X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fclassifier.h;h=6f8c186d43cf640bbba79d494cf96c8226b4cd43;hb=b55f2f799b6340a89fd282ac28f6eff8d8492bf5;hp=ead087b9ee5574a8e44e14412b83b3d1505dd887;hpb=9850cd0ff6a08945f57462fb33fbe785edbeb60f;p=sliver-openvswitch.git

diff --git a/lib/classifier.h b/lib/classifier.h
index ead087b9e..6f8c186d4 100644
--- a/lib/classifier.h
+++ b/lib/classifier.h
@@ -19,24 +19,93 @@
 
 /* Flow classifier.
  *
- * A classifier is a "struct classifier",
- *      a hash map from a set of wildcards to a "struct cls_table",
- *              a hash map from fixed field values to "struct cls_rule",
- *                      which can contain a list of otherwise identical rules
- *                      with lower priorities.
+ *
+ * What?
+ * =====
+ *
+ * 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.
+ *
+ * Each OpenFlow table is implemented as a flow classifier.
+ *
+ *
+ * Basic 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
+ * and wildcarded all the other fields.  Then the obvious way to implement a
+ * classifier would be a hash table on the source and destination Ethernet
+ * addresses.  If new classification rules came along with a different form,
+ * you could add a second hash table that hashed on the fields matched in those
+ * rules.  With two hash tables, you look up a given flow in each hash table.
+ * If there are no matches, the classifier didn't contain a match; if you find
+ * a match in one of them, that's the result; if you find a match in both of
+ * them, then the result is the rule with the higher priority.
+ *
+ * This is how the classifier works.  In a "struct classifier", each form of
+ * "struct cls_rule" present (based on its ->match.mask) goes into a separate
+ * "struct cls_subtable".  A lookup does a hash lookup in every "struct
+ * 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.
+ *
+ * One detail: a classifier can contain multiple rules that are identical other
+ * than their priority.  When this happens, only the highest priority rule out
+ * of a group of otherwise identical rules is stored directly in the "struct
+ * cls_subtable", with the other almost-identical rules chained off a linked
+ * list inside that highest-priority rule.
+ *
+ *
+ * Partitioning
+ * ============
+ *
+ * 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
+ * named "metadata") distinguishing between the different stages.  For example,
+ * metadata value 1 might identify ingress rules, metadata value 2 might
+ * identify ACLs, and metadata value 3 might identify egress rules.  Such a
+ * classifier is essentially partitioned into multiple sub-classifiers on the
+ * basis of the metadata value.
+ *
+ * The classifier has a special optimization to speed up matching in this
+ * scenario:
+ *
+ *     - Each cls_subtable that matches on metadata gets a tag derived from the
+ *       subtable's mask, so that it is likely that each subtable has a unique
+ *       tag.  (Duplicate tags have a performance cost but do not affect
+ *       correctness.)
+ *
+ *     - For each metadata value matched by any cls_rule, the classifier
+ *       constructs a "struct cls_partition" indexed by the metadata value.
+ *       The cls_partition has a 'tags' member whose value is the bitwise-OR of
+ *       the tags of each cls_subtable that contains any rule that matches on
+ *       the cls_partition's metadata value.  In other words, struct
+ *       cls_partition associates metadata values with subtables that need to
+ *       be checked with flows with that specific metadata value.
+ *
+ * Thus, a flow lookup can start by looking up the partition associated with
+ * the flow's metadata, and then skip over any cls_subtable whose 'tag' does
+ * not intersect the partition's 'tags'.  (The flow must also be looked up in
+ * 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.)
+ *
  *
  * Thread-safety
  * =============
  *
- * When locked properly, the classifier is thread safe as long as the following
- * conditions are satisfied.
- * - Only the main thread calls functions requiring a write lock.
- * - Only the main thread is allowed to iterate over rules. */
+ * The classifier may safely be accessed by many reader threads concurrently or
+ * by a single writer. */
 
 #include "flow.h"
 #include "hmap.h"
 #include "list.h"
 #include "match.h"
+#include "tag.h"
 #include "openflow/nicira-ext.h"
 #include "openflow/openflow.h"
 #include "ovs-thread.h"
@@ -46,39 +115,58 @@
 extern "C" {
 #endif
 
+/* Needed only for the lock annotation in struct classifier. */
+extern struct ovs_mutex ofproto_mutex;
+
 /* A flow classifier. */
 struct classifier {
     int n_rules;                /* Total number of rules. */
-    struct hmap tables;         /* Contains "struct cls_table"s.  */
-    struct list tables_priority; /* Tables in descending priority order */
-    struct ovs_rwlock rwlock;
+    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);
 };
 
 /* A set of rules that all have the same fields wildcarded. */
-struct cls_table {
-    struct hmap_node hmap_node; /* Within struct classifier 'tables' hmap. */
-    struct list list_node;      /* Within classifier 'tables_priority_list' */
+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_table_rules;          /* Number of rules, including duplicates. */
-    unsigned int max_priority;  /* Max priority of any rule in the table. */
+    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. */
 };
 
-/* Returns true if 'table' is a "catch-all" table that will match every
+/* 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_table_is_catchall(const struct cls_table *table)
+cls_subtable_is_catchall(const struct cls_subtable *subtable)
 {
-    return minimask_is_catchall(&table->mask);
+    return minimask_is_catchall(&subtable->mask);
 }
 
-/* A rule in a "struct classifier". */
+/* A rule in a "struct cls_subtable". */
 struct cls_rule {
-    struct hmap_node hmap_node; /* Within struct cls_table 'rules'. */
+    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;
+};
+
+/* 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 *,
@@ -133,14 +221,14 @@ struct cls_rule *classifier_find_match_exactly(const struct classifier *cls,
 
 struct cls_cursor {
     const struct classifier *cls;
-    const struct cls_table *table;
+    const struct cls_subtable *subtable;
     const struct cls_rule *target;
 };
 
 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 *cursor, const struct cls_rule *);
+struct cls_rule *cls_cursor_next(struct cls_cursor *, const struct cls_rule *);
 
 #define CLS_CURSOR_FOR_EACH(RULE, MEMBER, CURSOR)                       \
     for (ASSIGN_CONTAINER(RULE, cls_cursor_first(CURSOR), MEMBER);      \