get rid of isc_random_t -- use a wrapper around rand() instead that doesn't do as much work. Also, implement isc_random_jitter(), used to generate a value between a min, max, with a provided jitter value.

2025-08-31 06:25:31 +00:00 · 2000-09-06 02:40:00 +00:00
parent 16803617e4
commit 7da0286b54
5 changed files with 46 additions and 123 deletions
--- a/6
+++ b/6
@@ -1,4 +1,10 @@

+ 422.	[func]		get rid of isc_random_t, and make isc_random_get()
+			and isc_random_jitter() use rand() internally
+			instead of local state.  Note that isc_random_*()
+			functions are only for weak, non-critical "randomness"
+			such as timing jitter and such.
+
 421.	[bug]		nslookup would exit when given a blank line as input.

 420.	[bug]		nslookup failed to implement the "exit" command.
--- a/lib/dns/adb.c
+++ b/lib/dns/adb.c
@@ -15,7 +15,7 @@
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

-/* $Id: adb.c,v 1.149 2000/08/26 02:21:44 explorer Exp $ */
+/* $Id: adb.c,v 1.150 2000/09/06 02:39:56 explorer Exp $ */

 /*
 * Implementation notes
@@ -144,8 +144,6 @@ struct dns_adb {
 	isc_mempool_t		       *afmp;	/* dns_adbfetch_t */
 	isc_mempool_t		       *af6mp;	/* dns_adbfetch6_t */

-	isc_random_t			rand;
-
 	/*
 	 * Bucketized locks and lists for names.
 	 *
@@ -1405,7 +1403,7 @@ new_adbentry(dns_adb_t *adb) {
 	e->flags = 0;
 	e->edns_level = -1;
 	e->goodness = 0;
-	isc_random_get(&adb->rand, &r);
+	isc_random_get(&r);
 	e->srtt = (r & 0x1f) + 1;
 	e->expires = 0;
 	e->avoid_bitstring = 0;
@@ -2141,8 +2139,6 @@ destroy(dns_adb_t *adb) {
 	DESTROYLOCK(&adb->lock);
 	DESTROYLOCK(&adb->mplock);

-	isc_random_invalidate(&adb->rand);
-
 	isc_mem_put(adb->mctx, adb, sizeof (dns_adb_t));
 }

@@ -2198,10 +2194,6 @@ dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *timermgr,
 	adb->shutting_down = ISC_FALSE;
 	ISC_LIST_INIT(adb->whenshutdown);

-	result = isc_random_init(&adb->rand);
-	if (result != ISC_R_SUCCESS)
-		goto fail0a;
-
 	result = isc_mutex_init(&adb->lock);
 	if (result != ISC_R_SUCCESS)
 		goto fail0b;
@@ -2326,8 +2318,6 @@ dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *timermgr,
 fail0c:
 	DESTROYLOCK(&adb->lock);
 fail0b:
-	isc_random_invalidate(&adb->rand);
- fail0a:
 	isc_mem_put(mem, adb, sizeof (dns_adb_t));

 	return (result);
--- a/lib/dns/rbtdb.c
+++ b/lib/dns/rbtdb.c
@@ -15,7 +15,7 @@
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

-/* $Id: rbtdb.c,v 1.122 2000/08/31 12:15:11 marka Exp $ */
+/* $Id: rbtdb.c,v 1.123 2000/09/06 02:39:57 explorer Exp $ */

 /*
 * Principal Author: Bob Halley
@@ -166,7 +166,6 @@ typedef struct {
 	rbtdb_version_t *		future_version;
 	rbtdb_versionlist_t		open_versions;
 	isc_boolean_t			overmem;
-	isc_random_t			random;
 	/* Locked by tree_lock. */
 	dns_rbt_t *			tree;
 	isc_boolean_t			secure;
@@ -330,7 +329,6 @@ free_rbtdb(dns_rbtdb_t *rbtdb) {
 	REQUIRE(EMPTY(rbtdb->open_versions));
 	REQUIRE(rbtdb->future_version == NULL);

-	isc_random_invalidate(&rbtdb->random);
 	if (rbtdb->current_version != NULL)
 		isc_mem_put(rbtdb->common.mctx, rbtdb->current_version,
 			    sizeof (rbtdb_version_t));
@@ -2736,7 +2734,7 @@ expirenode(dns_db_t *db, dns_dbnode_t *node, isc_stdtime_t now) {
 			if (rbtdb->overmem)
 				fprintf(stderr, "overmem stale\n");
 		} else if (rbtdb->overmem) {
-			isc_random_get(&rbtdb->random, &val);
+			isc_random_get(&val);
 			if ((val % 7) == 0) {
 				fprintf(stderr, "overmem expire\n");
 				header->ttl = 0;
@@ -4031,7 +4029,6 @@ dns_rbtdb_create
 	rbtdb->attributes = 0;
 	rbtdb->secure = ISC_FALSE;
 	rbtdb->overmem = ISC_FALSE;
-	isc_random_init(&rbtdb->random);

 	/*
 	 * Version Initialization.
--- a/lib/isc/include/isc/random.h
+++ b/lib/isc/include/isc/random.h
@@ -15,7 +15,7 @@
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

-/* $Id: random.h,v 1.7 2000/08/01 01:30:37 tale Exp $ */
+/* $Id: random.h,v 1.8 2000/09/06 02:40:00 explorer Exp $ */

 #ifndef ISC_RANDOM_H
 #define ISC_RANDOM_H 1
@@ -27,65 +27,35 @@
 * Implements a random state pool which will let the caller return a
 * series of possibly non-reproducable random values.  Note that the
 * strength of these numbers is not all that high, and should not be
- * used in cryptography functions.
+ * used in cryptography functions.  It is useful to jitter values a bit
+ * here and there, such as timeouts, etc.
 */

 ISC_LANG_BEGINDECLS

-struct isc_random {
-	unsigned int	magic;
-#if 0
-	isc_mutex_t	lock;
-#endif
-};
-
-#define ISC_RANDOM_MAGIC	0x52416e64	/* RAnd. */
-#define ISC_RANDOM_VALID(x)	((x) != NULL && (x->magic) == ISC_RANDOM_MAGIC)
-
-isc_result_t
-isc_random_init(isc_random_t *r);
+void
+isc_random_seed(isc_uint32_t seed);
 /*
- * Initialize a random state.
- *
- * This function must be called before using any of the following functions.
- *
- * Requires:
- *	r != NULL.
- */
-
-isc_result_t
-isc_random_invalidate(isc_random_t *r);
-/*
- * Invalidate a random state.  This will wipe any information contained in
- * the state and make it unusable.
- *
- * Requires:
- *	r be a valid pool.
+ * Set the initial seed of the random state.
 */

 void
-isc_random_seed(isc_random_t *r, isc_uint32_t seed);
+isc_random_get(isc_uint32_t *val);
 /*
- * Set the initial seed of the random state.  Note that on some systems
- * the private state isn't all that private, and setting the seed may
- * alter numbers returned to other state pools.
+ * Get a random value.
 *
 * Requires:
- *	r be a valid pool.
- */
-
-void
-isc_random_get(isc_random_t *r, isc_uint32_t *val);
-/*
- * Get a random value.  Note that on some systems the private state isn't
- * all that private, and getting a value may alter what other state pools
- * would have returned.
- *
- * Requires:
- *	r be a valid pool.
 *	val != NULL.
 */

+isc_uint32_t
+isc_random_jitter(isc_uint32_t max, isc_uint32_t min, isc_uint32_t jitter);
+/*
+ * Return a value between (max - jitter) and (max).
+ *
+ * If (max - min) < jitter, the maximum jitter becomes (max - min) instead.
+ */
+
 ISC_LANG_ENDDECLS

 #endif /* ISC_RANDOM_H */
--- a/lib/isc/random.c
+++ b/lib/isc/random.c
@@ -15,7 +15,7 @@
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

-/* $Id: random.c,v 1.10 2000/08/26 01:23:14 bwelling Exp $ */
+/* $Id: random.c,v 1.11 2000/09/06 02:39:59 explorer Exp $ */

 #include <config.h>

@@ -28,12 +28,11 @@
 #include <isc/util.h>

 static isc_once_t once = ISC_ONCE_INIT;
-static isc_mutex_t rand_lock;

 static void
 initialize_rand(void)
 {
-	RUNTIME_CHECK(isc_mutex_init(&rand_lock) == ISC_R_SUCCESS);
+	srand(time(NULL));
 }

 static void
@@ -42,75 +41,36 @@ initialize(void)
 	RUNTIME_CHECK(isc_once_do(&once, initialize_rand) == ISC_R_SUCCESS);
 }

-isc_result_t
-isc_random_init(isc_random_t *r)
-{
-	REQUIRE(r != NULL);
-
-	r->magic = ISC_RANDOM_MAGIC;
-#if 0
-	return (isc_mutex_init(&r->lock));
-#else
-	return (ISC_R_SUCCESS);
-#endif
-}
-
-isc_result_t
-isc_random_invalidate(isc_random_t *r)
-{
-	isc_result_t result;
-
-	REQUIRE(ISC_RANDOM_VALID(r));
-
-#if 0
-	DESTROYLOCK(&r->lock);
-	result = ISC_R_SUCCESS;
-#else
-	result = ISC_R_SUCCESS;
-#endif
-
-	memset(r, 0, sizeof(isc_random_t));
-
-	return (result);
-}
-
 void
-isc_random_seed(isc_random_t *r, isc_uint32_t seed)
+isc_random_seed(isc_uint32_t seed)
 {
-	REQUIRE(ISC_RANDOM_VALID(r));
-
-	UNUSED(r);
-
 	initialize();

-#if 0
-	LOCK(&r->lock);
-#endif
-	LOCK(&rand_lock);
 	srand(seed);
-	UNLOCK(&rand_lock);
-#if 0
-	UNLOCK(&r->lock);
-#endif
 }

 void
-isc_random_get(isc_random_t *r, isc_uint32_t *val)
+isc_random_get(isc_uint32_t *val)
 {
-	REQUIRE(ISC_RANDOM_VALID(r));
 	REQUIRE(val != NULL);

-	UNUSED(r);
-
 	initialize();

-#if 0
-	LOCK(&r->lock);
-#endif
-	LOCK(&rand_lock);
 	*val = rand();
-	UNLOCK(&rand_lock);
-#if 0
-	UNLOCK(&r->lock);
-#endif
+}
+
+isc_uint32_t
+isc_random_jitter(isc_uint32_t max, isc_uint32_t min, isc_uint32_t jitter) {
+	isc_uint32_t val;
+
+	REQUIRE(jitter > 0);
+
+	/*
+	 * Don't allow jitter to be more than max - min.
+	 */
+	if (jitter > max - min)
+		jitter = max - min;
+
+	val = rand() % jitter;
+	return (max - val);
 }