text: /* Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015 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 "ofproto-dpif-upcall.h"
  
  #include <errno.h>
  #include <stdbool.h>
  #include <inttypes.h>
  
  #include "connmgr.h"
  #include "coverage.h"
  #include "cmap.h"
  #include "dpif.h"
  #include "dynamic-string.h"
  #include "fail-open.h"
  #include "guarded-list.h"
  #include "latch.h"
  #include "list.h"
  #include "netlink.h"
  #include "ofpbuf.h"
  #include "ofproto-dpif-ipfix.h"
  #include "ofproto-dpif-sflow.h"
  #include "ofproto-dpif-xlate.h"
  #include "ovs-rcu.h"
  #include "packets.h"
  #include "poll-loop.h"
  #include "seq.h"
  #include "unixctl.h"
  #include "openvswitch/vlog.h"
  
  #define MAX_QUEUE_LENGTH 512
  #define UPCALL_MAX_BATCH 64
  #define REVALIDATE_MAX_BATCH 50
  
  VLOG_DEFINE_THIS_MODULE(ofproto_dpif_upcall);
  
  COVERAGE_DEFINE(dumped_duplicate_flow);
  COVERAGE_DEFINE(dumped_new_flow);
  COVERAGE_DEFINE(handler_duplicate_upcall);
  COVERAGE_DEFINE(upcall_ukey_contention);
  COVERAGE_DEFINE(revalidate_missed_dp_flow);
  
  /* A thread that reads upcalls from dpif, forwards each upcall's packet,
   * and possibly sets up a kernel flow as a cache. */
  struct handler {
      struct udpif *udpif;               /* Parent udpif. */
      pthread_t thread;                  /* Thread ID. */
      uint32_t handler_id;               /* Handler id. */
  };
  
  /* In the absence of a multiple-writer multiple-reader datastructure for
   * storing ukeys, we use a large number of cmaps, each with its own lock for
   * writing. */
  #define N_UMAPS 512 /* per udpif. */
  struct umap {
      struct ovs_mutex mutex;            /* Take for writing to the following. */
      struct cmap cmap;                  /* Datapath flow keys. */
  };
  
  /* A thread that processes datapath flows, updates OpenFlow statistics, and
   * updates or removes them if necessary. */
  struct revalidator {
      struct udpif *udpif;               /* Parent udpif. */
      pthread_t thread;                  /* Thread ID. */
      unsigned int id;                   /* ovsthread_id_self(). */
  };
  
  /* An upcall handler for ofproto_dpif.
   *
   * udpif keeps records of two kind of logically separate units:
   *
   * upcall handling
   * ---------------
   *
   *    - An array of 'struct handler's for upcall handling and flow
   *      installation.
   *
   * flow revalidation
   * -----------------
   *
   *    - Revalidation threads which read the datapath flow table and maintains
   *      them.
   */
  struct udpif {
      struct ovs_list list_node;         /* In all_udpifs list. */
  
      struct dpif *dpif;                 /* Datapath handle. */
      struct dpif_backer *backer;        /* Opaque dpif_backer pointer. */
  
      struct handler *handlers;          /* Upcall handlers. */
      size_t n_handlers;
  
      struct revalidator *revalidators;  /* Flow revalidators. */
      size_t n_revalidators;
  
      struct latch exit_latch;           /* Tells child threads to exit. */
  
      /* Revalidation. */
      struct seq *reval_seq;             /* Incremented to force revalidation. */
      bool reval_exit;                   /* Set by leader on 'exit_latch. */
      struct ovs_barrier reval_barrier;  /* Barrier used by revalidators. */
      struct dpif_flow_dump *dump;       /* DPIF flow dump state. */
      long long int dump_duration;       /* Duration of the last flow dump. */
      struct seq *dump_seq;              /* Increments each dump iteration. */
      atomic_bool enable_ufid;           /* If true, skip dumping flow attrs. */
  
      /* These variables provide a mechanism for the main thread to pause
       * all revalidation without having to completely shut the threads down.
       * 'pause_latch' is shared between the main thread and the lead
       * revalidator thread, so when it is desirable to halt revalidation, the
       * main thread will set the latch. 'pause' and 'pause_barrier' are shared
       * by revalidator threads. The lead revalidator will set 'pause' when it
       * observes the latch has been set, and this will cause all revalidator
       * threads to wait on 'pause_barrier' at the beginning of the next
       * revalidation round. */
      bool pause;                        /* Set by leader on 'pause_latch. */
      struct latch pause_latch;          /* Set to force revalidators pause. */
      struct ovs_barrier pause_barrier;  /* Barrier used to pause all */
                                         /* revalidators by main thread. */
  
      /* There are 'N_UMAPS' maps containing 'struct udpif_key' elements.
       *
       * During the flow dump phase, revalidators insert into these with a random
       * distribution. During the garbage collection phase, each revalidator
       * takes care of garbage collecting a slice of these maps. */
      struct umap *ukeys;
  
      /* Datapath flow statistics. */
      unsigned int max_n_flows;
      unsigned int avg_n_flows;
  
      /* Following fields are accessed and modified by different threads. */
      atomic_uint flow_limit;            /* Datapath flow hard limit. */
  
      /* n_flows_mutex prevents multiple threads updating these concurrently. */
      atomic_uint n_flows;               /* Number of flows in the datapath. */
      atomic_llong n_flows_timestamp;    /* Last time n_flows was updated. */
      struct ovs_mutex n_flows_mutex;
  
      /* Following fields are accessed and modified only from the main thread. */
      struct unixctl_conn **conns;       /* Connections waiting on dump_seq. */
      uint64_t conn_seq;                 /* Corresponds to 'dump_seq' when
                                            conns[n_conns-1] was stored. */
      size_t n_conns;                    /* Number of connections waiting. */
  };
  
  enum upcall_type {
      BAD_UPCALL,                 /* Some kind of bug somewhere. */
      MISS_UPCALL,                /* A flow miss.  */
      SFLOW_UPCALL,               /* sFlow sample. */
      FLOW_SAMPLE_UPCALL,         /* Per-flow sampling. */
      IPFIX_UPCALL                /* Per-bridge sampling. */
  };
  
  enum reval_result {
      UKEY_KEEP,
      UKEY_DELETE,
      UKEY_MODIFY
  };
  
  struct upcall {
      struct ofproto_dpif *ofproto;  /* Parent ofproto. */
      const struct recirc_id_node *recirc; /* Recirculation context. */
      bool have_recirc_ref;                /* Reference held on recirc ctx? */
  
      /* The flow and packet are only required to be constant when using
       * dpif-netdev.  If a modification is absolutely necessary, a const cast
       * may be used with other datapaths. */
      const struct flow *flow;       /* Parsed representation of the packet. */
      const ovs_u128 *ufid;          /* Unique identifier for 'flow'. */
      unsigned pmd_id;               /* Datapath poll mode driver id. */
      const struct dp_packet *packet;   /* Packet associated with this upcall. */
      ofp_port_t in_port;            /* OpenFlow in port, or OFPP_NONE. */
      uint16_t mru;                  /* If !0, Maximum receive unit of
                                        fragmented IP packet */
  
      enum dpif_upcall_type type;    /* Datapath type of the upcall. */
      const struct nlattr *userdata; /* Userdata for DPIF_UC_ACTION Upcalls. */
      const struct nlattr *actions;  /* Flow actions in DPIF_UC_ACTION Upcalls. */
  
      bool xout_initialized;         /* True if 'xout' must be uninitialized. */
      struct xlate_out xout;         /* Result of xlate_actions(). */
      struct ofpbuf odp_actions;     /* Datapath actions from xlate_actions(). */
      struct flow_wildcards wc;      /* Dependencies that megaflow must match. */
      struct ofpbuf put_actions;     /* Actions 'put' in the fastpath. */
  
      struct dpif_ipfix *ipfix;      /* IPFIX pointer or NULL. */
      struct dpif_sflow *sflow;      /* SFlow pointer or NULL. */
  
      bool vsp_adjusted;             /* 'packet' and 'flow' were adjusted for
                                        VLAN splinters if true. */
  
      struct udpif_key *ukey;        /* Revalidator flow cache. */
      bool ukey_persists;            /* Set true to keep 'ukey' beyond the
                                        lifetime of this upcall. */
  
      uint64_t dump_seq;             /* udpif->dump_seq at translation time. */
      uint64_t reval_seq;            /* udpif->reval_seq at translation time. */
  
      /* Not used by the upcall callback interface. */
      const struct nlattr *key;      /* Datapath flow key. */
      size_t key_len;                /* Datapath flow key length. */
      const struct nlattr *out_tun_key;  /* Datapath output tunnel key. */
  
      uint64_t odp_actions_stub[1024 / 8]; /* Stub for odp_actions. */
  };
  
  /* 'udpif_key's are responsible for tracking the little bit of state udpif
   * needs to do flow expiration which can't be pulled directly from the
   * datapath.  They may be created by any handler or revalidator thread at any
   * time, and read by any revalidator during the dump phase. They are however
   * each owned by a single revalidator which takes care of destroying them
   * during the garbage-collection phase.
   *
   * The mutex within the ukey protects some members of the ukey. The ukey
   * itself is protected by RCU and is held within a umap in the parent udpif.
   * Adding or removing a ukey from a umap is only safe when holding the
   * corresponding umap lock. */
  struct udpif_key {
      struct cmap_node cmap_node;     /* In parent revalidator 'ukeys' map. */
  
      /* These elements are read only once created, and therefore aren't
       * protected by a mutex. */
      const struct nlattr *key;      /* Datapath flow key. */
      size_t key_len;                /* Length of 'key'. */
      const struct nlattr *mask;     /* Datapath flow mask. */
      size_t mask_len;               /* Length of 'mask'. */
      ovs_u128 ufid;                 /* Unique flow identifier. */
      bool ufid_present;             /* True if 'ufid' is in datapath. */
      uint32_t hash;                 /* Pre-computed hash for 'key'. */
      unsigned pmd_id;               /* Datapath poll mode driver id. */
  
      struct ovs_mutex mutex;                   /* Guards the following. */
      struct dpif_flow_stats stats OVS_GUARDED; /* Last known stats.*/
      long long int created OVS_GUARDED;        /* Estimate of creation time. */
      uint64_t dump_seq OVS_GUARDED;            /* Tracks udpif->dump_seq. */
      uint64_t reval_seq OVS_GUARDED;           /* Tracks udpif->reval_seq. */
      bool flow_exists OVS_GUARDED;             /* Ensures flows are only deleted
                                                   once. */
      /* Datapath flow actions as nlattrs.  Protected by RCU.  Read with
       * ukey_get_actions(), and write with ukey_set_actions(). */
      OVSRCU_TYPE(struct ofpbuf *) actions;
  
      struct xlate_cache *xcache OVS_GUARDED;   /* Cache for xlate entries that
                                                 * are affected by this ukey.
                                                 * Used for stats and learning.*/
      union {
          struct odputil_keybuf buf;
          struct nlattr nla;
      } keybuf, maskbuf;
  
      uint32_t key_recirc_id;   /* Non-zero if reference is held by the ukey. */
      struct recirc_refs recircs;  /* Action recirc IDs with references held. */
  };
  
  /* Datapath operation with optional ukey attached. */
  struct ukey_op {
      struct udpif_key *ukey;
      struct dpif_flow_stats stats; /* Stats for 'op'. */
      struct dpif_op dop;           /* Flow operation. */
  };
  
  static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
  static struct ovs_list all_udpifs = OVS_LIST_INITIALIZER(&all_udpifs);
  
  static size_t recv_upcalls(struct handler *);
  static int process_upcall(struct udpif *, struct upcall *,
                            struct ofpbuf *odp_actions, struct flow_wildcards *);
  static void handle_upcalls(struct udpif *, struct upcall *, size_t n_upcalls);
  static void udpif_stop_threads(struct udpif *);
  static void udpif_start_threads(struct udpif *, size_t n_handlers,
                                  size_t n_revalidators);
  static void udpif_pause_revalidators(struct udpif *);
  static void udpif_resume_revalidators(struct udpif *);
  static void *udpif_upcall_handler(void *);
  static void *udpif_revalidator(void *);
  static unsigned long udpif_get_n_flows(struct udpif *);
  static void revalidate(struct revalidator *);
  static void revalidator_pause(struct revalidator *);
  static void revalidator_sweep(struct revalidator *);
  static void revalidator_purge(struct revalidator *);
  static void upcall_unixctl_show(struct unixctl_conn *conn, int argc,
                                  const char *argv[], void *aux);
  static void upcall_unixctl_disable_megaflows(struct unixctl_conn *, int argc,
                                               const char *argv[], void *aux);
  static void upcall_unixctl_enable_megaflows(struct unixctl_conn *, int argc,
                                              const char *argv[], void *aux);
  static void upcall_unixctl_disable_ufid(struct unixctl_conn *, int argc,
                                                const char *argv[], void *aux);
  static void upcall_unixctl_enable_ufid(struct unixctl_conn *, int argc,
                                               const char *argv[], void *aux);
  static void upcall_unixctl_set_flow_limit(struct unixctl_conn *conn, int argc,
                                              const char *argv[], void *aux);
  static void upcall_unixctl_dump_wait(struct unixctl_conn *conn, int argc,
                                       const char *argv[], void *aux);
  static void upcall_unixctl_purge(struct unixctl_conn *conn, int argc,
                                   const char *argv[], void *aux);
  
  static struct udpif_key *ukey_create_from_upcall(struct upcall *,
                                                   struct flow_wildcards *);
  static int ukey_create_from_dpif_flow(const struct udpif *,
                                        const struct dpif_flow *,
                                        struct udpif_key **);
  static void ukey_get_actions(struct udpif_key *, const struct nlattr **actions,
                               size_t *size);
  static bool ukey_install_start(struct udpif *, struct udpif_key *ukey);
  static bool ukey_install_finish(struct udpif_key *ukey, int error);
  static bool ukey_install(struct udpif *udpif, struct udpif_key *ukey);
  static struct udpif_key *ukey_lookup(struct udpif *udpif,
                                       const ovs_u128 *ufid);
  static int ukey_acquire(struct udpif *, const struct dpif_flow *,
                          struct udpif_key **result, int *error);
  static void ukey_delete__(struct udpif_key *);
  static void ukey_delete(struct umap *, struct udpif_key *);
  static enum upcall_type classify_upcall(enum dpif_upcall_type type,
                                          const struct nlattr *userdata);
  
  static int upcall_receive(struct upcall *, const struct dpif_backer *,
                            const struct dp_packet *packet, enum dpif_upcall_type,
                            const struct nlattr *userdata, const struct flow *,
                            const unsigned int mru,
                            const ovs_u128 *ufid, const unsigned pmd_id);
  static void upcall_uninit(struct upcall *);
  
  static upcall_callback upcall_cb;
  static dp_purge_callback dp_purge_cb;
  
  static atomic_bool enable_megaflows = ATOMIC_VAR_INIT(true);
  static atomic_bool enable_ufid = ATOMIC_VAR_INIT(true);
  
  void
  udpif_init(void)
  {
      static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
      if (ovsthread_once_start(&once)) {
          unixctl_command_register("upcall/show", "", 0, 0, upcall_unixctl_show,
                                   NULL);
          unixctl_command_register("upcall/disable-megaflows", "", 0, 0,
                                   upcall_unixctl_disable_megaflows, NULL);
          unixctl_command_register("upcall/enable-megaflows", "", 0, 0,
                                   upcall_unixctl_enable_megaflows, NULL);
          unixctl_command_register("upcall/disable-ufid", "", 0, 0,
                                   upcall_unixctl_disable_ufid, NULL);
          unixctl_command_register("upcall/enable-ufid", "", 0, 0,
                                   upcall_unixctl_enable_ufid, NULL);
          unixctl_command_register("upcall/set-flow-limit", "", 1, 1,
                                   upcall_unixctl_set_flow_limit, NULL);
          unixctl_command_register("revalidator/wait", "", 0, 0,
                                   upcall_unixctl_dump_wait, NULL);
          unixctl_command_register("revalidator/purge", "", 0, 0,
                                   upcall_unixctl_purge, NULL);
          ovsthread_once_done(&once);
      }
  }
  
  struct udpif *
  udpif_create(struct dpif_backer *backer, struct dpif *dpif)
  {
      struct udpif *udpif = xzalloc(sizeof *udpif);
  
      udpif->dpif = dpif;
      udpif->backer = backer;
      atomic_init(&udpif->flow_limit, MIN(ofproto_flow_limit, 10000));
      udpif->reval_seq = seq_create();
      udpif->dump_seq = seq_create();
      latch_init(&udpif->exit_latch);
      latch_init(&udpif->pause_latch);
      list_push_back(&all_udpifs, &udpif->list_node);
      atomic_init(&udpif->enable_ufid, false);
      atomic_init(&udpif->n_flows, 0);
      atomic_init(&udpif->n_flows_timestamp, LLONG_MIN);
      ovs_mutex_init(&udpif->n_flows_mutex);
      udpif->ukeys = xmalloc(N_UMAPS * sizeof *udpif->ukeys);
      for (int i = 0; i < N_UMAPS; i++) {
          cmap_init(&udpif->ukeys[i].cmap);
          ovs_mutex_init(&udpif->ukeys[i].mutex);
      }
  
      dpif_register_upcall_cb(dpif, upcall_cb, udpif);
      dpif_register_dp_purge_cb(dpif, dp_purge_cb, udpif);
  
      return udpif;
  }
  
  void
  udpif_run(struct udpif *udpif)
  {
      if (udpif->conns && udpif->conn_seq != seq_read(udpif->dump_seq)) {
          int i;
  
          for (i = 0; i < udpif->n_conns; i++) {
              unixctl_command_reply(udpif->conns[i], NULL);
          }
          free(udpif->conns);
          udpif->conns = NULL;
          udpif->n_conns = 0;
      }
  }
  
  void
  udpif_destroy(struct udpif *udpif)
  {
      udpif_stop_threads(udpif);
  
      for (int i = 0; i < N_UMAPS; i++) {
          cmap_destroy(&udpif->ukeys[i].cmap);
          ovs_mutex_destroy(&udpif->ukeys[i].mutex);
      }
      free(udpif->ukeys);
      udpif->ukeys = NULL;
  
      list_remove(&udpif->list_node);
      latch_destroy(&udpif->exit_latch);
      latch_destroy(&udpif->pause_latch);
      seq_destroy(udpif->reval_seq);
      seq_destroy(udpif->dump_seq);
      ovs_mutex_destroy(&udpif->n_flows_mutex);
      free(udpif);
  }
  
  /* Stops the handler and revalidator threads, must be enclosed in
   * ovsrcu quiescent state unless when destroying udpif. */
  static void
  udpif_stop_threads(struct udpif *udpif)
  {
      if (udpif && (udpif->n_handlers != 0 || udpif->n_revalidators != 0)) {
          size_t i;
  
          latch_set(&udpif->exit_latch);
  
          for (i = 0; i < udpif->n_handlers; i++) {
              struct handler *handler = &udpif->handlers[i];
  
              xpthread_join(handler->thread, NULL);
          }
  
          for (i = 0; i < udpif->n_revalidators; i++) {
              xpthread_join(udpif->revalidators[i].thread, NULL);
          }
  
          dpif_disable_upcall(udpif->dpif);
  
          for (i = 0; i < udpif->n_revalidators; i++) {
              struct revalidator *revalidator = &udpif->revalidators[i];
  
              /* Delete ukeys, and delete all flows from the datapath to prevent
               * double-counting stats. */
              revalidator_purge(revalidator);
          }
  
          latch_poll(&udpif->exit_latch);
  
          ovs_barrier_destroy(&udpif->reval_barrier);
          ovs_barrier_destroy(&udpif->pause_barrier);
  
          free(udpif->revalidators);
          udpif->revalidators = NULL;
          udpif->n_revalidators = 0;
  
          free(udpif->handlers);
          udpif->handlers = NULL;
          udpif->n_handlers = 0;
      }
  }
  
  /* Starts the handler and revalidator threads, must be enclosed in
   * ovsrcu quiescent state. */
  static void
  udpif_start_threads(struct udpif *udpif, size_t n_handlers,
                      size_t n_revalidators)
  {
      if (udpif && n_handlers && n_revalidators) {
          size_t i;
          bool enable_ufid;
  
          udpif->n_handlers = n_handlers;
          udpif->n_revalidators = n_revalidators;
  
          udpif->handlers = xzalloc(udpif->n_handlers * sizeof *udpif->handlers);
          for (i = 0; i < udpif->n_handlers; i++) {
              struct handler *handler = &udpif->handlers[i];
  
              handler->udpif = udpif;
              handler->handler_id = i;
              handler->thread = ovs_thread_create(
                  "handler", udpif_upcall_handler, handler);
          }
  
          enable_ufid = ofproto_dpif_get_enable_ufid(udpif->backer);
          atomic_init(&udpif->enable_ufid, enable_ufid);
          dpif_enable_upcall(udpif->dpif);
  
          ovs_barrier_init(&udpif->reval_barrier, udpif->n_revalidators);
          ovs_barrier_init(&udpif->pause_barrier, udpif->n_revalidators + 1);
          udpif->reval_exit = false;
          udpif->pause = false;
          udpif->revalidators = xzalloc(udpif->n_revalidators
                                        * sizeof *udpif->revalidators);
          for (i = 0; i < udpif->n_revalidators; i++) {
              struct revalidator *revalidator = &udpif->revalidators[i];
  
              revalidator->udpif = udpif;
              revalidator->thread = ovs_thread_create(
                  "revalidator", udpif_revalidator, revalidator);
          }
      }
  }
  
  /* Pauses all revalidators.  Should only be called by the main thread.
   * When function returns, all revalidators are paused and will proceed
   * only after udpif_resume_revalidators() is called. */
  static void
  udpif_pause_revalidators(struct udpif *udpif)
  {
      if (ofproto_dpif_backer_enabled(udpif->backer)) {
          latch_set(&udpif->pause_latch);
          ovs_barrier_block(&udpif->pause_barrier);
      }
  }
  
  /* Resumes the pausing of revalidators.  Should only be called by the
   * main thread. */
  static void
  udpif_resume_revalidators(struct udpif *udpif)
  {
      if (ofproto_dpif_backer_enabled(udpif->backer)) {
          latch_poll(&udpif->pause_latch);
          ovs_barrier_block(&udpif->pause_barrier);
      }
  }
  
  /* Tells 'udpif' how many threads it should use to handle upcalls.
   * 'n_handlers' and 'n_revalidators' can never be zero.  'udpif''s
   * datapath handle must have packet reception enabled before starting
   * threads. */
  void
  udpif_set_threads(struct udpif *udpif, size_t n_handlers,
                    size_t n_revalidators)
  {
      ovs_assert(udpif);
      ovs_assert(n_handlers && n_revalidators);
  
      ovsrcu_quiesce_start();
      if (udpif->n_handlers != n_handlers
          || udpif->n_revalidators != n_revalidators) {
          udpif_stop_threads(udpif);
      }
  
      if (!udpif->handlers && !udpif->revalidators) {
          int error;
  
          error = dpif_handlers_set(udpif->dpif, n_handlers);
          if (error) {
              VLOG_ERR("failed to configure handlers in dpif %s: %s",
                       dpif_name(udpif->dpif), ovs_strerror(error));
              return;
          }
  
          udpif_start_threads(udpif, n_handlers, n_revalidators);
      }
      ovsrcu_quiesce_end();
  }
  
  /* Waits for all ongoing upcall translations to complete.  This ensures that
   * there are no transient references to any removed ofprotos (or other
   * objects).  In particular, this should be called after an ofproto is removed
   * (e.g. via xlate_remove_ofproto()) but before it is destroyed. */
  void
  udpif_synchronize(struct udpif *udpif)
  {
      /* This is stronger than necessary.  It would be sufficient to ensure
       * (somehow) that each handler and revalidator thread had passed through
       * its main loop once. */
      size_t n_handlers = udpif->n_handlers;
      size_t n_revalidators = udpif->n_revalidators;
  
      ovsrcu_quiesce_start();
      udpif_stop_threads(udpif);
      udpif_start_threads(udpif, n_handlers, n_revalidators);
      ovsrcu_quiesce_end();
  }
  
  /* Notifies 'udpif' that something changed which may render previous
   * xlate_actions() results invalid. */
  void
  udpif_revalidate(struct udpif *udpif)
  {
      seq_change(udpif->reval_seq);
  }
  
  /* Returns a seq which increments every time 'udpif' pulls stats from the
   * datapath.  Callers can use this to get a sense of when might be a good time
   * to do periodic work which relies on relatively up to date statistics. */
  struct seq *
  udpif_dump_seq(struct udpif *udpif)
  {
      return udpif->dump_seq;
  }
  
  void
  udpif_get_memory_usage(struct udpif *udpif, struct simap *usage)
  {
      size_t i;
  
      simap_increase(usage, "handlers", udpif->n_handlers);
  
      simap_increase(usage, "revalidators", udpif->n_revalidators);
      for (i = 0; i < N_UMAPS; i++) {
          simap_increase(usage, "udpif keys", cmap_count(&udpif->ukeys[i].cmap));
      }
  }
  
  /* Remove flows from a single datapath. */
  void
  udpif_flush(struct udpif *udpif)
  {
      size_t n_handlers, n_revalidators;
  
      n_handlers = udpif->n_handlers;
      n_revalidators = udpif->n_revalidators;
  
      ovsrcu_quiesce_start();
  
      udpif_stop_threads(udpif);
      dpif_flow_flush(udpif->dpif);
      udpif_start_threads(udpif, n_handlers, n_revalidators);
  
      ovsrcu_quiesce_end();
  }
  
  /* Removes all flows from all datapaths. */
  static void
  udpif_flush_all_datapaths(void)
  {
      struct udpif *udpif;
  
      LIST_FOR_EACH (udpif, list_node, &all_udpifs) {
          udpif_flush(udpif);
      }
  }
  
  static bool
  udpif_use_ufid(struct udpif *udpif)
  {
      bool enable;
  
      atomic_read_relaxed(&enable_ufid, &enable);
      return enable && ofproto_dpif_get_enable_ufid(udpif->backer);
  }
  
  
  static unsigned long
  udpif_get_n_flows(struct udpif *udpif)
  {
      long long int time, now;
      unsigned long flow_count;
  
      now = time_msec();
      atomic_read_relaxed(&udpif->n_flows_timestamp, &time);
      if (time < now - 100 && !ovs_mutex_trylock(&udpif->n_flows_mutex)) {
          struct dpif_dp_stats stats;
  
          atomic_store_relaxed(&udpif->n_flows_timestamp, now);
          dpif_get_dp_stats(udpif->dpif, &stats);
          flow_count = stats.n_flows;
          atomic_store_relaxed(&udpif->n_flows, flow_count);
          ovs_mutex_unlock(&udpif->n_flows_mutex);
      } else {
          atomic_read_relaxed(&udpif->n_flows, &flow_count);
      }
      return flow_count;
  }
  
  /* The upcall handler thread tries to read a batch of UPCALL_MAX_BATCH
   * upcalls from dpif, processes the batch and installs corresponding flows
   * in dpif. */
  static void *
  udpif_upcall_handler(void *arg)
  {
      struct handler *handler = arg;
      struct udpif *udpif = handler->udpif;
  
      while (!latch_is_set(&handler->udpif->exit_latch)) {
          if (recv_upcalls(handler)) {
              poll_immediate_wake();
          } else {
              dpif_recv_wait(udpif->dpif, handler->handler_id);
              latch_wait(&udpif->exit_latch);
          }
          poll_block();
      }
  
      return NULL;
  }
  
  static size_t
  recv_upcalls(struct handler *handler)
  {
      struct udpif *udpif = handler->udpif;
      uint64_t recv_stubs[UPCALL_MAX_BATCH][512 / 8];
      struct ofpbuf recv_bufs[UPCALL_MAX_BATCH];
      struct dpif_upcall dupcalls[UPCALL_MAX_BATCH];
      struct upcall upcalls[UPCALL_MAX_BATCH];
      struct flow flows[UPCALL_MAX_BATCH];
      size_t n_upcalls, i;
  
      n_upcalls = 0;
      while (n_upcalls < UPCALL_MAX_BATCH) {
          struct ofpbuf *recv_buf = &recv_bufs[n_upcalls];
          struct dpif_upcall *dupcall = &dupcalls[n_upcalls];
          struct upcall *upcall = &upcalls[n_upcalls];
          struct flow *flow = &flows[n_upcalls];
          unsigned int mru;
          int error;
  
          ofpbuf_use_stub(recv_buf, recv_stubs[n_upcalls],
                          sizeof recv_stubs[n_upcalls]);
          if (dpif_recv(udpif->dpif, handler->handler_id, dupcall, recv_buf)) {
              ofpbuf_uninit(recv_buf);
              break;
          }
  
          if (odp_flow_key_to_flow(dupcall->key, dupcall->key_len, flow)
              == ODP_FIT_ERROR) {
              goto free_dupcall;
          }
  
          if (dupcall->mru) {
              mru = nl_attr_get_u16(dupcall->mru);
          } else {
              mru = 0;
          }
  
          error = upcall_receive(upcall, udpif->backer, &dupcall->packet,
                                 dupcall->type, dupcall->userdata, flow, mru,
                                 &dupcall->ufid, PMD_ID_NULL);
          if (error) {
              if (error == ENODEV) {
                  /* Received packet on datapath port for which we couldn't
                   * associate an ofproto.  This can happen if a port is removed
                   * while traffic is being received.  Print a rate-limited
                   * message in case it happens frequently. */
                  dpif_flow_put(udpif->dpif, DPIF_FP_CREATE, dupcall->key,
                                dupcall->key_len, NULL, 0, NULL, 0,
                                &dupcall->ufid, PMD_ID_NULL, NULL);
                  VLOG_INFO_RL(&rl, "received packet on unassociated datapath "
                               "port %"PRIu32, flow->in_port.odp_port);
              }
              goto free_dupcall;
          }
  
          upcall->key = dupcall->key;
          upcall->key_len = dupcall->key_len;
          upcall->ufid = &dupcall->ufid;
  
          upcall->out_tun_key = dupcall->out_tun_key;
          upcall->actions = dupcall->actions;
  
          if (vsp_adjust_flow(upcall->ofproto, flow, &dupcall->packet)) {
              upcall->vsp_adjusted = true;
          }
  
          pkt_metadata_from_flow(&dupcall->packet.md, flow);
          flow_extract(&dupcall->packet, flow);
  
          error = process_upcall(udpif, upcall,
                                 &upcall->odp_actions, &upcall->wc);
          if (error) {
              goto cleanup;
          }
  
          n_upcalls++;
          continue;
  
  cleanup:
          upcall_uninit(upcall);
  free_dupcall:
          dp_packet_uninit(&dupcall->packet);
          ofpbuf_uninit(recv_buf);
      }
  
      if (n_upcalls) {
          handle_upcalls(handler->udpif, upcalls, n_upcalls);
          for (i = 0; i < n_upcalls; i++) {
              dp_packet_uninit(&dupcalls[i].packet);
              ofpbuf_uninit(&recv_bufs[i]);
              upcall_uninit(&upcalls[i]);
          }
      }
  
      return n_upcalls;
  }
  
  static void *
  udpif_revalidator(void *arg)
  {
      /* Used by all revalidators. */
      struct revalidator *revalidator = arg;
      struct udpif *udpif = revalidator->udpif;
      bool leader = revalidator == &udpif->revalidators[0];
  
      /* Used only by the leader. */
      long long int start_time = 0;
      uint64_t last_reval_seq = 0;
      size_t n_flows = 0;
  
      revalidator->id = ovsthread_id_self();
      for (;;) {
          if (leader) {
              uint64_t reval_seq;
  
              recirc_run(); /* Recirculation cleanup. */
  
              reval_seq = seq_read(udpif->reval_seq);
              last_reval_seq = reval_seq;
  
              n_flows = udpif_get_n_flows(udpif);
              udpif->max_n_flows = MAX(n_flows, udpif->max_n_flows);
              udpif->avg_n_flows = (udpif->avg_n_flows + n_flows) / 2;
  
              /* Only the leader checks the pause latch to prevent a race where
               * some threads think it's false and proceed to block on
               * reval_barrier and others think it's true and block indefinitely
               * on the pause_barrier */
              udpif->pause = latch_is_set(&udpif->pause_latch);
  
              /* Only the leader checks the exit latch to prevent a race where
               * some threads think it's true and exit and others think it's
               * false and block indefinitely on the reval_barrier */
              udpif->reval_exit = latch_is_set(&udpif->exit_latch);
  
              start_time = time_msec();
              if (!udpif->reval_exit) {
                  bool terse_dump;
  
                  terse_dump = udpif_use_ufid(udpif);
                  udpif->dump = dpif_flow_dump_create(udpif->dpif, terse_dump);
              }
          }
  
          /* Wait for the leader to start the flow dump. */
          ovs_barrier_block(&udpif->reval_barrier);
          if (udpif->pause) {
              revalidator_pause(revalidator);
          }
  
          if (udpif->reval_exit) {
              break;
          }
          revalidate(revalidator);
  
          /* Wait for all flows to have been dumped before we garbage collect. */
          ovs_barrier_block(&udpif->reval_barrier);
          revalidator_sweep(revalidator);
  
          /* Wait for all revalidators to finish garbage collection. */
          ovs_barrier_block(&udpif->reval_barrier);
  
          if (leader) {
              unsigned int flow_limit;
              long long int duration;
  
              atomic_read_relaxed(&udpif->flow_limit, &flow_limit);
  
              dpif_flow_dump_destroy(udpif->dump);
              seq_change(udpif->dump_seq);
  
              duration = MAX(time_msec() - start_time, 1);
              udpif->dump_duration = duration;
              if (duration > 2000) {
                  flow_limit /= duration / 1000;
              } else if (duration > 1300) {
                  flow_limit = flow_limit * 3 / 4;
              } else if (duration < 1000 && n_flows > 2000
                         && flow_limit < n_flows * 1000 / duration) {
                  flow_limit += 1000;
              }
              flow_limit = MIN(ofproto_flow_limit, MAX(flow_limit, 1000));
              atomic_store_relaxed(&udpif->flow_limit, flow_limit);
  
              if (duration > 2000) {
                  VLOG_INFO("Spent an unreasonably long %lldms dumping flows",
                            duration);
              }
  
              poll_timer_wait_until(start_time + MIN(ofproto_max_idle, 500));
              seq_wait(udpif->reval_seq, last_reval_seq);
              latch_wait(&udpif->exit_latch);
              latch_wait(&udpif->pause_latch);
              poll_block();
          }
      }
  
      return NULL;
  }
  
  static enum upcall_type
  classify_upcall(enum dpif_upcall_type type, const struct nlattr *userdata)
  {
      union user_action_cookie cookie;
      size_t userdata_len;
  
      /* First look at the upcall type. */
      switch (type) {
      case DPIF_UC_ACTION:
          break;
  
      case DPIF_UC_MISS:
          return MISS_UPCALL;
  
      case DPIF_N_UC_TYPES:
      default:
          VLOG_WARN_RL(&rl, "upcall has unexpected type %"PRIu32, type);
          return BAD_UPCALL;
      }
  
      /* "action" upcalls need a closer look. */
      if (!userdata) {
          VLOG_WARN_RL(&rl, "action upcall missing cookie");
          return BAD_UPCALL;
      }
      userdata_len = nl_attr_get_size(userdata);
      if (userdata_len < sizeof cookie.type
          || userdata_len > sizeof cookie) {
          VLOG_WARN_RL(&rl, "action upcall cookie has unexpected size %"PRIuSIZE,
                       userdata_len);
          return BAD_UPCALL;
      }
      memset(&cookie, 0, sizeof cookie);
      memcpy(&cookie, nl_attr_get(userdata), userdata_len);
      if (userdata_len == MAX(8, sizeof cookie.sflow)
          && cookie.type == USER_ACTION_COOKIE_SFLOW) {
          return SFLOW_UPCALL;
      } else if (userdata_len == MAX(8, sizeof cookie.slow_path)
                 && cookie.type == USER_ACTION_COOKIE_SLOW_PATH) {
          return MISS_UPCALL;
      } else if (userdata_len == MAX(8, sizeof cookie.flow_sample)
                 && cookie.type == USER_ACTION_COOKIE_FLOW_SAMPLE) {
          return FLOW_SAMPLE_UPCALL;
      } else if (userdata_len == MAX(8, sizeof cookie.ipfix)
                 && cookie.type == USER_ACTION_COOKIE_IPFIX) {
          return IPFIX_UPCALL;
      } else {
          VLOG_WARN_RL(&rl, "invalid user cookie of type %"PRIu16
                       " and size %"PRIuSIZE, cookie.type, userdata_len);
          return BAD_UPCALL;
      }
  }
  
  /* Calculates slow path actions for 'xout'.  'buf' must statically be
   * initialized with at least 128 bytes of space. */
  static void
  compose_slow_path(struct udpif *udpif, struct xlate_out *xout,
                    const struct flow *flow, odp_port_t odp_in_port,
                    struct ofpbuf *buf)
  {
      union user_action_cookie cookie;
      odp_port_t port;
      uint32_t pid;
  
      cookie.type = USER_ACTION_COOKIE_SLOW_PATH;
      cookie.slow_path.unused = 0;
      cookie.slow_path.reason = xout->slow;
  
      port = xout->slow & (SLOW_CFM | SLOW_BFD | SLOW_LACP | SLOW_STP)
          ? ODPP_NONE
          : odp_in_port;
      pid = dpif_port_get_pid(udpif->dpif, port, flow_hash_5tuple(flow, 0));
      odp_put_userspace_action(pid, &cookie, sizeof cookie.slow_path,
                               ODPP_NONE, false, buf);
  }
  
  /* If there is no error, the upcall must be destroyed with upcall_uninit()
   * before quiescing, as the referred objects are guaranteed to exist only
   * until the calling thread quiesces.  Otherwise, do not call upcall_uninit()
   * since the 'upcall->put_actions' remains uninitialized. */
  static int
  upcall_receive(struct upcall *upcall, const struct dpif_backer *backer,
                 const struct dp_packet *packet, enum dpif_upcall_type type,
                 const struct nlattr *userdata, const struct flow *flow,
                 const unsigned int mru,
                 const ovs_u128 *ufid, const unsigned pmd_id)
  {
      int error;
  
      error = xlate_lookup(backer, flow, &upcall->ofproto, &upcall->ipfix,
                           &upcall->sflow, NULL, &upcall->in_port);
      if (error) {
          return error;
      }
  
      upcall->recirc = NULL;
      upcall->have_recirc_ref = false;
      upcall->flow = flow;
      upcall->packet = packet;
      upcall->ufid = ufid;
      upcall->pmd_id = pmd_id;
      upcall->type = type;
      upcall->userdata = userdata;
      ofpbuf_use_stub(&upcall->odp_actions, upcall->odp_actions_stub,
                      sizeof upcall->odp_actions_stub);
      ofpbuf_init(&upcall->put_actions, 0);
  
      upcall->xout_initialized = false;
      upcall->vsp_adjusted = false;
      upcall->ukey_persists = false;
  
      upcall->ukey = NULL;
      upcall->key = NULL;
      upcall->key_len = 0;
      upcall->mru = mru;
  
      upcall->out_tun_key = NULL;
      upcall->actions = NULL;
  
      return 0;
  }
  
  static void
  upcall_xlate(struct udpif *udpif, struct upcall *upcall,
               struct ofpbuf *odp_actions, struct flow_wildcards *wc)
  {
      struct dpif_flow_stats stats;
      struct xlate_in xin;
  
      stats.n_packets = 1;
      stats.n_bytes = dp_packet_size(upcall->packet);
      stats.used = time_msec();
      stats.tcp_flags = ntohs(upcall->flow->tcp_flags);
  
      xlate_in_init(&xin, upcall->ofproto, upcall->flow, upcall->in_port, NULL,
                    stats.tcp_flags, upcall->packet, wc, odp_actions);
  
      if (upcall->type == DPIF_UC_MISS) {
          xin.resubmit_stats = &stats;
  
          if (xin.recirc) {
              /* We may install a datapath flow only if we get a reference to the
               * recirculation context (otherwise we could have recirculation
               * upcalls using recirculation ID for which no context can be
               * found).  We may still execute the flow's actions even if we
               * don't install the flow. */
              upcall->recirc = xin.recirc;
              upcall->have_recirc_ref = recirc_id_node_try_ref_rcu(xin.recirc);
          }
      } else {
          /* For non-miss upcalls, we are either executing actions (one of which
           * is an userspace action) for an upcall, in which case the stats have
           * already been taken care of, or there's a flow in the datapath which
           * this packet was accounted to.  Presumably the revalidators will deal
           * with pushing its stats eventually. */
      }
  
      upcall->dump_seq = seq_read(udpif->dump_seq);
      upcall->reval_seq = seq_read(udpif->reval_seq);
      xlate_actions(&xin, &upcall->xout);
      upcall->xout_initialized = true;
  
      /* Special case for fail-open mode.
       *
       * If we are in fail-open mode, but we are connected to a controller too,
       * then we should send the packet up to the controller in the hope that it
       * will try to set up a flow and thereby allow us to exit fail-open.
       *
       * See the top-level comment in fail-open.c for more information.
       *
       * Copy packets before they are modified by execution. */
      if (upcall->xout.fail_open) {
          const struct dp_packet *packet = upcall->packet;
          struct ofproto_packet_in *pin;
  
          pin = xmalloc(sizeof *pin);
          pin->up.packet = xmemdup(dp_packet_data(packet), dp_packet_size(packet));
          pin->up.packet_len = dp_packet_size(packet);
          pin->up.reason = OFPR_NO_MATCH;
          pin->up.table_id = 0;
          pin->up.cookie = OVS_BE64_MAX;
          flow_get_metadata(upcall->flow, &pin->up.flow_metadata);
          pin->send_len = 0; /* Not used for flow table misses. */
          pin->miss_type = OFPROTO_PACKET_IN_NO_MISS;
          ofproto_dpif_send_packet_in(upcall->ofproto, pin);
      }
  
      if (!upcall->xout.slow) {
          ofpbuf_use_const(&upcall->put_actions,
                           odp_actions->data, odp_actions->size);
      } else {
          /* upcall->put_actions already initialized by upcall_receive(). */
          compose_slow_path(udpif, &upcall->xout, upcall->flow,
                            upcall->flow->in_port.odp_port,
                            &upcall->put_actions);
      }
  
      /* This function is also called for slow-pathed flows.  As we are only
       * going to create new datapath flows for actual datapath misses, there is
       * no point in creating a ukey otherwise. */
      if (upcall->type == DPIF_UC_MISS) {
          upcall->ukey = ukey_create_from_upcall(upcall, wc);
      }
  }
  
  static void
  upcall_uninit(struct upcall *upcall)
  {
      if (upcall) {
          if (upcall->xout_initialized) {
              xlate_out_uninit(&upcall->xout);
          }
          ofpbuf_uninit(&upcall->odp_actions);
          ofpbuf_uninit(&upcall->put_actions);
          if (upcall->ukey) {
              if (!upcall->ukey_persists) {
                  ukey_delete__(upcall->ukey);
              }
          } else if (upcall->have_recirc_ref) {
              /* The reference was transferred to the ukey if one was created. */
              recirc_id_node_unref(upcall->recirc);
          }
      }
  }
  
  static int
  upcall_cb(const struct dp_packet *packet, const struct flow *flow, ovs_u128 *ufid,
            unsigned pmd_id, enum dpif_upcall_type type,
            const struct nlattr *userdata, struct ofpbuf *actions,
            struct flow_wildcards *wc, struct ofpbuf *put_actions, void *aux)
  {
      static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 1);
      struct udpif *udpif = aux;
      unsigned int flow_limit;
      struct upcall upcall;
      bool megaflow;
      int error;
  
      atomic_read_relaxed(&enable_megaflows, &megaflow);
      atomic_read_relaxed(&udpif->flow_limit, &flow_limit);
  
      error = upcall_receive(&upcall, udpif->backer, packet, type, userdata,
                             flow, 0, ufid, pmd_id);
      if (error) {
          return error;
      }
  
      error = process_upcall(udpif, &upcall, actions, wc);
      if (error) {
          goto out;
      }
  
      if (upcall.xout.slow && put_actions) {
          ofpbuf_put(put_actions, upcall.put_actions.data,
                     upcall.put_actions.size);
      }
  
      if (OVS_UNLIKELY(!megaflow)) {
          flow_wildcards_init_for_packet(wc, flow);
      }
  
      if (udpif_get_n_flows(udpif) >= flow_limit) {
          VLOG_WARN_RL(&rl, "upcall_cb failure: datapath flow limit reached");
          error = ENOSPC;
          goto out;
      }
  
      /* Prevent miss flow installation if the key has recirculation ID but we
       * were not able to get a reference on it. */
      if (type == DPIF_UC_MISS && upcall.recirc && !upcall.have_recirc_ref) {
          VLOG_WARN_RL(&rl, "upcall_cb failure: no reference for recirc flow");
          error = ENOSPC;
          goto out;
      }
  
      if (upcall.ukey && !ukey_install(udpif, upcall.ukey)) {
          VLOG_WARN_RL(&rl, "upcall_cb failure: ukey installation fails");
          error = ENOSPC;
      }
  out:
      if (!error) {
          upcall.ukey_persists = true;
      }
      upcall_uninit(&upcall);
      return error;
  }
  
  static int
  process_upcall(struct udpif *udpif, struct upcall *upcall,
                 struct ofpbuf *odp_actions, struct flow_wildcards *wc)
  {
      const struct nlattr *userdata = upcall->userdata;
      const struct dp_packet *packet = upcall->packet;
      const struct flow *flow = upcall->flow;
  
      switch (classify_upcall(upcall->type, userdata)) {
      case MISS_UPCALL:
          upcall_xlate(udpif, upcall, odp_actions, wc);
          return 0;
  
      case SFLOW_UPCALL:
          if (upcall->sflow) {
              union user_action_cookie cookie;
              const struct nlattr *actions;
              size_t actions_len = 0;
              struct dpif_sflow_actions sflow_actions;
              memset(&sflow_actions, 0, sizeof sflow_actions);
              memset(&cookie, 0, sizeof cookie);
              memcpy(&cookie, nl_attr_get(userdata), sizeof cookie.sflow);
              if (upcall->actions) {
                  /* Actions were passed up from datapath. */
                  actions = nl_attr_get(upcall->actions);
                  actions_len = nl_attr_get_size(upcall->actions);
                  if (actions && actions_len) {
                      dpif_sflow_read_actions(flow, actions, actions_len,
                                              &sflow_actions);
                  }
              }
              if (actions_len == 0) {
                  /* Lookup actions in userspace cache. */
                  struct udpif_key *ukey = ukey_lookup(udpif, upcall->ufid);
                  if (ukey) {
                      ukey_get_actions(ukey, &actions, &actions_len);
                      dpif_sflow_read_actions(flow, actions, actions_len,
                                              &sflow_actions);
                  }
              }
              dpif_sflow_received(upcall->sflow, packet, flow,
                                  flow->in_port.odp_port, &cookie,
                                  actions_len > 0 ? &sflow_actions : NULL);
          }
          break;
  
      case IPFIX_UPCALL:
          if (upcall->ipfix) {
              union user_action_cookie cookie;
              struct flow_tnl output_tunnel_key;
  
              memset(&cookie, 0, sizeof cookie);
              memcpy(&cookie, nl_attr_get(userdata), sizeof cookie.ipfix);
  
              if (upcall->out_tun_key) {
                  odp_tun_key_from_attr(upcall->out_tun_key, false,
                                        &output_tunnel_key);
              }
              dpif_ipfix_bridge_sample(upcall->ipfix, packet, flow,
                                       flow->in_port.odp_port,
                                       cookie.ipfix.output_odp_port,
                                       upcall->out_tun_key ?
                                           &output_tunnel_key : NULL);
          }
          break;
  
      case FLOW_SAMPLE_UPCALL:
          if (upcall->ipfix) {
              union user_action_cookie cookie;
  
              memset(&cookie, 0, sizeof cookie);
              memcpy(&cookie, nl_attr_get(userdata), sizeof cookie.flow_sample);
  
              /* The flow reflects exactly the contents of the packet.
               * Sample the packet using it. */
              dpif_ipfix_flow_sample(upcall->ipfix, packet, flow,
                                     cookie.flow_sample.collector_set_id,
                                     cookie.flow_sample.probability,
                                     cookie.flow_sample.obs_domain_id,
                                     cookie.flow_sample.obs_point_id);
          }
          break;
  
      case BAD_UPCALL:
          break;
      }
  
      return EAGAIN;
  }
  
  static void
  handle_upcalls(struct udpif *udpif, struct upcall *upcalls,
                 size_t n_upcalls)
  {
      struct dpif_op *opsp[UPCALL_MAX_BATCH * 2];
      struct ukey_op ops[UPCALL_MAX_BATCH * 2];
      unsigned int flow_limit;
      size_t n_ops, n_opsp, i;
      bool may_put;
  
      atomic_read_relaxed(&udpif->flow_limit, &flow_limit);
  
      may_put = udpif_get_n_flows(udpif) < flow_limit;
  
      /* Handle the packets individually in order of arrival.
       *
       *   - For SLOW_CFM, SLOW_LACP, SLOW_STP, and SLOW_BFD, translation is what
       *     processes received packets for these protocols.
       *
       *   - For SLOW_CONTROLLER, translation sends the packet to the OpenFlow
       *     controller.
       *
       * The loop fills 'ops' with an array of operations to execute in the
       * datapath. */
      n_ops = 0;
      for (i = 0; i < n_upcalls; i++) {
          struct upcall *upcall = &upcalls[i];
          const struct dp_packet *packet = upcall->packet;
          struct ukey_op *op;
  
          if (upcall->vsp_adjusted) {
              /* This packet was received on a VLAN splinter port.  We added a
               * VLAN to the packet to make the packet resemble the flow, but the
               * actions were composed assuming that the packet contained no
               * VLAN.  So, we must remove the VLAN header from the packet before
               * trying to execute the actions. */
              if (upcall->odp_actions.size) {
                  eth_pop_vlan(CONST_CAST(struct dp_packet *, upcall->packet));
              }
  
              /* Remove the flow vlan tags inserted by vlan splinter logic
               * to ensure megaflow masks generated match the data path flow. */
              CONST_CAST(struct flow *, upcall->flow)->vlan_tci = 0;
          }
  
          /* Do not install a flow into the datapath if:
           *
           *    - The datapath already has too many flows.
           *
           *    - We received this packet via some flow installed in the kernel
           *      already.
           *
           *    - Upcall was a recirculation but we do not have a reference to
           *      to the recirculation ID. */
          if (may_put && upcall->type == DPIF_UC_MISS &&
              (!upcall->recirc || upcall->have_recirc_ref)) {
              struct udpif_key *ukey = upcall->ukey;
  
              upcall->ukey_persists = true;
              op = &ops[n_ops++];
  
              op->ukey = ukey;
              op->dop.type = DPIF_OP_FLOW_PUT;
              op->dop.u.flow_put.flags = DPIF_FP_CREATE;
              op->dop.u.flow_put.key = ukey->key;
              op->dop.u.flow_put.key_len = ukey->key_len;
              op->dop.u.flow_put.mask = ukey->mask;
              op->dop.u.flow_put.mask_len = ukey->mask_len;
              op->dop.u.flow_put.ufid = upcall->ufid;
              op->dop.u.flow_put.stats = NULL;
              ukey_get_actions(ukey, &op->dop.u.flow_put.actions,
                               &op->dop.u.flow_put.actions_len);
          }
  
          if (upcall->odp_actions.size) {
              op = &ops[n_ops++];
              op->ukey = NULL;
              op->dop.type = DPIF_OP_EXECUTE;
              op->dop.u.execute.packet = CONST_CAST(struct dp_packet *, packet);
              odp_key_to_pkt_metadata(upcall->key, upcall->key_len,
                                      &op->dop.u.execute.packet->md);
              op->dop.u.execute.actions = upcall->odp_actions.data;
              op->dop.u.execute.actions_len = upcall->odp_actions.size;
              op->dop.u.execute.needs_help = (upcall->xout.slow & SLOW_ACTION) != 0;
              op->dop.u.execute.probe = false;
              op->dop.u.execute.mtu = upcall->mru;
          }
      }
  
      /* Execute batch.
       *
       * We install ukeys before installing the flows, locking them for exclusive
       * access by this thread for the period of installation. This ensures that
       * other threads won't attempt to delete the flows as we are creating them.
       */
      n_opsp = 0;
      for (i = 0; i < n_ops; i++) {
          struct udpif_key *ukey = ops[i].ukey;
  
          if (ukey) {
              /* If we can't install the ukey, don't install the flow. */
              if (!ukey_install_start(udpif, ukey)) {
                  ukey_delete__(ukey);
                  ops[i].ukey = NULL;
                  continue;
              }
          }
          opsp[n_opsp++] = &ops[i].dop;
      }
      dpif_operate(udpif->dpif, opsp, n_opsp);
      for (i = 0; i < n_ops; i++) {
          if (ops[i].ukey) {
              ukey_install_finish(ops[i].ukey, ops[i].dop.error);
          }
      }
  }
  
  static uint32_t
  get_ufid_hash(const ovs_u128 *ufid)
  {
      return ufid->u32[0];
  }
  
  static struct udpif_key *
  ukey_lookup(struct udpif *udpif, const ovs_u128 *ufid)
  {
      struct udpif_key *ukey;
      int idx = get_ufid_hash(ufid) % N_UMAPS;
      struct cmap *cmap = &udpif->ukeys[idx].cmap;
  
      CMAP_FOR_EACH_WITH_HASH (ukey, cmap_node, get_ufid_hash(ufid), cmap) {
          if (ovs_u128_equals(&ukey->ufid, ufid)) {
              return ukey;
          }
      }
      return NULL;
  }
  
  /* Provides safe lockless access of RCU protected 'ukey->actions'.  Callers may
   * alternatively access the field directly if they take 'ukey->mutex'. */
  static void
  ukey_get_actions(struct udpif_key *ukey, const struct nlattr **actions, size_t *size)
  {
      const struct ofpbuf *buf = ovsrcu_get(struct ofpbuf *, &ukey->actions);
      *actions = buf->data;
      *size = buf->size;
  }
  
  static void
  ukey_set_actions(struct udpif_key *ukey, const struct ofpbuf *actions)
  {
      ovsrcu_postpone(ofpbuf_delete,
                      ovsrcu_get_protected(struct ofpbuf *, &ukey->actions));
      ovsrcu_set(&ukey->actions, ofpbuf_clone(actions));
  }
  
  static struct udpif_key *
  ukey_create__(const struct nlattr *key, size_t key_len,
                const struct nlattr *mask, size_t mask_len,
                bool ufid_present, const ovs_u128 *ufid,
                const unsigned pmd_id, const struct ofpbuf *actions,
                uint64_t dump_seq, uint64_t reval_seq, long long int used,
                uint32_t key_recirc_id, struct xlate_out *xout)
      OVS_NO_THREAD_SAFETY_ANALYSIS
  {
      struct udpif_key *ukey = xmalloc(sizeof *ukey);
  
      memcpy(&ukey->keybuf, key, key_len);
      ukey->key = &ukey->keybuf.nla;
      ukey->key_len = key_len;
      memcpy(&ukey->maskbuf, mask, mask_len);
      ukey->mask = &ukey->maskbuf.nla;
      ukey->mask_len = mask_len;
      ukey->ufid_present = ufid_present;
      ukey->ufid = *ufid;
      ukey->pmd_id = pmd_id;
      ukey->hash = get_ufid_hash(&ukey->ufid);
  
      ovsrcu_init(&ukey->actions, NULL);
      ukey_set_actions(ukey, actions);
  
      ovs_mutex_init(&ukey->mutex);
      ukey->dump_seq = dump_seq;
      ukey->reval_seq = reval_seq;
      ukey->flow_exists = false;
      ukey->created = time_msec();
      memset(&ukey->stats, 0, sizeof ukey->stats);
      ukey->stats.used = used;
      ukey->xcache = NULL;
  
      ukey->key_recirc_id = key_recirc_id;
      recirc_refs_init(&ukey->recircs);
      if (xout) {
          /* Take ownership of the action recirc id references. */
          recirc_refs_swap(&ukey->recircs, &xout->recircs);
      }
  
      return ukey;
  }
  
  static struct udpif_key *
  ukey_create_from_upcall(struct upcall *upcall, struct flow_wildcards *wc)
  {
      struct odputil_keybuf keystub, maskstub;
      struct ofpbuf keybuf, maskbuf;
      bool megaflow;
      struct odp_flow_key_parms odp_parms = {
          .flow = upcall->flow,
          .mask = &wc->masks,
      };
  
      odp_parms.support = ofproto_dpif_get_support(upcall->ofproto)->odp;
      if (upcall->key_len) {
          ofpbuf_use_const(&keybuf, upcall->key, upcall->key_len);
      } else {
          /* dpif-netdev doesn't provide a netlink-formatted flow key in the
           * upcall, so convert the upcall's flow here. */
          ofpbuf_use_stack(&keybuf, &keystub, sizeof keystub);
          odp_parms.odp_in_port = upcall->flow->in_port.odp_port;
          odp_flow_key_from_flow(&odp_parms, &keybuf);
      }
  
      atomic_read_relaxed(&enable_megaflows, &megaflow);
      ofpbuf_use_stack(&maskbuf, &maskstub, sizeof maskstub);
      if (megaflow) {
          odp_parms.odp_in_port = ODPP_NONE;
          odp_parms.key_buf = &keybuf;
  
          odp_flow_key_from_mask(&odp_parms, &maskbuf);
      }
  
      return ukey_create__(keybuf.data, keybuf.size, maskbuf.data, maskbuf.size,
                           true, upcall->ufid, upcall->pmd_id,
                           &upcall->put_actions, upcall->dump_seq,
                           upcall->reval_seq, 0,
                           upcall->have_recirc_ref ? upcall->recirc->id : 0,
                           &upcall->xout);
  }
  
  static int
  ukey_create_from_dpif_flow(const struct udpif *udpif,
                             const struct dpif_flow *flow,
                             struct udpif_key **ukey)
  {
      struct dpif_flow full_flow;
      struct ofpbuf actions;
      uint64_t dump_seq, reval_seq;
      uint64_t stub[DPIF_FLOW_BUFSIZE / 8];
      const struct nlattr *a;
      unsigned int left;
  
      if (!flow->key_len || !flow->actions_len) {
          struct ofpbuf buf;
          int err;
  
          /* If the key or actions were not provided by the datapath, fetch the
           * full flow. */
          ofpbuf_use_stack(&buf, &stub, sizeof stub);
          err = dpif_flow_get(udpif->dpif, NULL, 0, &flow->ufid,
                              flow->pmd_id, &buf, &full_flow);
          if (err) {
              return err;
          }
          flow = &full_flow;
      }
  
      /* Check the flow actions for recirculation action.  As recirculation
       * relies on OVS userspace internal state, we need to delete all old
       * datapath flows with either a non-zero recirc_id in the key, or any
       * recirculation actions upon OVS restart. */
      NL_ATTR_FOR_EACH_UNSAFE (a, left, flow->key, flow->key_len) {
          if (nl_attr_type(a) == OVS_KEY_ATTR_RECIRC_ID
              && nl_attr_get_u32(a) != 0) {
              return EINVAL;
          }
      }
      NL_ATTR_FOR_EACH_UNSAFE (a, left, flow->actions, flow->actions_len) {
          if (nl_attr_type(a) == OVS_ACTION_ATTR_RECIRC) {
              return EINVAL;
          }
      }
  
      dump_seq = seq_read(udpif->dump_seq);
      reval_seq = seq_read(udpif->reval_seq);
      ofpbuf_use_const(&actions, &flow->actions, flow->actions_len);
      *ukey = ukey_create__(flow->key, flow->key_len,
                            flow->mask, flow->mask_len, flow->ufid_present,
                            &flow->ufid, flow->pmd_id, &actions, dump_seq,
                            reval_seq, flow->stats.used, 0, NULL);
  
      return 0;
  }
  
  /* Attempts to insert a ukey into the shared ukey maps.
   *
   * On success, returns true, installs the ukey and returns it in a locked
   * state. Otherwise, returns false. */
  static bool
  ukey_install_start(struct udpif *udpif, struct udpif_key *new_ukey)
      OVS_TRY_LOCK(true, new_ukey->mutex)
  {
      struct umap *umap;
      struct udpif_key *old_ukey;
      uint32_t idx;
      bool locked = false;
  
      idx = new_ukey->hash % N_UMAPS;
      umap = &udpif->ukeys[idx];
      ovs_mutex_lock(&umap->mutex);
      old_ukey = ukey_lookup(udpif, &new_ukey->ufid);
      if (old_ukey) {
          /* Uncommon case: A ukey is already installed with the same UFID. */
          if (old_ukey->key_len == new_ukey->key_len
              && !memcmp(old_ukey->key, new_ukey->key, new_ukey->key_len)) {
              COVERAGE_INC(handler_duplicate_upcall);
          } else {
              struct ds ds = DS_EMPTY_INITIALIZER;
  
              odp_format_ufid(&old_ukey->ufid, &ds);
              ds_put_cstr(&ds, " ");
              odp_flow_key_format(old_ukey->key, old_ukey->key_len, &ds);
              ds_put_cstr(&ds, "\n");
              odp_format_ufid(&new_ukey->ufid, &ds);
              ds_put_cstr(&ds, " ");
              odp_flow_key_format(new_ukey->key, new_ukey->key_len, &ds);
  
              VLOG_WARN_RL(&rl, "Conflicting ukey for flows:\n%s", ds_cstr(&ds));
              ds_destroy(&ds);
          }
      } else {
          ovs_mutex_lock(&new_ukey->mutex);
          cmap_insert(&umap->cmap, &new_ukey->cmap_node, new_ukey->hash);
          locked = true;
      }
      ovs_mutex_unlock(&umap->mutex);
  
      return locked;
  }
  
  static void
  ukey_install_finish__(struct udpif_key *ukey) OVS_REQUIRES(ukey->mutex)
  {
      ukey->flow_exists = true;
  }
  
  static bool
  ukey_install_finish(struct udpif_key *ukey, int error)
      OVS_RELEASES(ukey->mutex)
  {
      if (!error) {
          ukey_install_finish__(ukey);
      }
      ovs_mutex_unlock(&ukey->mutex);
  
      return !error;
  }
  
  static bool
  ukey_install(struct udpif *udpif, struct udpif_key *ukey)
  {
      /* The usual way to keep 'ukey->flow_exists' in sync with the datapath is
       * to call ukey_install_start(), install the corresponding datapath flow,
       * then call ukey_install_finish(). The netdev interface using upcall_cb()
       * doesn't provide a function to separately finish the flow installation,
       * so we perform the operations together here.
       *
       * This is fine currently, as revalidator threads will only delete this
       * ukey during revalidator_sweep() and only if the dump_seq is mismatched.
       * It is unlikely for a revalidator thread to advance dump_seq and reach
       * the next GC phase between ukey creation and flow installation. */
      return ukey_install_start(udpif, ukey) && ukey_install_finish(ukey, 0);
  }
  
  /* Searches for a ukey in 'udpif->ukeys' that matches 'flow' and attempts to
   * lock the ukey. If the ukey does not exist, create it.
   *
   * Returns 0 on success, setting *result to the matching ukey and returning it
   * in a locked state. Otherwise, returns an errno and clears *result. EBUSY
   * indicates that another thread is handling this flow. Other errors indicate
   * an unexpected condition creating a new ukey.
   *
   * *error is an output parameter provided to appease the threadsafety analyser,
   * and its value matches the return value. */
  static int
  ukey_acquire(struct udpif *udpif, const struct dpif_flow *flow,
               struct udpif_key **result, int *error)
      OVS_TRY_LOCK(0, (*result)->mutex)
  {
      struct udpif_key *ukey;
      int retval;
  
      ukey = ukey_lookup(udpif, &flow->ufid);
      if (ukey) {
          retval = ovs_mutex_trylock(&ukey->mutex);
      } else {
          /* Usually we try to avoid installing flows from revalidator threads,
           * because locking on a umap may cause handler threads to block.
           * However there are certain cases, like when ovs-vswitchd is
           * restarted, where it is desirable to handle flows that exist in the
           * datapath gracefully (ie, don't just clear the datapath). */
          bool install;
  
          retval = ukey_create_from_dpif_flow(udpif, flow, &ukey);
          if (retval) {
              goto done;
          }
          install = ukey_install_start(udpif, ukey);
          if (install) {
              ukey_install_finish__(ukey);
              retval = 0;
          } else {
              ukey_delete__(ukey);
              retval = EBUSY;
          }
      }
  
  done:
      *error = retval;
      if (retval) {
          *result = NULL;
      } else {
          *result = ukey;
      }
      return retval;
  }
  
  static void
  ukey_delete__(struct udpif_key *ukey)
      OVS_NO_THREAD_SAFETY_ANALYSIS
  {
      if (ukey) {
          if (ukey->key_recirc_id) {
              recirc_free_id(ukey->key_recirc_id);
          }
          recirc_refs_unref(&ukey->recircs);
          xlate_cache_delete(ukey->xcache);
          ofpbuf_delete(ovsrcu_get(struct ofpbuf *, &ukey->actions));
          ovs_mutex_destroy(&ukey->mutex);
          free(ukey);
      }
  }
  
  static void
  ukey_delete(struct umap *umap, struct udpif_key *ukey)
      OVS_REQUIRES(umap->mutex)
  {
      cmap_remove(&umap->cmap, &ukey->cmap_node, ukey->hash);
      ovsrcu_postpone(ukey_delete__, ukey);
  }
  
  static bool
  should_revalidate(const struct udpif *udpif, uint64_t packets,
                    long long int used)
  {
      long long int metric, now, duration;
  
      if (udpif->dump_duration < 200) {
          /* We are likely to handle full revalidation for the flows. */
          return true;
      }
  
      /* Calculate the mean time between seeing these packets. If this
       * exceeds the threshold, then delete the flow rather than performing
       * costly revalidation for flows that aren't being hit frequently.
       *
       * This is targeted at situations where the dump_duration is high (~1s),
       * and revalidation is triggered by a call to udpif_revalidate(). In
       * these situations, revalidation of all flows causes fluctuations in the
       * flow_limit due to the interaction with the dump_duration and max_idle.
       * This tends to result in deletion of low-throughput flows anyway, so
       * skip the revalidation and just delete those flows. */
      packets = MAX(packets, 1);
      now = MAX(used, time_msec());
      duration = now - used;
      metric = duration / packets;
  
      if (metric < 200) {
          /* The flow is receiving more than ~5pps, so keep it. */
          return true;
      }
      return false;
  }
  
  /* Verifies that the datapath actions of 'ukey' are still correct, and pushes
   * 'stats' for it.
   *
   * Returns a recommended action for 'ukey', options include:
   *      UKEY_DELETE The ukey should be deleted.
   *      UKEY_KEEP   The ukey is fine as is.
   *      UKEY_MODIFY The ukey's actions should be changed but is otherwise
   *                  fine.  Callers should change the actions to those found
   *                  in the caller supplied 'odp_actions' buffer.  The
   *                  recirculation references can be found in 'recircs' and
   *                  must be handled by the caller.
   *
   * If the result is UKEY_MODIFY, then references to all recirc_ids used by the
   * new flow will be held within 'recircs' (which may be none).
   *
   * The caller is responsible for both initializing 'recircs' prior this call,
   * and ensuring any references are eventually freed.
   */
  static enum reval_result
  revalidate_ukey(struct udpif *udpif, struct udpif_key *ukey,
                  const struct dpif_flow_stats *stats,
                  struct ofpbuf *odp_actions, uint64_t reval_seq,
                  struct recirc_refs *recircs)
      OVS_REQUIRES(ukey->mutex)
  {
      struct xlate_out xout, *xoutp;
      struct netflow *netflow;
      struct ofproto_dpif *ofproto;
      struct dpif_flow_stats push;
      struct flow flow;
      struct flow_wildcards dp_mask, wc;
      enum reval_result result;
      ofp_port_t ofp_in_port;
      struct xlate_in xin;
      long long int last_used;
      int error;
      bool need_revalidate;
  
      result = UKEY_DELETE;
      xoutp = NULL;
      netflow = NULL;
  
      ofpbuf_clear(odp_actions);
      need_revalidate = (ukey->reval_seq != reval_seq);
      last_used = ukey->stats.used;
      push.used = stats->used;
      push.tcp_flags = stats->tcp_flags;
      push.n_packets = (stats->n_packets > ukey->stats.n_packets
                        ? stats->n_packets - ukey->stats.n_packets
                        : 0);
      push.n_bytes = (stats->n_bytes > ukey->stats.n_bytes
                      ? stats->n_bytes - ukey->stats.n_bytes
                      : 0);
  
      if (need_revalidate && last_used
          && !should_revalidate(udpif, push.n_packets, last_used)) {
          goto exit;
      }
  
      /* We will push the stats, so update the ukey stats cache. */
      ukey->stats = *stats;
      if (!push.n_packets && !need_revalidate) {
          result = UKEY_KEEP;
          goto exit;
      }
  
      if (ukey->xcache && !need_revalidate) {
          xlate_push_stats(ukey->xcache, &push);
          result = UKEY_KEEP;
          goto exit;
      }
  
      if (odp_flow_key_to_flow(ukey->key, ukey->key_len, &flow)
          == ODP_FIT_ERROR) {
          goto exit;
      }
  
      error = xlate_lookup(udpif->backer, &flow, &ofproto, NULL, NULL, &netflow,
                           &ofp_in_port);
      if (error) {
          goto exit;
      }
  
      if (need_revalidate) {
          xlate_cache_clear(ukey->xcache);
      }
      if (!ukey->xcache) {
          ukey->xcache = xlate_cache_new();
      }
  
      xlate_in_init(&xin, ofproto, &flow, ofp_in_port, NULL, push.tcp_flags,
                    NULL, need_revalidate ? &wc : NULL, odp_actions);
      if (push.n_packets) {
          xin.resubmit_stats = &push;
          xin.may_learn = true;
      }
      xin.xcache = ukey->xcache;
      xlate_actions(&xin, &xout);
      xoutp = &xout;
  
      if (!need_revalidate) {
          result = UKEY_KEEP;
          goto exit;
      }
  
      if (xout.slow) {
          ofpbuf_clear(odp_actions);
          compose_slow_path(udpif, &xout, &flow, flow.in_port.odp_port,
                            odp_actions);
      }
  
      if (odp_flow_key_to_mask(ukey->mask, ukey->mask_len, ukey->key,
                               ukey->key_len, &dp_mask, &flow)
          == ODP_FIT_ERROR) {
          goto exit;
      }
  
      /* Do not modify if any bit is wildcarded by the installed datapath flow,
       * but not the newly revalidated wildcard mask (wc), i.e., if revalidation
       * tells that the datapath flow is now too generic and must be narrowed
       * down.  Note that we do not know if the datapath has ignored any of the
       * wildcarded bits, so we may be overtly conservative here. */
      if (flow_wildcards_has_extra(&dp_mask, &wc)) {
          goto exit;
      }
  
      if (!ofpbuf_equal(odp_actions,
                        ovsrcu_get(struct ofpbuf *, &ukey->actions))) {
          /* The datapath mask was OK, but the actions seem to have changed.
           * Let's modify it in place. */
          result = UKEY_MODIFY;
          /* Transfer recirc action ID references to the caller. */
          recirc_refs_swap(recircs, &xoutp->recircs);
          goto exit;
      }
  
      result = UKEY_KEEP;
  
  exit:
      if (result != UKEY_DELETE) {
          ukey->reval_seq = reval_seq;
      }
      if (netflow && result == UKEY_DELETE) {
          netflow_flow_clear(netflow, &flow);
      }
      xlate_out_uninit(xoutp);
      return result;
  }
  
  static void
  delete_op_init__(struct udpif *udpif, struct ukey_op *op,
                   const struct dpif_flow *flow)
  {
      op->ukey = NULL;
      op->dop.type = DPIF_OP_FLOW_DEL;
      op->dop.u.flow_del.key = flow->key;
      op->dop.u.flow_del.key_len = flow->key_len;
      op->dop.u.flow_del.ufid = flow->ufid_present ? &flow->ufid : NULL;
      op->dop.u.flow_del.pmd_id = flow->pmd_id;
      op->dop.u.flow_del.stats = &op->stats;
      op->dop.u.flow_del.terse = udpif_use_ufid(udpif);
  }
  
  static void
  delete_op_init(struct udpif *udpif, struct ukey_op *op, struct udpif_key *ukey)
  {
      op->ukey = ukey;
      op->dop.type = DPIF_OP_FLOW_DEL;
      op->dop.u.flow_del.key = ukey->key;
      op->dop.u.flow_del.key_len = ukey->key_len;
      op->dop.u.flow_del.ufid = ukey->ufid_present ? &ukey->ufid : NULL;
      op->dop.u.flow_del.pmd_id = ukey->pmd_id;
      op->dop.u.flow_del.stats = &op->stats;
      op->dop.u.flow_del.terse = udpif_use_ufid(udpif);
  }
  
  static void
  modify_op_init(struct ukey_op *op, struct udpif_key *ukey)
  {
      op->ukey = ukey;
      op->dop.type = DPIF_OP_FLOW_PUT;
      op->dop.u.flow_put.flags = DPIF_FP_MODIFY;
      op->dop.u.flow_put.key = ukey->key;
      op->dop.u.flow_put.key_len = ukey->key_len;
      op->dop.u.flow_put.mask = ukey->mask;
      op->dop.u.flow_put.mask_len = ukey->mask_len;
      op->dop.u.flow_put.ufid = &ukey->ufid;
      op->dop.u.flow_put.pmd_id = ukey->pmd_id;
      op->dop.u.flow_put.stats = NULL;
      ukey_get_actions(ukey, &op->dop.u.flow_put.actions,
                       &op->dop.u.flow_put.actions_len);
  }
  
  static void
  push_ukey_ops__(struct udpif *udpif, struct ukey_op *ops, size_t n_ops)
  {
      struct dpif_op *opsp[REVALIDATE_MAX_BATCH];
      size_t i;
  
      ovs_assert(n_ops <= REVALIDATE_MAX_BATCH);
      for (i = 0; i < n_ops; i++) {
          opsp[i] = &ops[i].dop;
      }
      dpif_operate(udpif->dpif, opsp, n_ops);
  
      for (i = 0; i < n_ops; i++) {
          struct ukey_op *op = &ops[i];
          struct dpif_flow_stats *push, *stats, push_buf;
  
          stats = op->dop.u.flow_del.stats;
          push = &push_buf;
  
          if (op->dop.type != DPIF_OP_FLOW_DEL) {
              /* Only deleted flows need their stats pushed. */
              continue;
          }
  
          if (op->dop.error) {
              /* flow_del error, 'stats' is unusable. */
              continue;
          }
  
          if (op->ukey) {
              ovs_mutex_lock(&op->ukey->mutex);
              push->used = MAX(stats->used, op->ukey->stats.used);
              push->tcp_flags = stats->tcp_flags | op->ukey->stats.tcp_flags;
              push->n_packets = stats->n_packets - op->ukey->stats.n_packets;
              push->n_bytes = stats->n_bytes - op->ukey->stats.n_bytes;
              ovs_mutex_unlock(&op->ukey->mutex);
          } else {
              push = stats;
          }
  
          if (push->n_packets || netflow_exists()) {
              const struct nlattr *key = op->dop.u.flow_del.key;
              size_t key_len = op->dop.u.flow_del.key_len;
              struct ofproto_dpif *ofproto;
              struct netflow *netflow;
              ofp_port_t ofp_in_port;
              struct flow flow;
              int error;
  
              if (op->ukey) {
                  ovs_mutex_lock(&op->ukey->mutex);
                  if (op->ukey->xcache) {
                      xlate_push_stats(op->ukey->xcache, push);
                      ovs_mutex_unlock(&op->ukey->mutex);
                      continue;
                  }
                  ovs_mutex_unlock(&op->ukey->mutex);
                  key = op->ukey->key;
                  key_len = op->ukey->key_len;
              }
  
              if (odp_flow_key_to_flow(key, key_len, &flow)
                  == ODP_FIT_ERROR) {
                  continue;
              }
  
              error = xlate_lookup(udpif->backer, &flow, &ofproto, NULL, NULL,
                                   &netflow, &ofp_in_port);
              if (!error) {
                  struct xlate_in xin;
  
                  xlate_in_init(&xin, ofproto, &flow, ofp_in_port, NULL,
                                push->tcp_flags, NULL, NULL, NULL);
                  xin.resubmit_stats = push->n_packets ? push : NULL;
                  xin.may_learn = push->n_packets > 0;
                  xlate_actions_for_side_effects(&xin);
  
                  if (netflow) {
                      netflow_flow_clear(netflow, &flow);
                  }
              }
          }
      }
  }
  
  static void
  push_ukey_ops(struct udpif *udpif, struct umap *umap,
                struct ukey_op *ops, size_t n_ops)
  {
      int i;
  
      push_ukey_ops__(udpif, ops, n_ops);
      ovs_mutex_lock(&umap->mutex);
      for (i = 0; i < n_ops; i++) {
          ukey_delete(umap, ops[i].ukey);
      }
      ovs_mutex_unlock(&umap->mutex);
  }
  
  static void
  log_unexpected_flow(const struct dpif_flow *flow, int error)
  {
      static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(10, 60);
      struct ds ds = DS_EMPTY_INITIALIZER;
  
      ds_put_format(&ds, "Failed to acquire udpif_key corresponding to "
                    "unexpected flow (%s): ", ovs_strerror(error));
      odp_format_ufid(&flow->ufid, &ds);
      VLOG_WARN_RL(&rl, "%s", ds_cstr(&ds));
  }
  
  static void
  reval_op_init(struct ukey_op *op, enum reval_result result,
                struct udpif *udpif, struct udpif_key *ukey,
                struct recirc_refs *recircs, struct ofpbuf *odp_actions)
  {
      if (result == UKEY_DELETE) {
          delete_op_init(udpif, op, ukey);
      } else if (result == UKEY_MODIFY) {
          /* Store the new recircs. */
          recirc_refs_swap(&ukey->recircs, recircs);
          /* Release old recircs. */
          recirc_refs_unref(recircs);
          /* ukey->key_recirc_id remains, as the key is the same as before. */
  
          ukey_set_actions(ukey, odp_actions);
          modify_op_init(op, ukey);
      }
  }
  
  static void
  revalidate(struct revalidator *revalidator)
  {
      uint64_t odp_actions_stub[1024 / 8];
      struct ofpbuf odp_actions = OFPBUF_STUB_INITIALIZER(odp_actions_stub);
  
      struct udpif *udpif = revalidator->udpif;
      struct dpif_flow_dump_thread *dump_thread;
      uint64_t dump_seq, reval_seq;
      unsigned int flow_limit;
  
      dump_seq = seq_read(udpif->dump_seq);
      reval_seq = seq_read(udpif->reval_seq);
      atomic_read_relaxed(&udpif->flow_limit, &flow_limit);
      dump_thread = dpif_flow_dump_thread_create(udpif->dump);
      for (;;) {
          struct ukey_op ops[REVALIDATE_MAX_BATCH];
          int n_ops = 0;
  
          struct dpif_flow flows[REVALIDATE_MAX_BATCH];
          const struct dpif_flow *f;
          int n_dumped;
  
          long long int max_idle;
          long long int now;
          size_t n_dp_flows;
          bool kill_them_all;
  
          n_dumped = dpif_flow_dump_next(dump_thread, flows, ARRAY_SIZE(flows));
          if (!n_dumped) {
              break;
          }
  
          now = time_msec();
  
          /* In normal operation we want to keep flows around until they have
           * been idle for 'ofproto_max_idle' milliseconds.  However:
           *
           *     - If the number of datapath flows climbs above 'flow_limit',
           *       drop that down to 100 ms to try to bring the flows down to
           *       the limit.
           *
           *     - If the number of datapath flows climbs above twice
           *       'flow_limit', delete all the datapath flows as an emergency
           *       measure.  (We reassess this condition for the next batch of
           *       datapath flows, so we will recover before all the flows are
           *       gone.) */
          n_dp_flows = udpif_get_n_flows(udpif);
          kill_them_all = n_dp_flows > flow_limit * 2;
          max_idle = n_dp_flows > flow_limit ? 100 : ofproto_max_idle;
  
          for (f = flows; f < &flows[n_dumped]; f++) {
              long long int used = f->stats.used;
              struct recirc_refs recircs = RECIRC_REFS_EMPTY_INITIALIZER;
              enum reval_result result;
              struct udpif_key *ukey;
              bool already_dumped;
              int error;
  
              if (ukey_acquire(udpif, f, &ukey, &error)) {
                  if (error == EBUSY) {
                      /* Another thread is processing this flow, so don't bother
                       * processing it.*/
                      COVERAGE_INC(upcall_ukey_contention);
                  } else {
                      log_unexpected_flow(f, error);
                      if (error != ENOENT) {
                          delete_op_init__(udpif, &ops[n_ops++], f);
                      }
                  }
                  continue;
              }
  
              already_dumped = ukey->dump_seq == dump_seq;
              if (already_dumped) {
                  /* The flow has already been handled during this flow dump
                   * operation. Skip it. */
                  if (ukey->xcache) {
                      COVERAGE_INC(dumped_duplicate_flow);
                  } else {
                      COVERAGE_INC(dumped_new_flow);
                  }
                  ovs_mutex_unlock(&ukey->mutex);
                  continue;
              }
  
              if (!used) {
                  used = ukey->created;
              }
              if (kill_them_all || (used && used < now - max_idle)) {
                  result = UKEY_DELETE;
              } else {
                  result = revalidate_ukey(udpif, ukey, &f->stats, &odp_actions,
                                           reval_seq, &recircs);
              }
              ukey->dump_seq = dump_seq;
              ukey->flow_exists = result != UKEY_DELETE;
  
              if (result != UKEY_KEEP) {
                  /* Takes ownership of 'recircs'. */
                  reval_op_init(&ops[n_ops++], result, udpif, ukey, &recircs,
                                &odp_actions);
              }
              ovs_mutex_unlock(&ukey->mutex);
          }
  
          if (n_ops) {
              push_ukey_ops__(udpif, ops, n_ops);
          }
          ovsrcu_quiesce();
      }
      dpif_flow_dump_thread_destroy(dump_thread);
      ofpbuf_uninit(&odp_actions);
  }
  
  /* Pauses the 'revalidator', can only proceed after main thread
   * calls udpif_resume_revalidators(). */
  static void
  revalidator_pause(struct revalidator *revalidator)
  {
      /* The first block is for sync'ing the pause with main thread. */
      ovs_barrier_block(&revalidator->udpif->pause_barrier);
      /* The second block is for pausing until main thread resumes. */
      ovs_barrier_block(&revalidator->udpif->pause_barrier);
  }
  
  static void
  revalidator_sweep__(struct revalidator *revalidator, bool purge)
  {
      struct udpif *udpif;
      uint64_t dump_seq, reval_seq;
      int slice;
  
      udpif = revalidator->udpif;
      dump_seq = seq_read(udpif->dump_seq);
      reval_seq = seq_read(udpif->reval_seq);
      slice = revalidator - udpif->revalidators;
      ovs_assert(slice < udpif->n_revalidators);
  
      for (int i = slice; i < N_UMAPS; i += udpif->n_revalidators) {
          uint64_t odp_actions_stub[1024 / 8];
          struct ofpbuf odp_actions = OFPBUF_STUB_INITIALIZER(odp_actions_stub);
  
          struct ukey_op ops[REVALIDATE_MAX_BATCH];
          struct udpif_key *ukey;
          struct umap *umap = &udpif->ukeys[i];
          size_t n_ops = 0;
  
          CMAP_FOR_EACH(ukey, cmap_node, &umap->cmap) {
              bool flow_exists, seq_mismatch;
              struct recirc_refs recircs = RECIRC_REFS_EMPTY_INITIALIZER;
              enum reval_result result;
  
              /* Handler threads could be holding a ukey lock while it installs a
               * new flow, so don't hang around waiting for access to it. */
              if (ovs_mutex_trylock(&ukey->mutex)) {
                  continue;
              }
              flow_exists = ukey->flow_exists;
              seq_mismatch = (ukey->dump_seq != dump_seq
                              && ukey->reval_seq != reval_seq);
  
              if (purge) {
                  result = UKEY_DELETE;
              } else if (!seq_mismatch) {
                  result = UKEY_KEEP;
              } else {
                  struct dpif_flow_stats stats;
                  COVERAGE_INC(revalidate_missed_dp_flow);
                  memset(&stats, 0, sizeof stats);
                  result = revalidate_ukey(udpif, ukey, &stats, &odp_actions,
                                           reval_seq, &recircs);
              }
              if (result != UKEY_KEEP) {
                  /* Takes ownership of 'recircs'. */
                  reval_op_init(&ops[n_ops++], result, udpif, ukey, &recircs,
                                &odp_actions);
              }
              ovs_mutex_unlock(&ukey->mutex);
  
              if (n_ops == REVALIDATE_MAX_BATCH) {
                  push_ukey_ops(udpif, umap, ops, n_ops);
                  n_ops = 0;
              }
  
              if (!flow_exists) {
                  ovs_mutex_lock(&umap->mutex);
                  ukey_delete(umap, ukey);
                  ovs_mutex_unlock(&umap->mutex);
              }
          }
  
          if (n_ops) {
              push_ukey_ops(udpif, umap, ops, n_ops);
          }
  
          ofpbuf_uninit(&odp_actions);
          ovsrcu_quiesce();
      }
  }
  
  static void
  revalidator_sweep(struct revalidator *revalidator)
  {
      revalidator_sweep__(revalidator, false);
  }
  
  static void
  revalidator_purge(struct revalidator *revalidator)
  {
      revalidator_sweep__(revalidator, true);
  }
  
  /* In reaction to dpif purge, purges all 'ukey's with same 'pmd_id'. */
  static void
  dp_purge_cb(void *aux, unsigned pmd_id)
  {
      struct udpif *udpif = aux;
      size_t i;
  
      udpif_pause_revalidators(udpif);
      for (i = 0; i < N_UMAPS; i++) {
          struct ukey_op ops[REVALIDATE_MAX_BATCH];
          struct udpif_key *ukey;
          struct umap *umap = &udpif->ukeys[i];
          size_t n_ops = 0;
  
          CMAP_FOR_EACH(ukey, cmap_node, &umap->cmap) {
               if (ukey->pmd_id == pmd_id) {
                  delete_op_init(udpif, &ops[n_ops++], ukey);
                  if (n_ops == REVALIDATE_MAX_BATCH) {
                      push_ukey_ops(udpif, umap, ops, n_ops);
                      n_ops = 0;
                  }
              }
          }
  
          if (n_ops) {
              push_ukey_ops(udpif, umap, ops, n_ops);
          }
  
          ovsrcu_quiesce();
      }
      udpif_resume_revalidators(udpif);
  }
  
  static void
  upcall_unixctl_show(struct unixctl_conn *conn, int argc OVS_UNUSED,
                      const char *argv[] OVS_UNUSED, void *aux OVS_UNUSED)
  {
      struct ds ds = DS_EMPTY_INITIALIZER;
      struct udpif *udpif;
  
      LIST_FOR_EACH (udpif, list_node, &all_udpifs) {
          unsigned int flow_limit;
          bool ufid_enabled;
          size_t i;
  
          atomic_read_relaxed(&udpif->flow_limit, &flow_limit);
          ufid_enabled = udpif_use_ufid(udpif);
  
          ds_put_format(&ds, "%s:\n", dpif_name(udpif->dpif));
          ds_put_format(&ds, "\tflows         : (current %lu)"
              " (avg %u) (max %u) (limit %u)\n", udpif_get_n_flows(udpif),
              udpif->avg_n_flows, udpif->max_n_flows, flow_limit);
          ds_put_format(&ds, "\tdump duration : %lldms\n", udpif->dump_duration);
          ds_put_format(&ds, "\tufid enabled : ");
          if (ufid_enabled) {
              ds_put_format(&ds, "true\n");
          } else {
              ds_put_format(&ds, "false\n");
          }
          ds_put_char(&ds, '\n');
  
          for (i = 0; i < n_revalidators; i++) {
              struct revalidator *revalidator = &udpif->revalidators[i];
              int j, elements = 0;
  
              for (j = i; j < N_UMAPS; j += n_revalidators) {
                  elements += cmap_count(&udpif->ukeys[j].cmap);
              }
              ds_put_format(&ds, "\t%u: (keys %d)\n", revalidator->id, elements);
          }
      }
  
      unixctl_command_reply(conn, ds_cstr(&ds));
      ds_destroy(&ds);
  }
  
  /* Disable using the megaflows.
   *
   * This command is only needed for advanced debugging, so it's not
   * documented in the man page. */
  static void
  upcall_unixctl_disable_megaflows(struct unixctl_conn *conn,
                                   int argc OVS_UNUSED,
                                   const char *argv[] OVS_UNUSED,
                                   void *aux OVS_UNUSED)
  {
      atomic_store_relaxed(&enable_megaflows, false);
      udpif_flush_all_datapaths();
      unixctl_command_reply(conn, "megaflows disabled");
  }
  
  /* Re-enable using megaflows.
   *
   * This command is only needed for advanced debugging, so it's not
   * documented in the man page. */
  static void
  upcall_unixctl_enable_megaflows(struct unixctl_conn *conn,
                                  int argc OVS_UNUSED,
                                  const char *argv[] OVS_UNUSED,
                                  void *aux OVS_UNUSED)
  {
      atomic_store_relaxed(&enable_megaflows, true);
      udpif_flush_all_datapaths();
      unixctl_command_reply(conn, "megaflows enabled");
  }
  
  /* Disable skipping flow attributes during flow dump.
   *
   * This command is only needed for advanced debugging, so it's not
   * documented in the man page. */
  static void
  upcall_unixctl_disable_ufid(struct unixctl_conn *conn, int argc OVS_UNUSED,
                             const char *argv[] OVS_UNUSED, void *aux OVS_UNUSED)
  {
      atomic_store_relaxed(&enable_ufid, false);
      unixctl_command_reply(conn, "Datapath dumping tersely using UFID disabled");
  }
  
  /* Re-enable skipping flow attributes during flow dump.
   *
   * This command is only needed for advanced debugging, so it's not documented
   * in the man page. */
  static void
  upcall_unixctl_enable_ufid(struct unixctl_conn *conn, int argc OVS_UNUSED,
                            const char *argv[] OVS_UNUSED, void *aux OVS_UNUSED)
  {
      atomic_store_relaxed(&enable_ufid, true);
      unixctl_command_reply(conn, "Datapath dumping tersely using UFID enabled "
                                  "for supported datapaths");
  }
  
  /* Set the flow limit.
   *
   * This command is only needed for advanced debugging, so it's not
   * documented in the man page. */
  static void
  upcall_unixctl_set_flow_limit(struct unixctl_conn *conn,
                                int argc OVS_UNUSED,
                                const char *argv[] OVS_UNUSED,
                                void *aux OVS_UNUSED)
  {
      struct ds ds = DS_EMPTY_INITIALIZER;
      struct udpif *udpif;
      unsigned int flow_limit = atoi(argv[1]);
  
      LIST_FOR_EACH (udpif, list_node, &all_udpifs) {
          atomic_store_relaxed(&udpif->flow_limit, flow_limit);
      }
      ds_put_format(&ds, "set flow_limit to %u\n", flow_limit);
      unixctl_command_reply(conn, ds_cstr(&ds));
      ds_destroy(&ds);
  }
  
  static void
  upcall_unixctl_dump_wait(struct unixctl_conn *conn,
                           int argc OVS_UNUSED,
                           const char *argv[] OVS_UNUSED,
                           void *aux OVS_UNUSED)
  {
      if (list_is_singleton(&all_udpifs)) {
          struct udpif *udpif = NULL;
          size_t len;
  
          udpif = OBJECT_CONTAINING(list_front(&all_udpifs), udpif, list_node);
          len = (udpif->n_conns + 1) * sizeof *udpif->conns;
          udpif->conn_seq = seq_read(udpif->dump_seq);
          udpif->conns = xrealloc(udpif->conns, len);
          udpif->conns[udpif->n_conns++] = conn;
      } else {
          unixctl_command_reply_error(conn, "can't wait on multiple udpifs.");
      }
  }
  
  static void
  upcall_unixctl_purge(struct unixctl_conn *conn, int argc OVS_UNUSED,
                       const char *argv[] OVS_UNUSED, void *aux OVS_UNUSED)
  {
      struct udpif *udpif;
  
      LIST_FOR_EACH (udpif, list_node, &all_udpifs) {
          int n;
  
          for (n = 0; n < udpif->n_revalidators; n++) {
              revalidator_purge(&udpif->revalidators[n]);
          }
      }
      unixctl_command_reply(conn, "");
  }
  