bfd: use tw_timer_template instead of legacy wheel
[vpp.git] / src / vnet / bfd / bfd_main.c
index e25eadf..3570ae0 100644 (file)
  * @brief BFD nodes implementation
  */
 
+#if WITH_LIBSSL > 0
+#include <openssl/sha.h>
+#endif
+
+#if __SSE4_2__
+#include <x86intrin.h>
+#endif
+
+#include <vlibmemory/api.h>
 #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>
+#include <vlib/log.h>
 
 static u64
-bfd_us_to_clocks (bfd_main_t * bm, u64 us)
+bfd_calc_echo_checksum (u32 discriminator, u64 expire_time, u32 secret)
 {
-  return bm->cpu_cps * ((f64) us / USEC_PER_SECOND);
+  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 vlib_node_registration_t bfd_process_node;
+static u64
+bfd_usec_to_nsec (u64 us)
+{
+  return us * NSEC_PER_USEC;
+}
 
-typedef enum
+u32
+bfd_nsec_to_usec (u64 nsec)
 {
-#define F(t, n) BFD_OUTPUT_##t,
-  foreach_bfd_transport (F)
-#undef F
-    BFD_OUTPUT_N_NEXT,
-} bfd_output_next_t;
+  return nsec / NSEC_PER_USEC;
+}
 
-static u32 bfd_next_index_by_transport[] = {
-#define F(t, n) [BFD_TRANSPORT_##t] = BFD_OUTPUT_##t,
-  foreach_bfd_transport (F)
-#undef F
-};
+always_inline u64
+bfd_time_now_nsec (vlib_main_t * vm, f64 * vm_time)
+{
+  f64 _vm_time = vlib_time_now (vm);
+  if (vm_time)
+    *vm_time = _vm_time;
+  return _vm_time * NSEC_PER_SEC;
+}
+
+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
@@ -68,12 +111,20 @@ 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->local_demand = 0;
   bs->remote_discr = 0;
-  bs->desired_min_tx_us = BFD_DEFAULT_DESIRED_MIN_TX_US;
-  bs->desired_min_tx_clocks = bfd_us_to_clocks (bm, bs->desired_min_tx_us);
-  bs->remote_min_rx_us = 1;
+  bs->hop_type = BFD_HOP_TYPE_SINGLE;
+  bs->config_desired_min_tx_usec = BFD_DEFAULT_DESIRED_MIN_TX_USEC;
+  bs->config_desired_min_tx_nsec = bm->default_desired_min_tx_nsec;
+  bs->effective_desired_min_tx_nsec = bm->default_desired_min_tx_nsec;
+  bs->remote_min_rx_usec = 1;
+  bs->remote_min_rx_nsec = bfd_usec_to_nsec (bs->remote_min_rx_usec);
+  bs->remote_min_echo_rx_usec = 0;
+  bs->remote_min_echo_rx_nsec = 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
@@ -88,7 +139,7 @@ bfd_set_diag (bfd_session_t * bs, bfd_diag_code_e code)
 }
 
 static void
-bfd_set_state (bfd_main_t * bm, bfd_session_t * bs,
+bfd_set_state (vlib_main_t * vm, bfd_main_t * bm, bfd_session_t * bs,
               bfd_state_e new_state, int handling_wakeup)
 {
   if (bs->local_state != new_state)
@@ -97,104 +148,138 @@ bfd_set_state (bfd_main_t * bm, bfd_session_t * bs,
               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);
+      bfd_on_state_change (bm, bs, bfd_time_now_nsec (vm, NULL),
+                          handling_wakeup);
     }
 }
 
-static void
-bfd_recalc_tx_interval (bfd_main_t * bm, bfd_session_t * bs)
+const char *
+bfd_poll_state_string (bfd_poll_state_e state)
 {
-  if (!bs->local_demand)
+  switch (state)
     {
-      bs->transmit_interval_clocks =
-       clib_max (bs->desired_min_tx_clocks, bs->remote_min_rx_clocks);
+#define F(x)         \
+  case BFD_POLL_##x: \
+    return "BFD_POLL_" #x;
+      foreach_bfd_poll_state (F)
+#undef F
     }
-  else
+  return "UNKNOWN";
+}
+
+static void
+bfd_set_poll_state (bfd_session_t * bs, bfd_poll_state_e state)
+{
+  if (bs->poll_state != state)
     {
-      /* TODO */
+      BFD_DBG ("Setting poll state=%s, bs_idx=%u",
+              bfd_poll_state_string (state), bs->bs_idx);
+      bs->poll_state = state;
     }
-  BFD_DBG ("Recalculated transmit interval %lu clocks/%.2fs",
-          bs->transmit_interval_clocks,
-          bs->transmit_interval_clocks / bm->cpu_cps);
+}
+
+static void
+bfd_recalc_tx_interval (bfd_main_t * bm, bfd_session_t * bs)
+{
+  bs->transmit_interval_nsec =
+    clib_max (bs->effective_desired_min_tx_nsec, bs->remote_min_rx_nsec);
+  BFD_DBG ("Recalculated transmit interval " BFD_CLK_FMT,
+          BFD_CLK_PRN (bs->transmit_interval_nsec));
+}
+
+static void
+bfd_recalc_echo_tx_interval (bfd_main_t * bm, bfd_session_t * bs)
+{
+  bs->echo_transmit_interval_nsec =
+    clib_max (bs->effective_desired_min_tx_nsec, bs->remote_min_echo_rx_nsec);
+  BFD_DBG ("Recalculated echo transmit interval " BFD_CLK_FMT,
+          BFD_CLK_PRN (bs->echo_transmit_interval_nsec));
 }
 
 static void
 bfd_calc_next_tx (bfd_main_t * bm, bfd_session_t * bs, u64 now)
 {
-  if (!bs->local_demand)
+  if (bs->local_detect_mult > 1)
     {
-      if (bs->local_detect_mult > 1)
+      /* common case - 75-100% of transmit interval */
+      bs->tx_timeout_nsec = bs->last_tx_nsec +
+       (1 - .25 * (random_f64 (&bm->random_seed))) *
+       bs->transmit_interval_nsec;
+      if (bs->tx_timeout_nsec < now)
        {
-         /* common case - 75-100% of transmit interval */
-         bs->tx_timeout_clocks = now +
-           (1 - .25 * (random_f64 (&bm->random_seed))) *
-           bs->transmit_interval_clocks;
-         if (bs->tx_timeout_clocks < now)
-           {
-             /* huh, we've missed it already, skip the missed events */
-             const u64 missed =
-               (now - bs->tx_timeout_clocks) / bs->transmit_interval_clocks;
-             BFD_ERR ("Missed %lu transmit events (now is %lu, calc "
-                      "tx_timeout is %lu)!",
-                      missed, now, bs->tx_timeout_clocks);
-             bs->tx_timeout_clocks +=
-               (missed + 1) * bs->transmit_interval_clocks;
-           }
+         /*
+          * 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_nsec) /
+                  bs->transmit_interval_nsec, now, bs->tx_timeout_nsec);
+         bs->tx_timeout_nsec = now;
        }
-      else
+    }
+  else
+    {
+      /* special case - 75-90% of transmit interval */
+      bs->tx_timeout_nsec = bs->last_tx_nsec +
+       (.9 - .15 * (random_f64 (&bm->random_seed))) *
+       bs->transmit_interval_nsec;
+      if (bs->tx_timeout_nsec < now)
        {
-         /* special case - 75-90% of transmit interval */
-         bs->tx_timeout_clocks =
-           now +
-           (.9 - .15 * (random_f64 (&bm->random_seed))) *
-           bs->transmit_interval_clocks;
-         if (bs->tx_timeout_clocks < now)
-           {
-             /* huh, we've missed it already, skip the missed events */
-             const u64 missed =
-               (now - bs->tx_timeout_clocks) / bs->transmit_interval_clocks;
-             BFD_ERR ("Missed %lu transmit events (now is %lu, calc "
-                      "tx_timeout is %lu)!",
-                      missed, now, bs->tx_timeout_clocks);
-             bs->tx_timeout_clocks +=
-               (missed + 1) * bs->transmit_interval_clocks;
-           }
+         /*
+          * 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_nsec) /
+                  bs->transmit_interval_nsec, now, bs->tx_timeout_nsec);
+         bs->tx_timeout_nsec = now;
        }
     }
-  else
+  if (bs->tx_timeout_nsec)
     {
-      /* TODO */
+      BFD_DBG ("Next transmit in %lu nsec/%.02fs@%lu",
+              bs->tx_timeout_nsec - now,
+              (bs->tx_timeout_nsec - now) * SEC_PER_NSEC,
+              bs->tx_timeout_nsec);
     }
-  if (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_nsec =
+    bs->echo_last_tx_nsec + bs->echo_transmit_interval_nsec;
+  if (bs->echo_tx_timeout_nsec < now)
     {
-      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);
+      /* 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_nsec) /
+              bs->echo_transmit_interval_nsec,
+              now, bs->echo_tx_timeout_nsec);
+      bs->echo_tx_timeout_nsec = now;
     }
+  BFD_DBG ("Next echo transmit in %lu nsec/%.02fs@%lu",
+          bs->echo_tx_timeout_nsec - now,
+          (bs->echo_tx_timeout_nsec - now) * SEC_PER_NSEC,
+          bs->echo_tx_timeout_nsec);
 }
 
 static void
 bfd_recalc_detection_time (bfd_main_t * bm, bfd_session_t * bs)
 {
-  if (!bs->local_demand)
+  if (bs->local_state == BFD_STATE_init || bs->local_state == BFD_STATE_up)
     {
-      bs->detection_time_clocks =
+      bs->detection_time_nsec =
        bs->remote_detect_mult *
-       bfd_us_to_clocks (bm, clib_max (bs->required_min_rx_us,
-                                       bs->remote_desired_min_tx_us));
+       clib_max (bs->effective_required_min_rx_nsec,
+                 bs->remote_desired_min_tx_nsec);
+      BFD_DBG ("Recalculated detection time %lu nsec/%.3fs",
+              bs->detection_time_nsec,
+              bs->detection_time_nsec * SEC_PER_NSEC);
     }
-  else
-    {
-      bs->detection_time_clocks =
-       bs->local_detect_mult *
-       bfd_us_to_clocks (bm,
-                         clib_max (bs->desired_min_tx_us,
-                                   bs->remote_min_rx_us));
-    }
-  BFD_DBG ("Recalculated detection time %lu clocks/%.2fs",
-          bs->detection_time_clocks,
-          bs->detection_time_clocks / bm->cpu_cps);
 }
 
 static void
@@ -203,151 +288,206 @@ bfd_set_timer (bfd_main_t * bm, bfd_session_t * bs, u64 now,
 {
   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;
+      rx_timeout = bs->last_rx_nsec + bs->detection_time_nsec;
+    }
+  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_nsec;
     }
-  if (bs->tx_timeout_clocks && rx_timeout)
+  if (tx_timeout && rx_timeout)
     {
-      next = clib_min (bs->tx_timeout_clocks, rx_timeout);
+      next = clib_min (tx_timeout, rx_timeout);
     }
-  else if (bs->tx_timeout_clocks)
+  else if (tx_timeout)
     {
-      next = bs->tx_timeout_clocks;
+      next = tx_timeout;
     }
   else if (rx_timeout)
     {
       next = rx_timeout;
     }
-  BFD_DBG ("bs_idx=%u, tx_timeout=%lu, rx_timeout=%lu, next=%s", bs->bs_idx,
-          bs->tx_timeout_clocks, rx_timeout,
-          next == bs->tx_timeout_clocks ? "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 (bs->echo && next > bs->echo_tx_timeout_nsec)
+    {
+      next = bs->echo_tx_timeout_nsec;
+    }
+  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_nsec, rx_timeout,
+          next == tx_timeout
+          ? "tx" : (next == bs->echo_tx_timeout_nsec ? "echo tx" : "rx"));
+  if (next)
+    {
+      int send_signal = 0;
+      bs->event_time_nsec = next;
+      /* add extra tick if it's not even */
+      u32 wheel_time_ticks =
+       (bs->event_time_nsec - now) / bm->nsec_per_tw_tick +
+       ((bs->event_time_nsec - now) % bm->nsec_per_tw_tick != 0);
+      BFD_DBG ("event_time_nsec %lu (%lu nsec/%.3fs in future) -> "
+              "wheel_time_ticks %u", bs->event_time_nsec,
+              bs->event_time_nsec - now,
+              (bs->event_time_nsec - now) * SEC_PER_NSEC, wheel_time_ticks);
+      bfd_lock (bm);
+      if (bs->tw_id)
+       {
+         TW (tw_timer_update) (&bm->wheel, bs->tw_id, wheel_time_ticks);
+         BFD_DBG ("tw_timer_update(%p, %u, %lu);", &bm->wheel, bs->tw_id,
+                  wheel_time_ticks);
+       }
+      else
+       {
+         bs->tw_id =
+           TW (tw_timer_start) (&bm->wheel, bs->bs_idx, 0, wheel_time_ticks);
+         BFD_DBG ("tw_timer_start(%p, %u, 0, %lu) == %u;", &bm->wheel,
+                  bs->bs_idx, wheel_time_ticks);
+       }
+
       if (!handling_wakeup)
        {
-         vlib_process_signal_event (bm->vlib_main,
-                                    bm->bfd_process_node_index,
-                                    BFD_EVENT_RESCHEDULE, bs->bs_idx);
+
+         /* Send only if it is earlier than current awaited wakeup time */
+         send_signal =
+           (bs->event_time_nsec < bm->bfd_process_next_wakeup_nsec) &&
+           /*
+            * If the wake-up time is within 2x the delay of the event propagation delay,
+            * avoid the expense of sending the event. The 2x multiplier is to workaround the race whereby
+            * simultaneous event + expired timer create one recurring bogus wakeup/suspend instance,
+            * due to double scheduling of the node on the pending list.
+            */
+           (bm->bfd_process_next_wakeup_nsec - bs->event_time_nsec >
+            2 * bm->bfd_process_wakeup_event_delay_nsec) &&
+           /* Must be no events in flight to send an event */
+           (!bm->bfd_process_wakeup_events_in_flight);
+
+         /* If we do send the signal, note this down along with the start timestamp */
+         if (send_signal)
+           {
+             bm->bfd_process_wakeup_events_in_flight++;
+             bm->bfd_process_wakeup_event_start_nsec = now;
+           }
+       }
+      bfd_unlock (bm);
+
+      /* Use the multithreaded event sending so the workers can send events too */
+      if (send_signal)
+       {
+         vlib_process_signal_event_mt (bm->vlib_main,
+                                       bm->bfd_process_node_index,
+                                       BFD_EVENT_RESCHEDULE, ~0);
        }
     }
 }
 
 static void
-bfd_set_desired_min_tx (bfd_main_t * bm, bfd_session_t * bs, u64 now,
-                       u32 desired_min_tx_us, int handling_wakeup)
-{
-  bs->desired_min_tx_us = desired_min_tx_us;
-  bs->desired_min_tx_clocks = bfd_us_to_clocks (bm, bs->desired_min_tx_us);
-  BFD_DBG ("Set desired min tx to %uus/%lu clocks/%.2fs",
-          bs->desired_min_tx_us, bs->desired_min_tx_clocks,
-          bs->desired_min_tx_clocks / bm->cpu_cps);
+bfd_set_effective_desired_min_tx (bfd_main_t * bm,
+                                 bfd_session_t * bs, u64 now,
+                                 u64 desired_min_tx_nsec)
+{
+  bs->effective_desired_min_tx_nsec = desired_min_tx_nsec;
+  BFD_DBG ("Set effective desired min tx to " BFD_CLK_FMT,
+          BFD_CLK_PRN (bs->effective_desired_min_tx_nsec));
   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);
-  bfd_set_timer (bm, bs, now, handling_wakeup);
 }
 
 static void
-bfd_set_remote_required_min_rx (bfd_main_t * bm, bfd_session_t * bs,
-                               u64 now,
-                               u32 remote_required_min_rx_us,
-                               int handling_wakeup)
-{
-  bs->remote_min_rx_us = remote_required_min_rx_us;
-  bs->remote_min_rx_clocks = bfd_us_to_clocks (bm, bs->remote_min_rx_us);
-  BFD_DBG ("Set remote min rx to %uus/%lu clocks/%.2fs", bs->remote_min_rx_us,
-          bs->remote_min_rx_clocks, bs->remote_min_rx_clocks / bm->cpu_cps);
+bfd_set_effective_required_min_rx (bfd_main_t * bm,
+                                  bfd_session_t * bs,
+                                  u64 required_min_rx_nsec)
+{
+  bs->effective_required_min_rx_nsec = required_min_rx_nsec;
+  BFD_DBG ("Set effective required min rx to " BFD_CLK_FMT,
+          BFD_CLK_PRN (bs->effective_required_min_rx_nsec));
   bfd_recalc_detection_time (bm, bs);
-  bfd_recalc_tx_interval (bm, bs);
-  bfd_calc_next_tx (bm, bs, now);
-  bfd_set_timer (bm, bs, now, handling_wakeup);
 }
 
-void
-bfd_session_start (bfd_main_t * bm, bfd_session_t * 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)
 {
-  BFD_DBG ("%U", format_bfd_session, bs);
-  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);
+  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_nsec = bfd_usec_to_nsec (remote_required_min_rx_usec);
+      BFD_DBG ("Set remote min rx to " BFD_CLK_FMT,
+              BFD_CLK_PRN (bs->remote_min_rx_nsec));
+      bfd_recalc_detection_time (bm, bs);
+      bfd_recalc_tx_interval (bm, bs);
+    }
 }
 
-vnet_api_error_t
-bfd_del_session (uword bs_idx)
+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)
 {
-  const bfd_main_t *bm = &bfd_main;
-  if (!pool_is_free_index (bm->sessions, bs_idx))
-    {
-      bfd_session_t *bs = pool_elt_at_index (bm->sessions, bs_idx);
-      pool_put (bm->sessions, bs);
-      return 0;
-    }
-  else
+  if (bs->remote_min_echo_rx_usec != remote_required_min_echo_rx_usec)
     {
-      BFD_ERR ("no such session");
-      return VNET_API_ERROR_BFD_NOENT;
+      bs->remote_min_echo_rx_usec = remote_required_min_echo_rx_usec;
+      bs->remote_min_echo_rx_nsec =
+       bfd_usec_to_nsec (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_nsec));
+      bfd_recalc_echo_tx_interval (bm, bs);
     }
-  return 0;
 }
 
-const char *
-bfd_diag_code_string (bfd_diag_code_e diag)
+static void
+bfd_notify_listeners (bfd_main_t * bm,
+                     bfd_listen_event_e event, const bfd_session_t * bs)
 {
-#define F(n, t, s)             \
-  case BFD_DIAG_CODE_NAME (t): \
-    return s;
-  switch (diag)
-    {
-    foreach_bfd_diag_code (F)}
-  return "UNKNOWN";
-#undef F
+  bfd_notify_fn_t *fn;
+  vec_foreach (fn, bm->listeners)
+  {
+    (*fn) (event, bs);
+  }
 }
 
-const char *
-bfd_state_string (bfd_state_e state)
+void
+bfd_session_start (bfd_main_t * bm, bfd_session_t * bs)
 {
-#define F(n, t, s)         \
-  case BFD_STATE_NAME (t): \
-    return s;
-  switch (state)
-    {
-    foreach_bfd_state (F)}
-  return "UNKNOWN";
-#undef F
+  BFD_DBG ("\nStarting session: %U", format_bfd_session, bs);
+  vlib_log_info (bm->log_class, "start BFD session: %U",
+                format_bfd_session_brief, bs);
+  bfd_set_effective_required_min_rx (bm, bs, bs->config_required_min_rx_nsec);
+  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);
 }
 
-vnet_api_error_t
-bfd_session_set_flags (u32 bs_idx, u8 admin_up_down)
+void
+bfd_session_set_flags (vlib_main_t * vm, bfd_session_t * bs, u8 admin_up_down)
 {
   bfd_main_t *bm = &bfd_main;
-  if (pool_is_free_index (bm->sessions, bs_idx))
-    {
-      BFD_ERR ("invalid bs_idx=%u", bs_idx);
-      return VNET_API_ERROR_BFD_NOENT;
-    }
-  bfd_session_t *bs = pool_elt_at_index (bm->sessions, bs_idx);
+  u64 now = bfd_time_now_nsec (vm, NULL);
   if (admin_up_down)
     {
-      bfd_set_state (bm, bs, BFD_STATE_down, 0);
+      BFD_DBG ("Session set admin-up, bs-idx=%u", bs->bs_idx);
+      vlib_log_info (bm->log_class, "set session admin-up: %U",
+                    format_bfd_session_brief, bs);
+      bfd_set_state (vm, 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_set_diag (bs, BFD_DIAG_CODE_neighbor_sig_down);
-      bfd_set_state (bm, bs, BFD_STATE_admin_down, 0);
+      BFD_DBG ("Session set admin-down, bs-idx=%u", bs->bs_idx);
+      vlib_log_info (bm->log_class, "set session admin-down: %U",
+                    format_bfd_session_brief, bs);
+      bfd_set_diag (bs, BFD_DIAG_CODE_admin_down);
+      bfd_set_state (vm, bm, bs, BFD_STATE_admin_down, 0);
+      bfd_calc_next_tx (bm, bs, now);
+      bfd_set_timer (bm, bs, now, 0);
     }
-  return 0;
 }
 
 u8 *
@@ -360,8 +500,8 @@ bfd_input_format_trace (u8 * s, va_list * args)
   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",
+                 "    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),
@@ -371,186 +511,586 @@ bfd_input_format_trace (u8 * s, va_list * args)
                  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))
+      if (t->len >= sizeof (bfd_pkt_t) &&
+         pkt->head.length >= sizeof (bfd_pkt_t))
        {
-         s = format (s, "    my discriminator: %u\n", pkt->my_disc);
-         s = format (s, "    your discriminator: %u\n", pkt->your_disc);
+         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\n",
+         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;
 }
 
+typedef struct
+{
+  u32 bs_idx;
+} bfd_rpc_event_t;
+
+static void
+bfd_rpc_event_cb (const bfd_rpc_event_t * a)
+{
+  bfd_main_t *bm = &bfd_main;
+  u32 bs_idx = a->bs_idx;
+  u32 valid_bs = 0;
+  bfd_session_t session_data;
+
+  bfd_lock (bm);
+  if (!pool_is_free_index (bm->sessions, bs_idx))
+    {
+      bfd_session_t *bs = pool_elt_at_index (bm->sessions, bs_idx);
+      clib_memcpy (&session_data, bs, sizeof (bfd_session_t));
+      valid_bs = 1;
+    }
+  else
+    {
+      BFD_DBG ("Ignoring event RPC for non-existent session index %u",
+              bs_idx);
+    }
+  bfd_unlock (bm);
+
+  if (valid_bs)
+    bfd_event (bm, &session_data);
+}
+
+static void
+bfd_event_rpc (u32 bs_idx)
+{
+  const u32 data_size = sizeof (bfd_rpc_event_t);
+  u8 data[data_size];
+  bfd_rpc_event_t *event = (bfd_rpc_event_t *) data;
+
+  event->bs_idx = bs_idx;
+  vl_api_rpc_call_main_thread (bfd_rpc_event_cb, data, data_size);
+}
+
+typedef struct
+{
+  u32 bs_idx;
+} bfd_rpc_notify_listeners_t;
+
+static void
+bfd_rpc_notify_listeners_cb (const bfd_rpc_notify_listeners_t * a)
+{
+  bfd_main_t *bm = &bfd_main;
+  u32 bs_idx = a->bs_idx;
+  bfd_lock (bm);
+  if (!pool_is_free_index (bm->sessions, bs_idx))
+    {
+      bfd_session_t *bs = pool_elt_at_index (bm->sessions, bs_idx);
+      bfd_notify_listeners (bm, BFD_LISTEN_EVENT_UPDATE, bs);
+    }
+  else
+    {
+      BFD_DBG ("Ignoring notify RPC for non-existent session index %u",
+              bs_idx);
+    }
+  bfd_unlock (bm);
+}
+
+static void
+bfd_notify_listeners_rpc (u32 bs_idx)
+{
+  const u32 data_size = sizeof (bfd_rpc_notify_listeners_t);
+  u8 data[data_size];
+  bfd_rpc_notify_listeners_t *notify = (bfd_rpc_notify_listeners_t *) data;
+  notify->bs_idx = bs_idx;
+  vl_api_rpc_call_main_thread (bfd_rpc_notify_listeners_cb, data, data_size);
+}
+
 static void
 bfd_on_state_change (bfd_main_t * bm, bfd_session_t * bs, u64 now,
                     int handling_wakeup)
 {
-  BFD_DBG ("State changed: %U", format_bfd_session, bs);
-  bfd_event (bm, bs);
+  BFD_DBG ("\nState changed: %U", format_bfd_session, bs);
+
+  if (vlib_get_thread_index () == 0)
+    {
+      bfd_event (bm, bs);
+    }
+  else
+    {
+      /* without RPC - a REGRESSION: BFD event are not propagated */
+      bfd_event_rpc (bs->bs_idx);
+    }
+
   switch (bs->local_state)
     {
     case BFD_STATE_admin_down:
-      bfd_set_desired_min_tx (bm, bs, now,
-                             clib_max (bs->config_desired_min_tx_us,
-                                       BFD_DEFAULT_DESIRED_MIN_TX_US),
-                             handling_wakeup);
+      bs->echo = 0;
+      bfd_set_effective_desired_min_tx (bm, bs, now,
+                                       clib_max
+                                       (bs->config_desired_min_tx_nsec,
+                                        bm->default_desired_min_tx_nsec));
+      bfd_set_effective_required_min_rx (bm, bs,
+                                        bs->config_required_min_rx_nsec);
+      bfd_set_timer (bm, bs, now, handling_wakeup);
       break;
     case BFD_STATE_down:
-      bfd_set_desired_min_tx (bm, bs, now,
-                             clib_max (bs->config_desired_min_tx_us,
-                                       BFD_DEFAULT_DESIRED_MIN_TX_US),
-                             handling_wakeup);
+      bs->echo = 0;
+      bfd_set_effective_desired_min_tx (bm, bs, now,
+                                       clib_max
+                                       (bs->config_desired_min_tx_nsec,
+                                        bm->default_desired_min_tx_nsec));
+      bfd_set_effective_required_min_rx (bm, bs,
+                                        bs->config_required_min_rx_nsec);
+      bfd_set_timer (bm, bs, now, handling_wakeup);
       break;
     case BFD_STATE_init:
-      bfd_set_desired_min_tx (bm, bs, now,
-                             clib_max (bs->config_desired_min_tx_us,
-                                       BFD_DEFAULT_DESIRED_MIN_TX_US),
-                             handling_wakeup);
+      bs->echo = 0;
+      bfd_set_effective_desired_min_tx (bm, bs, now,
+                                       bs->config_desired_min_tx_nsec);
+      bfd_set_timer (bm, bs, now, handling_wakeup);
       break;
     case BFD_STATE_up:
-      bfd_set_desired_min_tx (bm, bs, now, bs->config_desired_min_tx_us,
-                             handling_wakeup);
+      bfd_set_effective_desired_min_tx (bm, bs, now,
+                                       bs->config_desired_min_tx_nsec);
+      if (BFD_POLL_NOT_NEEDED == bs->poll_state)
+       {
+         bfd_set_effective_required_min_rx (bm, bs,
+                                            bs->config_required_min_rx_nsec);
+       }
+      bfd_set_timer (bm, bs, now, handling_wakeup);
       break;
     }
+  if (vlib_get_thread_index () == 0)
+    {
+      bfd_notify_listeners (bm, BFD_LISTEN_EVENT_UPDATE, bs);
+    }
+  else
+    {
+      /* without RPC - a REGRESSION: state changes are not propagated */
+      bfd_notify_listeners_rpc (bs->bs_idx);
+    }
+}
+
+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_nsec < now)
+    {
+      bs->tx_timeout_nsec = now;
+    }
+  bfd_recalc_detection_time (bm, bs);
+  bfd_set_timer (bm, bs, now, 0);
 }
 
 static void
-bfd_add_transport_layer (vlib_main_t * vm, vlib_buffer_t * b,
-                        bfd_session_t * bs)
+bfd_add_transport_layer (vlib_main_t * vm, u32 bi, bfd_session_t * bs)
 {
   switch (bs->transport)
     {
     case BFD_TRANSPORT_UDP4:
-      /* fallthrough */
+      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 udp, bs_idx=%u", bs->bs_idx);
-      bfd_add_udp_transport (vm, b, &bs->udp);
+      BFD_DBG ("Transport bfd via udp6, bs_idx=%u", bs->bs_idx);
+      bfd_add_udp6_transport (vm, bi, bs, 0 /* is_echo */ );
       break;
     }
 }
 
-static vlib_buffer_t *
-bfd_create_frame (vlib_main_t * vm, vlib_node_runtime_t * rt,
-                 bfd_session_t * bs)
+static int
+bfd_transport_control_frame (vlib_main_t * vm, u32 bi, bfd_session_t * bs)
 {
-  u32 bi;
-  if (vlib_buffer_alloc (vm, &bi, 1) != 1)
+  switch (bs->transport)
     {
-      clib_warning ("buffer allocation failure");
-      return NULL;
+    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;
+}
 
-  vlib_buffer_t *b = vlib_get_buffer (vm, bi);
-  ASSERT (b->current_data == 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;
+}
 
-  u32 *to_next;
-  u32 n_left_to_next;
+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;
+}
 
-  vlib_get_next_frame (vm, rt, bfd_next_index_by_transport[bs->transport],
-                      to_next, n_left_to_next);
+#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);
+  clib_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
 
-  to_next[0] = bi;
-  n_left_to_next -= 1;
+static void
+bfd_add_auth_section (vlib_buffer_t * b, bfd_session_t * bs)
+{
+  bfd_main_t *bm = &bfd_main;
+  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:
+         vlib_log_crit (bm->log_class,
+                        "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:
+         vlib_log_crit (bm->log_class,
+                        "internal error, unexpected BFD auth type '%d'",
+                        auth_type);
+         break;
+#endif
+       }
+    }
+}
 
-  vlib_put_next_frame (vm, rt, bfd_next_index_by_transport[bs->transport],
-                      n_left_to_next);
-  return b;
+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 (vlib_buffer_t * b, bfd_session_t * bs)
+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);
-  const u32 bfd_length = 24;
-  memset (pkt, 0, sizeof (*pkt));
-
+  u32 bfd_length = 0;
+  bfd_length = sizeof (bfd_pkt_t);
+  clib_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);
-  if (bs->local_demand && BFD_STATE_up == bs->local_state &&
-      BFD_STATE_up == bs->remote_state)
-    {
-      bfd_pkt_set_demand (pkt);
-    }
   pkt->head.detect_mult = bs->local_detect_mult;
-  pkt->head.length = clib_host_to_net_u32 (bfd_length);
+  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->desired_min_tx_us);
-  pkt->req_min_rx = clib_host_to_net_u32 (bs->required_min_rx_us);
-  pkt->req_min_echo_rx = clib_host_to_net_u32 (0);     /* FIXME */
+  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_nsec_to_usec
+                             (bs->effective_required_min_rx_nsec));
+    }
+  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_periodic (vlib_main_t * vm, vlib_node_runtime_t * rt,
-                  bfd_main_t * bm, bfd_session_t * bs, u64 now,
-                  int handling_wakeup)
+bfd_send_echo (vlib_main_t * vm, vlib_node_runtime_t * rt,
+              bfd_main_t * bm, bfd_session_t * bs, u64 now)
 {
-  if (!bs->remote_min_rx_us)
+  if (!bfd_is_echo_possible (bs))
     {
-      BFD_DBG
-       ("bfd.RemoteMinRxInterval is zero, not sending periodic control "
-        "frame");
+      BFD_DBG ("\nSwitching off echo function: %U", format_bfd_session, bs);
+      bs->echo = 0;
       return;
     }
-  /* FIXME
-     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.
-   */
-  /* sometimes the wheel expires an event a bit sooner than requested, account
-     for that here */
-  if (now + bm->wheel_inaccuracy >= bs->tx_timeout_clocks)
+  if (now >= bs->echo_tx_timeout_nsec)
     {
-      BFD_DBG ("Send periodic control frame for bs_idx=%lu", bs->bs_idx);
-      vlib_buffer_t *b = bfd_create_frame (vm, rt, bs);
-      if (!b)
+      BFD_DBG ("\nSending echo packet: %U", format_bfd_session, bs);
+      u32 bi;
+      if (vlib_buffer_alloc (vm, &bi, 1) != 1)
+       {
+         vlib_log_crit (bm->log_class, "buffer allocation failure");
+         return;
+       }
+      vlib_buffer_t *b = vlib_get_buffer (vm, bi);
+      ASSERT (b->current_data == 0);
+      VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b);
+      bfd_echo_pkt_t *pkt = vlib_buffer_get_current (b);
+      clib_memset (pkt, 0, sizeof (*pkt));
+      pkt->discriminator = bs->local_discr;
+      pkt->expire_time_nsec =
+       now + bs->echo_transmit_interval_nsec * bs->local_detect_mult;
+      pkt->checksum =
+       bfd_calc_echo_checksum (bs->local_discr, pkt->expire_time_nsec,
+                               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;
        }
-      bfd_init_control_frame (b, bs);
-      bfd_add_transport_layer (vm, b, bs);
+      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_nsec = 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_nsec);
+    }
+}
+
+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;
+    }
+  if (now >= bs->tx_timeout_nsec)
+    {
+      BFD_DBG ("\nSending periodic control frame: %U", format_bfd_session,
+              bs);
+      u32 bi;
+      if (vlib_buffer_alloc (vm, &bi, 1) != 1)
+       {
+         vlib_log_crit (bm->log_class, "buffer allocation failure");
+         return;
+       }
+      vlib_buffer_t *b = vlib_get_buffer (vm, bi);
+      ASSERT (b->current_data == 0);
+      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_nsec)
+           {
+             BFD_DBG ("Cannot start a poll sequence yet, need to wait for "
+                      BFD_CLK_FMT,
+                      BFD_CLK_PRN (bs->poll_state_start_or_timeout_nsec -
+                                   now));
+             break;
+           }
+         bs->poll_state_start_or_timeout_nsec = 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_nsec = 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);
+        now, bs->tx_timeout_nsec);
     }
-  bfd_set_timer (bm, bs, now, handling_wakeup);
 }
 
 void
-bfd_send_final (vlib_main_t * vm, vlib_buffer_t * b, bfd_session_t * bs)
+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 (b, bs);
+  bfd_init_control_frame (bm, bs, b);
   bfd_pkt_set_final (vlib_buffer_get_current (b));
-  bfd_add_transport_layer (vm, b, bs);
+  bfd_add_auth_section (b, bs);
+  u32 bi = vlib_get_buffer_index (vm, b);
+  bfd_add_transport_layer (vm, bi, bs);
+  bs->last_tx_nsec = bfd_time_now_nsec (vm, NULL);
+  /*
+   * 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)
+bfd_check_rx_timeout (vlib_main_t * vm, 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)
+  if (bs->last_rx_nsec + bs->detection_time_nsec <= now)
     {
       BFD_DBG ("Rx timeout, session goes down");
+      /*
+       * RFC 5880 6.8.1. State Variables
+
+       * bfd.RemoteDiscr
+
+       * The remote discriminator for this BFD session.  This is the
+       * discriminator chosen by the remote system, and is totally opaque
+       * to the local system.  This MUST be initialized to zero.  If a
+       * period of a Detection Time passes without the receipt of a valid,
+       * authenticated BFD packet from the remote system, this variable
+       * MUST be set to zero.
+       */
+      bs->remote_discr = 0;
       bfd_set_diag (bs, BFD_DIAG_CODE_det_time_exp);
-      bfd_set_state (bm, bs, BFD_STATE_down, handling_wakeup);
+      bfd_set_state (vm, 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_nsec +
+          bs->echo_transmit_interval_nsec * bs->local_detect_mult <= now)
+    {
+      BFD_DBG ("Echo rx timeout, session goes down");
+      bfd_set_diag (bs, BFD_DIAG_CODE_echo_failed);
+      bfd_set_state (vm, bm, bs, BFD_STATE_down, handling_wakeup);
     }
 }
 
@@ -562,21 +1102,36 @@ bfd_on_timeout (vlib_main_t * vm, vlib_node_runtime_t * rt, bfd_main_t * bm,
   switch (bs->local_state)
     {
     case BFD_STATE_admin_down:
-      BFD_ERR ("Unexpected timeout when in %s state",
-              bfd_state_string (bs->local_state));
-      abort ();
+      bfd_send_periodic (vm, rt, bm, bs, now);
       break;
     case BFD_STATE_down:
-      bfd_send_periodic (vm, rt, bm, bs, now, 1);
+      bfd_send_periodic (vm, rt, bm, bs, now);
       break;
     case BFD_STATE_init:
-      BFD_ERR ("Unexpected timeout when in %s state",
-              bfd_state_string (bs->local_state));
-      abort ();
+      bfd_check_rx_timeout (vm, 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);
-      bfd_send_periodic (vm, rt, bm, bs, now, 1);
+      bfd_check_rx_timeout (vm, 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_nsec = now;
+         bs->echo_tx_timeout_nsec = now;
+         bfd_set_effective_required_min_rx (bm, bs,
+                                            clib_max
+                                            (bm->min_required_min_rx_while_echo_nsec,
+                                             bs->config_required_min_rx_nsec));
+         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;
     }
 }
@@ -596,58 +1151,109 @@ bfd_process (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
 
   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)
+      f64 vm_time;
+      u64 now = bfd_time_now_nsec (vm, &vm_time);
+      BFD_DBG ("wakeup, now is %llunsec, vlib_time_now() is %.9f", now,
+              vm_time);
+      bfd_lock (bm);
+      f64 timeout;
+      if (pool_elts (bm->sessions))
        {
-         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)
+         u32 first_expires_in_ticks =
+           TW (tw_timer_first_expires_in_ticks) (&bm->wheel);
+         if (!first_expires_in_ticks)
            {
-             BFD_DBG ("negative timeout, already expired, skipping wait");
-             event_type = ~0;
+             BFD_DBG
+               ("tw_timer_first_expires_in_ticks(%p) returns 0ticks",
+                &bm->wheel);
+             timeout = bm->wheel.next_run_time - vm_time;
+             BFD_DBG ("wheel.next_run_time is %.9f",
+                      bm->wheel.next_run_time);
+             u64 next_expire_nsec = now + timeout * SEC_PER_NSEC;
+             bm->bfd_process_next_wakeup_nsec = next_expire_nsec;
+             bfd_unlock (bm);
            }
          else
            {
-             (void) vlib_process_wait_for_event_or_clock (vm, timeout);
-             event_type = vlib_process_get_events (vm, &event_data);
+             BFD_DBG ("tw_timer_first_expires_in_ticks(%p) returns %luticks",
+                      &bm->wheel, first_expires_in_ticks);
+             u64 next_expire_nsec =
+               now + first_expires_in_ticks * bm->nsec_per_tw_tick;
+             bm->bfd_process_next_wakeup_nsec = next_expire_nsec;
+             bfd_unlock (bm);
+             timeout = (next_expire_nsec - now) * SEC_PER_NSEC;
            }
+         BFD_DBG ("vlib_process_wait_for_event_or_clock(vm, %.09f)",
+                  timeout);
+         (void) vlib_process_wait_for_event_or_clock (vm, timeout);
+       }
+      else
+       {
+         (void) vlib_process_wait_for_event (vm);
        }
-      now = clib_cpu_time_now ();
+      event_type = vlib_process_get_events (vm, &event_data);
+      now = bfd_time_now_nsec (vm, &vm_time);
+      uword *session_index;
       switch (event_type)
        {
        case ~0:                /* no events => timeout */
          /* nothing to do here */
          break;
        case BFD_EVENT_RESCHEDULE:
+         BFD_DBG ("reschedule event");
+         bfd_lock (bm);
+         bm->bfd_process_wakeup_event_delay_nsec =
+           now - bm->bfd_process_wakeup_event_start_nsec;
+         bm->bfd_process_wakeup_events_in_flight--;
+         bfd_unlock (bm);
          /* nothing to do here - reschedule is done automatically after
           * each event or timeout */
          break;
        case BFD_EVENT_NEW_SESSION:
-         do
-           {
-             bfd_session_t *bs =
-               pool_elt_at_index (bm->sessions, *event_data);
-             bfd_send_periodic (vm, rt, bm, bs, now, 1);
-           }
-         while (0);
+         vec_foreach (session_index, event_data)
+         {
+           bfd_lock (bm);
+           if (!pool_is_free_index (bm->sessions, *session_index))
+             {
+               bfd_session_t *bs =
+                 pool_elt_at_index (bm->sessions, *session_index);
+               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) * session_index);
+             }
+           bfd_unlock (bm);
+         }
+         break;
+       case BFD_EVENT_CONFIG_CHANGED:
+         vec_foreach (session_index, event_data)
+         {
+           bfd_lock (bm);
+           if (!pool_is_free_index (bm->sessions, *session_index))
+             {
+               bfd_session_t *bs =
+                 pool_elt_at_index (bm->sessions, *session_index);
+               bfd_on_config_change (vm, rt, bm, bs, now);
+             }
+           else
+             {
+               BFD_DBG ("Ignoring event for non-existent session index %u",
+                        (u32) * session_index);
+             }
+           bfd_unlock (bm);
+         }
          break;
        default:
-         clib_warning ("BUG: event type 0x%wx", event_type);
+         vlib_log_err (bm->log_class, "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 ("tw_timer_expire_timers_vec(%p, %.04f);", &bm->wheel, vm_time);
+      bfd_lock (bm);
+      expired =
+       TW (tw_timer_expire_timers_vec) (&bm->wheel, vm_time, expired);
       BFD_DBG ("Expired %d elements", vec_len (expired));
       u32 *p = NULL;
       vec_foreach (p, expired)
@@ -656,9 +1262,12 @@ bfd_process (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
        if (!pool_is_free_index (bm->sessions, bs_idx))
          {
            bfd_session_t *bs = pool_elt_at_index (bm->sessions, bs_idx);
+           bs->tw_id = 0;      /* timer is gone because it expired */
            bfd_on_timeout (vm, rt, bm, bs, now);
+           bfd_set_timer (bm, bs, now, 1);
          }
       }
+      bfd_unlock (bm);
       if (expired)
        {
          _vec_len (expired) = 0;
@@ -680,13 +1289,8 @@ VLIB_REGISTER_NODE (bfd_process_node, static) = {
   .function = bfd_process,
   .type = VLIB_NODE_TYPE_PROCESS,
   .name = "bfd-process",
-  .n_next_nodes = BFD_OUTPUT_N_NEXT,
-  .next_nodes =
-      {
-#define F(t, n) [BFD_OUTPUT_##t] = n,
-          foreach_bfd_transport (F)
-#undef F
-      },
+  .n_next_nodes = 0,
+  .next_nodes = {},
 };
 /* *INDENT-ON* */
 
@@ -717,52 +1321,107 @@ bfd_hw_interface_up_down (vnet_main_t * vnm, u32 hw_if_index, u32 flags)
 
 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)
 {
+  vlib_thread_main_t *tm = &vlib_thread_main;
+  u32 n_vlib_mains = tm->n_vlib_mains;
+#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 = 2590000000;    // vm->clib_time.clocks_per_second;
-  BFD_DBG ("cps is %.2f", bm->cpu_cps);
-  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;
-
+  clib_memset (&bm->wheel, 0, sizeof (bm->wheel));
+  bm->nsec_per_tw_tick = (f64) NSEC_PER_SEC / BFD_TW_TPS;
+  bm->default_desired_min_tx_nsec =
+    bfd_usec_to_nsec (BFD_DEFAULT_DESIRED_MIN_TX_USEC);
+  bm->min_required_min_rx_while_echo_nsec =
+    bfd_usec_to_nsec (BFD_REQUIRED_MIN_RX_USEC_WHILE_ECHO);
+  BFD_DBG ("tw_timer_wheel_init(%p, %p, %.04f, %u)", &bm->wheel, NULL,
+          1.00 / BFD_TW_TPS, ~0);
+  TW (tw_timer_wheel_init) (&bm->wheel, NULL, 1.00 / BFD_TW_TPS, ~0);
+  bm->log_class = vlib_log_register_class ("bfd", 0);
+  vlib_log_debug (bm->log_class, "initialized");
+  bm->owner_thread_index = ~0;
+  if (n_vlib_mains > 1)
+    clib_spinlock_init (&bm->lock);
   return 0;
 }
 
 VLIB_INIT_FUNCTION (bfd_main_init);
 
 bfd_session_t *
-bfd_get_session (bfd_main_t * bm, bfd_transport_t t)
+bfd_get_session (bfd_main_t * bm, bfd_transport_e t)
 {
   bfd_session_t *result;
+
+  bfd_lock (bm);
+
   pool_get (bm->sessions, result);
-  memset (result, 0, sizeof (*result));
+  clib_memset (result, 0, sizeof (*result));
   result->bs_idx = result - bm->sessions;
   result->transport = t;
-  result->local_discr = random_u32 (&bm->random_seed);
+  const unsigned limit = 1000;
+  unsigned counter = 0;
+  do
+    {
+      result->local_discr = random_u32 (&bm->random_seed);
+      if (counter > limit)
+       {
+         vlib_log_crit (bm->log_class,
+                        "couldn't allocate unused session discriminator even "
+                        "after %u tries!", limit);
+         pool_put (bm->sessions, result);
+         bfd_unlock (bm);
+         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);
+  bfd_unlock (bm);
   return result;
 }
 
 void
 bfd_put_session (bfd_main_t * bm, bfd_session_t * bs)
 {
+  bfd_lock (bm);
+
+  vlib_log_info (bm->log_class, "delete session: %U",
+                format_bfd_session_brief, 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_unlock (bm);
 }
 
 bfd_session_t *
 bfd_find_session_by_idx (bfd_main_t * bm, uword bs_idx)
 {
+  bfd_lock_check (bm);
   if (!pool_is_free_index (bm->sessions, bs_idx))
     {
       return pool_elt_at_index (bm->sessions, bs_idx);
@@ -773,6 +1432,7 @@ bfd_find_session_by_idx (bfd_main_t * bm, uword bs_idx)
 bfd_session_t *
 bfd_find_session_by_disc (bfd_main_t * bm, u32 disc)
 {
+  bfd_lock_check (bm);
   uword *p = hash_get (bfd_main.session_by_disc, disc);
   if (p)
     {
@@ -799,7 +1459,7 @@ bfd_verify_pkt_common (const bfd_pkt_t * pkt)
     }
   if (pkt->head.length < sizeof (bfd_pkt_t) ||
       (bfd_pkt_get_auth_present (pkt) &&
-       pkt->head.length < sizeof (bfd_pkt_with_auth_t)))
+       pkt->head.length < sizeof (bfd_pkt_with_common_auth_t)))
     {
       BFD_ERR ("BFD verification failed - unexpected length: '%d' (auth "
               "present: %d)",
@@ -837,6 +1497,230 @@ bfd_verify_pkt_common (const bfd_pkt_t * pkt)
   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 (vlib_main_t * vm, 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 = bfd_time_now_nsec (vm, NULL);
+  if (now - bs->last_rx_nsec > bs->detection_time_nsec * 2)
+    {
+      BFD_DBG ("BFD peer unresponsive for %lu nsec, which is > 2 * "
+              "detection_time=%u nsec, resetting remote_seq_number_known "
+              "flag", now - bs->last_rx_nsec, bs->detection_time_nsec * 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 (vlib_main_t * vm, const bfd_pkt_t * pkt,
+                        u32 pkt_size, bfd_session_t * bs, u8 bfd_key_id,
+                        bfd_auth_key_t * auth_key)
+{
+  bfd_main_t *bm = &bfd_main;
+  switch (auth_key->auth_type)
+    {
+    case BFD_AUTH_TYPE_reserved:
+      vlib_log_err (bm->log_class,
+                   "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:
+      vlib_log_err (bm->log_class,
+                   "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:
+      vlib_log_err
+       (bm->log_class,
+        "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 (vm, 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
+      vlib_log_err
+       (bm->log_class,
+        "internal error, attempt to use SHA1 without SSL support");
+      return 0;
+#endif
+    }
+  return 0;
+}
+
 /**
  * @brief verify bfd packet - authentication
  *
@@ -845,37 +1729,92 @@ bfd_verify_pkt_common (const bfd_pkt_t * pkt)
  * @return 1 if bfd packet is valid
  */
 int
-bfd_verify_pkt_session (const bfd_pkt_t * pkt, u16 pkt_size,
-                       const bfd_session_t * bs)
+bfd_verify_pkt_auth (vlib_main_t * vm, const bfd_pkt_t * pkt, u16 pkt_size,
+                    bfd_session_t * bs)
 {
-  const bfd_pkt_with_auth_t *with_auth = (bfd_pkt_with_auth_t *) pkt;
-  if (!bfd_pkt_get_auth_present (pkt))
+  if (bfd_pkt_get_auth_present (pkt))
     {
-      if (pkt_size > sizeof (*pkt))
+      /* authentication present in packet */
+      if (!bs->auth.curr_key)
        {
-         BFD_ERR ("BFD verification failed - unexpected packet size '%d' "
-                  "(auth not present)", pkt_size);
-         return 0;
+         /* 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 (vm, 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 (vm, 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 (vm, 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
     {
-      if (!with_auth->auth.type)
+      /* authentication in packet not present */
+      if (pkt_size > sizeof (*pkt))
        {
-         BFD_ERR ("BFD verification failed - unexpected auth type: '%d'",
-                  with_auth->auth.type);
+         BFD_ERR ("BFD verification failed - unexpected packet size '%d' "
+                  "(auth not present)", pkt_size);
          return 0;
        }
-      /* TODO FIXME - implement the actual verification */
+      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 1;
+  return 0;
 }
 
 void
-bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
+bfd_consume_pkt (vlib_main_t * vm, bfd_main_t * bm, const bfd_pkt_t * pkt,
+                u32 bs_idx)
 {
+  bfd_lock_check (bm);
+
   bfd_session_t *bs = bfd_find_session_by_idx (bm, bs_idx);
-  if (!bs)
+  if (!bs || (pkt->your_disc && pkt->your_disc != bs->local_discr))
     {
       return;
     }
@@ -883,38 +1822,104 @@ bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
   bs->remote_discr = pkt->my_disc;
   bs->remote_state = bfd_pkt_get_state (pkt);
   bs->remote_demand = bfd_pkt_get_demand (pkt);
-  u64 now = clib_cpu_time_now ();
-  bs->last_rx_clocks = now;
-  bs->remote_desired_min_tx_us = clib_net_to_host_u32 (pkt->des_min_tx);
+  bs->remote_diag = bfd_pkt_get_diag_code (pkt);
+  u64 now = bfd_time_now_nsec (vm, NULL);
+  bs->last_rx_nsec = 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:
+         vlib_log_crit (bm->log_class,
+                        "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_nsec =
+    bfd_usec_to_nsec (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), 0);
-  /* FIXME
-     If the Required Min Echo RX Interval field is zero, the
-     transmission of Echo packets, if any, MUST cease.
-
-     If a Poll Sequence is being transmitted by the local system and
-     the Final (F) bit in the received packet is set, the Poll Sequence
-     MUST be terminated.
-   */
-  /* FIXME 6.8.2 */
-  /* FIXME 6.8.4 */
+                                 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_nsec,
+                                                          bs->config_required_min_rx_nsec));
+           }
+       }
+      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_nsec));
+         bs->poll_state_start_or_timeout_nsec =
+           now + (now - bs->poll_state_start_or_timeout_nsec);
+         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)
-    return;
+    {
+      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);
+      bfd_set_state (vm, bm, bs, BFD_STATE_down, 0);
     }
   else if (BFD_STATE_down == bs->local_state)
     {
       if (BFD_STATE_down == bs->remote_state)
        {
-         bfd_set_state (bm, bs, BFD_STATE_init, 0);
+         bfd_set_diag (bs, BFD_DIAG_CODE_no_diag);
+         bfd_set_state (vm, bm, bs, BFD_STATE_init, 0);
        }
       else if (BFD_STATE_init == bs->remote_state)
        {
-         bfd_set_state (bm, bs, BFD_STATE_up, 0);
+         bfd_set_diag (bs, BFD_DIAG_CODE_no_diag);
+         bfd_set_state (vm, bm, bs, BFD_STATE_up, 0);
        }
     }
   else if (BFD_STATE_init == bs->local_state)
@@ -922,7 +1927,8 @@ bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
       if (BFD_STATE_up == bs->remote_state ||
          BFD_STATE_init == bs->remote_state)
        {
-         bfd_set_state (bm, bs, BFD_STATE_up, 0);
+         bfd_set_diag (bs, BFD_DIAG_CODE_no_diag);
+         bfd_set_state (vm, bm, bs, BFD_STATE_up, 0);
        }
     }
   else                         /* BFD_STATE_up == bs->local_state */
@@ -930,32 +1936,352 @@ bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
       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);
+         bfd_set_state (vm, bm, bs, BFD_STATE_down, 0);
        }
     }
 }
 
+int
+bfd_consume_echo_pkt (vlib_main_t * vm, 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_nsec,
+                           bs->echo_secret);
+  if (checksum != pkt->checksum)
+    {
+      BFD_DBG ("Invalid echo packet, checksum mismatch");
+      return 1;
+    }
+  u64 now = bfd_time_now_nsec (vm, NULL);
+  if (pkt->expire_time_nsec < now)
+    {
+      BFD_DBG ("Stale packet received, expire time %lu < now %lu",
+              pkt->expire_time_nsec, now);
+    }
+  else
+    {
+      bs->echo_last_rx_nsec = now;
+    }
+  return 1;
+}
+
 u8 *
 format_bfd_session (u8 * s, va_list * args)
 {
   const bfd_session_t *bs = va_arg (*args, bfd_session_t *);
-  return format (s, "BFD(%u): bfd.SessionState=%s, "
-                "bfd.RemoteSessionState=%s, "
-                "bfd.LocalDiscr=%u, "
-                "bfd.RemoteDiscr=%u, "
-                "bfd.LocalDiag=%s, "
-                "bfd.DesiredMinTxInterval=%u, "
-                "bfd.RequiredMinRxInterval=%u, "
-                "bfd.RemoteMinRxInterval=%u, "
-                "bfd.DemandMode=%s, "
-                "bfd.RemoteDemandMode=%s, "
-                "bfd.DetectMult=%u, ",
-                bs->bs_idx, bfd_state_string (bs->local_state),
-                bfd_state_string (bs->remote_state), bs->local_discr,
-                bs->remote_discr, bfd_diag_code_string (bs->local_diag),
-                bs->desired_min_tx_us, bs->required_min_rx_us,
-                bs->remote_min_rx_us, (bs->local_demand ? "yes" : "no"),
-                (bs->remote_demand ? "yes" : "no"), bs->local_detect_mult);
+  u32 indent = format_get_indent (s) + vlib_log_get_indent ();
+  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;
+}
+
+u8 *
+format_bfd_session_brief (u8 * s, va_list * args)
+{
+  const bfd_session_t *bs = va_arg (*args, bfd_session_t *);
+  s =
+    format (s, "bs_idx=%u local-state=%s remote-state=%s", bs->bs_idx,
+           bfd_state_string (bs->local_state),
+           bfd_state_string (bs->remote_state));
+  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)
+    {
+      vlib_log_err (bm->log_class,
+                   "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);
+  vlib_log_info (bm->log_class, "session auth modified: %U",
+                format_bfd_session_brief, bs);
+  return 0;
+}
+
+vnet_api_error_t
+bfd_auth_deactivate (bfd_session_t * bs, u8 is_delayed)
+{
+  bfd_main_t *bm = &bfd_main;
+#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);
+  vlib_log_info (bm->log_class, "session auth modified: %U",
+                format_bfd_session_brief, bs);
+  return 0;
+#else
+  vlib_log_err (bm->log_class,
+               "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_nsec = bfd_usec_to_nsec (desired_min_tx_usec);
+      bs->config_required_min_rx_usec = required_min_rx_usec;
+      bs->config_required_min_rx_nsec =
+       bfd_usec_to_nsec (required_min_rx_usec);
+      BFD_DBG ("\nChanged session params: %U", format_bfd_session, bs);
+
+      vlib_log_info (bm->log_class, "changed session params: %U",
+                    format_bfd_session_brief, 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)
+{
+  bfd_main_t *bm = &bfd_main;
+#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))
+    {
+      vlib_log_err (bm->log_class,
+                   "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))
+    {
+      vlib_log_err (bm->log_class, "unsupported auth type=%d:%s", auth_type,
+                   bfd_auth_type_str (auth_type));
+      return VNET_API_ERROR_BFD_NOTSUPP;
+    }
+  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)
+       {
+         vlib_log_err (bm->log_class,
+                       "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;
+  clib_memset (auth_key->key, 0, sizeof (auth_key->key));
+  clib_memcpy (auth_key->key, key_data, key_len);
+  return 0;
+#else
+  vlib_log_err (bm->log_class,
+               "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)
+       {
+         vlib_log_err (bm->log_class,
+                       "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);
+      clib_memset (auth_key, 0, sizeof (*auth_key));
+      pool_put (bm->auth_keys, auth_key);
+    }
+  else
+    {
+      /* no such key */
+      vlib_log_err (bm->log_class,
+                   "authentication key with conf ID %u does not exist",
+                   conf_key_id);
+      return VNET_API_ERROR_BFD_ENOENT;
+    }
+  return 0;
+#else
+  vlib_log_err (bm->log_class,
+               "SSL missing, cannot manipulate authentication keys");
+  return VNET_API_ERROR_BFD_NOTSUPP;
+#endif
 }
 
 bfd_main_t bfd_main;