text: /*
   * Copyright (c) 2011-2016 Cisco and/or its affiliates.
   * 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.
   */
  /**
   * @file
   * @brief BFD nodes implementation
   */
  
  #if WITH_LIBSSL > 0
  #include <openssl/sha.h>
  #endif
  
  #if __SSE4_2__
  #include <x86intrin.h>
  #endif
  
  #include <vppinfra/random.h>
  #include <vppinfra/error.h>
  #include <vppinfra/hash.h>
  #include <vppinfra/xxhash.h>
  #include <vnet/ethernet/ethernet.h>
  #include <vnet/ethernet/packet.h>
  #include <vnet/bfd/bfd_debug.h>
  #include <vnet/bfd/bfd_protocol.h>
  #include <vnet/bfd/bfd_main.h>
  
  static u64
  bfd_calc_echo_checksum (u32 discriminator, u64 expire_time, u32 secret)
  {
    u64 checksum = 0;
  #if defined(clib_crc32c_uses_intrinsics) && !defined (__i386__)
    checksum = crc32_u64 (0, discriminator);
    checksum = crc32_u64 (checksum, expire_time);
    checksum = crc32_u64 (checksum, secret);
  #else
    checksum = clib_xxhash (discriminator ^ expire_time ^ secret);
  #endif
    return checksum;
  }
  
  static u64
  bfd_usec_to_clocks (const bfd_main_t * bm, u64 us)
  {
    return bm->cpu_cps * ((f64) us / USEC_PER_SECOND);
  }
  
  u32
  bfd_clocks_to_usec (const bfd_main_t * bm, u64 clocks)
  {
    return (clocks / bm->cpu_cps) * USEC_PER_SECOND;
  }
  
  static vlib_node_registration_t bfd_process_node;
  
  u8 *
  format_bfd_auth_key (u8 * s, va_list * args)
  {
    const bfd_auth_key_t *key = va_arg (*args, bfd_auth_key_t *);
    if (key)
      {
        s = format (s, "{auth-type=%u:%s, conf-key-id=%u, use-count=%u}, ",
  		  key->auth_type, bfd_auth_type_str (key->auth_type),
  		  key->conf_key_id, key->use_count);
      }
    else
      {
        s = format (s, "{none}");
      }
    return s;
  }
  
  /*
   * We actually send all bfd pkts to the "error" node after scanning
   * them, so the graph node has only one next-index. The "error-drop"
   * node automatically bumps our per-node packet counters for us.
   */
  typedef enum
  {
    BFD_INPUT_NEXT_NORMAL,
    BFD_INPUT_N_NEXT,
  } bfd_input_next_t;
  
  static void bfd_on_state_change (bfd_main_t * bm, bfd_session_t * bs, u64 now,
  				 int handling_wakeup);
  
  static void
  bfd_set_defaults (bfd_main_t * bm, bfd_session_t * bs)
  {
    bs->local_state = BFD_STATE_down;
    bs->local_diag = BFD_DIAG_CODE_no_diag;
    bs->remote_state = BFD_STATE_down;
    bs->remote_discr = 0;
    bs->hop_type = BFD_HOP_TYPE_SINGLE;
    bs->config_desired_min_tx_usec = BFD_DEFAULT_DESIRED_MIN_TX_USEC;
    bs->config_desired_min_tx_clocks = bm->default_desired_min_tx_clocks;
    bs->effective_desired_min_tx_clocks = bm->default_desired_min_tx_clocks;
    bs->remote_min_rx_usec = 1;
    bs->remote_min_rx_clocks = bfd_usec_to_clocks (bm, bs->remote_min_rx_usec);
    bs->remote_min_echo_rx_usec = 0;
    bs->remote_min_echo_rx_clocks = 0;
    bs->remote_demand = 0;
    bs->auth.remote_seq_number = 0;
    bs->auth.remote_seq_number_known = 0;
    bs->auth.local_seq_number = random_u32 (&bm->random_seed);
    bs->echo_secret = random_u32 (&bm->random_seed);
  }
  
  static void
  bfd_set_diag (bfd_session_t * bs, bfd_diag_code_e code)
  {
    if (bs->local_diag != code)
      {
        BFD_DBG ("set local_diag, bs_idx=%d: '%d:%s'", bs->bs_idx, code,
  	       bfd_diag_code_string (code));
        bs->local_diag = code;
      }
  }
  
  static void
  bfd_set_state (bfd_main_t * bm, bfd_session_t * bs,
  	       bfd_state_e new_state, int handling_wakeup)
  {
    if (bs->local_state != new_state)
      {
        BFD_DBG ("Change state, bs_idx=%d: %s->%s", bs->bs_idx,
  	       bfd_state_string (bs->local_state),
  	       bfd_state_string (new_state));
        bs->local_state = new_state;
        bfd_on_state_change (bm, bs, clib_cpu_time_now (), handling_wakeup);
      }
  }
  
  const char *
  bfd_poll_state_string (bfd_poll_state_e state)
  {
    switch (state)
      {
  #define F(x)         \
    case BFD_POLL_##x: \
      return "BFD_POLL_" #x;
        foreach_bfd_poll_state (F)
  #undef F
      }
    return "UNKNOWN";
  }
  
  static void
  bfd_set_poll_state (bfd_session_t * bs, bfd_poll_state_e state)
  {
    if (bs->poll_state != state)
      {
        BFD_DBG ("Setting poll state=%s, bs_idx=%u",
  	       bfd_poll_state_string (state), bs->bs_idx);
        bs->poll_state = state;
      }
  }
  
  static void
  bfd_recalc_tx_interval (bfd_main_t * bm, bfd_session_t * bs)
  {
    bs->transmit_interval_clocks =
      clib_max (bs->effective_desired_min_tx_clocks, bs->remote_min_rx_clocks);
    BFD_DBG ("Recalculated transmit interval " BFD_CLK_FMT,
  	   BFD_CLK_PRN (bs->transmit_interval_clocks));
  }
  
  static void
  bfd_recalc_echo_tx_interval (bfd_main_t * bm, bfd_session_t * bs)
  {
    bs->echo_transmit_interval_clocks =
      clib_max (bs->effective_desired_min_tx_clocks,
  	      bs->remote_min_echo_rx_clocks);
    BFD_DBG ("Recalculated echo transmit interval " BFD_CLK_FMT,
  	   BFD_CLK_PRN (bs->echo_transmit_interval_clocks));
  }
  
  static void
  bfd_calc_next_tx (bfd_main_t * bm, bfd_session_t * bs, u64 now)
  {
    if (bs->local_detect_mult > 1)
      {
        /* common case - 75-100% of transmit interval */
        bs->tx_timeout_clocks = bs->last_tx_clocks +
  	(1 - .25 * (random_f64 (&bm->random_seed))) *
  	bs->transmit_interval_clocks;
        if (bs->tx_timeout_clocks < now)
  	{
  	  /*
  	   * the timeout is in the past, which means that either remote
  	   * demand mode was set or performance/clock issues ...
  	   */
  	  BFD_DBG ("Missed %lu transmit events (now is %lu, calc "
  		   "tx_timeout is %lu)",
  		   (now - bs->tx_timeout_clocks) /
  		   bs->transmit_interval_clocks, now, bs->tx_timeout_clocks);
  	  bs->tx_timeout_clocks = now;
  	}
      }
    else
      {
        /* special case - 75-90% of transmit interval */
        bs->tx_timeout_clocks = bs->last_tx_clocks +
  	(.9 - .15 * (random_f64 (&bm->random_seed))) *
  	bs->transmit_interval_clocks;
        if (bs->tx_timeout_clocks < now)
  	{
  	  /*
  	   * the timeout is in the past, which means that either remote
  	   * demand mode was set or performance/clock issues ...
  	   */
  	  BFD_DBG ("Missed %lu transmit events (now is %lu, calc "
  		   "tx_timeout is %lu)",
  		   (now - bs->tx_timeout_clocks) /
  		   bs->transmit_interval_clocks, now, bs->tx_timeout_clocks);
  	  bs->tx_timeout_clocks = now;
  	}
      }
    if (bs->tx_timeout_clocks)
      {
        BFD_DBG ("Next transmit in %lu clocks/%.02fs@%lu",
  	       bs->tx_timeout_clocks - now,
  	       (bs->tx_timeout_clocks - now) / bm->cpu_cps,
  	       bs->tx_timeout_clocks);
      }
  }
  
  static void
  bfd_calc_next_echo_tx (bfd_main_t * bm, bfd_session_t * bs, u64 now)
  {
    bs->echo_tx_timeout_clocks =
      bs->echo_last_tx_clocks + bs->echo_transmit_interval_clocks;
    if (bs->echo_tx_timeout_clocks < now)
      {
        /* huh, we've missed it already, transmit now */
        BFD_DBG ("Missed %lu echo transmit events (now is %lu, calc tx_timeout "
  	       "is %lu)",
  	       (now - bs->echo_tx_timeout_clocks) /
  	       bs->echo_transmit_interval_clocks,
  	       now, bs->echo_tx_timeout_clocks);
        bs->echo_tx_timeout_clocks = now;
      }
    BFD_DBG ("Next echo transmit in %lu clocks/%.02fs@%lu",
  	   bs->echo_tx_timeout_clocks - now,
  	   (bs->echo_tx_timeout_clocks - now) / bm->cpu_cps,
  	   bs->echo_tx_timeout_clocks);
  }
  
  static void
  bfd_recalc_detection_time (bfd_main_t * bm, bfd_session_t * bs)
  {
    if (bs->local_state == BFD_STATE_init || bs->local_state == BFD_STATE_up)
      {
        bs->detection_time_clocks =
  	bs->remote_detect_mult *
  	clib_max (bs->effective_required_min_rx_clocks,
  		  bs->remote_desired_min_tx_clocks);
        BFD_DBG ("Recalculated detection time %lu clocks/%.2fs",
  	       bs->detection_time_clocks,
  	       bs->detection_time_clocks / bm->cpu_cps);
      }
  }
  
  static void
  bfd_set_timer (bfd_main_t * bm, bfd_session_t * bs, u64 now,
  	       int handling_wakeup)
  {
    u64 next = 0;
    u64 rx_timeout = 0;
    u64 tx_timeout = 0;
    if (BFD_STATE_up == bs->local_state)
      {
        rx_timeout = bs->last_rx_clocks + bs->detection_time_clocks;
      }
    if (BFD_STATE_up != bs->local_state ||
        (!bs->remote_demand && bs->remote_min_rx_usec) ||
        BFD_POLL_NOT_NEEDED != bs->poll_state)
      {
        tx_timeout = bs->tx_timeout_clocks;
      }
    if (tx_timeout && rx_timeout)
      {
        next = clib_min (tx_timeout, rx_timeout);
      }
    else if (tx_timeout)
      {
        next = tx_timeout;
      }
    else if (rx_timeout)
      {
        next = rx_timeout;
      }
    if (bs->echo && next > bs->echo_tx_timeout_clocks)
      {
        next = bs->echo_tx_timeout_clocks;
      }
    BFD_DBG ("bs_idx=%u, tx_timeout=%lu, echo_tx_timeout=%lu, rx_timeout=%lu, "
  	   "next=%s",
  	   bs->bs_idx, tx_timeout, bs->echo_tx_timeout_clocks, rx_timeout,
  	   next == tx_timeout
  	   ? "tx" : (next == bs->echo_tx_timeout_clocks ? "echo tx" : "rx"));
    /* sometimes the wheel expires an event a bit sooner than requested, account
       for that here */
    if (next && (now + bm->wheel_inaccuracy > bs->wheel_time_clocks ||
  	       next < bs->wheel_time_clocks || !bs->wheel_time_clocks))
      {
        bs->wheel_time_clocks = next;
        BFD_DBG ("timing_wheel_insert(%p, %lu (%ld clocks/%.2fs in the "
  	       "future), %u);",
  	       &bm->wheel, bs->wheel_time_clocks,
  	       (i64) bs->wheel_time_clocks - clib_cpu_time_now (),
  	       (i64) (bs->wheel_time_clocks - clib_cpu_time_now ()) /
  	       bm->cpu_cps, bs->bs_idx);
        timing_wheel_insert (&bm->wheel, bs->wheel_time_clocks, bs->bs_idx);
        if (!handling_wakeup)
  	{
  	  vlib_process_signal_event (bm->vlib_main,
  				     bm->bfd_process_node_index,
  				     BFD_EVENT_RESCHEDULE, bs->bs_idx);
  	}
      }
  }
  
  static void
  bfd_set_effective_desired_min_tx (bfd_main_t * bm,
  				  bfd_session_t * bs, u64 now,
  				  u64 desired_min_tx_clocks)
  {
    bs->effective_desired_min_tx_clocks = desired_min_tx_clocks;
    BFD_DBG ("Set effective desired min tx to " BFD_CLK_FMT,
  	   BFD_CLK_PRN (bs->effective_desired_min_tx_clocks));
    bfd_recalc_detection_time (bm, bs);
    bfd_recalc_tx_interval (bm, bs);
    bfd_recalc_echo_tx_interval (bm, bs);
    bfd_calc_next_tx (bm, bs, now);
  }
  
  static void
  bfd_set_effective_required_min_rx (bfd_main_t * bm,
  				   bfd_session_t * bs,
  				   u64 required_min_rx_clocks)
  {
    bs->effective_required_min_rx_clocks = required_min_rx_clocks;
    BFD_DBG ("Set effective required min rx to " BFD_CLK_FMT,
  	   BFD_CLK_PRN (bs->effective_required_min_rx_clocks));
    bfd_recalc_detection_time (bm, bs);
  }
  
  static void
  bfd_set_remote_required_min_rx (bfd_main_t * bm, bfd_session_t * bs,
  				u64 now, u32 remote_required_min_rx_usec)
  {
    if (bs->remote_min_rx_usec != remote_required_min_rx_usec)
      {
        bs->remote_min_rx_usec = remote_required_min_rx_usec;
        bs->remote_min_rx_clocks =
  	bfd_usec_to_clocks (bm, remote_required_min_rx_usec);
        BFD_DBG ("Set remote min rx to " BFD_CLK_FMT,
  	       BFD_CLK_PRN (bs->remote_min_rx_clocks));
        bfd_recalc_detection_time (bm, bs);
        bfd_recalc_tx_interval (bm, bs);
      }
  }
  
  static void
  bfd_set_remote_required_min_echo_rx (bfd_main_t * bm, bfd_session_t * bs,
  				     u64 now,
  				     u32 remote_required_min_echo_rx_usec)
  {
    if (bs->remote_min_echo_rx_usec != remote_required_min_echo_rx_usec)
      {
        bs->remote_min_echo_rx_usec = remote_required_min_echo_rx_usec;
        bs->remote_min_echo_rx_clocks =
  	bfd_usec_to_clocks (bm, bs->remote_min_echo_rx_usec);
        BFD_DBG ("Set remote min echo rx to " BFD_CLK_FMT,
  	       BFD_CLK_PRN (bs->remote_min_echo_rx_clocks));
        bfd_recalc_echo_tx_interval (bm, bs);
      }
  }
  
  static void
  bfd_notify_listeners (bfd_main_t * bm,
  		      bfd_listen_event_e event, const bfd_session_t * bs)
  {
    bfd_notify_fn_t *fn;
    vec_foreach (fn, bm->listeners)
    {
      (*fn) (event, bs);
    }
  }
  
  void
  bfd_session_start (bfd_main_t * bm, bfd_session_t * bs)
  {
    BFD_DBG ("\nStarting session: %U", format_bfd_session, bs);
    bfd_set_effective_required_min_rx (bm, bs,
  				     bs->config_required_min_rx_clocks);
    bfd_recalc_tx_interval (bm, bs);
    vlib_process_signal_event (bm->vlib_main, bm->bfd_process_node_index,
  			     BFD_EVENT_NEW_SESSION, bs->bs_idx);
    bfd_notify_listeners (bm, BFD_LISTEN_EVENT_CREATE, bs);
  }
  
  void
  bfd_session_set_flags (bfd_session_t * bs, u8 admin_up_down)
  {
    bfd_main_t *bm = &bfd_main;
    u64 now = clib_cpu_time_now ();
    if (admin_up_down)
      {
        BFD_DBG ("Session set admin-up, bs-idx=%u", bs->bs_idx);
        bfd_set_state (bm, bs, BFD_STATE_down, 0);
        bfd_set_diag (bs, BFD_DIAG_CODE_no_diag);
        bfd_calc_next_tx (bm, bs, now);
        bfd_set_timer (bm, bs, now, 0);
      }
    else
      {
        BFD_DBG ("Session set admin-down, bs-idx=%u", bs->bs_idx);
        bfd_set_diag (bs, BFD_DIAG_CODE_admin_down);
        bfd_set_state (bm, bs, BFD_STATE_admin_down, 0);
        bfd_calc_next_tx (bm, bs, now);
        bfd_set_timer (bm, bs, now, 0);
      }
  }
  
  u8 *
  bfd_input_format_trace (u8 * s, va_list * args)
  {
    CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
    CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
    const bfd_input_trace_t *t = va_arg (*args, bfd_input_trace_t *);
    const bfd_pkt_t *pkt = (bfd_pkt_t *) t->data;
    if (t->len > STRUCT_SIZE_OF (bfd_pkt_t, head))
      {
        s = format (s, "BFD v%u, diag=%u(%s), state=%u(%s),\n"
  		  "    flags=(P:%u, F:%u, C:%u, A:%u, D:%u, M:%u), "
  		  "detect_mult=%u, length=%u\n",
  		  bfd_pkt_get_version (pkt), bfd_pkt_get_diag_code (pkt),
  		  bfd_diag_code_string (bfd_pkt_get_diag_code (pkt)),
  		  bfd_pkt_get_state (pkt),
  		  bfd_state_string (bfd_pkt_get_state (pkt)),
  		  bfd_pkt_get_poll (pkt), bfd_pkt_get_final (pkt),
  		  bfd_pkt_get_control_plane_independent (pkt),
  		  bfd_pkt_get_auth_present (pkt), bfd_pkt_get_demand (pkt),
  		  bfd_pkt_get_multipoint (pkt), pkt->head.detect_mult,
  		  pkt->head.length);
        if (t->len >= sizeof (bfd_pkt_t) &&
  	  pkt->head.length >= sizeof (bfd_pkt_t))
  	{
  	  s = format (s, "    my discriminator: %u\n",
  		      clib_net_to_host_u32 (pkt->my_disc));
  	  s = format (s, "    your discriminator: %u\n",
  		      clib_net_to_host_u32 (pkt->your_disc));
  	  s = format (s, "    desired min tx interval: %u\n",
  		      clib_net_to_host_u32 (pkt->des_min_tx));
  	  s = format (s, "    required min rx interval: %u\n",
  		      clib_net_to_host_u32 (pkt->req_min_rx));
  	  s = format (s, "    required min echo rx interval: %u",
  		      clib_net_to_host_u32 (pkt->req_min_echo_rx));
  	}
        if (t->len >= sizeof (bfd_pkt_with_common_auth_t) &&
  	  pkt->head.length >= sizeof (bfd_pkt_with_common_auth_t) &&
  	  bfd_pkt_get_auth_present (pkt))
  	{
  	  const bfd_pkt_with_common_auth_t *with_auth = (void *) pkt;
  	  const bfd_auth_common_t *common = &with_auth->common_auth;
  	  s = format (s, "\n    auth len: %u\n", common->len);
  	  s = format (s, "    auth type: %u:%s\n", common->type,
  		      bfd_auth_type_str (common->type));
  	  if (t->len >= sizeof (bfd_pkt_with_sha1_auth_t) &&
  	      pkt->head.length >= sizeof (bfd_pkt_with_sha1_auth_t) &&
  	      (BFD_AUTH_TYPE_keyed_sha1 == common->type ||
  	       BFD_AUTH_TYPE_meticulous_keyed_sha1 == common->type))
  	    {
  	      const bfd_pkt_with_sha1_auth_t *with_sha1 = (void *) pkt;
  	      const bfd_auth_sha1_t *sha1 = &with_sha1->sha1_auth;
  	      s = format (s, "    seq num: %u\n",
  			  clib_net_to_host_u32 (sha1->seq_num));
  	      s = format (s, "    key id: %u\n", sha1->key_id);
  	      s = format (s, "    hash: %U", format_hex_bytes, sha1->hash,
  			  sizeof (sha1->hash));
  	    }
  	}
        else
  	{
  	  s = format (s, "\n");
  	}
      }
  
    return s;
  }
  
  static void
  bfd_on_state_change (bfd_main_t * bm, bfd_session_t * bs, u64 now,
  		     int handling_wakeup)
  {
    BFD_DBG ("\nState changed: %U", format_bfd_session, bs);
    bfd_event (bm, bs);
    switch (bs->local_state)
      {
      case BFD_STATE_admin_down:
        bs->echo = 0;
        bfd_set_effective_desired_min_tx (bm, bs, now,
  					clib_max
  					(bs->config_desired_min_tx_clocks,
  					 bm->default_desired_min_tx_clocks));
        bfd_set_effective_required_min_rx (bm, bs,
  					 bs->config_required_min_rx_clocks);
        bfd_set_timer (bm, bs, now, handling_wakeup);
        break;
      case BFD_STATE_down:
        bs->echo = 0;
        bfd_set_effective_desired_min_tx (bm, bs, now,
  					clib_max
  					(bs->config_desired_min_tx_clocks,
  					 bm->default_desired_min_tx_clocks));
        bfd_set_effective_required_min_rx (bm, bs,
  					 bs->config_required_min_rx_clocks);
        bfd_set_timer (bm, bs, now, handling_wakeup);
        break;
      case BFD_STATE_init:
        bs->echo = 0;
        bfd_set_effective_desired_min_tx (bm, bs, now,
  					bs->config_desired_min_tx_clocks);
        bfd_set_timer (bm, bs, now, handling_wakeup);
        break;
      case BFD_STATE_up:
        bfd_set_effective_desired_min_tx (bm, bs, now,
  					bs->config_desired_min_tx_clocks);
        if (BFD_POLL_NOT_NEEDED == bs->poll_state)
  	{
  	  bfd_set_effective_required_min_rx (bm, bs,
  					     bs->config_required_min_rx_clocks);
  	}
        bfd_set_timer (bm, bs, now, handling_wakeup);
        break;
      }
    bfd_notify_listeners (bm, BFD_LISTEN_EVENT_UPDATE, bs);
  }
  
  static void
  bfd_on_config_change (vlib_main_t * vm, vlib_node_runtime_t * rt,
  		      bfd_main_t * bm, bfd_session_t * bs, u64 now)
  {
    /*
     * if remote demand mode is set and we need to do a poll, set the next
     * timeout so that the session wakes up immediately
     */
    if (bs->remote_demand && BFD_POLL_NEEDED == bs->poll_state &&
        bs->poll_state_start_or_timeout_clocks < now)
      {
        bs->tx_timeout_clocks = now;
      }
    bfd_recalc_detection_time (bm, bs);
    bfd_set_timer (bm, bs, now, 0);
  }
  
  static void
  bfd_add_transport_layer (vlib_main_t * vm, u32 bi, bfd_session_t * bs)
  {
    switch (bs->transport)
      {
      case BFD_TRANSPORT_UDP4:
        BFD_DBG ("Transport bfd via udp4, bs_idx=%u", bs->bs_idx);
        bfd_add_udp4_transport (vm, bi, bs, 0 /* is_echo */ );
        break;
      case BFD_TRANSPORT_UDP6:
        BFD_DBG ("Transport bfd via udp6, bs_idx=%u", bs->bs_idx);
        bfd_add_udp6_transport (vm, bi, bs, 0 /* is_echo */ );
        break;
      }
  }
  
  static int
  bfd_transport_control_frame (vlib_main_t * vm, u32 bi, bfd_session_t * bs)
  {
    switch (bs->transport)
      {
      case BFD_TRANSPORT_UDP4:
        BFD_DBG ("Transport bfd via udp4, bs_idx=%u", bs->bs_idx);
        return bfd_transport_udp4 (vm, bi, bs);
        break;
      case BFD_TRANSPORT_UDP6:
        BFD_DBG ("Transport bfd via udp6, bs_idx=%u", bs->bs_idx);
        return bfd_transport_udp6 (vm, bi, bs);
        break;
      }
    return 0;
  }
  
  static int
  bfd_echo_add_transport_layer (vlib_main_t * vm, u32 bi, bfd_session_t * bs)
  {
    switch (bs->transport)
      {
      case BFD_TRANSPORT_UDP4:
        BFD_DBG ("Transport bfd echo via udp4, bs_idx=%u", bs->bs_idx);
        return bfd_add_udp4_transport (vm, bi, bs, 1 /* is_echo */ );
        break;
      case BFD_TRANSPORT_UDP6:
        BFD_DBG ("Transport bfd echo via udp6, bs_idx=%u", bs->bs_idx);
        return bfd_add_udp6_transport (vm, bi, bs, 1 /* is_echo */ );
        break;
      }
    return 0;
  }
  
  static int
  bfd_transport_echo (vlib_main_t * vm, u32 bi, bfd_session_t * bs)
  {
    switch (bs->transport)
      {
      case BFD_TRANSPORT_UDP4:
        BFD_DBG ("Transport bfd echo via udp4, bs_idx=%u", bs->bs_idx);
        return bfd_transport_udp4 (vm, bi, bs);
        break;
      case BFD_TRANSPORT_UDP6:
        BFD_DBG ("Transport bfd echo via udp6, bs_idx=%u", bs->bs_idx);
        return bfd_transport_udp6 (vm, bi, bs);
        break;
      }
    return 0;
  }
  
  #if WITH_LIBSSL > 0
  static void
  bfd_add_sha1_auth_section (vlib_buffer_t * b, bfd_session_t * bs)
  {
    bfd_pkt_with_sha1_auth_t *pkt = vlib_buffer_get_current (b);
    bfd_auth_sha1_t *auth = &pkt->sha1_auth;
    b->current_length += sizeof (*auth);
    pkt->pkt.head.length += sizeof (*auth);
    bfd_pkt_set_auth_present (&pkt->pkt);
    memset (auth, 0, sizeof (*auth));
    auth->type_len.type = bs->auth.curr_key->auth_type;
    /*
     * only meticulous authentication types require incrementing seq number
     * for every message, but doing so doesn't violate the RFC
     */
    ++bs->auth.local_seq_number;
    auth->type_len.len = sizeof (bfd_auth_sha1_t);
    auth->key_id = bs->auth.curr_bfd_key_id;
    auth->seq_num = clib_host_to_net_u32 (bs->auth.local_seq_number);
    /*
     * first copy the password into the packet, then calculate the hash
     * and finally replace the password with the calculated hash
     */
    clib_memcpy (auth->hash, bs->auth.curr_key->key,
  	       sizeof (bs->auth.curr_key->key));
    unsigned char hash[sizeof (auth->hash)];
    SHA1 ((unsigned char *) pkt, sizeof (*pkt), hash);
    BFD_DBG ("hashing: %U", format_hex_bytes, pkt, sizeof (*pkt));
    clib_memcpy (auth->hash, hash, sizeof (hash));
  }
  #endif
  
  static void
  bfd_add_auth_section (vlib_buffer_t * b, bfd_session_t * bs)
  {
    if (bs->auth.curr_key)
      {
        const bfd_auth_type_e auth_type = bs->auth.curr_key->auth_type;
        switch (auth_type)
  	{
  	case BFD_AUTH_TYPE_reserved:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_simple_password:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_keyed_md5:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_meticulous_keyed_md5:
  	  clib_warning ("Internal error, unexpected BFD auth type '%d'",
  			auth_type);
  	  break;
  #if WITH_LIBSSL > 0
  	case BFD_AUTH_TYPE_keyed_sha1:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_meticulous_keyed_sha1:
  	  bfd_add_sha1_auth_section (b, bs);
  	  break;
  #else
  	case BFD_AUTH_TYPE_keyed_sha1:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_meticulous_keyed_sha1:
  	  clib_warning ("Internal error, unexpected BFD auth type '%d'",
  			auth_type);
  	  break;
  #endif
  	}
      }
  }
  
  static int
  bfd_is_echo_possible (bfd_session_t * bs)
  {
    if (BFD_STATE_up == bs->local_state && BFD_STATE_up == bs->remote_state &&
        bs->remote_min_echo_rx_usec > 0)
      {
        switch (bs->transport)
  	{
  	case BFD_TRANSPORT_UDP4:
  	  return bfd_udp_is_echo_available (BFD_TRANSPORT_UDP4);
  	case BFD_TRANSPORT_UDP6:
  	  return bfd_udp_is_echo_available (BFD_TRANSPORT_UDP6);
  	}
      }
    return 0;
  }
  
  static void
  bfd_init_control_frame (bfd_main_t * bm, bfd_session_t * bs,
  			vlib_buffer_t * b)
  {
    bfd_pkt_t *pkt = vlib_buffer_get_current (b);
    u32 bfd_length = 0;
    bfd_length = sizeof (bfd_pkt_t);
    memset (pkt, 0, sizeof (*pkt));
    bfd_pkt_set_version (pkt, 1);
    bfd_pkt_set_diag_code (pkt, bs->local_diag);
    bfd_pkt_set_state (pkt, bs->local_state);
    pkt->head.detect_mult = bs->local_detect_mult;
    pkt->head.length = bfd_length;
    pkt->my_disc = bs->local_discr;
    pkt->your_disc = bs->remote_discr;
    pkt->des_min_tx = clib_host_to_net_u32 (bs->config_desired_min_tx_usec);
    if (bs->echo)
      {
        pkt->req_min_rx =
  	clib_host_to_net_u32 (bfd_clocks_to_usec
  			      (bm, bs->effective_required_min_rx_clocks));
      }
    else
      {
        pkt->req_min_rx =
  	clib_host_to_net_u32 (bs->config_required_min_rx_usec);
      }
    pkt->req_min_echo_rx = clib_host_to_net_u32 (1);
    b->current_length = bfd_length;
  }
  
  static void
  bfd_send_echo (vlib_main_t * vm, vlib_node_runtime_t * rt,
  	       bfd_main_t * bm, bfd_session_t * bs, u64 now)
  {
    if (!bfd_is_echo_possible (bs))
      {
        BFD_DBG ("\nSwitching off echo function: %U", format_bfd_session, bs);
        bs->echo = 0;
        return;
      }
    /* sometimes the wheel expires an event a bit sooner than requested,
       account
       for that here */
    if (now + bm->wheel_inaccuracy >= bs->echo_tx_timeout_clocks)
      {
        BFD_DBG ("\nSending echo packet: %U", format_bfd_session, bs);
        u32 bi;
        if (vlib_buffer_alloc (vm, &bi, 1) != 1)
  	{
  	  clib_warning ("buffer allocation failure");
  	  return;
  	}
        vlib_buffer_t *b = vlib_get_buffer (vm, bi);
        ASSERT (b->current_data == 0);
        memset (vnet_buffer (b), 0, sizeof (*vnet_buffer (b)));
        VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b);
        bfd_echo_pkt_t *pkt = vlib_buffer_get_current (b);
        memset (pkt, 0, sizeof (*pkt));
        pkt->discriminator = bs->local_discr;
        pkt->expire_time_clocks =
  	now + bs->echo_transmit_interval_clocks * bs->local_detect_mult;
        pkt->checksum =
  	bfd_calc_echo_checksum (bs->local_discr, pkt->expire_time_clocks,
  				bs->echo_secret);
        b->current_length = sizeof (*pkt);
        if (!bfd_echo_add_transport_layer (vm, bi, bs))
  	{
  	  BFD_ERR ("cannot send echo packet out, turning echo off");
  	  bs->echo = 0;
  	  vlib_buffer_free_one (vm, bi);
  	  return;
  	}
        if (!bfd_transport_echo (vm, bi, bs))
  	{
  	  BFD_ERR ("cannot send echo packet out, turning echo off");
  	  bs->echo = 0;
  	  vlib_buffer_free_one (vm, bi);
  	  return;
  	}
        bs->echo_last_tx_clocks = now;
        bfd_calc_next_echo_tx (bm, bs, now);
      }
    else
      {
        BFD_DBG
  	("No need to send echo packet now, now is %lu, tx_timeout is %lu",
  	 now, bs->echo_tx_timeout_clocks);
      }
  }
  
  static void
  bfd_send_periodic (vlib_main_t * vm, vlib_node_runtime_t * rt,
  		   bfd_main_t * bm, bfd_session_t * bs, u64 now)
  {
    if (!bs->remote_min_rx_usec && BFD_POLL_NOT_NEEDED == bs->poll_state)
      {
        BFD_DBG ("Remote min rx interval is zero, not sending periodic control "
  	       "frame");
        return;
      }
    if (BFD_POLL_NOT_NEEDED == bs->poll_state && bs->remote_demand &&
        BFD_STATE_up == bs->local_state && BFD_STATE_up == bs->remote_state)
      {
        /*
         * A system MUST NOT periodically transmit BFD Control packets if Demand
         * mode is active on the remote system (bfd.RemoteDemandMode is 1,
         * bfd.SessionState is Up, and bfd.RemoteSessionState is Up) and a Poll
         * Sequence is not being transmitted.
         */
        BFD_DBG ("Remote demand is set, not sending periodic control frame");
        return;
      }
    /*
     * sometimes the wheel expires an event a bit sooner than requested, account
     * for that here
     */
    if (now + bm->wheel_inaccuracy >= bs->tx_timeout_clocks)
      {
        BFD_DBG ("\nSending periodic control frame: %U", format_bfd_session,
  	       bs);
        u32 bi;
        if (vlib_buffer_alloc (vm, &bi, 1) != 1)
  	{
  	  clib_warning ("buffer allocation failure");
  	  return;
  	}
        vlib_buffer_t *b = vlib_get_buffer (vm, bi);
        ASSERT (b->current_data == 0);
        memset (vnet_buffer (b), 0, sizeof (*vnet_buffer (b)));
        VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b);
        bfd_init_control_frame (bm, bs, b);
        switch (bs->poll_state)
  	{
  	case BFD_POLL_NEEDED:
  	  if (now < bs->poll_state_start_or_timeout_clocks)
  	    {
  	      BFD_DBG ("Cannot start a poll sequence yet, need to wait "
  		       "for " BFD_CLK_FMT,
  		       BFD_CLK_PRN (bs->poll_state_start_or_timeout_clocks -
  				    now));
  	      break;
  	    }
  	  bs->poll_state_start_or_timeout_clocks = now;
  	  bfd_set_poll_state (bs, BFD_POLL_IN_PROGRESS);
  	  /* fallthrough */
  	case BFD_POLL_IN_PROGRESS:
  	case BFD_POLL_IN_PROGRESS_AND_QUEUED:
  	  bfd_pkt_set_poll (vlib_buffer_get_current (b));
  	  BFD_DBG ("Setting poll bit in packet, bs_idx=%u", bs->bs_idx);
  	  break;
  	case BFD_POLL_NOT_NEEDED:
  	  /* fallthrough */
  	  break;
  	}
        bfd_add_auth_section (b, bs);
        bfd_add_transport_layer (vm, bi, bs);
        if (!bfd_transport_control_frame (vm, bi, bs))
  	{
  	  vlib_buffer_free_one (vm, bi);
  	}
        bs->last_tx_clocks = now;
        bfd_calc_next_tx (bm, bs, now);
      }
    else
      {
        BFD_DBG
  	("No need to send control frame now, now is %lu, tx_timeout is %lu",
  	 now, bs->tx_timeout_clocks);
      }
  }
  
  void
  bfd_init_final_control_frame (vlib_main_t * vm, vlib_buffer_t * b,
  			      bfd_main_t * bm, bfd_session_t * bs,
  			      int is_local)
  {
    BFD_DBG ("Send final control frame for bs_idx=%lu", bs->bs_idx);
    bfd_init_control_frame (bm, bs, b);
    bfd_pkt_set_final (vlib_buffer_get_current (b));
    bfd_add_auth_section (b, bs);
    u32 bi = vlib_get_buffer_index (vm, b);
    bfd_add_transport_layer (vm, bi, bs);
    bs->last_tx_clocks = clib_cpu_time_now ();
    /*
     * RFC allows to include changes in final frame, so if there were any
     * pending, we already did that, thus we can clear any pending poll needs
     */
    bfd_set_poll_state (bs, BFD_POLL_NOT_NEEDED);
  }
  
  static void
  bfd_check_rx_timeout (bfd_main_t * bm, bfd_session_t * bs, u64 now,
  		      int handling_wakeup)
  {
    /*
     * sometimes the wheel expires an event a bit sooner than requested, account
     * for that here
     */
    if (bs->last_rx_clocks + bs->detection_time_clocks <=
        now + bm->wheel_inaccuracy)
      {
        BFD_DBG ("Rx timeout, session goes down");
        bfd_set_diag (bs, BFD_DIAG_CODE_det_time_exp);
        bfd_set_state (bm, bs, BFD_STATE_down, handling_wakeup);
        /*
         * If the remote system does not receive any
         * BFD Control packets for a Detection Time, it SHOULD reset
         * bfd.RemoteMinRxInterval to its initial value of 1 (per section 6.8.1,
         * since it is no longer required to maintain previous session state)
         * and then can transmit at its own rate.
         */
        bfd_set_remote_required_min_rx (bm, bs, now, 1);
      }
    else if (bs->echo &&
  	   bs->echo_last_rx_clocks +
  	   bs->echo_transmit_interval_clocks * bs->local_detect_mult <=
  	   now + bm->wheel_inaccuracy)
      {
        BFD_DBG ("Echo rx timeout, session goes down");
        bfd_set_diag (bs, BFD_DIAG_CODE_echo_failed);
        bfd_set_state (bm, bs, BFD_STATE_down, handling_wakeup);
      }
  }
  
  void
  bfd_on_timeout (vlib_main_t * vm, vlib_node_runtime_t * rt, bfd_main_t * bm,
  		bfd_session_t * bs, u64 now)
  {
    BFD_DBG ("Timeout for bs_idx=%lu", bs->bs_idx);
    switch (bs->local_state)
      {
      case BFD_STATE_admin_down:
        bfd_send_periodic (vm, rt, bm, bs, now);
        break;
      case BFD_STATE_down:
        bfd_send_periodic (vm, rt, bm, bs, now);
        break;
      case BFD_STATE_init:
        bfd_check_rx_timeout (bm, bs, now, 1);
        bfd_send_periodic (vm, rt, bm, bs, now);
        break;
      case BFD_STATE_up:
        bfd_check_rx_timeout (bm, bs, now, 1);
        if (BFD_POLL_NOT_NEEDED == bs->poll_state && !bs->echo &&
  	  bfd_is_echo_possible (bs))
  	{
  	  /* switch on echo function as main detection method now */
  	  BFD_DBG ("Switching on echo function, bs_idx=%u", bs->bs_idx);
  	  bs->echo = 1;
  	  bs->echo_last_rx_clocks = now;
  	  bs->echo_tx_timeout_clocks = now;
  	  bfd_set_effective_required_min_rx (bm, bs,
  					     clib_max
  					     (bm->min_required_min_rx_while_echo_clocks,
  					      bs->config_required_min_rx_clocks));
  	  bfd_set_poll_state (bs, BFD_POLL_NEEDED);
  	}
        bfd_send_periodic (vm, rt, bm, bs, now);
        if (bs->echo)
  	{
  	  bfd_send_echo (vm, rt, bm, bs, now);
  	}
        break;
      }
  }
  
  /*
   * bfd process node function
   */
  static uword
  bfd_process (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
  {
    bfd_main_t *bm = &bfd_main;
    u32 *expired = 0;
    uword event_type, *event_data = 0;
  
    /* So we can send events to the bfd process */
    bm->bfd_process_node_index = bfd_process_node.index;
  
    while (1)
      {
        u64 now = clib_cpu_time_now ();
        u64 next_expire = timing_wheel_next_expiring_elt_time (&bm->wheel);
        BFD_DBG ("timing_wheel_next_expiring_elt_time(%p) returns %lu",
  	       &bm->wheel, next_expire);
        if ((i64) next_expire < 0)
  	{
  	  BFD_DBG ("wait for event without timeout");
  	  (void) vlib_process_wait_for_event (vm);
  	  event_type = vlib_process_get_events (vm, &event_data);
  	}
        else
  	{
  	  f64 timeout = ((i64) next_expire - (i64) now) / bm->cpu_cps;
  	  BFD_DBG ("wait for event with timeout %.02f", timeout);
  	  if (timeout < 0)
  	    {
  	      BFD_DBG ("negative timeout, already expired, skipping wait");
  	      event_type = ~0;
  	    }
  	  else
  	    {
  	      (void) vlib_process_wait_for_event_or_clock (vm, timeout);
  	      event_type = vlib_process_get_events (vm, &event_data);
  	    }
  	}
        now = clib_cpu_time_now ();
        switch (event_type)
  	{
  	case ~0:		/* no events => timeout */
  	  /* nothing to do here */
  	  break;
  	case BFD_EVENT_RESCHEDULE:
  	  /* nothing to do here - reschedule is done automatically after
  	   * each event or timeout */
  	  break;
  	case BFD_EVENT_NEW_SESSION:
  	  if (!pool_is_free_index (bm->sessions, *event_data))
  	    {
  	      bfd_session_t *bs =
  		pool_elt_at_index (bm->sessions, *event_data);
  	      bfd_send_periodic (vm, rt, bm, bs, now);
  	      bfd_set_timer (bm, bs, now, 1);
  	    }
  	  else
  	    {
  	      BFD_DBG ("Ignoring event for non-existent session index %u",
  		       (u32) * event_data);
  	    }
  	  break;
  	case BFD_EVENT_CONFIG_CHANGED:
  	  if (!pool_is_free_index (bm->sessions, *event_data))
  	    {
  	      bfd_session_t *bs =
  		pool_elt_at_index (bm->sessions, *event_data);
  	      bfd_on_config_change (vm, rt, bm, bs, now);
  	    }
  	  else
  	    {
  	      BFD_DBG ("Ignoring event for non-existent session index %u",
  		       (u32) * event_data);
  	    }
  	  break;
  	default:
  	  clib_warning ("BUG: event type 0x%wx", event_type);
  	  break;
  	}
        BFD_DBG ("advancing wheel, now is %lu", now);
        BFD_DBG ("timing_wheel_advance (%p, %lu, %p, 0);", &bm->wheel, now,
  	       expired);
        expired = timing_wheel_advance (&bm->wheel, now, expired, 0);
        BFD_DBG ("Expired %d elements", vec_len (expired));
        u32 *p = NULL;
        vec_foreach (p, expired)
        {
  	const u32 bs_idx = *p;
  	if (!pool_is_free_index (bm->sessions, bs_idx))
  	  {
  	    bfd_session_t *bs = pool_elt_at_index (bm->sessions, bs_idx);
  	    bfd_on_timeout (vm, rt, bm, bs, now);
  	    bfd_set_timer (bm, bs, now, 1);
  	  }
        }
        if (expired)
  	{
  	  _vec_len (expired) = 0;
  	}
        if (event_data)
  	{
  	  _vec_len (event_data) = 0;
  	}
      }
  
    return 0;
  }
  
  /*
   * bfd process node declaration
   */
  /* *INDENT-OFF* */
  VLIB_REGISTER_NODE (bfd_process_node, static) = {
    .function = bfd_process,
    .type = VLIB_NODE_TYPE_PROCESS,
    .name = "bfd-process",
    .n_next_nodes = 0,
    .next_nodes = {},
  };
  /* *INDENT-ON* */
  
  static clib_error_t *
  bfd_sw_interface_up_down (vnet_main_t * vnm, u32 sw_if_index, u32 flags)
  {
    // bfd_main_t *bm = &bfd_main;
    // vnet_hw_interface_t *hi = vnet_get_sup_hw_interface (vnm, sw_if_index);
    if (!(flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP))
      {
        /* TODO */
      }
    return 0;
  }
  
  VNET_SW_INTERFACE_ADMIN_UP_DOWN_FUNCTION (bfd_sw_interface_up_down);
  
  static clib_error_t *
  bfd_hw_interface_up_down (vnet_main_t * vnm, u32 hw_if_index, u32 flags)
  {
    // bfd_main_t *bm = &bfd_main;
    if (flags & VNET_HW_INTERFACE_FLAG_LINK_UP)
      {
        /* TODO */
      }
    return 0;
  }
  
  VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION (bfd_hw_interface_up_down);
  
  void
  bfd_register_listener (bfd_notify_fn_t fn)
  {
    bfd_main_t *bm = &bfd_main;
  
    vec_add1 (bm->listeners, fn);
  }
  
  /*
   * setup function
   */
  static clib_error_t *
  bfd_main_init (vlib_main_t * vm)
  {
  #if BFD_DEBUG
    setbuf (stdout, NULL);
  #endif
    bfd_main_t *bm = &bfd_main;
    bm->random_seed = random_default_seed ();
    bm->vlib_main = vm;
    bm->vnet_main = vnet_get_main ();
    memset (&bm->wheel, 0, sizeof (bm->wheel));
    bm->cpu_cps = vm->clib_time.clocks_per_second;
    BFD_DBG ("cps is %.2f", bm->cpu_cps);
    bm->default_desired_min_tx_clocks =
      bfd_usec_to_clocks (bm, BFD_DEFAULT_DESIRED_MIN_TX_USEC);
    bm->min_required_min_rx_while_echo_clocks =
      bfd_usec_to_clocks (bm, BFD_REQUIRED_MIN_RX_USEC_WHILE_ECHO);
    const u64 now = clib_cpu_time_now ();
    timing_wheel_init (&bm->wheel, now, bm->cpu_cps);
    bm->wheel_inaccuracy = 2 << bm->wheel.log2_clocks_per_bin;
    return 0;
  }
  
  VLIB_INIT_FUNCTION (bfd_main_init);
  
  bfd_session_t *
  bfd_get_session (bfd_main_t * bm, bfd_transport_e t)
  {
    bfd_session_t *result;
    pool_get (bm->sessions, result);
    memset (result, 0, sizeof (*result));
    result->bs_idx = result - bm->sessions;
    result->transport = t;
    const unsigned limit = 1000;
    unsigned counter = 0;
    do
      {
        result->local_discr = random_u32 (&bm->random_seed);
        if (counter > limit)
  	{
  	  clib_warning ("Couldn't allocate unused session discriminator even "
  			"after %u tries!", limit);
  	  pool_put (bm->sessions, result);
  	  return NULL;
  	}
        ++counter;
      }
    while (hash_get (bm->session_by_disc, result->local_discr));
    bfd_set_defaults (bm, result);
    hash_set (bm->session_by_disc, result->local_discr, result->bs_idx);
    return result;
  }
  
  void
  bfd_put_session (bfd_main_t * bm, bfd_session_t * bs)
  {
    bfd_notify_listeners (bm, BFD_LISTEN_EVENT_DELETE, bs);
    if (bs->auth.curr_key)
      {
        --bs->auth.curr_key->use_count;
      }
    if (bs->auth.next_key)
      {
        --bs->auth.next_key->use_count;
      }
    hash_unset (bm->session_by_disc, bs->local_discr);
    pool_put (bm->sessions, bs);
  }
  
  bfd_session_t *
  bfd_find_session_by_idx (bfd_main_t * bm, uword bs_idx)
  {
    if (!pool_is_free_index (bm->sessions, bs_idx))
      {
        return pool_elt_at_index (bm->sessions, bs_idx);
      }
    return NULL;
  }
  
  bfd_session_t *
  bfd_find_session_by_disc (bfd_main_t * bm, u32 disc)
  {
    uword *p = hash_get (bfd_main.session_by_disc, disc);
    if (p)
      {
        return pool_elt_at_index (bfd_main.sessions, *p);
      }
    return NULL;
  }
  
  /**
   * @brief verify bfd packet - common checks
   *
   * @param pkt
   *
   * @return 1 if bfd packet is valid
   */
  int
  bfd_verify_pkt_common (const bfd_pkt_t * pkt)
  {
    if (1 != bfd_pkt_get_version (pkt))
      {
        BFD_ERR ("BFD verification failed - unexpected version: '%d'",
  	       bfd_pkt_get_version (pkt));
        return 0;
      }
    if (pkt->head.length < sizeof (bfd_pkt_t) ||
        (bfd_pkt_get_auth_present (pkt) &&
         pkt->head.length < sizeof (bfd_pkt_with_common_auth_t)))
      {
        BFD_ERR ("BFD verification failed - unexpected length: '%d' (auth "
  	       "present: %d)",
  	       pkt->head.length, bfd_pkt_get_auth_present (pkt));
        return 0;
      }
    if (!pkt->head.detect_mult)
      {
        BFD_ERR ("BFD verification failed - unexpected detect-mult: '%d'",
  	       pkt->head.detect_mult);
        return 0;
      }
    if (bfd_pkt_get_multipoint (pkt))
      {
        BFD_ERR ("BFD verification failed - unexpected multipoint: '%d'",
  	       bfd_pkt_get_multipoint (pkt));
        return 0;
      }
    if (!pkt->my_disc)
      {
        BFD_ERR ("BFD verification failed - unexpected my-disc: '%d'",
  	       pkt->my_disc);
        return 0;
      }
    if (!pkt->your_disc)
      {
        const u8 pkt_state = bfd_pkt_get_state (pkt);
        if (pkt_state != BFD_STATE_down && pkt_state != BFD_STATE_admin_down)
  	{
  	  BFD_ERR ("BFD verification failed - unexpected state: '%s' "
  		   "(your-disc is zero)", bfd_state_string (pkt_state));
  	  return 0;
  	}
      }
    return 1;
  }
  
  static void
  bfd_session_switch_auth_to_next (bfd_session_t * bs)
  {
    BFD_DBG ("Switching authentication key from %U to %U for bs_idx=%u",
  	   format_bfd_auth_key, bs->auth.curr_key, format_bfd_auth_key,
  	   bs->auth.next_key, bs->bs_idx);
    bs->auth.is_delayed = 0;
    if (bs->auth.curr_key)
      {
        --bs->auth.curr_key->use_count;
      }
    bs->auth.curr_key = bs->auth.next_key;
    bs->auth.next_key = NULL;
    bs->auth.curr_bfd_key_id = bs->auth.next_bfd_key_id;
  }
  
  static int
  bfd_auth_type_is_meticulous (bfd_auth_type_e auth_type)
  {
    if (BFD_AUTH_TYPE_meticulous_keyed_md5 == auth_type ||
        BFD_AUTH_TYPE_meticulous_keyed_sha1 == auth_type)
      {
        return 1;
      }
    return 0;
  }
  
  static int
  bfd_verify_pkt_auth_seq_num (bfd_session_t * bs,
  			     u32 received_seq_num, int is_meticulous)
  {
    /*
     * RFC 5880 6.8.1:
     *
     * This variable MUST be set to zero after no packets have been
     * received on this session for at least twice the Detection Time.
     */
    u64 now = clib_cpu_time_now ();
    if (now - bs->last_rx_clocks > bs->detection_time_clocks * 2)
      {
        BFD_DBG ("BFD peer unresponsive for %lu clocks, which is > 2 * "
  	       "detection_time=%u clocks, resetting remote_seq_number_known "
  	       "flag",
  	       now - bs->last_rx_clocks, bs->detection_time_clocks * 2);
        bs->auth.remote_seq_number_known = 0;
      }
    if (bs->auth.remote_seq_number_known)
      {
        /* remote sequence number is known, verify its validity */
        const u32 max_u32 = 0xffffffff;
        /* the calculation might wrap, account for the special case... */
        if (bs->auth.remote_seq_number > max_u32 - 3 * bs->local_detect_mult)
  	{
  	  /*
  	   * special case
  	   *
  	   *        x                   y                   z
  	   *  |----------+----------------------------+-----------|
  	   *  0          ^                            ^ 0xffffffff
  	   *             |        remote_seq_num------+
  	   *             |
  	   *             +-----(remote_seq_num + 3*detect_mult) % * 0xffffffff
  	   *
  	   *    x + y + z = 0xffffffff
  	   *    x + z = 3 * detect_mult
  	   */
  	  const u32 z = max_u32 - bs->auth.remote_seq_number;
  	  const u32 x = 3 * bs->local_detect_mult - z;
  	  if (received_seq_num > x &&
  	      received_seq_num < bs->auth.remote_seq_number + is_meticulous)
  	    {
  	      BFD_ERR
  		("Recvd sequence number=%u out of ranges <0, %u>, <%u, %u>",
  		 received_seq_num, x,
  		 bs->auth.remote_seq_number + is_meticulous, max_u32);
  	      return 0;
  	    }
  	}
        else
  	{
  	  /* regular case */
  	  const u32 min = bs->auth.remote_seq_number + is_meticulous;
  	  const u32 max =
  	    bs->auth.remote_seq_number + 3 * bs->local_detect_mult;
  	  if (received_seq_num < min || received_seq_num > max)
  	    {
  	      BFD_ERR ("Recvd sequence number=%u out of range <%u, %u>",
  		       received_seq_num, min, max);
  	      return 0;
  	    }
  	}
      }
    return 1;
  }
  
  static int
  bfd_verify_pkt_auth_key_sha1 (const bfd_pkt_t * pkt, u32 pkt_size,
  			      bfd_session_t * bs, u8 bfd_key_id,
  			      bfd_auth_key_t * auth_key)
  {
    ASSERT (auth_key->auth_type == BFD_AUTH_TYPE_keyed_sha1 ||
  	  auth_key->auth_type == BFD_AUTH_TYPE_meticulous_keyed_sha1);
  
    u8 result[SHA_DIGEST_LENGTH];
    bfd_pkt_with_common_auth_t *with_common = (void *) pkt;
    if (pkt_size < sizeof (*with_common))
      {
        BFD_ERR ("Packet size too small to hold authentication common header");
        return 0;
      }
    if (with_common->common_auth.type != auth_key->auth_type)
      {
        BFD_ERR ("BFD auth type mismatch, packet auth=%d:%s doesn't match "
  	       "in-use auth=%d:%s",
  	       with_common->common_auth.type,
  	       bfd_auth_type_str (with_common->common_auth.type),
  	       auth_key->auth_type, bfd_auth_type_str (auth_key->auth_type));
        return 0;
      }
    bfd_pkt_with_sha1_auth_t *with_sha1 = (void *) pkt;
    if (pkt_size < sizeof (*with_sha1) ||
        with_sha1->sha1_auth.type_len.len < sizeof (with_sha1->sha1_auth))
      {
        BFD_ERR
  	("BFD size mismatch, payload size=%u, expected=%u, auth_len=%u, "
  	 "expected=%u", pkt_size, sizeof (*with_sha1),
  	 with_sha1->sha1_auth.type_len.len, sizeof (with_sha1->sha1_auth));
        return 0;
      }
    if (with_sha1->sha1_auth.key_id != bfd_key_id)
      {
        BFD_ERR
  	("BFD key ID mismatch, packet key ID=%u doesn't match key ID=%u%s",
  	 with_sha1->sha1_auth.key_id, bfd_key_id,
  	 bs->
  	 auth.is_delayed ? " (but a delayed auth change is scheduled)" : "");
        return 0;
      }
    SHA_CTX ctx;
    if (!SHA1_Init (&ctx))
      {
        BFD_ERR ("SHA1_Init failed");
        return 0;
      }
    /* ignore last 20 bytes - use the actual key data instead pkt data */
    if (!SHA1_Update (&ctx, with_sha1,
  		    sizeof (*with_sha1) - sizeof (with_sha1->sha1_auth.hash)))
      {
        BFD_ERR ("SHA1_Update failed");
        return 0;
      }
    if (!SHA1_Update (&ctx, auth_key->key, sizeof (auth_key->key)))
      {
        BFD_ERR ("SHA1_Update failed");
        return 0;
      }
    if (!SHA1_Final (result, &ctx))
      {
        BFD_ERR ("SHA1_Final failed");
        return 0;
      }
    if (0 == memcmp (result, with_sha1->sha1_auth.hash, SHA_DIGEST_LENGTH))
      {
        return 1;
      }
    BFD_ERR ("SHA1 hash: %U doesn't match the expected value: %U",
  	   format_hex_bytes, with_sha1->sha1_auth.hash, SHA_DIGEST_LENGTH,
  	   format_hex_bytes, result, SHA_DIGEST_LENGTH);
    return 0;
  }
  
  static int
  bfd_verify_pkt_auth_key (const bfd_pkt_t * pkt, u32 pkt_size,
  			 bfd_session_t * bs, u8 bfd_key_id,
  			 bfd_auth_key_t * auth_key)
  {
    switch (auth_key->auth_type)
      {
      case BFD_AUTH_TYPE_reserved:
        clib_warning ("Internal error, unexpected auth_type=%d:%s",
  		    auth_key->auth_type,
  		    bfd_auth_type_str (auth_key->auth_type));
        return 0;
      case BFD_AUTH_TYPE_simple_password:
        clib_warning
  	("Internal error, not implemented, unexpected auth_type=%d:%s",
  	 auth_key->auth_type, bfd_auth_type_str (auth_key->auth_type));
        return 0;
      case BFD_AUTH_TYPE_keyed_md5:
        /* fallthrough */
      case BFD_AUTH_TYPE_meticulous_keyed_md5:
        clib_warning
  	("Internal error, not implemented, unexpected auth_type=%d:%s",
  	 auth_key->auth_type, bfd_auth_type_str (auth_key->auth_type));
        return 0;
      case BFD_AUTH_TYPE_keyed_sha1:
        /* fallthrough */
      case BFD_AUTH_TYPE_meticulous_keyed_sha1:
  #if WITH_LIBSSL > 0
        do
  	{
  	  const u32 seq_num = clib_net_to_host_u32 (((bfd_pkt_with_sha1_auth_t
  						      *) pkt)->
  						    sha1_auth.seq_num);
  	  return bfd_verify_pkt_auth_seq_num (bs, seq_num,
  					      bfd_auth_type_is_meticulous
  					      (auth_key->auth_type))
  	    && bfd_verify_pkt_auth_key_sha1 (pkt, pkt_size, bs, bfd_key_id,
  					     auth_key);
  	}
        while (0);
  #else
        clib_warning
  	("Internal error, attempt to use SHA1 without SSL support");
        return 0;
  #endif
      }
    return 0;
  }
  
  /**
   * @brief verify bfd packet - authentication
   *
   * @param pkt
   *
   * @return 1 if bfd packet is valid
   */
  int
  bfd_verify_pkt_auth (const bfd_pkt_t * pkt, u16 pkt_size, bfd_session_t * bs)
  {
    if (bfd_pkt_get_auth_present (pkt))
      {
        /* authentication present in packet */
        if (!bs->auth.curr_key)
  	{
  	  /* currently not using authentication - can we turn it on? */
  	  if (bs->auth.is_delayed && bs->auth.next_key)
  	    {
  	      /* yes, switch is scheduled - make sure the auth is valid */
  	      if (bfd_verify_pkt_auth_key (pkt, pkt_size, bs,
  					   bs->auth.next_bfd_key_id,
  					   bs->auth.next_key))
  		{
  		  /* auth matches next key, do the switch, packet is valid */
  		  bfd_session_switch_auth_to_next (bs);
  		  return 1;
  		}
  	    }
  	}
        else
  	{
  	  /* yes, using authentication, verify the key */
  	  if (bfd_verify_pkt_auth_key (pkt, pkt_size, bs,
  				       bs->auth.curr_bfd_key_id,
  				       bs->auth.curr_key))
  	    {
  	      /* verification passed, packet is valid */
  	      return 1;
  	    }
  	  else
  	    {
  	      /* verification failed - but maybe we need to switch key */
  	      if (bs->auth.is_delayed && bs->auth.next_key)
  		{
  		  /* delayed switch present, verify if that key works */
  		  if (bfd_verify_pkt_auth_key (pkt, pkt_size, bs,
  					       bs->auth.next_bfd_key_id,
  					       bs->auth.next_key))
  		    {
  		      /* auth matches next key, switch key, packet is valid */
  		      bfd_session_switch_auth_to_next (bs);
  		      return 1;
  		    }
  		}
  	    }
  	}
      }
    else
      {
        /* authentication in packet not present */
        if (pkt_size > sizeof (*pkt))
  	{
  	  BFD_ERR ("BFD verification failed - unexpected packet size '%d' "
  		   "(auth not present)", pkt_size);
  	  return 0;
  	}
        if (bs->auth.curr_key)
  	{
  	  /* currently authenticating - could we turn it off? */
  	  if (bs->auth.is_delayed && !bs->auth.next_key)
  	    {
  	      /* yes, delayed switch to NULL key is scheduled */
  	      bfd_session_switch_auth_to_next (bs);
  	      return 1;
  	    }
  	}
        else
  	{
  	  /* no auth in packet, no auth in use - packet is valid */
  	  return 1;
  	}
      }
    return 0;
  }
  
  void
  bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
  {
    bfd_session_t *bs = bfd_find_session_by_idx (bm, bs_idx);
    if (!bs || (pkt->your_disc && pkt->your_disc != bs->local_discr))
      {
        return;
      }
    BFD_DBG ("Scanning bfd packet, bs_idx=%d", bs->bs_idx);
    bs->remote_discr = pkt->my_disc;
    bs->remote_state = bfd_pkt_get_state (pkt);
    bs->remote_demand = bfd_pkt_get_demand (pkt);
    bs->remote_diag = bfd_pkt_get_diag_code (pkt);
    u64 now = clib_cpu_time_now ();
    bs->last_rx_clocks = now;
    if (bfd_pkt_get_auth_present (pkt))
      {
        bfd_auth_type_e auth_type =
  	((bfd_pkt_with_common_auth_t *) (pkt))->common_auth.type;
        switch (auth_type)
  	{
  	case BFD_AUTH_TYPE_reserved:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_simple_password:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_keyed_md5:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_meticulous_keyed_md5:
  	  clib_warning ("Internal error, unexpected auth_type=%d:%s",
  			auth_type, bfd_auth_type_str (auth_type));
  	  break;
  	case BFD_AUTH_TYPE_keyed_sha1:
  	  /* fallthrough */
  	case BFD_AUTH_TYPE_meticulous_keyed_sha1:
  	  do
  	    {
  	      bfd_pkt_with_sha1_auth_t *with_sha1 =
  		(bfd_pkt_with_sha1_auth_t *) pkt;
  	      bs->auth.remote_seq_number =
  		clib_net_to_host_u32 (with_sha1->sha1_auth.seq_num);
  	      bs->auth.remote_seq_number_known = 1;
  	      BFD_DBG ("Received sequence number %u",
  		       bs->auth.remote_seq_number);
  	    }
  	  while (0);
  	}
      }
    bs->remote_desired_min_tx_clocks =
      bfd_usec_to_clocks (bm, clib_net_to_host_u32 (pkt->des_min_tx));
    bs->remote_detect_mult = pkt->head.detect_mult;
    bfd_set_remote_required_min_rx (bm, bs, now,
  				  clib_net_to_host_u32 (pkt->req_min_rx));
    bfd_set_remote_required_min_echo_rx (bm, bs, now,
  				       clib_net_to_host_u32
  				       (pkt->req_min_echo_rx));
    if (bfd_pkt_get_final (pkt))
      {
        if (BFD_POLL_IN_PROGRESS == bs->poll_state)
  	{
  	  BFD_DBG ("Poll sequence terminated, bs_idx=%u", bs->bs_idx);
  	  bfd_set_poll_state (bs, BFD_POLL_NOT_NEEDED);
  	  if (BFD_STATE_up == bs->local_state)
  	    {
  	      bfd_set_effective_required_min_rx (bm, bs,
  						 clib_max (bs->echo *
  							   bm->min_required_min_rx_while_echo_clocks,
  							   bs->config_required_min_rx_clocks));
  	    }
  	}
        else if (BFD_POLL_IN_PROGRESS_AND_QUEUED == bs->poll_state)
  	{
  	  /*
  	   * next poll sequence must be delayed by at least the round trip
  	   * time, so calculate that here
  	   */
  	  BFD_DBG ("Next poll sequence can commence in " BFD_CLK_FMT,
  		   BFD_CLK_PRN (now -
  				bs->poll_state_start_or_timeout_clocks));
  	  bs->poll_state_start_or_timeout_clocks =
  	    now + (now - bs->poll_state_start_or_timeout_clocks);
  	  BFD_DBG
  	    ("Poll sequence terminated, but another is needed, bs_idx=%u",
  	     bs->bs_idx);
  	  bfd_set_poll_state (bs, BFD_POLL_NEEDED);
  	}
      }
    bfd_calc_next_tx (bm, bs, now);
    bfd_set_timer (bm, bs, now, 0);
    if (BFD_STATE_admin_down == bs->local_state)
      {
        BFD_DBG ("Session is admin-down, ignoring packet, bs_idx=%u",
  	       bs->bs_idx);
        return;
      }
    if (BFD_STATE_admin_down == bs->remote_state)
      {
        bfd_set_diag (bs, BFD_DIAG_CODE_neighbor_sig_down);
        bfd_set_state (bm, bs, BFD_STATE_down, 0);
      }
    else if (BFD_STATE_down == bs->local_state)
      {
        if (BFD_STATE_down == bs->remote_state)
  	{
  	  bfd_set_diag (bs, BFD_DIAG_CODE_no_diag);
  	  bfd_set_state (bm, bs, BFD_STATE_init, 0);
  	}
        else if (BFD_STATE_init == bs->remote_state)
  	{
  	  bfd_set_diag (bs, BFD_DIAG_CODE_no_diag);
  	  bfd_set_state (bm, bs, BFD_STATE_up, 0);
  	}
      }
    else if (BFD_STATE_init == bs->local_state)
      {
        if (BFD_STATE_up == bs->remote_state ||
  	  BFD_STATE_init == bs->remote_state)
  	{
  	  bfd_set_diag (bs, BFD_DIAG_CODE_no_diag);
  	  bfd_set_state (bm, bs, BFD_STATE_up, 0);
  	}
      }
    else				/* BFD_STATE_up == bs->local_state */
      {
        if (BFD_STATE_down == bs->remote_state)
  	{
  	  bfd_set_diag (bs, BFD_DIAG_CODE_neighbor_sig_down);
  	  bfd_set_state (bm, bs, BFD_STATE_down, 0);
  	}
      }
  }
  
  int
  bfd_consume_echo_pkt (bfd_main_t * bm, vlib_buffer_t * b)
  {
    bfd_echo_pkt_t *pkt = NULL;
    if (b->current_length != sizeof (*pkt))
      {
        return 0;
      }
    pkt = vlib_buffer_get_current (b);
    bfd_session_t *bs = bfd_find_session_by_disc (bm, pkt->discriminator);
    if (!bs)
      {
        return 0;
      }
    BFD_DBG ("Scanning bfd echo packet, bs_idx=%d", bs->bs_idx);
    u64 checksum =
      bfd_calc_echo_checksum (bs->local_discr, pkt->expire_time_clocks,
  			    bs->echo_secret);
    if (checksum != pkt->checksum)
      {
        BFD_DBG ("Invalid echo packet, checksum mismatch");
        return 1;
      }
    u64 now = clib_cpu_time_now ();
    if (pkt->expire_time_clocks < now)
      {
        BFD_DBG ("Stale packet received, expire time %lu < now %lu",
  	       pkt->expire_time_clocks, now);
      }
    else
      {
        bs->echo_last_rx_clocks = now;
      }
    return 1;
  }
  
  u8 *
  format_bfd_session (u8 * s, va_list * args)
  {
    const bfd_session_t *bs = va_arg (*args, bfd_session_t *);
    u32 indent = format_get_indent (s);
    s = format (s, "bs_idx=%u local-state=%s remote-state=%s\n"
  	      "%Ulocal-discriminator=%u remote-discriminator=%u\n"
  	      "%Ulocal-diag=%s echo-active=%s\n"
  	      "%Udesired-min-tx=%u required-min-rx=%u\n"
  	      "%Urequired-min-echo-rx=%u detect-mult=%u\n"
  	      "%Uremote-min-rx=%u remote-min-echo-rx=%u\n"
  	      "%Uremote-demand=%s poll-state=%s\n"
  	      "%Uauth: local-seq-num=%u remote-seq-num=%u\n"
  	      "%U      is-delayed=%s\n"
  	      "%U      curr-key=%U\n"
  	      "%U      next-key=%U",
  	      bs->bs_idx, bfd_state_string (bs->local_state),
  	      bfd_state_string (bs->remote_state), format_white_space, indent,
  	      bs->local_discr, bs->remote_discr, format_white_space, indent,
  	      bfd_diag_code_string (bs->local_diag),
  	      (bs->echo ? "yes" : "no"), format_white_space, indent,
  	      bs->config_desired_min_tx_usec, bs->config_required_min_rx_usec,
  	      format_white_space, indent, 1, bs->local_detect_mult,
  	      format_white_space, indent, bs->remote_min_rx_usec,
  	      bs->remote_min_echo_rx_usec, format_white_space, indent,
  	      (bs->remote_demand ? "yes" : "no"),
  	      bfd_poll_state_string (bs->poll_state), format_white_space,
  	      indent, bs->auth.local_seq_number, bs->auth.remote_seq_number,
  	      format_white_space, indent,
  	      (bs->auth.is_delayed ? "yes" : "no"), format_white_space,
  	      indent, format_bfd_auth_key, bs->auth.curr_key,
  	      format_white_space, indent, format_bfd_auth_key,
  	      bs->auth.next_key);
    return s;
  }
  
  unsigned
  bfd_auth_type_supported (bfd_auth_type_e auth_type)
  {
    if (auth_type == BFD_AUTH_TYPE_keyed_sha1 ||
        auth_type == BFD_AUTH_TYPE_meticulous_keyed_sha1)
      {
        return 1;
      }
    return 0;
  }
  
  vnet_api_error_t
  bfd_auth_activate (bfd_session_t * bs, u32 conf_key_id,
  		   u8 bfd_key_id, u8 is_delayed)
  {
    bfd_main_t *bm = &bfd_main;
    const uword *key_idx_p =
      hash_get (bm->auth_key_by_conf_key_id, conf_key_id);
    if (!key_idx_p)
      {
        clib_warning ("Authentication key with config ID %u doesn't exist)",
  		    conf_key_id);
        return VNET_API_ERROR_BFD_ENOENT;
      }
    const uword key_idx = *key_idx_p;
    bfd_auth_key_t *key = pool_elt_at_index (bm->auth_keys, key_idx);
    if (is_delayed)
      {
        if (bs->auth.next_key == key)
  	{
  	  /* already using this key, no changes required */
  	  return 0;
  	}
        bs->auth.next_key = key;
        bs->auth.next_bfd_key_id = bfd_key_id;
        bs->auth.is_delayed = 1;
      }
    else
      {
        if (bs->auth.curr_key == key)
  	{
  	  /* already using this key, no changes required */
  	  return 0;
  	}
        if (bs->auth.curr_key)
  	{
  	  --bs->auth.curr_key->use_count;
  	}
        bs->auth.curr_key = key;
        bs->auth.curr_bfd_key_id = bfd_key_id;
        bs->auth.is_delayed = 0;
      }
    ++key->use_count;
    BFD_DBG ("\nSession auth modified: %U", format_bfd_session, bs);
    return 0;
  }
  
  vnet_api_error_t
  bfd_auth_deactivate (bfd_session_t * bs, u8 is_delayed)
  {
  #if WITH_LIBSSL > 0
    if (!is_delayed)
      {
        /* not delayed - deactivate the current key right now */
        if (bs->auth.curr_key)
  	{
  	  --bs->auth.curr_key->use_count;
  	  bs->auth.curr_key = NULL;
  	}
        bs->auth.is_delayed = 0;
      }
    else
      {
        /* delayed - mark as so */
        bs->auth.is_delayed = 1;
      }
    /*
     * clear the next key unconditionally - either the auth change is not delayed
     * in which case the caller expects the session to not use authentication
     * from this point forward, or it is delayed, in which case the next_key
     * needs to be set to NULL to make it so in the future
     */
    if (bs->auth.next_key)
      {
        --bs->auth.next_key->use_count;
        bs->auth.next_key = NULL;
      }
    BFD_DBG ("\nSession auth modified: %U", format_bfd_session, bs);
    return 0;
  #else
    clib_warning ("SSL missing, cannot deactivate BFD authentication");
    return VNET_API_ERROR_BFD_NOTSUPP;
  #endif
  }
  
  vnet_api_error_t
  bfd_session_set_params (bfd_main_t * bm, bfd_session_t * bs,
  			u32 desired_min_tx_usec,
  			u32 required_min_rx_usec, u8 detect_mult)
  {
    if (bs->local_detect_mult != detect_mult ||
        bs->config_desired_min_tx_usec != desired_min_tx_usec ||
        bs->config_required_min_rx_usec != required_min_rx_usec)
      {
        BFD_DBG ("\nChanging session params: %U", format_bfd_session, bs);
        switch (bs->poll_state)
  	{
  	case BFD_POLL_NOT_NEEDED:
  	  if (BFD_STATE_up == bs->local_state ||
  	      BFD_STATE_init == bs->local_state)
  	    {
  	      /* poll sequence is not needed for detect multiplier change */
  	      if (bs->config_desired_min_tx_usec != desired_min_tx_usec ||
  		  bs->config_required_min_rx_usec != required_min_rx_usec)
  		{
  		  bfd_set_poll_state (bs, BFD_POLL_NEEDED);
  		}
  	    }
  	  break;
  	case BFD_POLL_NEEDED:
  	case BFD_POLL_IN_PROGRESS_AND_QUEUED:
  	  /*
  	   * nothing to do - will be handled in the future poll which is
  	   * already scheduled for execution
  	   */
  	  break;
  	case BFD_POLL_IN_PROGRESS:
  	  /* poll sequence is not needed for detect multiplier change */
  	  if (bs->config_desired_min_tx_usec != desired_min_tx_usec ||
  	      bs->config_required_min_rx_usec != required_min_rx_usec)
  	    {
  	      BFD_DBG ("Poll in progress, queueing extra poll, bs_idx=%u",
  		       bs->bs_idx);
  	      bfd_set_poll_state (bs, BFD_POLL_IN_PROGRESS_AND_QUEUED);
  	    }
  	}
  
        bs->local_detect_mult = detect_mult;
        bs->config_desired_min_tx_usec = desired_min_tx_usec;
        bs->config_desired_min_tx_clocks =
  	bfd_usec_to_clocks (bm, desired_min_tx_usec);
        bs->config_required_min_rx_usec = required_min_rx_usec;
        bs->config_required_min_rx_clocks =
  	bfd_usec_to_clocks (bm, required_min_rx_usec);
        BFD_DBG ("\nChanged session params: %U", format_bfd_session, bs);
  
        vlib_process_signal_event (bm->vlib_main, bm->bfd_process_node_index,
  				 BFD_EVENT_CONFIG_CHANGED, bs->bs_idx);
      }
    else
      {
        BFD_DBG ("Ignore parameter change - no change, bs_idx=%u", bs->bs_idx);
      }
    return 0;
  }
  
  vnet_api_error_t
  bfd_auth_set_key (u32 conf_key_id, u8 auth_type, u8 key_len,
  		  const u8 * key_data)
  {
  #if WITH_LIBSSL > 0
    bfd_auth_key_t *auth_key = NULL;
    if (!key_len || key_len > bfd_max_key_len_for_auth_type (auth_type))
      {
        clib_warning ("Invalid authentication key length for auth_type=%d:%s "
  		    "(key_len=%u, must be "
  		    "non-zero, expected max=%u)",
  		    auth_type, bfd_auth_type_str (auth_type), key_len,
  		    (u32) bfd_max_key_len_for_auth_type (auth_type));
        return VNET_API_ERROR_INVALID_VALUE;
      }
    if (!bfd_auth_type_supported (auth_type))
      {
        clib_warning ("Unsupported auth type=%d:%s", auth_type,
  		    bfd_auth_type_str (auth_type));
        return VNET_API_ERROR_BFD_NOTSUPP;
      }
    bfd_main_t *bm = &bfd_main;
    uword *key_idx_p = hash_get (bm->auth_key_by_conf_key_id, conf_key_id);
    if (key_idx_p)
      {
        /* modifying existing key - must not be used */
        const uword key_idx = *key_idx_p;
        auth_key = pool_elt_at_index (bm->auth_keys, key_idx);
        if (auth_key->use_count > 0)
  	{
  	  clib_warning ("Authentication key with conf ID %u in use by %u BFD "
  			"session(s) - cannot modify",
  			conf_key_id, auth_key->use_count);
  	  return VNET_API_ERROR_BFD_EINUSE;
  	}
      }
    else
      {
        /* adding new key */
        pool_get (bm->auth_keys, auth_key);
        auth_key->conf_key_id = conf_key_id;
        hash_set (bm->auth_key_by_conf_key_id, conf_key_id,
  		auth_key - bm->auth_keys);
      }
    auth_key->auth_type = auth_type;
    memset (auth_key->key, 0, sizeof (auth_key->key));
    clib_memcpy (auth_key->key, key_data, key_len);
    return 0;
  #else
    clib_warning ("SSL missing, cannot manipulate authentication keys");
    return VNET_API_ERROR_BFD_NOTSUPP;
  #endif
  }
  
  vnet_api_error_t
  bfd_auth_del_key (u32 conf_key_id)
  {
  #if WITH_LIBSSL > 0
    bfd_auth_key_t *auth_key = NULL;
    bfd_main_t *bm = &bfd_main;
    uword *key_idx_p = hash_get (bm->auth_key_by_conf_key_id, conf_key_id);
    if (key_idx_p)
      {
        /* deleting existing key - must not be used */
        const uword key_idx = *key_idx_p;
        auth_key = pool_elt_at_index (bm->auth_keys, key_idx);
        if (auth_key->use_count > 0)
  	{
  	  clib_warning ("Authentication key with conf ID %u in use by %u BFD "
  			"session(s) - cannot delete",
  			conf_key_id, auth_key->use_count);
  	  return VNET_API_ERROR_BFD_EINUSE;
  	}
        hash_unset (bm->auth_key_by_conf_key_id, conf_key_id);
        memset (auth_key, 0, sizeof (*auth_key));
        pool_put (bm->auth_keys, auth_key);
      }
    else
      {
        /* no such key */
        clib_warning ("Authentication key with conf ID %u does not exist",
  		    conf_key_id);
        return VNET_API_ERROR_BFD_ENOENT;
      }
    return 0;
  #else
    clib_warning ("SSL missing, cannot manipulate authentication keys");
    return VNET_API_ERROR_BFD_NOTSUPP;
  #endif
  }
  
  bfd_main_t bfd_main;
  
  /*
   * fd.io coding-style-patch-verification: ON
   *
   * Local Variables:
   * eval: (c-set-style "gnu")
   * End:
   */
  