/* * Copyright (C) Internet Systems Consortium, Inc. ("ISC") * * 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. */ #ifndef ISC_QUOTA_H #define ISC_QUOTA_H 1 /***** ***** Module Info *****/ /*! \file isc/quota.h * * \brief The isc_quota_t object is a simple helper object for implementing * quotas on things like the number of simultaneous connections to * a server. It keeps track of the amount of quota in use, and * encapsulates the locking necessary to allow multiple tasks to * share a quota. */ /*** *** Imports. ***/ #include <isc/atomic.h> #include <isc/lang.h> #include <isc/magic.h> #include <isc/mutex.h> #include <isc/types.h> /***** ***** Types. *****/ ISC_LANG_BEGINDECLS /*% isc_quota_cb - quota callback structure */ typedef struct isc_quota_cb isc_quota_cb_t; typedef void (*isc_quota_cb_func_t)(isc_quota_t *quota, void *data); struct isc_quota_cb { int magic; isc_quota_cb_func_t cb_func; void *data; ISC_LINK(isc_quota_cb_t) link; }; /*% isc_quota structure */ struct isc_quota { int magic; atomic_uint_fast32_t max; atomic_uint_fast32_t used; atomic_uint_fast32_t soft; atomic_uint_fast32_t waiting; isc_mutex_t cblock; ISC_LIST(isc_quota_cb_t) cbs; }; void isc_quota_init(isc_quota_t *quota, unsigned int max); /*%< * Initialize a quota object. */ void isc_quota_destroy(isc_quota_t *quota); /*%< * Destroy a quota object. */ void isc_quota_soft(isc_quota_t *quota, unsigned int soft); /*%< * Set a soft quota. */ void isc_quota_max(isc_quota_t *quota, unsigned int max); /*%< * Re-set a maximum quota. */ unsigned int isc_quota_getmax(isc_quota_t *quota); /*%< * Get the maximum quota. */ unsigned int isc_quota_getsoft(isc_quota_t *quota); /*%< * Get the soft quota. */ unsigned int isc_quota_getused(isc_quota_t *quota); /*%< * Get the current usage of quota. */ isc_result_t isc_quota_attach(isc_quota_t *quota, isc_quota_t **p); /*%< * * Attempt to reserve one unit of 'quota', and also attaches '*p' to the quota * if successful (ISC_R_SUCCESS or ISC_R_SOFTQUOTA). * * Returns: * \li #ISC_R_SUCCESS Success * \li #ISC_R_SOFTQUOTA Success soft quota reached * \li #ISC_R_QUOTA Quota is full */ isc_result_t isc_quota_attach_cb(isc_quota_t *quota, isc_quota_t **p, isc_quota_cb_t *cb); /*%< * * Like isc_quota_attach(), but if there's no quota left then cb->cb_func will * be called when we are attached to quota. * * Note: It's the caller's responsibility to make sure that we don't end up * with a huge number of callbacks waiting, making it easy to create a * resource exhaustion attack. For example, in the case of TCP listening, * we simply don't accept new connections when the quota is exceeded, so * the number of callbacks waiting in the queue will be limited by the * listen() backlog. * * Returns: * \li #ISC_R_SUCCESS Success * \li #ISC_R_SOFTQUOTA Success soft quota reached * \li #ISC_R_QUOTA Quota is full */ void isc_quota_cb_init(isc_quota_cb_t *cb, isc_quota_cb_func_t cb_func, void *data); /*%< * Initialize isc_quota_cb_t - setup the list, set the callback and data. */ void isc_quota_detach(isc_quota_t **p); /*%< * Release one unit of quota, and also detaches '*p' from the quota. */ ISC_LANG_ENDDECLS #endif /* ISC_QUOTA_H */