bfd: use tw_timer_template instead of legacy wheel
[vpp.git] / src / vnet / bfd / bfd_udp.c
index 677f1e2..0edf8a8 100644 (file)
@@ -1,18 +1,40 @@
+/*
+ * Copyright (c) 2011-2016 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/**
+ * @file
+ * @brief BFD UDP transport layer implementation
+ */
 #include <vppinfra/types.h>
 #include <vlibmemory/api.h>
 #include <vlib/vlib.h>
 #include <vlib/buffer.h>
 #include <vnet/ip/format.h>
 #include <vnet/ethernet/packet.h>
-#include <vnet/ip/udp_packet.h>
+#include <vnet/udp/udp_packet.h>
+#include <vnet/udp/udp.h>
 #include <vnet/ip/lookup.h>
 #include <vnet/ip/icmp46_packet.h>
 #include <vnet/ip/ip4.h>
 #include <vnet/ip/ip6.h>
-#include <vnet/ip/udp.h>
 #include <vnet/ip/ip6_packet.h>
+#include <vnet/ip/ip6_link.h>
 #include <vnet/adj/adj.h>
 #include <vnet/adj/adj_nbr.h>
+#include <vnet/dpo/receive_dpo.h>
+#include <vnet/fib/fib_entry.h>
+#include <vnet/fib/fib_table.h>
 #include <vnet/bfd/bfd_debug.h>
 #include <vnet/bfd/bfd_udp.h>
 #include <vnet/bfd/bfd_main.h>
@@ -24,64 +46,420 @@ typedef struct
   /* hashmap - bfd session index by bfd key - used for CLI/API lookup, where
    * discriminator is unknown */
   mhash_t bfd_session_idx_by_bfd_key;
+  /* convenience variable */
+  vnet_main_t *vnet_main;
+  /* flag indicating whether echo_source_sw_if_index holds a valid value */
+  int echo_source_is_set;
+  /* loopback interface used to get echo source ip */
+  u32 echo_source_sw_if_index;
+  /* node index of "ip4-arp" node */
+  u32 ip4_arp_idx;
+  /* node index of "ip6-discover-neighbor" node */
+  u32 ip6_ndp_idx;
+  /* node index of "ip4-rewrite" node */
+  u32 ip4_rewrite_idx;
+  /* node index of "ip6-rewrite" node */
+  u32 ip6_rewrite_idx;
+  /* node index of "ip4-midchain" node */
+  u32 ip4_midchain_idx;
+  /* node index of "ip6-midchain" node */
+  u32 ip6_midchain_idx;
+  /* log class */
+  vlib_log_class_t log_class;
+  /* number of active udp4 sessions */
+  u32 udp4_sessions_count;
+  /* number of active udp6 sessions */
+  u32 udp6_sessions_count;
 } bfd_udp_main_t;
 
 static vlib_node_registration_t bfd_udp4_input_node;
 static vlib_node_registration_t bfd_udp6_input_node;
+static vlib_node_registration_t bfd_udp_echo4_input_node;
+static vlib_node_registration_t bfd_udp_echo6_input_node;
 
 bfd_udp_main_t bfd_udp_main;
 
-void bfd_udp_transport_to_buffer (vlib_main_t *vm, vlib_buffer_t *b,
-                                  bfd_udp_session_t *bus)
+vnet_api_error_t
+bfd_udp_set_echo_source (u32 sw_if_index)
 {
-  udp_header_t *udp;
-  u16 udp_length, ip_length;
-  bfd_udp_key_t *key = &bus->key;
+  vnet_sw_interface_t *sw_if =
+    vnet_get_sw_interface_or_null (bfd_udp_main.vnet_main, sw_if_index);
+  if (sw_if)
+    {
+      bfd_udp_main.echo_source_sw_if_index = sw_if_index;
+      bfd_udp_main.echo_source_is_set = 1;
+      return 0;
+    }
+  return VNET_API_ERROR_BFD_ENOENT;
+}
+
+vnet_api_error_t
+bfd_udp_del_echo_source (u32 sw_if_index)
+{
+  bfd_udp_main.echo_source_sw_if_index = ~0;
+  bfd_udp_main.echo_source_is_set = 0;
+  return 0;
+}
+
+int
+bfd_udp_is_echo_available (bfd_transport_e transport)
+{
+  if (!bfd_udp_main.echo_source_is_set)
+    {
+      BFD_DBG ("UDP echo source not set - echo not available");
+      return 0;
+    }
+  /*
+   * for the echo to work, we need a loopback interface with at least one
+   * address with netmask length at most 31 (ip4) or 127 (ip6) so that we can
+   * pick an unused address from that subnet
+   */
+  vnet_sw_interface_t *sw_if =
+    vnet_get_sw_interface_or_null (bfd_udp_main.vnet_main,
+                                  bfd_udp_main.echo_source_sw_if_index);
+  if (sw_if && sw_if->flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP)
+    {
+      if (BFD_TRANSPORT_UDP4 == transport)
+       {
+         ip4_main_t *im = &ip4_main;
+         ip_interface_address_t *ia = NULL;
+          /* *INDENT-OFF* */
+          foreach_ip_interface_address (&im->lookup_main, ia,
+                                        bfd_udp_main.echo_source_sw_if_index,
+                                        0 /* honor unnumbered */, ({
+                                          if (ia->address_length <= 31)
+                                            {
+                                              return 1;
+                                            }
+                                        }));
+          /* *INDENT-ON* */
+       }
+      else if (BFD_TRANSPORT_UDP6 == transport)
+       {
+         ip6_main_t *im = &ip6_main;
+         ip_interface_address_t *ia = NULL;
+          /* *INDENT-OFF* */
+          foreach_ip_interface_address (&im->lookup_main, ia,
+                                        bfd_udp_main.echo_source_sw_if_index,
+                                        0 /* honor unnumbered */, ({
+                                          if (ia->address_length <= 127)
+                                            {
+                                              return 1;
+                                            }
+                                        }));
+          /* *INDENT-ON* */
+       }
+    }
+  BFD_DBG ("No usable IP address for UDP echo - echo not available");
+  return 0;
+}
+
+static u16
+bfd_udp_bs_idx_to_sport (u32 bs_idx)
+{
+  /* The source port MUST be in the range 49152 through 65535. The same UDP
+   * source port number MUST be used for all BFD Control packets associated
+   * with a particular session.  The source port number SHOULD be unique among
+   * all BFD sessions on the system. If more than 16384 BFD sessions are
+   * simultaneously active, UDP source port numbers MAY be reused on
+   * multiple sessions, but the number of distinct uses of the same UDP
+   * source port number SHOULD be minimized.
+   */
+  return 49152 + bs_idx % (65535 - 49152 + 1);
+}
 
-  b->flags |= VNET_BUFFER_LOCALLY_ORIGINATED;
-  if (ip46_address_is_ip4 (&key->local_addr))
+int
+bfd_udp_get_echo_src_ip4 (ip4_address_t * addr)
+{
+  if (!bfd_udp_main.echo_source_is_set)
     {
-      ip4_header_t *ip4;
-      const size_t data_size = sizeof (*ip4) + sizeof (*udp);
-      vlib_buffer_advance (b, -data_size);
-      ip4 = vlib_buffer_get_current (b);
-      udp = (udp_header_t *)(ip4 + 1);
-      memset (ip4, 0, data_size);
-      ip4->ip_version_and_header_length = 0x45;
-      ip4->ttl = 255;
-      ip4->protocol = IP_PROTOCOL_UDP;
-      ip4->src_address.as_u32 = key->local_addr.ip4.as_u32;
-      ip4->dst_address.as_u32 = key->peer_addr.ip4.as_u32;
+      BFD_ERR ("cannot find ip4 address, echo source not set");
+      return 0;
+    }
+  ip_interface_address_t *ia = NULL;
+  ip4_main_t *im = &ip4_main;
 
-      udp->src_port = clib_host_to_net_u16 (50000); /* FIXME */
-      udp->dst_port = clib_host_to_net_u16 (UDP_DST_PORT_bfd4);
+  /* *INDENT-OFF* */
+  foreach_ip_interface_address (
+      &im->lookup_main, ia, bfd_udp_main.echo_source_sw_if_index,
+      0 /* honor unnumbered */, ({
+        ip4_address_t *x =
+            ip_interface_address_get_address (&im->lookup_main, ia);
+        if (ia->address_length <= 31)
+          {
+            addr->as_u32 = clib_host_to_net_u32 (x->as_u32);
+            /*
+             * flip the last bit to get a different address, might be network,
+             * we don't care ...
+             */
+            addr->as_u32 ^= 1;
+            addr->as_u32 = clib_net_to_host_u32 (addr->as_u32);
+            return 1;
+          }
+      }));
+  /* *INDENT-ON* */
+  BFD_ERR ("cannot find ip4 address, no usable address found");
+  return 0;
+}
 
-      /* fix ip length, checksum and udp length */
-      ip_length = vlib_buffer_length_in_chain (vm, b);
+int
+bfd_udp_get_echo_src_ip6 (ip6_address_t * addr)
+{
+  if (!bfd_udp_main.echo_source_is_set)
+    {
+      BFD_ERR ("cannot find ip6 address, echo source not set");
+      return 0;
+    }
+  ip_interface_address_t *ia = NULL;
+  ip6_main_t *im = &ip6_main;
 
-      ip4->length = clib_host_to_net_u16 (ip_length);
-      ip4->checksum = ip4_header_checksum (ip4);
+  /* *INDENT-OFF* */
+  foreach_ip_interface_address (
+      &im->lookup_main, ia, bfd_udp_main.echo_source_sw_if_index,
+      0 /* honor unnumbered */, ({
+        ip6_address_t *x =
+            ip_interface_address_get_address (&im->lookup_main, ia);
+        if (ia->address_length <= 127)
+          {
+            *addr = *x;
+            addr->as_u8[15] ^= 1; /* flip the last bit of the address */
+            return 1;
+          }
+      }));
+  /* *INDENT-ON* */
+  BFD_ERR ("cannot find ip6 address, no usable address found");
+  return 0;
+}
+
+void
+bfd_udp_get_echo_source (int *is_set, u32 * sw_if_index,
+                        int *have_usable_ip4, ip4_address_t * ip4,
+                        int *have_usable_ip6, ip6_address_t * ip6)
+{
+  if (bfd_udp_main.echo_source_is_set)
+    {
+      *is_set = 1;
+      *sw_if_index = bfd_udp_main.echo_source_sw_if_index;
+      *have_usable_ip4 = bfd_udp_get_echo_src_ip4 (ip4);
+      *have_usable_ip6 = bfd_udp_get_echo_src_ip6 (ip6);
+    }
+  else
+    {
+      *is_set = 0;
+    }
+}
+
+int
+bfd_add_udp4_transport (vlib_main_t * vm, u32 bi, const bfd_session_t * bs,
+                       int is_echo)
+{
+  const bfd_udp_session_t *bus = &bs->udp;
+  const bfd_udp_key_t *key = &bus->key;
+  vlib_buffer_t *b = vlib_get_buffer (vm, bi);
 
-      udp_length = ip_length - (sizeof (*ip4));
-      udp->length = clib_host_to_net_u16 (udp_length);
+  b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
+  vnet_buffer (b)->ip.adj_index[VLIB_RX] = bus->adj_index;
+  vnet_buffer (b)->ip.adj_index[VLIB_TX] = bus->adj_index;
+  vnet_buffer (b)->sw_if_index[VLIB_RX] = 0;
+  vnet_buffer (b)->sw_if_index[VLIB_TX] = ~0;
+  typedef struct
+  {
+    ip4_header_t ip4;
+    udp_header_t udp;
+  } ip4_udp_headers;
+  ip4_udp_headers *headers = NULL;
+  vlib_buffer_advance (b, -sizeof (*headers));
+  headers = vlib_buffer_get_current (b);
+  clib_memset (headers, 0, sizeof (*headers));
+  headers->ip4.ip_version_and_header_length = 0x45;
+  headers->ip4.ttl = 255;
+  headers->ip4.protocol = IP_PROTOCOL_UDP;
+  headers->udp.src_port =
+    clib_host_to_net_u16 (bfd_udp_bs_idx_to_sport (bs->bs_idx));
+  if (is_echo)
+    {
+      int rv;
+      if (!(rv = bfd_udp_get_echo_src_ip4 (&headers->ip4.src_address)))
+       {
+         return rv;
+       }
+      headers->ip4.dst_address.as_u32 = key->local_addr.ip4.as_u32;
+      headers->udp.dst_port = clib_host_to_net_u16 (UDP_DST_PORT_bfd_echo4);
     }
   else
     {
-      BFD_ERR ("not implemented");
-      abort ();
+      headers->ip4.src_address.as_u32 = key->local_addr.ip4.as_u32;
+      headers->ip4.dst_address.as_u32 = key->peer_addr.ip4.as_u32;
+      headers->udp.dst_port = clib_host_to_net_u16 (UDP_DST_PORT_bfd4);
     }
+
+  /* fix ip length, checksum and udp length */
+  const u16 ip_length = vlib_buffer_length_in_chain (vm, b);
+
+  headers->ip4.length = clib_host_to_net_u16 (ip_length);
+  headers->ip4.checksum = ip4_header_checksum (&headers->ip4);
+
+  const u16 udp_length = ip_length - (sizeof (headers->ip4));
+  headers->udp.length = clib_host_to_net_u16 (udp_length);
+  return 1;
 }
 
-void bfd_add_udp_transport (vlib_main_t *vm, vlib_buffer_t *b,
-                            bfd_udp_session_t *bus)
+int
+bfd_add_udp6_transport (vlib_main_t * vm, u32 bi, const bfd_session_t * bs,
+                       int is_echo)
 {
+  const bfd_udp_session_t *bus = &bs->udp;
+  const bfd_udp_key_t *key = &bus->key;
+  vlib_buffer_t *b = vlib_get_buffer (vm, bi);
+
+  b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
   vnet_buffer (b)->ip.adj_index[VLIB_RX] = bus->adj_index;
   vnet_buffer (b)->ip.adj_index[VLIB_TX] = bus->adj_index;
-  bfd_udp_transport_to_buffer (vm, b, bus);
+  vnet_buffer (b)->sw_if_index[VLIB_RX] = 0;
+  vnet_buffer (b)->sw_if_index[VLIB_TX] = 0;
+  typedef struct
+  {
+    ip6_header_t ip6;
+    udp_header_t udp;
+  } ip6_udp_headers;
+  ip6_udp_headers *headers = NULL;
+  vlib_buffer_advance (b, -sizeof (*headers));
+  headers = vlib_buffer_get_current (b);
+  clib_memset (headers, 0, sizeof (*headers));
+  headers->ip6.ip_version_traffic_class_and_flow_label =
+    clib_host_to_net_u32 (0x6 << 28);
+  headers->ip6.hop_limit = 255;
+  headers->ip6.protocol = IP_PROTOCOL_UDP;
+  headers->udp.src_port =
+    clib_host_to_net_u16 (bfd_udp_bs_idx_to_sport (bs->bs_idx));
+  if (is_echo)
+    {
+      int rv;
+      if (!(rv = bfd_udp_get_echo_src_ip6 (&headers->ip6.src_address)))
+       {
+         return rv;
+       }
+      clib_memcpy_fast (&headers->ip6.dst_address, &key->local_addr.ip6,
+                       sizeof (headers->ip6.dst_address));
+
+      headers->udp.dst_port = clib_host_to_net_u16 (UDP_DST_PORT_bfd_echo6);
+    }
+  else
+    {
+      clib_memcpy_fast (&headers->ip6.src_address, &key->local_addr.ip6,
+                       sizeof (headers->ip6.src_address));
+      clib_memcpy_fast (&headers->ip6.dst_address, &key->peer_addr.ip6,
+                       sizeof (headers->ip6.dst_address));
+      headers->udp.dst_port = clib_host_to_net_u16 (UDP_DST_PORT_bfd6);
+    }
+
+  /* fix ip payload length and udp length */
+  const u16 udp_length =
+    vlib_buffer_length_in_chain (vm, b) - (sizeof (headers->ip6));
+  headers->udp.length = clib_host_to_net_u16 (udp_length);
+  headers->ip6.payload_length = headers->udp.length;
+
+  /* IPv6 UDP checksum is mandatory */
+  int bogus = 0;
+  headers->udp.checksum =
+    ip6_tcp_udp_icmp_compute_checksum (vm, b, &headers->ip6, &bogus);
+  ASSERT (bogus == 0);
+  if (headers->udp.checksum == 0)
+    {
+      headers->udp.checksum = 0xffff;
+    }
+  return 1;
+}
+
+static void
+bfd_create_frame_to_next_node (vlib_main_t * vm, u32 bi, u32 next_node)
+{
+  vlib_frame_t *f = vlib_get_frame_to_node (vm, next_node);
+  u32 *to_next = vlib_frame_vector_args (f);
+  to_next[0] = bi;
+  f->n_vectors = 1;
+  vlib_put_frame_to_node (vm, next_node, f);
+}
+
+int
+bfd_udp_calc_next_node (const struct bfd_session_s *bs, u32 * next_node)
+{
+  vnet_main_t *vnm = vnet_get_main ();
+  const bfd_udp_session_t *bus = &bs->udp;
+  ip_adjacency_t *adj = adj_get (bus->adj_index);
+
+  /* don't try to send the buffer if the interface is not up */
+  if (!vnet_sw_interface_is_up (vnm, bus->key.sw_if_index))
+    return 0;
+
+  switch (adj->lookup_next_index)
+    {
+    case IP_LOOKUP_NEXT_ARP:
+      switch (bs->transport)
+       {
+       case BFD_TRANSPORT_UDP4:
+         *next_node = bfd_udp_main.ip4_arp_idx;
+         return 1;
+       case BFD_TRANSPORT_UDP6:
+         *next_node = bfd_udp_main.ip6_ndp_idx;
+         return 1;
+       }
+      break;
+    case IP_LOOKUP_NEXT_REWRITE:
+      switch (bs->transport)
+       {
+       case BFD_TRANSPORT_UDP4:
+         *next_node = bfd_udp_main.ip4_rewrite_idx;
+         return 1;
+       case BFD_TRANSPORT_UDP6:
+         *next_node = bfd_udp_main.ip6_rewrite_idx;
+         return 1;
+       }
+      break;
+    case IP_LOOKUP_NEXT_MIDCHAIN:
+      switch (bs->transport)
+       {
+       case BFD_TRANSPORT_UDP4:
+         *next_node = bfd_udp_main.ip4_midchain_idx;
+         return 1;
+       case BFD_TRANSPORT_UDP6:
+         *next_node = bfd_udp_main.ip6_midchain_idx;
+         return 1;
+       }
+      break;
+    default:
+      /* drop */
+      break;
+    }
+  return 0;
 }
 
-static bfd_session_t *bfd_lookup_session (bfd_udp_main_t *bum,
-                                          const bfd_udp_key_t *key)
+int
+bfd_transport_udp4 (vlib_main_t * vm, u32 bi, const struct bfd_session_s *bs)
+{
+  u32 next_node;
+  int rv = bfd_udp_calc_next_node (bs, &next_node);
+  if (rv)
+    {
+      bfd_create_frame_to_next_node (vm, bi, next_node);
+    }
+  return rv;
+}
+
+int
+bfd_transport_udp6 (vlib_main_t * vm, u32 bi, const struct bfd_session_s *bs)
+{
+  u32 next_node;
+  int rv = bfd_udp_calc_next_node (bs, &next_node);
+  if (rv)
+    {
+      bfd_create_frame_to_next_node (vm, bi, next_node);
+    }
+  return 1;
+}
+
+static bfd_session_t *
+bfd_lookup_session (bfd_udp_main_t * bum, const bfd_udp_key_t * key)
 {
   uword *p = mhash_get (&bum->bfd_session_idx_by_bfd_key, key);
   if (p)
@@ -91,87 +469,122 @@ static bfd_session_t *bfd_lookup_session (bfd_udp_main_t *bum,
   return 0;
 }
 
+static void
+bfd_udp_key_init (bfd_udp_key_t * key, u32 sw_if_index,
+                 const ip46_address_t * local_addr,
+                 const ip46_address_t * peer_addr)
+{
+  clib_memset (key, 0, sizeof (*key));
+  key->sw_if_index = sw_if_index;
+  key->local_addr.as_u64[0] = local_addr->as_u64[0];
+  key->local_addr.as_u64[1] = local_addr->as_u64[1];
+  key->peer_addr.as_u64[0] = peer_addr->as_u64[0];
+  key->peer_addr.as_u64[1] = peer_addr->as_u64[1];
+}
+
 static vnet_api_error_t
-bfd_udp_add_session_internal (bfd_udp_main_t *bum, u32 sw_if_index,
-                              u32 desired_min_tx_us, u32 required_min_rx_us,
-                              u8 detect_mult, const ip46_address_t *local_addr,
-                              const ip46_address_t *peer_addr)
+bfd_udp_add_session_internal (vlib_main_t * vm, bfd_udp_main_t * bum,
+                             u32 sw_if_index, u32 desired_min_tx_usec,
+                             u32 required_min_rx_usec, u8 detect_mult,
+                             const ip46_address_t * local_addr,
+                             const ip46_address_t * peer_addr,
+                             bfd_session_t ** bs_out)
 {
-  vnet_sw_interface_t *sw_if =
-      vnet_get_sw_interface (vnet_get_main (), sw_if_index);
   /* get a pool entry and if we end up not needing it, give it back */
-  bfd_transport_t t = BFD_TRANSPORT_UDP4;
+  bfd_transport_e t = BFD_TRANSPORT_UDP4;
   if (!ip46_address_is_ip4 (local_addr))
     {
       t = BFD_TRANSPORT_UDP6;
     }
   bfd_session_t *bs = bfd_get_session (bum->bfd_main, t);
+  if (!bs)
+    {
+      return VNET_API_ERROR_BFD_EAGAIN;
+    }
   bfd_udp_session_t *bus = &bs->udp;
-  memset (bus, 0, sizeof (*bus));
+  clib_memset (bus, 0, sizeof (*bus));
   bfd_udp_key_t *key = &bus->key;
-  key->sw_if_index = sw_if->sw_if_index;
-  key->local_addr.as_u64[0] = local_addr->as_u64[0];
-  key->local_addr.as_u64[1] = local_addr->as_u64[1];
-  key->peer_addr.as_u64[0] = peer_addr->as_u64[0];
-  key->peer_addr.as_u64[1] = peer_addr->as_u64[1];
+  bfd_udp_key_init (key, sw_if_index, local_addr, peer_addr);
   const bfd_session_t *tmp = bfd_lookup_session (bum, key);
   if (tmp)
     {
-      BFD_ERR ("duplicate bfd-udp session, existing bs_idx=%d", tmp->bs_idx);
+      vlib_log_err (bum->log_class,
+                   "duplicate bfd-udp session, existing bs_idx=%d",
+                   tmp->bs_idx);
       bfd_put_session (bum->bfd_main, bs);
       return VNET_API_ERROR_BFD_EEXIST;
     }
-  key->sw_if_index = sw_if->sw_if_index;
   mhash_set (&bum->bfd_session_idx_by_bfd_key, key, bs->bs_idx, NULL);
   BFD_DBG ("session created, bs_idx=%u, sw_if_index=%d, local=%U, peer=%U",
-           bs->bs_idx, key->sw_if_index, format_ip46_address, &key->local_addr,
-           IP46_TYPE_ANY, format_ip46_address, &key->peer_addr, IP46_TYPE_ANY);
+          bs->bs_idx, key->sw_if_index, format_ip46_address,
+          &key->local_addr, IP46_TYPE_ANY, format_ip46_address,
+          &key->peer_addr, IP46_TYPE_ANY);
+  vlib_log_info (bum->log_class, "create BFD session: %U",
+                format_bfd_session, bs);
   if (BFD_TRANSPORT_UDP4 == t)
     {
       bus->adj_index = adj_nbr_add_or_lock (FIB_PROTOCOL_IP4, VNET_LINK_IP4,
-                                            &key->peer_addr, key->sw_if_index);
+                                           &key->peer_addr,
+                                           key->sw_if_index);
       BFD_DBG ("adj_nbr_add_or_lock(FIB_PROTOCOL_IP4, VNET_LINK_IP4, %U, %d) "
-               "returns %d",
-               format_ip46_address, &key->peer_addr, IP46_TYPE_ANY,
-               key->sw_if_index, bus->adj_index);
+              "returns %d", format_ip46_address, &key->peer_addr,
+              IP46_TYPE_ANY, key->sw_if_index, bus->adj_index);
+      ++bum->udp4_sessions_count;
+      if (1 == bum->udp4_sessions_count)
+       {
+         udp_register_dst_port (vm, UDP_DST_PORT_bfd4,
+                                bfd_udp4_input_node.index, 1);
+         udp_register_dst_port (vm, UDP_DST_PORT_bfd_echo4,
+                                bfd_udp_echo4_input_node.index, 1);
+       }
     }
   else
     {
       bus->adj_index = adj_nbr_add_or_lock (FIB_PROTOCOL_IP6, VNET_LINK_IP6,
-                                            &key->peer_addr, key->sw_if_index);
+                                           &key->peer_addr,
+                                           key->sw_if_index);
       BFD_DBG ("adj_nbr_add_or_lock(FIB_PROTOCOL_IP6, VNET_LINK_IP6, %U, %d) "
-               "returns %d",
-               format_ip46_address, &key->peer_addr, IP46_TYPE_ANY,
-               key->sw_if_index, bus->adj_index);
-    }
-  bs->config_desired_min_tx_us = desired_min_tx_us;
-  bs->required_min_rx_us = required_min_rx_us;
-  bs->required_min_echo_rx_us = required_min_rx_us; /* FIXME */
-  bs->local_detect_mult = detect_mult;
-  bfd_session_start (bum->bfd_main, bs);
-  return 0;
+              "returns %d", format_ip46_address, &key->peer_addr,
+              IP46_TYPE_ANY, key->sw_if_index, bus->adj_index);
+      ++bum->udp6_sessions_count;
+      if (1 == bum->udp6_sessions_count)
+       {
+         udp_register_dst_port (vm, UDP_DST_PORT_bfd6,
+                                bfd_udp6_input_node.index, 0);
+         udp_register_dst_port (vm, UDP_DST_PORT_bfd_echo6,
+                                bfd_udp_echo6_input_node.index, 0);
+       }
+    }
+  *bs_out = bs;
+  return bfd_session_set_params (bum->bfd_main, bs, desired_min_tx_usec,
+                                required_min_rx_usec, detect_mult);
 }
 
 static vnet_api_error_t
-bfd_udp_validate_api_input (u32 sw_if_index, const ip46_address_t *local_addr,
-                            const ip46_address_t *peer_addr)
+bfd_udp_validate_api_input (u32 sw_if_index,
+                           const ip46_address_t * local_addr,
+                           const ip46_address_t * peer_addr)
 {
+  bfd_udp_main_t *bum = &bfd_udp_main;
   vnet_sw_interface_t *sw_if =
-      vnet_get_sw_interface (vnet_get_main (), sw_if_index);
+    vnet_get_sw_interface_or_null (bfd_udp_main.vnet_main, sw_if_index);
   u8 local_ip_valid = 0;
   ip_interface_address_t *ia = NULL;
   if (!sw_if)
     {
-      BFD_ERR ("got NULL sw_if");
+      vlib_log_err (bum->log_class,
+                   "got NULL sw_if when getting interface by index %u",
+                   sw_if_index);
       return VNET_API_ERROR_INVALID_SW_IF_INDEX;
     }
   if (ip46_address_is_ip4 (local_addr))
     {
       if (!ip46_address_is_ip4 (peer_addr))
-        {
-          BFD_ERR ("IP family mismatch");
-          return VNET_API_ERROR_INVALID_ARGUMENT;
-        }
+       {
+         vlib_log_err (bum->log_class,
+                       "IP family mismatch (local is ipv4, peer is ipv6)");
+         return VNET_API_ERROR_INVALID_ARGUMENT;
+       }
       ip4_main_t *im = &ip4_main;
 
       /* *INDENT-OFF* */
@@ -191,109 +604,322 @@ bfd_udp_validate_api_input (u32 sw_if_index, const ip46_address_t *local_addr,
   else
     {
       if (ip46_address_is_ip4 (peer_addr))
-        {
-          BFD_ERR ("IP family mismatch");
-          return VNET_API_ERROR_INVALID_ARGUMENT;
-        }
-      ip6_main_t *im = &ip6_main;
-      /* *INDENT-OFF* */
-      foreach_ip_interface_address (
-          &im->lookup_main, ia, sw_if_index, 0 /* honor unnumbered */, ({
-            ip6_address_t *x =
-                ip_interface_address_get_address (&im->lookup_main, ia);
-            if (local_addr->ip6.as_u64[0] == x->as_u64[0] &&
-                local_addr->ip6.as_u64[1] == x->as_u64[1])
-              {
-                /* valid address for this interface */
-                local_ip_valid = 1;
-                break;
-              }
-          }));
-      /* *INDENT-ON* */
+       {
+         vlib_log_err (bum->log_class,
+                       "IP family mismatch (local is ipv6, peer is ipv4)");
+         return VNET_API_ERROR_INVALID_ARGUMENT;
+       }
+
+      if (ip6_address_is_link_local_unicast (&local_addr->ip6))
+       {
+         const ip6_address_t *ll_addr;
+         ll_addr = ip6_get_link_local_address (sw_if_index);
+         if (ip6_address_is_equal (ll_addr, &local_addr->ip6))
+           {
+             /* valid address for this interface */
+             local_ip_valid = 1;
+           }
+       }
+      else
+       {
+         ip6_main_t *im = &ip6_main;
+         /* *INDENT-OFF* */
+         foreach_ip_interface_address (
+             &im->lookup_main, ia, sw_if_index, 0 /* honor unnumbered */, ({
+               ip6_address_t *x =
+                   ip_interface_address_get_address (&im->lookup_main, ia);
+               if (local_addr->ip6.as_u64[0] == x->as_u64[0] &&
+                   local_addr->ip6.as_u64[1] == x->as_u64[1])
+                 {
+                   /* valid address for this interface */
+                   local_ip_valid = 1;
+                   break;
+                 }
+             }));
+         /* *INDENT-ON* */
+       }
     }
 
   if (!local_ip_valid)
     {
-      BFD_ERR ("address not found on interface");
+      vlib_log_err (bum->log_class,
+                   "local address %U not found on interface with index %u",
+                   format_ip46_address, local_addr, IP46_TYPE_ANY,
+                   sw_if_index);
       return VNET_API_ERROR_ADDRESS_NOT_FOUND_FOR_INTERFACE;
     }
 
   return 0;
 }
 
-vnet_api_error_t bfd_udp_add_session (u32 sw_if_index, u32 desired_min_tx_us,
-                                      u32 required_min_rx_us, u8 detect_mult,
-                                      const ip46_address_t *local_addr,
-                                      const ip46_address_t *peer_addr)
+static vnet_api_error_t
+bfd_udp_find_session_by_api_input (u32 sw_if_index,
+                                  const ip46_address_t * local_addr,
+                                  const ip46_address_t * peer_addr,
+                                  bfd_session_t ** bs_out)
 {
   vnet_api_error_t rv =
-      bfd_udp_validate_api_input (sw_if_index, local_addr, peer_addr);
+    bfd_udp_validate_api_input (sw_if_index, local_addr, peer_addr);
+  if (!rv)
+    {
+      bfd_udp_main_t *bum = &bfd_udp_main;
+      bfd_udp_key_t key;
+      bfd_udp_key_init (&key, sw_if_index, local_addr, peer_addr);
+      bfd_session_t *bs = bfd_lookup_session (bum, &key);
+      if (bs)
+       {
+         *bs_out = bs;
+       }
+      else
+       {
+         vlib_log_err (bum->log_class,
+                       "BFD session not found, sw_if_index=%u, local=%U, peer=%U",
+                       sw_if_index, format_ip46_address, local_addr,
+                       IP46_TYPE_ANY, format_ip46_address, peer_addr,
+                       IP46_TYPE_ANY);
+         return VNET_API_ERROR_BFD_ENOENT;
+       }
+    }
+  return rv;
+}
+
+static vnet_api_error_t
+bfd_api_verify_common (u32 sw_if_index, u32 desired_min_tx_usec,
+                      u32 required_min_rx_usec, u8 detect_mult,
+                      const ip46_address_t * local_addr,
+                      const ip46_address_t * peer_addr)
+{
+  bfd_udp_main_t *bum = &bfd_udp_main;
+  vnet_api_error_t rv =
+    bfd_udp_validate_api_input (sw_if_index, local_addr, peer_addr);
   if (rv)
     {
       return rv;
     }
   if (detect_mult < 1)
     {
-      BFD_ERR ("detect_mult < 1");
+      vlib_log_err (bum->log_class, "detect_mult < 1");
       return VNET_API_ERROR_INVALID_ARGUMENT;
     }
-  if (desired_min_tx_us < 1)
+  if (desired_min_tx_usec < 1)
     {
-      BFD_ERR ("desired_min_tx_us < 1");
+      vlib_log_err (bum->log_class, "desired_min_tx_usec < 1");
       return VNET_API_ERROR_INVALID_ARGUMENT;
     }
-  return bfd_udp_add_session_internal (&bfd_udp_main, sw_if_index,
-                                       desired_min_tx_us, required_min_rx_us,
-                                       detect_mult, local_addr, peer_addr);
+  return 0;
 }
 
-vnet_api_error_t bfd_udp_del_session (u32 sw_if_index,
-                                      const ip46_address_t *local_addr,
-                                      const ip46_address_t *peer_addr)
+static void
+bfd_udp_del_session_internal (vlib_main_t * vm, bfd_session_t * bs)
 {
+  bfd_udp_main_t *bum = &bfd_udp_main;
+  BFD_DBG ("free bfd-udp session, bs_idx=%d", bs->bs_idx);
+  mhash_unset (&bum->bfd_session_idx_by_bfd_key, &bs->udp.key, NULL);
+  adj_unlock (bs->udp.adj_index);
+  switch (bs->transport)
+    {
+    case BFD_TRANSPORT_UDP4:
+      --bum->udp4_sessions_count;
+      if (!bum->udp4_sessions_count)
+       {
+         udp_unregister_dst_port (vm, UDP_DST_PORT_bfd4, 1);
+         udp_unregister_dst_port (vm, UDP_DST_PORT_bfd_echo4, 1);
+       }
+      break;
+    case BFD_TRANSPORT_UDP6:
+      --bum->udp6_sessions_count;
+      if (!bum->udp6_sessions_count)
+       {
+         udp_unregister_dst_port (vm, UDP_DST_PORT_bfd6, 0);
+         udp_unregister_dst_port (vm, UDP_DST_PORT_bfd_echo6, 0);
+       }
+      break;
+    }
+  bfd_put_session (bum->bfd_main, bs);
+}
+
+vnet_api_error_t
+bfd_udp_add_session (u32 sw_if_index, const ip46_address_t * local_addr,
+                    const ip46_address_t * peer_addr,
+                    u32 desired_min_tx_usec, u32 required_min_rx_usec,
+                    u8 detect_mult, u8 is_authenticated, u32 conf_key_id,
+                    u8 bfd_key_id)
+{
+  bfd_main_t *bm = &bfd_main;
+  bfd_lock (bm);
+
   vnet_api_error_t rv =
-      bfd_udp_validate_api_input (sw_if_index, local_addr, peer_addr);
+    bfd_api_verify_common (sw_if_index, desired_min_tx_usec,
+                          required_min_rx_usec, detect_mult,
+                          local_addr, peer_addr);
+  bfd_session_t *bs = NULL;
+  if (!rv)
+    {
+      rv =
+       bfd_udp_add_session_internal (vlib_get_main (), &bfd_udp_main,
+                                     sw_if_index, desired_min_tx_usec,
+                                     required_min_rx_usec, detect_mult,
+                                     local_addr, peer_addr, &bs);
+    }
+  if (!rv && is_authenticated)
+    {
+#if WITH_LIBSSL > 0
+      rv = bfd_auth_activate (bs, conf_key_id, bfd_key_id,
+                             0 /* is not delayed */ );
+#else
+      vlib_log_err (bfd_udp_main.log_class,
+                   "SSL missing, cannot add authenticated BFD session");
+      rv = VNET_API_ERROR_BFD_NOTSUPP;
+#endif
+      if (rv)
+       {
+         bfd_udp_del_session_internal (vlib_get_main (), bs);
+       }
+    }
+  if (!rv)
+    {
+      bfd_session_start (bfd_udp_main.bfd_main, bs);
+    }
+
+  bfd_unlock (bm);
+  return rv;
+}
+
+vnet_api_error_t
+bfd_udp_mod_session (u32 sw_if_index,
+                    const ip46_address_t * local_addr,
+                    const ip46_address_t * peer_addr,
+                    u32 desired_min_tx_usec,
+                    u32 required_min_rx_usec, u8 detect_mult)
+{
+  bfd_session_t *bs = NULL;
+  bfd_main_t *bm = &bfd_main;
+  vnet_api_error_t error;
+  bfd_lock (bm);
+  vnet_api_error_t rv =
+    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
+                                      &bs);
   if (rv)
     {
+      bfd_unlock (bm);
       return rv;
     }
-  bfd_udp_main_t *bum = &bfd_udp_main;
-  vnet_sw_interface_t *sw_if =
-      vnet_get_sw_interface (vnet_get_main (), sw_if_index);
-  bfd_udp_key_t key;
-  memset (&key, 0, sizeof (key));
-  key.sw_if_index = sw_if->sw_if_index;
-  key.local_addr.as_u64[0] = local_addr->as_u64[0];
-  key.local_addr.as_u64[1] = local_addr->as_u64[1];
-  key.peer_addr.as_u64[0] = peer_addr->as_u64[0];
-  key.peer_addr.as_u64[1] = peer_addr->as_u64[1];
-  bfd_session_t *tmp = bfd_lookup_session (bum, &key);
-  if (tmp)
+
+  error = bfd_session_set_params (bfd_udp_main.bfd_main, bs,
+                                 desired_min_tx_usec, required_min_rx_usec,
+                                 detect_mult);
+  bfd_unlock (bm);
+  return error;
+}
+
+vnet_api_error_t
+bfd_udp_del_session (u32 sw_if_index,
+                    const ip46_address_t * local_addr,
+                    const ip46_address_t * peer_addr)
+{
+  bfd_session_t *bs = NULL;
+  bfd_main_t *bm = &bfd_main;
+  bfd_lock (bm);
+  vnet_api_error_t rv =
+    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
+                                      &bs);
+  if (rv)
     {
-      BFD_DBG ("free bfd-udp session, bs_idx=%d", tmp->bs_idx);
-      mhash_unset (&bum->bfd_session_idx_by_bfd_key, &key, NULL);
-      adj_unlock (tmp->udp.adj_index);
-      bfd_put_session (bum->bfd_main, tmp);
+      bfd_unlock (bm);
+      return rv;
     }
-  else
+  bfd_udp_del_session_internal (vlib_get_main (), bs);
+  bfd_unlock (bm);
+  return 0;
+}
+
+vnet_api_error_t
+bfd_udp_session_set_flags (vlib_main_t * vm, u32 sw_if_index,
+                          const ip46_address_t * local_addr,
+                          const ip46_address_t * peer_addr, u8 admin_up_down)
+{
+  bfd_session_t *bs = NULL;
+  bfd_main_t *bm = &bfd_main;
+  bfd_lock (bm);
+  vnet_api_error_t rv =
+    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
+                                      &bs);
+  if (rv)
     {
-      BFD_ERR ("no such session");
-      return VNET_API_ERROR_BFD_NOENT;
+      bfd_unlock (bm);
+      return rv;
     }
+  bfd_session_set_flags (vm, bs, admin_up_down);
+  bfd_unlock (bm);
   return 0;
 }
 
-typedef enum {
+vnet_api_error_t
+bfd_udp_auth_activate (u32 sw_if_index,
+                      const ip46_address_t * local_addr,
+                      const ip46_address_t * peer_addr,
+                      u32 conf_key_id, u8 key_id, u8 is_delayed)
+{
+  bfd_main_t *bm = &bfd_main;
+  bfd_lock (bm);
+  vnet_api_error_t error;
+
+#if WITH_LIBSSL > 0
+  bfd_session_t *bs = NULL;
+  vnet_api_error_t rv =
+    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
+                                      &bs);
+  if (rv)
+    {
+      bfd_unlock (bm);
+      return rv;
+    }
+  error = bfd_auth_activate (bs, conf_key_id, key_id, is_delayed);
+  bfd_unlock (bm);
+  return error;
+#else
+  vlib_log_err (bfd_udp_main->log_class,
+               "SSL missing, cannot activate BFD authentication");
+  bfd_unlock (bm);
+  return VNET_API_ERROR_BFD_NOTSUPP;
+#endif
+}
+
+vnet_api_error_t
+bfd_udp_auth_deactivate (u32 sw_if_index,
+                        const ip46_address_t * local_addr,
+                        const ip46_address_t * peer_addr, u8 is_delayed)
+{
+  bfd_main_t *bm = &bfd_main;
+  vnet_api_error_t error;
+  bfd_lock (bm);
+  bfd_session_t *bs = NULL;
+  vnet_api_error_t rv =
+    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
+                                      &bs);
+  if (rv)
+    {
+      bfd_unlock (bm);
+      return rv;
+    }
+  error = bfd_auth_deactivate (bs, is_delayed);
+  bfd_unlock (bm);
+  return error;
+}
+
+typedef enum
+{
   BFD_UDP_INPUT_NEXT_NORMAL,
-  BFD_UDP_INPUT_NEXT_REPLY,
+  BFD_UDP_INPUT_NEXT_REPLY_ARP,
+  BFD_UDP_INPUT_NEXT_REPLY_REWRITE,
+  BFD_UDP_INPUT_NEXT_REPLY_MIDCHAIN,
   BFD_UDP_INPUT_N_NEXT,
 } bfd_udp_input_next_t;
 
-/* Packet counters */
+/* Packet counters - BFD control frames */
 #define foreach_bfd_udp_error(F)           \
   F (NONE, "good bfd packets (processed)") \
-  F (BAD, "invalid bfd packets")           \
-  F (DISABLED, "bfd packets received on disabled interfaces")
+  F (BAD, "invalid bfd packets")
 
 #define F(sym, string) static char BFD_UDP_ERR_##sym##_STR[] = string;
 foreach_bfd_udp_error (F);
@@ -305,18 +931,51 @@ static char *bfd_udp_error_strings[] = {
 #undef F
 };
 
-typedef enum {
+typedef enum
+{
 #define F(sym, str) BFD_UDP_ERROR_##sym,
   foreach_bfd_udp_error (F)
 #undef F
-      BFD_UDP_N_ERROR,
+    BFD_UDP_N_ERROR,
 } bfd_udp_error_t;
 
-static void bfd_udp4_find_headers (vlib_buffer_t *b, const ip4_header_t **ip4,
-                                   const udp_header_t **udp)
+typedef enum
+{
+  BFD_UDP_ECHO_INPUT_NEXT_NORMAL,
+  BFD_UDP_ECHO_INPUT_NEXT_REPLY_ARP,
+  BFD_UDP_ECHO_INPUT_NEXT_REPLY_REWRITE,
+  BFD_UDP_ECHO_INPUT_N_NEXT,
+} bfd_udp_echo_input_next_t;
+
+/* Packet counters - BFD ECHO packets */
+#define foreach_bfd_udp_echo_error(F)           \
+  F (NONE, "good bfd echo packets (processed)") \
+  F (BAD, "invalid bfd echo packets")
+
+#define F(sym, string) static char BFD_UDP_ECHO_ERR_##sym##_STR[] = string;
+foreach_bfd_udp_echo_error (F);
+#undef F
+
+static char *bfd_udp_echo_error_strings[] = {
+#define F(sym, string) BFD_UDP_ECHO_ERR_##sym##_STR,
+  foreach_bfd_udp_echo_error (F)
+#undef F
+};
+
+typedef enum
+{
+#define F(sym, str) BFD_UDP_ECHO_ERROR_##sym,
+  foreach_bfd_udp_echo_error (F)
+#undef F
+    BFD_UDP_ECHO_N_ERROR,
+} bfd_udp_echo_error_t;
+
+static void
+bfd_udp4_find_headers (vlib_buffer_t * b, ip4_header_t ** ip4,
+                      udp_header_t ** udp)
 {
   /* sanity check first */
-  const i32 start = vnet_buffer (b)->ip.start_of_ip_header;
+  const i32 start = vnet_buffer (b)->l3_hdr_offset;
   if (start < 0 && start < sizeof (b->pre_data))
     {
       BFD_ERR ("Start of ip header is before pre_data, ignoring");
@@ -324,49 +983,48 @@ static void bfd_udp4_find_headers (vlib_buffer_t *b, const ip4_header_t **ip4,
       *udp = NULL;
       return;
     }
-  *ip4 = (ip4_header_t *)(b->data + start);
-  if ((u8 *)*ip4 > (u8 *)vlib_buffer_get_current (b))
+  *ip4 = (ip4_header_t *) (b->data + start);
+  if ((u8 *) * ip4 > (u8 *) vlib_buffer_get_current (b))
     {
       BFD_ERR ("Start of ip header is beyond current data, ignoring");
       *ip4 = NULL;
       *udp = NULL;
       return;
     }
-  *udp = (udp_header_t *)((*ip4) + 1);
+  *udp = (udp_header_t *) ((*ip4) + 1);
 }
 
-static bfd_udp_error_t bfd_udp4_verify_transport (const ip4_header_t *ip4,
-                                                  const udp_header_t *udp,
-                                                  const bfd_session_t *bs)
+static bfd_udp_error_t
+bfd_udp4_verify_transport (const ip4_header_t * ip4,
+                          const udp_header_t * udp, const bfd_session_t * bs)
 {
   const bfd_udp_session_t *bus = &bs->udp;
   const bfd_udp_key_t *key = &bus->key;
   if (ip4->src_address.as_u32 != key->peer_addr.ip4.as_u32)
     {
-      BFD_ERR ("IP src addr mismatch, got %U, expected %U", format_ip4_address,
-               ip4->src_address.as_u32, format_ip4_address,
-               key->peer_addr.ip4.as_u32);
+      BFD_ERR ("IPv4 src addr mismatch, got %U, expected %U",
+              format_ip4_address, ip4->src_address.as_u8, format_ip4_address,
+              key->peer_addr.ip4.as_u8);
       return BFD_UDP_ERROR_BAD;
     }
   if (ip4->dst_address.as_u32 != key->local_addr.ip4.as_u32)
     {
-      BFD_ERR ("IP dst addr mismatch, got %U, expected %U", format_ip4_address,
-               ip4->dst_address.as_u32, format_ip4_address,
-               key->local_addr.ip4.as_u32);
+      BFD_ERR ("IPv4 dst addr mismatch, got %U, expected %U",
+              format_ip4_address, ip4->dst_address.as_u8, format_ip4_address,
+              key->local_addr.ip4.as_u8);
       return BFD_UDP_ERROR_BAD;
     }
   const u8 expected_ttl = 255;
   if (ip4->ttl != expected_ttl)
     {
-      BFD_ERR ("IP unexpected TTL value %d, expected %d", ip4->ttl,
-               expected_ttl);
+      BFD_ERR ("IPv4 unexpected TTL value %u, expected %u", ip4->ttl,
+              expected_ttl);
       return BFD_UDP_ERROR_BAD;
     }
-  if (clib_net_to_host_u16 (udp->src_port) < 49152 ||
-      clib_net_to_host_u16 (udp->src_port) > 65535)
+  if (clib_net_to_host_u16 (udp->src_port) < 49152)
     {
-      BFD_ERR ("Invalid UDP src port %d, out of range <49152,65535>",
-               udp->src_port);
+      BFD_ERR ("Invalid UDP src port %u, out of range <49152,65535>",
+              udp->src_port);
     }
   return BFD_UDP_ERROR_NONE;
 }
@@ -377,43 +1035,43 @@ typedef struct
   bfd_pkt_t pkt;
 } bfd_rpc_update_t;
 
-static void bfd_rpc_update_session_cb (const bfd_rpc_update_t *a)
-{
-  bfd_consume_pkt (bfd_udp_main.bfd_main, &a->pkt, a->bs_idx);
-}
-
-static void bfd_rpc_update_session (u32 bs_idx, const bfd_pkt_t *pkt)
+static void
+bfd_rpc_update_session (vlib_main_t * vm, u32 bs_idx, const bfd_pkt_t * pkt)
 {
-  /* packet length was already verified to be correct by the caller */
-  const u32 data_size = sizeof (bfd_rpc_update_t) -
-                        STRUCT_SIZE_OF (bfd_rpc_update_t, pkt) +
-                        pkt->head.length;
-  u8 data[data_size];
-  bfd_rpc_update_t *update = (bfd_rpc_update_t *)data;
-  update->bs_idx = bs_idx;
-  clib_memcpy (&update->pkt, pkt, pkt->head.length);
-  vl_api_rpc_call_main_thread (bfd_rpc_update_session_cb, data, data_size);
+  bfd_main_t *bm = &bfd_main;
+  bfd_lock (bm);
+  bfd_consume_pkt (vm, bm, pkt, bs_idx);
+  bfd_unlock (bm);
 }
 
-static bfd_udp_error_t bfd_udp4_scan (vlib_main_t *vm, vlib_node_runtime_t *rt,
-                                      vlib_buffer_t *b, bfd_session_t **bs_out)
+static bfd_udp_error_t
+bfd_udp4_scan (vlib_main_t * vm, vlib_node_runtime_t * rt,
+              vlib_buffer_t * b, bfd_session_t ** bs_out)
 {
   const bfd_pkt_t *pkt = vlib_buffer_get_current (b);
   if (sizeof (*pkt) > b->current_length)
     {
-      BFD_ERR (
-          "Payload size %d too small to hold bfd packet of minimum size %d",
-          b->current_length, sizeof (*pkt));
+      BFD_ERR
+       ("Payload size %d too small to hold bfd packet of minimum size %d",
+        b->current_length, sizeof (*pkt));
       return BFD_UDP_ERROR_BAD;
     }
-  const ip4_header_t *ip4;
-  const udp_header_t *udp;
+  ip4_header_t *ip4;
+  udp_header_t *udp;
   bfd_udp4_find_headers (b, &ip4, &udp);
   if (!ip4 || !udp)
     {
       BFD_ERR ("Couldn't find ip4 or udp header");
       return BFD_UDP_ERROR_BAD;
     }
+  const u32 udp_payload_length = udp->length - sizeof (*udp);
+  if (pkt->head.length > udp_payload_length)
+    {
+      BFD_ERR
+       ("BFD packet length is larger than udp payload length (%u > %u)",
+        pkt->head.length, udp_payload_length);
+      return BFD_UDP_ERROR_BAD;
+    }
   if (!bfd_verify_pkt_common (pkt))
     {
       return BFD_UDP_ERROR_BAD;
@@ -422,20 +1080,20 @@ static bfd_udp_error_t bfd_udp4_scan (vlib_main_t *vm, vlib_node_runtime_t *rt,
   if (pkt->your_disc)
     {
       BFD_DBG ("Looking up BFD session using discriminator %u",
-               pkt->your_disc);
+              pkt->your_disc);
       bs = bfd_find_session_by_disc (bfd_udp_main.bfd_main, pkt->your_disc);
     }
   else
     {
       bfd_udp_key_t key;
-      memset (&key, 0, sizeof (key));
+      clib_memset (&key, 0, sizeof (key));
       key.sw_if_index = vnet_buffer (b)->sw_if_index[VLIB_RX];
       key.local_addr.ip4.as_u32 = ip4->dst_address.as_u32;
       key.peer_addr.ip4.as_u32 = ip4->src_address.as_u32;
       BFD_DBG ("Looking up BFD session using key (sw_if_index=%u, local=%U, "
-               "peer=%U)",
-               key.sw_if_index, format_ip4_address, key.local_addr.ip4.as_u8,
-               format_ip4_address, key.peer_addr.ip4.as_u8);
+              "peer=%U)",
+              key.sw_if_index, format_ip4_address, key.local_addr.ip4.as_u8,
+              format_ip4_address, key.peer_addr.ip4.as_u8);
       bs = bfd_lookup_session (&bfd_udp_main, &key);
     }
   if (!bs)
@@ -444,8 +1102,9 @@ static bfd_udp_error_t bfd_udp4_scan (vlib_main_t *vm, vlib_node_runtime_t *rt,
       return BFD_UDP_ERROR_BAD;
     }
   BFD_DBG ("BFD session found, bs_idx=%u", bs->bs_idx);
-  if (!bfd_verify_pkt_session (pkt, b->current_length, bs))
+  if (!bfd_verify_pkt_auth (vm, pkt, b->current_length, bs))
     {
+      BFD_ERR ("Packet verification failed, dropping packet");
       return BFD_UDP_ERROR_BAD;
     }
   bfd_udp_error_t err;
@@ -453,29 +1112,169 @@ static bfd_udp_error_t bfd_udp4_scan (vlib_main_t *vm, vlib_node_runtime_t *rt,
     {
       return err;
     }
-  bfd_rpc_update_session (bs->bs_idx, pkt);
+  bfd_rpc_update_session (vm, bs->bs_idx, pkt);
   *bs_out = bs;
   return BFD_UDP_ERROR_NONE;
 }
 
-static bfd_udp_error_t bfd_udp6_scan (vlib_main_t *vm, vlib_buffer_t *b)
+static void
+bfd_udp6_find_headers (vlib_buffer_t * b, ip6_header_t ** ip6,
+                      udp_header_t ** udp)
 {
-  /* TODO */
-  return BFD_UDP_ERROR_BAD;
+  /* sanity check first */
+  const i32 start = vnet_buffer (b)->l3_hdr_offset;
+  if (start < 0 && start < sizeof (b->pre_data))
+    {
+      BFD_ERR ("Start of ip header is before pre_data, ignoring");
+      *ip6 = NULL;
+      *udp = NULL;
+      return;
+    }
+  *ip6 = (ip6_header_t *) (b->data + start);
+  if ((u8 *) * ip6 > (u8 *) vlib_buffer_get_current (b))
+    {
+      BFD_ERR ("Start of ip header is beyond current data, ignoring");
+      *ip6 = NULL;
+      *udp = NULL;
+      return;
+    }
+  if ((*ip6)->protocol != IP_PROTOCOL_UDP)
+    {
+      BFD_ERR ("Unexpected protocol in IPv6 header '%u', expected '%u' (== "
+              "IP_PROTOCOL_UDP)", (*ip6)->protocol, IP_PROTOCOL_UDP);
+      *ip6 = NULL;
+      *udp = NULL;
+      return;
+    }
+  *udp = (udp_header_t *) ((*ip6) + 1);
+}
+
+static bfd_udp_error_t
+bfd_udp6_verify_transport (const ip6_header_t * ip6,
+                          const udp_header_t * udp, const bfd_session_t * bs)
+{
+  const bfd_udp_session_t *bus = &bs->udp;
+  const bfd_udp_key_t *key = &bus->key;
+  if (ip6->src_address.as_u64[0] != key->peer_addr.ip6.as_u64[0] &&
+      ip6->src_address.as_u64[1] != key->peer_addr.ip6.as_u64[1])
+    {
+      BFD_ERR ("IP src addr mismatch, got %U, expected %U",
+              format_ip6_address, ip6, format_ip6_address,
+              &key->peer_addr.ip6);
+      return BFD_UDP_ERROR_BAD;
+    }
+  if (ip6->dst_address.as_u64[0] != key->local_addr.ip6.as_u64[0] &&
+      ip6->dst_address.as_u64[1] != key->local_addr.ip6.as_u64[1])
+    {
+      BFD_ERR ("IP dst addr mismatch, got %U, expected %U",
+              format_ip6_address, ip6, format_ip6_address,
+              &key->local_addr.ip6);
+      return BFD_UDP_ERROR_BAD;
+    }
+  const u8 expected_hop_limit = 255;
+  if (ip6->hop_limit != expected_hop_limit)
+    {
+      BFD_ERR ("IPv6 unexpected hop-limit value %u, expected %u",
+              ip6->hop_limit, expected_hop_limit);
+      return BFD_UDP_ERROR_BAD;
+    }
+  if (clib_net_to_host_u16 (udp->src_port) < 49152)
+    {
+      BFD_ERR ("Invalid UDP src port %u, out of range <49152,65535>",
+              udp->src_port);
+    }
+  return BFD_UDP_ERROR_NONE;
+}
+
+static bfd_udp_error_t
+bfd_udp6_scan (vlib_main_t * vm, vlib_node_runtime_t * rt,
+              vlib_buffer_t * b, bfd_session_t ** bs_out)
+{
+  const bfd_pkt_t *pkt = vlib_buffer_get_current (b);
+  if (sizeof (*pkt) > b->current_length)
+    {
+      BFD_ERR
+       ("Payload size %d too small to hold bfd packet of minimum size %d",
+        b->current_length, sizeof (*pkt));
+      return BFD_UDP_ERROR_BAD;
+    }
+  ip6_header_t *ip6;
+  udp_header_t *udp;
+  bfd_udp6_find_headers (b, &ip6, &udp);
+  if (!ip6 || !udp)
+    {
+      BFD_ERR ("Couldn't find ip6 or udp header");
+      return BFD_UDP_ERROR_BAD;
+    }
+  const u32 udp_payload_length = udp->length - sizeof (*udp);
+  if (pkt->head.length > udp_payload_length)
+    {
+      BFD_ERR
+       ("BFD packet length is larger than udp payload length (%u > %u)",
+        pkt->head.length, udp_payload_length);
+      return BFD_UDP_ERROR_BAD;
+    }
+  if (!bfd_verify_pkt_common (pkt))
+    {
+      return BFD_UDP_ERROR_BAD;
+    }
+  bfd_session_t *bs = NULL;
+  if (pkt->your_disc)
+    {
+      BFD_DBG ("Looking up BFD session using discriminator %u",
+              pkt->your_disc);
+      bs = bfd_find_session_by_disc (bfd_udp_main.bfd_main, pkt->your_disc);
+    }
+  else
+    {
+      bfd_udp_key_t key;
+      clib_memset (&key, 0, sizeof (key));
+      key.sw_if_index = vnet_buffer (b)->sw_if_index[VLIB_RX];
+      key.local_addr.ip6.as_u64[0] = ip6->dst_address.as_u64[0];
+      key.local_addr.ip6.as_u64[1] = ip6->dst_address.as_u64[1];
+      key.peer_addr.ip6.as_u64[0] = ip6->src_address.as_u64[0];
+      key.peer_addr.ip6.as_u64[1] = ip6->src_address.as_u64[1];
+      BFD_DBG ("Looking up BFD session using key (sw_if_index=%u, local=%U, "
+              "peer=%U)",
+              key.sw_if_index, format_ip6_address, &key.local_addr,
+              format_ip6_address, &key.peer_addr);
+      bs = bfd_lookup_session (&bfd_udp_main, &key);
+    }
+  if (!bs)
+    {
+      BFD_ERR ("BFD session lookup failed - no session matches BFD pkt");
+      return BFD_UDP_ERROR_BAD;
+    }
+  BFD_DBG ("BFD session found, bs_idx=%u", bs->bs_idx);
+  if (!bfd_verify_pkt_auth (vm, pkt, b->current_length, bs))
+    {
+      BFD_ERR ("Packet verification failed, dropping packet");
+      return BFD_UDP_ERROR_BAD;
+    }
+  bfd_udp_error_t err;
+  if (BFD_UDP_ERROR_NONE != (err = bfd_udp6_verify_transport (ip6, udp, bs)))
+    {
+      return err;
+    }
+  bfd_rpc_update_session (vm, bs->bs_idx, pkt);
+  *bs_out = bs;
+  return BFD_UDP_ERROR_NONE;
 }
 
 /*
  * Process a frame of bfd packets
  * Expect 1 packet / frame
  */
-static uword bfd_udp_input (vlib_main_t *vm, vlib_node_runtime_t *rt,
-                            vlib_frame_t *f, int is_ipv6)
+static uword
+bfd_udp_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
+              vlib_frame_t * f, int is_ipv6)
 {
   u32 n_left_from, *from;
   bfd_input_trace_t *t0;
+  bfd_main_t *bm = &bfd_main;
 
-  from = vlib_frame_vector_args (f); /* array of buffer indices */
-  n_left_from = f->n_vectors;        /* number of buffer indices */
+  from = vlib_frame_vector_args (f);   /* array of buffer indices */
+  n_left_from = f->n_vectors;  /* number of buffer indices */
 
   while (n_left_from > 0)
     {
@@ -490,49 +1289,72 @@ static uword bfd_udp_input (vlib_main_t *vm, vlib_node_runtime_t *rt,
 
       /* If this pkt is traced, snapshot the data */
       if (b0->flags & VLIB_BUFFER_IS_TRACED)
-        {
-          int len;
-          t0 = vlib_add_trace (vm, rt, b0, sizeof (*t0));
-          len = (b0->current_length < sizeof (t0->data)) ? b0->current_length
-                                                         : sizeof (t0->data);
-          t0->len = len;
-          clib_memcpy (t0->data, vlib_buffer_get_current (b0), len);
-        }
+       {
+         int len;
+         t0 = vlib_add_trace (vm, rt, b0, sizeof (*t0));
+         len = (b0->current_length < sizeof (t0->data)) ? b0->current_length
+           : sizeof (t0->data);
+         t0->len = len;
+         clib_memcpy_fast (t0->data, vlib_buffer_get_current (b0), len);
+       }
 
       /* scan this bfd pkt. error0 is the counter index to bmp */
+      bfd_lock (bm);
       if (is_ipv6)
-        {
-          error0 = bfd_udp6_scan (vm, b0);
-        }
+       {
+         error0 = bfd_udp6_scan (vm, rt, b0, &bs);
+       }
       else
-        {
-          error0 = bfd_udp4_scan (vm, rt, b0, &bs);
-        }
+       {
+         error0 = bfd_udp4_scan (vm, rt, b0, &bs);
+       }
       b0->error = rt->errors[error0];
 
       next0 = BFD_UDP_INPUT_NEXT_NORMAL;
       if (BFD_UDP_ERROR_NONE == error0)
-        {
-          /* if everything went fine, check for poll bit, if present, re-use
-             the buffer and based on (now updated) session parameters, send the
-             final packet back */
-          const bfd_pkt_t *pkt = vlib_buffer_get_current (b0);
-          if (bfd_pkt_get_poll (pkt))
-            {
-              bfd_send_final (vm, b0, bs);
-              if (is_ipv6)
-                {
-                  vlib_node_increment_counter (vm, bfd_udp6_input_node.index,
-                                               b0->error, 1);
-                }
-              else
-                {
-                  vlib_node_increment_counter (vm, bfd_udp4_input_node.index,
-                                               b0->error, 1);
-                }
-              next0 = BFD_UDP_INPUT_NEXT_REPLY;
-            }
-        }
+       {
+         /*
+          *  if everything went fine, check for poll bit, if present, re-use
+          *  the buffer and based on (now updated) session parameters, send
+          *  the final packet back
+          */
+         const bfd_pkt_t *pkt = vlib_buffer_get_current (b0);
+         if (bfd_pkt_get_poll (pkt))
+           {
+             b0->current_data = 0;
+             b0->current_length = 0;
+             bfd_init_final_control_frame (vm, b0, bfd_udp_main.bfd_main, bs,
+                                           0);
+             if (is_ipv6)
+               {
+                 vlib_node_increment_counter (vm, bfd_udp6_input_node.index,
+                                              b0->error, 1);
+               }
+             else
+               {
+                 vlib_node_increment_counter (vm, bfd_udp4_input_node.index,
+                                              b0->error, 1);
+               }
+             const bfd_udp_session_t *bus = &bs->udp;
+             ip_adjacency_t *adj = adj_get (bus->adj_index);
+             switch (adj->lookup_next_index)
+               {
+               case IP_LOOKUP_NEXT_ARP:
+                 next0 = BFD_UDP_INPUT_NEXT_REPLY_ARP;
+                 break;
+               case IP_LOOKUP_NEXT_REWRITE:
+                 next0 = BFD_UDP_INPUT_NEXT_REPLY_REWRITE;
+                 break;
+               case IP_LOOKUP_NEXT_MIDCHAIN:
+                 next0 = BFD_UDP_INPUT_NEXT_REPLY_MIDCHAIN;
+                 break;
+               default:
+                 /* drop */
+                 break;
+               }
+           }
+       }
+      bfd_unlock (bm);
       vlib_set_next_frame_buffer (vm, rt, next0, bi0);
 
       from += 1;
@@ -542,8 +1364,8 @@ static uword bfd_udp_input (vlib_main_t *vm, vlib_node_runtime_t *rt,
   return f->n_vectors;
 }
 
-static uword bfd_udp4_input (vlib_main_t *vm, vlib_node_runtime_t *rt,
-                             vlib_frame_t *f)
+static uword
+bfd_udp4_input (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
 {
   return bfd_udp_input (vm, rt, f, 0);
 }
@@ -567,13 +1389,15 @@ VLIB_REGISTER_NODE (bfd_udp4_input_node, static) = {
   .next_nodes =
       {
               [BFD_UDP_INPUT_NEXT_NORMAL] = "error-drop",
-              [BFD_UDP_INPUT_NEXT_REPLY] = "ip4-lookup",
+              [BFD_UDP_INPUT_NEXT_REPLY_ARP] = "ip4-arp",
+              [BFD_UDP_INPUT_NEXT_REPLY_REWRITE] = "ip4-lookup",
+              [BFD_UDP_INPUT_NEXT_REPLY_MIDCHAIN] = "ip4-midchain",
       },
 };
 /* *INDENT-ON* */
 
-static uword bfd_udp6_input (vlib_main_t *vm, vlib_node_runtime_t *rt,
-                             vlib_frame_t *f)
+static uword
+bfd_udp6_input (vlib_main_t * vm, vlib_node_runtime_t * rt, vlib_frame_t * f)
 {
   return bfd_udp_input (vm, rt, f, 1);
 }
@@ -594,47 +1418,237 @@ VLIB_REGISTER_NODE (bfd_udp6_input_node, static) = {
   .next_nodes =
       {
               [BFD_UDP_INPUT_NEXT_NORMAL] = "error-drop",
-              [BFD_UDP_INPUT_NEXT_REPLY] = "ip6-lookup",
+              [BFD_UDP_INPUT_NEXT_REPLY_ARP] = "ip6-discover-neighbor",
+              [BFD_UDP_INPUT_NEXT_REPLY_REWRITE] = "ip6-lookup",
+              [BFD_UDP_INPUT_NEXT_REPLY_MIDCHAIN] = "ip6-midchain",
       },
 };
 /* *INDENT-ON* */
 
-static clib_error_t *bfd_sw_interface_up_down (vnet_main_t *vnm,
-                                               u32 sw_if_index, u32 flags)
+/*
+ * Process a frame of bfd echo packets
+ * Expect 1 packet / frame
+ */
+static uword
+bfd_udp_echo_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
+                   vlib_frame_t * f, int is_ipv6)
 {
-  // vnet_hw_interface_t *hi = vnet_get_sup_hw_interface (vnm, sw_if_index);
-  if (!(flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP))
+  u32 n_left_from, *from;
+  bfd_input_trace_t *t0;
+  bfd_main_t *bm = &bfd_main;
+
+  from = vlib_frame_vector_args (f);   /* array of buffer indices */
+  n_left_from = f->n_vectors;  /* number of buffer indices */
+
+  while (n_left_from > 0)
     {
-      /* TODO */
+      u32 bi0;
+      vlib_buffer_t *b0;
+      u32 next0;
+
+      bi0 = from[0];
+      b0 = vlib_get_buffer (vm, bi0);
+
+      /* If this pkt is traced, snapshot the data */
+      if (b0->flags & VLIB_BUFFER_IS_TRACED)
+       {
+         int len;
+         t0 = vlib_add_trace (vm, rt, b0, sizeof (*t0));
+         len = (b0->current_length < sizeof (t0->data)) ? b0->current_length
+           : sizeof (t0->data);
+         t0->len = len;
+         clib_memcpy_fast (t0->data, vlib_buffer_get_current (b0), len);
+       }
+
+      bfd_lock (bm);
+      if (bfd_consume_echo_pkt (vm, bfd_udp_main.bfd_main, b0))
+       {
+         b0->error = rt->errors[BFD_UDP_ERROR_NONE];
+         next0 = BFD_UDP_ECHO_INPUT_NEXT_NORMAL;
+       }
+      else
+       {
+         /* loop back the packet */
+         b0->error = rt->errors[BFD_UDP_ERROR_NONE];
+         if (is_ipv6)
+           {
+             vlib_node_increment_counter (vm, bfd_udp_echo6_input_node.index,
+                                          b0->error, 1);
+           }
+         else
+           {
+             vlib_node_increment_counter (vm, bfd_udp_echo4_input_node.index,
+                                          b0->error, 1);
+           }
+         next0 = BFD_UDP_ECHO_INPUT_NEXT_REPLY_REWRITE;
+       }
+
+      bfd_unlock (bm);
+      vlib_set_next_frame_buffer (vm, rt, next0, bi0);
+
+      from += 1;
+      n_left_from -= 1;
     }
-  return 0;
+
+  return f->n_vectors;
 }
 
-VNET_SW_INTERFACE_ADMIN_UP_DOWN_FUNCTION (bfd_sw_interface_up_down);
+static uword
+bfd_udp_echo4_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
+                    vlib_frame_t * f)
+{
+  return bfd_udp_echo_input (vm, rt, f, 0);
+}
 
-static clib_error_t *bfd_hw_interface_up_down (vnet_main_t *vnm,
-                                               u32 hw_if_index, u32 flags)
+u8 *
+bfd_echo_input_format_trace (u8 * s, va_list * args)
 {
-  if (flags & VNET_HW_INTERFACE_FLAG_LINK_UP)
+  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
+  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
+  const bfd_udp_echo_input_trace_t *t =
+    va_arg (*args, bfd_udp_echo_input_trace_t *);
+  if (t->len > STRUCT_SIZE_OF (bfd_pkt_t, head))
     {
-      /* TODO */
+      s = format (s, "BFD ECHO:\n");
+      s = format (s, "    data: %U", format_hexdump, t->data, t->len);
     }
+
+  return s;
+}
+
+/*
+ * bfd input graph node declaration
+ */
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (bfd_udp_echo4_input_node, static) = {
+  .function = bfd_udp_echo4_input,
+  .name = "bfd-udp-echo4-input",
+  .vector_size = sizeof (u32),
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = BFD_UDP_ECHO_N_ERROR,
+  .error_strings = bfd_udp_error_strings,
+
+  .format_trace = bfd_echo_input_format_trace,
+
+  .n_next_nodes = BFD_UDP_ECHO_INPUT_N_NEXT,
+  .next_nodes =
+      {
+              [BFD_UDP_ECHO_INPUT_NEXT_NORMAL] = "error-drop",
+              [BFD_UDP_ECHO_INPUT_NEXT_REPLY_ARP] = "ip4-arp",
+              [BFD_UDP_ECHO_INPUT_NEXT_REPLY_REWRITE] = "ip4-lookup",
+      },
+};
+/* *INDENT-ON* */
+
+static uword
+bfd_udp_echo6_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
+                    vlib_frame_t * f)
+{
+  return bfd_udp_echo_input (vm, rt, f, 1);
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (bfd_udp_echo6_input_node, static) = {
+  .function = bfd_udp_echo6_input,
+  .name = "bfd-udp-echo6-input",
+  .vector_size = sizeof (u32),
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = BFD_UDP_ECHO_N_ERROR,
+  .error_strings = bfd_udp_echo_error_strings,
+
+  .format_trace = bfd_echo_input_format_trace,
+
+  .n_next_nodes = BFD_UDP_ECHO_INPUT_N_NEXT,
+  .next_nodes =
+      {
+              [BFD_UDP_ECHO_INPUT_NEXT_NORMAL] = "error-drop",
+              [BFD_UDP_ECHO_INPUT_NEXT_REPLY_ARP] = "ip6-discover-neighbor",
+              [BFD_UDP_ECHO_INPUT_NEXT_REPLY_REWRITE] = "ip6-lookup",
+      },
+};
+
+/* *INDENT-ON* */
+
+static clib_error_t *
+bfd_udp_sw_if_add_del (vnet_main_t * vnm, u32 sw_if_index, u32 is_create)
+{
+  bfd_session_t **to_be_freed = NULL;
+  bfd_udp_main_t *bum = &bfd_udp_main;
+  BFD_DBG ("sw_if_add_del called, sw_if_index=%u, is_create=%u", sw_if_index,
+          is_create);
+  if (!is_create)
+    {
+      bfd_session_t *bs;
+      pool_foreach (bs, bfd_udp_main.bfd_main->sessions,
+                   {
+                   if (bs->transport != BFD_TRANSPORT_UDP4 &&
+                       bs->transport != BFD_TRANSPORT_UDP6)
+                   {
+                   continue;}
+                   if (bs->udp.key.sw_if_index != sw_if_index)
+                   {
+                   continue;}
+                   vec_add1 (to_be_freed, bs);}
+      );
+    }
+  bfd_session_t **bs;
+  vec_foreach (bs, to_be_freed)
+  {
+    vlib_log_notice (bum->log_class,
+                    "removal of sw_if_index=%u forces removal of bfd session "
+                    "with bs_idx=%u", sw_if_index, (*bs)->bs_idx);
+    bfd_session_set_flags (vlib_get_main (), *bs, 0);
+    bfd_udp_del_session_internal (vlib_get_main (), *bs);
+  }
   return 0;
 }
 
-VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION (bfd_hw_interface_up_down);
+VNET_SW_INTERFACE_ADD_DEL_FUNCTION (bfd_udp_sw_if_add_del);
 
 /*
  * setup function
  */
-static clib_error_t *bfd_udp_init (vlib_main_t *vm)
+static clib_error_t *
+bfd_udp_init (vlib_main_t * vm)
 {
+  bfd_udp_main.udp4_sessions_count = 0;
+  bfd_udp_main.udp6_sessions_count = 0;
   mhash_init (&bfd_udp_main.bfd_session_idx_by_bfd_key, sizeof (uword),
-              sizeof (bfd_udp_key_t));
+             sizeof (bfd_udp_key_t));
   bfd_udp_main.bfd_main = &bfd_main;
-  udp_register_dst_port (vm, UDP_DST_PORT_bfd4, bfd_udp4_input_node.index, 1);
-  udp_register_dst_port (vm, UDP_DST_PORT_bfd6, bfd_udp6_input_node.index, 0);
+  bfd_udp_main.vnet_main = vnet_get_main ();
+  vlib_node_t *node = vlib_get_node_by_name (vm, (u8 *) "ip4-arp");
+  ASSERT (node);
+  bfd_udp_main.ip4_arp_idx = node->index;
+  node = vlib_get_node_by_name (vm, (u8 *) "ip6-discover-neighbor");
+  ASSERT (node);
+  bfd_udp_main.ip6_ndp_idx = node->index;
+  node = vlib_get_node_by_name (vm, (u8 *) "ip4-rewrite");
+  ASSERT (node);
+  bfd_udp_main.ip4_rewrite_idx = node->index;
+  node = vlib_get_node_by_name (vm, (u8 *) "ip6-rewrite");
+  ASSERT (node);
+  bfd_udp_main.ip6_rewrite_idx = node->index;
+  node = vlib_get_node_by_name (vm, (u8 *) "ip4-midchain");
+  ASSERT (node);
+  bfd_udp_main.ip4_midchain_idx = node->index;
+  node = vlib_get_node_by_name (vm, (u8 *) "ip6-midchain");
+  ASSERT (node);
+  bfd_udp_main.ip6_midchain_idx = node->index;
+
+  bfd_udp_main.log_class = vlib_log_register_class ("bfd", "udp");
+  vlib_log_debug (bfd_udp_main.log_class, "initialized");
   return 0;
 }
 
 VLIB_INIT_FUNCTION (bfd_udp_init);
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */