mirror of
https://github.com/openvswitch/ovs
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183126a1dc
It's easy to add two tags together, but it's hard to subtract them. The new "tag_tracker" data structure provides a solution. Signed-off-by: Ben Pfaff <blp@nicira.com>
250 lines
11 KiB
C
250 lines
11 KiB
C
/*
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* Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef CLASSIFIER_H
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#define CLASSIFIER_H 1
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/* Flow classifier.
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*
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*
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* What?
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* =====
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*
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* A flow classifier holds any number of "rules", each of which specifies
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* values to match for some fields or subfields and a priority. The primary
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* design goal for the classifier is that, given a packet, it can as quickly as
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* possible find the highest-priority rule that matches the packet.
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*
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* Each OpenFlow table is implemented as a flow classifier.
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*
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*
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* Basic Design
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* ============
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*
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* Suppose that all the rules in a classifier had the same form. For example,
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* suppose that they all matched on the source and destination Ethernet address
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* and wildcarded all the other fields. Then the obvious way to implement a
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* classifier would be a hash table on the source and destination Ethernet
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* addresses. If new classification rules came along with a different form,
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* you could add a second hash table that hashed on the fields matched in those
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* rules. With two hash tables, you look up a given flow in each hash table.
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* If there are no matches, the classifier didn't contain a match; if you find
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* a match in one of them, that's the result; if you find a match in both of
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* them, then the result is the rule with the higher priority.
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*
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* This is how the classifier works. In a "struct classifier", each form of
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* "struct cls_rule" present (based on its ->match.mask) goes into a separate
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* "struct cls_table". A lookup does a hash lookup in every "struct cls_table"
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* in the classifier and tracks the highest-priority match that it finds. The
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* tables are kept in a descending priority order according to the highest
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* priority rule in each table, which allows lookup to skip over tables that
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* can't possibly have a higher-priority match than already found.
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*
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* One detail: a classifier can contain multiple rules that are identical other
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* than their priority. When this happens, only the highest priority rule out
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* of a group of otherwise identical rules is stored directly in the "struct
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* cls_table", with the other almost-identical rules chained off a linked list
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* inside that highest-priority rule.
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*
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*
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* Partitioning
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* ============
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*
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* Suppose that a given classifier is being used to handle multiple stages in a
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* pipeline using "resubmit", with metadata (that is, the OpenFlow 1.1+ field
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* named "metadata") distinguishing between the different stages. For example,
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* metadata value 1 might identify ingress rules, metadata value 2 might
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* identify ACLs, and metadata value 3 might identify egress rules. Such a
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* classifier is essentially partitioned into multiple sub-classifiers on the
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* basis of the metadata value.
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*
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* The classifier has a special optimization to speed up matching in this
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* scenario:
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*
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* - Each cls_table that matches on metadata gets a tag derived from the
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* table's mask, so that it is likely that each table has a unique tag.
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* (Duplicate tags have a performance cost but do not affect
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* correctness.)
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*
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* - For each metadata value matched by any cls_rule, the classifier
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* constructs a "struct cls_partition" indexed by the metadata value.
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* The cls_partition has a 'tags' member whose value is the bitwise-OR of
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* the tags of each cls_table that contains any rule that matches on the
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* cls_partition's metadata value. In other words, struct cls_partition
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* associates metadata values with tables that need to be checked with
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* flows with that specific metadata value.
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*
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* Thus, a flow lookup can start by looking up the partition associated with
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* the flow's metadata, and then skip over any cls_table whose 'tag' does not
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* intersect the partition's 'tags'. (The flow must also be looked up in any
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* cls_table that doesn't match on metadata. We handle that by giving any such
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* cls_table TAG_ALL as its 'tags' so that it matches any tag.)
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*
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*
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* Thread-safety
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* =============
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*
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* When locked properly, the classifier is thread safe as long as the following
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* conditions are satisfied.
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* - Only the main thread calls functions requiring a write lock.
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* - Only the main thread is allowed to iterate over rules. */
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#include "flow.h"
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#include "hmap.h"
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#include "list.h"
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#include "match.h"
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#include "tag.h"
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#include "openflow/nicira-ext.h"
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#include "openflow/openflow.h"
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#include "ovs-thread.h"
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#include "util.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Needed only for the lock annotation in struct classifier. */
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extern struct ovs_mutex ofproto_mutex;
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/* A flow classifier. */
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struct classifier {
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int n_rules; /* Total number of rules. */
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struct hmap tables; /* Contains "struct cls_table"s. */
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struct list tables_priority; /* Tables in descending priority order */
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struct hmap partitions; /* Contains "struct cls_partition"s. */
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struct ovs_rwlock rwlock OVS_ACQ_AFTER(ofproto_mutex);
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};
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/* A set of rules that all have the same fields wildcarded. */
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struct cls_table {
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struct hmap_node hmap_node; /* Within struct classifier 'tables' hmap. */
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struct list list_node; /* Within classifier 'tables_priority_list' */
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struct hmap rules; /* Contains "struct cls_rule"s. */
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struct minimask mask; /* Wildcards for fields. */
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int n_table_rules; /* Number of rules, including duplicates. */
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unsigned int max_priority; /* Max priority of any rule in the table. */
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unsigned int max_count; /* Count of max_priority rules. */
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tag_type tag; /* Tag generated from mask for partitioning. */
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};
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/* Returns true if 'table' is a "catch-all" table that will match every
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* packet (if there is no higher-priority match). */
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static inline bool
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cls_table_is_catchall(const struct cls_table *table)
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{
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return minimask_is_catchall(&table->mask);
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}
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/* A rule in a "struct classifier". */
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struct cls_rule {
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struct hmap_node hmap_node; /* Within struct cls_table 'rules'. */
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struct list list; /* List of identical, lower-priority rules. */
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struct minimatch match; /* Matching rule. */
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unsigned int priority; /* Larger numbers are higher priorities. */
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struct cls_partition *partition;
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};
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/* Associates a metadata value (that is, a value of the OpenFlow 1.1+ metadata
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* field) with tags for the "cls_table"s that contain rules that match that
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* metadata value. */
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struct cls_partition {
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struct hmap_node hmap_node; /* In struct classifier's 'partitions' hmap. */
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ovs_be64 metadata; /* metadata value for this partition. */
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tag_type tags; /* OR of each included flow's cls_table tag. */
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struct tag_tracker tracker; /* Tracks the bits in 'tags'. */
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};
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void cls_rule_init(struct cls_rule *, const struct match *,
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unsigned int priority);
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void cls_rule_init_from_minimatch(struct cls_rule *, const struct minimatch *,
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unsigned int priority);
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void cls_rule_clone(struct cls_rule *, const struct cls_rule *);
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void cls_rule_move(struct cls_rule *dst, struct cls_rule *src);
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void cls_rule_destroy(struct cls_rule *);
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bool cls_rule_equal(const struct cls_rule *, const struct cls_rule *);
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uint32_t cls_rule_hash(const struct cls_rule *, uint32_t basis);
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void cls_rule_format(const struct cls_rule *, struct ds *);
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bool cls_rule_is_catchall(const struct cls_rule *);
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bool cls_rule_is_loose_match(const struct cls_rule *rule,
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const struct minimatch *criteria);
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void classifier_init(struct classifier *cls);
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void classifier_destroy(struct classifier *);
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bool classifier_is_empty(const struct classifier *cls)
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OVS_REQ_RDLOCK(cls->rwlock);
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int classifier_count(const struct classifier *cls)
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OVS_REQ_RDLOCK(cls->rwlock);
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void classifier_insert(struct classifier *cls, struct cls_rule *)
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OVS_REQ_WRLOCK(cls->rwlock);
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struct cls_rule *classifier_replace(struct classifier *cls, struct cls_rule *)
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OVS_REQ_WRLOCK(cls->rwlock);
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void classifier_remove(struct classifier *cls, struct cls_rule *)
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OVS_REQ_WRLOCK(cls->rwlock);
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struct cls_rule *classifier_lookup(const struct classifier *cls,
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const struct flow *,
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struct flow_wildcards *)
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OVS_REQ_RDLOCK(cls->rwlock);
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bool classifier_rule_overlaps(const struct classifier *cls,
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const struct cls_rule *)
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OVS_REQ_RDLOCK(cls->rwlock);
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typedef void cls_cb_func(struct cls_rule *, void *aux);
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struct cls_rule *classifier_find_rule_exactly(const struct classifier *cls,
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const struct cls_rule *)
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OVS_REQ_RDLOCK(cls->rwlock);
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struct cls_rule *classifier_find_match_exactly(const struct classifier *cls,
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const struct match *,
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unsigned int priority)
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OVS_REQ_RDLOCK(cls->rwlock);
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/* Iteration. */
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struct cls_cursor {
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const struct classifier *cls;
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const struct cls_table *table;
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const struct cls_rule *target;
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};
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void cls_cursor_init(struct cls_cursor *cursor, const struct classifier *cls,
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const struct cls_rule *match) OVS_REQ_RDLOCK(cls->rwlock);
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struct cls_rule *cls_cursor_first(struct cls_cursor *cursor);
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struct cls_rule *cls_cursor_next(struct cls_cursor *cursor, const struct cls_rule *);
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#define CLS_CURSOR_FOR_EACH(RULE, MEMBER, CURSOR) \
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for (ASSIGN_CONTAINER(RULE, cls_cursor_first(CURSOR), MEMBER); \
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RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER); \
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ASSIGN_CONTAINER(RULE, cls_cursor_next(CURSOR, &(RULE)->MEMBER), \
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MEMBER))
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#define CLS_CURSOR_FOR_EACH_SAFE(RULE, NEXT, MEMBER, CURSOR) \
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for (ASSIGN_CONTAINER(RULE, cls_cursor_first(CURSOR), MEMBER); \
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(RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER) \
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? ASSIGN_CONTAINER(NEXT, cls_cursor_next(CURSOR, &(RULE)->MEMBER), \
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MEMBER), 1 \
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: 0); \
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(RULE) = (NEXT))
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#ifdef __cplusplus
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}
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#endif
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#endif /* classifier.h */
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