out2in_ed.c

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/*
 * Copyright (c) 2018 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 NAT44 endpoint-dependent outside to inside network translation
 */

#include <vlib/vlib.h>
#include <vnet/vnet.h>
#include <vnet/ip/ip.h>
#include <vnet/ethernet/ethernet.h>
#include <vnet/fib/ip4_fib.h>
#include <vnet/udp/udp_local.h>
#include <vppinfra/error.h>
#include <nat/nat.h>
#include <nat/lib/ipfix_logging.h>
#include <nat/nat_inlines.h>
#include <nat/nat44/inlines.h>
#include <nat/lib/nat_syslog.h>
#include <nat/nat_ha.h>
#include <nat/nat44/ed_inlines.h>

static char *nat_out2in_ed_error_strings[] = {
#define _(sym,string) string,
  foreach_nat_out2in_ed_error
#undef _
};

typedef struct
{
  u32 sw_if_index;
  u32 next_index;
  u32 session_index;
  u32 is_slow_path;
} nat44_ed_out2in_trace_t;

typedef struct
{
  u16 thread_next;
} nat44_ed_out2in_handoff_trace_t;

static u8 *
format_nat44_ed_out2in_trace (u8 * s, va_list * args)
{
  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
  nat44_ed_out2in_trace_t *t = va_arg (*args, nat44_ed_out2in_trace_t *);
  char *tag;

  tag =
    t->is_slow_path ? "NAT44_OUT2IN_ED_SLOW_PATH" :
    "NAT44_OUT2IN_ED_FAST_PATH";

  s = format (s, "%s: sw_if_index %d, next index %d, session %d", tag,
              t->sw_if_index, t->next_index, t->session_index);

  return s;
}

static inline u32
icmp_out2in_ed_slow_path (snat_main_t * sm, vlib_buffer_t * b0,
                          ip4_header_t * ip0, icmp46_header_t * icmp0,
                          u32 sw_if_index0, u32 rx_fib_index0,
                          vlib_node_runtime_t * node, u32 next0, f64 now,
                          u32 thread_index, snat_session_t ** p_s0)
{
  vlib_main_t *vm = vlib_get_main ();

  next0 = icmp_out2in (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
                       next0, thread_index, p_s0, 0);
  snat_session_t *s0 = *p_s0;
  if (PREDICT_TRUE (next0 != NAT_NEXT_DROP && s0))
    {
      /* Accounting */
      nat44_session_update_counters (s0, now,
                                     vlib_buffer_length_in_chain
                                     (vm, b0), thread_index);
      /* Per-user LRU list maintenance */
      nat44_session_update_lru (sm, s0, thread_index);
    }
  return next0;
}

#ifndef CLIB_MARCH_VARIANT
int
nat44_o2i_ed_is_idle_session_cb (clib_bihash_kv_16_8_t * kv, void *arg)
{
  snat_main_t *sm = &snat_main;
  nat44_is_idle_session_ctx_t *ctx = arg;
  snat_session_t *s;
  u64 sess_timeout_time;
  u8 proto;
  u16 r_port, l_port;
  ip4_address_t *l_addr, *r_addr;
  u32 fib_index;
  clib_bihash_kv_16_8_t ed_kv;
  int i;
  //snat_address_t *a;
  snat_main_per_thread_data_t *tsm = vec_elt_at_index (sm->per_thread_data,
                                                       ctx->thread_index);

  s = pool_elt_at_index (tsm->sessions, kv->value);
  sess_timeout_time = s->last_heard + (f64) nat44_session_get_timeout (sm, s);
  if (ctx->now >= sess_timeout_time)
    {
      l_addr = &s->in2out.addr;
      r_addr = &s->ext_host_addr;
      fib_index = s->in2out.fib_index;
      if (snat_is_unk_proto_session (s))
        {
          proto = s->in2out.port;
          r_port = 0;
          l_port = 0;
        }
      else
        {
          proto = nat_proto_to_ip_proto (s->nat_proto);
          l_port = s->in2out.port;
          r_port = s->ext_host_port;
        }
      if (is_twice_nat_session (s))
        {
          r_addr = &s->ext_host_nat_addr;
          r_port = s->ext_host_nat_port;
        }
      init_ed_k (&ed_kv, *l_addr, l_port, *r_addr, r_port, fib_index, proto);
      if (clib_bihash_add_del_16_8 (&tsm->in2out_ed, &ed_kv, 0))
        nat_elog_warn ("in2out_ed key del failed");

      if (snat_is_unk_proto_session (s))
        goto delete;

      nat_ipfix_logging_nat44_ses_delete (ctx->thread_index,
                                          s->in2out.addr.as_u32,
                                          s->out2in.addr.as_u32,
                                          s->nat_proto,
                                          s->in2out.port,
                                          s->out2in.port,
                                          s->in2out.fib_index);

      nat_syslog_nat44_sdel (s->user_index, s->in2out.fib_index,
                             &s->in2out.addr, s->in2out.port,
                             &s->ext_host_nat_addr, s->ext_host_nat_port,
                             &s->out2in.addr, s->out2in.port,
                             &s->ext_host_addr, s->ext_host_port,
                             s->nat_proto, is_twice_nat_session (s));

      nat_ha_sdel (&s->out2in.addr, s->out2in.port, &s->ext_host_addr,
                   s->ext_host_port, s->nat_proto, s->out2in.fib_index,
                   ctx->thread_index);

      if (is_twice_nat_session (s))
        {
          for (i = 0; i < vec_len (sm->twice_nat_addresses); i++)
            {
              // FIXME TODO this is obviously wrong code ... needs fix!
              //       key.protocol = s->nat_proto;
              //       key.port = s->ext_host_nat_port;
              //       a = sm->twice_nat_addresses + i;
              //       if (a->addr.as_u32 == s->ext_host_nat_addr.as_u32)
              //      {
              //        snat_free_outside_address_and_port (sm->twice_nat_addresses,
              //                                            ctx->thread_index,
              //                                            &key);
              //        break;
              //      }
            }
        }

      if (snat_is_session_static (s))
        goto delete;

      snat_free_outside_address_and_port (sm->addresses, ctx->thread_index,
                                          &s->out2in.addr, s->out2in.port,
                                          s->nat_proto);
    delete:
      nat_ed_session_delete (sm, s, ctx->thread_index, 1);
      return 1;
    }

  return 0;
}
#endif

// allocate exact address based on preference
static_always_inline int
nat_alloc_addr_and_port_exact (snat_address_t * a,
                               u32 thread_index,
                               nat_protocol_t proto,
                               ip4_address_t * addr,
                               u16 * port,
                               u16 port_per_thread, u32 snat_thread_index)
{
  u32 portnum;

  switch (proto)
    {
#define _(N, j, n, s) \
    case NAT_PROTOCOL_##N: \
      if (a->busy_##n##_ports_per_thread[thread_index] < port_per_thread) \
        { \
          while (1) \
            { \
              portnum = (port_per_thread * \
                snat_thread_index) + \
                snat_random_port(0, port_per_thread - 1) + 1024; \
              if (a->busy_##n##_port_refcounts[portnum]) \
                continue; \
              --a->busy_##n##_port_refcounts[portnum]; \
              a->busy_##n##_ports_per_thread[thread_index]++; \
              a->busy_##n##_ports++; \
              *addr = a->addr; \
              *port = clib_host_to_net_u16(portnum); \
              return 0; \
            } \
        } \
      break;
      foreach_nat_protocol
#undef _
    default:
      nat_elog_info ("unknown protocol");
      return 1;
    }

  /* Totally out of translations to use... */
  nat_ipfix_logging_addresses_exhausted (thread_index, 0);
  return 1;
}


static snat_session_t *
create_session_for_static_mapping_ed (snat_main_t * sm,
                                      vlib_buffer_t * b,
                                      ip4_address_t i2o_addr,
                                      u16 i2o_port,
                                      u32 i2o_fib_index,
                                      ip4_address_t o2i_addr,
                                      u16 o2i_port,
                                      u32 o2i_fib_index,
                                      nat_protocol_t nat_proto,
                                      vlib_node_runtime_t * node,
                                      u32 rx_fib_index,
                                      u32 thread_index,
                                      twice_nat_type_t twice_nat,
                                      lb_nat_type_t lb_nat, f64 now,
                                      snat_static_mapping_t * mapping)
{
  snat_session_t *s;
  ip4_header_t *ip;
  udp_header_t *udp;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  clib_bihash_kv_16_8_t kv;
  nat44_is_idle_session_ctx_t ctx;

  if (PREDICT_FALSE
      (nat44_ed_maximum_sessions_exceeded (sm, rx_fib_index, thread_index)))
    {
      b->error = node->errors[NAT_OUT2IN_ED_ERROR_MAX_SESSIONS_EXCEEDED];
      nat_elog_notice ("maximum sessions exceeded");
      return 0;
    }

  s = nat_ed_session_alloc (sm, thread_index, now, nat_proto);
  if (!s)
    {
      b->error = node->errors[NAT_OUT2IN_ED_ERROR_MAX_USER_SESS_EXCEEDED];
      nat_elog_warn ("create NAT session failed");
      return 0;
    }

  ip = vlib_buffer_get_current (b);
  udp = ip4_next_header (ip);

  s->ext_host_addr.as_u32 = ip->src_address.as_u32;
  s->ext_host_port = nat_proto == NAT_PROTOCOL_ICMP ? 0 : udp->src_port;
  s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
  if (lb_nat)
    s->flags |= SNAT_SESSION_FLAG_LOAD_BALANCING;
  if (lb_nat == AFFINITY_LB_NAT)
    s->flags |= SNAT_SESSION_FLAG_AFFINITY;
  s->flags |= SNAT_SESSION_FLAG_ENDPOINT_DEPENDENT;
  s->out2in.addr = o2i_addr;
  s->out2in.port = o2i_port;
  s->out2in.fib_index = o2i_fib_index;
  s->in2out.addr = i2o_addr;
  s->in2out.port = i2o_port;
  s->in2out.fib_index = i2o_fib_index;
  s->nat_proto = nat_proto;

  /* Add to lookup tables */
  init_ed_kv (&kv, o2i_addr, o2i_port, s->ext_host_addr, s->ext_host_port,
              o2i_fib_index, ip->protocol, thread_index, s - tsm->sessions);
  ctx.now = now;
  ctx.thread_index = thread_index;
  if (clib_bihash_add_or_overwrite_stale_16_8 (&sm->out2in_ed, &kv,
                                               nat44_o2i_ed_is_idle_session_cb,
                                               &ctx))
    nat_elog_notice ("out2in-ed key add failed");

  if (twice_nat == TWICE_NAT || (twice_nat == TWICE_NAT_SELF &&
                                 ip->src_address.as_u32 == i2o_addr.as_u32))
    {
      int rc = 0;
      snat_address_t *filter = 0;

      // if exact address is specified use this address
      if (is_exact_address (mapping))
        {
          snat_address_t *ap;
          vec_foreach (ap, sm->twice_nat_addresses)
          {
            if (mapping->pool_addr.as_u32 == ap->addr.as_u32)
              {
                filter = ap;
                break;
              }
          }
        }

      if (filter)
        {
          rc = nat_alloc_addr_and_port_exact (filter,
                                              thread_index,
                                              nat_proto,
                                              &s->ext_host_nat_addr,
                                              &s->ext_host_nat_port,
                                              sm->port_per_thread,
                                              tsm->snat_thread_index);
          s->flags |= SNAT_SESSION_FLAG_EXACT_ADDRESS;
        }
      else
        {
          rc =
            snat_alloc_outside_address_and_port (sm->twice_nat_addresses, 0,
                                                 thread_index, nat_proto,
                                                 &s->ext_host_nat_addr,
                                                 &s->ext_host_nat_port,
                                                 sm->port_per_thread,
                                                 tsm->snat_thread_index);
        }

      if (rc)
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_OUT_OF_PORTS];
          nat_ed_session_delete (sm, s, thread_index, 1);
          if (clib_bihash_add_del_16_8 (&sm->out2in_ed, &kv, 0))
            nat_elog_notice ("out2in-ed key del failed");
          return 0;
        }

      s->flags |= SNAT_SESSION_FLAG_TWICE_NAT;
      init_ed_kv (&kv, i2o_addr, i2o_port, s->ext_host_nat_addr,
                  s->ext_host_nat_port, i2o_fib_index, ip->protocol,
                  thread_index, s - tsm->sessions);
    }
  else
    {
      init_ed_kv (&kv, i2o_addr, i2o_port, s->ext_host_addr,
                  s->ext_host_port, i2o_fib_index, ip->protocol,
                  thread_index, s - tsm->sessions);
    }
  if (clib_bihash_add_or_overwrite_stale_16_8 (&tsm->in2out_ed, &kv,
                                               nat44_i2o_ed_is_idle_session_cb,
                                               &ctx))
    nat_elog_notice ("in2out-ed key add failed");

  nat_ipfix_logging_nat44_ses_create (thread_index,
                                      s->in2out.addr.as_u32,
                                      s->out2in.addr.as_u32,
                                      s->nat_proto,
                                      s->in2out.port,
                                      s->out2in.port, s->in2out.fib_index);

  nat_syslog_nat44_sadd (s->user_index, s->in2out.fib_index,
                         &s->in2out.addr, s->in2out.port,
                         &s->ext_host_nat_addr, s->ext_host_nat_port,
                         &s->out2in.addr, s->out2in.port,
                         &s->ext_host_addr, s->ext_host_port,
                         s->nat_proto, is_twice_nat_session (s));

  nat_ha_sadd (&s->in2out.addr, s->in2out.port, &s->out2in.addr,
               s->out2in.port, &s->ext_host_addr, s->ext_host_port,
               &s->ext_host_nat_addr, s->ext_host_nat_port,
               s->nat_proto, s->in2out.fib_index, s->flags, thread_index, 0);

  per_vrf_sessions_register_session (s, thread_index);

  return s;
}

static int
next_src_nat (snat_main_t * sm, ip4_header_t * ip, u16 src_port,
              u16 dst_port, u32 thread_index, u32 rx_fib_index)
{
  clib_bihash_kv_16_8_t kv, value;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];

  init_ed_k (&kv, ip->src_address, src_port, ip->dst_address, dst_port,
             rx_fib_index, ip->protocol);
  if (!clib_bihash_search_16_8 (&tsm->in2out_ed, &kv, &value))
    return 1;

  return 0;
}

static void
create_bypass_for_fwd (snat_main_t * sm, vlib_buffer_t * b, ip4_header_t * ip,
                       u32 rx_fib_index, u32 thread_index)
{
  clib_bihash_kv_16_8_t kv, value;
  udp_header_t *udp;
  snat_session_t *s = 0;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  vlib_main_t *vm = vlib_get_main ();
  f64 now = vlib_time_now (vm);
  u16 l_port, r_port;

  if (ip->protocol == IP_PROTOCOL_ICMP)
    {
      if (get_icmp_o2i_ed_key
          (b, ip, rx_fib_index, ~0, ~0, 0, &l_port, &r_port, &kv))
        return;
    }
  else
    {
      if (ip->protocol == IP_PROTOCOL_UDP || ip->protocol == IP_PROTOCOL_TCP)
        {
          udp = ip4_next_header (ip);
          l_port = udp->dst_port;
          r_port = udp->src_port;
        }
      else
        {
          l_port = 0;
          r_port = 0;
        }
      init_ed_k (&kv, ip->dst_address, l_port, ip->src_address, r_port,
                 rx_fib_index, ip->protocol);
    }

  if (!clib_bihash_search_16_8 (&tsm->in2out_ed, &kv, &value))
    {
      ASSERT (thread_index == ed_value_get_thread_index (&value));
      s =
        pool_elt_at_index (tsm->sessions,
                           ed_value_get_session_index (&value));
    }
  else if (ip->protocol == IP_PROTOCOL_ICMP &&
           icmp_type_is_error_message
           (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags))
    {
      return;
    }
  else
    {
      u32 proto;

      if (PREDICT_FALSE
          (nat44_ed_maximum_sessions_exceeded
           (sm, rx_fib_index, thread_index)))
        return;

      s = nat_ed_session_alloc (sm, thread_index, now, ip->protocol);
      if (!s)
        {
          nat_elog_warn ("create NAT session failed");
          return;
        }

      proto = ip_proto_to_nat_proto (ip->protocol);

      s->ext_host_addr = ip->src_address;
      s->ext_host_port = r_port;
      s->flags |= SNAT_SESSION_FLAG_FWD_BYPASS;
      s->out2in.addr = ip->dst_address;
      s->out2in.port = l_port;
      s->nat_proto = proto;
      if (proto == NAT_PROTOCOL_OTHER)
        {
          s->flags |= SNAT_SESSION_FLAG_UNKNOWN_PROTO;
          s->out2in.port = ip->protocol;
        }
      s->out2in.fib_index = rx_fib_index;
      s->in2out.addr = s->out2in.addr;
      s->in2out.port = s->out2in.port;
      s->in2out.fib_index = s->out2in.fib_index;

      kv.value = s - tsm->sessions;
      if (clib_bihash_add_del_16_8 (&tsm->in2out_ed, &kv, 1))
        nat_elog_notice ("in2out_ed key add failed");

      per_vrf_sessions_register_session (s, thread_index);
    }

  if (ip->protocol == IP_PROTOCOL_TCP)
    {
      tcp_header_t *tcp = ip4_next_header (ip);
      nat44_set_tcp_session_state_o2i (sm, now, s, tcp->flags,
                                       tcp->ack_number, tcp->seq_number,
                                       thread_index);
    }

  /* Accounting */
  nat44_session_update_counters (s, now, 0, thread_index);
  /* Per-user LRU list maintenance */
  nat44_session_update_lru (sm, s, thread_index);
}

static_always_inline int
create_bypass_for_fwd_worker (snat_main_t * sm,
                              vlib_buffer_t * b, ip4_header_t * ip,
                              u32 rx_fib_index, u32 thread_index)
{
  ip4_header_t tmp = {
    .src_address = ip->dst_address,
  };
  u32 index = sm->worker_in2out_cb (&tmp, rx_fib_index, 0);

  if (index != thread_index)
    {
      vnet_buffer2 (b)->nat.thread_next = index;
      return 1;
    }

  create_bypass_for_fwd (sm, b, ip, rx_fib_index, thread_index);
  return 0;
}

#ifndef CLIB_MARCH_VARIANT
u32
icmp_match_out2in_ed (snat_main_t * sm, vlib_node_runtime_t * node,
                      u32 thread_index, vlib_buffer_t * b,
                      ip4_header_t * ip, ip4_address_t * addr,
                      u16 * port, u32 * fib_index, nat_protocol_t * proto,
                      void *d, void *e, u8 * dont_translate)
{
  u32 next = ~0, sw_if_index, rx_fib_index;
  clib_bihash_kv_16_8_t kv, value;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  snat_session_t *s = 0;
  u8 is_addr_only, identity_nat;
  u16 l_port, r_port;
  vlib_main_t *vm = vlib_get_main ();
  ip4_address_t sm_addr;
  u16 sm_port;
  u32 sm_fib_index;
  *dont_translate = 0;
  snat_static_mapping_t *m;

  sw_if_index = vnet_buffer (b)->sw_if_index[VLIB_RX];
  rx_fib_index = ip4_fib_table_get_index_for_sw_if_index (sw_if_index);

  if (get_icmp_o2i_ed_key
      (b, ip, rx_fib_index, ~0, ~0, proto, &l_port, &r_port, &kv))
    {
      b->error = node->errors[NAT_OUT2IN_ED_ERROR_UNSUPPORTED_PROTOCOL];
      next = NAT_NEXT_DROP;
      goto out;
    }

  if (clib_bihash_search_16_8 (&sm->out2in_ed, &kv, &value))
    {
      if (snat_static_mapping_match
          (sm, ip->dst_address, l_port, rx_fib_index,
           ip_proto_to_nat_proto (ip->protocol), &sm_addr, &sm_port,
           &sm_fib_index, 1, &is_addr_only, 0, 0, 0, &identity_nat, &m))
        {
          // static mapping not matched
          if (!sm->forwarding_enabled)
            {
              /* Don't NAT packet aimed at the intfc address */
              if (PREDICT_FALSE (is_interface_addr (sm, node, sw_if_index,
                                                    ip->dst_address.as_u32)))
                {
                  *dont_translate = 1;
                }
              else
                {
                  b->error = node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
                  next = NAT_NEXT_DROP;
                }
            }
          else
            {
              *dont_translate = 1;
              if (next_src_nat (sm, ip, l_port, r_port,
                                thread_index, rx_fib_index))
                {
                  next = NAT_NEXT_IN2OUT_ED_FAST_PATH;
                }
              else
                {
                  if (sm->num_workers > 1)
                    {
                      if (create_bypass_for_fwd_worker (sm, b, ip,
                                                        rx_fib_index,
                                                        thread_index))
                        {
                          next = NAT_NEXT_OUT2IN_ED_HANDOFF;
                        }
                    }
                  else
                    {
                      create_bypass_for_fwd (sm, b, ip, rx_fib_index,
                                             thread_index);
                    }
                }
            }
          goto out;
        }

      if (PREDICT_FALSE
          (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
           ICMP4_echo_reply
           && (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
               ICMP4_echo_request || !is_addr_only)))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_BAD_ICMP_TYPE];
          next = NAT_NEXT_DROP;
          goto out;
        }

      if (PREDICT_FALSE (identity_nat))
        {
          *dont_translate = 1;
          goto out;
        }

      /* Create session initiated by host from external network */
      s =
        create_session_for_static_mapping_ed (sm, b, sm_addr, sm_port,
                                              sm_fib_index, ip->dst_address,
                                              l_port, rx_fib_index, *proto,
                                              node, rx_fib_index,
                                              thread_index, 0, 0,
                                              vlib_time_now (vm), m);
      if (!s)
        next = NAT_NEXT_DROP;
    }
  else
    {
      if (PREDICT_FALSE
          (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
           ICMP4_echo_reply
           && vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
           ICMP4_echo_request
           && !icmp_type_is_error_message (vnet_buffer (b)->ip.
                                           reass.icmp_type_or_tcp_flags)))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_BAD_ICMP_TYPE];
          next = NAT_NEXT_DROP;
          goto out;
        }

      ASSERT (thread_index == ed_value_get_thread_index (&value));
      s =
        pool_elt_at_index (tsm->sessions,
                           ed_value_get_session_index (&value));
    }
out:
  if (s)
    {
      *addr = s->in2out.addr;
      *port = s->in2out.port;
      *fib_index = s->in2out.fib_index;
    }
  if (d)
    *(snat_session_t **) d = s;
  return next;
}
#endif

static snat_session_t *
nat44_ed_out2in_unknown_proto (snat_main_t * sm,
                               vlib_buffer_t * b,
                               ip4_header_t * ip,
                               u32 rx_fib_index,
                               u32 thread_index,
                               f64 now,
                               vlib_main_t * vm, vlib_node_runtime_t * node)
{
  clib_bihash_kv_8_8_t kv, value;
  clib_bihash_kv_16_8_t s_kv, s_value;
  snat_static_mapping_t *m;
  u32 old_addr, new_addr;
  ip_csum_t sum;
  snat_session_t *s;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];

  old_addr = ip->dst_address.as_u32;

  init_ed_k (&s_kv, ip->dst_address, 0, ip->src_address, 0, rx_fib_index,
             ip->protocol);

  if (!clib_bihash_search_16_8 (&sm->out2in_ed, &s_kv, &s_value))
    {
      ASSERT (thread_index == ed_value_get_thread_index (&s_value));
      s =
        pool_elt_at_index (tsm->sessions,
                           ed_value_get_session_index (&s_value));
      new_addr = ip->dst_address.as_u32 = s->in2out.addr.as_u32;
    }
  else
    {
      if (PREDICT_FALSE
          (nat44_ed_maximum_sessions_exceeded
           (sm, rx_fib_index, thread_index)))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_MAX_SESSIONS_EXCEEDED];
          nat_elog_notice ("maximum sessions exceeded");
          return 0;
        }

      init_nat_k (&kv, ip->dst_address, 0, 0, 0);
      if (clib_bihash_search_8_8
          (&sm->static_mapping_by_external, &kv, &value))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
          return 0;
        }

      m = pool_elt_at_index (sm->static_mappings, value.value);

      new_addr = ip->dst_address.as_u32 = m->local_addr.as_u32;

      /* Create a new session */
      s = nat_ed_session_alloc (sm, thread_index, now, ip->protocol);
      if (!s)
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_MAX_USER_SESS_EXCEEDED];
          nat_elog_warn ("create NAT session failed");
          return 0;
        }

      s->ext_host_addr.as_u32 = ip->src_address.as_u32;
      s->flags |= SNAT_SESSION_FLAG_UNKNOWN_PROTO;
      s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
      s->flags |= SNAT_SESSION_FLAG_ENDPOINT_DEPENDENT;
      s->out2in.addr.as_u32 = old_addr;
      s->out2in.fib_index = rx_fib_index;
      s->in2out.addr.as_u32 = new_addr;
      s->in2out.fib_index = m->fib_index;
      s->in2out.port = s->out2in.port = ip->protocol;

      /* Add to lookup tables */
      s_kv.value = s - tsm->sessions;
      if (clib_bihash_add_del_16_8 (&sm->out2in_ed, &s_kv, 1))
        nat_elog_notice ("out2in key add failed");

      init_ed_kv (&s_kv, ip->dst_address, 0, ip->src_address, 0, m->fib_index,
                  ip->protocol, thread_index, s - tsm->sessions);
      if (clib_bihash_add_del_16_8 (&tsm->in2out_ed, &s_kv, 1))
        nat_elog_notice ("in2out key add failed");

      per_vrf_sessions_register_session (s, thread_index);
    }

  /* Update IP checksum */
  sum = ip->checksum;
  sum = ip_csum_update (sum, old_addr, new_addr, ip4_header_t, dst_address);
  ip->checksum = ip_csum_fold (sum);

  vnet_buffer (b)->sw_if_index[VLIB_TX] = s->in2out.fib_index;

  /* Accounting */
  nat44_session_update_counters (s, now, vlib_buffer_length_in_chain (vm, b),
                                 thread_index);
  /* Per-user LRU list maintenance */
  nat44_session_update_lru (sm, s, thread_index);

  return s;
}

static inline uword
nat44_ed_out2in_fast_path_node_fn_inline (vlib_main_t * vm,
                                          vlib_node_runtime_t * node,
                                          vlib_frame_t * frame,
                                          int is_multi_worker)
{
  u32 n_left_from, *from;
  snat_main_t *sm = &snat_main;
  f64 now = vlib_time_now (vm);
  u32 thread_index = vm->thread_index;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors;

  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;
  u16 nexts[VLIB_FRAME_SIZE], *next = nexts;
  vlib_get_buffers (vm, from, b, n_left_from);

  while (n_left_from > 0)
    {
      vlib_buffer_t *b0;
      u32 sw_if_index0, rx_fib_index0, proto0, old_addr0, new_addr0;
      u16 old_port0, new_port0;
      ip4_header_t *ip0;
      udp_header_t *udp0;
      tcp_header_t *tcp0;
      snat_session_t *s0 = 0;
      clib_bihash_kv_16_8_t kv0, value0;
      ip_csum_t sum0;

      b0 = *b;
      b++;

      /* Prefetch next iteration. */
      if (PREDICT_TRUE (n_left_from >= 2))
        {
          vlib_buffer_t *p2;

          p2 = *b;

          vlib_prefetch_buffer_header (p2, LOAD);

          CLIB_PREFETCH (p2->data, CLIB_CACHE_LINE_BYTES, LOAD);
        }

      next[0] = vnet_buffer2 (b0)->nat.arc_next;

      vnet_buffer (b0)->snat.flags = 0;
      ip0 = vlib_buffer_get_current (b0);

      sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
      rx_fib_index0 =
        fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP4, sw_if_index0);

      if (PREDICT_FALSE (ip0->ttl == 1))
        {
          vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
          icmp4_error_set_vnet_buffer (b0, ICMP4_time_exceeded,
                                       ICMP4_time_exceeded_ttl_exceeded_in_transit,
                                       0);
          next[0] = NAT_NEXT_ICMP_ERROR;
          goto trace0;
        }

      udp0 = ip4_next_header (ip0);
      tcp0 = (tcp_header_t *) udp0;
      proto0 = ip_proto_to_nat_proto (ip0->protocol);

      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_OTHER))
        {
          next[0] = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
          goto trace0;
        }

      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
        {
          next[0] = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
          goto trace0;
        }

      init_ed_k (&kv0, ip0->dst_address,
                 vnet_buffer (b0)->ip.reass.l4_dst_port, ip0->src_address,
                 vnet_buffer (b0)->ip.reass.l4_src_port, rx_fib_index0,
                 ip0->protocol);

      /* there is a stashed index in vnet_buffer2 from handoff node,
       * see if we can use it */
      if (is_multi_worker
          &&
          PREDICT_TRUE (!pool_is_free_index
                        (tsm->sessions,
                         vnet_buffer2 (b0)->nat.ed_out2in_nat_session_index)))
        {
          s0 = pool_elt_at_index (tsm->sessions,
                                  vnet_buffer2 (b0)->
                                  nat.ed_out2in_nat_session_index);
          if (PREDICT_TRUE
              (s0->out2in.addr.as_u32 == ip0->dst_address.as_u32
               && s0->out2in.port == vnet_buffer (b0)->ip.reass.l4_dst_port
               && s0->nat_proto == ip_proto_to_nat_proto (ip0->protocol)
               && s0->out2in.fib_index == rx_fib_index0
               && s0->ext_host_addr.as_u32 == ip0->src_address.as_u32
               && s0->ext_host_port ==
               vnet_buffer (b0)->ip.reass.l4_src_port))
            {
              /* yes, this is the droid we're looking for */
              goto skip_lookup;
            }
        }

      // lookup for session
      if (clib_bihash_search_16_8 (&sm->out2in_ed, &kv0, &value0))
        {
          // session does not exist go slow path
          next[0] = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
          goto trace0;
        }
      ASSERT (thread_index == ed_value_get_thread_index (&value0));
      s0 =
        pool_elt_at_index (tsm->sessions,
                           ed_value_get_session_index (&value0));

    skip_lookup:

      if (PREDICT_FALSE (per_vrf_sessions_is_expired (s0, thread_index)))
        {
          // session is closed, go slow path
          nat_free_session_data (sm, s0, thread_index, 0);
          nat_ed_session_delete (sm, s0, thread_index, 1);
          next[0] = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
          goto trace0;
        }

      if (s0->tcp_closed_timestamp)
        {
          if (now >= s0->tcp_closed_timestamp)
            {
              // session is closed, go slow path, freed in slow path
              next[0] = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
            }
          else
            {
              // session in transitory timeout, drop
              b0->error = node->errors[NAT_OUT2IN_ED_ERROR_TCP_CLOSED];
              next[0] = NAT_NEXT_DROP;
            }
          goto trace0;
        }

      // drop if session expired
      u64 sess_timeout_time;
      sess_timeout_time =
        s0->last_heard + (f64) nat44_session_get_timeout (sm, s0);
      if (now >= sess_timeout_time)
        {
          // session is closed, go slow path
          nat_free_session_data (sm, s0, thread_index, 0);
          nat_ed_session_delete (sm, s0, thread_index, 1);
          next[0] = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
          goto trace0;
        }

      old_addr0 = ip0->dst_address.as_u32;
      new_addr0 = ip0->dst_address.as_u32 = s0->in2out.addr.as_u32;
      vnet_buffer (b0)->sw_if_index[VLIB_TX] = s0->in2out.fib_index;

      sum0 = ip0->checksum;
      sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                             dst_address);
      if (PREDICT_FALSE (is_twice_nat_session (s0)))
        sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                               s0->ext_host_nat_addr.as_u32, ip4_header_t,
                               src_address);
      ip0->checksum = ip_csum_fold (sum0);

      old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;

      if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
        {
          if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
            {
              new_port0 = udp0->dst_port = s0->in2out.port;
              sum0 = tcp0->checksum;
              sum0 =
                ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                dst_address);
              sum0 =
                ip_csum_update (sum0, old_port0, new_port0, ip4_header_t,
                                length);
              if (is_twice_nat_session (s0))
                {
                  sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                         s0->ext_host_nat_addr.as_u32,
                                         ip4_header_t, dst_address);
                  sum0 =
                    ip_csum_update (sum0,
                                    vnet_buffer (b0)->ip.reass.l4_src_port,
                                    s0->ext_host_nat_port, ip4_header_t,
                                    length);
                  tcp0->src_port = s0->ext_host_nat_port;
                  ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                }
              tcp0->checksum = ip_csum_fold (sum0);
            }
          vlib_increment_simple_counter (&sm->counters.fastpath.out2in_ed.tcp,
                                         thread_index, sw_if_index0, 1);
          nat44_set_tcp_session_state_o2i (sm, now, s0,
                                           vnet_buffer (b0)->ip.
                                           reass.icmp_type_or_tcp_flags,
                                           vnet_buffer (b0)->ip.
                                           reass.tcp_ack_number,
                                           vnet_buffer (b0)->ip.
                                           reass.tcp_seq_number,
                                           thread_index);
        }
      else if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment
               && udp0->checksum)
        {
          new_port0 = udp0->dst_port = s0->in2out.port;
          sum0 = udp0->checksum;
          sum0 =
            ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                            dst_address);
          sum0 =
            ip_csum_update (sum0, old_port0, new_port0, ip4_header_t, length);
          if (PREDICT_FALSE (is_twice_nat_session (s0)))
            {
              sum0 =
                ip_csum_update (sum0, ip0->src_address.as_u32,
                                s0->ext_host_nat_addr.as_u32, ip4_header_t,
                                dst_address);
              sum0 =
                ip_csum_update (sum0, vnet_buffer (b0)->ip.reass.l4_src_port,
                                s0->ext_host_nat_port, ip4_header_t, length);
              udp0->src_port = s0->ext_host_nat_port;
              ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
            }
          udp0->checksum = ip_csum_fold (sum0);
          vlib_increment_simple_counter (&sm->counters.fastpath.out2in_ed.udp,
                                         thread_index, sw_if_index0, 1);
        }
      else
        {
          if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
            {
              new_port0 = udp0->dst_port = s0->in2out.port;
              if (PREDICT_FALSE (is_twice_nat_session (s0)))
                {
                  udp0->src_port = s0->ext_host_nat_port;
                  ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                }
            }
          vlib_increment_simple_counter (&sm->counters.fastpath.out2in_ed.udp,
                                         thread_index, sw_if_index0, 1);
        }

      /* Accounting */
      nat44_session_update_counters (s0, now,
                                     vlib_buffer_length_in_chain (vm, b0),
                                     thread_index);
      /* Per-user LRU list maintenance */
      nat44_session_update_lru (sm, s0, thread_index);

    trace0:
      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                         && (b0->flags & VLIB_BUFFER_IS_TRACED)))
        {
          nat44_ed_out2in_trace_t *t =
            vlib_add_trace (vm, node, b0, sizeof (*t));
          t->sw_if_index = sw_if_index0;
          t->next_index = next[0];
          t->is_slow_path = 0;

          if (s0)
            t->session_index = s0 - tsm->sessions;
          else
            t->session_index = ~0;
        }

      if (next[0] == NAT_NEXT_DROP)
        {
          vlib_increment_simple_counter (&sm->counters.fastpath.
                                         out2in_ed.drops, thread_index,
                                         sw_if_index0, 1);
        }

      n_left_from--;
      next++;
    }

  vlib_buffer_enqueue_to_next (vm, node, from, (u16 *) nexts,
                               frame->n_vectors);
  return frame->n_vectors;
}

static inline uword
nat44_ed_out2in_slow_path_node_fn_inline (vlib_main_t * vm,
                                          vlib_node_runtime_t * node,
                                          vlib_frame_t * frame)
{
  u32 n_left_from, *from;
  snat_main_t *sm = &snat_main;
  f64 now = vlib_time_now (vm);
  u32 thread_index = vm->thread_index;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  snat_static_mapping_t *m;

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors;

  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;
  u16 nexts[VLIB_FRAME_SIZE], *next = nexts;
  vlib_get_buffers (vm, from, b, n_left_from);

  while (n_left_from > 0)
    {
      vlib_buffer_t *b0;
      u32 sw_if_index0, rx_fib_index0, proto0, old_addr0, new_addr0;
      u16 old_port0, new_port0;
      ip4_header_t *ip0;
      udp_header_t *udp0;
      tcp_header_t *tcp0;
      icmp46_header_t *icmp0;
      snat_session_t *s0 = 0;
      clib_bihash_kv_16_8_t kv0, value0;
      ip_csum_t sum0;
      lb_nat_type_t lb_nat0;
      twice_nat_type_t twice_nat0;
      u8 identity_nat0;
      ip4_address_t sm_addr;
      u16 sm_port;
      u32 sm_fib_index;

      b0 = *b;
      next[0] = vnet_buffer2 (b0)->nat.arc_next;

      vnet_buffer (b0)->snat.flags = 0;
      ip0 = vlib_buffer_get_current (b0);

      sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
      rx_fib_index0 =
        fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP4, sw_if_index0);

      if (PREDICT_FALSE (ip0->ttl == 1))
        {
          vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
          icmp4_error_set_vnet_buffer (b0, ICMP4_time_exceeded,
                                       ICMP4_time_exceeded_ttl_exceeded_in_transit,
                                       0);
          next[0] = NAT_NEXT_ICMP_ERROR;
          goto trace0;
        }

      udp0 = ip4_next_header (ip0);
      tcp0 = (tcp_header_t *) udp0;
      icmp0 = (icmp46_header_t *) udp0;
      proto0 = ip_proto_to_nat_proto (ip0->protocol);

      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_OTHER))
        {
          s0 =
            nat44_ed_out2in_unknown_proto (sm, b0, ip0, rx_fib_index0,
                                           thread_index, now, vm, node);
          if (!sm->forwarding_enabled)
            {
              if (!s0)
                next[0] = NAT_NEXT_DROP;
            }
          vlib_increment_simple_counter (&sm->counters.slowpath.
                                         out2in_ed.other, thread_index,
                                         sw_if_index0, 1);
          goto trace0;
        }

      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
        {
          next[0] = icmp_out2in_ed_slow_path
            (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
             next[0], now, thread_index, &s0);
          vlib_increment_simple_counter (&sm->counters.slowpath.
                                         out2in_ed.icmp, thread_index,
                                         sw_if_index0, 1);
          goto trace0;
        }

      init_ed_k (&kv0, ip0->dst_address,
                 vnet_buffer (b0)->ip.reass.l4_dst_port, ip0->src_address,
                 vnet_buffer (b0)->ip.reass.l4_src_port, rx_fib_index0,
                 ip0->protocol);

      s0 = NULL;
      if (!clib_bihash_search_16_8 (&sm->out2in_ed, &kv0, &value0))
        {
          ASSERT (thread_index == ed_value_get_thread_index (&value0));
          s0 =
            pool_elt_at_index (tsm->sessions,
                               ed_value_get_session_index (&value0));

          if (s0->tcp_closed_timestamp && now >= s0->tcp_closed_timestamp)
            {
              nat_free_session_data (sm, s0, thread_index, 0);
              nat_ed_session_delete (sm, s0, thread_index, 1);
              s0 = NULL;
            }
        }

      if (!s0)
        {
          /* Try to match static mapping by external address and port,
             destination address and port in packet */

          if (snat_static_mapping_match
              (sm, ip0->dst_address,
               vnet_buffer (b0)->ip.reass.l4_dst_port, rx_fib_index0,
               proto0, &sm_addr, &sm_port, &sm_fib_index, 1, 0,
               &twice_nat0, &lb_nat0, &ip0->src_address, &identity_nat0, &m))
            {
              /*
               * Send DHCP packets to the ipv4 stack, or we won't
               * be able to use dhcp client on the outside interface
               */
              if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_UDP
                                 && (vnet_buffer (b0)->ip.reass.l4_dst_port ==
                                     clib_host_to_net_u16
                                     (UDP_DST_PORT_dhcp_to_client))))
                {
                  goto trace0;
                }

              if (!sm->forwarding_enabled)
                {
                  b0->error =
                    node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
                  next[0] = NAT_NEXT_DROP;
                }
              else
                {
                  if (next_src_nat
                      (sm, ip0, vnet_buffer (b0)->ip.reass.l4_src_port,
                       vnet_buffer (b0)->ip.reass.l4_dst_port,
                       thread_index, rx_fib_index0))
                    {
                      next[0] = NAT_NEXT_IN2OUT_ED_FAST_PATH;
                    }
                  else
                    {
                      if ((sm->num_workers > 1)
                          && create_bypass_for_fwd_worker (sm, b0, ip0,
                                                           rx_fib_index0,
                                                           thread_index))
                        {
                          next[0] = NAT_NEXT_OUT2IN_ED_HANDOFF;
                        }
                      else
                        {
                          create_bypass_for_fwd (sm, b0, ip0, rx_fib_index0,
                                                 thread_index);
                        }
                    }
                }
              goto trace0;
            }

          if (PREDICT_FALSE (identity_nat0))
            goto trace0;

          if ((proto0 == NAT_PROTOCOL_TCP)
              && !tcp_flags_is_init (vnet_buffer (b0)->ip.
                                     reass.icmp_type_or_tcp_flags))
            {
              b0->error = node->errors[NAT_OUT2IN_ED_ERROR_NON_SYN];
              next[0] = NAT_NEXT_DROP;
              goto trace0;
            }

          /* Create session initiated by host from external network */
          s0 = create_session_for_static_mapping_ed (sm, b0,
                                                     sm_addr, sm_port,
                                                     sm_fib_index,
                                                     ip0->dst_address,
                                                     vnet_buffer (b0)->
                                                     ip.reass.l4_dst_port,
                                                     rx_fib_index0, proto0,
                                                     node, rx_fib_index0,
                                                     thread_index, twice_nat0,
                                                     lb_nat0, now, m);
          if (!s0)
            {
              next[0] = NAT_NEXT_DROP;
              goto trace0;
            }
        }

      old_addr0 = ip0->dst_address.as_u32;
      new_addr0 = ip0->dst_address.as_u32 = s0->in2out.addr.as_u32;
      vnet_buffer (b0)->sw_if_index[VLIB_TX] = s0->in2out.fib_index;

      sum0 = ip0->checksum;
      sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                             dst_address);
      if (PREDICT_FALSE (is_twice_nat_session (s0)))
        sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                               s0->ext_host_nat_addr.as_u32, ip4_header_t,
                               src_address);
      ip0->checksum = ip_csum_fold (sum0);

      old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;

      if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
        {
          if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
            {
              new_port0 = udp0->dst_port = s0->in2out.port;
              sum0 = tcp0->checksum;
              sum0 =
                ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                dst_address);
              sum0 =
                ip_csum_update (sum0, old_port0, new_port0, ip4_header_t,
                                length);
              if (is_twice_nat_session (s0))
                {
                  sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                         s0->ext_host_nat_addr.as_u32,
                                         ip4_header_t, dst_address);
                  sum0 =
                    ip_csum_update (sum0,
                                    vnet_buffer (b0)->ip.reass.l4_src_port,
                                    s0->ext_host_nat_port, ip4_header_t,
                                    length);
                  tcp0->src_port = s0->ext_host_nat_port;
                  ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                }
              tcp0->checksum = ip_csum_fold (sum0);
            }
          vlib_increment_simple_counter (&sm->counters.slowpath.out2in_ed.tcp,
                                         thread_index, sw_if_index0, 1);
          nat44_set_tcp_session_state_o2i (sm, now, s0,
                                           vnet_buffer (b0)->ip.
                                           reass.icmp_type_or_tcp_flags,
                                           vnet_buffer (b0)->ip.
                                           reass.tcp_ack_number,
                                           vnet_buffer (b0)->ip.
                                           reass.tcp_seq_number,
                                           thread_index);
        }
      else if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment
               && udp0->checksum)
        {
          new_port0 = udp0->dst_port = s0->in2out.port;
          sum0 = udp0->checksum;
          sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                 dst_address);
          sum0 = ip_csum_update (sum0, old_port0, new_port0, ip4_header_t,
                                 length);
          if (PREDICT_FALSE (is_twice_nat_session (s0)))
            {
              sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                     s0->ext_host_nat_addr.as_u32,
                                     ip4_header_t, dst_address);
              sum0 =
                ip_csum_update (sum0,
                                vnet_buffer (b0)->ip.reass.l4_src_port,
                                s0->ext_host_nat_port, ip4_header_t, length);
              udp0->src_port = s0->ext_host_nat_port;
              ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
            }
          udp0->checksum = ip_csum_fold (sum0);
          vlib_increment_simple_counter (&sm->counters.slowpath.out2in_ed.udp,
                                         thread_index, sw_if_index0, 1);
        }
      else
        {
          if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
            {
              new_port0 = udp0->dst_port = s0->in2out.port;
              if (PREDICT_FALSE (is_twice_nat_session (s0)))
                {
                  udp0->src_port = s0->ext_host_nat_port;
                  ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                }
            }
          vlib_increment_simple_counter (&sm->counters.slowpath.out2in_ed.udp,
                                         thread_index, sw_if_index0, 1);
        }

      /* Accounting */
      nat44_session_update_counters (s0, now,
                                     vlib_buffer_length_in_chain (vm, b0),
                                     thread_index);
      /* Per-user LRU list maintenance */
      nat44_session_update_lru (sm, s0, thread_index);

    trace0:
      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                         && (b0->flags & VLIB_BUFFER_IS_TRACED)))
        {
          nat44_ed_out2in_trace_t *t =
            vlib_add_trace (vm, node, b0, sizeof (*t));
          t->sw_if_index = sw_if_index0;
          t->next_index = next[0];
          t->is_slow_path = 1;

          if (s0)
            t->session_index = s0 - tsm->sessions;
          else
            t->session_index = ~0;
        }

      if (next[0] == NAT_NEXT_DROP)
        {
          vlib_increment_simple_counter (&sm->counters.slowpath.
                                         out2in_ed.drops, thread_index,
                                         sw_if_index0, 1);
        }

      n_left_from--;
      next++;
      b++;
    }

  vlib_buffer_enqueue_to_next (vm, node, from, (u16 *) nexts,
                               frame->n_vectors);

  return frame->n_vectors;
}

static inline uword
nat_handoff_node_fn_inline (vlib_main_t * vm,
                            vlib_node_runtime_t * node,
                            vlib_frame_t * frame, u32 fq_index)
{
  u32 n_enq, n_left_from, *from;

  u16 thread_indices[VLIB_FRAME_SIZE], *ti = thread_indices;
  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors;

  vlib_get_buffers (vm, from, b, n_left_from);

  while (n_left_from >= 4)
    {
      if (PREDICT_TRUE (n_left_from >= 8))
        {
          vlib_prefetch_buffer_header (b[4], LOAD);
          vlib_prefetch_buffer_header (b[5], LOAD);
          vlib_prefetch_buffer_header (b[6], LOAD);
          vlib_prefetch_buffer_header (b[7], LOAD);
          CLIB_PREFETCH (&b[4]->data, CLIB_CACHE_LINE_BYTES, LOAD);
          CLIB_PREFETCH (&b[5]->data, CLIB_CACHE_LINE_BYTES, LOAD);
          CLIB_PREFETCH (&b[6]->data, CLIB_CACHE_LINE_BYTES, LOAD);
          CLIB_PREFETCH (&b[7]->data, CLIB_CACHE_LINE_BYTES, LOAD);
        }

      ti[0] = vnet_buffer2 (b[0])->nat.thread_next;
      ti[1] = vnet_buffer2 (b[1])->nat.thread_next;
      ti[2] = vnet_buffer2 (b[2])->nat.thread_next;
      ti[3] = vnet_buffer2 (b[3])->nat.thread_next;

      b += 4;
      ti += 4;
      n_left_from -= 4;
    }

  while (n_left_from > 0)
    {
      ti[0] = vnet_buffer2 (b[0])->nat.thread_next;

      b += 1;
      ti += 1;
      n_left_from -= 1;
    }

  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)))
    {
      u32 i;
      b = bufs;
      ti = thread_indices;

      for (i = 0; i < frame->n_vectors; i++)
        {
          if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
            {
              nat44_ed_out2in_handoff_trace_t *t =
                vlib_add_trace (vm, node, b[0], sizeof (*t));
              t->thread_next = ti[0];
              b += 1;
              ti += 1;
            }
          else
            break;
        }
    }

  n_enq = vlib_buffer_enqueue_to_thread (vm, fq_index, from, thread_indices,
                                         frame->n_vectors, 1);

  if (n_enq < frame->n_vectors)
    {
      vlib_node_increment_counter (vm, node->node_index,
                                   NAT44_HANDOFF_ERROR_CONGESTION_DROP,
                                   frame->n_vectors - n_enq);
    }

  return frame->n_vectors;
}

VLIB_NODE_FN (nat44_ed_out2in_node) (vlib_main_t * vm,
                                     vlib_node_runtime_t * node,
                                     vlib_frame_t * frame)
{
  if (snat_main.num_workers > 1)
    {
      return nat44_ed_out2in_fast_path_node_fn_inline (vm, node, frame, 1);
    }
  else
    {
      return nat44_ed_out2in_fast_path_node_fn_inline (vm, node, frame, 0);
    }
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (nat44_ed_out2in_node) = {
  .name = "nat44-ed-out2in",
  .vector_size = sizeof (u32),
  .sibling_of = "nat-default",
  .format_trace = format_nat44_ed_out2in_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = ARRAY_LEN(nat_out2in_ed_error_strings),
  .error_strings = nat_out2in_ed_error_strings,
  .runtime_data_bytes = sizeof (snat_runtime_t),
};
/* *INDENT-ON* */

VLIB_NODE_FN (nat44_ed_out2in_slowpath_node) (vlib_main_t * vm,
                                              vlib_node_runtime_t * node,
                                              vlib_frame_t * frame)
{
  return nat44_ed_out2in_slow_path_node_fn_inline (vm, node, frame);
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (nat44_ed_out2in_slowpath_node) = {
  .name = "nat44-ed-out2in-slowpath",
  .vector_size = sizeof (u32),
  .sibling_of = "nat-default",
  .format_trace = format_nat44_ed_out2in_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = ARRAY_LEN(nat_out2in_ed_error_strings),
  .error_strings = nat_out2in_ed_error_strings,
  .runtime_data_bytes = sizeof (snat_runtime_t),
};
/* *INDENT-ON* */

static u8 *
format_nat44_ed_out2in_handoff_trace (u8 * s, va_list * args)
{
  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
  nat44_ed_out2in_handoff_trace_t *t =
    va_arg (*args, nat44_ed_out2in_handoff_trace_t *);
  return format (s, "out2in ed handoff thread_next index %d", t->thread_next);
}

VLIB_NODE_FN (nat44_ed_out2in_handoff_node) (vlib_main_t * vm,
                                             vlib_node_runtime_t * node,
                                             vlib_frame_t * frame)
{
  return nat_handoff_node_fn_inline (vm, node, frame,
                                     snat_main.ed_out2in_node_index);
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (nat44_ed_out2in_handoff_node) = {
  .name = "nat44-ed-out2in-handoff",
  .vector_size = sizeof (u32),
  .sibling_of = "nat-default",
  .format_trace = format_nat44_ed_out2in_handoff_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = 0,
};
/* *INDENT-ON* */

static u8 *
format_nat_pre_trace (u8 * s, va_list * args)
{
  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
  nat_pre_trace_t *t = va_arg (*args, nat_pre_trace_t *);
  return format (s, "out2in next_index %d arc_next_index %d", t->next_index,
                 t->arc_next_index);
}

VLIB_NODE_FN (nat_pre_out2in_node) (vlib_main_t * vm,
                                    vlib_node_runtime_t * node,
                                    vlib_frame_t * frame)
{
  return nat_pre_node_fn_inline (vm, node, frame,
                                 NAT_NEXT_OUT2IN_ED_FAST_PATH);
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (nat_pre_out2in_node) = {
  .name = "nat-pre-out2in",
  .vector_size = sizeof (u32),
  .sibling_of = "nat-default",
  .format_trace = format_nat_pre_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = 0,
 };
/* *INDENT-ON* */

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