lib/classifier.h

   1 /*
   2  * Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef CLASSIFIER_H
  18 #define CLASSIFIER_H 1
  19
  20 /* Flow classifier.
  21  *
  22  *
  23  * What?
  24  * =====
  25  *
  26  * A flow classifier holds any number of "rules", each of which specifies
  27  * values to match for some fields or subfields and a priority.  The primary
  28  * design goal for the classifier is that, given a packet, it can as quickly as
  29  * possible find the highest-priority rule that matches the packet.
  30  *
  31  * Each OpenFlow table is implemented as a flow classifier.
  32  *
  33  *
  34  * Basic Design
  35  * ============
  36  *
  37  * Suppose that all the rules in a classifier had the same form.  For example,
  38  * suppose that they all matched on the source and destination Ethernet address
  39  * and wildcarded all the other fields.  Then the obvious way to implement a
  40  * classifier would be a hash table on the source and destination Ethernet
  41  * addresses.  If new classification rules came along with a different form,
  42  * you could add a second hash table that hashed on the fields matched in those
  43  * rules.  With two hash tables, you look up a given flow in each hash table.
  44  * If there are no matches, the classifier didn't contain a match; if you find
  45  * a match in one of them, that's the result; if you find a match in both of
  46  * them, then the result is the rule with the higher priority.
  47  *
  48  * This is how the classifier works.  In a "struct classifier", each form of
  49  * "struct cls_rule" present (based on its ->match.mask) goes into a separate
  50  * "struct cls_subtable".  A lookup does a hash lookup in every "struct
  51  * cls_subtable" in the classifier and tracks the highest-priority match that
  52  * it finds.  The subtables are kept in a descending priority order according
  53  * to the highest priority rule in each subtable, which allows lookup to skip
  54  * over subtables that can't possibly have a higher-priority match than
  55  * already found.
  56  *
  57  * One detail: a classifier can contain multiple rules that are identical other
  58  * than their priority.  When this happens, only the highest priority rule out
  59  * of a group of otherwise identical rules is stored directly in the "struct
  60  * cls_subtable", with the other almost-identical rules chained off a linked
  61  * list inside that highest-priority rule.
  62  *
  63  *
  64  * Partitioning
  65  * ============
  66  *
  67  * Suppose that a given classifier is being used to handle multiple stages in a
  68  * pipeline using "resubmit", with metadata (that is, the OpenFlow 1.1+ field
  69  * named "metadata") distinguishing between the different stages.  For example,
  70  * metadata value 1 might identify ingress rules, metadata value 2 might
  71  * identify ACLs, and metadata value 3 might identify egress rules.  Such a
  72  * classifier is essentially partitioned into multiple sub-classifiers on the
  73  * basis of the metadata value.
  74  *
  75  * The classifier has a special optimization to speed up matching in this
  76  * scenario:
  77  *
  78  *     - Each cls_subtable that matches on metadata gets a tag derived from the
  79  *       subtable's mask, so that it is likely that each subtable has a unique
  80  *       tag.  (Duplicate tags have a performance cost but do not affect
  81  *       correctness.)
  82  *
  83  *     - For each metadata value matched by any cls_rule, the classifier
  84  *       constructs a "struct cls_partition" indexed by the metadata value.
  85  *       The cls_partition has a 'tags' member whose value is the bitwise-OR of
  86  *       the tags of each cls_subtable that contains any rule that matches on
  87  *       the cls_partition's metadata value.  In other words, struct
  88  *       cls_partition associates metadata values with subtables that need to
  89  *       be checked with flows with that specific metadata value.
  90  *
  91  * Thus, a flow lookup can start by looking up the partition associated with
  92  * the flow's metadata, and then skip over any cls_subtable whose 'tag' does
  93  * not intersect the partition's 'tags'.  (The flow must also be looked up in
  94  * any cls_subtable that doesn't match on metadata.  We handle that by giving
  95  * any such cls_subtable TAG_ALL as its 'tags' so that it matches any tag.)
  96  *
  97  *
  98  * Thread-safety
  99  * =============
 100  *
 101  * When locked properly, the classifier is thread safe as long as the following
 102  * conditions are satisfied.
 103  * - Only the main thread calls functions requiring a write lock.
 104  * - Only the main thread is allowed to iterate over rules. */
 105
 106 #include "flow.h"
 107 #include "hmap.h"
 108 #include "list.h"
 109 #include "match.h"
 110 #include "tag.h"
 111 #include "openflow/nicira-ext.h"
 112 #include "openflow/openflow.h"
 113 #include "ovs-thread.h"
 114 #include "util.h"
 115
 116 #ifdef __cplusplus
 117 extern "C" {
 118 #endif
 119
 120 /* Needed only for the lock annotation in struct classifier. */
 121 extern struct ovs_mutex ofproto_mutex;
 122
 123 /* A flow classifier. */
 124 struct classifier {
 125     int n_rules;                /* Total number of rules. */
 126     struct hmap subtables;      /* Contains "struct cls_subtable"s.  */
 127     struct list subtables_priority; /* Subtables in descending priority order.
 128                                      */
 129     struct hmap partitions;     /* Contains "struct cls_partition"s. */
 130     struct ovs_rwlock rwlock OVS_ACQ_AFTER(ofproto_mutex);
 131 };
 132
 133 /* A set of rules that all have the same fields wildcarded. */
 134 struct cls_subtable {
 135     struct hmap_node hmap_node; /* Within struct classifier 'subtables' hmap.
 136                                  */
 137     struct list list_node;      /* Within classifier 'subtables_priority' list.
 138                                  */
 139     struct hmap rules;          /* Contains "struct cls_rule"s. */
 140     struct minimask mask;       /* Wildcards for fields. */
 141     int n_rules;                /* Number of rules, including duplicates. */
 142     unsigned int max_priority;  /* Max priority of any rule in the subtable. */
 143     unsigned int max_count;     /* Count of max_priority rules. */
 144     tag_type tag;               /* Tag generated from mask for partitioning. */
 145 };
 146
 147 /* Returns true if 'table' is a "catch-all" subtable that will match every
 148  * packet (if there is no higher-priority match). */
 149 static inline bool
 150 cls_subtable_is_catchall(const struct cls_subtable *subtable)
 151 {
 152     return minimask_is_catchall(&subtable->mask);
 153 }
 154
 155 /* A rule in a "struct cls_subtable". */
 156 struct cls_rule {
 157     struct hmap_node hmap_node; /* Within struct cls_subtable 'rules'. */
 158     struct list list;           /* List of identical, lower-priority rules. */
 159     struct minimatch match;     /* Matching rule. */
 160     unsigned int priority;      /* Larger numbers are higher priorities. */
 161     struct cls_partition *partition;
 162 };
 163
 164 /* Associates a metadata value (that is, a value of the OpenFlow 1.1+ metadata
 165  * field) with tags for the "cls_subtable"s that contain rules that match that
 166  * metadata value.  */
 167 struct cls_partition {
 168     struct hmap_node hmap_node; /* In struct classifier's 'partitions' hmap. */
 169     ovs_be64 metadata;          /* metadata value for this partition. */
 170     tag_type tags;              /* OR of each flow's cls_subtable tag. */
 171     struct tag_tracker tracker; /* Tracks the bits in 'tags'. */
 172 };
 173
 174 void cls_rule_init(struct cls_rule *, const struct match *,
 175                    unsigned int priority);
 176 void cls_rule_init_from_minimatch(struct cls_rule *, const struct minimatch *,
 177                                   unsigned int priority);
 178 void cls_rule_clone(struct cls_rule *, const struct cls_rule *);
 179 void cls_rule_move(struct cls_rule *dst, struct cls_rule *src);
 180 void cls_rule_destroy(struct cls_rule *);
 181
 182 bool cls_rule_equal(const struct cls_rule *, const struct cls_rule *);
 183 uint32_t cls_rule_hash(const struct cls_rule *, uint32_t basis);
 184
 185 void cls_rule_format(const struct cls_rule *, struct ds *);
 186
 187 bool cls_rule_is_catchall(const struct cls_rule *);
 188
 189 bool cls_rule_is_loose_match(const struct cls_rule *rule,
 190                              const struct minimatch *criteria);
 191
 192 void classifier_init(struct classifier *cls);
 193 void classifier_destroy(struct classifier *);
 194 bool classifier_is_empty(const struct classifier *cls)
 195     OVS_REQ_RDLOCK(cls->rwlock);
 196 int classifier_count(const struct classifier *cls)
 197     OVS_REQ_RDLOCK(cls->rwlock);
 198 void classifier_insert(struct classifier *cls, struct cls_rule *)
 199     OVS_REQ_WRLOCK(cls->rwlock);
 200 struct cls_rule *classifier_replace(struct classifier *cls, struct cls_rule *)
 201     OVS_REQ_WRLOCK(cls->rwlock);
 202 void classifier_remove(struct classifier *cls, struct cls_rule *)
 203     OVS_REQ_WRLOCK(cls->rwlock);
 204 struct cls_rule *classifier_lookup(const struct classifier *cls,
 205                                    const struct flow *,
 206                                    struct flow_wildcards *)
 207     OVS_REQ_RDLOCK(cls->rwlock);
 208 bool classifier_rule_overlaps(const struct classifier *cls,
 209                               const struct cls_rule *)
 210     OVS_REQ_RDLOCK(cls->rwlock);
 211
 212 typedef void cls_cb_func(struct cls_rule *, void *aux);
 213
 214 struct cls_rule *classifier_find_rule_exactly(const struct classifier *cls,
 215                                               const struct cls_rule *)
 216     OVS_REQ_RDLOCK(cls->rwlock);
 217 struct cls_rule *classifier_find_match_exactly(const struct classifier *cls,
 218                                                const struct match *,
 219                                                unsigned int priority)
 220     OVS_REQ_RDLOCK(cls->rwlock);
 221 \f
 222 /* Iteration. */
 223
 224 struct cls_cursor {
 225     const struct classifier *cls;
 226     const struct cls_subtable *subtable;
 227     const struct cls_rule *target;
 228 };
 229
 230 void cls_cursor_init(struct cls_cursor *cursor, const struct classifier *cls,
 231                      const struct cls_rule *match) OVS_REQ_RDLOCK(cls->rwlock);
 232 struct cls_rule *cls_cursor_first(struct cls_cursor *cursor);
 233 struct cls_rule *cls_cursor_next(struct cls_cursor *, const struct cls_rule *);
 234
 235 #define CLS_CURSOR_FOR_EACH(RULE, MEMBER, CURSOR)                       \
 236     for (ASSIGN_CONTAINER(RULE, cls_cursor_first(CURSOR), MEMBER);      \
 237          RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER);                 \
 238          ASSIGN_CONTAINER(RULE, cls_cursor_next(CURSOR, &(RULE)->MEMBER), \
 239                           MEMBER))
 240
 241 #define CLS_CURSOR_FOR_EACH_SAFE(RULE, NEXT, MEMBER, CURSOR)            \
 242     for (ASSIGN_CONTAINER(RULE, cls_cursor_first(CURSOR), MEMBER);      \
 243          (RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER)                 \
 244           ? ASSIGN_CONTAINER(NEXT, cls_cursor_next(CURSOR, &(RULE)->MEMBER), \
 245                              MEMBER), 1                                 \
 246           : 0);                                                         \
 247          (RULE) = (NEXT))
 248
 249 #ifdef __cplusplus
 250 }
 251 #endif
 252
 253 #endif /* classifier.h */