV_PERSIST|EV_FINALIZE,
+	    bev_group_refill_callback_, g);
+	/*XXXX handle event_add failure */
+	event_add(&g->master_refill_event, &cfg->tick_timeout);
+
+	EVTHREAD_ALLOC_LOCK(g->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+
+	bufferevent_rate_limit_group_set_min_share(g, 64);
+
+	evutil_weakrand_seed_(&g->weakrand_seed,
+	    (ev_uint32_t) ((now.tv_sec + now.tv_usec) + (ev_intptr_t)g));
+
+	return g;
+}
+
+int
+bufferevent_rate_limit_group_set_cfg(
+	struct bufferevent_rate_limit_group *g,
+	const struct ev_token_bucket_cfg *cfg)
+{
+	int same_tick;
+	if (!g || !cfg)
+		return -1;
+
+	LOCK_GROUP(g);
+	same_tick = evutil_timercmp(
+		&g->rate_limit_cfg.tick_timeout, &cfg->tick_timeout, ==);
+	memcpy(&g->rate_limit_cfg, cfg, sizeof(g->rate_limit_cfg));
+
+	if (g->rate_limit.read_limit > (ev_ssize_t)cfg->read_maximum)
+		g->rate_limit.read_limit = cfg->read_maximum;
+	if (g->rate_limit.write_limit > (ev_ssize_t)cfg->write_maximum)
+		g->rate_limit.write_limit = cfg->write_maximum;
+
+	if (!same_tick) {
+		/* This can cause a hiccup in the schedule */
+		event_add(&g->master_refill_event, &cfg->tick_timeout);
+	}
+
+	/* The new limits might force us to adjust min_share differently. */
+	bufferevent_rate_limit_group_set_min_share(g, g->configured_min_share);
+
+	UNLOCK_GROUP(g);
+	return 0;
+}
+
+int
+bufferevent_rate_limit_group_set_min_share(
+	struct bufferevent_rate_limit_group *g,
+	size_t share)
+{
+	if (share > EV_SSIZE_MAX)
+		return -1;
+
+	g->configured_min_share = share;
+
+	/* Can't set share to less than the one-tick maximum.  IOW, at steady
+	 * state, at least one connection can go per tick. */
+	if (share > g->rate_limit_cfg.read_rate)
+		share = g->rate_limit_cfg.read_rate;
+	if (share > g->rate_limit_cfg.write_rate)
+		share = g->rate_limit_cfg.write_rate;
+
+	g->min_share = share;
+	return 0;
+}
+
+void
+bufferevent_rate_limit_group_free(struct bufferevent_rate_limit_group *g)
+{
+	LOCK_GROUP(g);
+	EVUTIL_ASSERT(0 == g->n_members);
+	event_del(&g->master_refill_event);
+	UNLOCK_GROUP(g);
+	EVTHREAD_FREE_LOCK(g->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+	mm_free(g);
+}
+
+int
+bufferevent_add_to_rate_limit_group(struct bufferevent *bev,
+    struct bufferevent_rate_limit_group *g)
+{
+	int wsuspend, rsuspend;
+	struct bufferevent_private *bevp = BEV_UPCAST(bev);
+	BEV_LOCK(bev);
+
+	if (!bevp->rate_limiting) {
+		struct bufferevent_rate_limit *rlim;
+		rlim = mm_calloc(1, sizeof(struct bufferevent_rate_limit));
+		if (!rlim) {
+			BEV_UNLOCK(bev);
+			return -1;
+		}
+		event_assign(&rlim->refill_bucket_event, bev->ev_base,
+		    -1, EV_FINALIZE, bev_refill_callback_, bevp);
+		bevp->rate_limiting = rlim;
+	}
+
+	if (bevp->rate_limiting->group == g) {
+		BEV_UNLOCK(bev);
+		return 0;
+	}
+	if (bevp->rate_limiting->group)
+		bufferevent_remove_from_rate_limit_group(bev);
+
+	LOCK_GROUP(g);
+	bevp->rate_limiting->group = g;
+	++g->n_members;
+	LIST_INSERT_HEAD(&g->members, bevp, rate_limiting->next_in_group);
+
+	rsuspend = g->read_suspended;
+	wsuspend = g->write_suspended;
+
+	UNLOCK_GROUP(g);
+
+	if (rsuspend)
+		bufferevent_suspend_read_(bev, BEV_SUSPEND_BW_GROUP);
+	if (wsuspend)
+		bufferevent_suspend_write_(bev, BEV_SUSPEND_BW_GROUP);
+
+	BEV_UNLOCK(bev);
+	return 0;
+}
+
+int
+bufferevent_remove_from_rate_limit_group(struct bufferevent *bev)
+{
+	return bufferevent_remove_from_rate_limit_group_internal_(bev, 1);
+}
+
+int
+bufferevent_remove_from_rate_limit_group_internal_(struct bufferevent *bev,
+    int unsuspend)
+{
+	struct bufferevent_private *bevp = BEV_UPCAST(bev);
+	BEV_LOCK(bev);
+	if (bevp->rate_limiting && bevp->rate_limiting->group) {
+		struct bufferevent_rate_limit_group *g =
+		    bevp->rate_limiting->group;
+		LOCK_GROUP(g);
+		bevp->rate_limiting->group = NULL;
+		--g->n_members;
+		LIST_REMOVE(bevp, rate_limiting->next_in_group);
+		UNLOCK_GROUP(g);
+	}
+	if (unsuspend) {
+		bufferevent_unsuspend_read_(bev, BEV_SUSPEND_BW_GROUP);
+		bufferevent_unsuspend_write_(bev, BEV_SUSPEND_BW_GROUP);
+	}
+	BEV_UNLOCK(bev);
+	return 0;
+}
+
+/* ===
+ * API functions to expose rate limits.
+ *
+ * Don't use these from inside Libevent; they're meant to be for use by
+ * the program.
+ * === */
+
+/* Mostly you don't want to use this function from inside libevent;
+ * bufferevent_get_read_max_() is more likely what you want*/
+ev_ssize_t
+bufferevent_get_read_limit(struct bufferevent *bev)
+{
+	ev_ssize_t r;
+	struct bufferevent_private *bevp;
+	BEV_LOCK(bev);
+	bevp = BEV_UPCAST(bev);
+	if (bevp->rate_limiting && bevp->rate_limiting->cfg) {
+		bufferevent_update_buckets(bevp);
+		r = bevp->rate_limiting->limit.read_limit;
+	} else {
+		r = EV_SSIZE_MAX;
+	}
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+/* Mostly you don't want to use this function from inside libevent;
+ * bufferevent_get_write_max_() is more likely what you want*/
+ev_ssize_t
+bufferevent_get_write_limit(struct bufferevent *bev)
+{
+	ev_ssize_t r;
+	struct bufferevent_private *bevp;
+	BEV_LOCK(bev);
+	bevp = BEV_UPCAST(bev);
+	if (bevp->rate_limiting && bevp->rate_limiting->cfg) {
+		bufferevent_update_buckets(bevp);
+		r = bevp->rate_limiting->limit.write_limit;
+	} else {
+		r = EV_SSIZE_MAX;
+	}
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+int
+bufferevent_set_max_single_read(struct bufferevent *bev, size_t size)
+{
+	struct bufferevent_private *bevp;
+	BEV_LOCK(bev);
+	bevp = BEV_UPCAST(bev);
+	if (size == 0 || size > EV_SSIZE_MAX)
+		bevp->max_single_read = MAX_SINGLE_READ_DEFAULT;
+	else
+		bevp->max_single_read = size;
+	BEV_UNLOCK(bev);
+	return 0;
+}
+
+int
+bufferevent_set_max_single_write(struct bufferevent *bev, size_t size)
+{
+	struct bufferevent_private *bevp;
+	BEV_LOCK(bev);
+	bevp = BEV_UPCAST(bev);
+	if (size == 0 || size > EV_SSIZE_MAX)
+		bevp->max_single_write = MAX_SINGLE_WRITE_DEFAULT;
+	else
+		bevp->max_single_write = size;
+	BEV_UNLOCK(bev);
+	return 0;
+}
+
+ev_ssize_t
+bufferevent_get_max_single_read(struct bufferevent *bev)
+{
+	ev_ssize_t r;
+
+	BEV_LOCK(bev);
+	r = BEV_UPCAST(bev)->max_single_read;
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+ev_ssize_t
+bufferevent_get_max_single_write(struct bufferevent *bev)
+{
+	ev_ssize_t r;
+
+	BEV_LOCK(bev);
+	r = BEV_UPCAST(bev)->max_single_write;
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+ev_ssize_t
+bufferevent_get_max_to_read(struct bufferevent *bev)
+{
+	ev_ssize_t r;
+	BEV_LOCK(bev);
+	r = bufferevent_get_read_max_(BEV_UPCAST(bev));
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+ev_ssize_t
+bufferevent_get_max_to_write(struct bufferevent *bev)
+{
+	ev_ssize_t r;
+	BEV_LOCK(bev);
+	r = bufferevent_get_write_max_(BEV_UPCAST(bev));
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+const struct ev_token_bucket_cfg *
+bufferevent_get_token_bucket_cfg(const struct bufferevent *bev) {
+	struct bufferevent_private *bufev_private = BEV_UPCAST(bev);
+	struct ev_token_bucket_cfg *cfg;
+
+	BEV_LOCK(bev);
+
+	if (bufev_private->rate_limiting) {
+		cfg = bufev_private->rate_limiting->cfg;
+	} else {
+		cfg = NULL;
+	}
+
+	BEV_UNLOCK(bev);
+
+	return cfg;
+}
+
+/* Mostly you don't want to use this function from inside libevent;
+ * bufferevent_get_read_max_() is more likely what you want*/
+ev_ssize_t
+bufferevent_rate_limit_group_get_read_limit(
+	struct bufferevent_rate_limit_group *grp)
+{
+	ev_ssize_t r;
+	LOCK_GROUP(grp);
+	r = grp->rate_limit.read_limit;
+	UNLOCK_GROUP(grp);
+	return r;
+}
+
+/* Mostly you don't want to use this function from inside libevent;
+ * bufferevent_get_write_max_() is more likely what you want. */
+ev_ssize_t
+bufferevent_rate_limit_group_get_write_limit(
+	struct bufferevent_rate_limit_group *grp)
+{
+	ev_ssize_t r;
+	LOCK_GROUP(grp);
+	r = grp->rate_limit.write_limit;
+	UNLOCK_GROUP(grp);
+	return r;
+}
+
+int
+bufferevent_decrement_read_limit(struct bufferevent *bev, ev_ssize_t decr)
+{
+	int r = 0;
+	ev_ssize_t old_limit, new_limit;
+	struct bufferevent_private *bevp;
+	BEV_LOCK(bev);
+	bevp = BEV_UPCAST(bev);
+	EVUTIL_ASSERT(bevp->rate_limiting && bevp->rate_limiting->cfg);
+	old_limit = bevp->rate_limiting->limit.read_limit;
+
+	new_limit = (bevp->rate_limiting->limit.read_limit -= decr);
+	if (old_limit > 0 && new_limit <= 0) {
+		bufferevent_suspend_read_(bev, BEV_SUSPEND_BW);
+		if (event_add(&bevp->rate_limiting->refill_bucket_event,
+			&bevp->rate_limiting->cfg->tick_timeout) < 0)
+			r = -1;
+	} else if (old_limit <= 0 && new_limit > 0) {
+		if (!(bevp->write_suspended & BEV_SUSPEND_BW))
+			event_del(&bevp->rate_limiting->refill_bucket_event);
+		bufferevent_unsuspend_read_(bev, BEV_SUSPEND_BW);
+	}
+
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+int
+bufferevent_decrement_write_limit(struct bufferevent *bev, ev_ssize_t decr)
+{
+	/* XXXX this is mostly copy-and-paste from
+	 * bufferevent_decrement_read_limit */
+	int r = 0;
+	ev_ssize_t old_limit, new_limit;
+	struct bufferevent_private *bevp;
+	BEV_LOCK(bev);
+	bevp = BEV_UPCAST(bev);
+	EVUTIL_ASSERT(bevp->rate_limiting && bevp->rate_limiting->cfg);
+	old_limit = bevp->rate_limiting->limit.write_limit;
+
+	new_limit = (bevp->rate_limiting->limit.write_limit -= decr);
+	if (old_limit > 0 && new_limit <= 0) {
+		bufferevent_suspend_write_(bev, BEV_SUSPEND_BW);
+		if (event_add(&bevp->rate_limiting->refill_bucket_event,
+			&bevp->rate_limiting->cfg->tick_timeout) < 0)
+			r = -1;
+	} else if (old_limit <= 0 && new_limit > 0) {
+		if (!(bevp->read_suspended & BEV_SUSPEND_BW))
+			event_del(&bevp->rate_limiting->refill_bucket_event);
+		bufferevent_unsuspend_write_(bev, BEV_SUSPEND_BW);
+	}
+
+	BEV_UNLOCK(bev);
+	return r;
+}
+
+int
+bufferevent_rate_limit_group_decrement_read(
+	struct bufferevent_rate_limit_group *grp, ev_ssize_t decr)
+{
+	int r = 0;
+	ev_ssize_t old_limit, new_limit;
+	LOCK_GROUP(grp);
+	old_limit = grp->rate_limit.read_limit;
+	new_limit = (grp->rate_limit.read_limit -= decr);
+
+	if (old_limit > 0 && new_limit <= 0) {
+		bev_group_suspend_reading_(grp);
+	} else if (old_limit <= 0 && new_limit > 0) {
+		bev_group_unsuspend_reading_(grp);
+	}
+
+	UNLOCK_GROUP(grp);
+	return r;
+}
+
+int
+bufferevent_rate_limit_group_decrement_write(
+	struct bufferevent_rate_limit_group *grp, ev_ssize_t decr)
+{
+	int r = 0;
+	ev_ssize_t old_limit, new_limit;
+	LOCK_GROUP(grp);
+	old_limit = grp->rate_limit.write_limit;
+	new_limit = (grp->rate_limit.write_limit -= decr);
+
+	if (old_limit > 0 && new_limit <= 0) {
+		bev_group_suspend_writing_(grp);
+	} else if (old_limit <= 0 && new_limit > 0) {
+		bev_group_unsuspend_writing_(grp);
+	}
+
+	UNLOCK_GROUP(grp);
+	return r;
+}
+
+void
+bufferevent_rate_limit_group_get_totals(struct bufferevent_rate_limit_group *grp,
+    ev_uint64_t *total_read_out, ev_uint64_t *total_written_out)
+{
+	EVUTIL_ASSERT(grp != NULL);
+	if (total_read_out)
+		*total_read_out = grp->total_read;
+	if (total_written_out)
+		*total_written_out = grp->total_written;
+}
+
+void
+bufferevent_rate_limit_group_reset_totals(struct bufferevent_rate_limit_group *grp)
+{
+	grp->total_read = grp->total_written = 0;
+}
+
+int
+bufferevent_ratelim_init_(struct bufferevent_private *bev)
+{
+	bev->rate_limiting = NULL;
+	bev->max_single_read = MAX_SINGLE_READ_DEFAULT;
+	bev->max_single_write = MAX_SINGLE_WRITE_DEFAULT;
+
+	return 0;
+}