cache.c

非常好的dns解析软件

/*
 * Copyright (C) 2004-2006  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: cache.c,v 1.57.18.16 2006/08/01 01:06:48 marka Exp $ */

/*! \file */

#include <config.h>

#include <isc/mem.h>
#include <isc/task.h>
#include <isc/time.h>
#include <isc/timer.h>
#include <isc/util.h>

#include <dns/cache.h>
#include <dns/db.h>
#include <dns/dbiterator.h>
#include <dns/events.h>
#include <dns/lib.h>
#include <dns/log.h>
#include <dns/masterdump.h>
#include <dns/rdata.h>
#include <dns/rdataset.h>
#include <dns/rdatasetiter.h>
#include <dns/result.h>

#define CACHE_MAGIC		ISC_MAGIC('$', '$', '$', '$')
#define VALID_CACHE(cache)	ISC_MAGIC_VALID(cache, CACHE_MAGIC)

/*! 
 * Control incremental cleaning.
 * DNS_CACHE_MINSIZE is how many bytes is the floor for dns_cache_setcachesize().
 * See also DNS_CACHE_CLEANERINCREMENT
 */
#define DNS_CACHE_MINSIZE 		2097152	/*%< Bytes.  2097152 = 2 MB */
/*! 
 * Control incremental cleaning.
 * CLEANERINCREMENT is how many nodes are examined in one pass.
 * See also DNS_CACHE_MINSIZE 
 */
#define DNS_CACHE_CLEANERINCREMENT	1000U	/*%< Number of nodes. */

/***
 ***	Types
 ***/

/*
 * A cache_cleaner_t encapsulsates the state of the periodic
 * cache cleaning.
 */

typedef struct cache_cleaner cache_cleaner_t;

typedef enum {
	cleaner_s_idle,	/*%< Waiting for cleaning-interval to expire. */
	cleaner_s_busy,	/*%< Currently cleaning. */
	cleaner_s_done  /*%< Freed enough memory after being overmem. */
} cleaner_state_t;

/*
 * Convenience macros for comprehensive assertion checking.
 */
#define CLEANER_IDLE(c) ((c)->state == cleaner_s_idle && \
			 (c)->resched_event != NULL)
#define CLEANER_BUSY(c) ((c)->state == cleaner_s_busy && \
			 (c)->iterator != NULL && \
			 (c)->resched_event == NULL)

/*%
 * Accesses to a cache cleaner object are synchronized through
 * task/event serialization, or locked from the cache object.
 */
struct cache_cleaner {
	isc_mutex_t	lock;
	/*%<
	 * Locks overmem_event, overmem.  Note: never allocate memory
	 * while holding this lock - that could lead to deadlock since
	 * the lock is take by water() which is called from the memory
	 * allocator.
	 */

	dns_cache_t	*cache;
	isc_task_t 	*task;
	unsigned int	cleaning_interval; /*% The cleaning-interval from
					      named.conf, in seconds. */
	isc_timer_t 	*cleaning_timer;
	isc_event_t	*resched_event;	/*% Sent by cleaner task to
					   itself to reschedule */
	isc_event_t	*overmem_event;

	dns_dbiterator_t *iterator;
	unsigned int 	 increment;	/*% Number of names to
					   clean in one increment */
	cleaner_state_t  state;		/*% Idle/Busy. */
	isc_boolean_t	 overmem;	/*% The cache is in an overmem state. */
	isc_boolean_t	 replaceiterator;
};

/*%
 * The actual cache object.
 */

struct dns_cache {
	/* Unlocked. */
	unsigned int		magic;
	isc_mutex_t		lock;
	isc_mutex_t		filelock;
	isc_mem_t		*mctx;

	/* Locked by 'lock'. */
	int			references;
	int			live_tasks;
	dns_rdataclass_t	rdclass;
	dns_db_t		*db;
	cache_cleaner_t		cleaner;
	char			*db_type;
	int			db_argc;
	char			**db_argv;

	/* Locked by 'filelock'. */
	char *			filename;
	/* Access to the on-disk cache file is also locked by 'filelock'. */
};

/***
 ***	Functions
 ***/

static isc_result_t
cache_cleaner_init(dns_cache_t *cache, isc_taskmgr_t *taskmgr,
		   isc_timermgr_t *timermgr, cache_cleaner_t *cleaner);

static void
cleaning_timer_action(isc_task_t *task, isc_event_t *event);

static void
incremental_cleaning_action(isc_task_t *task, isc_event_t *event);

static void
cleaner_shutdown_action(isc_task_t *task, isc_event_t *event);

static void
overmem_cleaning_action(isc_task_t *task, isc_event_t *event);

/*%
 * Work out how many nodes can be cleaned in the time between two
 * requests to the nameserver.  Smooth the resulting number and use
 * it as a estimate for the number of nodes to be cleaned in the next
 * iteration.
 */
static void
adjust_increment(cache_cleaner_t *cleaner, unsigned int remaining,
		 isc_time_t *start)
{
	isc_time_t end;
	isc_uint64_t usecs;
	isc_uint64_t new;
	unsigned int pps = dns_pps;
	unsigned int interval;
	unsigned int names;
	
	/*
	 * Tune for minumum of 100 packets per second (pps).
	 */
	if (pps < 100)
		pps = 100;

	isc_time_now(&end);

	interval = 1000000 / pps; /* Interval between packets in usecs. */
	if (interval == 0)
		interval = 1;

	INSIST(cleaner->increment >= remaining);
	names = cleaner->increment - remaining;
	usecs = isc_time_microdiff(&end, start);

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_CACHE,
		      ISC_LOG_DEBUG(1), "adjust_increment interval=%u "
		      "names=%u usec=%" ISC_PLATFORM_QUADFORMAT "u",
		      interval, names, usecs);
	
	if (usecs == 0) {
		/*
		 * If we cleaned all the nodes in unmeasurable time
		 * double the number of nodes to be cleaned next time.
		 */
		if (names == cleaner->increment) {
			cleaner->increment *= 2;
			if (cleaner->increment > DNS_CACHE_CLEANERINCREMENT)
				cleaner->increment = DNS_CACHE_CLEANERINCREMENT;
			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
				      DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
				      "%p:new cleaner->increment = %u\n",
				      cleaner, cleaner->increment);
		}
		return;
	}

	new = (names * interval);
	new /= (usecs * 2);
	if (new == 0)
		new = 1;

	/* Smooth */
	new = (new + cleaner->increment * 7) / 8;

	if (new > DNS_CACHE_CLEANERINCREMENT)
		new = DNS_CACHE_CLEANERINCREMENT;

	cleaner->increment = (unsigned int)new;

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_CACHE,
		      ISC_LOG_DEBUG(1), "%p:new cleaner->increment = %u\n",
		      cleaner, cleaner->increment);
}

static inline isc_result_t
cache_create_db(dns_cache_t *cache, dns_db_t **db) {
	return (dns_db_create(cache->mctx, cache->db_type, dns_rootname,
			      dns_dbtype_cache, cache->rdclass,
			      cache->db_argc, cache->db_argv, db));
}

isc_result_t
dns_cache_create(isc_mem_t *mctx, isc_taskmgr_t *taskmgr,
		 isc_timermgr_t *timermgr, dns_rdataclass_t rdclass,
		 const char *db_type, unsigned int db_argc, char **db_argv,
		 dns_cache_t **cachep)
{
	isc_result_t result;
	dns_cache_t *cache;
	int i;

	REQUIRE(cachep != NULL);
	REQUIRE(*cachep == NULL);
	REQUIRE(mctx != NULL);

	cache = isc_mem_get(mctx, sizeof(*cache));
	if (cache == NULL)
		return (ISC_R_NOMEMORY);

	cache->mctx = NULL;
	isc_mem_attach(mctx, &cache->mctx);

	result = isc_mutex_init(&cache->lock);
	if (result != ISC_R_SUCCESS)
		goto cleanup_mem;

	result = isc_mutex_init(&cache->filelock);
	if (result != ISC_R_SUCCESS)
		goto cleanup_lock;

	cache->references = 1;
	cache->live_tasks = 0;
	cache->rdclass = rdclass;

	cache->db_type = isc_mem_strdup(mctx, db_type);
	if (cache->db_type == NULL) {
		result = ISC_R_NOMEMORY;
		goto cleanup_filelock;
	}

	cache->db_argc = db_argc;
	if (cache->db_argc == 0)
		cache->db_argv = NULL;
	else {
		cache->db_argv = isc_mem_get(mctx,
					     cache->db_argc * sizeof(char *));
		if (cache->db_argv == NULL) {
			result = ISC_R_NOMEMORY;
			goto cleanup_dbtype;
		}
		for (i = 0; i < cache->db_argc; i++)
			cache->db_argv[i] = NULL;
		for (i = 0; i < cache->db_argc; i++) {
			cache->db_argv[i] = isc_mem_strdup(mctx, db_argv[i]);
			if (cache->db_argv[i] == NULL) {
				result = ISC_R_NOMEMORY;
				goto cleanup_dbargv;
			}
		}
	}

	cache->db = NULL;
	result = cache_create_db(cache, &cache->db);
	if (result != ISC_R_SUCCESS)
		goto cleanup_dbargv;

	cache->filename = NULL;

	cache->magic = CACHE_MAGIC;

	result = cache_cleaner_init(cache, taskmgr, timermgr, &cache->cleaner);
	if (result != ISC_R_SUCCESS)
		goto cleanup_db;

	*cachep = cache;
	return (ISC_R_SUCCESS);

 cleanup_db:
	dns_db_detach(&cache->db);
 cleanup_dbargv:
	for (i = 0; i < cache->db_argc; i++)
		if (cache->db_argv[i] != NULL)
			isc_mem_free(mctx, cache->db_argv[i]);
	if (cache->db_argv != NULL)
		isc_mem_put(mctx, cache->db_argv,
			    cache->db_argc * sizeof(char *));
 cleanup_dbtype:
	isc_mem_free(mctx, cache->db_type);
 cleanup_filelock:
	DESTROYLOCK(&cache->filelock);
 cleanup_lock:
	DESTROYLOCK(&cache->lock);
 cleanup_mem:
	isc_mem_put(mctx, cache, sizeof(*cache));
	isc_mem_detach(&mctx);
	return (result);
}

static void
cache_free(dns_cache_t *cache) {
	isc_mem_t *mctx;
	int i;

	REQUIRE(VALID_CACHE(cache));
	REQUIRE(cache->references == 0);

	isc_mem_setwater(cache->mctx, NULL, NULL, 0, 0);

	if (cache->cleaner.task != NULL)
		isc_task_detach(&cache->cleaner.task);

	if (cache->cleaner.overmem_event != NULL)
		isc_event_free(&cache->cleaner.overmem_event);

	if (cache->cleaner.resched_event != NULL)
		isc_event_free(&cache->cleaner.resched_event);

	if (cache->cleaner.iterator != NULL)
		dns_dbiterator_destroy(&cache->cleaner.iterator);

	DESTROYLOCK(&cache->cleaner.lock);

	if (cache->filename) {
		isc_mem_free(cache->mctx, cache->filename);
		cache->filename = NULL;
	}

	if (cache->db != NULL)
		dns_db_detach(&cache->db);

	if (cache->db_argv != NULL) {
		for (i = 0; i < cache->db_argc; i++)
			if (cache->db_argv[i] != NULL)
				isc_mem_free(cache->mctx, cache->db_argv[i]);
		isc_mem_put(cache->mctx, cache->db_argv,
			    cache->db_argc * sizeof(char *));
	}

	if (cache->db_type != NULL)
		isc_mem_free(cache->mctx, cache->db_type);

	DESTROYLOCK(&cache->lock);
	DESTROYLOCK(&cache->filelock);
	cache->magic = 0;
	mctx = cache->mctx;
	isc_mem_put(cache->mctx, cache, sizeof(*cache));
	isc_mem_detach(&mctx);
}


void
dns_cache_attach(dns_cache_t *cache, dns_cache_t **targetp) {

	REQUIRE(VALID_CACHE(cache));
	REQUIRE(targetp != NULL && *targetp == NULL);

	LOCK(&cache->lock);
	cache->references++;
	UNLOCK(&cache->lock);

	*targetp = cache;
}

void
dns_cache_detach(dns_cache_t **cachep) {
	dns_cache_t *cache;
	isc_boolean_t free_cache = ISC_FALSE;

	REQUIRE(cachep != NULL);
	cache = *cachep;
	REQUIRE(VALID_CACHE(cache));

	LOCK(&cache->lock);
	REQUIRE(cache->references > 0);
	cache->references--;
	if (cache->references == 0) {
		cache->cleaner.overmem = ISC_FALSE;
		free_cache = ISC_TRUE;
	}

	*cachep = NULL;

	if (free_cache) {
		/*
		 * When the cache is shut down, dump it to a file if one is
		 * specified.
		 */
		isc_result_t result = dns_cache_dump(cache);
		if (result != ISC_R_SUCCESS)
			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
				      DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
				      "error dumping cache: %s ",
				      isc_result_totext(result));

		/*
		 * If the cleaner task exists, let it free the cache.
		 */
		if (cache->live_tasks > 0) {
			isc_task_shutdown(cache->cleaner.task);
			free_cache = ISC_FALSE;
		}
	}

	UNLOCK(&cache->lock);

	if (free_cache)
		cache_free(cache);
}

void
dns_cache_attachdb(dns_cache_t *cache, dns_db_t **dbp) {
	REQUIRE(VALID_CACHE(cache));
	REQUIRE(dbp != NULL && *dbp == NULL);
	REQUIRE(cache->db != NULL);

	LOCK(&cache->lock);
	dns_db_attach(cache->db, dbp);
	UNLOCK(&cache->lock);

}

isc_result_t
dns_cache_setfilename(dns_cache_t *cache, const char *filename) {
	char *newname;

	REQUIRE(VALID_CACHE(cache));
	REQUIRE(filename != NULL);

	newname = isc_mem_strdup(cache->mctx, filename);
	if (newname == NULL)
		return (ISC_R_NOMEMORY);

	LOCK(&cache->filelock);
	if (cache->filename)
		isc_mem_free(cache->mctx, cache->filename);
	cache->filename = newname;
	UNLOCK(&cache->filelock);

	return (ISC_R_SUCCESS);
}

isc_result_t
dns_cache_load(dns_cache_t *cache) {
	isc_result_t result;

	REQUIRE(VALID_CACHE(cache));

	if (cache->filename == NULL)
		return (ISC_R_SUCCESS);

	LOCK(&cache->filelock);
	result = dns_db_load(cache->db, cache->filename);
	UNLOCK(&cache->filelock);

	return (result);
}

isc_result_t
dns_cache_dump(dns_cache_t *cache) {
	isc_result_t result;

	REQUIRE(VALID_CACHE(cache));

	if (cache->filename == NULL)
		return (ISC_R_SUCCESS);

	LOCK(&cache->filelock);
	result = dns_master_dump(cache->mctx, cache->db, NULL,
				 &dns_master_style_cache, cache->filename);
	UNLOCK(&cache->filelock);

	return (result);
}

void
dns_cache_setcleaninginterval(dns_cache_t *cache, unsigned int t) {
	isc_interval_t interval;
	isc_result_t result;

	LOCK(&cache->lock);

	/*
	 * It may be the case that the cache has already shut down.
	 * If so, it has no timer.
	 */
	if (cache->cleaner.cleaning_timer == NULL)
		goto unlock;

	cache->cleaner.cleaning_interval = t;

	if (t == 0) {
		result = isc_timer_reset(cache->cleaner.cleaning_timer,
					 isc_timertype_inactive,
					 NULL, NULL, ISC_TRUE);
	} else {
		isc_interval_set(&interval, cache->cleaner.cleaning_interval,
				 0);
		result = isc_timer_reset(cache->cleaner.cleaning_timer,
					 isc_timertype_ticker,
					 NULL, &interval, ISC_FALSE);
	}
	if (result != ISC_R_SUCCESS)	
		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
			      DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
			      "could not set cache cleaning interval: %s",
			      isc_result_totext(result));

 unlock:
	UNLOCK(&cache->lock);
}

/*
 * Initialize the cache cleaner object at *cleaner.
 * Space for the object must be allocated by the caller.
 */

static isc_result_t
cache_cleaner_init(dns_cache_t *cache, isc_taskmgr_t *taskmgr,
		   isc_timermgr_t *timermgr, cache_cleaner_t *cleaner)
{
	isc_result_t result;

	result = isc_mutex_init(&cleaner->lock);
	if (result != ISC_R_SUCCESS)
		goto fail;

	cleaner->increment = DNS_CACHE_CLEANERINCREMENT;
	cleaner->state = cleaner_s_idle;
	cleaner->cache = cache;
	cleaner->iterator = NULL;
	cleaner->overmem = ISC_FALSE;
	cleaner->replaceiterator = ISC_FALSE;

	cleaner->task = NULL;
	cleaner->cleaning_timer = NULL;
	cleaner->resched_event = NULL;
	cleaner->overmem_event = NULL;

	result = dns_db_createiterator(cleaner->cache->db, ISC_FALSE,
				       &cleaner->iterator);