Sync from head

6 files changed, 87 insertions, 0 deletions

diff --git a/usr.sbin/nscd/cachelib.c b/usr.sbin/nscd/cachelib.c
index afdbc0a3fe2b..ab95b2939fe4 100644
--- a/usr.sbin/nscd/cachelib.c
+++ b/usr.sbin/nscd/cachelib.c
@@ -726,6 +726,12 @@ cache_read(struct cache_entry_ *entry, const char *key, size_t key_size,
 		TRACE_OUT(cache_read);
 		return (-1);
 	}
+	/* pretend that entry was not found if confidence is below threshold*/
+	if (find_res->confidence < 
+	    common_entry->common_params.confidence_threshold) {
+		TRACE_OUT(cache_read);
+		return (-1);
+	}
 
 	if ((common_entry->common_params.max_lifetime.tv_sec != 0) ||
 		(common_entry->common_params.max_lifetime.tv_usec != 0)) {
@@ -826,6 +832,24 @@ cache_write(struct cache_entry_ *entry, const char *key, size_t key_size,
 	item = HASHTABLE_GET_ENTRY(&(common_entry->items), hash);
 	find_res = HASHTABLE_ENTRY_FIND(cache_ht_, item, &item_data);
 	if (find_res != NULL) {
+		if (find_res->confidence < common_entry->common_params.confidence_threshold) {
+		  	/* duplicate entry is no error, if confidence is low */
+			if ((find_res->value_size == value_size) &&
+			    (memcmp(find_res->value, value, value_size) == 0)) {
+				/* increase confidence on exact match (key and values) */
+				find_res->confidence++;
+			} else {
+				/* create new entry with low confidence, if value changed */
+				free(item_data.value);
+				item_data.value = malloc(value_size);
+				assert(item_data.value != NULL);
+				memcpy(item_data.value, value, value_size);
+				item_data.value_size = value_size;
+				find_res->confidence = 1;
+			}
+			TRACE_OUT(cache_write);
+			return (0);
+		}
 		TRACE_OUT(cache_write);
 		return (-1);
 	}
@@ -839,6 +863,8 @@ cache_write(struct cache_entry_ *entry, const char *key, size_t key_size,
 	memcpy(item_data.value, value, value_size);
 	item_data.value_size = value_size;
 
+	item_data.confidence = 1;
+
 	policy_item = common_entry->policies[0]->create_item_func();
 	policy_item->key = item_data.key;
 	policy_item->key_size = item_data.key_size;
diff --git a/usr.sbin/nscd/cachelib.h b/usr.sbin/nscd/cachelib.h
index 37f0041e9d32..9df50e786d2c 100644
--- a/usr.sbin/nscd/cachelib.h
+++ b/usr.sbin/nscd/cachelib.h
@@ -92,6 +92,7 @@ struct common_cache_entry_params {
 	size_t	satisf_elemsize;	/* if entry size is exceeded,
 					 * this number of elements will be left,
 					 * others will be deleted */
+	int	confidence_threshold;	/* number matching replies required */
 	struct timeval	max_lifetime;	/* if 0 then no check is made */
 	enum cache_policy_t policy;	/* policy used for transformations */
 };
@@ -116,6 +117,7 @@ struct cache_ht_item_data_ {
 	size_t	value_size;
 
 	struct cache_policy_item_ *fifo_policy_item;
+	int	confidence;	/* incremented for each verification */
 };
 
 struct cache_ht_item_ {
diff --git a/usr.sbin/nscd/config.c b/usr.sbin/nscd/config.c
index 856cf97d8bd2..f44e9862d4bb 100644
--- a/usr.sbin/nscd/config.c
+++ b/usr.sbin/nscd/config.c
@@ -209,6 +209,7 @@ create_def_configuration_entry(const char *name)
 	positive_params.max_elemsize = DEFAULT_POSITIVE_ELEMENTS_SIZE;
 	positive_params.satisf_elemsize = DEFAULT_POSITIVE_ELEMENTS_SIZE / 2;
 	positive_params.max_lifetime.tv_sec = DEFAULT_POSITIVE_LIFETIME;
+	positive_params.confidence_threshold = DEFAULT_POSITIVE_CONF_THRESH;
 	positive_params.policy = CPT_LRU;
 
 	memcpy(&negative_params, &positive_params,
@@ -216,6 +217,7 @@ create_def_configuration_entry(const char *name)
 	negative_params.max_elemsize = DEFAULT_NEGATIVE_ELEMENTS_SIZE;
 	negative_params.satisf_elemsize = DEFAULT_NEGATIVE_ELEMENTS_SIZE / 2;
 	negative_params.max_lifetime.tv_sec = DEFAULT_NEGATIVE_LIFETIME;
+	negative_params.confidence_threshold = DEFAULT_NEGATIVE_CONF_THRESH;
 	negative_params.policy = CPT_FIFO;
 
 	memset(&default_common_timeout, 0, sizeof(struct timeval));
diff --git a/usr.sbin/nscd/config.h b/usr.sbin/nscd/config.h
index 6c42932772cc..29770e64caaf 100644
--- a/usr.sbin/nscd/config.h
+++ b/usr.sbin/nscd/config.h
@@ -44,9 +44,11 @@
 
 #define DEFAULT_POSITIVE_ELEMENTS_SIZE	(2048)
 #define DEFAULT_POSITIVE_LIFETIME 	(3600)
+#define DEFAULT_POSITIVE_CONF_THRESH 	(1)
 
 #define DEFAULT_NEGATIVE_ELEMENTS_SIZE	(2048)
 #define DEFAULT_NEGATIVE_LIFETIME	(60)
+#define DEFAULT_NEGATIVE_CONF_THRESH 	(1) /* (2) ??? */
 
 #define DEFAULT_MULTIPART_ELEMENTS_SIZE	(1024 * 8)
 #define DEFAULT_MULITPART_SESSIONS_SIZE	(1024)
diff --git a/usr.sbin/nscd/nscd.conf.5 b/usr.sbin/nscd/nscd.conf.5
index b5700a4e7b19..b59449b11157 100644
--- a/usr.sbin/nscd/nscd.conf.5
+++ b/usr.sbin/nscd/nscd.conf.5
@@ -102,6 +102,17 @@ The same as the positive-policy, but this one is applied to the negative
 elements of the given
 .Ar cachename .
 The default policy is fifo.
+.It Va negative-confidence-threshold Oo Ar cachename Oc Op Ar value
+The number of times a query must have failed before the cache accepts
+that the element can not be found.
+At the default value of 1 each negative query result is cached and
+immediately returned from the cache on further queries.
+Higher numbers cause queries to be retried at the configured data
+sources the given number of times, before the negative result is
+returned from the cache on further queries.
+This allows to probe for the existence of an entry, and then to create
+it if it did not exist, without the negative probe result preventing
+access to the new entry for the duration of the negative TTL.
 .It Va suggested-size Oo Ar cachename Oc Op Ar value
 This is the internal hash table size.
 The value should be a prime number for optimum performance.
diff --git a/usr.sbin/nscd/parser.c b/usr.sbin/nscd/parser.c
index a36821a75e7a..533dc79ddb33 100644
--- a/usr.sbin/nscd/parser.c
+++ b/usr.sbin/nscd/parser.c
@@ -167,6 +167,38 @@ set_negative_time_to_live(struct configuration *config,
 	TRACE_OUT(set_negative_time_to_live);
 }
 
+static void
+set_positive_confidence_threshold(struct configuration *config,
+	const char *entry_name, int conf_thresh)
+{
+	struct configuration_entry *entry;
+
+	TRACE_IN(set_positive_conf_thresh);
+	assert(conf_thresh > 0);
+	assert(entry_name != NULL);
+
+	entry = find_create_entry(config, entry_name);
+	assert(entry != NULL);
+	entry->positive_cache_params.confidence_threshold = conf_thresh;
+
+	TRACE_OUT(set_positive_conf_thresh);
+}
+
+static void
+set_negative_confidence_threshold(struct configuration *config,
+	const char *entry_name, int conf_thresh)
+{
+	struct configuration_entry *entry;
+
+	TRACE_IN(set_negative_conf_thresh);
+	assert(conf_thresh > 0);
+	assert(entry_name != NULL);
+	entry = find_create_entry(config, entry_name);
+	assert(entry != NULL);
+	entry->negative_cache_params.confidence_threshold = conf_thresh;
+	TRACE_OUT(set_negative_conf_thresh);
+}
+
 /*
  * Hot count is actually the elements size limit.
  */
@@ -393,6 +425,12 @@ parse_config_file(struct configuration *config,
 					fields[1], value);
 				continue;
 			} else if ((field_count == 3) &&
+			(strcmp(fields[0], "positive-confidence-threshold") == 0) &&
+			((value = get_number(fields[2], 1, -1)) != -1)) {
+				set_positive_confidence_threshold(config,
+					fields[1], value);
+				continue;
+			} else if ((field_count == 3) &&
 			(strcmp(fields[0], "positive-policy") == 0) &&
 			(check_cachename(fields[1]) == 0) &&
 			((value = get_policy(fields[2])) != -1)) {
@@ -416,6 +454,12 @@ parse_config_file(struct configuration *config,
 					fields[1], value);
 				continue;
 			} else if ((field_count == 3) &&
+			(strcmp(fields[0], "negative-confidence-threshold") == 0) &&
+			((value = get_number(fields[2], 1, -1)) != -1)) {
+				set_negative_confidence_threshold(config,
+					fields[1], value);
+				continue;
+			} else if ((field_count == 3) &&
 			(strcmp(fields[0], "negative-policy") == 0) &&
 			(check_cachename(fields[1]) == 0) &&
 			((value = get_policy(fields[2])) != -1)) {