1 files changed, 372 insertions, 0 deletions
diff --git a/lib/isc/ratelimiter.c b/lib/isc/ratelimiter.c
new file mode 100644
index 0000000..84a848a
--- /dev/null
+++ b/lib/isc/ratelimiter.c
@@ -0,0 +1,372 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*! \file */
+
+#include <inttypes.h>
+#include <stdbool.h>
+
+#include <isc/mem.h>
+#include <isc/ratelimiter.h>
+#include <isc/refcount.h>
+#include <isc/task.h>
+#include <isc/time.h>
+#include <isc/timer.h>
+#include <isc/util.h>
+
+typedef enum {
+	isc_ratelimiter_stalled = 0,
+	isc_ratelimiter_ratelimited = 1,
+	isc_ratelimiter_idle = 2,
+	isc_ratelimiter_shuttingdown = 3
+} isc_ratelimiter_state_t;
+
+struct isc_ratelimiter {
+	isc_mem_t *mctx;
+	isc_mutex_t lock;
+	isc_refcount_t references;
+	isc_task_t *task;
+	isc_timer_t *timer;
+	isc_interval_t interval;
+	uint32_t pertic;
+	bool pushpop;
+	isc_ratelimiter_state_t state;
+	isc_event_t shutdownevent;
+	ISC_LIST(isc_event_t) pending;
+};
+
+#define ISC_RATELIMITEREVENT_SHUTDOWN (ISC_EVENTCLASS_RATELIMITER + 1)
+
+static void
+ratelimiter_tick(isc_task_t *task, isc_event_t *event);
+
+static void
+ratelimiter_shutdowncomplete(isc_task_t *task, isc_event_t *event);
+
+isc_result_t
+isc_ratelimiter_create(isc_mem_t *mctx, isc_timermgr_t *timermgr,
+		       isc_task_t *task, isc_ratelimiter_t **ratelimiterp) {
+	isc_result_t result;
+	isc_ratelimiter_t *rl;
+	INSIST(ratelimiterp != NULL && *ratelimiterp == NULL);
+
+	rl = isc_mem_get(mctx, sizeof(*rl));
+	*rl = (isc_ratelimiter_t){
+		.mctx = mctx,
+		.task = task,
+		.pertic = 1,
+		.state = isc_ratelimiter_idle,
+	};
+
+	isc_refcount_init(&rl->references, 1);
+	isc_interval_set(&rl->interval, 0, 0);
+	ISC_LIST_INIT(rl->pending);
+
+	isc_mutex_init(&rl->lock);
+
+	result = isc_timer_create(timermgr, isc_timertype_inactive, NULL, NULL,
+				  rl->task, ratelimiter_tick, rl, &rl->timer);
+	if (result != ISC_R_SUCCESS) {
+		goto free_mutex;
+	}
+
+	/*
+	 * Increment the reference count to indicate that we may
+	 * (soon) have events outstanding.
+	 */
+	isc_refcount_increment(&rl->references);
+
+	ISC_EVENT_INIT(&rl->shutdownevent, sizeof(isc_event_t), 0, NULL,
+		       ISC_RATELIMITEREVENT_SHUTDOWN,
+		       ratelimiter_shutdowncomplete, rl, rl, NULL, NULL);
+
+	*ratelimiterp = rl;
+	return (ISC_R_SUCCESS);
+
+free_mutex:
+	isc_refcount_decrementz(&rl->references);
+	isc_refcount_destroy(&rl->references);
+	isc_mutex_destroy(&rl->lock);
+	isc_mem_put(mctx, rl, sizeof(*rl));
+	return (result);
+}
+
+isc_result_t
+isc_ratelimiter_setinterval(isc_ratelimiter_t *rl, isc_interval_t *interval) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(rl != NULL);
+	REQUIRE(interval != NULL);
+
+	LOCK(&rl->lock);
+	rl->interval = *interval;
+	/*
+	 * If the timer is currently running, change its rate.
+	 */
+	if (rl->state == isc_ratelimiter_ratelimited) {
+		result = isc_timer_reset(rl->timer, isc_timertype_ticker, NULL,
+					 &rl->interval, false);
+	}
+	UNLOCK(&rl->lock);
+	return (result);
+}
+
+void
+isc_ratelimiter_setpertic(isc_ratelimiter_t *rl, uint32_t pertic) {
+	REQUIRE(rl != NULL);
+
+	if (pertic == 0) {
+		pertic = 1;
+	}
+	rl->pertic = pertic;
+}
+
+void
+isc_ratelimiter_setpushpop(isc_ratelimiter_t *rl, bool pushpop) {
+	REQUIRE(rl != NULL);
+
+	rl->pushpop = pushpop;
+}
+
+isc_result_t
+isc_ratelimiter_enqueue(isc_ratelimiter_t *rl, isc_task_t *task,
+			isc_event_t **eventp) {
+	isc_result_t result = ISC_R_SUCCESS;
+	isc_event_t *ev;
+
+	REQUIRE(rl != NULL);
+	REQUIRE(task != NULL);
+	REQUIRE(eventp != NULL && *eventp != NULL);
+	ev = *eventp;
+	REQUIRE(ev->ev_sender == NULL);
+
+	LOCK(&rl->lock);
+	if (rl->state == isc_ratelimiter_ratelimited ||
+	    rl->state == isc_ratelimiter_stalled)
+	{
+		ev->ev_sender = task;
+		*eventp = NULL;
+		if (rl->pushpop) {
+			ISC_LIST_PREPEND(rl->pending, ev, ev_ratelink);
+		} else {
+			ISC_LIST_APPEND(rl->pending, ev, ev_ratelink);
+		}
+	} else if (rl->state == isc_ratelimiter_idle) {
+		result = isc_timer_reset(rl->timer, isc_timertype_ticker, NULL,
+					 &rl->interval, false);
+		if (result == ISC_R_SUCCESS) {
+			ev->ev_sender = task;
+			rl->state = isc_ratelimiter_ratelimited;
+		}
+	} else {
+		INSIST(rl->state == isc_ratelimiter_shuttingdown);
+		result = ISC_R_SHUTTINGDOWN;
+	}
+	UNLOCK(&rl->lock);
+	if (*eventp != NULL && result == ISC_R_SUCCESS) {
+		isc_task_send(task, eventp);
+	}
+	return (result);
+}
+
+isc_result_t
+isc_ratelimiter_dequeue(isc_ratelimiter_t *rl, isc_event_t *event) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(rl != NULL);
+	REQUIRE(event != NULL);
+
+	LOCK(&rl->lock);
+	if (ISC_LINK_LINKED(event, ev_ratelink)) {
+		ISC_LIST_UNLINK(rl->pending, event, ev_ratelink);
+		event->ev_sender = NULL;
+	} else {
+		result = ISC_R_NOTFOUND;
+	}
+	UNLOCK(&rl->lock);
+	return (result);
+}
+
+static void
+ratelimiter_tick(isc_task_t *task, isc_event_t *event) {
+	isc_ratelimiter_t *rl = (isc_ratelimiter_t *)event->ev_arg;
+	isc_event_t *p;
+	uint32_t pertic;
+
+	UNUSED(task);
+
+	isc_event_free(&event);
+
+	pertic = rl->pertic;
+	while (pertic != 0) {
+		pertic--;
+		LOCK(&rl->lock);
+		p = ISC_LIST_HEAD(rl->pending);
+		if (p != NULL) {
+			/*
+			 * There is work to do.  Let's do it after unlocking.
+			 */
+			ISC_LIST_UNLINK(rl->pending, p, ev_ratelink);
+		} else {
+			/*
+			 * No work left to do.  Stop the timer so that we don't
+			 * waste resources by having it fire periodically.
+			 */
+			isc_result_t result = isc_timer_reset(
+				rl->timer, isc_timertype_inactive, NULL, NULL,
+				false);
+			RUNTIME_CHECK(result == ISC_R_SUCCESS);
+			rl->state = isc_ratelimiter_idle;
+			pertic = 0; /* Force the loop to exit. */
+		}
+		UNLOCK(&rl->lock);
+		if (p != NULL) {
+			isc_task_t *evtask = p->ev_sender;
+			isc_task_send(evtask, &p);
+		}
+		INSIST(p == NULL);
+	}
+}
+
+void
+isc_ratelimiter_shutdown(isc_ratelimiter_t *rl) {
+	isc_event_t *ev;
+	isc_task_t *task;
+	isc_result_t result;
+
+	REQUIRE(rl != NULL);
+
+	LOCK(&rl->lock);
+	rl->state = isc_ratelimiter_shuttingdown;
+	(void)isc_timer_reset(rl->timer, isc_timertype_inactive, NULL, NULL,
+			      false);
+	while ((ev = ISC_LIST_HEAD(rl->pending)) != NULL) {
+		task = ev->ev_sender;
+		ISC_LIST_UNLINK(rl->pending, ev, ev_ratelink);
+		ev->ev_attributes |= ISC_EVENTATTR_CANCELED;
+		isc_task_send(task, &ev);
+	}
+	task = NULL;
+	isc_task_attach(rl->task, &task);
+
+	result = isc_timer_reset(rl->timer, isc_timertype_inactive, NULL, NULL,
+				 true);
+	RUNTIME_CHECK(result == ISC_R_SUCCESS);
+	isc_timer_destroy(&rl->timer);
+
+	/*
+	 * Send an event to our task.  The delivery of this event
+	 * indicates that no more timer events will be delivered.
+	 */
+	ev = &rl->shutdownevent;
+	isc_task_send(rl->task, &ev);
+
+	UNLOCK(&rl->lock);
+}
+
+static void
+ratelimiter_shutdowncomplete(isc_task_t *task, isc_event_t *event) {
+	isc_ratelimiter_t *rl = (isc_ratelimiter_t *)event->ev_arg;
+
+	UNUSED(task);
+
+	isc_ratelimiter_detach(&rl);
+	isc_task_detach(&task);
+}
+
+static void
+ratelimiter_free(isc_ratelimiter_t *rl) {
+	isc_refcount_destroy(&rl->references);
+	isc_mutex_destroy(&rl->lock);
+	isc_mem_put(rl->mctx, rl, sizeof(*rl));
+}
+
+void
+isc_ratelimiter_attach(isc_ratelimiter_t *source, isc_ratelimiter_t **target) {
+	REQUIRE(source != NULL);
+	REQUIRE(target != NULL && *target == NULL);
+
+	isc_refcount_increment(&source->references);
+
+	*target = source;
+}
+
+void
+isc_ratelimiter_detach(isc_ratelimiter_t **rlp) {
+	isc_ratelimiter_t *rl;
+
+	REQUIRE(rlp != NULL && *rlp != NULL);
+
+	rl = *rlp;
+	*rlp = NULL;
+
+	if (isc_refcount_decrement(&rl->references) == 1) {
+		ratelimiter_free(rl);
+	}
+}
+
+isc_result_t
+isc_ratelimiter_stall(isc_ratelimiter_t *rl) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(rl != NULL);
+
+	LOCK(&rl->lock);
+	switch (rl->state) {
+	case isc_ratelimiter_shuttingdown:
+		result = ISC_R_SHUTTINGDOWN;
+		break;
+	case isc_ratelimiter_ratelimited:
+		result = isc_timer_reset(rl->timer, isc_timertype_inactive,
+					 NULL, NULL, false);
+		RUNTIME_CHECK(result == ISC_R_SUCCESS);
+		FALLTHROUGH;
+	case isc_ratelimiter_idle:
+	case isc_ratelimiter_stalled:
+		rl->state = isc_ratelimiter_stalled;
+		break;
+	}
+	UNLOCK(&rl->lock);
+	return (result);
+}
+
+isc_result_t
+isc_ratelimiter_release(isc_ratelimiter_t *rl) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(rl != NULL);
+
+	LOCK(&rl->lock);
+	switch (rl->state) {
+	case isc_ratelimiter_shuttingdown:
+		result = ISC_R_SHUTTINGDOWN;
+		break;
+	case isc_ratelimiter_stalled:
+		if (!ISC_LIST_EMPTY(rl->pending)) {
+			result = isc_timer_reset(rl->timer,
+						 isc_timertype_ticker, NULL,
+						 &rl->interval, false);
+			if (result == ISC_R_SUCCESS) {
+				rl->state = isc_ratelimiter_ratelimited;
+			}
+		} else {
+			rl->state = isc_ratelimiter_idle;
+		}
+		break;
+	case isc_ratelimiter_ratelimited:
+	case isc_ratelimiter_idle:
+		break;
+	}
+	UNLOCK(&rl->lock);
+	return (result);
+}