ofproto: Make ->construct() and ->destruct() more symmetrical.

[sliver-openvswitch.git] / ofproto / ofproto-provider.h

/*
 * Copyright (c) 2009, 2010, 2011 Nicira Networks.
 *
 * 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.
 */

#ifndef OFPROTO_OFPROTO_PROVIDER_H
#define OFPROTO_OFPROTO_PROVIDER_H 1

/* Definitions for use within ofproto. */

#include "ofproto/ofproto.h"
#include "classifier.h"
#include "list.h"
#include "shash.h"
#include "timeval.h"

/* An OpenFlow switch.
 *
 * With few exceptions, ofproto implementations may look at these fields but
 * should not modify them. */
struct ofproto {
    const struct ofproto_class *ofproto_class;
    char *type;                 /* Datapath type. */
    char *name;                 /* Datapath name. */
    struct hmap_node hmap_node; /* In global 'all_ofprotos' hmap. */

    /* Settings. */
    uint64_t fallback_dpid;     /* Datapath ID if no better choice found. */
    uint64_t datapath_id;       /* Datapath ID. */
    unsigned flow_eviction_threshold; /* Threshold at which to begin flow
                                       * table eviction. Only affects the
                                       * ofproto-dpif implementation */
    char *mfr_desc;             /* Manufacturer. */
    char *hw_desc;              /* Hardware. */
    char *sw_desc;              /* Software version. */
    char *serial_desc;          /* Serial number. */
    char *dp_desc;              /* Datapath description. */

    /* Datapath. */
    struct hmap ports;          /* Contains "struct ofport"s. */
    struct shash port_by_name;

    /* Flow tables. */
    struct classifier *tables;  /* Each classifier contains "struct rule"s. */
    int n_tables;

    /* OpenFlow connections. */
    struct connmgr *connmgr;

    /* Flow table operation tracking. */
    int state;                  /* Internal state. */
    struct list pending;        /* List of "struct ofopgroup"s. */
    struct hmap deletions;      /* All OFOPERATION_DELETE "ofoperation"s. */
};

struct ofproto *ofproto_lookup(const char *name);
struct ofport *ofproto_get_port(const struct ofproto *, uint16_t ofp_port);

/* An OpenFlow port within a "struct ofproto".
 *
 * With few exceptions, ofproto implementations may look at these fields but
 * should not modify them. */
struct ofport {
    struct ofproto *ofproto;    /* The ofproto that contains this port. */
    struct hmap_node hmap_node; /* In struct ofproto's "ports" hmap. */
    struct netdev *netdev;
    struct ofp_phy_port opp;
    uint16_t ofp_port;          /* OpenFlow port number. */
    unsigned int change_seq;
};

/* An OpenFlow flow within a "struct ofproto".
 *
 * With few exceptions, ofproto implementations may look at these fields but
 * should not modify them. */
struct rule {
    struct ofproto *ofproto;     /* The ofproto that contains this rule. */
    struct list ofproto_node;    /* Owned by ofproto base code. */
    struct cls_rule cr;          /* In owning ofproto's classifier. */

    struct ofoperation *pending; /* Operation now in progress, if nonnull. */

    ovs_be64 flow_cookie;        /* Controller-issued identifier. */

    long long int created;       /* Creation time. */
    uint16_t idle_timeout;       /* In seconds from time of last use. */
    uint16_t hard_timeout;       /* In seconds from time of creation. */
    uint8_t table_id;            /* Index in ofproto's 'tables' array. */
    bool send_flow_removed;      /* Send a flow removed message? */

    union ofp_action *actions;   /* OpenFlow actions. */
    int n_actions;               /* Number of elements in actions[]. */
};

static inline struct rule *
rule_from_cls_rule(const struct cls_rule *cls_rule)
{
    return cls_rule ? CONTAINER_OF(cls_rule, struct rule, cr) : NULL;
}

void ofproto_rule_expire(struct rule *, uint8_t reason);
void ofproto_rule_destroy(struct rule *);

void ofoperation_complete(struct ofoperation *, int status);
struct rule *ofoperation_get_victim(struct ofoperation *);

/* ofproto class structure, to be defined by each ofproto implementation.
 *
 *
 * Data Structures
 * ===============
 *
 * These functions work primarily with three different kinds of data
 * structures:
 *
 *   - "struct ofproto", which represents an OpenFlow switch.
 *
 *   - "struct ofport", which represents a port within an ofproto.
 *
 *   - "struct rule", which represents an OpenFlow flow within an ofproto.
 *
 * Each of these data structures contains all of the implementation-independent
 * generic state for the respective concept, called the "base" state.  None of
 * them contains any extra space for ofproto implementations to use.  Instead,
 * each implementation is expected to declare its own data structure that
 * contains an instance of the generic data structure plus additional
 * implementation-specific members, called the "derived" state.  The
 * implementation can use casts or (preferably) the CONTAINER_OF macro to
 * obtain access to derived state given only a pointer to the embedded generic
 * data structure.
 *
 *
 * Life Cycle
 * ==========
 *
 * Four stylized functions accompany each of these data structures:
 *
 *            "alloc"       "construct"       "destruct"       "dealloc"
 *            ------------  ----------------  ---------------  --------------
 *   ofproto  ->alloc       ->construct       ->destruct       ->dealloc
 *   ofport   ->port_alloc  ->port_construct  ->port_destruct  ->port_dealloc
 *   rule     ->rule_alloc  ->rule_construct  ->rule_destruct  ->rule_dealloc
 *
 * Any instance of a given data structure goes through the following life
 * cycle:
 *
 *   1. The client calls the "alloc" function to obtain raw memory.  If "alloc"
 *      fails, skip all the other steps.
 *
 *   2. The client initializes all of the data structure's base state.  If this
 *      fails, skip to step 7.
 *
 *   3. The client calls the "construct" function.  The implementation
 *      initializes derived state.  It may refer to the already-initialized
 *      base state.  If "construct" fails, skip to step 6.
 *
 *   4. The data structure is now initialized and in use.
 *
 *   5. When the data structure is no longer needed, the client calls the
 *      "destruct" function.  The implementation uninitializes derived state.
 *      The base state has not been uninitialized yet, so the implementation
 *      may still refer to it.
 *
 *   6. The client uninitializes all of the data structure's base state.
 *
 *   7. The client calls the "dealloc" to free the raw memory.  The
 *      implementation must not refer to base or derived state in the data
 *      structure, because it has already been uninitialized.
 *
 * Each "alloc" function allocates and returns a new instance of the respective
 * data structure.  The "alloc" function is not given any information about the
 * use of the new data structure, so it cannot perform much initialization.
 * Its purpose is just to ensure that the new data structure has enough room
 * for base and derived state.  It may return a null pointer if memory is not
 * available, in which case none of the other functions is called.
 *
 * Each "construct" function initializes derived state in its respective data
 * structure.  When "construct" is called, all of the base state has already
 * been initialized, so the "construct" function may refer to it.  The
 * "construct" function is allowed to fail, in which case the client calls the
 * "dealloc" function (but not the "destruct" function).
 *
 * Each "destruct" function uninitializes and frees derived state in its
 * respective data structure.  When "destruct" is called, the base state has
 * not yet been uninitialized, so the "destruct" function may refer to it.  The
 * "destruct" function is not allowed to fail.
 *
 * Each "dealloc" function frees raw memory that was allocated by the the
 * "alloc" function.  The memory's base and derived members might not have ever
 * been initialized (but if "construct" returned successfully, then it has been
 * "destruct"ed already).  The "dealloc" function is not allowed to fail.
 *
 *
 * Conventions
 * ===========
 *
 * Most of these functions return 0 if they are successful or a positive error
 * code on failure.  Depending on the function, valid error codes are either
 * errno values or OpenFlow error codes constructed with ofp_mkerr().
 *
 * Most of these functions are expected to execute synchronously, that is, to
 * block as necessary to obtain a result.  Thus, these functions may return
 * EAGAIN (or EWOULDBLOCK or EINPROGRESS) only where the function descriptions
 * explicitly say those errors are a possibility.  We may relax this
 * requirement in the future if and when we encounter performance problems. */
struct ofproto_class {
/* ## ----------------- ## */
/* ## Factory Functions ## */
/* ## ----------------- ## */

    /* Enumerates the types of all support ofproto types into 'types'.  The
     * caller has already initialized 'types' and other ofproto classes might
     * already have added names to it. */
    void (*enumerate_types)(struct sset *types);

    /* Enumerates the names of all existing datapath of the specified 'type'
     * into 'names' 'all_dps'.  The caller has already initialized 'names' as
     * an empty sset.
     *
     * 'type' is one of the types enumerated by ->enumerate_types().
     *
     * Returns 0 if successful, otherwise a positive errno value.
     */
    int (*enumerate_names)(const char *type, struct sset *names);

    /* Deletes the datapath with the specified 'type' and 'name'.  The caller
     * should have closed any open ofproto with this 'type' and 'name'; this
     * function is allowed to fail if that is not the case.
     *
     * 'type' is one of the types enumerated by ->enumerate_types().
     * 'name' is one of the names enumerated by ->enumerate_names() for 'type'.
     *
     * Returns 0 if successful, otherwise a positive errno value.
     */
    int (*del)(const char *type, const char *name);

/* ## --------------------------- ## */
/* ## Top-Level ofproto Functions ## */
/* ## --------------------------- ## */

    /* Life-cycle functions for an "ofproto" (see "Life Cycle" above).
     *
     *
     * Construction
     * ============
     *
     * ->construct() should not modify any base members of the ofproto.  The
     * client will initialize the ofproto's 'ports' and 'tables' members after
     * construction is complete.
     *
     * When ->construct() is called, the client does not yet know how many flow
     * tables the datapath supports, so ofproto->n_tables will be 0 and
     * ofproto->tables will be NULL.  ->construct() should store the number of
     * flow tables supported by the datapath (between 1 and 255, inclusive)
     * into '*n_tables'.  After a successful return, the client will initialize
     * the base 'n_tables' member to '*n_tables' and allocate and initialize
     * the base 'tables' member as the specified number of empty flow tables.
     * Each flow table will be initially empty, so ->construct() should delete
     * flows from the underlying datapath, if necessary, rather than populating
     * the tables.
     *
     * Only one ofproto instance needs to be supported for any given datapath.
     * If a datapath is already open as part of one "ofproto", then another
     * attempt to "construct" the same datapath as part of another ofproto is
     * allowed to fail with an error.
     *
     * ->construct() returns 0 if successful, otherwise a positive errno
     * value.
     *
     *
     * Destruction
     * ===========
     *
     * If 'ofproto' has any pending asynchronous operations, ->destruct()
     * must complete all of them by calling ofoperation_complete().
     *
     * ->destruct() must also destroy all remaining rules in the ofproto's
     * tables, by passing each remaining rule to ofproto_rule_destroy().  The
     * client will destroy the flow tables themselves after ->destruct()
     * returns.
     */
    struct ofproto *(*alloc)(void);
    int (*construct)(struct ofproto *ofproto, int *n_tables);
    void (*destruct)(struct ofproto *ofproto);
    void (*dealloc)(struct ofproto *ofproto);

    /* Performs any periodic activity required by 'ofproto'.  It should:
     *
     *   - Call connmgr_send_packet_in() for each received packet that missed
     *     in the OpenFlow flow table or that had a OFPP_CONTROLLER output
     *     action.
     *
     *   - Call ofproto_rule_expire() for each OpenFlow flow that has reached
     *     its hard_timeout or idle_timeout, to expire the flow.
     *
     * Returns 0 if successful, otherwise a positive errno value.  The ENODEV
     * return value specifically means that the datapath underlying 'ofproto'
     * has been destroyed (externally, e.g. by an admin running ovs-dpctl).
     */
    int (*run)(struct ofproto *ofproto);

    /* Causes the poll loop to wake up when 'ofproto''s 'run' function needs to
     * be called, e.g. by calling the timer or fd waiting functions in
     * poll-loop.h.  */
    void (*wait)(struct ofproto *ofproto);

    /* Every "struct rule" in 'ofproto' is about to be deleted, one by one.
     * This function may prepare for that, for example by clearing state in
     * advance.  It should *not* actually delete any "struct rule"s from
     * 'ofproto', only prepare for it.
     *
     * This function is optional; it's really just for optimization in case
     * it's cheaper to delete all the flows from your hardware in a single pass
     * than to do it one by one. */
    void (*flush)(struct ofproto *ofproto);

    /* Helper for the OpenFlow OFPT_FEATURES_REQUEST request.
     *
     * The implementation should store true in '*arp_match_ip' if the switch
     * supports matching IP addresses inside ARP requests and replies, false
     * otherwise.
     *
     * The implementation should store in '*actions' a bitmap of the supported
     * OpenFlow actions: the bit with value (1 << n) should be set to 1 if the
     * implementation supports the action with value 'n', and to 0 otherwise.
     * For example, if the implementation supports the OFPAT_OUTPUT and
     * OFPAT_ENQUEUE actions, but no others, it would set '*actions' to (1 <<
     * OFPAT_OUTPUT) | (1 << OFPAT_ENQUEUE).  Vendor actions are not included
     * in '*actions'. */
    void (*get_features)(struct ofproto *ofproto,
                         bool *arp_match_ip, uint32_t *actions);

    /* Helper for the OpenFlow OFPST_TABLE statistics request.
     *
     * The 'ots' array contains 'ofproto->n_tables' elements.  Each element is
     * initialized as:
     *
     *   - 'table_id' to the array index.
     *
     *   - 'name' to "table#" where # is the table ID.
     *
     *   - 'wildcards' to OFPFW_ALL.
     *
     *   - 'max_entries' to 1,000,000.
     *
     *   - 'active_count' to the classifier_count() for the table.
     *
     *   - 'lookup_count' and 'matched_count' to 0.
     *
     * The implementation should update any members in each element for which
     * it has better values:
     *
     *   - 'name' to a more meaningful name.
     *
     *   - 'wildcards' to the set of wildcards actually supported by the table
     *     (if it doesn't support all OpenFlow wildcards).
     *
     *   - 'max_entries' to the maximum number of flows actually supported by
     *     the hardware.
     *
     *   - 'lookup_count' to the number of packets looked up in this flow table
     *     so far.
     *
     *   - 'matched_count' to the number of packets looked up in this flow
     *     table so far that matched one of the flow entries.
     *
     * Keep in mind that all of the members of struct ofp_table_stats are in
     * network byte order.
     */
    void (*get_tables)(struct ofproto *ofproto, struct ofp_table_stats *ots);

/* ## ---------------- ## */
/* ## ofport Functions ## */
/* ## ---------------- ## */

    /* Life-cycle functions for a "struct ofport" (see "Life Cycle" above).
     *
     * ->port_construct() should not modify any base members of the ofport.
     *
     * ofports are managed by the base ofproto code.  The ofproto
     * implementation should only create and destroy them in response to calls
     * to these functions.  The base ofproto code will create and destroy
     * ofports in the following situations:
     *
     *   - Just after the ->construct() function is called, the base ofproto
     *     iterates over all of the implementation's ports, using
     *     ->port_dump_start() and related functions, and constructs an ofport
     *     for each dumped port.
     *
     *   - If ->port_poll() reports that a specific port has changed, then the
     *     base ofproto will query that port with ->port_query_by_name() and
     *     construct or destruct ofports as necessary to reflect the updated
     *     set of ports.
     *
     *   - If ->port_poll() returns ENOBUFS to report an unspecified port set
     *     change, then the base ofproto will iterate over all of the
     *     implementation's ports, in the same way as at ofproto
     *     initialization, and construct and destruct ofports to reflect all of
     *     the changes.
     *
     * ->port_construct() returns 0 if successful, otherwise a positive errno
     * value.
     */
    struct ofport *(*port_alloc)(void);
    int (*port_construct)(struct ofport *ofport);
    void (*port_destruct)(struct ofport *ofport);
    void (*port_dealloc)(struct ofport *ofport);

    /* Called after 'ofport->netdev' is replaced by a new netdev object.  If
     * the ofproto implementation uses the ofport's netdev internally, then it
     * should switch to using the new one.  The old one has been closed.
     *
     * An ofproto implementation that doesn't need to do anything in this
     * function may use a null pointer. */
    void (*port_modified)(struct ofport *ofport);

    /* Called after an OpenFlow OFPT_PORT_MOD request changes a port's
     * configuration.  'ofport->opp.config' contains the new configuration.
     * 'old_config' contains the previous configuration.
     *
     * The caller implements OFPPC_PORT_DOWN using netdev functions to turn
     * NETDEV_UP on and off, so this function doesn't have to do anything for
     * that bit (and it won't be called if that is the only bit that
     * changes). */
    void (*port_reconfigured)(struct ofport *ofport, ovs_be32 old_config);

    /* Looks up a port named 'devname' in 'ofproto'.  On success, initializes
     * '*port' appropriately.
     *
     * The caller owns the data in 'port' and must free it with
     * ofproto_port_destroy() when it is no longer needed. */
    int (*port_query_by_name)(const struct ofproto *ofproto,
                              const char *devname, struct ofproto_port *port);

    /* Attempts to add 'netdev' as a port on 'ofproto'.  Returns 0 if
     * successful, otherwise a positive errno value.  If successful, sets
     * '*ofp_portp' to the new port's port number.
     *
     * It doesn't matter whether the new port will be returned by a later call
     * to ->port_poll(); the implementation may do whatever is more
     * convenient. */
    int (*port_add)(struct ofproto *ofproto, struct netdev *netdev,
                    uint16_t *ofp_portp);

    /* Deletes port number 'ofp_port' from the datapath for 'ofproto'.  Returns
     * 0 if successful, otherwise a positive errno value.
     *
     * It doesn't matter whether the new port will be returned by a later call
     * to ->port_poll(); the implementation may do whatever is more
     * convenient. */
    int (*port_del)(struct ofproto *ofproto, uint16_t ofp_port);

    /* Port iteration functions.
     *
     * The client might not be entirely in control of the ports within an
     * ofproto.  Some hardware implementations, for example, might have a fixed
     * set of ports in a datapath, and the Linux datapath allows the system
     * administrator to externally add and remove ports with ovs-dpctl.  For
     * this reason, the client needs a way to iterate through all the ports
     * that are actually in a datapath.  These functions provide that
     * functionality.
     *
     * The 'state' pointer provides the implementation a place to
     * keep track of its position.  Its format is opaque to the caller.
     *
     * The ofproto provider retains ownership of the data that it stores into
     * ->port_dump_next()'s 'port' argument.  The data must remain valid until
     * at least the next call to ->port_dump_next() or ->port_dump_done() for
     * 'state'.  The caller will not modify or free it.
     *
     * Details
     * =======
     *
     * ->port_dump_start() attempts to begin dumping the ports in 'ofproto'.
     * On success, it should return 0 and initialize '*statep' with any data
     * needed for iteration.  On failure, returns a positive errno value, and
     * the client will not call ->port_dump_next() or ->port_dump_done().
     *
     * ->port_dump_next() attempts to retrieve another port from 'ofproto' for
     * 'state'.  If there is another port, it should store the port's
     * information into 'port' and return 0.  It should return EOF if all ports
     * have already been iterated.  Otherwise, on error, it should return a
     * positive errno value.  This function will not be called again once it
     * returns nonzero once for a given iteration (but the 'port_dump_done'
     * function will be called afterward).
     *
     * ->port_dump_done() allows the implementation to release resources used
     * for iteration.  The caller might decide to stop iteration in the middle
     * by calling this function before ->port_dump_next() returns nonzero.
     *
     * Usage Example
     * =============
     *
     * int error;
     * void *state;
     *
     * error = ofproto->ofproto_class->port_dump_start(ofproto, &state);
     * if (!error) {
     *     for (;;) {
     *         struct ofproto_port port;
     *
     *         error = ofproto->ofproto_class->port_dump_next(
     *                     ofproto, state, &port);
     *         if (error) {
     *             break;
     *         }
     *         // Do something with 'port' here (without modifying or freeing
     *         // any of its data).
     *     }
     *     ofproto->ofproto_class->port_dump_done(ofproto, state);
     * }
     * // 'error' is now EOF (success) or a positive errno value (failure).
     */
    int (*port_dump_start)(const struct ofproto *ofproto, void **statep);
    int (*port_dump_next)(const struct ofproto *ofproto, void *state,
                          struct ofproto_port *port);
    int (*port_dump_done)(const struct ofproto *ofproto, void *state);

    /* Polls for changes in the set of ports in 'ofproto'.  If the set of ports
     * in 'ofproto' has changed, then this function should do one of the
     * following:
     *
     * - Preferably: store the name of the device that was added to or deleted
     *   from 'ofproto' in '*devnamep' and return 0.  The caller is responsible
     *   for freeing '*devnamep' (with free()) when it no longer needs it.
     *
     * - Alternatively: return ENOBUFS, without indicating the device that was
     *   added or deleted.
     *
     * Occasional 'false positives', in which the function returns 0 while
     * indicating a device that was not actually added or deleted or returns
     * ENOBUFS without any change, are acceptable.
     *
     * The purpose of 'port_poll' is to let 'ofproto' know about changes made
     * externally to the 'ofproto' object, e.g. by a system administrator via
     * ovs-dpctl.  Therefore, it's OK, and even preferable, for port_poll() to
     * not report changes made through calls to 'port_add' or 'port_del' on the
     * same 'ofproto' object.  (But it's OK for it to report them too, just
     * slightly less efficient.)
     *
     * If the set of ports in 'ofproto' has not changed, returns EAGAIN.  May
     * also return other positive errno values to indicate that something has
     * gone wrong.
     *
     * If the set of ports in a datapath is fixed, or if the only way that the
     * set of ports in a datapath can change is through ->port_add() and
     * ->port_del(), then this function may be a null pointer.
     */
    int (*port_poll)(const struct ofproto *ofproto, char **devnamep);

    /* Arranges for the poll loop to wake up when ->port_poll() will return a
     * value other than EAGAIN.
     *
     * If the set of ports in a datapath is fixed, or if the only way that the
     * set of ports in a datapath can change is through ->port_add() and
     * ->port_del(), or if the poll loop will always wake up anyway when
     * ->port_poll() will return a value other than EAGAIN, then this function
     * may be a null pointer.
     */
    void (*port_poll_wait)(const struct ofproto *ofproto);

    /* Checks the status of LACP negotiation for 'port'.  Returns 1 if LACP
     * partner information for 'port' is up-to-date, 0 if LACP partner
     * information is not current (generally indicating a connectivity
     * problem), or -1 if LACP is not enabled on 'port'.
     *
     * This function may be a null pointer if the ofproto implementation does
     * not support LACP. */
    int (*port_is_lacp_current)(const struct ofport *port);

/* ## ----------------------- ## */
/* ## OpenFlow Rule Functions ## */
/* ## ----------------------- ## */



    /* Chooses an appropriate table for 'cls_rule' within 'ofproto'.  On
     * success, stores the table ID into '*table_idp' and returns 0.  On
     * failure, returns an OpenFlow error code (as returned by ofp_mkerr()).
     *
     * The choice of table should be a function of 'cls_rule' and 'ofproto''s
     * datapath capabilities.  It should not depend on the flows already in
     * 'ofproto''s flow tables.  Failure implies that an OpenFlow rule with
     * 'cls_rule' as its matching condition can never be inserted into
     * 'ofproto', even starting from an empty flow table.
     *
     * If multiple tables are candidates for inserting the flow, the function
     * should choose one arbitrarily (but deterministically).
     *
     * This function will never be called for an ofproto that has only one
     * table, so it may be NULL in that case. */
    int (*rule_choose_table)(const struct ofproto *ofproto,
                             const struct cls_rule *cls_rule,
                             uint8_t *table_idp);

    /* Life-cycle functions for a "struct rule" (see "Life Cycle" above).
     *
     *
     * Asynchronous Operation Support
     * ==============================
     *
     * The life-cycle operations on rules can operate asynchronously, meaning
     * that ->rule_construct() and ->rule_destruct() only need to initiate
     * their respective operations and do not need to wait for them to complete
     * before they return.  ->rule_modify_actions() also operates
     * asynchronously.
     *
     * An ofproto implementation reports the success or failure of an
     * asynchronous operation on a rule using the rule's 'pending' member,
     * which points to a opaque "struct ofoperation" that represents the
     * ongoing opreation.  When the operation completes, the ofproto
     * implementation calls ofoperation_complete(), passing the ofoperation and
     * an error indication.
     *
     * Only the following contexts may call ofoperation_complete():
     *
     *   - The function called to initiate the operation,
     *     e.g. ->rule_construct() or ->rule_destruct().  This is the best
     *     choice if the operation completes quickly.
     *
     *   - The implementation's ->run() function.
     *
     *   - The implementation's ->destruct() function.
     *
     * The ofproto base code updates the flow table optimistically, assuming
     * that the operation will probably succeed:
     *
     *   - ofproto adds or replaces the rule in the flow table before calling
     *     ->rule_construct().
     *
     *   - ofproto updates the rule's actions before calling
     *     ->rule_modify_actions().
     *
     *   - ofproto removes the rule before calling ->rule_destruct().
     *
     * With one exception, when an asynchronous operation completes with an
     * error, ofoperation_complete() backs out the already applied changes:
     *
     *   - If adding or replacing a rule in the flow table fails, ofproto
     *     removes the new rule or restores the original rule.
     *
     *   - If modifying a rule's actions fails, ofproto restores the original
     *     actions.
     *
     *   - Removing a rule is not allowed to fail.  It must always succeed.
     *
     * The ofproto base code serializes operations: if any operation is in
     * progress on a given rule, ofproto postpones initiating any new operation
     * on that rule until the pending operation completes.  Therefore, every
     * operation must eventually complete through a call to
     * ofoperation_complete() to avoid delaying new operations indefinitely
     * (including any OpenFlow request that affects the rule in question, even
     * just to query its statistics).
     *
     *
     * Construction
     * ============
     *
     * When ->rule_construct() is called, the caller has already inserted
     * 'rule' into 'rule->ofproto''s flow table numbered 'rule->table_id'.
     * There are two cases:
     *
     *   - 'rule' is a new rule in its flow table.  In this case,
     *     ofoperation_get_victim(rule) returns NULL.
     *
     *   - 'rule' is replacing an existing rule in its flow table that had the
     *     same matching criteria and priority.  In this case,
     *     ofoperation_get_victim(rule) returns the rule being replaced.
     *
     * ->rule_construct() should set the following in motion:
     *
     *   - Validate that the matching rule in 'rule->cr' is supported by the
     *     datapath.  For example, if the rule's table does not support
     *     registers, then it is an error if 'rule->cr' does not wildcard all
     *     registers.
     *
     *   - Validate that 'rule->actions' and 'rule->n_actions' are well-formed
     *     OpenFlow actions that the datapath can correctly implement.  The
     *     validate_actions() function (in ofp-util.c) can be useful as a model
     *     for action validation, but it accepts all of the OpenFlow actions
     *     that OVS understands.  If your ofproto implementation only
     *     implements a subset of those, then you should implement your own
     *     action validation.
     *
     *   - If the rule is valid, update the datapath flow table, adding the new
     *     rule or replacing the existing one.
     *
     * (On failure, the ofproto code will roll back the insertion from the flow
     * table, either removing 'rule' or replacing it by the flow that was
     * originally in its place.)
     *
     * ->rule_construct() must act in one of the following ways:
     *
     *   - If it succeeds, it must call ofoperation_complete() and return 0.
     *
     *   - If it fails, it must act in one of the following ways:
     *
     *       * Call ofoperation_complete() and return 0.
     *
     *       * Return an OpenFlow error code (as returned by ofp_mkerr()).  (Do
     *         not call ofoperation_complete() in this case.)
     *
     *     In the former case, ->rule_destruct() will be called; in the latter
     *     case, it will not.  ->rule_dealloc() will be called in either case.
     *
     *   - If the operation is only partially complete, then it must return 0.
     *     Later, when the operation is complete, the ->run() or ->destruct()
     *     function must call ofoperation_complete() to report success or
     *     failure.
     *
     * ->rule_construct() should not modify any base members of struct rule.
     *
     *
     * Destruction
     * ===========
     *
     * When ->rule_destruct() is called, the caller has already removed 'rule'
     * from 'rule->ofproto''s flow table.  ->rule_destruct() should set in
     * motion removing 'rule' from the datapath flow table.  If removal
     * completes synchronously, it should call ofoperation_complete().
     * Otherwise, the ->run() or ->destruct() function must later call
     * ofoperation_complete() after the operation completes.
     *
     * Rule destruction must not fail. */
    struct rule *(*rule_alloc)(void);
    int (*rule_construct)(struct rule *rule);
    void (*rule_destruct)(struct rule *rule);
    void (*rule_dealloc)(struct rule *rule);

    /* Obtains statistics for 'rule', storing the number of packets that have
     * matched it in '*packet_count' and the number of bytes in those packets
     * in '*byte_count'.  UINT64_MAX indicates that the packet count or byte
     * count is unknown. */
    void (*rule_get_stats)(struct rule *rule, uint64_t *packet_count,
                           uint64_t *byte_count);

    /* Applies the actions in 'rule' to 'packet'.  (This implements sending
     * buffered packets for OpenFlow OFPT_FLOW_MOD commands.)
     *
     * Takes ownership of 'packet' (so it should eventually free it, with
     * ofpbuf_delete()).
     *
     * 'flow' reflects the flow information for 'packet'.  All of the
     * information in 'flow' is extracted from 'packet', except for
     * flow->tun_id and flow->in_port, which are assigned the correct values
     * for the incoming packet.  The register values are zeroed.
     *
     * The statistics for 'packet' should be included in 'rule'.
     *
     * Returns 0 if successful, otherwise an OpenFlow error code (as returned
     * by ofp_mkerr()). */
    int (*rule_execute)(struct rule *rule, struct flow *flow,
                        struct ofpbuf *packet);

    /* When ->rule_modify_actions() is called, the caller has already replaced
     * the OpenFlow actions in 'rule' by a new set.  (The original actions are
     * in rule->pending->actions.)
     *
     * ->rule_modify_actions() should set the following in motion:
     *
     *   - Validate that the actions now in 'rule' are well-formed OpenFlow
     *     actions that the datapath can correctly implement.
     *
     *   - Update the datapath flow table with the new actions.
     *
     * If the operation synchronously completes, ->rule_modify_actions() may
     * call ofoperation_complete() before it returns.  Otherwise, ->run()
     * should call ofoperation_complete() later, after the operation does
     * complete.
     *
     * If the operation fails, then the base ofproto code will restore the
     * original 'actions' and 'n_actions' of 'rule'.
     *
     * ->rule_modify_actions() should not modify any base members of struct
     * rule. */
    void (*rule_modify_actions)(struct rule *rule);

    /* These functions implement the OpenFlow IP fragment handling policy.  By
     * default ('drop_frags' == false), an OpenFlow switch should treat IP
     * fragments the same way as other packets (although TCP and UDP port
     * numbers cannot be determined).  With 'drop_frags' == true, the switch
     * should drop all IP fragments without passing them through the flow
     * table. */
    bool (*get_drop_frags)(struct ofproto *ofproto);
    void (*set_drop_frags)(struct ofproto *ofproto, bool drop_frags);

    /* Implements the OpenFlow OFPT_PACKET_OUT command.  The datapath should
     * execute the 'n_actions' in the 'actions' array on 'packet'.
     *
     * The caller retains ownership of 'packet', so ->packet_out() should not
     * modify or free it.
     *
     * This function must validate that the 'n_actions' elements in 'actions'
     * are well-formed OpenFlow actions that can be correctly implemented by
     * the datapath.  If not, then it should return an OpenFlow error code (as
     * returned by ofp_mkerr()).
     *
     * 'flow' reflects the flow information for 'packet'.  All of the
     * information in 'flow' is extracted from 'packet', except for
     * flow->in_port, which is taken from the OFPT_PACKET_OUT message.
     * flow->tun_id and its register values are zeroed.
     *
     * 'packet' is not matched against the OpenFlow flow table, so its
     * statistics should not be included in OpenFlow flow statistics.
     *
     * Returns 0 if successful, otherwise an OpenFlow error code (as returned
     * by ofp_mkerr()). */
    int (*packet_out)(struct ofproto *ofproto, struct ofpbuf *packet,
                      const struct flow *flow,
                      const union ofp_action *actions,
                      size_t n_actions);

/* ## ------------------------- ## */
/* ## OFPP_NORMAL configuration ## */
/* ## ------------------------- ## */

    /* Configures NetFlow on 'ofproto' according to the options in
     * 'netflow_options', or turns off NetFlow if 'netflow_options' is NULL.
     *
     * EOPNOTSUPP as a return value indicates that 'ofproto' does not support
     * NetFlow, as does a null pointer. */
    int (*set_netflow)(struct ofproto *ofproto,
                       const struct netflow_options *netflow_options);

    void (*get_netflow_ids)(const struct ofproto *ofproto,
                            uint8_t *engine_type, uint8_t *engine_id);

    /* Configures sFlow on 'ofproto' according to the options in
     * 'sflow_options', or turns off sFlow if 'sflow_options' is NULL.
     *
     * EOPNOTSUPP as a return value indicates that 'ofproto' does not support
     * sFlow, as does a null pointer. */
    int (*set_sflow)(struct ofproto *ofproto,
                     const struct ofproto_sflow_options *sflow_options);

    /* Configures connectivity fault management on 'ofport'.
     *
     * If 'cfm_settings' is nonnull, configures CFM according to its members.
     *
     * If 'cfm_settings' is null, removes any connectivity fault management
     * configuration from 'ofport'.
     *
     * EOPNOTSUPP as a return value indicates that this ofproto_class does not
     * support CFM, as does a null pointer. */
    int (*set_cfm)(struct ofport *ofport, const struct cfm_settings *s);

    /* Checks the fault status of CFM configured on 'ofport'.  Returns 1 if CFM
     * is faulted (generally indicating a connectivity problem), 0 if CFM is
     * not faulted, or -1 if CFM is not enabled on 'port'
     *
     * This function may be a null pointer if the ofproto implementation does
     * not support CFM. */
    int (*get_cfm_fault)(const struct ofport *ofport);

    /* If 's' is nonnull, this function registers a "bundle" associated with
     * client data pointer 'aux' in 'ofproto'.  A bundle is the same concept as
     * a Port in OVSDB, that is, it consists of one or more "slave" devices
     * (Interfaces, in OVSDB) along with VLAN and LACP configuration and, if
     * there is more than one slave, a bonding configuration.  If 'aux' is
     * already registered then this function updates its configuration to 's'.
     * Otherwise, this function registers a new bundle.
     *
     * If 's' is NULL, this function unregisters the bundle registered on
     * 'ofproto' associated with client data pointer 'aux'.  If no such bundle
     * has been registered, this has no effect.
     *
     * This function affects only the behavior of the NXAST_AUTOPATH action and
     * output to the OFPP_NORMAL port.  An implementation that does not support
     * it at all may set it to NULL or return EOPNOTSUPP.  An implementation
     * that supports only a subset of the functionality should implement what
     * it can and return 0. */
    int (*bundle_set)(struct ofproto *ofproto, void *aux,
                      const struct ofproto_bundle_settings *s);

    /* If 'port' is part of any bundle, removes it from that bundle.  If the
     * bundle now has no ports, deletes the bundle.  If the bundle now has only
     * one port, deconfigures the bundle's bonding configuration. */
    void (*bundle_remove)(struct ofport *ofport);

    /* If 's' is nonnull, this function registers a mirror associated with
     * client data pointer 'aux' in 'ofproto'.  A mirror is the same concept as
     * a Mirror in OVSDB.  If 'aux' is already registered then this function
     * updates its configuration to 's'.  Otherwise, this function registers a
     * new mirror.
     *
     * If 's' is NULL, this function unregisters the mirror registered on
     * 'ofproto' associated with client data pointer 'aux'.  If no such mirror
     * has been registered, this has no effect.
     *
     * This function affects only the behavior of the OFPP_NORMAL action.  An
     * implementation that does not support it at all may set it to NULL or
     * return EOPNOTSUPP.  An implementation that supports only a subset of the
     * functionality should implement what it can and return 0. */
    int (*mirror_set)(struct ofproto *ofproto, void *aux,
                      const struct ofproto_mirror_settings *s);

    /* Configures the VLANs whose bits are set to 1 in 'flood_vlans' as VLANs
     * on which all packets are flooded, instead of using MAC learning.  If
     * 'flood_vlans' is NULL, then MAC learning applies to all VLANs.
     *
     * This function affects only the behavior of the OFPP_NORMAL action.  An
     * implementation that does not support it may set it to NULL or return
     * EOPNOTSUPP. */
    int (*set_flood_vlans)(struct ofproto *ofproto,
                           unsigned long *flood_vlans);

    /* Returns true if 'aux' is a registered bundle that is currently in use as
     * the output for a mirror. */
    bool (*is_mirror_output_bundle)(struct ofproto *ofproto, void *aux);
};

extern const struct ofproto_class ofproto_dpif_class;

int ofproto_class_register(const struct ofproto_class *);
int ofproto_class_unregister(const struct ofproto_class *);

void ofproto_add_flow(struct ofproto *, const struct cls_rule *,
                      const union ofp_action *, size_t n_actions);
bool ofproto_delete_flow(struct ofproto *, const struct cls_rule *);
void ofproto_flush_flows(struct ofproto *);

#endif /* ofproto/ofproto-provider.h */