/* Copyright (c) 2015, 2016, 2017 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 "bitmap.h"
#include "byte-order.h"
#include "dirs.h"
#include "dp-packet.h"
#include "flow.h"
#include "hash.h"
#include "lflow.h"
#include "ofctrl.h"
#include "openflow/openflow.h"
#include "openvswitch/dynamic-string.h"
#include "openvswitch/hmap.h"
#include "openvswitch/list.h"
#include "openvswitch/match.h"
#include "openvswitch/ofp-actions.h"
#include "openvswitch/ofp-msgs.h"
#include "openvswitch/ofp-parse.h"
#include "openvswitch/ofp-print.h"
#include "openvswitch/ofp-util.h"
#include "openvswitch/ofpbuf.h"
#include "openvswitch/vlog.h"
#include "ovn-controller.h"
#include "ovn/actions.h"
#include "ovn/lib/extend-table.h"
#include "openvswitch/poll-loop.h"
#include "physical.h"
#include "openvswitch/rconn.h"
#include "socket-util.h"
#include "util.h"
#include "vswitch-idl.h"

VLOG_DEFINE_THIS_MODULE(ofctrl);

/* An OpenFlow flow. */
struct ovn_flow {
    struct hmap_node hmap_node; /* For match based hashing. */
    struct ovs_list list_node; /* For handling lists of flows. */

    /* Key. */
    uint8_t table_id;
    uint16_t priority;
    struct match match;

    /* Data. */
    struct ofpact *ofpacts;
    size_t ofpacts_len;
    uint64_t cookie;
};

static uint32_t ovn_flow_hash(const struct ovn_flow *);
static struct ovn_flow *ovn_flow_lookup(struct hmap *flow_table,
                                        const struct ovn_flow *target);
static char *ovn_flow_to_string(const struct ovn_flow *);
static void ovn_flow_log(const struct ovn_flow *, const char *action);
static void ovn_flow_destroy(struct ovn_flow *);

/* OpenFlow connection to the switch. */
static struct rconn *swconn;

/* Symbol table for OVN expressions. */
static struct shash symtab;

/* Last seen sequence number for 'swconn'.  When this differs from
 * rconn_get_connection_seqno(rconn), 'swconn' has reconnected. */
static unsigned int seqno;

/* Connection state machine. */
#define STATES                                  \
    STATE(S_NEW)                                \
    STATE(S_TLV_TABLE_REQUESTED)                \
    STATE(S_TLV_TABLE_MOD_SENT)                 \
    STATE(S_CLEAR_FLOWS)                        \
    STATE(S_UPDATE_FLOWS)
enum ofctrl_state {
#define STATE(NAME) NAME,
    STATES
#undef STATE
};

/* An in-flight update to the switch's flow table.
 *
 * When we receive a barrier reply from the switch with the given 'xid', we
 * know that the switch is caught up to northbound database sequence number
 * 'nb_cfg' (and make that available to the client via ofctrl_get_cur_cfg(), so
 * that it can store it into our Chassis record's nb_cfg column). */
struct ofctrl_flow_update {
    struct ovs_list list_node;  /* In 'flow_updates'. */
    ovs_be32 xid;               /* OpenFlow transaction ID for barrier. */
    int64_t nb_cfg;             /* Northbound database sequence number. */
};

static struct ofctrl_flow_update *
ofctrl_flow_update_from_list_node(const struct ovs_list *list_node)
{
    return CONTAINER_OF(list_node, struct ofctrl_flow_update, list_node);
}

/* Currently in-flight updates. */
static struct ovs_list flow_updates;

/* nb_cfg of latest committed flow update. */
static int64_t cur_cfg;

/* Current state. */
static enum ofctrl_state state;

/* Transaction IDs for messages in flight to the switch. */
static ovs_be32 xid, xid2;

/* Counter for in-flight OpenFlow messages on 'swconn'.  We only send a new
 * round of flow table modifications to the switch when the counter falls to
 * zero, to avoid unbounded buffering. */
static struct rconn_packet_counter *tx_counter;

/* Flow table of "struct ovn_flow"s, that holds the flow table currently
 * installed in the switch. */
static struct hmap installed_flows;

/* A reference to the group_table. */
static struct ovn_extend_table *groups;

/* A reference to the meter_table. */
static struct ovn_extend_table *meters;

/* MFF_* field ID for our Geneve option.  In S_TLV_TABLE_MOD_SENT, this is
 * the option we requested (we don't know whether we obtained it yet).  In
 * S_CLEAR_FLOWS or S_UPDATE_FLOWS, this is really the option we have. */
static enum mf_field_id mff_ovn_geneve;

static ovs_be32 queue_msg(struct ofpbuf *);

static struct ofpbuf *encode_flow_mod(struct ofputil_flow_mod *);

static struct ofpbuf *encode_group_mod(const struct ofputil_group_mod *);

static struct ofpbuf *encode_meter_mod(const struct ofputil_meter_mod *);

static void ovn_flow_table_clear(struct hmap *flow_table);
static void ovn_flow_table_destroy(struct hmap *flow_table);

static void ofctrl_recv(const struct ofp_header *, enum ofptype);

void
ofctrl_init(struct ovn_extend_table *group_table,
            struct ovn_extend_table *meter_table)
{
    swconn = rconn_create(5, 0, DSCP_DEFAULT, 1 << OFP13_VERSION);
    tx_counter = rconn_packet_counter_create();
    hmap_init(&installed_flows);
    ovs_list_init(&flow_updates);
    ovn_init_symtab(&symtab);
    groups = group_table;
    meters = meter_table;
}

/* S_NEW, for a new connection.
 *
 * Sends NXT_TLV_TABLE_REQUEST and transitions to
 * S_TLV_TABLE_REQUESTED. */

static void
run_S_NEW(void)
{
    struct ofpbuf *buf = ofpraw_alloc(OFPRAW_NXT_TLV_TABLE_REQUEST,
                                      rconn_get_version(swconn), 0);
    xid = queue_msg(buf);
    state = S_TLV_TABLE_REQUESTED;
}

static void
recv_S_NEW(const struct ofp_header *oh OVS_UNUSED,
           enum ofptype type OVS_UNUSED,
           struct shash *pending_ct_zones OVS_UNUSED)
{
    OVS_NOT_REACHED();
}

/* S_TLV_TABLE_REQUESTED, when NXT_TLV_TABLE_REQUEST has been sent
 * and we're waiting for a reply.
 *
 * If we receive an NXT_TLV_TABLE_REPLY:
 *
 *     - If it contains our tunnel metadata option, assign its field ID to
 *       mff_ovn_geneve and transition to S_CLEAR_FLOWS.
 *
 *     - Otherwise, if there is an unused tunnel metadata field ID, send
 *       NXT_TLV_TABLE_MOD and OFPT_BARRIER_REQUEST, and transition to
 *       S_TLV_TABLE_MOD_SENT.
 *
 *     - Otherwise, log an error, disable Geneve, and transition to
 *       S_CLEAR_FLOWS.
 *
 * If we receive an OFPT_ERROR:
 *
 *     - Log an error, disable Geneve, and transition to S_CLEAR_FLOWS. */

static void
run_S_TLV_TABLE_REQUESTED(void)
{
}

static bool
process_tlv_table_reply(const struct ofputil_tlv_table_reply *reply)
{
    const struct ofputil_tlv_map *map;
    uint64_t md_free = UINT64_MAX;
    BUILD_ASSERT(TUN_METADATA_NUM_OPTS == 64);

    LIST_FOR_EACH (map, list_node, &reply->mappings) {
        if (map->option_class == OVN_GENEVE_CLASS
            && map->option_type == OVN_GENEVE_TYPE
            && map->option_len == OVN_GENEVE_LEN) {
            if (map->index >= TUN_METADATA_NUM_OPTS) {
                VLOG_ERR("desired Geneve tunnel option 0x%"PRIx16","
                         "%"PRIu8",%"PRIu8" already in use with "
                         "unsupported index %"PRIu16,
                         map->option_class, map->option_type,
                         map->option_len, map->index);
                return false;
            } else {
                mff_ovn_geneve = MFF_TUN_METADATA0 + map->index;
                state = S_CLEAR_FLOWS;
                return true;
            }
        }

        if (map->index < TUN_METADATA_NUM_OPTS) {
            md_free &= ~(UINT64_C(1) << map->index);
        }
    }

    VLOG_DBG("OVN Geneve option not found");
    if (!md_free) {
        VLOG_ERR("no Geneve options free for use by OVN");
        return false;
    }

    unsigned int index = rightmost_1bit_idx(md_free);
    mff_ovn_geneve = MFF_TUN_METADATA0 + index;
    struct ofputil_tlv_map tm;
    tm.option_class = OVN_GENEVE_CLASS;
    tm.option_type = OVN_GENEVE_TYPE;
    tm.option_len = OVN_GENEVE_LEN;
    tm.index = index;

    struct ofputil_tlv_table_mod ttm;
    ttm.command = NXTTMC_ADD;
    ovs_list_init(&ttm.mappings);
    ovs_list_push_back(&ttm.mappings, &tm.list_node);

    xid = queue_msg(ofputil_encode_tlv_table_mod(OFP13_VERSION, &ttm));
    xid2 = queue_msg(ofputil_encode_barrier_request(OFP13_VERSION));
    state = S_TLV_TABLE_MOD_SENT;

    return true;
}

static void
recv_S_TLV_TABLE_REQUESTED(const struct ofp_header *oh, enum ofptype type,
                           struct shash *pending_ct_zones OVS_UNUSED)
{
    if (oh->xid != xid) {
        ofctrl_recv(oh, type);
        return;
    } else if (type == OFPTYPE_NXT_TLV_TABLE_REPLY) {
        struct ofputil_tlv_table_reply reply;
        enum ofperr error = ofputil_decode_tlv_table_reply(oh, &reply);
        if (!error) {
            bool ok = process_tlv_table_reply(&reply);
            ofputil_uninit_tlv_table(&reply.mappings);
            if (ok) {
                return;
            }
        } else {
            VLOG_ERR("failed to decode TLV table request (%s)",
                     ofperr_to_string(error));
        }
    } else if (type == OFPTYPE_ERROR) {
        VLOG_ERR("switch refused to allocate Geneve option (%s)",
                 ofperr_to_string(ofperr_decode_msg(oh, NULL)));
    } else {
        char *s = ofp_to_string(oh, ntohs(oh->length), NULL, 1);
        VLOG_ERR("unexpected reply to TLV table request (%s)", s);
        free(s);
    }

    /* Error path. */
    mff_ovn_geneve = 0;
    state = S_CLEAR_FLOWS;
}

/* S_TLV_TABLE_MOD_SENT, when NXT_TLV_TABLE_MOD and OFPT_BARRIER_REQUEST
 * have been sent and we're waiting for a reply to one or the other.
 *
 * If we receive an OFPT_ERROR:
 *
 *     - If the error is NXTTMFC_ALREADY_MAPPED or NXTTMFC_DUP_ENTRY, we
 *       raced with some other controller.  Transition to S_NEW.
 *
 *     - Otherwise, log an error, disable Geneve, and transition to
 *       S_CLEAR_FLOWS.
 *
 * If we receive OFPT_BARRIER_REPLY:
 *
 *     - Set the tunnel metadata field ID to the one that we requested.
 *       Transition to S_CLEAR_FLOWS.
 */

static void
run_S_TLV_TABLE_MOD_SENT(void)
{
}

static void
recv_S_TLV_TABLE_MOD_SENT(const struct ofp_header *oh, enum ofptype type,
                          struct shash *pending_ct_zones OVS_UNUSED)
{
    if (oh->xid != xid && oh->xid != xid2) {
        ofctrl_recv(oh, type);
    } else if (oh->xid == xid2 && type == OFPTYPE_BARRIER_REPLY) {
        state = S_CLEAR_FLOWS;
    } else if (oh->xid == xid && type == OFPTYPE_ERROR) {
        enum ofperr error = ofperr_decode_msg(oh, NULL);
        if (error == OFPERR_NXTTMFC_ALREADY_MAPPED ||
            error == OFPERR_NXTTMFC_DUP_ENTRY) {
            VLOG_INFO("raced with another controller adding "
                      "Geneve option (%s); trying again",
                      ofperr_to_string(error));
            state = S_NEW;
        } else {
            VLOG_ERR("error adding Geneve option (%s)",
                     ofperr_to_string(error));
            goto error;
        }
    } else {
        char *s = ofp_to_string(oh, ntohs(oh->length), NULL, 1);
        VLOG_ERR("unexpected reply to Geneve option allocation request (%s)",
                 s);
        free(s);
        goto error;
    }
    return;

error:
    state = S_CLEAR_FLOWS;
}

/* S_CLEAR_FLOWS, after we've established a Geneve metadata field ID and it's
 * time to set up some flows.
 *
 * Sends an OFPT_TABLE_MOD to clear all flows, then transitions to
 * S_UPDATE_FLOWS. */

static void
run_S_CLEAR_FLOWS(void)
{
    /* Send a flow_mod to delete all flows. */
    struct ofputil_flow_mod fm = {
        .match = MATCH_CATCHALL_INITIALIZER,
        .table_id = OFPTT_ALL,
        .command = OFPFC_DELETE,
    };
    queue_msg(encode_flow_mod(&fm));
    VLOG_DBG("clearing all flows");

    /* Clear installed_flows, to match the state of the switch. */
    ovn_flow_table_clear(&installed_flows);

    /* Send a group_mod to delete all groups. */
    struct ofputil_group_mod gm;
    memset(&gm, 0, sizeof gm);
    gm.command = OFPGC11_DELETE;
    gm.group_id = OFPG_ALL;
    gm.command_bucket_id = OFPG15_BUCKET_ALL;
    ovs_list_init(&gm.buckets);
    queue_msg(encode_group_mod(&gm));
    ofputil_uninit_group_mod(&gm);

    /* Clear existing groups, to match the state of the switch. */
    if (groups) {
        ovn_extend_table_clear(groups, true);
    }

    /* Send a meter_mod to delete all meters. */
    struct ofputil_meter_mod mm;
    memset(&mm, 0, sizeof mm);
    mm.command = OFPMC13_DELETE;
    mm.meter.meter_id = OFPM13_ALL;
    queue_msg(encode_meter_mod(&mm));

    /* Clear existing meters, to match the state of the switch. */
    if (meters) {
        ovn_extend_table_clear(meters, true);
    }

    /* All flow updates are irrelevant now. */
    struct ofctrl_flow_update *fup, *next;
    LIST_FOR_EACH_SAFE (fup, next, list_node, &flow_updates) {
        ovs_list_remove(&fup->list_node);
        free(fup);
    }

    state = S_UPDATE_FLOWS;
}

static void
recv_S_CLEAR_FLOWS(const struct ofp_header *oh, enum ofptype type,
                   struct shash *pending_ct_zones OVS_UNUSED)
{
    ofctrl_recv(oh, type);
}

/* S_UPDATE_FLOWS, for maintaining the flow table over time.
 *
 * Compare the installed flows to the ones we want.  Send OFPT_FLOW_MOD as
 * necessary.
 *
 * This is a terminal state.  We only transition out of it if the connection
 * drops. */

static void
run_S_UPDATE_FLOWS(void)
{
    /* Nothing to do here.
     *
     * Being in this state enables ofctrl_put() to work, however. */
}

static void
recv_S_UPDATE_FLOWS(const struct ofp_header *oh, enum ofptype type,
                    struct shash *pending_ct_zones)
{
    if (type == OFPTYPE_BARRIER_REPLY && !ovs_list_is_empty(&flow_updates)) {
        struct ofctrl_flow_update *fup = ofctrl_flow_update_from_list_node(
            ovs_list_front(&flow_updates));
        if (fup->xid == oh->xid) {
            if (fup->nb_cfg >= cur_cfg) {
                cur_cfg = fup->nb_cfg;
            }
            ovs_list_remove(&fup->list_node);
            free(fup);
        }

        /* If the barrier xid is associated with an outstanding conntrack
         * flush, the flush succeeded.  Move the pending ct zone entry
         * to the next stage. */
        struct shash_node *iter;
        SHASH_FOR_EACH(iter, pending_ct_zones) {
            struct ct_zone_pending_entry *ctzpe = iter->data;
            if (ctzpe->state == CT_ZONE_OF_SENT && ctzpe->of_xid == oh->xid) {
                ctzpe->state = CT_ZONE_DB_QUEUED;
            }
        }
    } else {
        ofctrl_recv(oh, type);
    }
}

/* Runs the OpenFlow state machine against 'br_int', which is local to the
 * hypervisor on which we are running.  Attempts to negotiate a Geneve option
 * field for class OVN_GENEVE_CLASS, type OVN_GENEVE_TYPE.  If successful,
 * returns the MFF_* field ID for the option, otherwise returns 0. */
enum mf_field_id
ofctrl_run(const struct ovsrec_bridge *br_int, struct shash *pending_ct_zones)
{
    char *target = xasprintf("unix:%s/%s.mgmt", ovs_rundir(), br_int->name);
    if (strcmp(target, rconn_get_target(swconn))) {
        VLOG_INFO("%s: connecting to switch", target);
        rconn_connect(swconn, target, target);
    }
    free(target);

    rconn_run(swconn);

    if (!rconn_is_connected(swconn)) {
        return 0;
    }
    if (seqno != rconn_get_connection_seqno(swconn)) {
        seqno = rconn_get_connection_seqno(swconn);
        state = S_NEW;

        /* Reset the state of any outstanding ct flushes to resend them. */
        struct shash_node *iter;
        SHASH_FOR_EACH(iter, pending_ct_zones) {
            struct ct_zone_pending_entry *ctzpe = iter->data;
            if (ctzpe->state == CT_ZONE_OF_SENT) {
                ctzpe->state = CT_ZONE_OF_QUEUED;
            }
        }
    }

    bool progress = true;
    for (int i = 0; progress && i < 50; i++) {
        /* Allow the state machine to run. */
        enum ofctrl_state old_state = state;
        switch (state) {
#define STATE(NAME) case NAME: run_##NAME(); break;
            STATES
#undef STATE
        default:
            OVS_NOT_REACHED();
        }

        /* Try to process a received packet. */
        struct ofpbuf *msg = rconn_recv(swconn);
        if (msg) {
            const struct ofp_header *oh = msg->data;
            enum ofptype type;
            enum ofperr error;

            error = ofptype_decode(&type, oh);
            if (!error) {
                switch (state) {
#define STATE(NAME) case NAME: recv_##NAME(oh, type, pending_ct_zones); break;
                    STATES
#undef STATE
                default:
                    OVS_NOT_REACHED();
                }
            } else {
                char *s = ofp_to_string(oh, ntohs(oh->length), NULL, 1);
                VLOG_WARN("could not decode OpenFlow message (%s): %s",
                          ofperr_to_string(error), s);
                free(s);
            }

            ofpbuf_delete(msg);
        }

        /* If we did some work, plan to go around again. */
        progress = old_state != state || msg;
    }
    if (progress) {
        /* We bailed out to limit the amount of work we do in one go, to allow
         * other code a chance to run.  We were still making progress at that
         * point, so ensure that we come back again without waiting. */
        poll_immediate_wake();
    }

    return (state == S_CLEAR_FLOWS || state == S_UPDATE_FLOWS
            ? mff_ovn_geneve : 0);
}

void
ofctrl_wait(void)
{
    rconn_run_wait(swconn);
    rconn_recv_wait(swconn);
}

void
ofctrl_destroy(void)
{
    rconn_destroy(swconn);
    ovn_flow_table_destroy(&installed_flows);
    rconn_packet_counter_destroy(tx_counter);
    expr_symtab_destroy(&symtab);
    shash_destroy(&symtab);
}

int64_t
ofctrl_get_cur_cfg(void)
{
    return cur_cfg;
}

static ovs_be32
queue_msg(struct ofpbuf *msg)
{
    const struct ofp_header *oh = msg->data;
    ovs_be32 xid = oh->xid;
    rconn_send(swconn, msg, tx_counter);
    return xid;
}

static void
log_openflow_rl(struct vlog_rate_limit *rl, enum vlog_level level,
                const struct ofp_header *oh, const char *title)
{
    if (!vlog_should_drop(&this_module, level, rl)) {
        char *s = ofp_to_string(oh, ntohs(oh->length), NULL, 2);
        vlog(&this_module, level, "%s: %s", title, s);
        free(s);
    }
}

static void
ofctrl_recv(const struct ofp_header *oh, enum ofptype type)
{
    if (type == OFPTYPE_ECHO_REQUEST) {
        queue_msg(make_echo_reply(oh));
    } else if (type == OFPTYPE_ERROR) {
        static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(30, 300);
        log_openflow_rl(&rl, VLL_INFO, oh, "OpenFlow error");
    } else {
        static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(30, 300);
        log_openflow_rl(&rl, VLL_DBG, oh, "OpenFlow packet ignored");
    }
}

/* Flow table interfaces to the rest of ovn-controller. */

/* Adds a flow to 'desired_flows' with the specified 'match' and 'actions' to
 * the OpenFlow table numbered 'table_id' with the given 'priority' and
 * OpenFlow 'cookie'.  The caller retains ownership of 'match' and 'actions'.
 *
 * This just assembles the desired flow table in memory.  Nothing is actually
 * sent to the switch until a later call to ofctrl_put().
 *
 * The caller should initialize its own hmap to hold the flows. */
void
ofctrl_add_flow(struct hmap *desired_flows,
                uint8_t table_id, uint16_t priority, uint64_t cookie,
                const struct match *match,
                const struct ofpbuf *actions)
{
    struct ovn_flow *f = xmalloc(sizeof *f);
    f->table_id = table_id;
    f->priority = priority;
    f->match = *match;
    f->ofpacts = xmemdup(actions->data, actions->size);
    f->ofpacts_len = actions->size;
    f->hmap_node.hash = ovn_flow_hash(f);
    f->cookie = cookie;

    if (ovn_flow_lookup(desired_flows, f)) {
        static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 5);
        if (!VLOG_DROP_DBG(&rl)) {
            char *s = ovn_flow_to_string(f);
            VLOG_DBG("dropping duplicate flow: %s", s);
            free(s);
        }

        ovn_flow_destroy(f);
        return;
    }

    hmap_insert(desired_flows, &f->hmap_node, f->hmap_node.hash);
}


/* ovn_flow. */

/* Returns a hash of the key in 'f'. */
static uint32_t
ovn_flow_hash(const struct ovn_flow *f)
{
    return hash_2words((f->table_id << 16) | f->priority,
                       match_hash(&f->match, 0));

}

/* Duplicate an ovn_flow structure. */
struct ovn_flow *
ofctrl_dup_flow(struct ovn_flow *src)
{
    struct ovn_flow *dst = xmalloc(sizeof *dst);
    dst->table_id = src->table_id;
    dst->priority = src->priority;
    dst->match = src->match;
    dst->ofpacts = xmemdup(src->ofpacts, src->ofpacts_len);
    dst->ofpacts_len = src->ofpacts_len;
    dst->hmap_node.hash = ovn_flow_hash(dst);
    return dst;
}

/* Finds and returns an ovn_flow in 'flow_table' whose key is identical to
 * 'target''s key, or NULL if there is none. */
static struct ovn_flow *
ovn_flow_lookup(struct hmap *flow_table, const struct ovn_flow *target)
{
    struct ovn_flow *f;

    HMAP_FOR_EACH_WITH_HASH (f, hmap_node, target->hmap_node.hash,
                             flow_table) {
        if (f->table_id == target->table_id
            && f->priority == target->priority
            && match_equal(&f->match, &target->match)) {
            return f;
        }
    }
    return NULL;
}

static char *
ovn_flow_to_string(const struct ovn_flow *f)
{
    struct ds s = DS_EMPTY_INITIALIZER;
    ds_put_format(&s, "table_id=%"PRIu8", ", f->table_id);
    ds_put_format(&s, "priority=%"PRIu16", ", f->priority);
    match_format(&f->match, NULL, &s, OFP_DEFAULT_PRIORITY);
    ds_put_cstr(&s, ", actions=");
    ofpacts_format(f->ofpacts, f->ofpacts_len, NULL, &s);
    return ds_steal_cstr(&s);
}

static void
ovn_flow_log(const struct ovn_flow *f, const char *action)
{
    if (VLOG_IS_DBG_ENABLED()) {
        char *s = ovn_flow_to_string(f);
        VLOG_DBG("%s flow: %s", action, s);
        free(s);
    }
}

static void
ovn_flow_destroy(struct ovn_flow *f)
{
    if (f) {
        free(f->ofpacts);
        free(f);
    }
}

/* Flow tables of struct ovn_flow. */

static void
ovn_flow_table_clear(struct hmap *flow_table)
{
    struct ovn_flow *f, *next;
    HMAP_FOR_EACH_SAFE (f, next, hmap_node, flow_table) {
        hmap_remove(flow_table, &f->hmap_node);
        ovn_flow_destroy(f);
    }
}

static void
ovn_flow_table_destroy(struct hmap *flow_table)
{
    ovn_flow_table_clear(flow_table);
    hmap_destroy(flow_table);
}

/* Flow table update. */

static struct ofpbuf *
encode_flow_mod(struct ofputil_flow_mod *fm)
{
    fm->buffer_id = UINT32_MAX;
    fm->out_port = OFPP_ANY;
    fm->out_group = OFPG_ANY;
    return ofputil_encode_flow_mod(fm, OFPUTIL_P_OF13_OXM);
}

static void
add_flow_mod(struct ofputil_flow_mod *fm, struct ovs_list *msgs)
{
    struct ofpbuf *msg = encode_flow_mod(fm);
    ovs_list_push_back(msgs, &msg->list_node);
}

/* group_table. */

static struct ofpbuf *
encode_group_mod(const struct ofputil_group_mod *gm)
{
    return ofputil_encode_group_mod(OFP13_VERSION, gm);
}

static void
add_group_mod(const struct ofputil_group_mod *gm, struct ovs_list *msgs)
{
    struct ofpbuf *msg = encode_group_mod(gm);
    ovs_list_push_back(msgs, &msg->list_node);
}


static struct ofpbuf *
encode_meter_mod(const struct ofputil_meter_mod *mm)
{
    return ofputil_encode_meter_mod(OFP13_VERSION, mm);
}

static void
add_meter_mod(const struct ofputil_meter_mod *mm, struct ovs_list *msgs)
{
    struct ofpbuf *msg = encode_meter_mod(mm);
    ovs_list_push_back(msgs, &msg->list_node);
}

static void
add_ct_flush_zone(uint16_t zone_id, struct ovs_list *msgs)
{
    struct ofpbuf *msg = ofpraw_alloc(OFPRAW_NXT_CT_FLUSH_ZONE,
                                      rconn_get_version(swconn), 0);
    struct nx_zone_id *nzi = ofpbuf_put_zeros(msg, sizeof *nzi);
    nzi->zone_id = htons(zone_id);

    ovs_list_push_back(msgs, &msg->list_node);
}

/* The flow table can be updated if the connection to the switch is up and
 * in the correct state and not backlogged with existing flow_mods.  (Our
 * criteria for being backlogged appear very conservative, but the socket
 * between ovn-controller and OVS provides some buffering.) */
bool
ofctrl_can_put(void)
{
    if (state != S_UPDATE_FLOWS
        || rconn_packet_counter_n_packets(tx_counter)
        || rconn_get_version(swconn) < 0) {
        return false;
    }
    return true;
}

/* Replaces the flow table on the switch, if possible, by the flows added
 * with ofctrl_add_flow().
 *
 * Replaces the group table and meter table on the switch, if possible, by the
 *  contents of 'groups->desired'.  Regardless of whether the group table
 * is updated, this deletes all the groups from the 'groups->desired' and frees
 * them. (The hmap itself isn't destroyed.)
 *
 * Sends conntrack flush messages to each zone in 'pending_ct_zones' that
 * is in the CT_ZONE_OF_QUEUED state and then moves the zone into the
 * CT_ZONE_OF_SENT state.
 *
 * This should be called after ofctrl_run() within the main loop. */
void
ofctrl_put(struct hmap *flow_table, struct shash *pending_ct_zones,
           int64_t nb_cfg)
{
    if (!ofctrl_can_put()) {
        ovn_flow_table_clear(flow_table);
        ovn_extend_table_clear(groups, false);
        ovn_extend_table_clear(meters, false);
        return;
    }

    /* OpenFlow messages to send to the switch to bring it up-to-date. */
    struct ovs_list msgs = OVS_LIST_INITIALIZER(&msgs);

    /* Iterate through ct zones that need to be flushed. */
    struct shash_node *iter;
    SHASH_FOR_EACH(iter, pending_ct_zones) {
        struct ct_zone_pending_entry *ctzpe = iter->data;
        if (ctzpe->state == CT_ZONE_OF_QUEUED) {
            add_ct_flush_zone(ctzpe->zone, &msgs);
            ctzpe->state = CT_ZONE_OF_SENT;
            ctzpe->of_xid = 0;
        }
    }

    /* Iterate through all the desired groups. If there are new ones,
     * add them to the switch. */
    struct ovn_extend_table_info *desired;
    EXTEND_TABLE_FOR_EACH_UNINSTALLED (desired, groups) {
        /* Create and install new group. */
        struct ofputil_group_mod gm;
        enum ofputil_protocol usable_protocols;
        char *group_string = xasprintf("group_id=%"PRIu32",%s",
                                       desired->table_id,
                                       ds_cstr(&desired->info));
        char *error = parse_ofp_group_mod_str(&gm, OFPGC11_ADD, group_string,
                                              NULL, &usable_protocols);
        if (!error) {
            add_group_mod(&gm, &msgs);
        } else {
            static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 1);
            VLOG_ERR_RL(&rl, "new group %s %s", error, group_string);
            free(error);
        }
        free(group_string);
        ofputil_uninit_group_mod(&gm);
    }

    /* Iterate through all the desired meters. If there are new ones,
     * add them to the switch. */
    struct ovn_extend_table_info *m_desired;
    EXTEND_TABLE_FOR_EACH_UNINSTALLED (m_desired, meters) {
        /* Create and install new meter. */
        struct ofputil_meter_mod mm;
        enum ofputil_protocol usable_protocols;
        char *meter_string = xasprintf("meter=%"PRIu32",%s",
                                       m_desired->table_id,
                                       ds_cstr(&m_desired->info));
        char *error = parse_ofp_meter_mod_str(&mm, meter_string, OFPMC13_ADD,
                                              &usable_protocols);
        if (!error) {
            add_meter_mod(&mm, &msgs);
        } else {
            static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 1);
            VLOG_ERR_RL(&rl, "new meter %s %s", error, meter_string);
            free(error);
        }
        free(meter_string);
    }

    /* Iterate through all of the installed flows.  If any of them are no
     * longer desired, delete them; if any of them should have different
     * actions, update them. */
    struct ovn_flow *i, *next;
    HMAP_FOR_EACH_SAFE (i, next, hmap_node, &installed_flows) {
        struct ovn_flow *d = ovn_flow_lookup(flow_table, i);
        if (!d) {
            /* Installed flow is no longer desirable.  Delete it from the
             * switch and from installed_flows. */
            struct ofputil_flow_mod fm = {
                .match = i->match,
                .priority = i->priority,
                .table_id = i->table_id,
                .command = OFPFC_DELETE_STRICT,
            };
            add_flow_mod(&fm, &msgs);
            ovn_flow_log(i, "removing installed");

            hmap_remove(&installed_flows, &i->hmap_node);
            ovn_flow_destroy(i);
        } else {
            if (!ofpacts_equal(i->ofpacts, i->ofpacts_len,
                               d->ofpacts, d->ofpacts_len)) {
                /* Update actions in installed flow. */
                struct ofputil_flow_mod fm = {
                    .match = i->match,
                    .priority = i->priority,
                    .table_id = i->table_id,
                    .ofpacts = d->ofpacts,
                    .ofpacts_len = d->ofpacts_len,
                    .command = OFPFC_MODIFY_STRICT,
                };
                add_flow_mod(&fm, &msgs);
                ovn_flow_log(i, "updating installed");

                /* Replace 'i''s actions by 'd''s. */
                free(i->ofpacts);
                i->ofpacts = d->ofpacts;
                i->ofpacts_len = d->ofpacts_len;
                d->ofpacts = NULL;
                d->ofpacts_len = 0;
            }

            hmap_remove(flow_table, &d->hmap_node);
            ovn_flow_destroy(d);
        }
    }

    /* The previous loop removed from 'flow_table' all of the flows that are
     * already installed.  Thus, any flows remaining in 'flow_table' need to
     * be added to the flow table. */
    struct ovn_flow *d;
    HMAP_FOR_EACH_SAFE (d, next, hmap_node, flow_table) {
        /* Send flow_mod to add flow. */
        struct ofputil_flow_mod fm = {
            .match = d->match,
            .priority = d->priority,
            .table_id = d->table_id,
            .ofpacts = d->ofpacts,
            .ofpacts_len = d->ofpacts_len,
            .new_cookie = htonll(d->cookie),
            .command = OFPFC_ADD,
        };
        add_flow_mod(&fm, &msgs);
        ovn_flow_log(d, "adding installed");

        /* Move 'd' from 'flow_table' to installed_flows. */
        hmap_remove(flow_table, &d->hmap_node);
        hmap_insert(&installed_flows, &d->hmap_node, d->hmap_node.hash);
    }

    /* Iterate through the installed groups from previous runs. If they
     * are not needed delete them. */
    struct ovn_extend_table_info *installed, *next_group;
    EXTEND_TABLE_FOR_EACH_INSTALLED (installed, next_group, groups) {
        /* Delete the group. */
        struct ofputil_group_mod gm;
        enum ofputil_protocol usable_protocols;
        char *group_string = xasprintf("group_id=%"PRIu32"",
                                       installed->table_id);
        char *error = parse_ofp_group_mod_str(&gm, OFPGC11_DELETE,
                                              group_string, NULL,
                                              &usable_protocols);
        if (!error) {
            add_group_mod(&gm, &msgs);
        } else {
            static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 1);
            VLOG_ERR_RL(&rl, "Error deleting group %d: %s",
                        installed->table_id, error);
            free(error);
        }
        free(group_string);
        ofputil_uninit_group_mod(&gm);
        ovn_extend_table_remove(groups, installed);
    }

    /* Move the contents of groups->desired to groups->existing. */
    ovn_extend_table_move(groups);

    /* Iterate through the installed meters from previous runs. If they
     * are not needed delete them. */
    struct ovn_extend_table_info *m_installed, *next_meter;
    EXTEND_TABLE_FOR_EACH_INSTALLED (m_installed, next_meter, meters) {
        /* Delete the meter. */
        struct ofputil_meter_mod mm;
        enum ofputil_protocol usable_protocols;
        char *meter_string = xasprintf("meter=%"PRIu32"",
                                       m_installed->table_id);
        char *error = parse_ofp_meter_mod_str(&mm, meter_string,
                                              OFPMC13_DELETE,
                                              &usable_protocols);
        if (!error) {
            add_meter_mod(&mm, &msgs);
        } else {
            static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 1);
            VLOG_ERR_RL(&rl,  "Error deleting meter %"PRIu32": %s",
                        m_installed->table_id, error);
            free(error);
        }
        free(meter_string);
        ovn_extend_table_remove(meters, m_installed);
    }

    /* Move the contents of meters->desired to meters->existing. */
    ovn_extend_table_move(meters);

    if (!ovs_list_is_empty(&msgs)) {
        /* Add a barrier to the list of messages. */
        struct ofpbuf *barrier = ofputil_encode_barrier_request(OFP13_VERSION);
        const struct ofp_header *oh = barrier->data;
        ovs_be32 xid = oh->xid;
        ovs_list_push_back(&msgs, &barrier->list_node);

        /* Queue the messages. */
        struct ofpbuf *msg;
        LIST_FOR_EACH_POP (msg, list_node, &msgs) {
            queue_msg(msg);
        }

        /* Store the barrier's xid with any newly sent ct flushes. */
        SHASH_FOR_EACH(iter, pending_ct_zones) {
            struct ct_zone_pending_entry *ctzpe = iter->data;
            if (ctzpe->state == CT_ZONE_OF_SENT && !ctzpe->of_xid) {
                ctzpe->of_xid = xid;
            }
        }

        /* Track the flow update. */
        struct ofctrl_flow_update *fup, *prev;
        LIST_FOR_EACH_REVERSE_SAFE (fup, prev, list_node, &flow_updates) {
            if (nb_cfg < fup->nb_cfg) {
                /* This ofctrl_flow_update is for a configuration later than
                 * 'nb_cfg'.  This should not normally happen, because it means
                 * that 'nb_cfg' in the SB_Global table of the southbound
                 * database decreased, and it should normally be monotonically
                 * increasing. */
                VLOG_WARN("nb_cfg regressed from %"PRId64" to %"PRId64,
                          fup->nb_cfg, nb_cfg);
                ovs_list_remove(&fup->list_node);
                free(fup);
            } else if (nb_cfg == fup->nb_cfg) {
                /* This ofctrl_flow_update is for the same configuration as
                 * 'nb_cfg'.  Probably, some change to the physical topology
                 * means that we had to revise the OpenFlow flow table even
                 * though the logical topology did not change.  Update fp->xid,
                 * so that we don't send a notification that we're up-to-date
                 * until we're really caught up. */
                VLOG_DBG("advanced xid target for nb_cfg=%"PRId64, nb_cfg);
                fup->xid = xid;
                goto done;
            } else {
                break;
            }
        }

        /* Add a flow update. */
        fup = xmalloc(sizeof *fup);
        ovs_list_push_back(&flow_updates, &fup->list_node);
        fup->xid = xid;
        fup->nb_cfg = nb_cfg;
    done:;
    } else if (!ovs_list_is_empty(&flow_updates)) {
        /* Getting up-to-date with 'nb_cfg' didn't require any extra flow table
         * changes, so whenever we get up-to-date with the most recent flow
         * table update, we're also up-to-date with 'nb_cfg'. */
        struct ofctrl_flow_update *fup = ofctrl_flow_update_from_list_node(
            ovs_list_back(&flow_updates));
        fup->nb_cfg = nb_cfg;
    } else {
        /* We were completely up-to-date before and still are. */
        cur_cfg = nb_cfg;
    }
}

/* Looks up the logical port with the name 'port_name' in 'br_int_'.  If
 * found, returns true and sets '*portp' to the OpenFlow port number
 * assigned to the port.  Otherwise, returns false. */
static bool
ofctrl_lookup_port(const void *br_int_, const char *port_name,
                   unsigned int *portp)
{
    const struct ovsrec_bridge *br_int = br_int_;

    for (int i = 0; i < br_int->n_ports; i++) {
        const struct ovsrec_port *port_rec = br_int->ports[i];
        for (int j = 0; j < port_rec->n_interfaces; j++) {
            const struct ovsrec_interface *iface_rec = port_rec->interfaces[j];
            const char *iface_id = smap_get(&iface_rec->external_ids,
                                            "iface-id");

            if (iface_id && !strcmp(iface_id, port_name)) {
                if (!iface_rec->n_ofport) {
                    continue;
                }

                int64_t ofport = iface_rec->ofport[0];
                if (ofport < 1 || ofport > ofp_to_u16(OFPP_MAX)) {
                    continue;
                }
                *portp = ofport;
                return true;
            }
        }
    }

    return false;
}

/* Generates a packet described by 'flow_s' in the syntax of an OVN
 * logical expression and injects it into 'br_int'.  The flow
 * description must contain an ingress logical port that is present on
 * 'br_int'.
 *
 * Returns NULL if successful, otherwise an error message that the caller
 * must free(). */
char *
ofctrl_inject_pkt(const struct ovsrec_bridge *br_int, const char *flow_s,
                  const struct shash *addr_sets)
{
    int version = rconn_get_version(swconn);
    if (version < 0) {
        return xstrdup("OpenFlow channel not ready.");
    }

    struct flow uflow;
    char *error = expr_parse_microflow(flow_s, &symtab, addr_sets,
                                       ofctrl_lookup_port, br_int, &uflow);
    if (error) {
        return error;
    }

    /* The physical OpenFlow port was stored in the logical ingress
     * port, so put it in the correct location for a flow structure. */
    uflow.in_port.ofp_port = u16_to_ofp(uflow.regs[MFF_LOG_INPORT - MFF_REG0]);
    uflow.regs[MFF_LOG_INPORT - MFF_REG0] = 0;

    if (!uflow.in_port.ofp_port) {
        return xstrdup("ingress port not found on hypervisor.");
    }

    uint64_t packet_stub[128 / 8];
    struct dp_packet packet;
    dp_packet_use_stub(&packet, packet_stub, sizeof packet_stub);
    flow_compose(&packet, &uflow, 0);

    uint64_t ofpacts_stub[1024 / 8];
    struct ofpbuf ofpacts = OFPBUF_STUB_INITIALIZER(ofpacts_stub);
    struct ofpact_resubmit *resubmit = ofpact_put_RESUBMIT(&ofpacts);
    resubmit->in_port = OFPP_IN_PORT;
    resubmit->table_id = 0;

    struct ofputil_packet_out po = {
        .packet = dp_packet_data(&packet),
        .packet_len = dp_packet_size(&packet),
        .buffer_id = UINT32_MAX,
        .ofpacts = ofpacts.data,
        .ofpacts_len = ofpacts.size,
    };
    match_set_in_port(&po.flow_metadata, uflow.in_port.ofp_port);
    enum ofputil_protocol proto = ofputil_protocol_from_ofp_version(version);
    queue_msg(ofputil_encode_packet_out(&po, proto));
    dp_packet_uninit(&packet);
    ofpbuf_uninit(&ofpacts);

    return NULL;
}
