c11 safe string handling support
[vpp.git] / src / vnet / bfd / bfd_main.c
index 8bb8de3..ea58413 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>
-#if WITH_LIBSSL > 0
-#include <openssl/sha.h>
+#include <vlib/log.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)
@@ -35,16 +57,15 @@ bfd_usec_to_clocks (const bfd_main_t * bm, u64 us)
   return bm->cpu_cps * ((f64) us / USEC_PER_SECOND);
 }
 
-static vlib_node_registration_t bfd_process_node;
+u32
+bfd_clocks_to_usec (const bfd_main_t * bm, u64 clocks)
+{
+  return (clocks / bm->cpu_cps) * USEC_PER_SECOND;
+}
 
-/* set to 0 here, real values filled at startup */
-static u32 bfd_node_index_by_transport[] = {
-#define F(t, n) [BFD_TRANSPORT_##t] = 0,
-  foreach_bfd_transport (F)
-#undef F
-};
+static vlib_node_registration_t bfd_process_node;
 
-static u8 *
+u8 *
 format_bfd_auth_key (u8 * s, va_list * args)
 {
   const bfd_auth_key_t *key = va_arg (*args, bfd_auth_key_t *);
@@ -81,17 +102,20 @@ 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->config_desired_min_tx_usec = BFD_DEFAULT_DESIRED_MIN_TX_US;
+  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
@@ -119,68 +143,90 @@ bfd_set_state (bfd_main_t * bm, bfd_session_t * bs,
     }
 }
 
-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->effective_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_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_demand)
+  if (bs->local_detect_mult > 1)
     {
-      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)
-           {
-             /* huh, we've missed it already, transmit now */
-             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
+      /* 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)
        {
-         /* 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)
-           {
-             /* huh, we've missed it already, transmit now */
-             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;
-           }
+         /*
+          * 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
     {
-      /* TODO */
+      /* 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)
     {
@@ -191,27 +237,40 @@ bfd_calc_next_tx (bfd_main_t * bm, bfd_session_t * bs, u64 now)
     }
 }
 
+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_demand)
+  if (bs->local_state == BFD_STATE_init || bs->local_state == BFD_STATE_up)
     {
-      /* asynchronous mode */
       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);
     }
-  else
-    {
-      /* demand mode */
-      bs->detection_time_clocks =
-       bs->local_detect_mult * clib_max (bs->config_desired_min_tx_clocks,
-                                         bs->remote_min_rx_clocks);
-    }
-  BFD_DBG ("Recalculated detection time %lu clocks/%.2fs",
-          bs->detection_time_clocks,
-          bs->detection_time_clocks / bm->cpu_cps);
 }
 
 static void
@@ -220,30 +279,44 @@ 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;
     }
-  if (bs->tx_timeout_clocks && rx_timeout)
+  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 (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");
+  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))
     {
+      int send_signal = 0;
       bs->wheel_time_clocks = next;
       BFD_DBG ("timing_wheel_insert(%p, %lu (%ld clocks/%.2fs in the "
               "future), %u);",
@@ -251,12 +324,41 @@ bfd_set_timer (bfd_main_t * bm, bfd_session_t * bs, u64 now,
               (i64) bs->wheel_time_clocks - clib_cpu_time_now (),
               (i64) (bs->wheel_time_clocks - clib_cpu_time_now ()) /
               bm->cpu_cps, bs->bs_idx);
+      bfd_lock (bm);
       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);
+
+         /* Send only if it is earlier than current awaited wakeup time */
+         send_signal =
+           (bs->wheel_time_clocks < bm->bfd_process_next_wakeup_clocks) &&
+           /*
+            * 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_clocks - bs->wheel_time_clocks >
+            2 * bm->bfd_process_wakeup_event_delay_clocks) &&
+           /* 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_clocks = 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);
        }
     }
 }
@@ -264,87 +366,109 @@ bfd_set_timer (bfd_main_t * bm, bfd_session_t * bs, u64 now,
 static void
 bfd_set_effective_desired_min_tx (bfd_main_t * bm,
                                  bfd_session_t * bs, u64 now,
-                                 u64 desired_min_tx_clocks,
-                                 int handling_wakeup)
+                                 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);
-  bfd_set_timer (bm, bs, now, handling_wakeup);
 }
 
 static void
 bfd_set_effective_required_min_rx (bfd_main_t * bm,
-                                  bfd_session_t * bs, u64 now,
-                                  u64 required_min_rx_clocks,
-                                  int handling_wakeup)
+                                  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);
-  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_usec,
-                               int handling_wakeup)
-{
-  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);
-  bfd_calc_next_tx (bm, bs, now);
-  bfd_set_timer (bm, bs, now, handling_wakeup);
+                               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 ("%U", format_bfd_session, bs);
+  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_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);
-}
-
-vnet_api_error_t
-bfd_del_session (uword bs_idx)
-{
-  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
-    {
-      BFD_ERR ("no such session");
-      return VNET_API_ERROR_BFD_ENOENT;
-    }
-  return 0;
+  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);
+      vlib_log_info (bm->log_class, "set session admin-up: %U",
+                    format_bfd_session_brief, bs);
       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_set_diag (bs, BFD_DIAG_CODE_neighbor_sig_down);
+      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 (bm, bs, BFD_STATE_admin_down, 0);
+      bfd_calc_next_tx (bm, bs, now);
+      bfd_set_timer (bm, bs, now, 0);
     }
 }
 
@@ -415,110 +539,230 @@ bfd_input_format_trace (u8 * s, va_list * args)
   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_effective_required_min_rx (bm, bs, now,
-                                        bs->config_required_min_rx_clocks,
-                                        handling_wakeup);
+      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),
-                                       handling_wakeup);
+                                        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:
-      bfd_set_effective_required_min_rx (bm, bs, now,
-                                        bs->config_required_min_rx_clocks,
-                                        handling_wakeup);
+      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),
-                                       handling_wakeup);
+                                        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,
-                                       clib_max
-                                       (bs->config_desired_min_tx_clocks,
-                                        bm->default_desired_min_tx_clocks),
-                                       handling_wakeup);
+                                       bs->config_desired_min_tx_clocks);
+      bfd_set_timer (bm, bs, now, handling_wakeup);
       break;
     case BFD_STATE_up:
-      if (POLL_NOT_NEEDED == bs->poll_state)
+      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, now,
-                                            bs->config_required_min_rx_clocks,
-                                            handling_wakeup);
+         bfd_set_effective_required_min_rx (bm, bs,
+                                            bs->config_required_min_rx_clocks);
        }
-      bfd_set_effective_desired_min_tx (bm, bs, now,
-                                       bs->config_desired_min_tx_clocks,
-                                       handling_wakeup);
+      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 (bs->remote_demand)
-    {
-      /* TODO - initiate poll sequence here */
-    }
-  else
+  /*
+   * 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)
     {
-      /* asynchronous - poll is part of periodic - nothing to do here */
+      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, 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:
       BFD_DBG ("Transport bfd via udp4, bs_idx=%u", bs->bs_idx);
-      bfd_add_udp4_transport (vm, b, bs);
+      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, b, bs);
+      bfd_add_udp6_transport (vm, bi, bs, 0 /* is_echo */ );
       break;
     }
 }
 
-static vlib_buffer_t *
-bfd_create_frame_to_next_node (vlib_main_t * vm, 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);
-
-  vlib_frame_t *f =
-    vlib_get_frame_to_node (vm, bfd_node_index_by_transport[bs->transport]);
-
-  u32 *to_next = vlib_frame_vector_args (f);
-  to_next[0] = bi;
-  f->n_vectors = 1;
+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;
+}
 
-  vlib_put_frame_to_node (vm, bfd_node_index_by_transport[bs->transport], f);
-  return b;
+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
@@ -530,7 +774,7 @@ bfd_add_sha1_auth_section (vlib_buffer_t * b, bfd_session_t * bs)
   b->current_length += sizeof (*auth);
   pkt->pkt.head.length += sizeof (*auth);
   bfd_pkt_set_auth_present (&pkt->pkt);
-  memset (auth, 0, sizeof (*auth));
+  clib_memset (auth, 0, sizeof (*auth));
   auth->type_len.type = bs->auth.curr_key->auth_type;
   /*
    * only meticulous authentication types require incrementing seq number
@@ -556,6 +800,7 @@ bfd_add_sha1_auth_section (vlib_buffer_t * b, bfd_session_t * bs)
 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;
@@ -568,8 +813,9 @@ bfd_add_auth_section (vlib_buffer_t * b, bfd_session_t * bs)
        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);
+         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:
@@ -581,53 +827,134 @@ bfd_add_auth_section (vlib_buffer_t * b, bfd_session_t * bs)
        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);
+         vlib_log_crit (bm->log_class,
+                        "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 (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);
-
   u32 bfd_length = 0;
   bfd_length = sizeof (bfd_pkt_t);
-  memset (pkt, 0, sizeof (*pkt));
+  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->config_desired_min_tx_usec);
-  pkt->req_min_rx = clib_host_to_net_u32 (bs->config_required_min_rx_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_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_usec)
+  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)
+       {
+         vlib_log_crit (bm->log_class, "buffer allocation failure");
+         return;
+       }
+      vlib_buffer_t *b = vlib_get_buffer (vm, bi);
+      ASSERT (b->current_data == 0);
+      clib_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);
+      clib_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
-       ("bfd.RemoteMinRxInterval is zero, not sending periodic control "
-        "frame");
+       ("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 (POLL_NOT_NEEDED == bs->poll_state && bs->remote_demand &&
+  if (BFD_POLL_NOT_NEEDED == bs->poll_state && bs->remote_demand &&
       BFD_STATE_up == bs->local_state && BFD_STATE_up == bs->remote_state)
     {
       /*
@@ -636,31 +963,57 @@ bfd_send_periodic (vlib_main_t * vm, vlib_node_runtime_t * rt,
        * bfd.SessionState is Up, and bfd.RemoteSessionState is Up) and a Poll
        * Sequence is not being transmitted.
        */
-      BFD_DBG ("bfd.RemoteDemand is non-zero, not sending periodic control "
-              "frame");
+      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 */
+  /*
+   * 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 ("Send periodic control frame for bs_idx=%lu: %U", bs->bs_idx,
-              format_bfd_session, bs);
-      vlib_buffer_t *b = bfd_create_frame_to_next_node (vm, bs);
-      if (!b)
+      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;
        }
-      bfd_init_control_frame (b, bs);
-      if (POLL_NOT_NEEDED != bs->poll_state)
+      vlib_buffer_t *b = vlib_get_buffer (vm, bi);
+      ASSERT (b->current_data == 0);
+      clib_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)
        {
-         /* here we are either beginning a new poll sequence or retrying .. */
+       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));
-         bs->poll_state = POLL_IN_PROGRESS;
          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, 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);
     }
@@ -670,32 +1023,35 @@ bfd_send_periodic (vlib_main_t * vm, vlib_node_runtime_t * rt,
        ("No need to send control frame now, now is %lu, tx_timeout is %lu",
         now, bs->tx_timeout_clocks);
     }
-  bfd_set_timer (bm, bs, now, handling_wakeup);
 }
 
 void
 bfd_init_final_control_frame (vlib_main_t * vm, vlib_buffer_t * b,
-                             bfd_session_t * bs)
+                             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_auth_section (b, bs);
-  bfd_add_transport_layer (vm, 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
    */
-  bs->poll_state = POLL_NOT_NEEDED;
+  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 */
+  /*
+   * 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)
     {
@@ -709,7 +1065,16 @@ bfd_check_rx_timeout (bfd_main_t * bm, bfd_session_t * bs, u64 now,
        * 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, handling_wakeup);
+      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);
     }
 }
 
@@ -721,21 +1086,36 @@ 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 (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);
+      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;
     }
 }
@@ -756,9 +1136,13 @@ bfd_process (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
   while (1)
     {
       u64 now = clib_cpu_time_now ();
+      bfd_lock (bm);
       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);
+      bm->bfd_process_next_wakeup_clocks =
+       (i64) next_expire >= 0 ? next_expire : ~0;
+      bfd_unlock (bm);
       if ((i64) next_expire < 0)
        {
          BFD_DBG ("wait for event without timeout");
@@ -781,48 +1165,66 @@ bfd_process (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
            }
        }
       now = clib_cpu_time_now ();
+      uword *session_index;
       switch (event_type)
        {
        case ~0:                /* no events => timeout */
          /* nothing to do here */
          break;
        case BFD_EVENT_RESCHEDULE:
+         bfd_lock (bm);
+         bm->bfd_process_wakeup_event_delay_clocks =
+           now - bm->bfd_process_wakeup_event_start_clocks;
+         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:
-         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, 1);
-           }
-         else
-           {
-             BFD_DBG ("Ignoring event for non-existent session index %u",
-                      (u32) * event_data);
-           }
+         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:
-         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);
-           }
+         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);
+      bfd_lock (bm);
       expired = timing_wheel_advance (&bm->wheel, now, expired, 0);
       BFD_DBG ("Expired %d elements", vec_len (expired));
       u32 *p = NULL;
@@ -833,8 +1235,10 @@ bfd_process (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
          {
            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);
          }
       }
+      bfd_unlock (bm);
       if (expired)
        {
          _vec_len (expired) = 0;
@@ -888,12 +1292,22 @@ 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
@@ -901,44 +1315,68 @@ bfd_main_init (vlib_main_t * vm)
   bm->random_seed = random_default_seed ();
   bm->vlib_main = vm;
   bm->vnet_main = vnet_get_main ();
-  memset (&bm->wheel, 0, sizeof (bm->wheel));
+  clib_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_US);
+    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;
-
-  vlib_node_t *node = NULL;
-#define F(t, n)                                                 \
-  node = vlib_get_node_by_name (vm, (u8 *)n);                   \
-  bfd_node_index_by_transport[BFD_TRANSPORT_##t] = node->index; \
-  BFD_DBG ("node '%s' has index %u", n, node->index);
-  foreach_bfd_transport (F);
-#undef F
+  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;
@@ -949,11 +1387,13 @@ bfd_put_session (bfd_main_t * bm, bfd_session_t * bs)
     }
   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);
@@ -964,6 +1404,7 @@ 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)
     {
@@ -1204,23 +1645,27 @@ 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)
 {
+  bfd_main_t *bm = &bfd_main;
   switch (auth_key->auth_type)
     {
     case BFD_AUTH_TYPE_reserved:
-      clib_warning ("Internal error, unexpected auth_type=%d:%s",
+      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:
-      clib_warning
-       ("Internal error, not implemented, unexpected auth_type=%d:%s",
-        auth_key->auth_type, bfd_auth_type_str (auth_key->auth_type));
+      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:
-      clib_warning
-       ("Internal error, not implemented, unexpected auth_type=%d:%s",
+      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:
@@ -1240,8 +1685,9 @@ bfd_verify_pkt_auth_key (const bfd_pkt_t * pkt, u32 pkt_size,
        }
       while (0);
 #else
-      clib_warning
-       ("Internal error, attempt to use SHA1 without SSL support");
+      vlib_log_err
+       (bm->log_class,
+        "internal error, attempt to use SHA1 without SSL support");
       return 0;
 #endif
     }
@@ -1336,8 +1782,10 @@ bfd_verify_pkt_auth (const bfd_pkt_t * pkt, u16 pkt_size, bfd_session_t * bs)
 void
 bfd_consume_pkt (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;
     }
@@ -1345,6 +1793,7 @@ 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);
+  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))
@@ -1360,8 +1809,9 @@ bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
        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));
+         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 */
@@ -1383,31 +1833,49 @@ bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
     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), 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 */
-  if (bs->poll_state == POLL_IN_PROGRESS && bfd_pkt_get_final (pkt))
+                                 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))
     {
-      bs->poll_state = POLL_NOT_NEEDED;
-      BFD_DBG ("Poll sequence terminated, bs_idx=%u", bs->bs_idx);
-      if (BFD_STATE_up == bs->local_state)
+      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)
        {
-         bfd_set_effective_required_min_rx (bm, bs, now,
-                                            bs->config_required_min_rx_clocks,
-                                            0);
-         bfd_recalc_detection_time (bm, bs);
+         /*
+          * 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)
-    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);
@@ -1417,10 +1885,12 @@ 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_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);
        }
     }
@@ -1429,6 +1899,7 @@ 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_diag (bs, BFD_DIAG_CODE_no_diag);
          bfd_set_state (bm, bs, BFD_STATE_up, 0);
        }
     }
@@ -1442,52 +1913,86 @@ bfd_consume_pkt (bfd_main_t * bm, const bfd_pkt_t * pkt, u32 bs_idx)
     }
 }
 
-static const char *
-bfd_poll_state_string (bfd_poll_state_e state)
+int
+bfd_consume_echo_pkt (bfd_main_t * bm, vlib_buffer_t * b)
 {
-  switch (state)
+  bfd_echo_pkt_t *pkt = NULL;
+  if (b->current_length != sizeof (*pkt))
     {
-#define F(x)     \
-  case POLL_##x: \
-    return "POLL_" #x;
-      foreach_bfd_poll_state (F)
-#undef F
+      return 0;
     }
-  return "UNKNOWN";
+  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 *);
-  s = 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.RequiredMinEchoRxInterval=%u, "
-             "bfd.RemoteMinRxInterval=%u, "
-             "bfd.DemandMode=%s, "
-             "bfd.RemoteDemandMode=%s, "
-             "bfd.DetectMult=%u, "
-             "Auth: {local-seq-num=%u, "
-             "remote-seq-num=%u, "
-             "is-delayed=%s, "
-             "curr-key=%U, "
-             "next-key=%U},"
-             "poll-state: %s",
+  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), bs->local_discr,
-             bs->remote_discr, bfd_diag_code_string (bs->local_diag),
+             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,
-             1, bs->remote_min_rx_usec, (bs->local_demand ? "yes" : "no"),
-             (bs->remote_demand ? "yes" : "no"), bs->local_detect_mult,
-             bs->auth.local_seq_number, bs->auth.remote_seq_number,
-             (bs->auth.is_delayed ? "yes" : "no"), format_bfd_auth_key,
-             bs->auth.curr_key, format_bfd_auth_key, bs->auth.next_key,
-             bfd_poll_state_string (bs->poll_state));
+             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;
 }
 
@@ -1511,7 +2016,8 @@ bfd_auth_activate (bfd_session_t * bs, u32 conf_key_id,
     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)",
+      vlib_log_err (bm->log_class,
+                   "authentication key with config ID %u doesn't exist)",
                    conf_key_id);
       return VNET_API_ERROR_BFD_ENOENT;
     }
@@ -1544,13 +2050,16 @@ bfd_auth_activate (bfd_session_t * bs, u32 conf_key_id,
       bs->auth.is_delayed = 0;
     }
   ++key->use_count;
-  BFD_DBG ("Session auth modified: %U", format_bfd_session, bs);
+  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)
     {
@@ -1578,10 +2087,13 @@ bfd_auth_deactivate (bfd_session_t * bs, u8 is_delayed)
       --bs->auth.next_key->use_count;
       bs->auth.next_key = NULL;
     }
-  BFD_DBG ("Session auth modified: %U", format_bfd_session, bs);
+  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
-  clib_warning ("SSL missing, cannot deactivate BFD authentication");
+  vlib_log_err (bm->log_class,
+               "SSL missing, cannot deactivate BFD authentication");
   return VNET_API_ERROR_BFD_NOTSUPP;
 #endif
 }
@@ -1595,10 +2107,10 @@ bfd_session_set_params (bfd_main_t * bm, bfd_session_t * bs,
       bs->config_desired_min_tx_usec != desired_min_tx_usec ||
       bs->config_required_min_rx_usec != required_min_rx_usec)
     {
-      BFD_DBG ("Changing session params: %U", format_bfd_session, bs);
+      BFD_DBG ("\nChanging session params: %U", format_bfd_session, bs);
       switch (bs->poll_state)
        {
-       case POLL_NOT_NEEDED:
+       case BFD_POLL_NOT_NEEDED:
          if (BFD_STATE_up == bs->local_state ||
              BFD_STATE_init == bs->local_state)
            {
@@ -1606,21 +2118,26 @@ bfd_session_set_params (bfd_main_t * bm, bfd_session_t * bs,
              if (bs->config_desired_min_tx_usec != desired_min_tx_usec ||
                  bs->config_required_min_rx_usec != required_min_rx_usec)
                {
-                 bs->poll_state = POLL_NEEDED;
-                 BFD_DBG ("Set poll state=%s, bs_idx=%u",
-                          bfd_poll_state_string (bs->poll_state),
-                          bs->bs_idx);
+                 bfd_set_poll_state (bs, BFD_POLL_NEEDED);
                }
            }
          break;
-       case POLL_NEEDED:
-         /* nothing to do */
+       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 POLL_IN_PROGRESS:
-         /* can't change params now ... */
-         BFD_ERR ("Poll in progress, cannot change params for session with "
-                  "bs_idx=%u", bs->bs_idx);
-         return VNET_API_ERROR_BFD_EAGAIN;
+       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;
@@ -1630,8 +2147,10 @@ bfd_session_set_params (bfd_main_t * bm, bfd_session_t * bs,
       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 ("Changed session params: %U", format_bfd_session, bs);
+      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);
     }
@@ -1642,6 +2161,102 @@ bfd_session_set_params (bfd_main_t * bm, bfd_session_t * bs,
   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;
 
 /*