/*
- * Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
+ * Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* =====
*
* A flow classifier holds any number of "rules", each of which specifies
- * values to match for some fields or subfields and a priority. The primary
- * design goal for the classifier is that, given a packet, it can as quickly as
- * possible find the highest-priority rule that matches the packet.
+ * values to match for some fields or subfields and a priority. Each OpenFlow
+ * table is implemented as a flow classifier.
*
- * Each OpenFlow table is implemented as a flow classifier.
+ * The classifier has two primary design goals. The first is obvious: given a
+ * set of packet headers, as quickly as possible find the highest-priority rule
+ * that matches those headers. The following section describes the second
+ * goal.
*
*
- * Basic Design
- * ============
+ * "Un-wildcarding"
+ * ================
+ *
+ * A primary goal of the flow classifier is to produce, as a side effect of a
+ * packet lookup, a wildcard mask that indicates which bits of the packet
+ * headers were essential to the classification result. Ideally, a 1-bit in
+ * any position of this mask means that, if the corresponding bit in the packet
+ * header were flipped, then the classification result might change. A 0-bit
+ * means that changing the packet header bit would have no effect. Thus, the
+ * wildcarded bits are the ones that played no role in the classification
+ * decision.
+ *
+ * Such a wildcard mask is useful with datapaths that support installing flows
+ * that wildcard fields or subfields. If an OpenFlow lookup for a TCP flow
+ * does not actually look at the TCP source or destination ports, for example,
+ * then the switch may install into the datapath a flow that wildcards the port
+ * numbers, which in turn allows the datapath to handle packets that arrive for
+ * other TCP source or destination ports without additional help from
+ * ovs-vswitchd. This is useful for the Open vSwitch software and,
+ * potentially, for ASIC-based switches as well.
+ *
+ * Some properties of the wildcard mask:
+ *
+ * - "False 1-bits" are acceptable, that is, setting a bit in the wildcard
+ * mask to 1 will never cause a packet to be forwarded the wrong way.
+ * As a corollary, a wildcard mask composed of all 1-bits will always
+ * yield correct (but often needlessly inefficient) behavior.
+ *
+ * - "False 0-bits" can cause problems, so they must be avoided. In the
+ * extreme case, a mask of all 0-bits is only correct if the classifier
+ * contains only a single flow that matches all packets.
+ *
+ * - 0-bits are desirable because they allow the datapath to act more
+ * autonomously, relying less on ovs-vswitchd to process flow setups,
+ * thereby improving performance.
+ *
+ * - We don't know a good way to generate wildcard masks with the maximum
+ * (correct) number of 0-bits. We use various approximations, described
+ * in later sections.
+ *
+ * - Wildcard masks for lookups in a given classifier yield a
+ * non-overlapping set of rules. More specifically:
+ *
+ * Consider an classifier C1 filled with an arbitrary collection of rules
+ * and an empty classifier C2. Now take a set of packet headers H and
+ * look it up in C1, yielding a highest-priority matching rule R1 and
+ * wildcard mask M. Form a new classifier rule R2 out of packet headers
+ * H and mask M, and add R2 to C2 with a fixed priority. If one were to
+ * do this for every possible set of packet headers H, then this
+ * process would not attempt to add any overlapping rules to C2, that is,
+ * any packet lookup using the rules generated by this process matches at
+ * most one rule in C2.
+ *
+ * During the lookup process, the classifier starts out with a wildcard mask
+ * that is all 0-bits, that is, fully wildcarded. As lookup proceeds, each
+ * step tends to add constraints to the wildcard mask, that is, change
+ * wildcarded 0-bits into exact-match 1-bits. We call this "un-wildcarding".
+ * A lookup step that examines a particular field must un-wildcard that field.
+ * In general, un-wildcarding is necessary for correctness but undesirable for
+ * performance.
+ *
+ *
+ * Basic Classifier Design
+ * =======================
*
* Suppose that all the rules in a classifier had the same form. For example,
* suppose that they all matched on the source and destination Ethernet address
* cls_subtable" in the classifier and tracks the highest-priority match that
* it finds. The subtables are kept in a descending priority order according
* to the highest priority rule in each subtable, which allows lookup to skip
- * over subtables that can't possibly have a higher-priority match than
- * already found.
+ * over subtables that can't possibly have a higher-priority match than already
+ * found. Eliminating lookups through priority ordering aids both classifier
+ * primary design goals: skipping lookups saves time and avoids un-wildcarding
+ * fields that those lookups would have examined.
*
* One detail: a classifier can contain multiple rules that are identical other
* than their priority. When this happens, only the highest priority rule out
* cls_subtable", with the other almost-identical rules chained off a linked
* list inside that highest-priority rule.
*
+ * The following sub-sections describe various optimizations over this simple
+ * approach.
*
- * Staged Lookup
- * =============
+ *
+ * Staged Lookup (Wildcard Optimization)
+ * -------------------------------------
*
* Subtable lookup is performed in ranges defined for struct flow, starting
* from metadata (registers, in_port, etc.), then L2 header, L3, and finally
* L4 ports. Whenever it is found that there are no matches in the current
- * subtable, the rest of the subtable can be skipped. The rationale of this
- * logic is that as many fields as possible can remain wildcarded.
+ * subtable, the rest of the subtable can be skipped.
+ *
+ * Staged lookup does not reduce lookup time, and it may increase it, because
+ * it changes a single hash table lookup into multiple hash table lookups.
+ * It reduces un-wildcarding significantly in important use cases.
+ *
+ *
+ * Prefix Tracking (Wildcard Optimization)
+ * ---------------------------------------
*
+ * Classifier uses prefix trees ("tries") for tracking the used
+ * address space, enabling skipping classifier tables containing
+ * longer masks than necessary for the given address. This reduces
+ * un-wildcarding for datapath flows in parts of the address space
+ * without host routes, but consulting extra data structures (the
+ * tries) may slightly increase lookup time.
*
- * Partitioning
- * ============
+ * Trie lookup is interwoven with staged lookup, so that a trie is
+ * searched only when the configured trie field becomes relevant for
+ * the lookup. The trie lookup results are retained so that each trie
+ * is checked at most once for each classifier lookup.
+ *
+ * This implementation tracks the number of rules at each address
+ * prefix for the whole classifier. More aggressive table skipping
+ * would be possible by maintaining lists of tables that have prefixes
+ * at the lengths encountered on tree traversal, or by maintaining
+ * separate tries for subsets of rules separated by metadata fields.
+ *
+ * Prefix tracking is configured via OVSDB "Flow_Table" table,
+ * "fieldspec" column. "fieldspec" is a string map where a "prefix"
+ * key tells which fields should be used for prefix tracking. The
+ * value of the "prefix" key is a comma separated list of field names.
+ *
+ * There is a maximum number of fields that can be enabled for any one
+ * flow table. Currently this limit is 3.
+ *
+ *
+ * Partitioning (Lookup Time and Wildcard Optimization)
+ * ----------------------------------------------------
*
* Suppose that a given classifier is being used to handle multiple stages in a
* pipeline using "resubmit", with metadata (that is, the OpenFlow 1.1+ field
* any cls_subtable that doesn't match on metadata. We handle that by giving
* any such cls_subtable TAG_ALL as its 'tags' so that it matches any tag.)
*
+ * Partitioning saves lookup time by reducing the number of subtable lookups.
+ * Each eliminated subtable lookup also reduces the amount of un-wildcarding.
+ *
+ *
+ * Classifier Versioning
+ * =====================
+ *
+ * Classifier lookups are always done in a specific classifier version, where
+ * a version is defined to be a natural number.
+ *
+ * When a new rule is added to a classifier, it is set to become visible in a
+ * specific version. If the version number used at insert time is larger than
+ * any version number currently used in lookups, the new rule is said to be
+ * invisible to lookups. This means that lookups won't find the rule, but the
+ * rule is immediately available to classifier iterations.
+ *
+ * Similarly, a rule can be marked as to be deleted in a future version. To
+ * delete a rule in a way to not remove the rule before all ongoing lookups are
+ * finished, the rule should be made invisible in a specific version number.
+ * Then, when all the lookups use a later version number, the rule can be
+ * actually removed from the classifier.
+ *
+ * Classifiers can hold duplicate rules (rules with the same match criteria and
+ * priority) when at most one of these duplicates is visible in any given
+ * lookup version. The caller responsible for classifier modifications must
+ * maintain this invariant.
+ *
+ * The classifier supports versioning for two reasons:
+ *
+ * 1. Support for versioned modifications makes it possible to perform an
+ * arbitraty series of classifier changes as one atomic transaction,
+ * where intermediate versions of the classifier are not visible to any
+ * lookups. Also, when a rule is added for a future version, or marked
+ * for removal after the current version, such modifications can be
+ * reverted without any visible effects to any of the current lookups.
+ *
+ * 2. Performance: Adding (or deleting) a large set of rules can, in
+ * pathological cases, have a cost proportional to the number of rules
+ * already in the classifier. When multiple rules are being added (or
+ * deleted) in one go, though, this pathological case cost can be
+ * typically avoided, as long as it is OK for any new rules to be
+ * invisible until the batch change is complete.
+ *
+ * Note that the classifier_replace() function replaces a rule immediately, and
+ * is therefore not safe to use with versioning. It is still available for the
+ * users that do not use versioning.
+ *
+ *
+ * Deferred Publication
+ * ====================
+ *
+ * Removing large number of rules from classifier can be costly, as the
+ * supporting data structures are teared down, in many cases just to be
+ * re-instantiated right after. In the worst case, as when each rule has a
+ * different match pattern (mask), the maintenance of the match patterns can
+ * have cost O(N^2), where N is the number of different match patterns. To
+ * alleviate this, the classifier supports a "deferred mode", in which changes
+ * in internal data structures needed for future version lookups may not be
+ * fully computed yet. The computation is finalized when the deferred mode is
+ * turned off.
+ *
+ * This feature can be used with versioning such that all changes to future
+ * versions are made in the deferred mode. Then, right before making the new
+ * version visible to lookups, the deferred mode is turned off so that all the
+ * data structures are ready for lookups with the new version number.
+ *
+ * To use deferred publication, first call classifier_defer(). Then, modify
+ * the classifier via additions (classifier_insert() with a specific, future
+ * version number) and deletions (use cls_rule_make_removable_after_version()).
+ * Then call classifier_publish(), and after that, announce the new version
+ * number to be used in lookups.
+ *
*
* Thread-safety
* =============
*
- * The classifier may safely be accessed by many reader threads concurrently or
- * by a single writer. */
+ * The classifier may safely be accessed by many reader threads concurrently
+ * and by a single writer, or by multiple writers when they guarantee mutually
+ * exlucive access to classifier modifications.
+ *
+ * Since the classifier rules are RCU protected, the rule destruction after
+ * removal from the classifier must be RCU postponed. Also, when versioning is
+ * used, the rule removal itself needs to be typically RCU postponed. In this
+ * case the rule destruction is doubly RCU postponed, i.e., the second
+ * ovsrcu_postpone() call to destruct the rule is called from the first RCU
+ * callback that removes the rule.
+ *
+ * Rules that have never been visible to lookups are an exeption to the above
+ * rule. Such rules can be removed immediately, but their destruction must
+ * still be RCU postponed, as the rule's visibility attribute may be examined
+ * parallel to the rule's removal. */
-#include "flow.h"
-#include "hindex.h"
-#include "hmap.h"
-#include "list.h"
+#include "cmap.h"
#include "match.h"
-#include "tag.h"
-#include "openflow/nicira-ext.h"
-#include "openflow/openflow.h"
-#include "ovs-thread.h"
-#include "util.h"
+#include "meta-flow.h"
+#include "pvector.h"
+#include "rculist.h"
+#include "type-props.h"
#ifdef __cplusplus
extern "C" {
#endif
-/* Needed only for the lock annotation in struct classifier. */
-extern struct ovs_mutex ofproto_mutex;
+/* Classifier internal data structures. */
+struct cls_subtable;
+struct cls_match;
+
+struct trie_node;
+typedef OVSRCU_TYPE(struct trie_node *) rcu_trie_ptr;
-/* Maximum number of staged lookup indices for each subtable. */
-enum { CLS_MAX_INDICES = 3 };
+/* Prefix trie for a 'field' */
+struct cls_trie {
+ const struct mf_field *field; /* Trie field, or NULL. */
+ rcu_trie_ptr root; /* NULL if none. */
+};
+
+typedef uint64_t cls_version_t;
+
+#define CLS_MIN_VERSION 0 /* Default version number to use. */
+#define CLS_MAX_VERSION (TYPE_MAXIMUM(cls_version_t) - 1)
+#define CLS_NOT_REMOVED_VERSION TYPE_MAXIMUM(cls_version_t)
+
+enum {
+ CLS_MAX_INDICES = 3, /* Maximum number of lookup indices per subtable. */
+ CLS_MAX_TRIES = 3 /* Maximum number of prefix trees per classifier. */
+};
/* A flow classifier. */
struct classifier {
- int n_rules; /* Total number of rules. */
+ int n_rules; /* Total number of rules. */
uint8_t n_flow_segments;
uint8_t flow_segments[CLS_MAX_INDICES]; /* Flow segment boundaries to use
* for staged lookup. */
- struct hmap subtables; /* Contains "struct cls_subtable"s. */
- struct list subtables_priority; /* Subtables in descending priority order.
- */
- struct hmap partitions; /* Contains "struct cls_partition"s. */
- struct ovs_rwlock rwlock OVS_ACQ_AFTER(ofproto_mutex);
+ struct cmap subtables_map; /* Contains "struct cls_subtable"s. */
+ struct pvector subtables;
+ struct cmap partitions; /* Contains "struct cls_partition"s. */
+ struct cls_trie tries[CLS_MAX_TRIES]; /* Prefix tries. */
+ unsigned int n_tries;
+ bool publish; /* Make changes visible to lookups? */
};
-/* A set of rules that all have the same fields wildcarded. */
-struct cls_subtable {
- struct hmap_node hmap_node; /* Within struct classifier 'subtables' hmap.
- */
- struct list list_node; /* Within classifier 'subtables_priority' list.
- */
- struct hmap rules; /* Contains "struct cls_rule"s. */
- struct minimask mask; /* Wildcards for fields. */
- int n_rules; /* Number of rules, including duplicates. */
- unsigned int max_priority; /* Max priority of any rule in the subtable. */
- unsigned int max_count; /* Count of max_priority rules. */
- tag_type tag; /* Tag generated from mask for partitioning. */
- uint8_t n_indices; /* How many indices to use. */
- uint8_t index_ofs[CLS_MAX_INDICES]; /* u32 flow segment boundaries. */
- struct hindex indices[CLS_MAX_INDICES]; /* Staged lookup indices. */
+struct cls_conjunction {
+ uint32_t id;
+ uint8_t clause;
+ uint8_t n_clauses;
};
-/* Returns true if 'table' is a "catch-all" subtable that will match every
- * packet (if there is no higher-priority match). */
-static inline bool
-cls_subtable_is_catchall(const struct cls_subtable *subtable)
-{
- return minimask_is_catchall(&subtable->mask);
-}
-
-/* A rule in a "struct cls_subtable". */
+/* A rule to be inserted to the classifier. */
struct cls_rule {
- struct hmap_node hmap_node; /* Within struct cls_subtable 'rules'. */
- struct list list; /* List of identical, lower-priority rules. */
- struct minimatch match; /* Matching rule. */
- unsigned int priority; /* Larger numbers are higher priorities. */
- struct cls_partition *partition;
- struct hindex_node index_nodes[CLS_MAX_INDICES]; /* Within subtable's
- * 'indices'. */
+ struct rculist node; /* In struct cls_subtable 'rules_list'. */
+ const int priority; /* Larger numbers are higher priorities. */
+ struct cls_match *cls_match; /* NULL if not in a classifier. */
+ const struct minimatch match; /* Matching rule. */
};
-/* Associates a metadata value (that is, a value of the OpenFlow 1.1+ metadata
- * field) with tags for the "cls_subtable"s that contain rules that match that
- * metadata value. */
-struct cls_partition {
- struct hmap_node hmap_node; /* In struct classifier's 'partitions' hmap. */
- ovs_be64 metadata; /* metadata value for this partition. */
- tag_type tags; /* OR of each flow's cls_subtable tag. */
- struct tag_tracker tracker; /* Tracks the bits in 'tags'. */
-};
-
-void cls_rule_init(struct cls_rule *, const struct match *,
- unsigned int priority);
+void cls_rule_init(struct cls_rule *, const struct match *, int priority);
void cls_rule_init_from_minimatch(struct cls_rule *, const struct minimatch *,
- unsigned int priority);
+ int priority);
void cls_rule_clone(struct cls_rule *, const struct cls_rule *);
void cls_rule_move(struct cls_rule *dst, struct cls_rule *src);
void cls_rule_destroy(struct cls_rule *);
-bool cls_rule_equal(const struct cls_rule *, const struct cls_rule *);
-uint32_t cls_rule_hash(const struct cls_rule *, uint32_t basis);
+void cls_rule_set_conjunctions(struct cls_rule *,
+ const struct cls_conjunction *, size_t n);
+bool cls_rule_equal(const struct cls_rule *, const struct cls_rule *);
void cls_rule_format(const struct cls_rule *, struct ds *);
-
bool cls_rule_is_catchall(const struct cls_rule *);
-
bool cls_rule_is_loose_match(const struct cls_rule *rule,
const struct minimatch *criteria);
+bool cls_rule_visible_in_version(const struct cls_rule *, cls_version_t);
+void cls_rule_make_invisible_in_version(const struct cls_rule *,
+ cls_version_t);
+void cls_rule_restore_visibility(const struct cls_rule *);
-void classifier_init(struct classifier *cls, const uint8_t *flow_segments);
+/* Constructor/destructor. Must run single-threaded. */
+void classifier_init(struct classifier *, const uint8_t *flow_segments);
void classifier_destroy(struct classifier *);
-bool classifier_is_empty(const struct classifier *cls)
- OVS_REQ_RDLOCK(cls->rwlock);
-int classifier_count(const struct classifier *cls)
- OVS_REQ_RDLOCK(cls->rwlock);
-void classifier_insert(struct classifier *cls, struct cls_rule *)
- OVS_REQ_WRLOCK(cls->rwlock);
-struct cls_rule *classifier_replace(struct classifier *cls, struct cls_rule *)
- OVS_REQ_WRLOCK(cls->rwlock);
-void classifier_remove(struct classifier *cls, struct cls_rule *)
- OVS_REQ_WRLOCK(cls->rwlock);
-struct cls_rule *classifier_lookup(const struct classifier *cls,
- const struct flow *,
- struct flow_wildcards *)
- OVS_REQ_RDLOCK(cls->rwlock);
-bool classifier_rule_overlaps(const struct classifier *cls,
- const struct cls_rule *)
- OVS_REQ_RDLOCK(cls->rwlock);
-typedef void cls_cb_func(struct cls_rule *, void *aux);
+/* Modifiers. Caller MUST exclude concurrent calls from other threads. */
+bool classifier_set_prefix_fields(struct classifier *,
+ const enum mf_field_id *trie_fields,
+ unsigned int n_trie_fields);
+void classifier_insert(struct classifier *, const struct cls_rule *,
+ cls_version_t, const struct cls_conjunction *,
+ size_t n_conjunctions);
+const struct cls_rule *classifier_replace(struct classifier *,
+ const struct cls_rule *,
+ cls_version_t,
+ const struct cls_conjunction *,
+ size_t n_conjunctions);
+const struct cls_rule *classifier_remove(struct classifier *,
+ const struct cls_rule *);
+static inline void classifier_defer(struct classifier *);
+static inline void classifier_publish(struct classifier *);
-struct cls_rule *classifier_find_rule_exactly(const struct classifier *cls,
- const struct cls_rule *)
- OVS_REQ_RDLOCK(cls->rwlock);
-struct cls_rule *classifier_find_match_exactly(const struct classifier *cls,
- const struct match *,
- unsigned int priority)
- OVS_REQ_RDLOCK(cls->rwlock);
+/* Lookups. These are RCU protected and may run concurrently with modifiers
+ * and each other. */
+const struct cls_rule *classifier_lookup(const struct classifier *,
+ cls_version_t, struct flow *,
+ struct flow_wildcards *);
+bool classifier_rule_overlaps(const struct classifier *,
+ const struct cls_rule *, cls_version_t);
+const struct cls_rule *classifier_find_rule_exactly(const struct classifier *,
+ const struct cls_rule *,
+ cls_version_t);
+const struct cls_rule *classifier_find_match_exactly(const struct classifier *,
+ const struct match *,
+ int priority,
+ cls_version_t);
+bool classifier_is_empty(const struct classifier *);
+int classifier_count(const struct classifier *);
\f
-/* Iteration. */
-
+/* Iteration.
+ *
+ * Iteration is lockless and RCU-protected. Concurrent threads may perform all
+ * kinds of concurrent modifications without ruining the iteration. Obviously,
+ * any modifications may or may not be visible to the concurrent iterator, but
+ * all the rules not deleted are visited by the iteration. The iterating
+ * thread may also modify the classifier rules itself.
+ *
+ * 'TARGET' iteration only iterates rules matching the 'TARGET' criteria.
+ * Rather than looping through all the rules and skipping ones that can't
+ * match, 'TARGET' iteration skips whole subtables, if the 'TARGET' happens to
+ * be more specific than the subtable. */
struct cls_cursor {
const struct classifier *cls;
const struct cls_subtable *subtable;
const struct cls_rule *target;
+ cls_version_t version; /* Version to iterate. */
+ struct pvector_cursor subtables;
+ const struct cls_rule *rule;
};
-void cls_cursor_init(struct cls_cursor *cursor, const struct classifier *cls,
- const struct cls_rule *match) OVS_REQ_RDLOCK(cls->rwlock);
-struct cls_rule *cls_cursor_first(struct cls_cursor *cursor);
-struct cls_rule *cls_cursor_next(struct cls_cursor *, const struct cls_rule *);
+struct cls_cursor cls_cursor_start(const struct classifier *,
+ const struct cls_rule *target,
+ cls_version_t);
+void cls_cursor_advance(struct cls_cursor *);
+
+#define CLS_FOR_EACH(RULE, MEMBER, CLS) \
+ CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, NULL, CLS_MAX_VERSION)
+#define CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, TARGET, VERSION) \
+ for (struct cls_cursor cursor__ = cls_cursor_start(CLS, TARGET, VERSION); \
+ (cursor__.rule \
+ ? (INIT_CONTAINER(RULE, cursor__.rule, MEMBER), \
+ cls_cursor_advance(&cursor__), \
+ true) \
+ : false); \
+ )
-#define CLS_CURSOR_FOR_EACH(RULE, MEMBER, CURSOR) \
- for (ASSIGN_CONTAINER(RULE, cls_cursor_first(CURSOR), MEMBER); \
- RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER); \
- ASSIGN_CONTAINER(RULE, cls_cursor_next(CURSOR, &(RULE)->MEMBER), \
- MEMBER))
+\f
+static inline void
+classifier_defer(struct classifier *cls)
+{
+ cls->publish = false;
+}
-#define CLS_CURSOR_FOR_EACH_SAFE(RULE, NEXT, MEMBER, CURSOR) \
- for (ASSIGN_CONTAINER(RULE, cls_cursor_first(CURSOR), MEMBER); \
- (RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER) \
- ? ASSIGN_CONTAINER(NEXT, cls_cursor_next(CURSOR, &(RULE)->MEMBER), \
- MEMBER), 1 \
- : 0); \
- (RULE) = (NEXT))
+static inline void
+classifier_publish(struct classifier *cls)
+{
+ cls->publish = true;
+ pvector_publish(&cls->subtables);
+}
#ifdef __cplusplus
}
#endif
-
#endif /* classifier.h */
projects / cascardo / ovs.git / blobdiff