src/vnet/bfd/bfd_udp.c

/*
 * 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.
 */
#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/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/adj/adj.h>
#include <vnet/adj/adj_nbr.h>
#include <vnet/bfd/bfd_debug.h>
#include <vnet/bfd/bfd_udp.h>
#include <vnet/bfd/bfd_main.h>
#include <vnet/bfd/bfd_api.h>

typedef struct
{
  bfd_main_t *bfd_main;
  /* hashmap - bfd session index by bfd key - used for CLI/API lookup, where
   * discriminator is unknown */
  mhash_t bfd_session_idx_by_bfd_key;
} bfd_udp_main_t;

static vlib_node_registration_t bfd_udp4_input_node;
static vlib_node_registration_t bfd_udp6_input_node;

bfd_udp_main_t bfd_udp_main;

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);
}

void
bfd_add_udp4_transport (vlib_main_t * vm, vlib_buffer_t * b,
			const bfd_session_t * bs)
{
  const bfd_udp_session_t *bus = &bs->udp;
  const bfd_udp_key_t *key = &bus->key;

  b->flags |= VNET_BUFFER_LOCALLY_ORIGINATED;
  vnet_buffer (b)->ip.adj_index[VLIB_RX] = bus->adj_index;
  vnet_buffer (b)->ip.adj_index[VLIB_TX] = bus->adj_index;
  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);
  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);

  /* 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);
}

void
bfd_add_udp6_transport (vlib_main_t * vm, vlib_buffer_t * b,
			const bfd_session_t * bs)
{
  const bfd_udp_session_t *bus = &bs->udp;
  const bfd_udp_key_t *key = &bus->key;

  b->flags |= VNET_BUFFER_LOCALLY_ORIGINATED;
  vnet_buffer (b)->ip.adj_index[VLIB_RX] = bus->adj_index;
  vnet_buffer (b)->ip.adj_index[VLIB_TX] = bus->adj_index;
  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);
  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);

  /* 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;
    }
}

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)
    {
      return bfd_find_session_by_idx (bum->bfd_main, *p);
    }
  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)
{
  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_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;
  if (!ip46_address_is_ip4 (local_addr))
    {
      t = BFD_TRANSPORT_UDP6;
    }
  bfd_session_t *bs = bfd_get_session (bum->bfd_main, t);
  bfd_udp_session_t *bus = &bs->udp;
  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",
		    tmp->bs_idx);
      bfd_put_session (bum->bfd_main, bs);
      return VNET_API_ERROR_BFD_EEXIST;
    }
  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);
  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);
      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);
    }
  else
    {
      bus->adj_index = adj_nbr_add_or_lock (FIB_PROTOCOL_IP6, VNET_LINK_IP6,
					    &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_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)
{
  vnet_sw_interface_t *sw_if =
    vnet_get_sw_interface (vnet_get_main (), sw_if_index);
  u8 local_ip_valid = 0;
  ip_interface_address_t *ia = NULL;
  if (!sw_if)
    {
      clib_warning ("got NULL sw_if");
      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");
	  return VNET_API_ERROR_INVALID_ARGUMENT;
	}
      ip4_main_t *im = &ip4_main;

      /* *INDENT-OFF* */
      foreach_ip_interface_address (
          &im->lookup_main, ia, sw_if_index, 0 /* honor unnumbered */, ({
            ip4_address_t *x =
                ip_interface_address_get_address (&im->lookup_main, ia);
            if (x->as_u32 == local_addr->ip4.as_u32)
              {
                /* valid address for this interface */
                local_ip_valid = 1;
                break;
              }
          }));
      /* *INDENT-ON* */
    }
  else
    {
      if (ip46_address_is_ip4 (peer_addr))
	{
	  clib_warning ("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* */
    }

  if (!local_ip_valid)
    {
      clib_warning ("address not found on interface");
      return VNET_API_ERROR_ADDRESS_NOT_FOUND_FOR_INTERFACE;
    }

  return 0;
}

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);
  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
	{
	  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);
	  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)
{
  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)
    {
      clib_warning ("detect_mult < 1");
      return VNET_API_ERROR_INVALID_ARGUMENT;
    }
  if (desired_min_tx_usec < 1)
    {
      clib_warning ("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_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);
  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)
{
  vnet_api_error_t rv =
    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 (&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
      clib_warning ("SSL missing, cannot add authenticated BFD session");
      rv = VNET_API_ERROR_BFD_NOTSUPP;
#endif
      if (rv)
	{
	  bfd_udp_del_session_internal (bs);
	}
    }
  if (!rv)
    {
      bfd_session_start (bfd_udp_main.bfd_main, bs);
    }

  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;
  vnet_api_error_t rv =
    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
				       &bs);
  if (rv)
    {
      return rv;
    }

  return bfd_session_set_params (bfd_udp_main.bfd_main, bs,
				 desired_min_tx_usec, required_min_rx_usec,
				 detect_mult);
}

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;
  vnet_api_error_t rv =
    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
				       &bs);
  if (rv)
    {
      return rv;
    }
  bfd_udp_del_session_internal (bs);
  return 0;
}

vnet_api_error_t
bfd_udp_session_set_flags (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;
  vnet_api_error_t rv =
    bfd_udp_find_session_by_api_input (sw_if_index, local_addr, peer_addr,
				       &bs);
  if (rv)
    {
      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;
    }
  return 0;
#else
  clib_warning ("SSL missing, cannot manipulate authentication keys");
  return VNET_API_ERROR_BFD_NOTSUPP;
#endif
}

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)
{
#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)
    {
      return rv;
    }
  return bfd_auth_activate (bs, conf_key_id, key_id, is_delayed);
#else
  clib_warning ("SSL missing, cannot activate BFD authentication");
  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_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)
    {
      return rv;
    }
  return bfd_auth_deactivate (bs, is_delayed);
}

typedef enum
{
  BFD_UDP_INPUT_NEXT_NORMAL,
  BFD_UDP_INPUT_NEXT_REPLY,
  BFD_UDP_INPUT_N_NEXT,
} bfd_udp_input_next_t;

/* Packet counters */
#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")

#define F(sym, string) static char BFD_UDP_ERR_##sym##_STR[] = string;
foreach_bfd_udp_error (F);
#undef F

static char *bfd_udp_error_strings[] = {
#define F(sym, string) BFD_UDP_ERR_##sym##_STR,
  foreach_bfd_udp_error (F)
#undef F
};

typedef enum
{
#define F(sym, str) BFD_UDP_ERROR_##sym,
  foreach_bfd_udp_error (F)
#undef F
    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)
{
  /* sanity check first */
  const i32 start = vnet_buffer (b)->ip.start_of_ip_header;
  if (start < 0 && start < sizeof (b->pre_data))
    {
      BFD_ERR ("Start of ip header is before pre_data, ignoring");
      *ip4 = NULL;
      *udp = NULL;
      return;
    }
  *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);
}

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 ("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 ("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 ("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)
    {
      BFD_ERR ("Invalid UDP src port %u, out of range <49152,65535>",
	       udp->src_port);
    }
  return BFD_UDP_ERROR_NONE;
}

typedef struct
{
  u32 bs_idx;
  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)
{
  /* 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);
}

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));
      return BFD_UDP_ERROR_BAD;
    }
  const ip4_header_t *ip4;
  const 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;
    }
  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;
      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);
      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 (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_udp4_verify_transport (ip4, udp, bs)))
    {
      return err;
    }
  bfd_rpc_update_session (bs->bs_idx, pkt);
  *bs_out = bs;
  return BFD_UDP_ERROR_NONE;
}

static void
bfd_udp6_find_headers (vlib_buffer_t * b, const ip6_header_t ** ip6,
		       const udp_header_t ** udp)
{
  /* sanity check first */
  const i32 start = vnet_buffer (b)->ip.start_of_ip_header;
  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;
    }
  const ip6_header_t *ip6;
  const 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;
      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 (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 (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)
{
  u32 n_left_from, *from;
  bfd_input_trace_t *t0;

  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)
    {
      u32 bi0;
      vlib_buffer_t *b0;
      u32 next0, error0;

      bi0 = from[0];
      b0 = vlib_get_buffer (vm, bi0);

      bfd_session_t *bs = NULL;

      /* 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);
	}

      /* scan this bfd pkt. error0 is the counter index to bmp */
      if (is_ipv6)
	{
	  error0 = bfd_udp6_scan (vm, rt, b0, &bs);
	}
      else
	{
	  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_init_final_control_frame (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;
	    }
	}
      vlib_set_next_frame_buffer (vm, rt, next0, bi0);

      from += 1;
      n_left_from -= 1;
    }

  return f->n_vectors;
}

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);
}

/*
 * bfd input graph node declaration
 */
/* *INDENT-OFF* */
VLIB_REGISTER_NODE (bfd_udp4_input_node, static) = {
  .function = bfd_udp4_input,
  .name = "bfd-udp4-input",
  .vector_size = sizeof (u32),
  .type = VLIB_NODE_TYPE_INTERNAL,

  .n_errors = BFD_UDP_N_ERROR,
  .error_strings = bfd_udp_error_strings,

  .format_trace = bfd_input_format_trace,

  .n_next_nodes = BFD_UDP_INPUT_N_NEXT,
  .next_nodes =
      {
              [BFD_UDP_INPUT_NEXT_NORMAL] = "error-drop",
              [BFD_UDP_INPUT_NEXT_REPLY] = "ip4-lookup",
      },
};
/* *INDENT-ON* */

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);
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (bfd_udp6_input_node, static) = {
  .function = bfd_udp6_input,
  .name = "bfd-udp6-input",
  .vector_size = sizeof (u32),
  .type = VLIB_NODE_TYPE_INTERNAL,

  .n_errors = BFD_UDP_N_ERROR,
  .error_strings = bfd_udp_error_strings,

  .format_trace = bfd_input_format_trace,

  .n_next_nodes = BFD_UDP_INPUT_N_NEXT,
  .next_nodes =
      {
              [BFD_UDP_INPUT_NEXT_NORMAL] = "error-drop",
              [BFD_UDP_INPUT_NEXT_REPLY] = "ip6-lookup",
      },
};
/* *INDENT-ON* */

static clib_error_t *
bfd_sw_interface_up_down (vnet_main_t * vnm, u32 sw_if_index, u32 flags)
{
  // 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 */
    }
  return 0;
}

VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION (bfd_hw_interface_up_down);

/*
 * setup function
 */
static clib_error_t *
bfd_udp_init (vlib_main_t * vm)
{
  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);
  return 0;
}

VLIB_INIT_FUNCTION (bfd_udp_init);

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */