bfd: use tw_timer_template instead of legacy wheel
[vpp.git] / src / vnet / bfd / bfd_udp.c
index 8519009..0edf8a8 100644 (file)
  * 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>
@@ -38,6 +46,30 @@ 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;
@@ -47,6 +79,81 @@ static vlib_node_registration_t bfd_udp_echo6_input_node;
 
 bfd_udp_main_t bfd_udp_main;
 
+vnet_api_error_t
+bfd_udp_set_echo_source (u32 sw_if_index)
+{
+  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)
 {
@@ -61,16 +168,100 @@ bfd_udp_bs_idx_to_sport (u32 bs_idx)
   return 49152 + bs_idx % (65535 - 49152 + 1);
 }
 
+int
+bfd_udp_get_echo_src_ip4 (ip4_address_t * addr)
+{
+  if (!bfd_udp_main.echo_source_is_set)
+    {
+      BFD_ERR ("cannot find ip4 address, echo source not set");
+      return 0;
+    }
+  ip_interface_address_t *ia = NULL;
+  ip4_main_t *im = &ip4_main;
+
+  /* *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;
+}
+
+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;
+
+  /* *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_add_udp4_transport (vlib_main_t * vm, vlib_buffer_t * b,
-                       const bfd_session_t * bs)
+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);
 
-  b->flags |= VNET_BUFFER_LOCALLY_ORIGINATED;
+  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;
@@ -79,16 +270,28 @@ bfd_add_udp4_transport (vlib_main_t * vm, vlib_buffer_t * b,
   ip4_udp_headers *headers = NULL;
   vlib_buffer_advance (b, -sizeof (*headers));
   headers = vlib_buffer_get_current (b);
-  memset (headers, 0, sizeof (*headers));
+  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->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.src_port =
     clib_host_to_net_u16 (bfd_udp_bs_idx_to_sport (bs->bs_idx));
-  headers->udp.dst_port = clib_host_to_net_u16 (UDP_DST_PORT_bfd4);
+  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
+    {
+      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);
@@ -98,18 +301,22 @@ bfd_add_udp4_transport (vlib_main_t * vm, vlib_buffer_t * b,
 
   const u16 udp_length = ip_length - (sizeof (headers->ip4));
   headers->udp.length = clib_host_to_net_u16 (udp_length);
+  return 1;
 }
 
-void
-bfd_add_udp6_transport (vlib_main_t * vm, vlib_buffer_t * b,
-                       const bfd_session_t * bs)
+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_LOCALLY_ORIGINATED;
+  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
   {
     ip6_header_t ip6;
@@ -118,19 +325,33 @@ bfd_add_udp6_transport (vlib_main_t * vm, vlib_buffer_t * b,
   ip6_udp_headers *headers = NULL;
   vlib_buffer_advance (b, -sizeof (*headers));
   headers = vlib_buffer_get_current (b);
-  memset (headers, 0, sizeof (*headers));
+  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;
-  clib_memcpy (&headers->ip6.src_address, &key->local_addr.ip6,
-              sizeof (headers->ip6.src_address));
-  clib_memcpy (&headers->ip6.dst_address, &key->peer_addr.ip6,
-              sizeof (headers->ip6.dst_address));
-
   headers->udp.src_port =
     clib_host_to_net_u16 (bfd_udp_bs_idx_to_sport (bs->bs_idx));
-  headers->udp.dst_port = clib_host_to_net_u16 (UDP_DST_PORT_bfd6);
+  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 =
@@ -147,6 +368,94 @@ bfd_add_udp6_transport (vlib_main_t * vm, vlib_buffer_t * b,
     {
       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;
+}
+
+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 *
@@ -165,7 +474,7 @@ 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)
 {
-  memset (key, 0, sizeof (*key));
+  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];
@@ -174,28 +483,33 @@ bfd_udp_key_init (bfd_udp_key_t * key, u32 sw_if_index,
 }
 
 static vnet_api_error_t
-bfd_udp_add_session_internal (bfd_udp_main_t * bum, u32 sw_if_index,
-                             u32 desired_min_tx_usec,
+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)
 {
   /* 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;
   bfd_udp_key_init (key, sw_if_index, local_addr, peer_addr);
   const bfd_session_t *tmp = bfd_lookup_session (bum, key);
   if (tmp)
     {
-      clib_warning ("duplicate bfd-udp session, existing bs_idx=%d",
+      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;
@@ -205,6 +519,8 @@ bfd_udp_add_session_internal (bfd_udp_main_t * bum, u32 sw_if_index,
           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,
@@ -213,6 +529,14 @@ bfd_udp_add_session_internal (bfd_udp_main_t * bum, u32 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);
+      ++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
     {
@@ -222,6 +546,14 @@ bfd_udp_add_session_internal (bfd_udp_main_t * bum, u32 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);
+      ++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,
@@ -233,20 +565,24 @@ 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)
     {
-      clib_warning ("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))
        {
-         clib_warning ("IP family mismatch");
+         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;
@@ -269,29 +605,47 @@ bfd_udp_validate_api_input (u32 sw_if_index,
     {
       if (ip46_address_is_ip4 (peer_addr))
        {
-         clib_warning ("IP family mismatch");
+         vlib_log_err (bum->log_class,
+                       "IP family mismatch (local is ipv6, peer is ipv4)");
          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* */
+
+      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)
     {
-      clib_warning ("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;
     }
 
@@ -318,10 +672,11 @@ bfd_udp_find_session_by_api_input (u32 sw_if_index,
        }
       else
        {
-         clib_warning
-           ("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);
+         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;
        }
     }
@@ -334,6 +689,7 @@ bfd_api_verify_common (u32 sw_if_index, u32 desired_min_tx_usec,
                       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)
@@ -342,24 +698,43 @@ bfd_api_verify_common (u32 sw_if_index, u32 desired_min_tx_usec,
     }
   if (detect_mult < 1)
     {
-      clib_warning ("detect_mult < 1");
+      vlib_log_err (bum->log_class, "detect_mult < 1");
       return VNET_API_ERROR_INVALID_ARGUMENT;
     }
   if (desired_min_tx_usec < 1)
     {
-      clib_warning ("desired_min_tx_usec < 1");
+      vlib_log_err (bum->log_class, "desired_min_tx_usec < 1");
       return VNET_API_ERROR_INVALID_ARGUMENT;
     }
   return 0;
 }
 
 static void
-bfd_udp_del_session_internal (bfd_session_t * bs)
+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);
 }
 
@@ -370,6 +745,9 @@ bfd_udp_add_session (u32 sw_if_index, const ip46_address_t * local_addr,
                     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_api_verify_common (sw_if_index, desired_min_tx_usec,
                           required_min_rx_usec, detect_mult,
@@ -378,8 +756,8 @@ bfd_udp_add_session (u32 sw_if_index, const ip46_address_t * local_addr,
   if (!rv)
     {
       rv =
-       bfd_udp_add_session_internal (&bfd_udp_main, sw_if_index,
-                                     desired_min_tx_usec,
+       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);
     }
@@ -389,12 +767,13 @@ bfd_udp_add_session (u32 sw_if_index, const ip46_address_t * local_addr,
       rv = bfd_auth_activate (bs, conf_key_id, bfd_key_id,
                              0 /* is not delayed */ );
 #else
-      clib_warning ("SSL missing, cannot add authenticated BFD session");
+      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 (bs);
+         bfd_udp_del_session_internal (vlib_get_main (), bs);
        }
     }
   if (!rv)
@@ -402,6 +781,7 @@ bfd_udp_add_session (u32 sw_if_index, const ip46_address_t * local_addr,
       bfd_session_start (bfd_udp_main.bfd_main, bs);
     }
 
+  bfd_unlock (bm);
   return rv;
 }
 
@@ -413,17 +793,23 @@ bfd_udp_mod_session (u32 sw_if_index,
                     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;
     }
 
-  return bfd_session_set_params (bfd_udp_main.bfd_main, bs,
-                                desired_min_tx_usec, required_min_rx_usec,
-                                detect_mult);
+  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
@@ -432,123 +818,40 @@ bfd_udp_del_session (u32 sw_if_index,
                     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_unlock (bm);
       return rv;
     }
-  bfd_udp_del_session_internal (bs);
+  bfd_udp_del_session_internal (vlib_get_main (), bs);
+  bfd_unlock (bm);
   return 0;
 }
 
 vnet_api_error_t
-bfd_udp_session_set_flags (u32 sw_if_index,
+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_unlock (bm);
       return rv;
     }
-  bfd_session_set_flags (bs, admin_up_down);
-  return 0;
-}
-
-vnet_api_error_t
-bfd_auth_set_key (u32 conf_key_id, u8 auth_type, u8 key_len,
-                 const u8 * key_data)
-{
-#if WITH_LIBSSL > 0
-  bfd_auth_key_t *auth_key = NULL;
-  if (!key_len || key_len > bfd_max_len_for_auth_type (auth_type))
-    {
-      clib_warning ("Invalid authentication key length for auth_type=%d:%s "
-                   "(key_len=%u, must be "
-                   "non-zero, expected max=%u)",
-                   auth_type, bfd_auth_type_str (auth_type), key_len,
-                   (u32) bfd_max_len_for_auth_type (auth_type));
-      return VNET_API_ERROR_INVALID_VALUE;
-    }
-  if (!bfd_auth_type_supported (auth_type))
-    {
-      clib_warning ("Unsupported auth type=%d:%s", auth_type,
-                   bfd_auth_type_str (auth_type));
-      return VNET_API_ERROR_BFD_NOTSUPP;
-    }
-  bfd_main_t *bm = bfd_udp_main.bfd_main;
-  uword *key_idx_p = hash_get (bm->auth_key_by_conf_key_id, conf_key_id);
-  if (key_idx_p)
-    {
-      /* modifying existing key - must not be used */
-      const uword key_idx = *key_idx_p;
-      auth_key = pool_elt_at_index (bm->auth_keys, key_idx);
-      if (auth_key->use_count > 0)
-       {
-         clib_warning ("Authentication key with conf ID %u in use by %u BFD "
-                       "sessions - cannot modify",
-                       conf_key_id, auth_key->use_count);
-         return VNET_API_ERROR_BFD_EINUSE;
-       }
-    }
-  else
-    {
-      /* adding new key */
-      pool_get (bm->auth_keys, auth_key);
-      auth_key->conf_key_id = conf_key_id;
-      hash_set (bm->auth_key_by_conf_key_id, conf_key_id,
-               auth_key - bm->auth_keys);
-    }
-  auth_key->auth_type = auth_type;
-  memset (auth_key->key, 0, sizeof (auth_key->key));
-  clib_memcpy (auth_key->key, key_data, key_len);
-  return 0;
-#else
-  clib_warning ("SSL missing, cannot manipulate authentication keys");
-  return VNET_API_ERROR_BFD_NOTSUPP;
-#endif
-}
-
-vnet_api_error_t
-bfd_auth_del_key (u32 conf_key_id)
-{
-#if WITH_LIBSSL > 0
-  bfd_auth_key_t *auth_key = NULL;
-  bfd_main_t *bm = bfd_udp_main.bfd_main;
-  uword *key_idx_p = hash_get (bm->auth_key_by_conf_key_id, conf_key_id);
-  if (key_idx_p)
-    {
-      /* deleting existing key - must not be used */
-      const uword key_idx = *key_idx_p;
-      auth_key = pool_elt_at_index (bm->auth_keys, key_idx);
-      if (auth_key->use_count > 0)
-       {
-         clib_warning ("Authentication key with conf ID %u in use by %u BFD "
-                       "sessions - cannot delete",
-                       conf_key_id, auth_key->use_count);
-         return VNET_API_ERROR_BFD_EINUSE;
-       }
-      hash_unset (bm->auth_key_by_conf_key_id, conf_key_id);
-      memset (auth_key, 0, sizeof (*auth_key));
-      pool_put (bm->auth_keys, auth_key);
-    }
-  else
-    {
-      /* no such key */
-      clib_warning ("Authentication key with conf ID %u does not exist",
-                   conf_key_id);
-      return VNET_API_ERROR_BFD_ENOENT;
-    }
+  bfd_session_set_flags (vm, bs, admin_up_down);
+  bfd_unlock (bm);
   return 0;
-#else
-  clib_warning ("SSL missing, cannot manipulate authentication keys");
-  return VNET_API_ERROR_BFD_NOTSUPP;
-#endif
 }
 
 vnet_api_error_t
@@ -557,6 +860,10 @@ bfd_udp_auth_activate (u32 sw_if_index,
                       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 =
@@ -564,11 +871,16 @@ bfd_udp_auth_activate (u32 sw_if_index,
                                       &bs);
   if (rv)
     {
+      bfd_unlock (bm);
       return rv;
     }
-  return bfd_auth_activate (bs, conf_key_id, key_id, is_delayed);
+  error = bfd_auth_activate (bs, conf_key_id, key_id, is_delayed);
+  bfd_unlock (bm);
+  return error;
 #else
-  clib_warning ("SSL missing, cannot activate BFD authentication");
+  vlib_log_err (bfd_udp_main->log_class,
+               "SSL missing, cannot activate BFD authentication");
+  bfd_unlock (bm);
   return VNET_API_ERROR_BFD_NOTSUPP;
 #endif
 }
@@ -578,21 +890,29 @@ 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;
     }
-  return bfd_auth_deactivate (bs, is_delayed);
+  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;
 
@@ -619,6 +939,14 @@ typedef enum
     BFD_UDP_N_ERROR,
 } bfd_udp_error_t;
 
+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)") \
@@ -647,7 +975,7 @@ 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");
@@ -708,22 +1036,12 @@ typedef struct
 } 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)
+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
@@ -768,7 +1086,7 @@ bfd_udp4_scan (vlib_main_t * vm, vlib_node_runtime_t * rt,
   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;
@@ -784,7 +1102,7 @@ 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_auth (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;
@@ -794,7 +1112,7 @@ 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;
 }
@@ -804,7 +1122,7 @@ bfd_udp6_find_headers (vlib_buffer_t * b, ip6_header_t ** ip6,
                       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");
@@ -910,7 +1228,7 @@ bfd_udp6_scan (vlib_main_t * vm, vlib_node_runtime_t * rt,
   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.ip6.as_u64[0] = ip6->dst_address.as_u64[0];
       key.local_addr.ip6.as_u64[1] = ip6->dst_address.as_u64[1];
@@ -928,7 +1246,7 @@ bfd_udp6_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_auth (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;
@@ -938,7 +1256,7 @@ bfd_udp6_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;
 }
@@ -953,6 +1271,7 @@ bfd_udp_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
 {
   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 */
@@ -976,10 +1295,11 @@ bfd_udp_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
          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);
+         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, rt, b0, &bs);
@@ -1001,7 +1321,10 @@ bfd_udp_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
          const bfd_pkt_t *pkt = vlib_buffer_get_current (b0);
          if (bfd_pkt_get_poll (pkt))
            {
-             bfd_init_final_control_frame (vm, b0, bs);
+             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,
@@ -1012,9 +1335,26 @@ bfd_udp_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
                  vlib_node_increment_counter (vm, bfd_udp4_input_node.index,
                                               b0->error, 1);
                }
-             next0 = BFD_UDP_INPUT_NEXT_REPLY;
+             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;
@@ -1049,7 +1389,9 @@ 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* */
@@ -1076,49 +1418,13 @@ 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* */
 
-/**
- * @brief swap the source and destination IP addresses in the packet
- */
-static int
-bfd_echo_address_swap (vlib_buffer_t * b, int is_ipv6)
-{
-  udp_header_t *dummy = NULL;
-  if (is_ipv6)
-    {
-      ip6_header_t *ip6 = NULL;
-      bfd_udp6_find_headers (b, &ip6, &dummy);
-      if (!ip6)
-       {
-         return 0;
-       }
-      ip6_address_t tmp = ip6->dst_address;
-      ip6->dst_address = ip6->src_address;
-      ip6->src_address = tmp;
-      vlib_buffer_advance (b,
-                          (u8 *) ip6 - (u8 *) vlib_buffer_get_current (b));
-    }
-  else
-    {
-      ip4_header_t *ip4 = NULL;
-      bfd_udp4_find_headers (b, &ip4, &dummy);
-      if (!ip4)
-       {
-         return 0;
-       }
-      ip4_address_t tmp = ip4->dst_address;
-      ip4->dst_address = ip4->src_address;
-      ip4->src_address = tmp;
-      vlib_buffer_advance (b,
-                          (u8 *) ip4 - (u8 *) vlib_buffer_get_current (b));
-    }
-  return 1;
-}
-
 /*
  * Process a frame of bfd echo packets
  * Expect 1 packet / frame
@@ -1129,6 +1435,7 @@ bfd_udp_echo_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
 {
   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 */
@@ -1150,10 +1457,16 @@ bfd_udp_echo_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
          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);
+         clib_memcpy_fast (t0->data, vlib_buffer_get_current (b0), len);
        }
 
-      if (bfd_echo_address_swap (b0, is_ipv6))
+      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];
@@ -1167,14 +1480,10 @@ bfd_udp_echo_input (vlib_main_t * vm, vlib_node_runtime_t * rt,
              vlib_node_increment_counter (vm, bfd_udp_echo4_input_node.index,
                                           b0->error, 1);
            }
-         next0 = BFD_UDP_INPUT_NEXT_REPLY;
-       }
-      else
-       {
-         b0->error = rt->errors[BFD_UDP_ERROR_BAD];
-         next0 = BFD_UDP_INPUT_NEXT_NORMAL;
+         next0 = BFD_UDP_ECHO_INPUT_NEXT_REPLY_REWRITE;
        }
 
+      bfd_unlock (bm);
       vlib_set_next_frame_buffer (vm, rt, next0, bi0);
 
       from += 1;
@@ -1222,11 +1531,12 @@ VLIB_REGISTER_NODE (bfd_udp_echo4_input_node, static) = {
 
   .format_trace = bfd_echo_input_format_trace,
 
-  .n_next_nodes = BFD_UDP_INPUT_N_NEXT,
+  .n_next_nodes = BFD_UDP_ECHO_INPUT_N_NEXT,
   .next_nodes =
       {
-              [BFD_UDP_INPUT_NEXT_NORMAL] = "error-drop",
-              [BFD_UDP_INPUT_NEXT_REPLY] = "ip4-lookup",
+              [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* */
@@ -1250,40 +1560,52 @@ VLIB_REGISTER_NODE (bfd_udp_echo6_input_node, static) = {
 
   .format_trace = bfd_echo_input_format_trace,
 
-  .n_next_nodes = BFD_UDP_INPUT_N_NEXT,
+  .n_next_nodes = BFD_UDP_ECHO_INPUT_N_NEXT,
   .next_nodes =
       {
-              [BFD_UDP_INPUT_NEXT_NORMAL] = "error-drop",
-              [BFD_UDP_INPUT_NEXT_REPLY] = "ip6-lookup",
+              [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_sw_interface_up_down (vnet_main_t * vnm, u32 sw_if_index, u32 flags)
+bfd_udp_sw_if_add_del (vnet_main_t * vnm, u32 sw_if_index, u32 is_create)
 {
-  // vnet_hw_interface_t *hi = vnet_get_sup_hw_interface (vnm, sw_if_index);
-  if (!(flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP))
-    {
-      /* TODO */
-    }
-  return 0;
-}
-
-VNET_SW_INTERFACE_ADMIN_UP_DOWN_FUNCTION (bfd_sw_interface_up_down);
-
-static clib_error_t *
-bfd_hw_interface_up_down (vnet_main_t * vnm, u32 hw_if_index, u32 flags)
-{
-  if (flags & VNET_HW_INTERFACE_FLAG_LINK_UP)
-    {
-      /* TODO */
-    }
+  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
@@ -1291,15 +1613,33 @@ VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION (bfd_hw_interface_up_down);
 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));
   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);
-  udp_register_dst_port (vm, UDP_DST_PORT_bfd_echo4,
-                        bfd_udp_echo4_input_node.index, 1);
-  udp_register_dst_port (vm, UDP_DST_PORT_bfd_echo6,
-                        bfd_udp_echo6_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;
 }