text: /* Copyright (c) 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 "bfd.h"
  
  #include <sys/types.h>
  #include <arpa/inet.h>
  #include <netinet/in_systm.h>
  #include <netinet/ip.h>
  #include <sys/socket.h>
  
  #include "byte-order.h"
  #include "connectivity.h"
  #include "csum.h"
  #include "dp-packet.h"
  #include "dpif.h"
  #include "dynamic-string.h"
  #include "flow.h"
  #include "hash.h"
  #include "hmap.h"
  #include "list.h"
  #include "netdev.h"
  #include "odp-util.h"
  #include "ofpbuf.h"
  #include "ovs-thread.h"
  #include "openvswitch/types.h"
  #include "packets.h"
  #include "poll-loop.h"
  #include "random.h"
  #include "seq.h"
  #include "smap.h"
  #include "timeval.h"
  #include "unaligned.h"
  #include "unixctl.h"
  #include "util.h"
  #include "openvswitch/vlog.h"
  
  VLOG_DEFINE_THIS_MODULE(bfd);
  
  /* XXX Finish BFD.
   *
   * The goal of this module is to replace CFM with something both more flexible
   * and standards compliant.  In service of this goal, the following needs to be
   * done.
   *
   * - Compliance
   *   * Implement Demand mode.
   *   * Go through the RFC line by line and verify we comply.
   *   * Test against a hardware implementation.  Preferably a popular one.
   *   * Delete BFD packets with nw_ttl != 255 in the datapath to prevent DOS
   *     attacks.
   *
   * - Unit tests.
   *
   * - Set TOS/PCP on the outer tunnel header when encapped.
   *
   * - Sending BFD messages should be in its own thread/process.
   *
   * - Scale testing.  How does it operate when there are large number of bfd
   *   sessions?  Do we ever have random flaps?  What's the CPU utilization?
   *
   * - Rely on data traffic for liveness by using BFD demand mode.
   *   If we're receiving traffic on a port, we can safely assume it's up (modulo
   *   unidrectional failures).  BFD has a demand mode in which it can stay quiet
   *   unless it feels the need to check the status of the port.  Using this, we
   *   can implement a strategy in which BFD only sends control messages on dark
   *   interfaces.
   *
   * - Depending on how one interprets the spec, it appears that a BFD session
   *   can never change bfd.LocalDiag to "No Diagnostic".  We should verify that
   *   this is what hardware implementations actually do.  Seems like "No
   *   Diagnostic" should be set once a BFD session state goes UP. */
  
  #define BFD_VERSION 1
  
  enum flags {
      FLAG_MULTIPOINT = 1 << 0,
      FLAG_DEMAND = 1 << 1,
      FLAG_AUTH = 1 << 2,
      FLAG_CTL = 1 << 3,
      FLAG_FINAL = 1 << 4,
      FLAG_POLL = 1 << 5
  };
  
  enum state {
      STATE_ADMIN_DOWN = 0 << 6,
      STATE_DOWN = 1 << 6,
      STATE_INIT = 2 << 6,
      STATE_UP = 3 << 6
  };
  
  enum diag {
      DIAG_NONE = 0,                /* No Diagnostic. */
      DIAG_EXPIRED = 1,             /* Control Detection Time Expired. */
      DIAG_ECHO_FAILED = 2,         /* Echo Function Failed. */
      DIAG_RMT_DOWN = 3,            /* Neighbor Signaled Session Down. */
      DIAG_FWD_RESET = 4,           /* Forwarding Plane Reset. */
      DIAG_PATH_DOWN = 5,           /* Path Down. */
      DIAG_CPATH_DOWN = 6,          /* Concatenated Path Down. */
      DIAG_ADMIN_DOWN = 7,          /* Administratively Down. */
      DIAG_RCPATH_DOWN = 8          /* Reverse Concatenated Path Down. */
  };
  
  /* RFC 5880 Section 4.1
   *  0                   1                   2                   3
   *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |Vers |  Diag   |Sta|P|F|C|A|D|M|  Detect Mult  |    Length     |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                       My Discriminator                        |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                      Your Discriminator                       |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                    Desired Min TX Interval                    |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                   Required Min RX Interval                    |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                 Required Min Echo RX Interval                 |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ */
  struct msg {
      uint8_t vers_diag;    /* Version and diagnostic. */
      uint8_t flags;        /* 2bit State field followed by flags. */
      uint8_t mult;         /* Fault detection multiplier. */
      uint8_t length;       /* Length of this BFD message. */
      ovs_be32 my_disc;     /* My discriminator. */
      ovs_be32 your_disc;   /* Your discriminator. */
      ovs_be32 min_tx;      /* Desired minimum tx interval. */
      ovs_be32 min_rx;      /* Required minimum rx interval. */
      ovs_be32 min_rx_echo; /* Required minimum echo rx interval. */
  };
  BUILD_ASSERT_DECL(BFD_PACKET_LEN == sizeof(struct msg));
  
  #define DIAG_MASK 0x1f
  #define VERS_SHIFT 5
  #define STATE_MASK 0xC0
  #define FLAGS_MASK 0x3f
  
  struct bfd {
      struct hmap_node node;        /* In 'all_bfds'. */
      uint32_t disc;                /* bfd.LocalDiscr. Key in 'all_bfds' hmap. */
  
      char *name;                   /* Name used for logging. */
  
      bool cpath_down;              /* Concatenated Path Down. */
      uint8_t mult;                 /* bfd.DetectMult. */
  
      struct netdev *netdev;
      uint64_t rx_packets;          /* Packets received by 'netdev'. */
  
      enum state state;             /* bfd.SessionState. */
      enum state rmt_state;         /* bfd.RemoteSessionState. */
  
      enum diag diag;               /* bfd.LocalDiag. */
      enum diag rmt_diag;           /* Remote diagnostic. */
  
      enum flags flags;             /* Flags sent on messages. */
      enum flags rmt_flags;         /* Flags last received. */
  
      uint32_t rmt_disc;            /* bfd.RemoteDiscr. */
  
      struct eth_addr local_eth_src; /* Local eth src address. */
      struct eth_addr local_eth_dst; /* Local eth dst address. */
  
      struct eth_addr rmt_eth_dst;   /* Remote eth dst address. */
  
      ovs_be32 ip_src;              /* IPv4 source address. */
      ovs_be32 ip_dst;              /* IPv4 destination address. */
  
      uint16_t udp_src;             /* UDP source port. */
  
      /* All timers in milliseconds. */
      long long int rmt_min_rx;     /* bfd.RemoteMinRxInterval. */
      long long int rmt_min_tx;     /* Remote minimum TX interval. */
  
      long long int cfg_min_tx;     /* Configured minimum TX rate. */
      long long int cfg_min_rx;     /* Configured required minimum RX rate. */
      long long int poll_min_tx;    /* Min TX negotating in a poll sequence. */
      long long int poll_min_rx;    /* Min RX negotating in a poll sequence. */
      long long int min_tx;         /* bfd.DesiredMinTxInterval. */
      long long int min_rx;         /* bfd.RequiredMinRxInterval. */
  
      long long int last_tx;        /* Last TX time. */
      long long int next_tx;        /* Next TX time. */
      long long int detect_time;    /* RFC 5880 6.8.4 Detection time. */
  
      bool last_forwarding;         /* Last calculation of forwarding flag. */
      int forwarding_override;      /* Manual override of 'forwarding' status. */
  
      atomic_bool check_tnl_key;    /* Verify tunnel key of inbound packets? */
      struct ovs_refcount ref_cnt;
  
      /* When forward_if_rx is true, bfd_forwarding() will return
       * true as long as there are incoming packets received.
       * Note, forwarding_override still has higher priority. */
      bool forwarding_if_rx;
      long long int forwarding_if_rx_detect_time;
  
      /* When 'bfd->forwarding_if_rx' is set, at least one bfd control packet
       * is required to be received every 100 * bfd->cfg_min_rx.  If bfd
       * control packet is not received within this interval, even if data
       * packets are received, the bfd->forwarding will still be false. */
      long long int demand_rx_bfd_time;
  
      /* BFD decay related variables. */
      bool in_decay;                /* True when bfd is in decay. */
      int decay_min_rx;             /* min_rx is set to decay_min_rx when */
                                    /* in decay. */
      int decay_rx_ctl;             /* Count bfd packets received within decay */
                                    /* detect interval. */
      uint64_t decay_rx_packets;    /* Packets received by 'netdev'. */
      long long int decay_detect_time; /* Decay detection time. */
  
      uint64_t flap_count;          /* Counts bfd forwarding flaps. */
  
      /* True when the variables returned by bfd_get_status() are changed
       * since last check. */
      bool status_changed;
  };
  
  static struct ovs_mutex mutex = OVS_MUTEX_INITIALIZER;
  static struct hmap all_bfds__ = HMAP_INITIALIZER(&all_bfds__);
  static struct hmap *const all_bfds OVS_GUARDED_BY(mutex) = &all_bfds__;
  
  static bool bfd_lookup_ip(const char *host_name, struct in_addr *)
      OVS_REQUIRES(mutex);
  static bool bfd_forwarding__(struct bfd *) OVS_REQUIRES(mutex);
  static bool bfd_in_poll(const struct bfd *) OVS_REQUIRES(mutex);
  static void bfd_poll(struct bfd *bfd) OVS_REQUIRES(mutex);
  static const char *bfd_diag_str(enum diag) OVS_REQUIRES(mutex);
  static const char *bfd_state_str(enum state) OVS_REQUIRES(mutex);
  static long long int bfd_min_tx(const struct bfd *) OVS_REQUIRES(mutex);
  static long long int bfd_tx_interval(const struct bfd *)
      OVS_REQUIRES(mutex);
  static long long int bfd_rx_interval(const struct bfd *)
      OVS_REQUIRES(mutex);
  static void bfd_set_next_tx(struct bfd *) OVS_REQUIRES(mutex);
  static void bfd_set_state(struct bfd *, enum state, enum diag)
      OVS_REQUIRES(mutex);
  static uint32_t generate_discriminator(void) OVS_REQUIRES(mutex);
  static void bfd_put_details(struct ds *, const struct bfd *)
      OVS_REQUIRES(mutex);
  static uint64_t bfd_rx_packets(const struct bfd *) OVS_REQUIRES(mutex);
  static void bfd_try_decay(struct bfd *) OVS_REQUIRES(mutex);
  static void bfd_decay_update(struct bfd *) OVS_REQUIRES(mutex);
  static void bfd_status_changed(struct bfd *) OVS_REQUIRES(mutex);
  
  static void bfd_forwarding_if_rx_update(struct bfd *) OVS_REQUIRES(mutex);
  static void bfd_unixctl_show(struct unixctl_conn *, int argc,
                               const char *argv[], void *aux OVS_UNUSED);
  static void bfd_unixctl_set_forwarding_override(struct unixctl_conn *,
                                                  int argc, const char *argv[],
                                                  void *aux OVS_UNUSED);
  static void log_msg(enum vlog_level, const struct msg *, const char *message,
                      const struct bfd *) OVS_REQUIRES(mutex);
  
  static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(20, 20);
  
  /* Returns true if the interface on which 'bfd' is running may be used to
   * forward traffic according to the BFD session state. */
  bool
  bfd_forwarding(struct bfd *bfd) OVS_EXCLUDED(mutex)
  {
      bool ret;
  
      ovs_mutex_lock(&mutex);
      ret = bfd_forwarding__(bfd);
      ovs_mutex_unlock(&mutex);
      return ret;
  }
  
  /* When forwarding_if_rx is enabled, if there are packets received,
   * updates forwarding_if_rx_detect_time. */
  void
  bfd_account_rx(struct bfd *bfd, const struct dpif_flow_stats *stats)
  {
      if (stats->n_packets && bfd->forwarding_if_rx) {
          ovs_mutex_lock(&mutex);
          bfd_forwarding__(bfd);
          bfd_forwarding_if_rx_update(bfd);
          bfd_forwarding__(bfd);
          ovs_mutex_unlock(&mutex);
      }
  }
  
  /* Returns and resets the 'bfd->status_changed'. */
  bool
  bfd_check_status_change(struct bfd *bfd) OVS_EXCLUDED(mutex)
  {
      bool ret;
  
      ovs_mutex_lock(&mutex);
      ret = bfd->status_changed;
      bfd->status_changed = false;
      ovs_mutex_unlock(&mutex);
  
      return ret;
  }
  
  /* Returns a 'smap' of key value pairs representing the status of 'bfd'
   * intended for the OVS database. */
  void
  bfd_get_status(const struct bfd *bfd, struct smap *smap)
      OVS_EXCLUDED(mutex)
  {
      ovs_mutex_lock(&mutex);
      smap_add(smap, "forwarding",
               bfd_forwarding__(CONST_CAST(struct bfd *, bfd))
               ? "true" : "false");
      smap_add(smap, "state", bfd_state_str(bfd->state));
      smap_add(smap, "diagnostic", bfd_diag_str(bfd->diag));
      smap_add_format(smap, "flap_count", "%"PRIu64, bfd->flap_count);
      smap_add(smap, "remote_state", bfd_state_str(bfd->rmt_state));
      smap_add(smap, "remote_diagnostic", bfd_diag_str(bfd->rmt_diag));
      ovs_mutex_unlock(&mutex);
  }
  
  void
  bfd_init(void)
  {
      unixctl_command_register("bfd/show", "[interface]", 0, 1,
                               bfd_unixctl_show, NULL);
      unixctl_command_register("bfd/set-forwarding",
                               "[interface] normal|false|true", 1, 2,
                               bfd_unixctl_set_forwarding_override, NULL);
  }
  
  /* Initializes, destroys, or reconfigures the BFD session 'bfd' (named 'name'),
   * according to the database configuration contained in 'cfg'.  Takes ownership
   * of 'bfd', which may be NULL.  Returns a BFD object which may be used as a
   * handle for the session, or NULL if BFD is not enabled according to 'cfg'.
   * Also returns NULL if cfg is NULL. */
  struct bfd *
  bfd_configure(struct bfd *bfd, const char *name, const struct smap *cfg,
                struct netdev *netdev) OVS_EXCLUDED(mutex)
  {
      static atomic_count udp_src = ATOMIC_COUNT_INIT(0);
  
      int decay_min_rx;
      long long int min_tx, min_rx;
      bool need_poll = false;
      bool cfg_min_rx_changed = false;
      bool cpath_down, forwarding_if_rx;
      const char *hwaddr, *ip_src, *ip_dst;
      struct in_addr in_addr;
      struct eth_addr ea;
  
      if (!cfg || !smap_get_bool(cfg, "enable", false)) {
          bfd_unref(bfd);
          return NULL;
      }
  
      ovs_mutex_lock(&mutex);
      if (!bfd) {
          bfd = xzalloc(sizeof *bfd);
          bfd->name = xstrdup(name);
          bfd->forwarding_override = -1;
          bfd->disc = generate_discriminator();
          hmap_insert(all_bfds, &bfd->node, bfd->disc);
  
          bfd->diag = DIAG_NONE;
          bfd->min_tx = 1000;
          bfd->mult = 3;
          ovs_refcount_init(&bfd->ref_cnt);
          bfd->netdev = netdev_ref(netdev);
          bfd->rx_packets = bfd_rx_packets(bfd);
          bfd->in_decay = false;
          bfd->flap_count = 0;
  
          /* RFC 5881 section 4
           * The source port MUST be in the range 49152 through 65535.  The same
           * UDP source port number MUST be used for all BFD Control packets
           * associated with a particular session.  The source port number SHOULD
           * be unique among all BFD sessions on the system. */
          bfd->udp_src = (atomic_count_inc(&udp_src) % 16384) + 49152;
  
          bfd_set_state(bfd, STATE_DOWN, DIAG_NONE);
  
          bfd_status_changed(bfd);
      }
  
      atomic_store_relaxed(&bfd->check_tnl_key,
                           smap_get_bool(cfg, "check_tnl_key", false));
      min_tx = smap_get_int(cfg, "min_tx", 100);
      min_tx = MAX(min_tx, 1);
      if (bfd->cfg_min_tx != min_tx) {
          bfd->cfg_min_tx = min_tx;
          if (bfd->state != STATE_UP
              || (!bfd_in_poll(bfd) && bfd->cfg_min_tx < bfd->min_tx)) {
              bfd->min_tx = bfd->cfg_min_tx;
          }
          need_poll = true;
      }
  
      min_rx = smap_get_int(cfg, "min_rx", 1000);
      min_rx = MAX(min_rx, 1);
      if (bfd->cfg_min_rx != min_rx) {
          bfd->cfg_min_rx = min_rx;
          if (bfd->state != STATE_UP
              || (!bfd_in_poll(bfd) && bfd->cfg_min_rx > bfd->min_rx)) {
              bfd->min_rx = bfd->cfg_min_rx;
          }
          cfg_min_rx_changed = true;
          need_poll = true;
      }
  
      decay_min_rx = smap_get_int(cfg, "decay_min_rx", 0);
      if (bfd->decay_min_rx != decay_min_rx || cfg_min_rx_changed) {
          if (decay_min_rx > 0 && decay_min_rx < bfd->cfg_min_rx) {
              VLOG_WARN("%s: decay_min_rx cannot be less than %lld ms",
                        bfd->name, bfd->cfg_min_rx);
              bfd->decay_min_rx = 0;
          } else {
              bfd->decay_min_rx = decay_min_rx;
          }
          /* Resets decay. */
          bfd->in_decay = false;
          bfd_decay_update(bfd);
          need_poll = true;
      }
  
      cpath_down = smap_get_bool(cfg, "cpath_down", false);
      if (bfd->cpath_down != cpath_down) {
          bfd->cpath_down = cpath_down;
          bfd_set_state(bfd, bfd->state, DIAG_NONE);
          need_poll = true;
      }
  
      hwaddr = smap_get(cfg, "bfd_local_src_mac");
      if (hwaddr && eth_addr_from_string(hwaddr, &ea)) {
          bfd->local_eth_src = ea;
      } else {
          bfd->local_eth_src = eth_addr_zero;
      }
  
      hwaddr = smap_get(cfg, "bfd_local_dst_mac");
      if (hwaddr && eth_addr_from_string(hwaddr, &ea)) {
          bfd->local_eth_dst = ea;
      } else {
          bfd->local_eth_dst = eth_addr_zero;
      }
  
      hwaddr = smap_get(cfg, "bfd_remote_dst_mac");
      if (hwaddr && eth_addr_from_string(hwaddr, &ea)) {
          bfd->rmt_eth_dst = ea;
      } else {
          bfd->rmt_eth_dst = eth_addr_zero;
      }
  
      ip_src = smap_get(cfg, "bfd_src_ip");
      if (ip_src && bfd_lookup_ip(ip_src, &in_addr)) {
          memcpy(&bfd->ip_src, &in_addr, sizeof in_addr);
      } else {
          bfd->ip_src = htonl(0xA9FE0101); /* 169.254.1.1. */
      }
  
      ip_dst = smap_get(cfg, "bfd_dst_ip");
      if (ip_dst && bfd_lookup_ip(ip_dst, &in_addr)) {
          memcpy(&bfd->ip_dst, &in_addr, sizeof in_addr);
      } else {
          bfd->ip_dst = htonl(0xA9FE0100); /* 169.254.1.0. */
      }
  
      forwarding_if_rx = smap_get_bool(cfg, "forwarding_if_rx", false);
      if (bfd->forwarding_if_rx != forwarding_if_rx) {
          bfd->forwarding_if_rx = forwarding_if_rx;
          if (bfd->state == STATE_UP && bfd->forwarding_if_rx) {
              bfd_forwarding_if_rx_update(bfd);
          } else {
              bfd->forwarding_if_rx_detect_time = 0;
          }
      }
  
      if (need_poll) {
          bfd_poll(bfd);
      }
      ovs_mutex_unlock(&mutex);
      return bfd;
  }
  
  struct bfd *
  bfd_ref(const struct bfd *bfd_)
  {
      struct bfd *bfd = CONST_CAST(struct bfd *, bfd_);
      if (bfd) {
          ovs_refcount_ref(&bfd->ref_cnt);
      }
      return bfd;
  }
  
  void
  bfd_unref(struct bfd *bfd) OVS_EXCLUDED(mutex)
  {
      if (bfd && ovs_refcount_unref_relaxed(&bfd->ref_cnt) == 1) {
          ovs_mutex_lock(&mutex);
          bfd_status_changed(bfd);
          hmap_remove(all_bfds, &bfd->node);
          netdev_close(bfd->netdev);
          free(bfd->name);
          free(bfd);
          ovs_mutex_unlock(&mutex);
      }
  }
  
  long long int
  bfd_wait(const struct bfd *bfd) OVS_EXCLUDED(mutex)
  {
      long long int wake_time = bfd_wake_time(bfd);
      poll_timer_wait_until(wake_time);
      return wake_time;
  }
  
  /* Returns the next wake up time. */
  long long int
  bfd_wake_time(const struct bfd *bfd) OVS_EXCLUDED(mutex)
  {
      long long int retval;
  
      if (!bfd) {
          return LLONG_MAX;
      }
  
      ovs_mutex_lock(&mutex);
      if (bfd->flags & FLAG_FINAL) {
          retval = 0;
      } else {
          retval = bfd->next_tx;
          if (bfd->state > STATE_DOWN) {
              retval = MIN(bfd->detect_time, retval);
          }
      }
      ovs_mutex_unlock(&mutex);
      return retval;
  }
  
  void
  bfd_run(struct bfd *bfd) OVS_EXCLUDED(mutex)
  {
      long long int now;
      bool old_in_decay;
  
      ovs_mutex_lock(&mutex);
      now = time_msec();
      old_in_decay = bfd->in_decay;
  
      if (bfd->state > STATE_DOWN && now >= bfd->detect_time) {
          bfd_set_state(bfd, STATE_DOWN, DIAG_EXPIRED);
      }
      bfd_forwarding__(bfd);
  
      /* Decay may only happen when state is STATE_UP, bfd->decay_min_rx is
       * configured, and decay_detect_time is reached. */
      if (bfd->state == STATE_UP && bfd->decay_min_rx > 0
          && now >= bfd->decay_detect_time) {
          bfd_try_decay(bfd);
      }
  
      if (bfd->min_tx != bfd->cfg_min_tx
          || (bfd->min_rx != bfd->cfg_min_rx && bfd->min_rx != bfd->decay_min_rx)
          || bfd->in_decay != old_in_decay) {
          bfd_poll(bfd);
      }
      ovs_mutex_unlock(&mutex);
  }
  
  bool
  bfd_should_send_packet(const struct bfd *bfd) OVS_EXCLUDED(mutex)
  {
      bool ret;
      ovs_mutex_lock(&mutex);
      ret = bfd->flags & FLAG_FINAL || time_msec() >= bfd->next_tx;
      ovs_mutex_unlock(&mutex);
      return ret;
  }
  
  void
  bfd_put_packet(struct bfd *bfd, struct dp_packet *p,
                 const struct eth_addr eth_src) OVS_EXCLUDED(mutex)
  {
      long long int min_tx, min_rx;
      struct udp_header *udp;
      struct eth_header *eth;
      struct ip_header *ip;
      struct msg *msg;
  
      ovs_mutex_lock(&mutex);
      if (bfd->next_tx) {
          long long int delay = time_msec() - bfd->next_tx;
          long long int interval = bfd_tx_interval(bfd);
          if (delay > interval * 3 / 2) {
              VLOG_INFO("%s: long delay of %lldms (expected %lldms) sending BFD"
                        " control message", bfd->name, delay, interval);
          }
      }
  
      /* RFC 5880 Section 6.5
       * A BFD Control packet MUST NOT have both the Poll (P) and Final (F) bits
       * set. */
      ovs_assert(!(bfd->flags & FLAG_POLL) || !(bfd->flags & FLAG_FINAL));
  
      dp_packet_reserve(p, 2); /* Properly align after the ethernet header. */
      eth = dp_packet_put_uninit(p, sizeof *eth);
      eth->eth_src = eth_addr_is_zero(bfd->local_eth_src)
          ? eth_src : bfd->local_eth_src;
      eth->eth_dst = eth_addr_is_zero(bfd->local_eth_dst)
          ? eth_addr_bfd : bfd->local_eth_dst;
      eth->eth_type = htons(ETH_TYPE_IP);
  
      ip = dp_packet_put_zeros(p, sizeof *ip);
      ip->ip_ihl_ver = IP_IHL_VER(5, 4);
      ip->ip_tot_len = htons(sizeof *ip + sizeof *udp + sizeof *msg);
      ip->ip_ttl = MAXTTL;
      ip->ip_tos = IPTOS_LOWDELAY | IPTOS_THROUGHPUT;
      ip->ip_proto = IPPROTO_UDP;
      put_16aligned_be32(&ip->ip_src, bfd->ip_src);
      put_16aligned_be32(&ip->ip_dst, bfd->ip_dst);
      ip->ip_csum = csum(ip, sizeof *ip);
  
      udp = dp_packet_put_zeros(p, sizeof *udp);
      udp->udp_src = htons(bfd->udp_src);
      udp->udp_dst = htons(BFD_DEST_PORT);
      udp->udp_len = htons(sizeof *udp + sizeof *msg);
  
      msg = dp_packet_put_uninit(p, sizeof *msg);
      msg->vers_diag = (BFD_VERSION << 5) | bfd->diag;
      msg->flags = (bfd->state & STATE_MASK) | bfd->flags;
  
      msg->mult = bfd->mult;
      msg->length = BFD_PACKET_LEN;
      msg->my_disc = htonl(bfd->disc);
      msg->your_disc = htonl(bfd->rmt_disc);
      msg->min_rx_echo = htonl(0);
  
      if (bfd_in_poll(bfd)) {
          min_tx = bfd->poll_min_tx;
          min_rx = bfd->poll_min_rx;
      } else {
          min_tx = bfd_min_tx(bfd);
          min_rx = bfd->min_rx;
      }
  
      msg->min_tx = htonl(min_tx * 1000);
      msg->min_rx = htonl(min_rx * 1000);
  
      bfd->flags &= ~FLAG_FINAL;
  
      log_msg(VLL_DBG, msg, "Sending BFD Message", bfd);
  
      bfd->last_tx = time_msec();
      bfd_set_next_tx(bfd);
      ovs_mutex_unlock(&mutex);
  }
  
  bool
  bfd_should_process_flow(const struct bfd *bfd_, const struct flow *flow,
                          struct flow_wildcards *wc)
  {
      struct bfd *bfd = CONST_CAST(struct bfd *, bfd_);
  
      if (!eth_addr_is_zero(bfd->rmt_eth_dst)) {
          memset(&wc->masks.dl_dst, 0xff, sizeof wc->masks.dl_dst);
  
          if (!eth_addr_equals(bfd->rmt_eth_dst, flow->dl_dst)) {
              return false;
          }
      }
  
      if (flow->dl_type == htons(ETH_TYPE_IP)) {
          memset(&wc->masks.nw_proto, 0xff, sizeof wc->masks.nw_proto);
          if (flow->nw_proto == IPPROTO_UDP) {
              memset(&wc->masks.tp_dst, 0xff, sizeof wc->masks.tp_dst);
              if (flow->tp_dst == htons(BFD_DEST_PORT)) {
                  bool check_tnl_key;
  
                  atomic_read_relaxed(&bfd->check_tnl_key, &check_tnl_key);
                  if (check_tnl_key) {
                      memset(&wc->masks.tunnel.tun_id, 0xff,
                             sizeof wc->masks.tunnel.tun_id);
                      return flow->tunnel.tun_id == htonll(0);
                  }
                  return true;
              }
          }
      }
      return false;
  }
  
  void
  bfd_process_packet(struct bfd *bfd, const struct flow *flow,
                     const struct dp_packet *p) OVS_EXCLUDED(mutex)
  {
      uint32_t rmt_min_rx, pkt_your_disc;
      enum state rmt_state;
      enum flags flags;
      uint8_t version;
      struct msg *msg;
      const uint8_t *l7 = dp_packet_get_udp_payload(p);
  
      if (!l7) {
          return; /* No UDP payload. */
      }
  
      /* This function is designed to follow section RFC 5880 6.8.6 closely. */
  
      ovs_mutex_lock(&mutex);
      /* Increments the decay rx counter. */
      bfd->decay_rx_ctl++;
  
      bfd_forwarding__(bfd);
  
      if (flow->nw_ttl != 255) {
          /* XXX Should drop in the kernel to prevent DOS. */
          goto out;
      }
  
      msg = dp_packet_at(p, l7 - (uint8_t *)dp_packet_data(p), BFD_PACKET_LEN);
      if (!msg) {
          VLOG_INFO_RL(&rl, "%s: Received too-short BFD control message (only "
                       "%"PRIdPTR" bytes long, at least %d required).",
                       bfd->name, (uint8_t *) dp_packet_tail(p) - l7,
                       BFD_PACKET_LEN);
          goto out;
      }
  
      /* RFC 5880 Section 6.8.6
       * If the Length field is greater than the payload of the encapsulating
       * protocol, the packet MUST be discarded.
       *
       * Note that we make this check implicitly.  Above we use dp_packet_at() to
       * ensure that there are at least BFD_PACKET_LEN bytes in the payload of
       * the encapsulating protocol.  Below we require msg->length to be exactly
       * BFD_PACKET_LEN bytes. */
  
      flags = msg->flags & FLAGS_MASK;
      rmt_state = msg->flags & STATE_MASK;
      version = msg->vers_diag >> VERS_SHIFT;
  
      log_msg(VLL_DBG, msg, "Received BFD control message", bfd);
  
      if (version != BFD_VERSION) {
          log_msg(VLL_WARN, msg, "Incorrect version", bfd);
          goto out;
      }
  
      /* Technically this should happen after the length check. We don't support
       * authentication however, so it's simpler to do the check first. */
      if (flags & FLAG_AUTH) {
          log_msg(VLL_WARN, msg, "Authenticated control message with"
                     " authentication disabled", bfd);
          goto out;
      }
  
      if (msg->length != BFD_PACKET_LEN) {
          log_msg(VLL_WARN, msg, "Unexpected length", bfd);
          if (msg->length < BFD_PACKET_LEN) {
              goto out;
          }
      }
  
      if (!msg->mult) {
          log_msg(VLL_WARN, msg, "Zero multiplier", bfd);
          goto out;
      }
  
      if (flags & FLAG_MULTIPOINT) {
          log_msg(VLL_WARN, msg, "Unsupported multipoint flag", bfd);
          goto out;
      }
  
      if (!msg->my_disc) {
          log_msg(VLL_WARN, msg, "NULL my_disc", bfd);
          goto out;
      }
  
      pkt_your_disc = ntohl(msg->your_disc);
      if (pkt_your_disc) {
          /* Technically, we should use the your discriminator field to figure
           * out which 'struct bfd' this packet is destined towards.  That way a
           * bfd session could migrate from one interface to another
           * transparently.  This doesn't fit in with the OVS structure very
           * well, so in this respect, we are not compliant. */
         if (pkt_your_disc != bfd->disc) {
             log_msg(VLL_WARN, msg, "Incorrect your_disc", bfd);
             goto out;
         }
      } else if (rmt_state > STATE_DOWN) {
          log_msg(VLL_WARN, msg, "Null your_disc", bfd);
          goto out;
      }
  
      if (bfd->rmt_state != rmt_state) {
          bfd_status_changed(bfd);
      }
  
      bfd->rmt_disc = ntohl(msg->my_disc);
      bfd->rmt_state = rmt_state;
      bfd->rmt_flags = flags;
      bfd->rmt_diag = msg->vers_diag & DIAG_MASK;
  
      if (flags & FLAG_FINAL && bfd_in_poll(bfd)) {
          bfd->min_tx = bfd->poll_min_tx;
          bfd->min_rx = bfd->poll_min_rx;
          bfd->flags &= ~FLAG_POLL;
          log_msg(VLL_INFO, msg, "Poll sequence terminated", bfd);
      }
  
      if (flags & FLAG_POLL) {
          /* RFC 5880 Section 6.5
           * When the other system receives a Poll, it immediately transmits a
           * BFD Control packet with the Final (F) bit set, independent of any
           * periodic BFD Control packets it may be sending
           * (see section 6.8.7). */
          bfd->flags &= ~FLAG_POLL;
          bfd->flags |= FLAG_FINAL;
      }
  
      rmt_min_rx = MAX(ntohl(msg->min_rx) / 1000, 1);
      if (bfd->rmt_min_rx != rmt_min_rx) {
          bfd->rmt_min_rx = rmt_min_rx;
          if (bfd->next_tx) {
              bfd_set_next_tx(bfd);
          }
          log_msg(VLL_INFO, msg, "New remote min_rx", bfd);
      }
  
      bfd->rmt_min_tx = MAX(ntohl(msg->min_tx) / 1000, 1);
      bfd->detect_time = bfd_rx_interval(bfd) * bfd->mult + time_msec();
  
      if (bfd->state == STATE_ADMIN_DOWN) {
          VLOG_DBG_RL(&rl, "Administratively down, dropping control message.");
          goto out;
      }
  
      if (rmt_state == STATE_ADMIN_DOWN) {
          if (bfd->state != STATE_DOWN) {
              bfd_set_state(bfd, STATE_DOWN, DIAG_RMT_DOWN);
          }
      } else {
          switch (bfd->state) {
          case STATE_DOWN:
              if (rmt_state == STATE_DOWN) {
                  bfd_set_state(bfd, STATE_INIT, bfd->diag);
              } else if (rmt_state == STATE_INIT) {
                  bfd_set_state(bfd, STATE_UP, bfd->diag);
              }
              break;
          case STATE_INIT:
              if (rmt_state > STATE_DOWN) {
                  bfd_set_state(bfd, STATE_UP, bfd->diag);
              }
              break;
          case STATE_UP:
              if (rmt_state <= STATE_DOWN) {
                  bfd_set_state(bfd, STATE_DOWN, DIAG_RMT_DOWN);
                  log_msg(VLL_INFO, msg, "Remote signaled STATE_DOWN", bfd);
              }
              break;
          case STATE_ADMIN_DOWN:
          default:
              OVS_NOT_REACHED();
          }
      }
      /* XXX: RFC 5880 Section 6.8.6 Demand mode related calculations here. */
  
      if (bfd->forwarding_if_rx) {
          bfd->demand_rx_bfd_time = time_msec() + 100 * bfd->cfg_min_rx;
      }
  
  out:
      bfd_forwarding__(bfd);
      ovs_mutex_unlock(&mutex);
  }
  
  /* Must be called when the netdev owned by 'bfd' should change. */
  void
  bfd_set_netdev(struct bfd *bfd, const struct netdev *netdev)
      OVS_EXCLUDED(mutex)
  {
      ovs_mutex_lock(&mutex);
      if (bfd->netdev != netdev) {
          netdev_close(bfd->netdev);
          bfd->netdev = netdev_ref(netdev);
          if (bfd->decay_min_rx && bfd->state == STATE_UP) {
              bfd_decay_update(bfd);
          }
          if (bfd->forwarding_if_rx && bfd->state == STATE_UP) {
              bfd_forwarding_if_rx_update(bfd);
          }
          bfd->rx_packets = bfd_rx_packets(bfd);
      }
      ovs_mutex_unlock(&mutex);
  }
  
  
  /* Updates the forwarding flag.  If override is not configured and
   * the forwarding flag value changes, increments the flap count.
   *
   * Note this function may be called multiple times in a function
   * (e.g. bfd_account_rx) before and after the bfd state or status
   * change.  This is to capture any forwarding flag flap. */
  static bool
  bfd_forwarding__(struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      long long int now = time_msec();
      bool forwarding_if_rx;
      bool last_forwarding = bfd->last_forwarding;
  
      if (bfd->forwarding_override != -1) {
          return bfd->forwarding_override == 1;
      }
  
      forwarding_if_rx = bfd->forwarding_if_rx
                         && bfd->forwarding_if_rx_detect_time > now
                         && bfd->demand_rx_bfd_time > now;
  
      bfd->last_forwarding = (bfd->state == STATE_UP || forwarding_if_rx)
                             && bfd->rmt_diag != DIAG_PATH_DOWN
                             && bfd->rmt_diag != DIAG_CPATH_DOWN
                             && bfd->rmt_diag != DIAG_RCPATH_DOWN;
      if (bfd->last_forwarding != last_forwarding) {
          bfd->flap_count++;
          bfd_status_changed(bfd);
      }
      return bfd->last_forwarding;
  }
  
  /* Helpers. */
  static bool
  bfd_lookup_ip(const char *host_name, struct in_addr *addr)
  {
      if (!ip_parse(host_name, &addr->s_addr)) {
          VLOG_ERR_RL(&rl, "\"%s\" is not a valid IP address", host_name);
          return false;
      }
      return true;
  }
  
  static bool
  bfd_in_poll(const struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      return (bfd->flags & FLAG_POLL) != 0;
  }
  
  static void
  bfd_poll(struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      if (bfd->state > STATE_DOWN && !bfd_in_poll(bfd)
          && !(bfd->flags & FLAG_FINAL)) {
          bfd->poll_min_tx = bfd->cfg_min_tx;
          bfd->poll_min_rx = bfd->in_decay ? bfd->decay_min_rx : bfd->cfg_min_rx;
          bfd->flags |= FLAG_POLL;
          bfd->next_tx = 0;
          VLOG_INFO_RL(&rl, "%s: Initiating poll sequence", bfd->name);
      }
  }
  
  static long long int
  bfd_min_tx(const struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      /* RFC 5880 Section 6.8.3
       * When bfd.SessionState is not Up, the system MUST set
       * bfd.DesiredMinTxInterval to a value of not less than one second
       * (1,000,000 microseconds).  This is intended to ensure that the
       * bandwidth consumed by BFD sessions that are not Up is negligible,
       * particularly in the case where a neighbor may not be running BFD. */
      return (bfd->state == STATE_UP ? bfd->min_tx : MAX(bfd->min_tx, 1000));
  }
  
  static long long int
  bfd_tx_interval(const struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      long long int interval = bfd_min_tx(bfd);
      return MAX(interval, bfd->rmt_min_rx);
  }
  
  static long long int
  bfd_rx_interval(const struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      return MAX(bfd->min_rx, bfd->rmt_min_tx);
  }
  
  static void
  bfd_set_next_tx(struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      long long int interval = bfd_tx_interval(bfd);
      interval -= interval * random_range(26) / 100;
      bfd->next_tx = bfd->last_tx + interval;
  }
  
  static const char *
  bfd_flag_str(enum flags flags)
  {
      struct ds ds = DS_EMPTY_INITIALIZER;
      static char flag_str[128];
  
      if (!flags) {
          return "none";
      }
  
      if (flags & FLAG_MULTIPOINT) {
          ds_put_cstr(&ds, "multipoint ");
      }
  
      if (flags & FLAG_DEMAND) {
          ds_put_cstr(&ds, "demand ");
      }
  
      if (flags & FLAG_AUTH) {
          ds_put_cstr(&ds, "auth ");
      }
  
      if (flags & FLAG_CTL) {
          ds_put_cstr(&ds, "ctl ");
      }
  
      if (flags & FLAG_FINAL) {
          ds_put_cstr(&ds, "final ");
      }
  
      if (flags & FLAG_POLL) {
          ds_put_cstr(&ds, "poll ");
      }
  
      /* Do not copy the trailing whitespace. */
      ds_chomp(&ds, ' ');
      ovs_strlcpy(flag_str, ds_cstr(&ds), sizeof flag_str);
      ds_destroy(&ds);
      return flag_str;
  }
  
  static const char *
  bfd_state_str(enum state state)
  {
      switch (state) {
      case STATE_ADMIN_DOWN: return "admin_down";
      case STATE_DOWN: return "down";
      case STATE_INIT: return "init";
      case STATE_UP: return "up";
      default: return "invalid";
      }
  }
  
  static const char *
  bfd_diag_str(enum diag diag) {
      switch (diag) {
      case DIAG_NONE: return "No Diagnostic";
      case DIAG_EXPIRED: return "Control Detection Time Expired";
      case DIAG_ECHO_FAILED: return "Echo Function Failed";
      case DIAG_RMT_DOWN: return "Neighbor Signaled Session Down";
      case DIAG_FWD_RESET: return "Forwarding Plane Reset";
      case DIAG_PATH_DOWN: return "Path Down";
      case DIAG_CPATH_DOWN: return "Concatenated Path Down";
      case DIAG_ADMIN_DOWN: return "Administratively Down";
      case DIAG_RCPATH_DOWN: return "Reverse Concatenated Path Down";
      default: return "Invalid Diagnostic";
      }
  };
  
  static void
  log_msg(enum vlog_level level, const struct msg *p, const char *message,
          const struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      struct ds ds = DS_EMPTY_INITIALIZER;
  
      if (vlog_should_drop(THIS_MODULE, level, &rl)) {
          return;
      }
  
      ds_put_format(&ds,
                    "%s: %s."
                    "\n\tvers:%"PRIu8" diag:\"%s\" state:%s mult:%"PRIu8
                    " length:%"PRIu8
                    "\n\tflags: %s"
                    "\n\tmy_disc:0x%"PRIx32" your_disc:0x%"PRIx32
                    "\n\tmin_tx:%"PRIu32"us (%"PRIu32"ms)"
                    "\n\tmin_rx:%"PRIu32"us (%"PRIu32"ms)"
                    "\n\tmin_rx_echo:%"PRIu32"us (%"PRIu32"ms)",
                    bfd->name, message, p->vers_diag >> VERS_SHIFT,
                    bfd_diag_str(p->vers_diag & DIAG_MASK),
                    bfd_state_str(p->flags & STATE_MASK),
                    p->mult, p->length, bfd_flag_str(p->flags & FLAGS_MASK),
                    ntohl(p->my_disc), ntohl(p->your_disc),
                    ntohl(p->min_tx), ntohl(p->min_tx) / 1000,
                    ntohl(p->min_rx), ntohl(p->min_rx) / 1000,
                    ntohl(p->min_rx_echo), ntohl(p->min_rx_echo) / 1000);
      bfd_put_details(&ds, bfd);
      VLOG(level, "%s", ds_cstr(&ds));
      ds_destroy(&ds);
  }
  
  static void
  bfd_set_state(struct bfd *bfd, enum state state, enum diag diag)
      OVS_REQUIRES(mutex)
  {
      if (bfd->cpath_down) {
          diag = DIAG_CPATH_DOWN;
      }
  
      if (bfd->state != state || bfd->diag != diag) {
          if (!VLOG_DROP_INFO(&rl)) {
              struct ds ds = DS_EMPTY_INITIALIZER;
  
              ds_put_format(&ds, "%s: BFD state change: %s->%s"
                            " \"%s\"->\"%s\".\n",
                            bfd->name, bfd_state_str(bfd->state),
                            bfd_state_str(state), bfd_diag_str(bfd->diag),
                            bfd_diag_str(diag));
              bfd_put_details(&ds, bfd);
              VLOG_INFO("%s", ds_cstr(&ds));
              ds_destroy(&ds);
          }
  
          bfd->state = state;
          bfd->diag = diag;
  
          if (bfd->state <= STATE_DOWN) {
              bfd->rmt_state = STATE_DOWN;
              bfd->rmt_diag = DIAG_NONE;
              bfd->rmt_min_rx = 1;
              bfd->rmt_flags = 0;
              bfd->rmt_disc = 0;
              bfd->rmt_min_tx = 0;
              /* Resets the min_rx if in_decay. */
              if (bfd->in_decay) {
                  bfd->min_rx = bfd->cfg_min_rx;
                  bfd->in_decay = false;
              }
          }
          /* Resets the decay when state changes to STATE_UP
           * and decay_min_rx is configured. */
          if (bfd->state == STATE_UP && bfd->decay_min_rx) {
              bfd_decay_update(bfd);
          }
  
          bfd_status_changed(bfd);
      }
  }
  
  static uint64_t
  bfd_rx_packets(const struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      struct netdev_stats stats;
  
      if (!netdev_get_stats(bfd->netdev, &stats)) {
          return stats.rx_packets;
      } else {
          return 0;
      }
  }
  
  /* Decays the bfd->min_rx to bfd->decay_min_rx when 'diff' is less than
   * the 'expect' value. */
  static void
  bfd_try_decay(struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      int64_t diff, expect;
  
      /* The 'diff' is the difference between current interface rx_packets
       * stats and last-time check.  The 'expect' is the recorded number of
       * bfd control packets received within an approximately decay_min_rx
       * (2000 ms if decay_min_rx is less than 2000 ms) interval.
       *
       * Since the update of rx_packets stats at interface happens
       * asynchronously to the bfd_rx_packets() function, the 'diff' value
       * can be jittered.  Thusly, we double the decay_rx_ctl to provide
       * more wiggle room. */
      diff = bfd_rx_packets(bfd) - bfd->decay_rx_packets;
      expect = 2 * MAX(bfd->decay_rx_ctl, 1);
      bfd->in_decay = diff <= expect ? true : false;
      bfd_decay_update(bfd);
  }
  
  /* Updates the rx_packets, decay_rx_ctl and decay_detect_time. */
  static void
  bfd_decay_update(struct bfd * bfd) OVS_REQUIRES(mutex)
  {
      bfd->decay_rx_packets = bfd_rx_packets(bfd);
      bfd->decay_rx_ctl = 0;
      bfd->decay_detect_time = MAX(bfd->decay_min_rx, 2000) + time_msec();
  }
  
  /* Records the status change and changes the global connectivity seq. */
  static void
  bfd_status_changed(struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      seq_change(connectivity_seq_get());
      bfd->status_changed = true;
  }
  
  static void
  bfd_forwarding_if_rx_update(struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      int64_t incr = bfd_rx_interval(bfd) * bfd->mult;
      bfd->forwarding_if_rx_detect_time = MAX(incr, 2000) + time_msec();
  }
  
  static uint32_t
  generate_discriminator(void)
  {
      uint32_t disc = 0;
  
      /* RFC 5880 Section 6.8.1
       * It SHOULD be set to a random (but still unique) value to improve
       * security.  The value is otherwise outside the scope of this
       * specification. */
  
      while (!disc) {
          struct bfd *bfd;
  
          /* 'disc' is by definition random, so there's no reason to waste time
           * hashing it. */
          disc = random_uint32();
          HMAP_FOR_EACH_IN_BUCKET (bfd, node, disc, all_bfds) {
              if (bfd->disc == disc) {
                  disc = 0;
                  break;
              }
          }
      }
  
      return disc;
  }
  
  static struct bfd *
  bfd_find_by_name(const char *name) OVS_REQUIRES(mutex)
  {
      struct bfd *bfd;
  
      HMAP_FOR_EACH (bfd, node, all_bfds) {
          if (!strcmp(bfd->name, name)) {
              return bfd;
          }
      }
      return NULL;
  }
  
  static void
  bfd_put_details(struct ds *ds, const struct bfd *bfd) OVS_REQUIRES(mutex)
  {
      ds_put_format(ds, "\tForwarding: %s\n",
                    bfd_forwarding__(CONST_CAST(struct bfd *, bfd))
                    ? "true" : "false");
      ds_put_format(ds, "\tDetect Multiplier: %d\n", bfd->mult);
      ds_put_format(ds, "\tConcatenated Path Down: %s\n",
                    bfd->cpath_down ? "true" : "false");
      ds_put_format(ds, "\tTX Interval: Approx %lldms\n", bfd_tx_interval(bfd));
      ds_put_format(ds, "\tRX Interval: Approx %lldms\n", bfd_rx_interval(bfd));
      ds_put_format(ds, "\tDetect Time: now %+lldms\n",
                    time_msec() - bfd->detect_time);
      ds_put_format(ds, "\tNext TX Time: now %+lldms\n",
                    time_msec() - bfd->next_tx);
      ds_put_format(ds, "\tLast TX Time: now %+lldms\n",
                    time_msec() - bfd->last_tx);
  
      ds_put_cstr(ds, "\n");
  
      ds_put_format(ds, "\tLocal Flags: %s\n", bfd_flag_str(bfd->flags));
      ds_put_format(ds, "\tLocal Session State: %s\n",
                    bfd_state_str(bfd->state));
      ds_put_format(ds, "\tLocal Diagnostic: %s\n", bfd_diag_str(bfd->diag));
      ds_put_format(ds, "\tLocal Discriminator: 0x%"PRIx32"\n", bfd->disc);
      ds_put_format(ds, "\tLocal Minimum TX Interval: %lldms\n",
                    bfd_min_tx(bfd));
      ds_put_format(ds, "\tLocal Minimum RX Interval: %lldms\n", bfd->min_rx);
  
      ds_put_cstr(ds, "\n");
  
      ds_put_format(ds, "\tRemote Flags: %s\n", bfd_flag_str(bfd->rmt_flags));
      ds_put_format(ds, "\tRemote Session State: %s\n",
                    bfd_state_str(bfd->rmt_state));
      ds_put_format(ds, "\tRemote Diagnostic: %s\n",
                    bfd_diag_str(bfd->rmt_diag));
      ds_put_format(ds, "\tRemote Discriminator: 0x%"PRIx32"\n", bfd->rmt_disc);
      ds_put_format(ds, "\tRemote Minimum TX Interval: %lldms\n",
                    bfd->rmt_min_tx);
      ds_put_format(ds, "\tRemote Minimum RX Interval: %lldms\n",
                    bfd->rmt_min_rx);
  }
  
  static void
  bfd_unixctl_show(struct unixctl_conn *conn, int argc, const char *argv[],
                   void *aux OVS_UNUSED) OVS_EXCLUDED(mutex)
  {
      struct ds ds = DS_EMPTY_INITIALIZER;
      struct bfd *bfd;
  
      ovs_mutex_lock(&mutex);
      if (argc > 1) {
          bfd = bfd_find_by_name(argv[1]);
          if (!bfd) {
              unixctl_command_reply_error(conn, "no such bfd object");
              goto out;
          }
          bfd_put_details(&ds, bfd);
      } else {
          HMAP_FOR_EACH (bfd, node, all_bfds) {
              ds_put_format(&ds, "---- %s ----\n", bfd->name);
              bfd_put_details(&ds, bfd);
          }
      }
      unixctl_command_reply(conn, ds_cstr(&ds));
      ds_destroy(&ds);
  
  out:
      ovs_mutex_unlock(&mutex);
  }
  
  
  static void
  bfd_unixctl_set_forwarding_override(struct unixctl_conn *conn, int argc,
                                      const char *argv[], void *aux OVS_UNUSED)
      OVS_EXCLUDED(mutex)
  {
      const char *forward_str = argv[argc - 1];
      int forwarding_override;
      struct bfd *bfd;
  
      ovs_mutex_lock(&mutex);
      if (!strcasecmp("true", forward_str)) {
          forwarding_override = 1;
      } else if (!strcasecmp("false", forward_str)) {
          forwarding_override = 0;
      } else if (!strcasecmp("normal", forward_str)) {
          forwarding_override = -1;
      } else {
          unixctl_command_reply_error(conn, "unknown fault string");
          goto out;
      }
  
      if (argc > 2) {
          bfd = bfd_find_by_name(argv[1]);
          if (!bfd) {
              unixctl_command_reply_error(conn, "no such BFD object");
              goto out;
          }
          bfd->forwarding_override = forwarding_override;
          bfd_status_changed(bfd);
      } else {
          HMAP_FOR_EACH (bfd, node, all_bfds) {
              bfd->forwarding_override = forwarding_override;
              bfd_status_changed(bfd);
          }
      }
  
      unixctl_command_reply(conn, "OK");
  
  out:
      ovs_mutex_unlock(&mutex);
  }
  