ovs/lib/classifier.c

/*
 * Copyright (c) 2009, 2010, 2011, 2012 Nicira, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <config.h>
#include "classifier.h"
#include <assert.h>
#include <errno.h>
#include <netinet/in.h>
#include "byte-order.h"
#include "dynamic-string.h"
#include "flow.h"
#include "hash.h"
#include "odp-util.h"
#include "ofp-util.h"
#include "packets.h"

static struct cls_table *find_table(const struct classifier *,
                                    const struct flow_wildcards *);
static struct cls_table *insert_table(struct classifier *,
                                      const struct flow_wildcards *);

static void destroy_table(struct classifier *, struct cls_table *);

static struct cls_rule *find_match(const struct cls_table *,
                                   const struct flow *);
static struct cls_rule *find_equal(struct cls_table *, const struct flow *,
                                   uint32_t hash);
static struct cls_rule *insert_rule(struct cls_table *, struct cls_rule *);

/* Iterates RULE over HEAD and all of the cls_rules on HEAD->list. */
#define FOR_EACH_RULE_IN_LIST(RULE, HEAD)                               \
    for ((RULE) = (HEAD); (RULE) != NULL; (RULE) = next_rule_in_list(RULE))
#define FOR_EACH_RULE_IN_LIST_SAFE(RULE, NEXT, HEAD)                    \
    for ((RULE) = (HEAD);                                               \
         (RULE) != NULL && ((NEXT) = next_rule_in_list(RULE), true);    \
         (RULE) = (NEXT))

static struct cls_rule *next_rule_in_list__(struct cls_rule *);
static struct cls_rule *next_rule_in_list(struct cls_rule *);

/* cls_rule. */

/* Initializes 'rule' to match packets specified by 'match' at the given
 * 'priority'.
 *
 * The caller must eventually destroy 'rule' with cls_rule_destroy().
 *
 * 'match' must satisfy the invariant described in the comment at the
 * definition of struct match.
 *
 * (OpenFlow uses priorities between 0 and UINT16_MAX, inclusive, but
 * internally Open vSwitch supports a wider range.) */
void
cls_rule_init(struct cls_rule *rule,
              const struct match *match, unsigned int priority)
{
    rule->match = *match;
    rule->priority = priority;
}

/* Initializes 'dst' as a copy of 'src'.
 *
 * The caller must eventually destroy 'rule' with cls_rule_destroy(). */
void
cls_rule_clone(struct cls_rule *dst, const struct cls_rule *src)
{
    *dst = *src;
}

/* Frees memory referenced by 'rule'.  Doesn't free 'rule' itself (it's
 * normally embedded into a larger structure).
 *
 * ('rule' must not currently be in a classifier.) */
void
cls_rule_destroy(struct cls_rule *rule OVS_UNUSED)
{
    /* Nothing to do yet. */
}

/* Returns true if 'a' and 'b' match the same packets at the same priority,
 * false if they differ in some way. */
bool
cls_rule_equal(const struct cls_rule *a, const struct cls_rule *b)
{
    return a->priority == b->priority && match_equal(&a->match, &b->match);
}

/* Returns a hash value for 'rule', folding in 'basis'. */
uint32_t
cls_rule_hash(const struct cls_rule *rule, uint32_t basis)
{
    return match_hash(&rule->match, hash_int(rule->priority, basis));
}

/* Appends a string describing 'rule' to 's'. */
void
cls_rule_format(const struct cls_rule *rule, struct ds *s)
{
    match_format(&rule->match, s, rule->priority);
}

/* Initializes 'cls' as a classifier that initially contains no classification
 * rules. */
void
classifier_init(struct classifier *cls)
{
    cls->n_rules = 0;
    hmap_init(&cls->tables);
}

/* Destroys 'cls'.  Rules within 'cls', if any, are not freed; this is the
 * caller's responsibility. */
void
classifier_destroy(struct classifier *cls)
{
    if (cls) {
        struct cls_table *table, *next_table;

        HMAP_FOR_EACH_SAFE (table, next_table, hmap_node, &cls->tables) {
            hmap_destroy(&table->rules);
            hmap_remove(&cls->tables, &table->hmap_node);
            free(table);
        }
        hmap_destroy(&cls->tables);
    }
}

/* Returns true if 'cls' contains no classification rules, false otherwise. */
bool
classifier_is_empty(const struct classifier *cls)
{
    return cls->n_rules == 0;
}

/* Returns the number of rules in 'cls'. */
int
classifier_count(const struct classifier *cls)
{
    return cls->n_rules;
}

/* Inserts 'rule' into 'cls'.  Until 'rule' is removed from 'cls', the caller
 * must not modify or free it.
 *
 * If 'cls' already contains an identical rule (including wildcards, values of
 * fixed fields, and priority), replaces the old rule by 'rule' and returns the
 * rule that was replaced.  The caller takes ownership of the returned rule and
 * is thus responsible for destroying it with cls_rule_destroy(), freeing the
 * memory block in which it resides, etc., as necessary.
 *
 * Returns NULL if 'cls' does not contain a rule with an identical key, after
 * inserting the new rule.  In this case, no rules are displaced by the new
 * rule, even rules that cannot have any effect because the new rule matches a
 * superset of their flows and has higher priority. */
struct cls_rule *
classifier_replace(struct classifier *cls, struct cls_rule *rule)
{
    struct cls_rule *old_rule;
    struct cls_table *table;

    table = find_table(cls, &rule->match.wc);
    if (!table) {
        table = insert_table(cls, &rule->match.wc);
    }

    old_rule = insert_rule(table, rule);
    if (!old_rule) {
        table->n_table_rules++;
        cls->n_rules++;
    }
    return old_rule;
}

/* Inserts 'rule' into 'cls'.  Until 'rule' is removed from 'cls', the caller
 * must not modify or free it.
 *
 * 'cls' must not contain an identical rule (including wildcards, values of
 * fixed fields, and priority).  Use classifier_find_rule_exactly() to find
 * such a rule. */
void
classifier_insert(struct classifier *cls, struct cls_rule *rule)
{
    struct cls_rule *displaced_rule = classifier_replace(cls, rule);
    assert(!displaced_rule);
}

/* Removes 'rule' from 'cls'.  It is the caller's responsibility to destroy
 * 'rule' with cls_rule_destroy(), freeing the memory block in which 'rule'
 * resides, etc., as necessary. */
void
classifier_remove(struct classifier *cls, struct cls_rule *rule)
{
    struct cls_rule *head;
    struct cls_table *table;

    table = find_table(cls, &rule->match.wc);
    head = find_equal(table, &rule->match.flow, rule->hmap_node.hash);
    if (head != rule) {
        list_remove(&rule->list);
    } else if (list_is_empty(&rule->list)) {
        hmap_remove(&table->rules, &rule->hmap_node);
    } else {
        struct cls_rule *next = CONTAINER_OF(rule->list.next,
                                             struct cls_rule, list);

        list_remove(&rule->list);
        hmap_replace(&table->rules, &rule->hmap_node, &next->hmap_node);
    }

    if (--table->n_table_rules == 0) {
        destroy_table(cls, table);
    }

    cls->n_rules--;
}

/* Finds and returns the highest-priority rule in 'cls' that matches 'flow'.
 * Returns a null pointer if no rules in 'cls' match 'flow'.  If multiple rules
 * of equal priority match 'flow', returns one arbitrarily. */
struct cls_rule *
classifier_lookup(const struct classifier *cls, const struct flow *flow)
{
    struct cls_table *table;
    struct cls_rule *best;

    best = NULL;
    HMAP_FOR_EACH (table, hmap_node, &cls->tables) {
        struct cls_rule *rule = find_match(table, flow);
        if (rule && (!best || rule->priority > best->priority)) {
            best = rule;
        }
    }
    return best;
}

/* Finds and returns a rule in 'cls' with exactly the same priority and
 * matching criteria as 'target'.  Returns a null pointer if 'cls' doesn't
 * contain an exact match. */
struct cls_rule *
classifier_find_rule_exactly(const struct classifier *cls,
                             const struct cls_rule *target)
{
    struct cls_rule *head, *rule;
    struct cls_table *table;

    table = find_table(cls, &target->match.wc);
    if (!table) {
        return NULL;
    }

    head = find_equal(table, &target->match.flow,
                      flow_hash(&target->match.flow, 0));
    FOR_EACH_RULE_IN_LIST (rule, head) {
        if (target->priority >= rule->priority) {
            return target->priority == rule->priority ? rule : NULL;
        }
    }
    return NULL;
}

/* Finds and returns a rule in 'cls' with priority 'priority' and exactly the
 * same matching criteria as 'target'.  Returns a null pointer if 'cls' doesn't
 * contain an exact match. */
struct cls_rule *
classifier_find_match_exactly(const struct classifier *cls,
                              const struct match *target,
                              unsigned int priority)
{
    struct cls_rule *retval;
    struct cls_rule cr;

    cls_rule_init(&cr, target, priority);
    retval = classifier_find_rule_exactly(cls, &cr);
    cls_rule_destroy(&cr);

    return retval;
}

/* Checks if 'target' would overlap any other rule in 'cls'.  Two rules are
 * considered to overlap if both rules have the same priority and a packet
 * could match both. */
bool
classifier_rule_overlaps(const struct classifier *cls,
                         const struct cls_rule *target)
{
    struct cls_table *table;

    HMAP_FOR_EACH (table, hmap_node, &cls->tables) {
        struct flow_wildcards wc;
        struct cls_rule *head;

        flow_wildcards_combine(&wc, &target->match.wc, &table->wc);
        HMAP_FOR_EACH (head, hmap_node, &table->rules) {
            struct cls_rule *rule;

            FOR_EACH_RULE_IN_LIST (rule, head) {
                if (rule->priority == target->priority
                    && flow_equal_except(&target->match.flow,
                                         &rule->match.flow, &wc)) {
                    return true;
                }
            }
        }
    }

    return false;
}

/* Returns true if 'rule' exactly matches 'criteria' or if 'rule' is more
 * specific than 'criteria'.  That is, 'rule' matches 'criteria' and this
 * function returns true if, for every field:
 *
 *   - 'criteria' and 'rule' specify the same (non-wildcarded) value for the
 *     field, or
 *
 *   - 'criteria' wildcards the field,
 *
 * Conversely, 'rule' does not match 'criteria' and this function returns false
 * if, for at least one field:
 *
 *   - 'criteria' and 'rule' specify different values for the field, or
 *
 *   - 'criteria' specifies a value for the field but 'rule' wildcards it.
 *
 * Equivalently, the truth table for whether a field matches is:
 *
 *                                     rule
 *
 *                   c         wildcard    exact
 *                   r        +---------+---------+
 *                   i   wild |   yes   |   yes   |
 *                   t   card |         |         |
 *                   e        +---------+---------+
 *                   r  exact |    no   |if values|
 *                   i        |         |are equal|
 *                   a        +---------+---------+
 *
 * This is the matching rule used by OpenFlow 1.0 non-strict OFPT_FLOW_MOD
 * commands and by OpenFlow 1.0 aggregate and flow stats.
 *
 * Ignores rule->priority. */
bool
cls_rule_is_loose_match(const struct cls_rule *rule,
                        const struct match *criteria)
{
    return (!flow_wildcards_has_extra(&rule->match.wc, &criteria->wc)
            && flow_equal_except(&rule->match.flow, &criteria->flow,
                                 &criteria->wc));
}

/* Iteration. */

static bool
rule_matches(const struct cls_rule *rule, const struct cls_rule *target)
{
    return (!target
            || flow_equal_except(&rule->match.flow, &target->match.flow,
                                 &target->match.wc));
}

static struct cls_rule *
search_table(const struct cls_table *table, const struct cls_rule *target)
{
    if (!target || !flow_wildcards_has_extra(&table->wc, &target->match.wc)) {
        struct cls_rule *rule;

        HMAP_FOR_EACH (rule, hmap_node, &table->rules) {
            if (rule_matches(rule, target)) {
                return rule;
            }
        }
    }
    return NULL;
}

/* Initializes 'cursor' for iterating through rules in 'cls':
 *
 *     - If 'target' is null, the cursor will visit every rule in 'cls'.
 *
 *     - If 'target' is nonnull, the cursor will visit each 'rule' in 'cls'
 *       such that cls_rule_is_loose_match(rule, target) returns true.
 *
 * Ignores target->priority. */
void
cls_cursor_init(struct cls_cursor *cursor, const struct classifier *cls,
                const struct cls_rule *target)
{
    cursor->cls = cls;
    cursor->target = target;
}

/* Returns the first matching cls_rule in 'cursor''s iteration, or a null
 * pointer if there are no matches. */
struct cls_rule *
cls_cursor_first(struct cls_cursor *cursor)
{
    struct cls_table *table;

    HMAP_FOR_EACH (table, hmap_node, &cursor->cls->tables) {
        struct cls_rule *rule = search_table(table, cursor->target);
        if (rule) {
            cursor->table = table;
            return rule;
        }
    }

    return NULL;
}

/* Returns the next matching cls_rule in 'cursor''s iteration, or a null
 * pointer if there are no more matches. */
struct cls_rule *
cls_cursor_next(struct cls_cursor *cursor, struct cls_rule *rule)
{
    const struct cls_table *table;
    struct cls_rule *next;

    next = next_rule_in_list__(rule);
    if (next->priority < rule->priority) {
        return next;
    }

    /* 'next' is the head of the list, that is, the rule that is included in
     * the table's hmap.  (This is important when the classifier contains rules
     * that differ only in priority.) */
    rule = next;
    HMAP_FOR_EACH_CONTINUE (rule, hmap_node, &cursor->table->rules) {
        if (rule_matches(rule, cursor->target)) {
            return rule;
        }
    }

    table = cursor->table;
    HMAP_FOR_EACH_CONTINUE (table, hmap_node, &cursor->cls->tables) {
        rule = search_table(table, cursor->target);
        if (rule) {
            cursor->table = table;
            return rule;
        }
    }

    return NULL;
}

static struct cls_table *
find_table(const struct classifier *cls, const struct flow_wildcards *wc)
{
    struct cls_table *table;

    HMAP_FOR_EACH_IN_BUCKET (table, hmap_node, flow_wildcards_hash(wc, 0),
                             &cls->tables) {
        if (flow_wildcards_equal(wc, &table->wc)) {
            return table;
        }
    }
    return NULL;
}

static struct cls_table *
insert_table(struct classifier *cls, const struct flow_wildcards *wc)
{
    struct cls_table *table;

    table = xzalloc(sizeof *table);
    hmap_init(&table->rules);
    table->wc = *wc;
    table->is_catchall = flow_wildcards_is_catchall(&table->wc);
    hmap_insert(&cls->tables, &table->hmap_node, flow_wildcards_hash(wc, 0));

    return table;
}

static void
destroy_table(struct classifier *cls, struct cls_table *table)
{
    hmap_remove(&cls->tables, &table->hmap_node);
    hmap_destroy(&table->rules);
    free(table);
}

static struct cls_rule *
find_match(const struct cls_table *table, const struct flow *flow)
{
    struct cls_rule *rule;

    if (table->is_catchall) {
        HMAP_FOR_EACH (rule, hmap_node, &table->rules) {
            return rule;
        }
    } else {
        struct flow f;

        f = *flow;
        flow_zero_wildcards(&f, &table->wc);
        HMAP_FOR_EACH_WITH_HASH (rule, hmap_node, flow_hash(&f, 0),
                                 &table->rules) {
            if (flow_equal(&f, &rule->match.flow)) {
                return rule;
            }
        }
    }

    return NULL;
}

static struct cls_rule *
find_equal(struct cls_table *table, const struct flow *flow, uint32_t hash)
{
    struct cls_rule *head;

    HMAP_FOR_EACH_WITH_HASH (head, hmap_node, hash, &table->rules) {
        if (flow_equal(&head->match.flow, flow)) {
            return head;
        }
    }
    return NULL;
}

static struct cls_rule *
insert_rule(struct cls_table *table, struct cls_rule *new)
{
    struct cls_rule *head;

    new->hmap_node.hash = flow_hash(&new->match.flow, 0);

    head = find_equal(table, &new->match.flow, new->hmap_node.hash);
    if (!head) {
        hmap_insert(&table->rules, &new->hmap_node, new->hmap_node.hash);
        list_init(&new->list);
        return NULL;
    } else {
        /* Scan the list for the insertion point that will keep the list in
         * order of decreasing priority. */
        struct cls_rule *rule;
        FOR_EACH_RULE_IN_LIST (rule, head) {
            if (new->priority >= rule->priority) {
                if (rule == head) {
                    /* 'new' is the new highest-priority flow in the list. */
                    hmap_replace(&table->rules,
                                 &rule->hmap_node, &new->hmap_node);
                }

                if (new->priority == rule->priority) {
                    list_replace(&new->list, &rule->list);
                    return rule;
                } else {
                    list_insert(&rule->list, &new->list);
                    return NULL;
                }
            }
        }

        /* Insert 'new' at the end of the list. */
        list_push_back(&head->list, &new->list);
        return NULL;
    }
}

static struct cls_rule *
next_rule_in_list__(struct cls_rule *rule)
{
    struct cls_rule *next = OBJECT_CONTAINING(rule->list.next, next, list);
    return next;
}

static struct cls_rule *
next_rule_in_list(struct cls_rule *rule)
{
    struct cls_rule *next = next_rule_in_list__(rule);
    return next->priority < rule->priority ? next : NULL;
}